Researcher Profile and Settings

Master

Affiliation (Master)

• Institute of Low Temperature Science　Frontier Ice and Snow Science

Affiliation (Master)

• Institute of Low Temperature Science　Frontier Ice and Snow Science

researchmap

Profile and Settings

Affiliation

• Hokkaido University, Graduate School of Science, Department of Cosmosciences

Profile and Settings

• Name (Japanese)

  Kimura

• Name (Kana)

  Yuki

• Name

  200901020947437592

Alternate Names

http://www.lowtem.hokudai.ac.jp/astro/ykimura/index.html
http://db.tohoku.ac.jp/whois/detail/0704c108d125122d56649ba738c73896.html

Affiliation

• Hokkaido University, Graduate School of Science, Department of Cosmosciences

Achievement

Research Interests

• 宇宙ダスト   結晶成長   結晶   透過型電子顕微鏡   多環芳香族炭化水素   天体観測   天文学   表面   その場観察   赤外スペクトル   惑星科学   均質核生成   ナノ領域科学   干渉法   核形成   電子顕微鏡   実験   宇宙塵   ナノ粒子   microscopy   experiments   cosmic dust   Nanoparticles   

Research Areas

• Natural sciences / Magnetism, superconductivity, and strongly correlated systems
• Natural sciences / Space and planetary science
• Natural sciences / Astronomy
• Natural sciences / Solid earth science
• Nanotechnology/Materials / Nanostructure physics
• Nanotechnology/Materials / Nanostructure chemistry

Research Experience

• 2023/03 - Today Hokkaido University Institute of Low Temperature Science Professor
• 2014/04 - 2023/02 Hokkaido University Institute of Low Temperature Science
• 2009/01 - 2014/03 Tohoku University
• 2008/04 - 2008/12 北海道大学 研究員
• 2006/05 - 2008/03 Ritsumeikan University
• 2004/04 - 2006/04 NASA 学術振興会海外特別研究員
• 2004 - 2006 NASA, Goddard Space Flight Center
• 2002/04 - 2004/03 Ritsumeikan University
• 2001/04 - 2002/03 Ritsumeikan University

Education

•        - 2002  Ritsumeikan University  Graduate School of Science and Engineering
•        - 2001  Ritsumeikan University  Graduate School of Science and Engineering
•        - 1999  Ritsumeikan University

Committee Memberships

• 2011 -2012   日本物理学会領域９   運営委員   日本物理学会領域９
• 2007 -2009   Reviewer of the award in the Japanese Society for Planetary Sciences   幹事   Reviewer of the award in the Japanese Society for Planetary Sciences

Awards

• 2024/04 令和六年度科学技術分野の文部科学大臣表彰 科学技術賞（研究部門）
  
• 2023/03 日本金属学会 第73回金属組織写真賞 奨励賞
  
• 2022/07 日本セラミックス協会 第47回学術写真賞 最優秀賞
  
• 2021/03 公益財団法人 風戸研究奨励会 第14回（令和2年度）風戸賞
  
• 2019/10 The Japanese Association for Crystal Growth 36th Best Paper Award
   Elucidation of formation processes of cosmic dust particles based on homogeneous nucleation experiments 

  受賞者: KIMURA Yuki
• 2019/05 Japan Geoscience Union The 3rd Nishida Prize
   

  受賞者: KIMURA Yuki
• 2019/02 Hokkaido University President's Award for Outstanding Research
   

  受賞者: KIMURA Yuki
• 2018/02 日本学術振興会 第14回（平成29年度）日本学術振興会賞
   

  受賞者: 木村 勇気
• 2017/01 宇宙航空研究開発機構 宇宙科学研究所 第3回宇宙科学研究所賞
   

  受賞者: 木村 勇気
• 2017/01 北海道大学 北海道大学研究総長賞
   

  受賞者: 木村 勇気
• 2016/10 日本マイクログラビティ応用学会 第12回 (2016年度) 日本マイクログラビティ応用学会研究奨励賞
   

  受賞者: 木村 勇気
• 2014/03 日本セラミックス協会 第３９回学術写真賞 最優秀賞
   隕石内部のSEM, Holography 観察からわかる太陽系形成期の「水」の痕跡 

  受賞者: 佐藤岳志;山本和生;木村勇気
• 2013 "Schieber Prize", the International Organization for Crystal Growth
  
• 2012 日本物理学会領域9若手奨励賞
  
• 2011 Best Poster Award at the International Conference on Materials for Advanced Technologies, 2011.
  
• 2010 平成22年度科学技術分野の文部科学大臣表彰 若手科学者賞
  
• 2009 International School of Crystallization 2009 Accommodation Grant
  
• 2008 日本結晶成長学会 第六回奨励賞
  
• 2007 2006年度 日本惑星科学会 最優秀研究者賞
  
• 2002 第32回 結晶成長国内会議 講演奨励賞
  

Published Papers

• Micrometer-Scale Graphene-Based Liquid Cells of Highly Concentrated Salt Solutions for In Situ Liquid-Cell Transmission Electron Microscopy.

  Yuga Yashima, Tomoya Yamazaki, Yuki Kimura

  ACS omega 9 (38) 39914 - 39924 2024/09/24 

  In situ liquid-cell transmission microscopy has attracted much attention as a method for the direct observations of the dynamics of soft matter. A graphene liquid cell (GLC) has previously been investigated as an alternative to a conventional SiN x liquid cell. Although GLCs are capable of scavenging radicals and providing high spatial resolutions, their production is fundamentally stochastic, and a significant compositional change in liquids encapsulated in GLCs has recently been pointed out. We found that graphene-based liquid cells were formed in nano- to micrometer sizes with high reproducibility when the concentration of the encapsulated aqueous salt solution was high. In contrast, when we revisited conventional fabrication methods, water-encapsulated GLC was formed with low yield, and any electron diffraction spots from ice were not confirmed by a cooling experiment. The reason for this was the presence of intrinsic defects in the graphene, the presence of which we confirmed by the etch-pit method. The shrinkage of a water-encapsulated cell and a decrease in the bubble area in an aqueous (NH4)2SO4 solution cell suggested that volatile water molecules and gas molecules can leak from the cells during the fabrication and observation processes. Further revision of the conditions for the formation of liquid cells and a reduction in the number of intrinsic graphene defects are expected to lead to the provision of graphene-based liquid cells capable of encapsulating dilute aqueous solutions or pure water.
• Dependence of Homoimmiscible Water Dynamics on Overpressure at the Interface between Water and the Basal Plane of Single-Crystal Ice I_h

  Hiromasa Niinomi, Hiroki Nada, Tomoya Yamazaki, Tetsuya Hama, Akira Kouchi, Tomoya Oshikiri, Masaru Nakagawa, Yuki Kimura

  The Journal of Physical Chemistry C 1932-7447 2024/09/09
• Enantioselective three-dimensional high-performance liquid chromatographic determination of amino acids in the Hayabusa2 returned samples from the asteroid Ryugu

  Aogu Furusho, Chiharu Ishii, Takeyuki Akita, Mai Oyaide, Masashi Mita, Hiroshi Naraoka, Yoshinori Takano, Jason P. Dworkin, Yasuhiro Oba, Toshiki Koga, Kazuhiko Fukushima, Dan Aoki, Minako Hashiguchi, Hajime Mita, Yoshito Chikaraishi, Naohiko Ohkouchi, Nanako O. Ogawa, Saburo Sakai, Daniel P. Glavin, Jamie E. Elsila, Eric T. Parker, José C. Aponte, Hannah L. McLain, Francois-Regis Orthous-Daunay, Véronique Vuitton, Roland Thissen, Cédric Wolters, Philippe Schmitt-Kopplin, Alexander Ruf, Junko Isa, Norbert Hertkorn, John M. Eiler, Toshihiro Yoshimura, Haruna Sugahara, Heather V. Graham, Yoshihiro Furukawa, Daisuke Araoka, Satoru Tanaka, Takaaki Yoshikawa, Fumie Kabashima, Kazunori Sasaki, Hajime Sato, Tomoya Yamazaki, Morihiko Onose, Mayu Morita, Yuki Kimura, Kuniyuki Kano, Junken Aoki, Kosuke Fujishima, Shin-ichiro Nomura, Shogo Tachibana

  Journal of Chromatography Open 2772-3917 2024/05
• Nonmagnetic framboid and associated iron nanoparticles with a space-weathered feature from asteroid Ryugu

  Yuki Kimura, Takeharu Kato, Satoshi Anada, Ryuji Yoshida, Kazuo Yamamoto, Toshiaki Tanigaki, Tetsuya Akashi, Hiroto Kasai, Kosuke Kurosawa, Tomoki Nakamura, Takaaki Noguchi, Masahiko Sato, Toru Matsumoto, Tomoyo Morita, Mizuha Kikuiri, Kana Amano, Eiichi Kagawa, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Hisayoshi Yurimoto, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Sei-ichiro Watanabe, Yuichi Tsuda, Shogo Tachibana

  Nature Communications 15 (1) 2024/04/29 

  Abstract Extraterrestrial minerals on the surface of airless Solar System bodies undergo gradual alteration processes known as space weathering over long periods of time. The signatures of space weathering help us understand the phenomena occurring in the Solar System. However, meteorites rarely retain the signatures, making it impossible to study the space weathering processes precisely. Here, we examine samples retrieved from the asteroid Ryugu by the Hayabusa2 spacecraft and discover the presence of nonmagnetic framboids through electron holography measurements that can visualize magnetic flux. Magnetite particles, which normally provide a record of the nebular magnetic field, have lost their magnetic properties by reduction via a high-velocity (>5 km s^–1) impact of a micrometeoroid with a diameter ranging from 2 to 20 μm after destruction of the parent body of Ryugu. Around these particles, thousands of metallic-iron nanoparticles with a vortex magnetic domain structure, which could have recorded a magnetic field in the impact event, are found. Through measuring the remanent magnetization of the iron nanoparticles, future studies are expected to elucidate the nature of the nebular/interplanetary magnetic fields after the termination of aqueous alteration in an asteroid.
• Diverse features of dust particles and their aggregates inferred from experimental nanoparticles

  Yuki Nakano, Yuki Kimura, Akihiko Hashimoto

  Monthly Notices of the Royal Astronomical Society: Letters 2024/03/29
• Machine Learning Refinement of In Situ Images Acquired by Low Electron Dose LC-TEM.

  Hiroyasu Katsuno, Yuki Kimura, Tomoya Yamazaki, Ichigaku Takigawa

  Microscopy and microanalysis : the official journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada 2024/01/29 

  We have studied a machine learning (ML) technique for refining images acquired during in situ observation using liquid-cell transmission electron microscopy. Our model is constructed using a U-Net architecture and a ResNet encoder. For training our ML model, we prepared an original image dataset that contained pairs of images of samples acquired with and without a solution present. The former images were used as noisy images, and the latter images were used as corresponding ground truth images. The number of pairs of image sets was 1,204, and the image sets included images acquired at several different magnifications and electron doses. The trained model converted a noisy image into a clear image. The time necessary for the conversion was on the order of 10 ms, and we applied the model to in situ observations using the software Gatan DigitalMicrograph (DM). Even if a nanoparticle was not visible in a view window in the DM software because of the low electron dose, it was visible in a successive refined image generated by our ML model.
• Chiral Spinodal-like Ordering of Homoimmiscible Water at Interface between Water and Chiral Ice III

  Hiromasa Niinomi, Tomoya Yamazaki, Hiroki Nada, Tetsuya Hama, Akira Kouchi, Tomoya Oshikiri, Masaru Nakagawa, Yuki Kimura

  The Journal of Physical Chemistry Letters 659 - 664 1948-7185 2024/01/11
• Polycyclic aromatic hydrocarbons in samples of Ryugu formed in the interstellar medium

  Sarah S. Zeichner, José C. Aponte, Surjyendu Bhattacharjee, Guannan Dong, Amy E. Hofmann, Jason P. Dworkin, Daniel P. Glavin, Jamie E. Elsila, Heather V. Graham, Hiroshi Naraoka, Yoshinori Takano, Shogo Tachibana, Allison T. Karp, Kliti Grice, Alex I. Holman, Katherine H. Freeman, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei-ichiro Watanabe, Yuichi Tsuda, Kenji Hamase, Kazuhiko Fukushima, Dan Aoki, Minako Hashiguchi, Hajime Mita, Yoshito Chikaraishi, Naohiko Ohkouchi, Nanako O. Ogawa, Saburo Sakai, Eric T. Parker, Hannah L. McLain, Francois-Regis Orthous-Daunay, Véronique Vuitton, Cédric Wolters, Philippe Schmitt-Kopplin, Norbert Hertkorn, Roland Thissen, Alexander Ruf, Junko Isa, Yasuhiro Oba, Toshiki Koga, Toshihiro Yoshimura, Daisuke Araoka, Haruna Sugahara, Aogu Furusho, Yoshihiro Furukawa, Junken Aoki, Kuniyuki Kano, Shin-ichiro M. Nomura, Kazunori Sasaki, Hajime Sato, Takaaki Yoshikawa, Satoru Tanaka, Mayu Morita, Morihiko Onose, Fumie Kabashima, Kosuke Fujishima, Tomoya Yamazaki, Yuki Kimura, John M. Eiler

  Science 382 (6677) 1411 - 1416 0036-8075 2023/12/22 

  Polycyclic aromatic hydrocarbons (PAHs) contain ≲20% of the carbon in the interstellar medium. They are potentially produced in circumstellar environments (at temperatures ≳1000 kelvin), by (~10 kelvin) interstellar clouds, or by processing of carbon-rich dust grains. We report isotopic properties of PAHs extracted from samples of the asteroid Ryugu and the meteorite Murchison. The doubly- ¹³ C substituted compositions (Δ2× ¹³ C values) of the PAHs naphthalene, fluoranthene, and pyrene are 9 to 51‰ higher than values expected for a stochastic distribution of isotopes. The Δ2× ¹³ C values are higher than expected if the PAHs formed in a circumstellar environment, but consistent with formation in the interstellar medium. By contrast, the PAHs phenanthrene and anthracene in Ryugu samples have Δ2× ¹³ C values consistent with formation by higher-temperature reactions.
• In Situ Transmission Electron Microscopy Study of Bubble Behavior Near the Surface of Ice Crystals by Using a Liquid Cell With a Peltier Cooling Holder.

  Tomoya Yamazaki, Yuga Yashima, Hiroyasu Katsuno, Hiroya Miyazaki, Takashi Gondo, Yuki Kimura

  Microscopy and microanalysis : the official journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada 29 (6) 1940 - 1949 2023/12/21 

  Liquid cell transmission electron microscopy (LC-TEM) is a unique technique that permits in situ observations of various phenomena in liquids with high spatial and temporal resolutions. One difficulty with this technique is the control of the environmental conditions in the observation area. Control of the temperature ranging from room temperature to minus several tens of degrees Celsius, is desirable for controlling the supersaturation in various materials and for observing crystallization more easily. We have developed a cooling transmission electron microscopy specimen holder that uses Peltier devices, and we have combined it with a liquid cell to realize accurate temperature control in LC-TEM. We evaluated this system by using water as a specimen. Motionless bubbles, shown to be voids containing pressurized gas, formed in the specimen sometime after the temperature had reached -12°C. An electron diffraction pattern showed that the specimen turned into ice Ih after the formation of these bubbles, confirming that our system works properly and can induce crystallization. In addition, we analyzed the behavior of bubbles formed in the ice Ih, and we discussed the formation of these bubbles and their internal pressure.
• 機械学習によるデータ駆動型の液中透過型電子顕微鏡“その場”観察

  Yuki KIMURA, Hiroyasu KATSUNO, Shizuka HIRAKAWA, Tomoya YAMAZAKI

  Vacuum and Surface Science 66 (12) 700 - 705 2433-5835 2023/12/10
• Dissolution enables dolomite crystal growth near ambient conditions.

  Joonsoo Kim, Yuki Kimura, Brian Puchala, Tomoya Yamazaki, Udo Becker, Wenhao Sun

  Science (New York, N.Y.) 382 (6673) 915 - 920 2023/11/24 

  Crystals grow in supersaturated solutions. A mysterious counterexample is dolomite CaMg(CO3)2, a geologically abundant sedimentary mineral that does not readily grow at ambient conditions, not even under highly supersaturated solutions. Using atomistic simulations, we show that dolomite initially precipitates a cation-disordered surface, where high surface strains inhibit further crystal growth. However, mild undersaturation will preferentially dissolve these disordered regions, enabling increased order upon reprecipitation. Our simulations predict that frequent cycling of a solution between supersaturation and undersaturation can accelerate dolomite growth by up to seven orders of magnitude. We validated our theory with in situ liquid cell transmission electron microscopy, directly observing bulk dolomite growth after pulses of dissolution. This mechanism explains why modern dolomite is primarily found in natural environments with pH or salinity fluctuations. More generally, it reveals that the growth and ripening of defect-free crystals can be facilitated by deliberate periods of mild dissolution.
• In situ cryogenic transmission electron microscopy observation on the formation of hydrogen-ordered hexagonal ices and its astrophysical implications

  Tomoya Yamazaki, Akira Kouchi, Ken-ichiro Murata, Hiroyasu Katsuno, Hiroki Nada, Tetsuya Hama, Yuki Kimura

  Monthly Notices of the Royal Astronomical Society 0035-8711 2023/11/06 

  Abstract Water ices play a critical role in various astrophysical phenomena and store information about the thermal history of icy grains. To understand this history, clarifying the formation conditions in astrophysical environments is critical. In addition to taking the form of amorphous ices, ice can take four crystalline forms: hexagonal ice I (ice Ih), cubic ice I (ice Ic) and hydrogen-ordered hexagonal ice (ice XIh) and cubic ice (ice XIc). The aim of this article is to study the conditions for phase transitions among these different crystalline ices. We found through cryogenic transmission electron microscopy observations that some polymorphs of ice XIh were formed by simple annealing of ice Ih at 120–150 K without any dopant or irradiation. We also investigated the formation conditions of ice Ih by vapor deposition and heating of ice Ic in protoplanetary disks. The transition kinetics from ice Ih to ice XIh suggested that ice XIh exists between the transition temperature from ice Ic to ice Ih and 150 K. From these results, we constructed a water-vapor flux–temperature–time diagram that clarifies the amorphous, Ic, Ih, XIc and XIh ice phases. We found that, under the conditions encountered in most protostars, hydrogen-ordered ices XIh and XIc can exist just outside the snow line and below 125 K, respectively. The infrared libration modes should enable these phases to be distinguished observationally. Because some of these phases are chiral, their presence could fundamentally affect the evolution of other homochiral organic molecules that develop on their surface.
• Anisotropy in spinodal-like dynamics of unknown water at ice V–water interface

  Hiromasa Niinomi, Tomoya Yamazaki, Hiroki Nada, Tetsuya Hama, Akira Kouchi, Tomoya Oshikiri, Masaru Nakagawa, Yuki Kimura

  Scientific Reports 13 (1) 2045-2322 2023/10/11 

  Abstract Experimentally demonstrating the existence of waters with local structures unlike that of common water is critical for understanding both the origin of the mysterious properties of water and liquid polymorphism in single component liquids. At the interfaces between water and ices I_h, III, and VI grown/melted under pressure, we previously discovered low- and high-density unknown waters, that are immiscible with the surrounding water. Here, we show, by in-situ optical microscopy, that an unknown water appears at the ice V–water interface via spinodal-like dynamics. The dewetting dynamics of the unknown water indicate that its characteristic velocity is ~ 90 m/s. The time evolution of the characteristic length of the spinodal-like undulation suggests that the dynamics may be described by a common model for spinodal decomposition of an immiscible liquid mixture. Spinodal-like dewetting dynamics of the unknown water transiently showed anisotropy, implying the property of a liquid crystal.
• Chemical evolution of primordial salts and organic sulfur molecules in the asteroid 162173 Ryugu

  Toshihiro Yoshimura, Yoshinori Takano, Hiroshi Naraoka, Toshiki Koga, Daisuke Araoka, Nanako O. Ogawa, Philippe Schmitt-Kopplin, Norbert Hertkorn, Yasuhiro Oba, Jason P. Dworkin, Jose C. Aponte, Takaaki Yoshikawa, Satoru Tanaka, Naohiko Ohkouchi, Minako Hashiguchi, Hannah Mclain, Eric T. Parker, Saburo Sakai, Mihoko Yamaguchi, Takahiro Suzuki, Tetsuya Yokoyama, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei-ichiro Watanabe, Yuichi Tsuda, Shogo Tachibana, Kenji Hamase, Aogu Furusho, Kazuhiko Fukushima, Dan Aoki, Daniel P. Glavin, Hannah L. Mclain, Jamie E. Elsila, Heather V. Graham, John M. Eiler, Alexander Ruf, Francois-Regis Orthous-Daunay, Cedric Wolters, Junko Isa, Mayu Morita, Veronique Vuitton, Roland Thissen, Shin-ichiro M. Nomura, Haruna Sugahara, Hajime Mita, Yoshihiro Furukawa, Yoshito Chikaraishi, Morihiko Onose, Fumie Kabashima, Kosuke Fujishima, Hajime Sato, Kazunori Sasaki, Kuniyuki Kano, Junken Aoki, Tomoya Yamazaki, Yuki Kimura

  NATURE COMMUNICATIONS 14 (1) 2041-1723 2023/09 

  Samples from the carbonaceous asteroid (162173) Ryugu provide information on the chemical evolution of organic molecules in the early solar system. Here we show the element partitioning of the major component ions by sequential extractions of salts, carbonates, and phyllosilicate-bearing fractions to reveal primordial brine composition of the primitive asteroid. Sodium is the dominant electrolyte of the salt fraction extract. Anions and NH4+ are more abundant in the salt fraction than in the carbonate and phyllosilicate fractions, with molar concentrations in the order SO42- > Cl- > S2O32- > NO3- > NH4+. The salt fraction extracts contain anionic soluble sulfur-bearing species such as Sn-polythionic acids (n < 6), C-n-alkylsulfonates, alkylthiosulfonates, hydroxyalkylsulfonates, and hydroxyalkylthiosulfonates (n < 7). The sulfur-bearing soluble compounds may have driven the molecular evolution of prebiotic organic material transforming simple organic molecules into hydrophilic, amphiphilic, and refractory S allotropes.
• Visualization of nanoscale magnetic domain states in the asteroid Ryugu

  Yuki Kimura, Takeharu Kato, Toshiaki Tanigaki, Tetsuya Akashi, Hiroto Kasai, Satoshi Anada, Ryuji Yoshida, Kazuo Yamamoto, Tomoki Nakamura, Masahiko Sato, Kana Amano, Mizuha Kikuiri, Tomoyo Morita, Eiichi Kagawa, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Hisayoshi Yurimoto, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Sei-ichiro Watanabe, Yuichi Tsuda, Shogo Tachibana

  Scientific Reports 13 (1) 2045-2322 2023/08/29 

  Abstract In the samples collected from the asteroid Ryugu, magnetite displays natural remanent magnetization due to nebular magnetic field, whereas contemporaneously grown iron sulfide does not display stable remanent magnetization. To clarify this counterintuitive feature, we observed their nanoscale magnetic domain structures using electron holography and found that framboidal magnetites have an external magnetic field of 300 A m⁻¹, similar to the bulk value, and its magnetic stability was enhanced by interactions with neighboring magnetites, permitting a disk magnetic field to be recorded. Micrometer-sized pyrrhotite showed a multidomain magnetic structure that was unable to retain natural remanent magnetization over a long time due to short relaxation time of magnetic-domain-wall movement, whereas submicron-sized sulfides formed a nonmagnetic phase. These results show that both magnetite and sulfide could have formed simultaneously during the aqueous alteration in the parent body of the asteroid Ryugu.
• Observation of hydrogen-ordered cubic ice thin films on the surface of ice Ic nanocrystals upon coarsening

  Akira Kouchi, Tomoya Yamazaki, Hiroyasu Katsuno, Hiroki Nada, Tetsuya Hama, Yuki Kimura

  Chemical Physics 572 111966 - 111966 0301-0104 2023/08
• Formation and evolution of carbonaceous asteroid Ryugu: Direct evidence from returned samples

  Tomoki Nakamura, Megumi Matsumoto, Kana Amano, Yuma Enokido, Michael Zolensky, Takashi Mikouchi, Hidenori Genda, Satoshi Tanaka, M. Y. Zolotov, Kosuke Kurosawa, Shigeru Wakita, Ryuki Hyodo, H. Nagano, D. Nakashima, Takahashi Yoshio, Y. Fujioka, M. Kikuiri, E. Kagawa, Moe Matsuoka, Adrian Brearley, Akira Tsuchiyama, Masayuki Uesugi, Junya Matsuno, Yuki Kimura, M. Sato, Ralph Milliken, Eri Tatsumi, Seiji Sugita, Takahiro Hiroi, Kohei Kitazato, D. Brownlee, D. J. Joswiak, M. Takahashi, Kazuhiko Ninomiya, T. Takahashi, Takahito Osawa, Kentaro Terada, Frank Erich Brenker, B. J. Tkalcec, L. Vincze, Rosario Brunetto, A. Aléon-Toppani, Queenie Hoi Shan Chan, Mathieu Roskosz, Jean-Christophe VIENNET, Pierre Beck, E. E. Alp, Tatsuhiro Michikami, Yuuya Nagaashi, Takeshi Tsuji, Y. Ino

  Science 0036-8075 2023/02 

  Samples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We analyzed 17 Ryugu samples measuring 1 to 8 millimeters. Carbon dioxide–bearing water inclusions are present within a pyrrhotite crystal, indicating that Ryugu’s parent asteroid formed in the outer Solar System. The samples contain low abundances of materials that formed at high temperatures, such as chondrules and calcium- and aluminum-rich inclusions. The samples are rich in phyllosilicates and carbonates, which formed through aqueous alteration reactions at low temperature, high pH, and water/rock ratios of <1 (by mass). Less altered fragments contain olivine, pyroxene, amorphous silicates, calcite, and phosphide. Numerical simulations, based on the mineralogical and physical properties of the samples, indicate that Ryugu’s parent body formed ~2 million years after the beginning of Solar System formation.
• Nucleation experiments on a titanium-carbon system imply nonclassical formation of presolar grains

  Yuki Kimura, Kyoko K. Tanaka, Yuko Inatomi, Coskun Aktas, Jürgen Blum

  Science Advances 9 (2) 2023/01/13 

  Just as the shapes of snowflakes provide us with information on the temperature and humidity of the upper atmosphere, the characteristics of presolar grains in meteorites place limits on their formation environment in a stellar outflow. However, even in the case of well-characterized presolar grains consisting of a titanium carbide core and a graphitic carbon mantle, it is not possible to delimit their formation environment. Here, we have demonstrated the formation of core-mantle grains in gravitational and microgravity environments and have found that core-mantle grains are formed by a nonclassical nucleation pathway involving the three steps: (i) primary nucleation of carbon at a substantially high supersaturation, (ii) heterogeneous condensation of titanium carbide on the carbon, and (iii) fusion of nuclei. We argue that the characteristics of not only core-mantle grains but also other presolar and solar grains might be accurately explained by considering a nonclassical nucleation pathway.
• Rock Magnetic Characterization of Returned Samples From Asteroid (162173) Ryugu: Implications for Paleomagnetic Interpretation and Paleointensity Estimation

  Masahiko Sato, Yuki Kimura, Satoshi Tanaka, Tadahiro Hatakeyama, Seiji Sugita, Tomoki Nakamuna, Shogo Tachibana, Hisayoshi Yurimoto, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Fuyuto Terui, Satoru Nakazawa, Sei‐ichiro Watanabe, Yuichi Tsuda

  Journal of Geophysical Research: Planets 127 (11) 2169-9097 2022/11
• Low-Temperature Hydrothermal Synthesis of Chromian Spinel from Fe-Cr Hydroxides Using a Flow-Through Reactor

  Yoko Ohtomo, Jeehyun Yang, Miu Nishikata, Daisuke Kawamoto, Yuki Kimura, Tsubasa Otake, Tsutomu Sato

  Minerals 2075-163X 2022/08/30 

  Recent studies have suggested that a chromian spinel can be formed under natural hydrothermal conditions; however, the required conditions, process, and associated redistribution of Cr are still poorly understood. Here, chromian spinel formation was performed by Fe-Cr hydroxides alteration with an Fe2+(aq) supply at 150, 170, and 200 °C and 5 MPa simulating the diagenetic process. The flow-through system enabled the Fe2+(aq) supply to be leached from the magnetite by an acidic solution to synthesize Fe-Cr hydroxides as the starting material with two reaction cells, flow lines, heaters, and a high-performance liquid chromatography (HPLC) pump. The accuracy of the temperature measurement was confirmed based on the amorphous silica solubility. Mineralogical analysis of solid samples recovered from the reaction cell indicated that the chromian spinel was formed between 150 and 170 °C from Fe-Cr hydroxides through goethite with a simultaneous hematite formation, while Mössbauer spectra showed that a large quantity of Fe-Cr ferrihydrites still remained after the experiments probably because of the Cr addition to the stability of ferrihydrites. The Cr/Fe ratio of the chromian spinel was smaller than that of the bulk of the Fe-Cr ferrihydrites and equivalent to Cr-rich magnetite, suggesting a redistribution of Cr during the transformation from goethite to synthesized spinel under the hydrothermal conditions.
• Chiral Ice Crystals in Space

  Akira Kouchi, Takashi Shimonishi, Tomoya Yamazaki, Masashi Tsuge, Naoki Nakatani, Kenji Furuya, Hiromasa Niinomi, Yasuhiro Oba, Tetsuya Hama, Hiroyasu Katsuno, Naoki Watanabe, Yuki Kimura

  Chirality - New Insights [Working Title] 2022/08/22 

  We observed the formation of CO, CH3OH, and H2O ices using a cryogenic transmission electron microscope, to determine if chiral ice crystals could form under the conditions of interstellar molecular clouds and young stellar objects (protoplanetary disks) and to clarify the crystalline structure of these ices. Our results suggest that the following ice crystals are chiral: crystalline CO (α-CO) formed on amorphous H2O (a-H2O) grains in a 10-K molecular cloud, crystalline CH3OH formed by the heating of amorphous CH3OH on a-H2O grains at 40–60 K in young stellar objects, and several polymorphs of hydrogen-ordered cubic ice crystals formed by the heating of a-H2O at 80–100 K and direct condensation at 120–140 K in protoplanetary disks. We also investigated candidates for other chiral ices using published data. We found that NH3 I and NH3·H2O I are chiral at low temperature and pressure conditions. If one-handed circularly polarized light is irradiated during the nucleation of these chiral ice crystals, homochiral crystals can be formed. These results have important implications for the origin of interstellar organic molecule homochirality.
• Feasibility of control of particle assembly by dielectrophoresis in liquid-cell transmission electron microscopy.

  Tomoya Yamazaki, Hiromasa Niinomi, Yuki Kimura

  Microscopy (Oxford, England) 71 (4) 231 - 237 2022/08/01 

  Liquid-cell transmission electron microscopy (LC-TEM) is a useful technique for observing phenomena in liquid samples with spatial and temporal resolutions similar to those of conventional transmission electron microscopy (TEM). This method is therefore expected to permit the visualization of phenomena previously inaccessible to conventional optical microscopy. However, dynamic processes such as nucleation are difficult to observe by this method because of difficulties in controlling the condition of the sample liquid in the observation area. To approach this problem, we focused on dielectrophoresis, in which electrodes are used to assemble particles, and we investigated the phenomena that occurred when an alternating-current signal was applied to an electrode in an existing liquid cell by using a phase-contrast optical microscope (PCM) and TEM. In PCM, we observed that colloidal particles in a solution were attracted to the electrodes to form assemblies, that the particles aligned along the electric field to form pearl chains and that the pearl chains accumulated to form colloidal crystals. However, these phenomena were not observed in the TEM study because of differences in the design of the relevant holders. The results of our study imply that the particle assembly by using dielectrophoretic forces in LC-TEM should be possible, but further studies, including electric device development, will be required to realize this in practice.
• Liquid-Cell Transmission Electron Microscopy Observation of Two-Step Collapse Dynamics of Silicon Nanopillars on Evaporation of Propan-2-ol: Implications for Semiconductor Integration Density

  Yuta Sasaki, Tomoya Yamazaki, Yuki Kimura

  ACS Applied Nano Materials 2022/07/22
• Possible embryos and precursors of crystalline nuclei of calcium carbonate observed by liquid-cell transmission electron microscopy.

  Yuki Kimura, Hiroyasu Katsuno, Tomoya Yamazaki

  Faraday discussions 235 81 - 94 2022/07/14 

  Several different building blocks or precursors play an important role in the early stages of the crystallization of calcium carbonate (CaCO3). Many studies have been conducted over a long period to elucidate the fundamental processes involved in this crystallization. Here, we report the role of an amorphous phase and embryo at the beginning of the nucleation of CaCO3 from solutions of relatively low supersaturation. Prenucleation crystals formed in amorphous calcium carbonate (ACC) at a significantly large formation rate of 2 × 1022 m-3 s-1, suggesting that a low interfacial energy exists between the ACC and crystals. Only one calcite crystal exceeded the size for a critical nucleus (∼104 molecules) in 150 pre-nucleation crystals. Each pre-nucleation crystal might consist of a different polymorph, and ACCs have a similar composition and structure. A particle-detection algorithm, used in conjunction with machine learning, suggested that an embryo with a characteristic structure exists in solution and might play a crucial role in nucleation. No similar embryonic structure could be observed immediately after the dissolution of pre-nucleation particles, implying that their dissolution process is not simply the reverse process of their growth. This method should provide a new approach to understanding nucleation processes.
• Inefficient Growth of SiOx Grains: Implications for Circumstellar Outflows

  Yuki Kimura, Kyoko K. Tanaka, Yuko Inatomi, Frank T. Ferguson, Joseph A. Nuth

  ASTROPHYSICAL JOURNAL LETTERS 934 (1) 2041-8205 2022/07 

  To explain observations of abundant circumstellar dust and high stellar wind velocity, most models simply postulate the efficient nucleation and growth of silicate dust particles. Here, we report measurement of the SiO-(SiOx)(n) grain sticking coefficient in a microgravity sounding rocket experiment, indicating very inefficient (0.005-0.016) grain formation from the vapor. Application of this measurement to radiative-driven winds in oxygen-rich asymptotic giant branch stars indicates that the initial grain condensate population should consist of very tiny dust particles in very large numbers. Aggregation of this dust population will produce low-dimension fractal aggregates that should couple well to the stellar radiation field and efficiently drive stellar mass loss.
• Low- and High-Density Unknown Waters at Ice-Water Interfaces

  Hiromasa Niinomi, Akira Kouch, Tetsuya Hama, Hiroki Nada, Tomoya Yamazaki, Yuki Kimura

  JOURNAL OF PHYSICAL CHEMISTRY LETTERS 13 (19) 4251 - 4256 1948-7185 2022/05 

  Experimental confirmation of liquid polymorphs of water, high-density liquid (HDL) and low-density liquid (LDL), is desired for understanding not only the liquid state of matter but also the origin of the mysterious properties of water. However, this remains challenging because the liquid-liquid critical point of water lies in experimentally inaccessible supercooling conditions known as "no man's land". Here, we show by in situ optical microscopy that droplets and layers of low- and high-density unknown waters (LDUW and HDUW) appear macroscopically depending upon ice polymorphs at non-equilibrium interfaces between water and ices under experimentally accessible (de)pressurization conditions. These unknown waters were found to have characteristic velocities (about 20 and 100 m/s for LDUW and HDUW, respectively) different from water (about 40 m/s) and quasi-liquid layers (QLLs) (about 2 and 0.2 m/s for droplet and layer forms of QLLs, respectively). Our discoveries provide insight on liquid polymorphism of water.
• Direct observation of the moment of nucleation from a solution by TEM

  Yuki Kimura

  Microscopy 2050-5698 2022/01/29 

  Abstract Recent discoveries of various nucleation processes make understanding the initial processes of crystallization, where atoms and molecules come together to form a crystal nucleus, difficult. Herein, transmission electron microscopy is used to directly visualize the moment of nucleation from a solution and to show that the singular phenomena of nanoparticles are critical to understanding nucleation. Our work revealed that nanoparticles undergo precipitation and dissolution even in undersaturated and equilibrium conditions, that crystal polymorphs formed at different frequencies compete, that molecules follow various nucleation pathways in the same solution, and that the hydration layer plays a critical role in crystallization. The observations visually support the common belief that dehydration is the greatest barrier to crystallization in an aqueous solution. These results are expected to contribute to the development of a unified nucleation model.
• 極低電子線観察を可能にする深層学習によるTEM画像の鮮明化—Improvement of ultra-low dose electron image of TEM by deep learning—特集 機械学習・AIは結晶成長研究をいかに変えるか?

  勝野 弘康, 木村 勇気, 山﨑 智也, 瀧川 一学

  日本結晶成長学会誌 Journal of the Japanese Association for Crystal Growth 49 (1) 1 - 8 2188-7268 2022 [Refereed][Invited]
  
• Early Detection of Nucleation Events From Solution in LC-TEM by Machine Learning.

  Hiroyasu Katsuno, Yuki Kimura, Tomoya Yamazaki, Ichigaku Takigawa

  Frontiers in chemistry 10 818230 - 818230 2022 [Refereed]
   

  To support the detection, recording, and analysis of nucleation events during in situ observations, we developed an early detection system for nucleation events observed using a liquid-cell transmission electron microscope. Detectability was achieved using the machine learning equivalent of detection by humans watching a video numerous times. The detection system was applied to the nucleation of sodium chloride crystals from a saturated acetone solution of sodium chlorate. Nanoparticles with a radius of more greater than 150 nm were detected in a viewing area of 12 μm × 12 μm by the detection system. The analysis of the change in the size of the growing particles as a function of time suggested that the crystal phase of the particles with a radius smaller than 400 nm differed from that of the crystals larger than 400 nm. Moreover, the use of machine learning enabled the detection of numerous nanometer sized nuclei. The nucleation rate estimated from the machine-learning-based detection was of the same order as that estimated from the detection using manual procedures.
• Improvement of ultra-low dose electron image of TEM by deep learning

  Katsuno Hiroyasu, Kimura Yuki, Yamazaki Tomoya, Takigawa Ichigaku

  Journal of the Japanese Association for Crystal Growth 日本結晶成長学会 49 (1) n/a  0385-6275 2022
• 液中における核生成過程の透過型電子顕微鏡その場観察

  勇気 木村

  顕微鏡 1349-0958 2021/12/30
• UV-Induced Formation of Ice XI Observed Using an Ultra-High Vacuum Cryogenic Transmission Electron Microscope and its Implications for Planetary Science

  Akira Kouchi, Yuki Kimura, Kensei Kitajima, Hiroyasu Katsuno, Hiroshi Hidaka, Yasuhiro Oba, Masashi Tsuge, Tomoya Yamazaki, Kazuyuki Fujita, Tetsuya Hama, Yukihiro Takahashi, Shunichi Nakatsubo, Naoki Watanabe

  Frontiers in Chemistry 9 2021/12/08 

  The occurrence of hydrogen atom-ordered form of ice Ih, ice XI, in the outer Solar System has been discussed based on laboratory experiments because its ferroelectricity influences the physical processes in the outer Solar System. However, the formation of ice XI in that region is still unknown due to a lack of formation conditions at temperatures higher than 72 K and the effect of UV-rays on the phase transition from ice I to ice XI. As a result, we observed the UV-irradiation process on ice Ih and ice Ic using a newly developed ultra-high vacuum cryogenic transmission electron microscope. We found that ice Ih transformed to ice XI at temperatures between 75 and 140 K with a relatively small UV dose. Although ice Ic partially transformed to ice XI at 83 K, the rate of transformation was slower than for ice Ih. These findings point to the formation of ice XI at temperatures greater than 72 K via UV irradiation of ice I crystals in the Solar System; icy grains and the surfaces of icy satellites in the Jovian and Saturnian regions.
• Formation of ice particles through nucleation in the mesosphere

  Kyoko Tanaka, Ingrid Mann, Yuki Kimura

  Atmospheric Chemistry and Physics 2021/10/14 

  Abstract. Observations of polar mesospheric clouds have revealed the presence of solid ice particles in the upper mesosphere at high latitudes; however, their formation mechanism remains uncertain. In this study, we investigated the formation process of ice particles through nucleation from small amounts of water vapor at low temperatures. Previous studies that used classical nucleation theory have shown that amorphous solid water particles can nucleate homogeneously at conditions that are present in the mesosphere. However, the rate predictions for water in classical nucleation theory disagree with experimental measurements by several orders of magnitude. We adopted a semi-phenomenological model for the nucleation process, which corrects the evaluation of the molecular cluster formation energy using the second virial coefficient, which agrees with both experiments and molecular dynamics simulations. To calculate the nucleation process, we applied atmospheric conditions for the temperature, pressure, numerical density of dust grains, and cooling rate. The results indicate that homogeneous water nucleation is extremely unlikely to occur in the mesosphere, while heterogeneous nucleation occurs effectively. Dust grains generated by meteor ablation can serve as nuclei for heterogeneous nucleation. We also showed that the ice can form directly in a crystalline state, rather than an amorphous state.
• Transmission Electron Microscopy Study of the Morphology of Ices Composed of H2O, CO2, and CO on Refractory Grains

  Akira Kouchi, Masashi Tsuge, Tetsuya Hama, Yasuhiro Oba, Satoshi Okuzumi, Sin-iti Sirono, Munetake Momose, Naoki Nakatani, Kenji Furuya, Takashi Shimonishi, Tomoya Yamazaki, Hiroshi Hidaka, Yuki Kimura, Ken-ichiro Murata, Kazuyuki Fujita, Shunichi Nakatsubo, Shogo Tachibana, Naoki Watanabe

  The Astrophysical Journal 918 (2) 45 - 45 0004-637X 2021/09/01 [Refereed]
  
• On the Nature of Organic Dust in Novae

  Izumi Endo, Itsuki Sakon, Takashi Onaka, Yuki Kimura, Seiji Kimura, Setsuko Wada, L. Andrew Helton, Ryan M. Lau, Yoko Kebukawa, Yasuji Muramatsu, Nanako O. Ogawa, Naohiko Ohkouchi, Masato Nakamura, Sun Kwok

  The Astrophysical Journal 917 (2) 103 - 103 0004-637X 2021/08/01 [Refereed]
  
• Electron Holography Details the Tagish Lake Parent Body and Implies Early Planetary Dynamics of the Solar System

  Yuki Kimura, Kazuo Yamamoto, Shigeru Wakita

  The Astrophysical Journal Letters 917 (1) L5 - L5 2041-8205 2021/08/01 [Refereed]
  
• Formation of chiral CO polyhedral crystals on icy interstellar grains

  Akira Kouchi, Masashi Tsuge, Tetsuya Hama, Hiromasa Niinomi, Naoki Nakatani, Takashi Shimonishi, Yasuhiro Oba, Yuki Kimura, Sin-iti Sirono, Satoshi Okuzumi, Munetake Momose, Kenji Furuya, Naoki Watanabe

  Monthly Notices of the Royal Astronomical Society 505 (1) 1530 - 1542 0035-8711 2021/06/03 [Refereed]
   

  The crystallinity and morphology of solid carbon monoxide (CO) on icy interstellar grains were examined by observing the deposition, crystallization, and UV and electrons irradiation of solid CO using transmission electron microscopy. Herein, we found that solid CO deposited in molecular clouds was crystalline, and that even if amorphous CO was deposited, amorphous CO crystallized within 103 yr at 10 K. Conversely, crystalline CO was not amorphized by UV rays or electron beam at 10 K. These results indicated the occurrence of chiral crystalline CO instead of amorphous CO in space. Furthermore, the large surface diffusion coefficients of CO on eamorphous H2O and crystalline CO at 10 K facilitated the morphological equilibration of crystalline CO. Bad wetting of crystalline CO with amorphous H2O proved that the morphology of the ice grains was not spherical with an onion-like structure, as hitherto assumed, but rather it was a polyhedral crystalline CO attached to amorphous H2O. This has important implications for phenomena associated with the collision and subsequent sticking between ice grains, surface chemical reactions, non-thermal desorption of molecules and the origin of homochirality in interstellar biomolecules.
• Radiolysis-Induced Crystallization of Sodium Chloride in Acetone by Electron Beam Irradiation

  Tomoya Yamazaki, Yuki Kimura

  Microscopy and Microanalysis 27 (3) 459 - 465 1431-9276 2021/06 [Refereed]
   
• Fast improvement of TEM image with low-dose electrons by deep learning.

  Hiroyasu Katsuno, Yuki Kimura, Tomoya Yamazaki, Ichigaku Takigawa

  CoRR abs/2106.01718 2021
• In-situ water-immersion experiments on amorphous silicates in the MgO–SiO2 system: implications for the onset of aqueous alteration in primitive meteorites

  Yohei Igami, Akira Tsuchiyama, Tomoya Yamazaki, Megumi Matsumoto, Yuki Kimura

  Geochimica et Cosmochimica Acta 293 86 - 102 0016-7037 2021/01 [Refereed]
   

  Amorphous silicates, abundant in primitive carbonaceous chondrites, are among the most primitive materials from the early Solar System. They show evidence of some aqueous alteration in the meteorite parent bodies, but it is not clear how this highly reactive material changed at an early stage after contact with water. Herein, we report in-situ experiments on the aqueous alteration of amorphous silicate nanoparticles (typically 70 nm in diameter); we used two different compositions that are similar to forsterite (MgO/SiO = 2.02) and enstatite (MgO/SiO = 1.15) in the simple MgO–SiO system to understand basic reaction principles at the onset of the aqueous alteration. The experiments were performed in pure water at room temperature using X-ray diffraction (XRD), transmission electron microscopy (TEM), and pH measurements. The in-situ TEM images of the nanoparticles—in particular those with the forsterite composition—gradually became difficult to recognize in water. The pH value of the water also increased with time, suggesting that preferential Mg dissolution occurred from the amorphous silicates right after mixing with water. The in-situ XRD patterns showed that magnesium silicate hydrate (M-S-H), which is a poorly crystalline phase like a phyllosilicate, newly appeared. The M-S-H seems to have been formed via a dissolution–precipitation process. Its formation rate from amorphous silicates was considerably higher than from crystalline silicates, because amorphous silicates are highly metastable and have high solubility in water. M-S-H formation from the forsterite composition, which has a highly unstable amorphous structure, is ten times faster than from the enstatite composition. The M-S-Hs show string-like or tiny fragmental textures in the final dried products that are very similar to those observed in the matrices of some primitive carbonaceous chondrites. M-S-H would have been the initial product formed in the aqueous alteration of amorphous silicates in the meteorites; thus, it is an important tracer of early aqueous activity at low temperatures in the early Solar System. By comparing the in-situ observations with those obtained after drying the experimental samples, we found two types of M-S-Hs: epigenetic M-S-Hs—which have a slightly Si-rich composition—formed during drying, and syngenetic M-S-Hs formed by in-situ alteration. Carbonaceous chondrites may also contain these two types of hydrous silicates, and this should be investigated to understand the conditions for aqueous alteration in the early Solar System in more detail. The present study clearly showed the importance of Mg/Si ratio in the precursor materials, although the actual chondrites are in more complicated multi-component system. Future experiments based on the present results can extend the investigation to the system containing Fe, S, and other components as in carbonaceous chondrites. 2 2 2 2+
• Precometary organic matter: A hidden reservoir of water inside the snow line

  Hideyuki Nakano, Naoki Hirakawa, Yasuhiro Matsubara, Shigeru Yamashita, Takuo Okuchi, Kenta Asahina, Ryo Tanaka, Noriyuki Suzuki, Hiroshi Naraoka, Yoshinori Takano, Shogo Tachibana, Tetsyua Hama, Yasuhiro Oba, Yuki Kimura, Naoki Watanabe, Akira Kouchi

  Scientific Reports 10 7755  2020/12 [Refereed][Not invited]
  
• High-Density Liquid Water at a Water–Ice Interface

  Hiromasa Niinomi, Tomoya Yamazaki, Hiroki Nada, Tetsuya Hama, Akira Kouchi, Junpei T. Okada, Jun Nozawa, Satoshi Uda, Yuki Kimura

  The Journal of Physical Chemistry Letters 11 (16) 6779 - 6784 1948-7185 2020/08/20 [Refereed]
  
• Time-Resolved Observation of Evolution of Amyloid-β Oligomer with Temporary Salt Crystals.

  Kichitaro Nakajima, Tomoya Yamazaki, Yuki Kimura, Masatomo So, Yuji Goto, Hirotsugu Ogi

  The journal of physical chemistry letters 11 (15) 6176 - 6184 2020/08/06 [Refereed]
   

  The aggregation behavior of amyloid-β (Aβ) peptides remains unclarified despite the fact that it is closely related to the pathogenic mechanism of Alzheimer's disease. Aβ peptides form diverse oligomers with various diameters before nucleation, making clarification of the mechanism involved a complex problem with conventional macroscopic analysis methods. Time-resolved single-molecule level analysis in bulk solution is thus required to fully understand their early stage aggregation behavior. Here, we perform time-resolved observation of the aggregation dynamics of Aβ oligomers in bulk solution using liquid-state transmission electron microscopy. Our observations reveal previously unknown behaviors. The most important discovery is that a salt crystal can precipitate even with a concentration much lower than its solubility, and it then dissolves in a short time, during which the aggregation reaction of Aβ peptides is significantly accelerated. These findings will provide new insights in the evolution of the Aβ oligomer.
• Formation experiments of organic molecules by catalytic reactions in low-temperature and low-pressure environments

  Yuki Kimura, Rikako Sato, AkiraTsuchiyama, YusukeTamenori, Tetsuya Hama, Hiroshi Hidaka, Naoki Watanabe, Akira Kouchi, Hiroko Nagahara

  Low Temperature Science 78 79 - 90 2020/03 [Refereed]
  
• High mobility of lattice molecules and defects during the early stage of protein crystallization

  Tomoya Yamazaki, Alexander E. S. Van Driessche, Yuki Kimura

  Soft Matter 16 (8) 1955 - 1960 1744-683X 2020 [Refereed]
   

  Dynamic behavior of defects in lysozyme protein crystals reveals that the lattice molecules are mobile throughout the crystal.

• Exposure Experiments of Amorphous Silicates and Organics to Cometary Ice and Vapor Analogs

  Aki Takigawa, Yoshihiro Furukawa, Yuki Kimura, Bjorn Davidsson, Tomoki Nakamura

  ASTROPHYSICAL JOURNAL 881 (1) 27  0004-637X 2019/08 [Refereed][Not invited]
   

  Hydration is a major mineral alteration process in primitive asteroids and it might occur in comet nuclei; however, it is poorly understood at low temperatures, especially below the freezing point of water. Long-duration experiments were performed with exposures of amorphous silicate nanoparticles and organic compounds (glycine and ribose) to D2O and D2O + NH3 ices and vapors at temperatures of -17 degrees C and -27 degrees C for 10-120 days; and with exposure of amorphous silicates to H2O vapor/liquid at >25 degrees C for 10 days. The amorphous silicates were analyzed by X-ray diffraction and Fourier-transform infrared spectroscopy, and recovery of organic molecules was determined by liquid chromatography-mass spectrometry. No hydration of amorphous silicates or organic compounds was observed after exposure at temperatures below -17 degrees C for 120 days to ices with or without NH3, whereas hydration of the amorphous silicates was observed in experiments above room temperature. The estimated thermal history of the nucleus of the short-period comet 67P/Churyumov-Gerasimenko indicates that the surface temperature does not exceed -45 degrees C, even in a region exposed to strong solar illumination during the perihelion passage. Assuming hydration is controlled by the collision frequency between H2O molecules and dust particles, the present results indicate that cometary dust does not hydrate for more than 25-510 periods of comet 67P. This is consistent with the absence of phyllosilicates on 67P and suggests that amino acids and sugars have not been altered.
• Interactions of Atomic and Molecular Hydrogen with a Diamond-like Carbon Surface: H2 Formation and Desorption

  Masashi Tsuge, Tetsuya Hama, Yuki Kimura, Akira Kouchi, Naoki Watanabe

  The Astrophysical Journal 878 (1) 23  0004-637X 2019/06 [Refereed][Not invited]
   

  The interactions of atomic and molecular hydrogen with bare interstellar dust grain surfaces are important for understanding H-2 formation at relatively high temperatures (>20 K). We investigate the diffusion of physisorbed H atoms and the desorption energetics of H-2 molecules on an amorphous diamond-like carbon (DLC) surface. From temperature-programmed desorption experiments with a resonance-enhanced multiphoton ionization (REMPI) method for H-2 detection, the H-2 coverage-dependent activation energies for H-2 desorption are determined. The activation energies decrease with increasing H-2 coverage and are centered at 30 meV with a narrow distribution. Using a combination of photostimulated desorption and REMPI methods, the time variations of the surface number density of H-2 following atomic and molecular hydrogen depositions are studied. From these measurements, we show that H-2 formation on a DLC surface is quite efficient, even at 20 K. A significant kinetic isotope effect for H-2 and D-2 recombination reactions suggests that H-atom diffusion on a DLC surface is mediated by quantum mechanical tunneling. In astrophysically relevant conditions, H-2 recombination due to physisorbed H-atoms is unlikely to occur at 20 K, suggesting that chemisorbed H atoms might play a role in H-2 formation at relatively high temperatures.
• Theoretical analysis of crystallization by homogeneous nucleation of water droplets

  Kyoko K. Tanaka, Yuki Kimura

  Physical Chemistry Chemical Physics 21 2410 - 2418 2019/01 [Refereed][Not invited]
  
• Space Exposure Experiment of Carbonaceous Dust

  I. Sakon, I. Endo, A. Ikeuchi, T. Onaka, Y. Kimura, S. Kimura, S. Wada, M. Nakamura, J. Ichimura, N. Ogawa, N. Ohkouchi, Y. Inatomi

  Aeronautical and Space Sciences Japan 一般社団法人 日本航空宇宙学会 66 (12) 381 - 387 0021-4663 2018/12 [Refereed][Not invited]
   

  国際宇宙ステーション「きぼう」利用簡易曝露実験装置ExHAMを利用した炭素質ダストの宇宙曝露実験は，年老いた星周環境で凝縮したダストが星間空間に至り次世代の星形成活動に寄与するまでの過程で被る物性変化を調べることを目的とする試みである．本実験では，未同定赤外バンド担い手の同定に焦点をあて，実験室で合成するダストである膜状急冷炭素質物質をはじめとして，約30種の実験試料を1年間，国際宇宙ステーションの軌道環境に曝露し，曝露前後の物質の赤外分光特性や物性変化の調査を実施している．この記事では，本曝露実験の概要と進捗状況を示すとともに，主要な実験試料の1つである膜状急冷炭素質物質に焦点をあて，宇宙環境曝露実験前後での赤外線吸光スペクトルの変化に関する初期成果の一部を紹介する．

• Immiscibility of Nucleating Aluminum Oxide Nanoparticles in Vapor

  Shinnosuke Ishizuka, Yuki Kimura, Jun Kawano, Rafael Escribano, Tomoya Yamazaki, Tetsuya Hama, Rikako Sato

  The Journal of Physical Chemistry C 122 (43) 25092 - 25101 2018/11/01 [Refereed][Not invited]
  
• Sounding-rocket microgravity experiments on alumina dust

  Shinnosuke Ishizuka, Yuki Kimura, Itsuki Sakon, Hiroshi Kimura, Tomoya Yamazaki, Shinsuke Takeuchi, Yuko Inatomi

  Nature Communications 9 (1) 3820 - 3820 2018/09 [Refereed][Not invited]
   

  Alumina (Al2O3) is believed to be the first major condensate to form in the gas outflow from oxygen-rich evolved stars because of the refractoriness and that α-Al2O3 (corundum, most stable polymorph) is a potential origin of a 13 μm feature that appears close to stars. However, no one has directly reproduced the 13 μm feature experimentally, and it has remained as a noteworthy unidentified infrared band. Here, we report nucleation experiments on Al2O3 nanoparticles monitored by a specially designed infrared spectrometer in the microgravity environment of a sounding rocket. The conditions approximate to those around asymptotic giant branch (AGB) stars. The measured spectra of the nucleated Al2O3 show a sharp feature at a wavelength of 13.55 μm and comparable in width to that observed near oxygen-rich AGB stars. Our finding that α-Al2O3 nucleates under certain condition provides a solid basis to elaborate condensation models of dust around oxygen-rich evolved stars.
• Nucleation Processes of Cosmic Dust Investigated by Microgravity Experiments using an Airplane

  Yuki Kimura, Shinnosuke Ishizuka, Sašo Šturm, Kyoko K. Tanaka, Tomoya Yamazaki, Fumiaki Saito, Yosuke Satoh, Katsuo Tsukamoto, Yuko Inatomi

  International Journal of Microgravity Science and Application 35 (3) 350305  0915-3616 2018/07 [Refereed][Not invited]
   

  Cosmic dust, which is composed of nanometer-sized particles and is ubiquitously distributed in the universe, is formed in a gas outflow from evolved stars under a microgravity environment. Its formation processes have been studied on the basis of knowledge obtained under the 1 G environment on Earth and is thus not fully understood under realistic conditions. To better understand the process, here, we performed nucleation experiments of dust analogs under a microgravity environment. We show the details of our experiments using an aircraft including results of in-situ observation employing an interferometer and ex-situ transmission electron microscopy to reveal the difficulty of nucleation and variability of nucleation processes. Of particular note is the size distribution of the produced particle, which was monotonical in microgravity experiments against a double peak for particles produced in the laboratory. Under a microgravity environment, nucleation tends to suppress because of smaller density fluctuation due to convection free and less turbulence due to smaller Reynolds number which gives atoms/molecules (particles) smaller chance to collide with each other for nucleation (coagulation).
• Measurements of the Activation Energies for Atomic Hydrogen Diffusion on Pure Solid CO

  Y. Kimura, M. Tsuge, V. Pirronello, A. Kouchi, N. Watanabe

  Astrophysical Journal Letters 858 (2) 23  2041-8213 2018/05/10 [Refereed][Not invited]
   

  The diffusion of hydrogen atoms on dust grains is a key process in the formation of interstellar H2 and some hydrogenated molecules such as formaldehyde and methanol. We investigate the adsorption and diffusion of H atoms on pure solid CO as an analog of dust surfaces observed toward some cold interstellar regions. Using a combination of photostimulated desorption and resonance-enhanced multiphoton ionization methods to detect H atoms directly, the relative adsorption probabilities and diffusion coefficients of the H atoms are measured on pure solid CO at 8, 12, and 15 K. There is little difference between the diffusion coefficients of the hydrogen and deuterium atoms, indicating that the diffusion is limited by thermal hopping. The activation energies controlling the H-atom diffusion depend on the surface temperature, and values of 22, 30, and ∼37 meV were obtained for 8, 12, and 15 K, respectively.
• Direct Transmission Electron Microscopy Visualization of the Cement Reaction by Colloidal Aggregation of Fumed Silica

  Hisao Satoh, Yuki Kimura, Erika Furukawa

  Industrial and Engineering Chemistry Research 57 (1) 79 - 83 1520-5045 2018/01/10 [Refereed][Not invited]
   

  Unlike other solidified materials, concrete has an internal structure that contains small pores that vary in size from several nanometers to the submicrometer range. These pores govern the strength of the material and hence the lifetime of concrete buildings. The size of the pores is governed by the presence of calcium silicate hydrate (CaO·2SiO2·4H2O, C-S-H). To identify how the pore size is determined during the concretion process, we used transmission electron microscopy to examine the early solidification of a simplified reaction system consisting of silica, portlandite [Ca(OH)2, CH], and water. The silica particles, used to suppress the degradation of concrete, expanded and, consequently, embedded the pores through hydration before C-S-H was formed, contrary to the predicted decrease in pore size by C-S-H formation after simple dissolution of silica. Visualization of this type of solidification process should permit improvement in the mechanical strength of concrete.
• Development of an ultrahigh vacuum low temperature transmission electron microscope for in-situ observation of ices

  Akira KOUCHI, Hiroshi HIDAKA, Naoki WATANABE, Tetsuya HAMA, Yuki KIMURA, Shunichi NAKATSUBO, Kazuyuki FUJITA, Kunio SINBORI, Masayuki IKEDA

  日本雪氷学会誌 雪氷 80 (1) 19 - 36 2018/01 [Refereed][Not invited]
  
• Experiments on Condensation of Calcium Sulfide Grains To Demarcate Environments for the Formation of Enstatite Chondrites

  Kaori Yokoyama, Yuki Kimura, Chihiro Kaito

  ACS EARTH AND SPACE CHEMISTRY 1 (10) 601 - 607 2472-3452 2017/12 [Refereed][Not invited]
   

  To achieve a better understanding of material evolution in the early solar system, experiments have been performed to constrain the environments in which many of the dust grains formed. Sulfur is an element whose chemical processes and mineralization of related grains are poorly understood. The high reactivity of sulfur makes it difficult to perform experiments in conventional metallic chambers, because these become heavily contaminated. Nevertheless, sulfur is expected to be a key element to understand processes in the early solar system. Here, we performed experiments on the condensation of calcium sulfide (CaS) in a glass chamber in an attempt to identify constraints on the possible formation environments of components of enstatite chondrites in terms of the effects of oxygen. Condensation experiments showed that calcium sulfate (CaSO4) or solid-solution particles of CaS and calcium oxide (CaO), i.e., [Ca(S,O)], were formed at various partial pressures of oxygen. Our results expand the range of possible conditions for the condensation of meteoritic CaS (oldhamite) from a nebula gas and extend the range of environments for the formation of the parent bodies of enstatite chondrites to include those more oxidizing environments in the solar nebula, where the atomic ratio of oxygen to sulfur was less than 6 and where CaS could have incorporated oxygen to form Ca(S,O) without the formation of CaSO4.
• Liquid-like behavior of UV-irradiated interstellar ice analog at low temperatures.

  Shogo Tachibana, Akira Kouchi, Tetsuya Hama, Yasuhiro Oba, Laurette Piani, Iyo Sugawara, Yukiko Endo, Hiroshi Hidaka, Yuki Kimura, Ken-Ichiro Murata, Hisayoshi Yurimoto, Naoki Watanabe

  Science advances 3 (9) eaao2538  2017/09 [Refereed][Not invited]
   

  Interstellar ice is believed to be a cradle of complex organic compounds, commonly found within icy comets and interstellar clouds, in association with ultraviolet (UV) irradiation and subsequent warming. We found that UV-irradiated amorphous ices composed of H2O, CH3OH, and NH3 and of pure H2O behave like liquids over the temperature ranges of 65 to 150 kelvin and 50 to 140 kelvin, respectively. This low-viscosity liquid-like ice may enhance the formation of organic compounds including prebiotic molecules and the accretion of icy dust to form icy planetesimals under certain interstellar conditions.
• Self-assembly of MoO3 needles in gas current for cubic formation pathway

  Shinnosuke Ishizuka, Yuki Kimura, Satoki Yokoi, Tomoya Yamazaki, Rikako Sato, Tetsuya Hama

  NANOSCALE 9 (28) 10109 - 10116 2040-3364 2017/07 [Refereed][Not invited]
   

  Nucleation and subsequent rapid growth are enigmatic due to the unrevealed pathways. Despite the relatively simpler mechanism compared to nucleation and growth in solution, that in vapor has received little attention. The largest hindrance to unveiling this process may be observing the rapid and mesoscopic-scale phenomena. To overcome this hindrance, we combine an experimental approach with in situ spatial scanning Fourier-transform infrared spectroscopy, which reveals the nucleating and growing nanoparticles in vapor. The nanoparticles are then collected at different evolutionary stages and analyzed by ex situ transmission electron microscopy (TEM). Needle-shaped molybdenum oxide (MoO3) nanoparticles were formed within similar to 0.1 s after homogeneous nucleation from a highly supersaturated vapor. Over one second, the needle particles gradually evolved into a cubic shape by fusion in a crystallographically favored orientation in a free-flying state in vapor. The similar sizes of the elongated axes of the needle and cubic structures suggest an additional growth stage, in which the needle particles become the growth units of the cubic particles. The morphology of a final crystal should reflect the formation environment of the particle because growing crystals are sensitive to the formation conditions such as temperature, concentration, and impurities. Although nucleation under very high supersaturation induces the anisotropic growth of the needle particles, this information of the initial nucleation environment is lost in the final cubic crystal. These findings enrich our understanding of pathways in the nucleation and growth of nanoparticles and provide new insights into the growth stages driven by oriented attachment.
• Fast crystalline ice formation at extremely low temperature through water/neon matrix sublimation

  Tetsuya Hama, Shinnosuke Ishizuka, Tomoya Yamazaki, Yuki Kimura, Akira Kouchi, Naoki Watanabe, Toshiki Sugimoto, Valerio Pirronello

  PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 (27) 17677 - 17684 1463-9076 2017/07 [Refereed][Not invited]
   

  Crystalline ice formation requires water molecules to be sufficiently mobile to find and settle on the thermodynamically most stable site. Upon cooling, however, diffusion and rearrangement become increasingly kinetically difficult. Water ice grown by the condensation of water vapor in laboratory is thus generally assumed to be in a metastable amorphous form below 100 K. Here, we demonstrate the possibility of crystalline ice formation at extremely low temperature using a water/neon matrix (1/1000, 30000 monolayers) prepared at 6 K, which is subsequently warmed to 11-12 K. In situ infrared spectroscopy revealed the assembly of the dispersed water molecules, forming crystalline ice I during the sublimation of the neon matrix for 40-250 seconds. This finding indicates that the high mobility of the water molecules during matrix sublimation can overcome the kinetic barrier to form crystals even at extremely low temperature.
• Simulations and spectra of water in CO matrices

  Rafael Escribano, Emilio Artacho, Akira Kouchi, Tetusya Hama, Yuki Kimura, Hiroshi Hidaka, Naoki Watanabe

  PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 (10) 7280 - 7287 1463-9076 2017/03 [Refereed][Not invited]
   

  Models for the inclusion of water molecules in carbon monoxide matrices are developed using density functional theory applied to amorphous solid systems. The models cover a large range of systems for smaller or larger CO matrices with different water content, consisting of either individual H2O molecules or small clusters linked by H-bonds. The vibrational spectra of the samples are predicted at the minimum of their potential energy surface. The spectra allow instances where the water molecules remain isolated or form aggregates to be discerned, and they also provide an indication of the strength of the H-bonding, when present. The calculations support recent experimental observations that linked IR bands at 3707 cm(-1) and 3617 cm(-1) to the presence of unbound water molecules in water-poor CO/H2O mixed ices. Assignment of some observed bands to water dimers or trimers is suggested as well. The residual static pressure in fixed-volume simulation cells is also calculated.
• Simulations and spectra of water in CO matrices

  Rafael Escribano, Emilio Artacho, Akira Kouchi, Tetusya Hama, Yuki Kimura, Hiroshi Hidaka, Naoki Watanabe

  PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 (10) 7280 - 7287 1463-9076 2017/03 [Refereed][Not invited]
   

  Models for the inclusion of water molecules in carbon monoxide matrices are developed using density functional theory applied to amorphous solid systems. The models cover a large range of systems for smaller or larger CO matrices with different water content, consisting of either individual H2O molecules or small clusters linked by H-bonds. The vibrational spectra of the samples are predicted at the minimum of their potential energy surface. The spectra allow instances where the water molecules remain isolated or form aggregates to be discerned, and they also provide an indication of the strength of the H-bonding, when present. The calculations support recent experimental observations that linked IR bands at 3707 cm(-1) and 3617 cm(-1) to the presence of unbound water molecules in water-poor CO/H2O mixed ices. Assignment of some observed bands to water dimers or trimers is suggested as well. The residual static pressure in fixed-volume simulation cells is also calculated.
• Evolution of Morphological and Physical Properties of Laboratory Interstellar Organic Residues with Ultraviolet Irradiation

  L. Piani, S. Tachibana, T. Hama, H. Tanaka, Y. Endo, I. Sugawara, L. Dessimoulie, Y. Kimura, A. Miyake, J. Matsuno, A. Tsuchiyama, K. Fujita, S. Nakatsubo, H. Fukushi, S. Mori, T. Chigai, H. Yurimoto, A. Kouchi

  ASTROPHYSICAL JOURNAL 837 (1) 35  0004-637X 2017/03 [Refereed][Not invited]
   

  Refractory organic compounds formed in molecular clouds are among the building blocks of the solar system objects and could be the precursors of organic matter found in primitive meteorites and cometary materials. However, little is known about the evolutionary pathways of molecular cloud organics from dense molecular clouds to planetary systems. In this study, we focus on the evolution of the morphological and viscoelastic properties of molecular cloud refractory organic matter. We found that the organic residue, experimentally synthesized at similar to 10 K from UV-irradiated H2O-CH3OH-NH3 ice, changed significantly in terms of its nanometer to micrometer-scale morphology and viscoelastic properties after UV irradiation at room temperature. The dose of this irradiation was equivalent to that experienced after short residence in diffuse clouds (<= 10(4) years) or irradiation in outer protoplanetary disks. The irradiated organic residues became highly porous and more rigid and formed amorphous nanospherules. These nanospherules are morphologically similar to organic nanoglobules observed in the least-altered chondrites, chondritic porous interplanetary dust particles, and cometary samples, suggesting that irradiation of refractory organics could be a possible formation pathway for such nanoglobules. The storage modulus (elasticity) of photo-irradiated organic residues is similar to 100 MPa irrespective of vibrational frequency, a value that is lower than the storage moduli of minerals and ice. Dust grains coated with such irradiated organics would therefore stick together efficiently, but growth to larger grains might be suppressed due to an increase in aggregate brittleness caused by the strong connections between grains.
• Two types of amorphous protein particles facilitate crystal nucleation

  Tomoya Yamazaki, Yuki Kimura, Peter G. Vekilov, Erika Furukawa, Manabu Shirai, Hiroaki Matsumoto, Alexander E. S. Van Driessche, Katsuo Tsukamoto

  PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 114 (9) 2154 - 2159 0027-8424 2017/02 [Refereed][Not invited]
   

  Nucleation, the primary step in crystallization, dictates the number of crystals, the distribution of their sizes, the polymorph selection, and other crucial properties of the crystal population. We used timeresolved liquid-cell transmission electron microscopy (TEM) to perform an in situ examination of the nucleation of lysozyme crystals. Our TEM images revealed that mesoscopic clusters, which are similar to those previously assumed to consist of a dense liquid and serve as nucleation precursors, are actually amorphous solid particles (ASPs) and act only as heterogeneous nucleation sites. Crystalline phases never form inside them. We demonstrate that a crystal appears within a noncrystalline particle assembling lysozyme on an ASP or a container wall, highlighting the role of heterogeneous nucleation. These findings represent a significant departure from the existing formulation of the two-step nucleation mechanism while reaffirming the role of noncrystalline particles. The insights gained may have significant implications in areas that rely on the production of protein crystals, such as structural biology, pharmacy, and biophysics, and for the fundamental understanding of crystallization mechanisms.
• Two types of amorphous protein particles facilitate crystal nucleation

  Tomoya Yamazaki, Yuki Kimura, Peter G. Vekilov, Erika Furukawa, Manabu Shirai, Hiroaki Matsumoto, Alexander E. S. Van Driessche, Katsuo Tsukamoto

  PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 114 (9) 2154 - 2159 0027-8424 2017/02 [Refereed][Not invited]
   

  Nucleation, the primary step in crystallization, dictates the number of crystals, the distribution of their sizes, the polymorph selection, and other crucial properties of the crystal population. We used timeresolved liquid-cell transmission electron microscopy (TEM) to perform an in situ examination of the nucleation of lysozyme crystals. Our TEM images revealed that mesoscopic clusters, which are similar to those previously assumed to consist of a dense liquid and serve as nucleation precursors, are actually amorphous solid particles (ASPs) and act only as heterogeneous nucleation sites. Crystalline phases never form inside them. We demonstrate that a crystal appears within a noncrystalline particle assembling lysozyme on an ASP or a container wall, highlighting the role of heterogeneous nucleation. These findings represent a significant departure from the existing formulation of the two-step nucleation mechanism while reaffirming the role of noncrystalline particles. The insights gained may have significant implications in areas that rely on the production of protein crystals, such as structural biology, pharmacy, and biophysics, and for the fundamental understanding of crystallization mechanisms.
• In-situ observations of nucleation processes in an ionic liquid as a solvent using TEM

  Kimura Yuki

  Journal of the Japanese Association for Crystal Growth 日本結晶成長学会 44 (1) 11 - 16 2188-7268 2017 

    We believe that elucidation of the role of hydrated layer on the surface of crystals and growth units, and incorporation of significances of nanoscale materials are the keys to understand nucleation processes. We are trying to observe at the moments of nucleation in nanoscale using advanced transmission electron microscopies (TEM) for long years. Here, we report results of nucleation of sodium chlorate as an example from an ionic liquid instead of water as a solvent. Ionic liquid has negligible vapor pressure and is not charged up by electron-beam irradiation due to its relatively higher electrical conductivity and, therefore, has a great potential to study crystallization using TEM. Nevertheless, observation of nucleation processes is still very difficult even used ionic liquids. To overcome the difficulties, the nucleation processes have been expected from the results of the opposite process, i.e., by observation of dissolution processes. We successfully found the concurrent formation of two polymorphic crystals without the contribution of an amorphous intermediate stages at the equilibrium concentration.

• Microscopic observations of chromian spinel synthesized in a low temperature hydrothermal environment

  Nishikata Miu, Ohtomo Yoko, Otake Tsubasa, Kimura Yuki, Kawamoto Daisuke, Sato Tsutomu

  Abstracts of Annual Meeting of the Geochemical Society of Japan 一般社団法人日本地球化学会 64 310 - 310 2017 

• Nucleation experiments of alumina nanoparticles in vapor phase under microgravity environment

  Kimura Yuki, Ishizuka Shinnosuke, Tanaka Kyoko K, Takeuchi Shinsuke, Inatomi Yuko

  Meeting Abstracts of the Physical Society of Japan 一般社団法人 日本物理学会 72 (0) 2571 - 2571 2017 

  観測ロケットおよび航空機で得られる微小重力環境を利用し、ガス中蒸発法によりアルミナナノ粒子を作製した。干渉計や赤外分光光度計で、過飽和ガスからアルミナのナノ粒子が生成する過程をその場観察した結果について報告する。

• Evolution analysis of V2O5.nH(2)O gels for preparation of xerogels having a high specific surface area and their replicas

  Kanji Ishii, Yuki Kimura, Tomoya Yamazaki, Yuya Oaki, Hiroaki Imai

  RSC ADVANCES 7 (57) 35711 - 35716 2046-2069 2017 [Refereed][Not invited]
   

  The evolution of a V2O5.nH(2)O gel skeleton through the hydration of vanadium alkoxide was monitored using ex situ and in situ transmission electron microscopy and X-ray diffractometry. We successfully observed the morphological evolution of the gel skeleton by vacuum drying after replacing the pore liquid of acetone with cyclohexane. The gel skeleton comprised of nanofibers 10-20 nm wide and over 300 nm long was formed from ultrathin films 1-3 nm thick through thin fibrils 3-7 nm wide and about 100 nm long. Fixation of the thin fibrils by a simple vacuum-drying technique provided xerogels having a specific surface area as high as similar to 320 m(2) g(-1) at ambient temperature. Highly porous polypyrrole frameworks were obtained as replicas of the V2O5.nH(2)O xerogels.
• Pure iron grains are rare in the universe

  Yuki Kimura, Kyoko K. Tanaka, Takaya Nozawa, Shinsuke Takeuchi, Yuko Inatomi

  SCIENCE ADVANCES 3 (1) e1601992  2375-2548 2017/01 [Refereed][Not invited]
   

  The abundant forms in which the major elements in the universe exist have been determined from numerous astronomical observations and meteoritic analyses. Iron (Fe) is an exception, in that only depletion of gaseous Fe has been detected in the interstellar medium, suggesting that Fe is condensed into a solid, possibly the astronomically invisible metal. To determine the primary form of Fe, we replicated the formation of Fe grains in gaseous ejecta of evolved stars by means of microgravity experiments. We found that the sticking probability for the formation of Fe grains is extremely small; only a few atoms will stick per hundred thousand collisions so that homogeneous nucleation of metallic Fe grains is highly ineffective, even in the Fe-rich ejecta of type Ia supernovae. This implies that most Fe is locked up as grains of Fe compounds or as impurities accreted onto other grains in the interstellar medium.
• Two-Step Process in Homogeneous Nucleation of Alumina in Supersaturated Vapor

  Shinnosuke Ishizuka, Yuki Kimura, Tomoya Yamazaki, Tetsuya Hama, Naoki Watanabe, Akira Kouchi

  CHEMISTRY OF MATERIALS 28 (23) 8732 - 8741 0897-4756 2016/12 [Refereed][Not invited]
   

  Multiple pathways in crystal nucleation are now known to be more common than previously predicted; it is, therefore, crucial to understand the early stages of crystallization. Even in relatively simple vapor-phase homogeneous nucleation, the process has significant potential diversity. Here, we experimentally show crystalline Al2O3 nanoparticles forming via precisely two steps in the nucleation process from supersaturated vapor with a moderate cooling rate. In situ FT-IR measurement of nucleation allowed us to observe the formation of Al2O3 nanoparticles. Liquid-like particles first nucleated from the vapor before crystallizing. The crystalline phase was preserved by quenching without further transformation into the most stable alpha-Al2O3 polymorph. The precipitated phase changed from delta-Al2O3 for pure Al2O3 to gamma-Al2O3 or theta-Al2O3 by adding Sb or Cr, respectively. We demonstrate that a two-step process occurs in homogeneous nucleation of refractory materials from supersaturated vapor, which may facilitate polymorphic control in industry formation in space. and improve understanding of cosmic dust
• In situ FT-IR study on the homogeneous nucleation of nanoparticles of titanium oxides from highly supersaturated vapor

  Shinnosuke Ishizuka, Yuki Kimura, Tomoya Yamazaki

  JOURNAL OF CRYSTAL GROWTH 450 168 - 173 0022-0248 2016/09 [Refereed][Not invited]
   

  The formation of nanoparticles of titanium oxides by homogeneous nucleation from highly supersaturated vapors was investigated by in situ Fourier transform IR spectroscopy and by observation of the resulting nanoparticles by transmission electron microscopy (TEM). Titanium metal was thermally evaporated in a specially designed chamber under a gaseous atmosphere of oxygen and argon. Nano particles nucleated and subsequently grew as they flew freely through the oxidizing gas atmosphere. Nascent nanoparticles of titanium oxides showed a broad IR absorption band at 10-20 mu m. Subsequently, the cooled nanoparticles showed a sharp crystalline anatase feature at 12.8 mu m. TEM observations showed the formation of spherical anatase nanoparticles. The IR spectral evolution showed that the titanium oxides nucleated as metastable liquid droplets, and that crystallization proceeded through secondary nucleation from the supercooled liquid droplets. This suggests that history of the titanium oxide nanoparticles, such as the temperature and oxidation that they experience after nucleation, determines their polymorphic form. (C) 2016 Elsevier B.V. All rights reserved.
• Matrix sublimation method for the formation of high-density amorphous ice

  A. Kouchi, T. Hama, Y. Kimura, H. Hidaka, R. Escribano, N. Watanabe

  CHEMICAL PHYSICS LETTERS 658 287 - 292 0009-2614 2016/08 [Refereed][Not invited]
   

  A novel method for the formation of amorphous ice involving matrix sublimation has been developed. A CO-rich CO:H2O mixed ice was deposited at 8-10 K under ultra-high vacuum condition, which was then allowed to warm. After the sublimation of matrix CO at 35 K, amorphous ice remained. The amorphous ice formed exhibits a highly porous microscale texture; however, it also rather exhibits a density similar to that of high-density amorphous ice formed under high pressure. Furthermore, unlike conventional vapor-deposited amorphous ice, the amorphous ice is stable up to 140 K, where it transforms directly to cubic ice Ic. (C) 2016 Elsevier B.V. All rights reserved.
• Carbon and silicate dust formation in V1280 Sco

  I Sakon, S Sako, T Oanaka, T Nozawa, Y Kimura, T Fujiyoshi, T Shimonishi, F Usui, H Takahashi, R Ohsawa, A Arai, M Uemura, T Nagayama, B-C Koo, T Kozasa

  Journal of Physics: Conference Series {IOP} Publishing 728 062006  1742-6588 2016/07 [Refereed][Not invited]
  
• Assembling interferometers and in-situ observation of ambient environments and solid-liquid interfaces

  Yuki Kimura, Kenta Murayama, Tomoya Yamazaki, Takao Maki

  PROGRESS IN CRYSTAL GROWTH AND CHARACTERIZATION OF MATERIALS 62 (2) 400 - 403 0960-8974 2016/06 [Refereed][Not invited]
   

  The principle of interferometers and its applicability to our research on crystal growth can be understood through assembling interferometers. In particular, practical skills such as techniques for assembling interferometers and selecting optical components, which are not covered by general textbooks, can be learned. (C) 2016 Elsevier Ltd. All rights reserved.
• Development of compartment for studies on the growth of protein crystals in space

  T. Yamazaki, K. Tsukamoto, I. Yoshizaki, S. Fukuyama, H. Miura, T. Shimaoka, T. Maki, K. Oshi, Y. Kimura

  REVIEW OF SCIENTIFIC INSTRUMENTS 87 (3) 033107  0034-6748 2016/03 [Refereed][Not invited]
   

  To clarify the growth mechanism of a protein crystal, it is essential to measure its growth rate with respect to the supersaturation. We developed a compartment (growth cell) for measuring the growth rate (<0.1 nm s(-1)) of the face of a protein crystal at a controlled supersaturation by interferometry over a period of half a year in space. The growth cell mainly consists of quartz glass, in which the growth solution and a seed crystal are enclosed by capillaries, the screw sample holder, and a helical insert. To avoid the destruction of the cell and the evaporation of the water from the solution inside the cell, we selected the materials for these components with care. The equipment was successfully used to examine the growth of a lysozyme crystal at a controlled supersaturation in space, where convection is negligible because of the microgravity environment, thereby advancing our understanding of the mechanism of protein crystal growth from solution. The technique used to develop the growth cell is useful not only for space experiments but also for kinetic studies of materials with very slow growth and dissolution rates (<10(-3) nm s(-1)). (C) 2016 AIP Publishing LLC.
• CONCURRENT FORMATION OF CARBON AND SILICATE DUST IN NOVA V1280 SCO

  Itsuki Sakon, Shigeyuki Sako, Takashi Onaka, Takaya Nozawa, Yuki Kimura, Takuya Fujiyoshi, Takashi Shimonishi, Fumihiko Usui, Hidenori Takahashi, Ryou Ohsawa, Akira Arai, Makoto Uemura, Takahiro Nagayama, Bon-Chul Koo, Takashi Kozasa

  ASTROPHYSICAL JOURNAL 817 (2) 145  0004-637X 2016/02 [Refereed][Not invited]
   

  We present infrared multi-epoch observations of the dust-forming nova V1280 Sco over similar to 2000 days from the outburst. The temporal evolution of the infrared spectral energy distributions at 1272, 1616, and 1947 days can be explained by the emissions produced by amorphous carbon dust of mass (6.6-8.7) x 10(-8) M-circle dot with a representative grain size of 0.01. mu m and astronomical silicate dust of mass (3.4-4.3) x 10(-7) M-circle dot with a representative grain size of 0.3-0.5 mu m. Both of these dust species travel farther away from the white dwarf without apparent mass evolution throughout those later epochs. The dust formation scenario around V1280 Sco suggested from our analyses is that the amorphous carbon dust is formed in the nova ejecta followed by the formation of silicate dust either in the expanding nova ejecta or as a result of the interaction between the nova wind and the circumstellar medium.
• 21aBE-7 In-situ observation of nucleation in a solution by transmission electron microscopes

  Kimura Yuki

  Meeting Abstracts of the Physical Society of Japan 一般社団法人日本物理学会 71 2609 - 2610 2189-079X 2016
• 1D oriented attachment of calcite nanocrystals: formation of single-crystalline rods through collision

  Mihiro Takasaki, Yuki Kimura, Tomoya Yamazaki, Yuya Oaki, Hiroaki Imai

  RSC ADVANCES 6 (66) 61346 - 61350 2046-2069 2016 [Refereed][Not invited]
   

  The oriented attachment of calcite, which is a main component of biominerals, was experimentally demonstrated in an aqueous system at ambient temperatures. Calcite nanoblocks similar to 50 nm in size were prepared by carbonation of Ca(OH)(2). One-dimensional (1D) alignment of the calcite nanoblocks was induced at ambient temperatures under a basic condition (pH similar to 12), and single-crystalline rods over 1 mm were then formed through elongation in the c direction. The oriented attachment of the nanoscale building blocks was enhanced by increasing the collision frequency with stirring of the system, but was halted under a neutral pH condition with further carbonation. The controllable non-classical growth mode of calcium carbonate nano-crystals would provide significant information for biogenic and biomimetic mineralization in aqueous solutions.
• Transmission Electron Microscopy of Crystallization of Lysozyme in a Solution

  Tomoya Yamazaki, Manabu Shirai, Hiroaki Matsumoto, Yuki Kimura

  Microscopy and Microanalysis 21 (S3) 255 - 256 2015/08 [Not refereed]
  
• Pulse-laser irradiation experiments of Murchison CM2 chondrite for reproducing space weathering on C-type asteroids

  Moe Matsuoka, Tomoki Nakamura, Yuki Kimura, Takahiro Hiroi, Ryosuke Nakamura, Satoshi Okumura, Sho Sasaki

  ICARUS 254 135 - 143 0019-1035 2015/07 [Refereed][Not invited]
   

  We performed pulse-laser irradiation experiments of a primitive meteorite to simulate space weathering by micrometeorite bombardments on C-type asteroids. Pellets of powdered Murchison CM2 chondrite were set in vacuum and exposed to pulse laser with a diameter of 0.5 mm and delivered energies of 5, 10, and 15 mJ. We measured reflectance spectra of unirradiated and irradiated surfaces of the pellets. During analysis the pellet was heated to approximately 100 degrees C and purged in N-2 gas in order to reduce absorption of ambient water. The spectra become darker and bluer with increasing laser energies. Their UV reflectance increases and 0.7- and 3-mu m band depths decrease from 0 to 15 mJ. The spectral bluing observed in our experiments reproduces the bluing occurred during space weathering of C-type asteroids. High-resolution observation by a transmission electron microscope showed that the laser heating causes preferential melting and evaporation in FeS-rich fine-grained portions, which results in dispersion and deposition of numerous FeS-rich amorphous silicate particles 20-1000 nm in size on the surface of the pellet. In addition, at the laser-irradiated but unmelted areas, heat-induced amorphization and decomposition of serpentine occur. These mineralogical changes make the reflectance spectra of the Murchison CM chondrite darker and bluer. (C) 2015 Elsevier Inc. All rights reserved.
• Nanodiamond Finding in the Hyblean Shallow Mantle Xenoliths

  S. K. Simakov, A. Kouchi, N. N. Mel'nik, V. Scribano, Y. Kimura, T. Hama, N. Suzuki, H. Saito, T. Yoshizawa

  SCIENTIFIC REPORTS 5 10765  2045-2322 2015/06 [Refereed][Not invited]
   

  Most of Earth's diamonds are connected with deep-seated mantle rocks; however, in recent years, mu m-sized diamonds have been found in shallower metamorphic rocks, and the process of shallow-seated diamond formation has become a hotly debated topic. Nanodiamonds occur mainly in chondrite meteorites associated with organic matter and water. They can be synthesized in the stability field of graphite from organic compounds under hydrothermal conditions. Similar physicochemical conditions occur in serpentinite-hosted hydrothermal systems. Herein, we report the first finding of nanodiamonds, primarily of 6 and 10 nm, in Hyblean asphaltene-bearing serpentinite xenoliths (Sicily, Italy). The discovery was made by electron microscopy observations coupled with Raman spectroscopy analyses. The finding reveals new aspects of carbon speciation and diamond formation in shallow crustal settings. Nanodiamonds can grow during the hydrothermal alteration of ultramafic rocks, as well as during the lithogenesis of sediments bearing organic matter.
• IN SITU INFRARED MEASUREMENTS OF FREE-FLYING SILICATE DURING CONDENSATION IN THE LABORATORY

  Shinnosuke Ishizuka, Yuki Kimura, Itsuki Sakon

  ASTROPHYSICAL JOURNAL 803 (2) 88  0004-637X 2015/04 [Refereed][Not invited]
   

  We developed a new experimental system for infrared (IR) measurements on free-flying nucleating nanoparticles in situ and applied it to studies on silicate particles. We monitored the condensation of magnesium-bearing silicate nanoparticles from thermally evaporated magnesium and silicon monoxide vapor under an atmosphere of oxygen and argon. The IR spectrum of newly condensed particles showed a spectral feature for non-crystalline magnesium-bearing silicate that is remarkably consistent with the IR spectrum of astronomically observed non-crystalline silicate around oxygen-rich evolved stars. The silicate crystallized at <500 K and eventually developed a high crystallinity. Because of the size effects of nanoparticles, the silicate would be expected to be like a liquid at least during the initial stages of nucleation and growth. Our experimental results therefore suggest decreasing the possible formation temperature of crystalline silicates in dust formation environments with relatively higher pressure.
• Initial processes of crystallization in mesoscopic region

  Yuki Kimura, Shinnosuke Ishizuka, Kyoko Tanaka, Itsuki Sakon, Shinsuke Takeuchi, Yuko Inatomi

  Space Utilization Research 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS) 29 (29) 100 - 102 2015 [Not refereed][Not invited]
   

  Space Utilization Research (January 24-25, 2015. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)), Sagamihara, Kanagawa Japan
• Dissolution behavior of vaterite spherulite in solutions containing phosphate ions

  Yuki Sugiura, Kazuo Onuma, Masahiro Nagao, Koichi Momma, Yuki Kimura, Atsushi Yamazaki

  JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 122 (1428) 679 - 687 1882-0743 2014/08 [Refereed][Not invited]
   

  Vaterite is a crystalline polymorph of calcium carbonate that exhibits low stability in comparison with the other crystalline polymorphs of calcium carbonate. It often assumes a spherical shape. The physical properties of vaterite are utilized in advanced biomaterials such as drug delivery systems (DDSs). The potential application of vaterite in DDSs demands a comprehensive understanding of its dissolution rate as a function of PO4 concentration. Using in situ optical studies, we analyzed the dissolution behavior of vaterite in a simulated PO4-containing biogenic environment. The varying physicality (i. e., the pseudo-physiological conditions) of vaterite were investigated using high-resolution cryogenic transmission electron microscopy and small-angle X-ray scattering. In addition, we measured the PO4/Ca ratio in each part of vaterite spherulites using field-emission scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy and inductively coupled plasma atomic emission spectrometry. We categorized the vaterite spherulites into three parts - the shell, mantle, and core parts - on the basis of their dissolution behavior and PO4 response. The PO4 response to the dissolution dynamics increases toward the outer part, although the adsorption rate decreases in the presence of PO4 and PO4 fluorescence materials. The composition of the shell part was nearly identical to that of ideal vaterite, whereas the inner part exhibited a high C/Ca ratio and a poorly crystalline phase referred to as vaterite-like material. The dissolution rate of each part was 0.23-1.58nm/s (shell), 0.63-3.19nm/s (mantle), and 1.38-5.71 nm/s (core). The vaterite and vaterite-like materials were further identified according to their composition and particle size distribution. (C) 2014 The Ceramic Society of Japan. All rights reserved.
• Emergence and Amplification of Chirality via Achiral-Chiral Polymorphic Transformation in Sodium Chlorate Solution Growth

  Hiromasa Niinomi, Hitoshi Miura, Yuki Kimura, Makio Uwaha, Hiroyasu Katsuno, Shunta Harada, Toru Ujihara, Katsuo Tsukamoto

  CRYSTAL GROWTH & DESIGN 14 (7) 3596 - 3602 1528-7483 2014/07 [Refereed][Not invited]
   

  Chiral symmetry breaking during the chiral crystallization from a sodium chlorate (NaClO3) aqueous solution is an intriguing phenomenon because it provides insights into the prebiotic process of biohomochirality. However, a mechanism of the emergence and amplification of chirality remains controversial, especially for crystallization from highly supersaturated solution, and one of the hypotheses proposed before is a transition toward the homochiral state during the early stages of crystallization. In this contribution, we directly examined the early stage of crystallization by in situ polarized-light microscopy. The observation revealed that achiral crystals, which appear prior to the formation of chiral crystals, transform to the chiral crystal through two kinds of polymorphic transformations: (1) martensitic transformation (MT) and (2) solution-mediated phase transition (SMPT). The SMPT is remarkably facilitated by contact with a chiral crystal. Notably, the resulting enantiomorph through contact-facilitated SMPT is strongly directed by the contacting enantiomorph. In contrast, the MT yields two enantiomorphs in equal probability. The emergence and amplification of chirality has generally been considered to be a result of direct nucleation of a chiral crystal and its fragmentation. In contrast, our observations provide a possibility that the MT and contact-facilitated SMPT play a role for the emergence and amplification of chirality, respectively.
• Measurement of two-dimensional distribution of surface supersaturation over a sodium chlorate crystal surface using multidirectional interferometry

  Kenta Murayama, Katsuo Tsukamoto, Atul Srivastava, Hitoshi Miura, Etsuro Yokoyama, Yuki Kimura

  CRYSTAL RESEARCH AND TECHNOLOGY 49 (5) 315 - 322 0232-1300 2014/05 [Refereed][Not invited]
   

  The two-dimensional (2D) distributions of surface supersaturation of sodium chlorate crystals with and without solutal convection have been measured by means of a multidirectional interferometry (MDI) technique coupled with the principles of three-dimensional (3D) computer tomography. When solutal convection was present over a top face, the supersaturation at the center of the face was depleted by a factor of >0.9 with reference to the value at the edges of the crystal. When the convection was suppressed using an upside-down geometry, the depletion of supersaturation at the center of the face was much smaller, <0.4. Therefore, the supersaturation difference between the edges and the face center, which is responsible for the morphological stability due to volume diffusion for the solute, becomes less important compared to the effect of convection due to hydrodynamic reasons. This result should give us a key to solve why the crystal quality is sometimes better in convection-free microgravity conditions because of improved stability of a crystal face caused by more homogeneous distribution of supersaturation over the crystal surface.
• Solubility measurement of a metastable achiral crystal of sodium chlorate in solution growth

  Hiromasa Niinomi, Atsushi Horio, Shunta Harada, Toru Ujihara, Hitoshi Miura, Yuki Kimura, Katsuo Tsukamoto

  JOURNAL OF CRYSTAL GROWTH 394 106 - 111 0022-0248 2014/05 [Refereed][Not invited]
   

  The solubility of the metastable achiral monoclinic phase in NaClO3 crystallization from an aqueous solution, which appears prior to the nucleation of chiral crystals, was successfully measured in the range from 10 degrees C to 23 degrees C. Antisolvent crystallization method was used to obtain metastable crystals for the measurement. The solubility was determined to be about 1.6 times higher than that of the chiral stable cubic phase by observing growth or dissolution of the crystal in aqueous solution at the temperature and concentration of which is predetermined. (C) 2014 Elsevier B.V. All rights reserved.
• In Situ Live Observation of Nucleation and Dissolution of Sodium Chlorate Nanoparticles by Transmission Electron Microscopy

  Yuki Kimura, Hiromasa Niinomi, Katsuo Tsukamoto, Juan M. Garcia-Ruiz

  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 136 (5) 1762 - 1765 0002-7863 2014/02 [Refereed][Not invited]
   

  The formation of crystals from solution requires the initial self-assembly of units of matter into stable periodic structures reaching a critical size. The early stages of this process, called nucleation, are very difficult to visualize. Here we describe a novel method that allows real time observation of the dynamics of nucleation and dissolution of sodium chlorate clusters in an ionic liquid solution using in situ transmission electron microscopy. Using ionic liquids as solvent circumvents the problem of evaporation and charging, while the nucleation frequency was reduced by using saturated solutions. We observe simultaneous formation and dissolution of prenucleation clusters, suggesting that high-density fluctuations leading to solid cluster formation exist even under equilibrium conditions. In situ electron diffraction patterns reveal the simultaneous formation of crystalline nuclei of two polymorphic structures, the stable cubic phase and the metastable monoclinic phase, during the earliest stages of nucleation. These results demonstrate that molecules in solution can form clusters of different polymorphic phases independently of their respective solubility.
• In Situ Live Observation of Nucleation and Dissolution of Sodium Chlorate Nanoparticles by Transmission Electron Microscopy

  Yuki Kimura, Hiromasa Niinomi, Katsuo Tsukamoto, Juan M. Garcia-Ruiz

  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 136 (5) 1762 - 1765 0002-7863 2014/02 [Not refereed][Not invited]
   

  The formation of crystals from solution requires the initial self-assembly of units of matter into stable periodic structures reaching a critical size. The early stages of this process, called nucleation, are very difficult to visualize. Here we describe a novel method that allows real time observation of the dynamics of nucleation and dissolution of sodium chlorate clusters in an ionic liquid solution using in situ transmission electron microscopy. Using ionic liquids as solvent circumvents the problem of evaporation and charging, while the nucleation frequency was reduced by using saturated solutions. We observe simultaneous formation and dissolution of prenucleation clusters, suggesting that high-density fluctuations leading to solid cluster formation exist even under equilibrium conditions. In situ electron diffraction patterns reveal the simultaneous formation of crystalline nuclei of two polymorphic structures, the stable cubic phase and the metastable monoclinic phase, during the earliest stages of nucleation. These results demonstrate that molecules in solution can form clusters of different polymorphic phases independently of their respective solubility.
• Nucleation Experiment of Cosmic Dust under Microgravity using a Sounding Rocket S-520-28

  Yuki Kimura

  Int. J. Microgravity Sci. Appl. 日本マイクログラビティ応用学会 31 (3) 130 - 136 2014 [Refereed][Not invited]
   

  We performed microgravity experiments of homogeneous nucleation of iron from the vapor phase using the sounding rocket S-520-28 on December 17, 2012. The purpose is determination of a sticking probability of iron during the nucleation from the supersaturated vapor, because the sticking probability is one of the most uncertain physical quantities to understand the formation process of cosmic dust based on nucleation theories. We prepared the specially designed MachZehnder-type interferometers with an evaporation chamber and camera recording systems to fit the space and weight limitations of the rocket. Three same systems, named DUST 1 to 3, were installed into the rocket. Iron was evaporated in an argon gas and then it was cooled and nucleated to form nanoparticles. The temperature and concentration of iron vapor at the nucleation site are determined from the movement of the interference fringe. Here, we present the brief summary of the experiments and the preliminary results of the homogeneous nucleation from iron vapor under microgravity.
• S-520 Sounding Rocket Experiments of Materials Science under Microgravity

  Y. Inatomi, Y. Kimura, K. Tsukamoto, Y. Takagi, S. Takeuchi, N. Ishii

  Transactions of the Japan Society for Aeronautical and Space Sciences, Aerospace Technology Japan 12 Th_31 - Th_34 2014 [Refereed][Not invited]
  
• Achiral Metastable Crystals of Sodium Chlorate Forming Prior to Chiral Crystals in Solution Growth

  Hiromasa Niinomi, Tomoya Yamazaki, Shunta Harada, Toru Ujihara, Hitoshi Miura, Yuki Kimura, Takahiro Kuribayashi, Makio Uwaha, Katsuo Tsukamoto

  CRYSTAL GROWTH & DESIGN 13 (12) 5188 - 5192 1528-7483 2013/12 [Refereed][Not invited]
   

  Chiral symmetry breaking in NaClO3 crystallization from an aqueous solution with perturbations has been of great interest. To understand the mechanism, several models focusing on the early stage of the crystallization have been proposed. However, they are ambiguous because the early stage has been barely explored directly. Here, we investigate the early stages of the crystallization process driven by droplet evaporation using a combination of direct in situ microscopic observations and cryogenic single-crystal XRD experiments. We demonstrate that an achiral crystal having P2(1)/a symmetry, which is newly discovered for a solution growth, first appears in the droplet and then transforms into the chiral crystals. Additionally, determination of the lattice constants by XRD experiments (a = 8.42 angstrom, b = 5.26 angstrom, c = 6.70 angstrom, beta = 109.71 degrees) revealed that the achiral phase should be identical to Phase III (a = 8.78 angstrom, b = 5.17 angstrom, c = 6.83 angstrom, beta = 110 degrees), which is a high-temperature phase from a melt growth of NaClO3. We advocate further assessment of the achiral crystal and a new pathway for the formation of chiral crystals via crystalline phase transition from achiral Phase III.
• Cathodoluminescence microscopy and spectroscopy of forsterite from Kaba meteorite: An application to the study of hydrothermal alteration of parent body

  Arnold Gucsik, Taro Endo, Hirotsugu Nishido, Kiyotaka Ninagawa, Masahiro Kayama, Szaniszlo Berczi, Szabolcs Nagy, Peter Abraham, Yuki Kimura, Hitoshi Miura, Ildiko Gyollai, Irakli Simonia, Peter Rozsa, Jozsef Posta, Daniel Apai, Krisztian Mihalyi, Mihaly Nagy, Ulrich Ott

  METEORITICS & PLANETARY SCIENCE 48 (12) 2577 - 2596 1086-9379 2013/12 [Refereed][Not invited]
   

  Highly forsteritic olivine (Fo: 99.2-99.7) in the Kaba meteorite emits bright cathodoluminescence (CL). CL spectra of red luminescent forsterite grains have two broad emission bands at approximately 630nm (impurity center of divalent Mn ions) in the red region and above 700nm (trivalent Cr ions) in the red-IR region. The cores of the grains show CL blue luminescence giving a characteristic broad band emission at 400nm, also associated with minor red emissions related to Mn and Cr ions. CL color variation of Kaba forsterite is attributed to structural defects. Electron probe microanalyzer (EPMA) analysis shows concentrations of Ca, Al, and Ti in the center of the forsterite grain. The migration of diffusible ions of Mn, Cr, and Fe to the rim of the Kaba meteoritic forsterite was controlled by the hydrothermal alteration at relatively low temperature (estimated at about 250 degrees C), while Ca and Al ions might still lie in the core. A very unusual phase of FeO (wustite) was also observed, which may be a terrestrial alteration product of FeNi-metal.
• Vortex magnetic structure in framboidal magnetite reveals existence of water droplets in an ancient asteroid

  Yuki Kimura, Takeshi Sato, Norihiro Nakamura, Jun Nozawa, Tomoki Nakamura, Katsuo Tsukamoto, Kazuo Yamamoto

  Nature Communications 4 2649  2041-1723 2013/10/22 [Refereed][Not invited]
   

  The majority of water has vanished from modern meteorites, yet there remain signatures of water on ancient asteroids. How and when water disappeared from the asteroids is important, because the final fluid-concentrated chemical species played critical roles in the early evolution of organics and in the final minerals in meteorites. Here we show evidence of vestigial traces of water based on a nanometre-scale palaeomagnetic method, applying electron holography to the framboids in the Tagish Lake meteorite. The framboids are colloidal crystals composed of three-dimensionally ordered magnetite nanoparticles and therefore are only able to form against the repulsive force induced by the surface charge of the magnetite as a water droplet parches in microgravity. We demonstrate that the magnetites have a flux closure vortex structure, a unique magnetic configuration in nature that permits the formation of colloidal crystals just before exhaustion of water from a local system within a hydrous asteroid.
• MET00432: Another Tagish Lake-type Carbonaceous Chondrite from Antarctica.

  T. Nakamura, T. Noguchi, Y. Kimura, T. Hiroi, I. Ahn, J. I. Lee, S. Sasaki

  METEORITICS & PLANETARY SCIENCE 48 A258 - A258 1086-9379 2013/07 [Refereed][Not invited]
  
• Acceleration and inhibition effects of phosphate on phase transformation of amorphous calcium carbonate into vaterite

  Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Katsuo Tsukamoto, Atsushi Yamazaki

  AMERICAN MINERALOGIST 98 (1) 262 - 270 0003-004X 2013/01 [Not refereed][Not invited]
   

  Phase transformation of amorphous calcium carbonate (ACC) into vaterite and its subsequent stability was investigated at a constant pH (similar to 8.2), ionic strength, and temperature that simulated the biological environment. Solutions containing the same concentrations of CaCl2, Na2CO3, and tris(hydroxymethyl)aminomethane buffer and various concentrations of PO4 (0-62.5 mu M) were prepared, and precipitates in the solutions were sampled at a constant interval to observe the morphology and type of calcium carbonate polymorphs that appeared. The change in the Ca-ion concentration over time, which served as a guide for phase transformation of ACC into crystalline phases, was measured in relation to the PO4 concentration. The starting time of phase transformation was at the minimum point when the concentration was similar to 2-3 mu M. Vaterite spherulites consisting of needle-like crystals (0.5-2 mu m in length) formed only in this PO4 range and survived the experimental procedure (similar to 2.5 h). In contrast, the starting time of phase transformation increased exponentially with the PO4 concentration when it was higher than 5 mu M. The vaterite spherulites and calcite crystals co-precipitated, and both polymorphs grew over time. The PO4 was shown to be an accelerator for phase transformation from ACC into vaterite at low concentrations (Ca/PO4 molar ratio <3000) and an inhibitor for transformation at high concentrations. We investigated the kinetics of vaterite formation in the presence of PO4 and derived an advanced concept for cluster-based phase transformation. This investigation showed that the appearance and stability of calcium carbonate polymorphs is easily controlled by adjusting the PO4 concentration.
• Acceleration and inhibition effects of phosphate on phase transformation of amorphous calcium carbonate into vaterite

  Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Katsuo Tsukamoto, Atsushi Yamazaki

  AMERICAN MINERALOGIST 98 (1) 262 - 270 0003-004X 2013/01 [Not refereed][Not invited]
   

  Phase transformation of amorphous calcium carbonate (ACC) into vaterite and its subsequent stability was investigated at a constant pH (similar to 8.2), ionic strength, and temperature that simulated the biological environment. Solutions containing the same concentrations of CaCl2, Na2CO3, and tris(hydroxymethyl)aminomethane buffer and various concentrations of PO4 (0-62.5 mu M) were prepared, and precipitates in the solutions were sampled at a constant interval to observe the morphology and type of calcium carbonate polymorphs that appeared. The change in the Ca-ion concentration over time, which served as a guide for phase transformation of ACC into crystalline phases, was measured in relation to the PO4 concentration. The starting time of phase transformation was at the minimum point when the concentration was similar to 2-3 mu M. Vaterite spherulites consisting of needle-like crystals (0.5-2 mu m in length) formed only in this PO4 range and survived the experimental procedure (similar to 2.5 h). In contrast, the starting time of phase transformation increased exponentially with the PO4 concentration when it was higher than 5 mu M. The vaterite spherulites and calcite crystals co-precipitated, and both polymorphs grew over time. The PO4 was shown to be an accelerator for phase transformation from ACC into vaterite at low concentrations (Ca/PO4 molar ratio <3000) and an inhibitor for transformation at high concentrations. We investigated the kinetics of vaterite formation in the presence of PO4 and derived an advanced concept for cluster-based phase transformation. This investigation showed that the appearance and stability of calcium carbonate polymorphs is easily controlled by adjusting the PO4 concentration.
• THE MECHANISM OF SURFACE DIFFUSION OF H AND D ATOMS ON AMORPHOUS SOLID WATER: EXISTENCE OF VARIOUS POTENTIAL SITES

  Tetsuya Hama, Kazuaki Kuwahata, Naoki Watanabe, Akira Kouchi, Yuki Kimura, Takeshi Chigai, Valerio Pirronello

  ASTROPHYSICAL JOURNAL 757 (2) 185 - 196 0004-637X 2012/10 [Not refereed][Not invited]
   

  To understand elementary processes leading to H-2 formation, and the hydrogenation and deuteration reactions of adsorbed species on dust grains in dense clouds, we experimentally investigated the diffusion of atomic hydrogen and deuterium on amorphous solidwater (ASW) at temperatures of 8-15 K. The present study extended our previous study for selective detections of H and D atoms, and of H-2 (J = 0 and 1) and D-2 (J = 0 and 1) molecules adsorbed on ASW using both photo-stimulated desorption and resonance-enhanced multiphoton ionization, to investigate potential sites on ASW for diffusion, recombination dynamics, and the diffusion mechanism of H and D atoms. Our results demonstrate that the ASW surface contains various potential sites that can be categorized into at least three groups: very shallow, middle-, and deep-potential sites, with diffusion activation energies of <= 18, 22 (23 meV for D atoms), and >= 30 meV, respectively. The present study pictured the outline of H-2 formation on cosmic ice dust at low temperatures: H atoms landing on the dust will diffuse rapidly at the abundant shallow and middle sites on ASW, and finally become trapped at deep sites. The H atoms that arrive next recombine with such trapped H atoms to yield H-2 molecules. The small isotopic difference between the diffusion of H and D atoms on ASW indicates that the diffusion mechanism can be explained by thermal hopping, at least at middle-potential sites.
• THE MECHANISM OF SURFACE DIFFUSION OF H AND D ATOMS ON AMORPHOUS SOLID WATER: EXISTENCE OF VARIOUS POTENTIAL SITES

  HAMA TETSUYA, KUWAHATA KAZUAKI, WATANABE NAOKI, KOUCHI AKIRA, KIMURA YUKI, CHIGAI TAKESHI, PIRRONELLO VALERIO

  Astrophys J 757 (2,Pt.1) 185,1-185,12  0004-637X 2012/10/01 [Not refereed][Not invited]
  
• THE MECHANISM OF SURFACE DIFFUSION OF H AND D ATOMS ON AMORPHOUS SOLID WATER: EXISTENCE OF VARIOUS POTENTIAL SITES

  Tetsuya Hama, Kazuaki Kuwahata, Naoki Watanabe, Akira Kouchi, Yuki Kimura, Takeshi Chigai, Valerio Pirronello

  ASTROPHYSICAL JOURNAL 757 (2) 0004-637X 2012/10 [Refereed][Not invited]
   

  To understand elementary processes leading to H-2 formation, and the hydrogenation and deuteration reactions of adsorbed species on dust grains in dense clouds, we experimentally investigated the diffusion of atomic hydrogen and deuterium on amorphous solidwater (ASW) at temperatures of 8-15 K. The present study extended our previous study for selective detections of H and D atoms, and of H-2 (J = 0 and 1) and D-2 (J = 0 and 1) molecules adsorbed on ASW using both photo-stimulated desorption and resonance-enhanced multiphoton ionization, to investigate potential sites on ASW for diffusion, recombination dynamics, and the diffusion mechanism of H and D atoms. Our results demonstrate that the ASW surface contains various potential sites that can be categorized into at least three groups: very shallow, middle-, and deep-potential sites, with diffusion activation energies of <= 18, 22 (23 meV for D atoms), and >= 30 meV, respectively. The present study pictured the outline of H-2 formation on cosmic ice dust at low temperatures: H atoms landing on the dust will diffuse rapidly at the abundant shallow and middle sites on ASW, and finally become trapped at deep sites. The H atoms that arrive next recombine with such trapped H atoms to yield H-2 molecules. The small isotopic difference between the diffusion of H and D atoms on ASW indicates that the diffusion mechanism can be explained by thermal hopping, at least at middle-potential sites.
• In-situ Observation of Cosmic Dust Formation toward Microgravity Experiment

  KIMURA YUKI, INATOMI YUKO, TANAKA KYOKO, MAKI TAKAO, MIURA HITOSHI, SAKON ITSUKI, NOZAWA TAKAYA, TSUKAMOTO KATSUO

  日本結晶成長学会誌 39 (2) 68 - 74 0385-6275 2012/07 [Not refereed][Not invited]
  
• Direct Observation of the Homogeneous Nucleation of Manganese in the Vapor Phase and Determination of Surface Free Energy and Sticking Coefficient

  Y. Kimura, K. K. Tanaka, H. Miura, K. Tsukamoto

  CRYSTAL GROWTH & DESIGN 12 (6) 3278 - 3284 1528-7483 2012/06 [Not refereed][Not invited]
   

  We examined the homogeneous condensation of thermally evaporated manganese vapor in an atmosphere of argon gas and determined the temperature and concentration during homogeneous nucleation in the vapor phase by using a Mach-Zehnder type interferometer. Condensation occurred at 660-785 K below the equilibrium temperature and the degree of supersaturation was as high as similar to 5 x 10(4). Using the condensation temperature and size of the condensed particles, which were measured by transmission electron microscopy, we determined the surface free energy and sticking coefficient of Mn at 1106 +/- 50 K to be 1.55 +/- 0.10 J/m(2) and 0.39(-0.20)(+0.39) respectively, by classical nucleation theory (CNT) and 1.57 +/- 0.35 J/m(2) and 0.42(-0.21)(+0.42), respectively, by a semiphenomenological theory (SP). The nucleation theories predict that the critical nucleus contains only three and six atoms for CNT and SP, respectively, which are fewer than the number of atoms in a unit cell of Mn. This suggests that the polymorphic form of manganese is decided during particle growth rather than during nucleation from the vapor phase.
• Cathodoluminescence microcharacterization of forsterite in the chondrule experimentally grown under super cooling

  A. Gucsik, K. Tsukamoto, H. Nishido, H. Miura, M. Kayama, K. Ninagawa, Y. Kimura

  JOURNAL OF LUMINESCENCE 132 (4) 1041 - 1047 0022-2313 2012/04 [Not refereed][Not invited]
   

  Cathodoluminescence (CL) of laboratory forsterite chondrules has been characterized to clarify the formation process of chondrules and related mechanism of the crystal growth in a supercooled melt. Color CL image of the experimentally grown forsterite exhibits significant blue luminescence in the main branches of the interior structure of lab-chondrule, which reflects to the anisotropy of crystallization. A new CL band centered at 450-525 nm (2.76-2.36 eV) in blue to green region might be assigned to a microdefect-related center, which is a diagnostic peak for the forsterite that was formed due to the rapid growth as high as similar to 10 mm/s or higher from a supercooled melt. (C) 2011 Elsevier B.V. All rights reserved.
• Morphological evolution of precipitates during transformation of amorphous calcium phosphate into octacalcium phosphate in relation to role of intermediate phase

  Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto

  JOURNAL OF CRYSTAL GROWTH 332 (1) 58 - 67 0022-0248 2011/10 [Not refereed][Not invited]
   

  Nucleation of amorphous calcium phosphate (ACP) and its phase transformation with a decrease in solution pH were investigated at a constant temperature of 32 degrees C. A solution containing a mixture of CaCl2 and KH2PO4 was prepared (initial pH=7.7), and a drop was sampled at a constant interval to observe the morphological evolution of the precipitates that formed in the solution. A gel-like solution structure formed immediately after mixing and contained a small amount of sea-urchin-like ACP spherulites (3-20 mu m in size). These spherulites consisted of 1.5-10-mu m-long flexible needles that formed simultaneously with numerous ACP spherical particles. They first transformed into beta-tri calcium phosphate-like material (called "pseudo beta-TCP") and then into single crystals of octacalcium phosphate (OCP) without dissolution. The flexible needles in the spherulites changed into blade springs, then into flexible plates, and finally into rigid plates during the transformation. The OCP structure appeared in the pseudo beta-TCP plates and gradually substituted for the beta-TCP structure over time. The macroscopic spherulite morphology of the initial ACP remained unchanged during the phase transformation, suggesting that OCP is a pseudomorph of ACP. This feature was observed only when the ACP spherulites formed in the initial solution. Fiber-like aggregates consisting of beta-TCP single crystals nucleated around the ACP spherical particles and grew over time. They survived until the final stage of the reaction, and OCP polycrystals formed in the mixture of beta-TCP and ACP spheres. The OCP polycrystals gradually substituted for the ACP spheres without phase transformation of beta-TCP into OCP. (C) 2011 Elsevier B.V. All rights reserved.
• Morphological evolution of precipitates during transformation of amorphous calcium phosphate into octacalcium phosphate in relation to role of intermediate phase

  Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto

  JOURNAL OF CRYSTAL GROWTH 332 (1) 58 - 67 0022-0248 2011/10 [Not refereed][Not invited]
   

  Nucleation of amorphous calcium phosphate (ACP) and its phase transformation with a decrease in solution pH were investigated at a constant temperature of 32 degrees C. A solution containing a mixture of CaCl2 and KH2PO4 was prepared (initial pH=7.7), and a drop was sampled at a constant interval to observe the morphological evolution of the precipitates that formed in the solution. A gel-like solution structure formed immediately after mixing and contained a small amount of sea-urchin-like ACP spherulites (3-20 mu m in size). These spherulites consisted of 1.5-10-mu m-long flexible needles that formed simultaneously with numerous ACP spherical particles. They first transformed into beta-tri calcium phosphate-like material (called "pseudo beta-TCP") and then into single crystals of octacalcium phosphate (OCP) without dissolution. The flexible needles in the spherulites changed into blade springs, then into flexible plates, and finally into rigid plates during the transformation. The OCP structure appeared in the pseudo beta-TCP plates and gradually substituted for the beta-TCP structure over time. The macroscopic spherulite morphology of the initial ACP remained unchanged during the phase transformation, suggesting that OCP is a pseudomorph of ACP. This feature was observed only when the ACP spherulites formed in the initial solution. Fiber-like aggregates consisting of beta-TCP single crystals nucleated around the ACP spherical particles and grew over time. They survived until the final stage of the reaction, and OCP polycrystals formed in the mixture of beta-TCP and ACP spheres. The OCP polycrystals gradually substituted for the ACP spheres without phase transformation of beta-TCP into OCP. (C) 2011 Elsevier B.V. All rights reserved.
• AGREEMENT OF EXPERIMENT AND THEORY IN HOMOGENEOUS NUCLEATION

  Y. Kimura, K. K. Tanaka, H. Miura, K. Tsukamoto

  METEORITICS & PLANETARY SCIENCE 46 A124 - A124 1086-9379 2011/07 [Refereed][Not invited]
  
• Magnetite 3D Colloidal Crystals Formed in the Early Solar System 4.6 Billion Years Ago

  Jun Nozawa, Katsuo Tsukamoto, Willem van Enckevort, Tomoki Nakamura, Yuki Kimura, Hitoshi Miura, Hisao Satoh, Ken Nagashima, Makoto Konoto

  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 133 (23) 8782 - 8785 0002-7863 2011/06 [Refereed][Not invited]
   

  Three-dimensional colloidal crystals made of ferromagnetic particles, such as magnetite (Fe(3)O(4)), cannot be synthesized in principle because of the strong attractive magnetic interaction. However, we discovered colloidal crystals composed of polyhedral magnetite nanocrystallites of uniform size in the range of a few hundred nanometers in the Tagish Lake meteorite. Those colloidal crystals were formed 4.6 billion years ago and thus are much older than natural colloidal crystals on earth, such as opals, which formed about 100 million years ago.(1) We found that the size of each individual magnetite particle determines its morphology, which in turn plays an important role in deciding the packing structure of the colloidal crystals. We also hypothesize that each particle has a flux-closed magnetic domain structure, which reduces the interparticle magnetic force significantly.
• Magnetite 3D Colloidal Crystals Formed in the Early Solar System 4.6 Billion Years Ago

  Jun Nozawa, Katsuo Tsukamoto, Willem van Enckevort, Tomoki Nakamura, Yuki Kimura, Hitoshi Miura, Hisao Satoh, Ken Nagashima, Makoto Konoto

  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 133 (23) 8782 - 8785 0002-7863 2011/06 [Not refereed][Not invited]
   

  Three-dimensional colloidal crystals made of ferromagnetic particles, such as magnetite (Fe(3)O(4)), cannot be synthesized in principle because of the strong attractive magnetic interaction. However, we discovered colloidal crystals composed of polyhedral magnetite nanocrystallites of uniform size in the range of a few hundred nanometers in the Tagish Lake meteorite. Those colloidal crystals were formed 4.6 billion years ago and thus are much older than natural colloidal crystals on earth, such as opals, which formed about 100 million years ago.(1) We found that the size of each individual magnetite particle determines its morphology, which in turn plays an important role in deciding the packing structure of the colloidal crystals. We also hypothesize that each particle has a flux-closed magnetic domain structure, which reduces the interparticle magnetic force significantly.
• Magnetite 3D Colloidal Crystals Formed in the Early Solar System 4.6 Billion Years Ago

  Jun Nozawa, Katsuo Tsukamoto, Willem van Enckevort, Tomoki Nakamura, Yuki Kimura, Hitoshi Miura, Hisao Satoh, Ken Nagashima, Makoto Konoto

  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 133 (23) 8782 - 8785 0002-7863 2011/06 [Not refereed][Not invited]
   

  Three-dimensional colloidal crystals made of ferromagnetic particles, such as magnetite (Fe(3)O(4)), cannot be synthesized in principle because of the strong attractive magnetic interaction. However, we discovered colloidal crystals composed of polyhedral magnetite nanocrystallites of uniform size in the range of a few hundred nanometers in the Tagish Lake meteorite. Those colloidal crystals were formed 4.6 billion years ago and thus are much older than natural colloidal crystals on earth, such as opals, which formed about 100 million years ago.(1) We found that the size of each individual magnetite particle determines its morphology, which in turn plays an important role in deciding the packing structure of the colloidal crystals. We also hypothesize that each particle has a flux-closed magnetic domain structure, which reduces the interparticle magnetic force significantly.
• Interferometric in-situ observation during nucleation and growth of WO3 nanocrystals in vapor phase

  Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto, Chaorong Li, Takao Maki

  JOURNAL OF CRYSTAL GROWTH 316 (1) 196 - 200 0022-0248 2011/02 [Not refereed][Not invited]
   

  To investigate the homogeneous nucleation and growth process of nanoparticles in vapor phase, interferometric observation was attempted for the first time to the gas evaporation method, which has been a commonly accepted physical production method of nanoparticles. Tungsten oxide was evaporated by electrical heating of a tungsten wire in a mixture gas of Ar and O-2. WO3 nanoparticles were formed via homogeneous nucleation and growth during a gas cools following a thermal convection produced by the evaporation source. The degree of supersaturation for nucleation was extremely high, 6.6 x 10(6), which was determined from the interferogram. Surface free energy of WO3 at 1100 K was calculated based on the classical nucleation theory and was 1.38 x 10(3) erg cm(-2), which is within the reported values. A part of the difference between actual formation rate of produced nanoparticles, which were determined based on a transmission electron microscope, and calculated values based on the classical nucleation theory were well explained if we adopt the idea of coalescence growth. (C) 2011 Elsevier B.V. All rights reserved.
• Interferometric in-situ observation during nucleation and growth of WO3 nanocrystals in vapor phase

  Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto, Chaorong Li, Takao Maki

  JOURNAL OF CRYSTAL GROWTH 316 (1) 196 - 200 0022-0248 2011/02 [Not refereed][Not invited]
   

  To investigate the homogeneous nucleation and growth process of nanoparticles in vapor phase, interferometric observation was attempted for the first time to the gas evaporation method, which has been a commonly accepted physical production method of nanoparticles. Tungsten oxide was evaporated by electrical heating of a tungsten wire in a mixture gas of Ar and O-2. WO3 nanoparticles were formed via homogeneous nucleation and growth during a gas cools following a thermal convection produced by the evaporation source. The degree of supersaturation for nucleation was extremely high, 6.6 x 10(6), which was determined from the interferogram. Surface free energy of WO3 at 1100 K was calculated based on the classical nucleation theory and was 1.38 x 10(3) erg cm(-2), which is within the reported values. A part of the difference between actual formation rate of produced nanoparticles, which were determined based on a transmission electron microscope, and calculated values based on the classical nucleation theory were well explained if we adopt the idea of coalescence growth. (C) 2011 Elsevier B.V. All rights reserved.
• Synthesis of Stacked-Cup Carbon Nanotubes in a Metal Free Low Temperature System

  Yuki Kimura, Joseph A. Nuth, Natasha M. Johnson, Kevin D. Farmer, Kenneth P. Roberts, Syed R. Hussaini

  NANOSCIENCE AND NANOTECHNOLOGY LETTERS 3 (1) 4 - 10 1941-4900 2011/02 [Refereed][Not invited]
   

  Stacked-cup carbon nanotubes were formed by either Fischer-Tropsch type or Haber-Bosch type reactions in a metal free system. Graphite particles were used as the catalyst. The samples were heated at 600 degrees C in a gas mixture of CO 75 Torr, N-2 75 Torr and H-2 550 Torr for three days. Transmission electron microscope analysis of the catalyst surface at the completion of the experiment recognized the growth of nanotubes. They were 10-50 nm in diameter and similar to 1 mu m in length. They had a hollow channel of 5-20 nm in the center. The nanotubes may have grown on graphite surfaces by the CO disproportionation reaction and the surface tension of the carbon nucleus may have determined the diameter. Although, generally, the diameter of a carbon nanotube depends on the size of the catalytic particles, the diameter of the nanotubes on graphite particles was independent of the particle size and significantly confined within a narrow range compared with that produced using catalytic amorphous iron-silicate nanoparticles. Therefore, they must have an unknown formation process that is different than the generally accepted mechanism.
• Laboratory annealing experiments of refractory silicate grain analogs using differential scanning calorimetry

  Yuki Kimura, Joseph A. Nuth, Katsuo Tsukamoto, Chihiro Kaito

  METEORITICS & PLANETARY SCIENCE 46 (1) 92 - 102 1086-9379 2011/01 [Not refereed][Not invited]
   

  Exothermic reactions during the annealing of laboratory synthesized amorphous magnesium-bearing silicate particles used as grain analogs of cosmic dust were detected by differential scanning calorimetry (DSC) in air. With infrared spectroscopy and transmission electron microscopy, we show that cosmic dust could possibly undergo fusion to larger particles, with oxidation of magnesium silicide and crystallization of forsterite as exothermic reactions in the early solar system. The reactions begin at approximately 425, approximately 625, and approximately 1000 K, respectively, and the reaction energies (enthalpies) are at least 727, 4151, and 160.22 J g-1, respectively. During the crystallization of forsterite particles, the spectral evolution of the 10 mu m feature from amorphous to crystalline was observed to begin at lower temperature than the crystallization temperature of 1003 K. During spectral evolution at lower temperature, nucleation and/or the formation of nanocrystallites of forsterite at the surface of the grain analogs was observed.
• Interferometric observation of temperature distributions in the smoke experiment

  Y. Kimura, K. Tsukamoto

  J. Jpn. Soc. Microgravity Appl 2011 [Not refereed][Not invited]
  
• Laboratory annealing experiments of refractory silicate grain analogs using differential scanning calorimetry

  Yuki Kimura, Joseph A. Nuth, Katsuo Tsukamoto, Chihiro Kaito

  METEORITICS & PLANETARY SCIENCE 46 (1) 92 - 102 1086-9379 2011/01 [Not refereed][Not invited]
   

  Exothermic reactions during the annealing of laboratory synthesized amorphous magnesium-bearing silicate particles used as grain analogs of cosmic dust were detected by differential scanning calorimetry (DSC) in air. With infrared spectroscopy and transmission electron microscopy, we show that cosmic dust could possibly undergo fusion to larger particles, with oxidation of magnesium silicide and crystallization of forsterite as exothermic reactions in the early solar system. The reactions begin at approximately 425, approximately 625, and approximately 1000 K, respectively, and the reaction energies (enthalpies) are at least 727, 4151, and 160.22 J g-1, respectively. During the crystallization of forsterite particles, the spectral evolution of the 10 mu m feature from amorphous to crystalline was observed to begin at lower temperature than the crystallization temperature of 1003 K. During spectral evolution at lower temperature, nucleation and/or the formation of nanocrystallites of forsterite at the surface of the grain analogs was observed.
• Laboratory annealing experiments of refractory silicate grain analogs using differential scanning calorimetry

  Yuki Kimura, Joseph A. Nuth, Katsuo Tsukamoto, Chihiro Kaito

  METEORITICS & PLANETARY SCIENCE 46 (1) 92 - 102 1086-9379 2011/01 [Refereed][Not invited]
   

  Exothermic reactions during the annealing of laboratory synthesized amorphous magnesium-bearing silicate particles used as grain analogs of cosmic dust were detected by differential scanning calorimetry (DSC) in air. With infrared spectroscopy and transmission electron microscopy, we show that cosmic dust could possibly undergo fusion to larger particles, with oxidation of magnesium silicide and crystallization of forsterite as exothermic reactions in the early solar system. The reactions begin at approximately 425, approximately 625, and approximately 1000 K, respectively, and the reaction energies (enthalpies) are at least 727, 4151, and 160.22 J g-1, respectively. During the crystallization of forsterite particles, the spectral evolution of the 10 mu m feature from amorphous to crystalline was observed to begin at lower temperature than the crystallization temperature of 1003 K. During spectral evolution at lower temperature, nucleation and/or the formation of nanocrystallites of forsterite at the surface of the grain analogs was observed.
• DIRECT MEASUREMENTS OF HYDROGEN ATOM DIFFUSION AND THE SPIN TEMPERATURE OF NASCENT H2 MOLECULE ON AMORPHOUS SOLID WATER

  WATANABE NAOKI, KIMURA YUKI, KOUCHI AKIRA, CHIGAI TAKESHI, HAMA TETSUYA, PIRRONELLO VALERIO

  Astrophys J 714 (2,Pt.2) L233-L237  0004-637X 2010/05/10 [Not refereed][Not invited]
  
• Physicochemical processes of atomic hydrogen on amorphous solid water at very low temperatures

  Naoki Watanabe, Akira Kouchi, Hiroshi Hidaka, Yuki Kimura, Tetsuya Hama

  ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 239 0065-7727 2010/03 [Refereed][Not invited]
  
• THE FORMATION OF GRAPHITE WHISKERS IN THE PRIMITIVE SOLAR NEBULA

  Joseph A. Nuth, Yuki Kimura, Christopher Lucas, Frank Ferguson, Natasha M. Johnson

  ASTROPHYSICAL JOURNAL LETTERS 710 (1) L98 - L101 2010/02 [Not refereed][Not invited]
   

  It has been suggested that carbonaceous grains are efficiently destroyed in the interstellar medium and must either reform in situ at very low pressures and temperatures or in an alternative environment more conducive to grain growth. Graphite whiskers have been discovered associated with high-temperature phases in meteorites such as calcium aluminum inclusions and chondrules, and it has been suggested that the expulsion of such material from protostellar nebulae could significantly affect the optical properties of the average interstellar grain population. We have experimentally studied the potential for Fischer-Tropsch and Haber-Bosch type reactions to produce organic materials in protostellar systems from the abundant H(2), CO, and N(2) reacting on the surfaces of available silicate grains. When graphite grains are repeatedly exposed to H(2), CO, and N(2) at 875 K abundant graphite whiskers are observed to form on or from the surfaces of the graphite grains. In a dense, turbulent nebula, such extended whiskers are very likely to be broken off, and fragments could be ejected either in polar jets or by photon pressure after transport to the outer reaches of the nebula.
• THE FORMATION OF GRAPHITE WHISKERS IN THE PRIMITIVE SOLAR NEBULA

  Joseph A. Nuth, Yuki Kimura, Christopher Lucas, Frank Ferguson, Natasha M. Johnson

  ASTROPHYSICAL JOURNAL LETTERS 710 (1) L98 - L101 0004-637X 2010/02 [Not refereed][Not invited]
   

  It has been suggested that carbonaceous grains are efficiently destroyed in the interstellar medium and must either reform in situ at very low pressures and temperatures or in an alternative environment more conducive to grain growth. Graphite whiskers have been discovered associated with high-temperature phases in meteorites such as calcium aluminum inclusions and chondrules, and it has been suggested that the expulsion of such material from protostellar nebulae could significantly affect the optical properties of the average interstellar grain population. We have experimentally studied the potential for Fischer-Tropsch and Haber-Bosch type reactions to produce organic materials in protostellar systems from the abundant H(2), CO, and N(2) reacting on the surfaces of available silicate grains. When graphite grains are repeatedly exposed to H(2), CO, and N(2) at 875 K abundant graphite whiskers are observed to form on or from the surfaces of the graphite grains. In a dense, turbulent nebula, such extended whiskers are very likely to be broken off, and fragments could be ejected either in polar jets or by photon pressure after transport to the outer reaches of the nebula.
• Formation of polycyclic aromatic hydrocarbon grains using anthracene and their stability under UV irradiation

  Midori Saito, Itsuki Sakon, Chihiro Kaito, Yuki Kimura

  EARTH PLANETS AND SPACE 62 (1) 81 - 90 1343-8832 2010 [Not refereed][Not invited]
   

  It has been known for sonic time that the properties of a material are changed in nanometer size. Since it is nontrivial that polycyclic aromatic hydrocarbon (PAH) grains at the nanometer scale show similar properties with that of macroscopic scale, PAH grains were synthesized by a gas evaporation method and were analyzed using a transmission electron microscope and their UV-Vis and mid-IR spectra were Measured. Results from these experiments showed that condensed anthracene grains from the gas phase had a planar form and showed similar infrared peaks compared to anthracene molecules, but With somewhat wider bands and different relative intensities. Sonic new features were also observed. The anthracene molecules formed photodimer ill their grain and showed different infrared features after UV irradiation. This Would be the first report concerning nanometer-sized PAH grains.
• Direct measurements of hydrogen atom diffusion and the spin temperature of nascent H2 molecule on amorphous solid water

  N. Watanabe, Y. Kimura, A. Kouchi, T. Chigai, T. Hama, V. Pirronello

  The Astrophysical Journal Letters 714 L233-L237  2010 [Not refereed][Not invited]
  
• Synthesis of stacked-cup carbon nanotubes in a metal free low temperature system

  Y. Kimura, J. A. Nuth III, N. M. Johnson, K. D. Farmer, K. P. Roberts, S. R. Hussaini

  Nanoscience and Nanotechnology Letters 3 1 - 7 2010 [Not refereed][Not invited]
  
• Formation of polycyclic aromatic hydrocarbon grains using anthracene and their stability under UV irradiation

  Midori Saito, Itsuki Sakon, Chihiro Kaito, Yuki Kimura

  EARTH PLANETS AND SPACE 62 (1) 81 - 90 1343-8832 2010 [Not refereed][Not invited]
   

  It has been known for sonic time that the properties of a material are changed in nanometer size. Since it is nontrivial that polycyclic aromatic hydrocarbon (PAH) grains at the nanometer scale show similar properties with that of macroscopic scale, PAH grains were synthesized by a gas evaporation method and were analyzed using a transmission electron microscope and their UV-Vis and mid-IR spectra were Measured. Results from these experiments showed that condensed anthracene grains from the gas phase had a planar form and showed similar infrared peaks compared to anthracene molecules, but With somewhat wider bands and different relative intensities. Sonic new features were also observed. The anthracene molecules formed photodimer ill their grain and showed different infrared features after UV irradiation. This Would be the first report concerning nanometer-sized PAH grains.
• AFM study on surface nanotopography of matrix olivines in Allende carbonaceous chondrite

  Jun Nozawa, Katsuo Tsukamoto, Hidekazu Kobatake, Junya Yamada, Hisao Satoh, Ken Nagashima, Hitoshi Miura, Yuki Kimura

  ICARUS 204 (2) 681 - 686 0019-1035 2009/12 [Not refereed][Not invited]
   

  By means of nanoscale surface observation, we have proposed a new approach for investigating fine crystals of cosmic materials to reveal their origin and growth conditions. Several different morphologies of polyhedral fine olivines with faceted faces have been found in Allende carbonaceous chondrite (4.5 byr in geochronological age). In the present work, molecular level topography of the faceted matrix olivine by Atomic Force Microscopy (AFM) has Successfully been performed, The matrix olivine found to have preserved growth step pattern on its surface even though quite long time has passed since they formed in the early Solar System. The Surface pattern Suggests that the faceted matrix olivine could have been condensed from the gas phase, and possibly that these olivine crystals had continued to grow under a rapid cooling condition (0.1-1 K s(-1)). The estimated cooling rate agrees well with predictions based on hypothetical rapid heating and cooling events such as shock wave heating. (C) 2009 Elsevier Inc. All rights reserved.
• ORIGIN OF ORGANIC GLOBULES IN METEORITES: LABORATORY SIMULATION USING AROMATIC HYDROCARBONS

  Midori Saito, Yuki Kimura

  ASTROPHYSICAL JOURNAL LETTERS 703 (2) L147 - L151 2009/10 [Not refereed][Not invited]
   

  Analogs of organic hollow globules, which have been found in carbonaceous chondrite meteorites and interplanetary dust particles, were synthesized in our laboratory from benzene and anthracene using plasma. Our results suggest that organic globules could be made from aromatic rings in circumstellar envelopes around evolved stars. The hollow interior could be formed by coagulation of vacancies, formed by electronic excitation and/or knock-out of carbon atoms following irradiation by plasma particles such as protons and He(+) ions. This experimental result suggests that organic globules are possibly the final products in the evolution of carbonaceous matter from acetylene and benzene to polycyclic aromatic hydrocarbons in ejecta gas from evolved stars.
• A SEED OF SOLAR FORSTERITE AND POSSIBLE NEW EVOLUTIONAL SCENARIO OF COSMIC SILICATES

  Yuki Kimura, Joseph A. Nuth

  ASTROPHYSICAL JOURNAL LETTERS 697 (1) L10 - L13 2009/05 [Refereed][Not invited]
   

  Laboratory experiments suggest that magnesium silicide (Mg(2)Si) grains could be produced in the hydrogen dominant gas outflow from evolved stars in addition to amorphous oxide minerals. If the magnesium silicide grains were incorporated into the primitive solar nebula, the magnesium silicide would easily become forsterite (Mg(2)SiO(4)) by oxidation as it reacted with the relatively oxygen-rich, solar composition gas. This hypothesis can explain the existence of abundant forsterite grains with solar oxygen composition in meteorites, i.e., magnesium silicide could be the precursor of much of the forsterite found in our solar system. In addition, if a significant fraction of the solar forsterite is derived from magnesium silicide, it could explain the apparent low abundance of presolar forsterite. Furthermore, the lower degree of crystallinity observed in silicates formed in outflows of lower mass-loss-rate stars might be caused by the formation of magnesium silicide in this relatively hydrogen-rich environment.
• 材料あれこれ〔その他〕 46億年昔の宇宙空間での結晶化

  木村勇気, 三浦均, 塚本勝男

  日本マイクログラビティ応用学会誌 日本マイクログラビティ応用学会 26 (2) 139 - 143 0915-3616 2009/04/30 [Not refereed][Not invited]
  
• 46億年昔の宇宙空間での結晶化

  木村勇気, 三浦均, 塚本勝男

  日本マイクログラビティ応用学会誌 2009 [Not refereed][Not invited]
  
• Origin of organic globules in meteorites: Laboratory simulation using aromatic hydrocarbons

  Midori Saito, Yuki Kimura

  Astrophysical Journal 703 (2) L147 - L151 1538-4357 2009 [Not refereed][Not invited]
   

  Analogs of organic hollow globules, which have been found in carbonaceous chondrite meteorites and interplanetary dust particles, were synthesized in our laboratory from benzene and anthracene using plasma. Our results suggest that organic globules could be made from aromatic rings in circumstellar envelopes around evolved stars. The hollow interior could be formed by coagulation of vacancies, formed by electronic excitation and/or knock-out of carbon atoms following irradiation by plasma particles such as protons and He+ ions. This experimental result suggests that organic globules are possibly the final products in the evolution of carbonaceous matter from acetylene and benzene to polycyclic aromatic hydrocarbons in ejecta gas from evolved stars. © 2009. The American Astronomical Society.
• Properties of Circumstellar PAHs in Various Radiation Environments

  Itsuki Sakon, Takashi Onaka, Yasuhiro Takahashi, Hidehiro Kaneda, Yuki Kimura, Midori Saito, In-Ok Song, Yoshiko Okamoto, Hirokazu Kataza, Takuya Yamashita, Takuya Fujiyoshi

  EXOPLANETS AND DISKS: THEIR FORMATION AND DIVERSITY 1158 153 - + 0094-243X 2009 

  A series of emission bands in the mid-infrared, mainly at 3.3, 6.2, 7.6-7.8, 8.6 and 11.2 mu m, have been ubiquitously observed in various astrophysical environments. They are originally termed unidentified infrared (UIR) bands and many previous studies based on laboratory experiments and theoretical quantum chemical calculations have lead us to the general consensus that the carriers of these features are carbonaceous materials, including polycyclic aromatic hydrocarbons (PAHs). The relative band strengths, the profiles and the peak positions of these features are expected to vary according to the different physical conditions of the carriers. Recent observational studies have revealed the variations in the spectral properties of the UIR bands among sources with different stellar spectral types. In this proceedings we plan to give a brief introduction of our latest observational studies on the properties and the spatial distribution of the UIR bands in several objects, including both the early-type (O5--O6) and the late-type (K2) stars based on observations with Cooled Mid-Infrared Camera and Spectrometer (COMICS) on board Subaru telescope.
• Experimental demonstration of condensation of Mg-bearing silicate grains around evolved stars

  Y. Kimura, S. Sasaki, H. Suzuki, A. Kumamoto, M. Saito, C. Kaito

  ASTROPHYSICAL JOURNAL 684 (2) 1496 - 1501 0004-637X 2008/09 [Not refereed][Not invited]
   

  Mg-bearing silicate grains were produced directly from the vapor phase from magnesium and silicon oxide in a mixed atmosphere of Ar and O-2 in the laboratory. It was found that the crystallinity, which was deduced from the shape of the 10 mu m feature, of the grains depends on the ratio of magnesium to silicon oxide in the vapor phase. When the Mg/SiOx ratio was high, crystalline forsterite grains were produced owing to annealing of the silicate accompanied by large exothermic energy due to the oxidation of magnesium. The experimental result suggests that the crystallinity of circumstellar silicates could be determined by the balance between heat generation by magnesium oxidation and heat dissipation due to radiation. In this situation, later annealing of the silicate fraction or the use of a warm substrate for condensation of crystalline silicate is unnecessary. Crystalline silicates found in young stars are also able to be produced following our hypothesis after simultaneous evaporation of silicates and ices during energetic shocks in protostellar nebulae.
• Morphological alteration and structure of ZnO particles produced in electric field

  Chihiro Kaito, Yasuhiko Kinuta, Hitoshi Suzuki, Syunsuke Adachi, Akihito Kumamoto, Yoshio Saito, Yuki Kimura

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 (9) 094708-1-094708-4  0031-9015 2008/09 [Not refereed][Not invited]
   

  The apparent morphological difference between ZnO particles with and without an electric field applied during the growth process was elucidated by high-resolution transmission electron microscopy. The ZnO smoke produced immediately below the electric field by burning zinc in a gas mixture of O-2, and Ar, curved towards a negative plate. The typical tetrapod- or needle-shaped ZnO particles were seldom observed in the electric field; spherical particles were predominantly produced. Some of these spherical particles were composed of multiply twinned particles with an antiphase boundary. The growth of these multiply twinned particles was due to an increment in the ionicity in the crystallographic polar direction of ZnO bonding induced by the applied electric field.
• Morphological alteration and structure of ZnO particles produced in electric field

  Chihiro Kaito, Yasuhiko Kinuta, Hitoshi Suzuki, Syunsuke Adachi, Akihito Kumamoto, Yoshio Saito, Yuki Kimura

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 (9) 094708.1-094708.4  0031-9015 2008/09 [Not refereed][Not invited]
   

  The apparent morphological difference between ZnO particles with and without an electric field applied during the growth process was elucidated by high-resolution transmission electron microscopy. The ZnO smoke produced immediately below the electric field by burning zinc in a gas mixture of O-2, and Ar, curved towards a negative plate. The typical tetrapod- or needle-shaped ZnO particles were seldom observed in the electric field; spherical particles were predominantly produced. Some of these spherical particles were composed of multiply twinned particles with an antiphase boundary. The growth of these multiply twinned particles was due to an increment in the ionicity in the crystallographic polar direction of ZnO bonding induced by the applied electric field.
• POSSIBLE DRIVING FORCE BEHIND FORMATION OF COSMIC CARBYNE CRYSTALS

  Yuki Kimura, Chihiro Kaito

  ASTROPHYSICAL JOURNAL LETTERS 685 (1) L83 - L86 2008/09 [Refereed][Not invited]
   

  Regarding the formation of cosmic dust, condensation and thermal alteration have been considered as clues to the formation mechanism and environments experienced by dust. Unfortunately, however, the formation mechanisms of many types of dust found in meteorites are still unidentified. Carbyne crystals found in carbonaceous meteorites are also one type of enigmatic mineral dust. We show a new route for the formation of cosmic carbyne crystals via synchrotron radiation as a more favorable driving force than condensation from hot gas. Carbyne crystals were produced under a coronal photon flux corresponding to 32 days at a heliocentric distance of 5 AU, which corresponds to the orbit of Jupiter, with respect to the young Sun. The novel method of synthesizing carbyne crystals will be useful for understanding the material evolution of carbonaceous dust.
• Morphological alteration and structure of ZnO particles produced in electric field

  Chihiro Kaito, Yasuhiko Kinuta, Hitoshi Suzuki, Syunsuke Adachi, Akihito Kumamoto, Yoshio Saito, Yuki Kimura

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 (9) 0031-9015 2008/09 [Refereed][Not invited]
   

  The apparent morphological difference between ZnO particles with and without an electric field applied during the growth process was elucidated by high-resolution transmission electron microscopy. The ZnO smoke produced immediately below the electric field by burning zinc in a gas mixture of O-2, and Ar, curved towards a negative plate. The typical tetrapod- or needle-shaped ZnO particles were seldom observed in the electric field; spherical particles were predominantly produced. Some of these spherical particles were composed of multiply twinned particles with an antiphase boundary. The growth of these multiply twinned particles was due to an increment in the ionicity in the crystallographic polar direction of ZnO bonding induced by the applied electric field.
• Direct observation of MoO(2) crystal growth from amorphous MoO(3) film

  Kenji Nina, Yuki Kimura, Kaorl Yokoyama, Osamu Kido, Gong Binyo, Chihiro Kaito

  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 40 (9) 2995 - 2998 1386-9477 2008/08 [Not refereed][Not invited]
   

  The formation process of MoO(2) crystal from amorphous MoO(3) film has been imaged by in situ observation with a transmission electron microscope. Selective growth of flower-shaped MoO(2) crystals by heating above 673 K in vacuum was directly observed. Since the MoO(2) crystal has metallic conductivity of the order of indium oxide film containing tin (ITO film), the thin film growth of the MoO(2) phase has been discussed on the basis of a new substitute for ITO film. (C) 2008 Elsevier B.V. All rights reserved.
• Structural Alterations of Carbon Particles in Saturated Water Vapor

  Chihiro Kaito, Masayuki Shintaku, Ryuta Sakao, Akihito Kumamoto, Midori Saito, Yuki Kimura, Shinsuke Ohyagi, Shigeru Morikawa, Hiroshi Suzuki

  JAPANESE JOURNAL OF APPLIED PHYSICS 47 (8) 6588 - 6591 0021-4922 2008/08 [Not refereed][Not invited]
   

  High-resolution transmission electron microscopy (HRTEM) of carbon particles has been carried out at 80 degrees C in saturated water vapor, to evaluate any structural alterations. Amorphous particles or microcrystallites of carbon based on the graphitic structure were altered to more stable graphitic structures such as ribbons or onion-like structures. The stable graphitic structure was altered again to the amorphous structure. Results are interpreted in terms of the oxidation of carbon particles in air. The differences in alterations among carbon particles, Pt clusters on carbon particles, and Pt clusters in carbon particles are presented on the basis of HRTEM images.
• Structural Alterations of Carbon Particles in Saturated Water Vapor

  Chihiro Kaito, Masayuki Shintaku, Ryuta Sakao, Akihito Kumamoto, Midori Saito, Yuki Kimura, Shinsuke Ohyagi, Shigeru Morikawa, Hiroshi Suzuki

  JAPANESE JOURNAL OF APPLIED PHYSICS 47 (8) 6588 - 6591 0021-4922 2008/08 [Not refereed][Not invited]
   

  High-resolution transmission electron microscopy (HRTEM) of carbon particles has been carried out at 80 degrees C in saturated water vapor, to evaluate any structural alterations. Amorphous particles or microcrystallites of carbon based on the graphitic structure were altered to more stable graphitic structures such as ribbons or onion-like structures. The stable graphitic structure was altered again to the amorphous structure. Results are interpreted in terms of the oxidation of carbon particles in air. The differences in alterations among carbon particles, Pt clusters on carbon particles, and Pt clusters in carbon particles are presented on the basis of HRTEM images.
• Crystallinity of Mg-bearing silicate grains due to condensation or thermal evolution

  Y. Kimura, C. Kaito, J. A. Nuth

  METEORITICS & PLANETARY SCIENCE 43 (7) A76 - A76 1086-9379 2008/07 [Refereed][Not invited]
  
• Characteristic low-temperature crystallization of amorphous Mg-bearing silicate grains under electron irradiation

  Yuki Kimura, Yu Miyazaki, Akihito Kumamoto, Midori Saito, Chihiro Kaito

  ASTROPHYSICAL JOURNAL LETTERS 680 (1) L89 - L92 2008/06 [Not refereed][Not invited]
   

  Amorphous Mg-bearing silicate grains, which were produced by the coalescence between MgO and SiOx smoke particles, were crystallized to forsterite (Mg2SiO4) by electron-beam irradiation in a transmission electron microscope at room temperature. The crystallization induced by electron beams was accelerated by the presence of CH4 adsorbed on the surface and incorporated interior of the grains. This experimental result implies the possibility of low-temperature crystallization in a silicate carbon star. In the case of binary stars, since the materials that flow from the stars stationarily exist around the star, the formed amorphous silicate grains will be irradiated by electrons from the star for a long duration. As a result, a significant amount of crystalline silicates can be produced.
• Production of refractory-metal ultrafine particles by gas evaporation method and their surface oxide layer

  Yuki Kimura, Chihiro Kaito

  SURFACE & COATINGS TECHNOLOGY 202 (17) 4159 - 4162 0257-8972 2008/05 [Not refereed][Not invited]
   

  Generally, molybdenum, tungsten or tantalum is used as the evaporation source of many kinds of materials because of their high melting points and reasonably low vapor pressures. Therefore, the production of ultrafine particles of molybdenum, tungsten and tantalum has not been achieved by gas evaporation method. In this paper, it is shown that ultrafine particles of molybdenum, tungsten and tantalum were produced by a modified gas evaporation method. Transmission electron microscope observations show that the produced particles had a bcc structure with a size of less than 50 nm. Then, the thicknesses and the structures of the natural oxide layers were determined. Metallic particles develop an oxide layer on their surface and produce composite material automatically. Therefore, when metallic particles are used industrially or are treated in theoretical calculation studies, in view of realistic materials, the effect of the natural oxide layer must be considered. By the use of this modified gas evaporation method, ultrafine particles of many kinds of refractory materials will be produced. (C) 2008 Elsevier B.V. All rights reserved.
• A refractory Ca-SiO-H(2)-O(2) vapor condensation experiment with implications for calciosilica dust transforming to silicate and carbonate minerals

  Frans J. M. Rietmeijer, Aurora Pun, Yuki Kimura, Joseph A. Nuth

  ICARUS 195 (1) 493 - 503 0019-1035 2008/05 [Not refereed][Not invited]
   

  Condensates produced in a laboratory condensation experiment of a refractory Ca-SiO-H(2)-O(2) vapor define four specific and predictable deep metastable eutectic calciosilica compositions. The condensed nanograins are amorphous solids, including those with the stoichiometric CaSiO(3) pyroxene composition. In evolving dust-condensing astronomical environments they will be highly suitable precursors for thermally supported, dust-aging reactions whereby the condensates form more complex refractory silicates, e.g., diopside and wollastonite, and calcite and dolomite carbonates. This kinetically controlled condensation experiment shows how the aging of amorphous refractory. condensates could produce the same minerals that are thought to require high-temperature equilibrium condensation. We submit that evidence for this thermal annealing of dust will be the astronomical detection of silica (amorphous or crystalline) that is the common, predicted, by-product of most of these reactions. (C) 2007 Elsevier Inc. All rights reserved.
• A refractory Ca-SiO-H(2)-O(2) vapor condensation experiment with implications for calciosilica dust transforming to silicate and carbonate minerals

  Frans J. M. Rietmeijer, Aurora Pun, Yuki Kimura, Joseph A. Nuth

  ICARUS 195 (1) 493 - 503 0019-1035 2008/05 [Refereed][Not invited]
   

  Condensates produced in a laboratory condensation experiment of a refractory Ca-SiO-H(2)-O(2) vapor define four specific and predictable deep metastable eutectic calciosilica compositions. The condensed nanograins are amorphous solids, including those with the stoichiometric CaSiO(3) pyroxene composition. In evolving dust-condensing astronomical environments they will be highly suitable precursors for thermally supported, dust-aging reactions whereby the condensates form more complex refractory silicates, e.g., diopside and wollastonite, and calcite and dolomite carbonates. This kinetically controlled condensation experiment shows how the aging of amorphous refractory. condensates could produce the same minerals that are thought to require high-temperature equilibrium condensation. We submit that evidence for this thermal annealing of dust will be the astronomical detection of silica (amorphous or crystalline) that is the common, predicted, by-product of most of these reactions. (C) 2007 Elsevier Inc. All rights reserved.
• 原始太陽系星雲中での物質進化に関わるダストの振る舞い

  木村勇気

  日本惑星科学会誌 遊・星・人 日本惑星科学会 17 (1) 62 - 68 0918-273X 2008/03/25 [Not refereed][Not invited]
   

  ガスと宇宙固体微粒子(ダスト)から成る原始太陽系星雲中で,どのような物質進化を経て我々の太陽系が誕生したのだろうか,物理化学環境が異なる他の惑星系星雲中ではどのような物質進化を経るのであろうか.この疑問に対して実験室で再現実験からのアプローチを行なっている.ガスが凝縮してダストを形成する際,ナノメートルサィズを経て成長していく為,成長の初期段階においてはナノ領域特有の現象を考慮しなければならない.今回,ガス中蒸発法を応用したダスト類似物の生成実験と,ナノメートルサィズの微粒子の振る舞いに加え,ダストの成長や変成に対する駆動力として,プラズマや紫外線等がどの様に寄与するかについて述べる.
• 原始太陽系星雲中での物質進化に関わるダストの振る舞い,

  木村勇気

  日本惑星科学会誌 17 62 - 68 2008 [Not refereed][Not invited]
  
• Possible Driving Force behind Formation of Cosmic Carbyne Crystals

  Y. Kimura, C. Kaito

  The Astrophysical Journal Letters 685 83 - 86 2008 [Not refereed][Not invited]
  
• In situ observation of structural alteration process of filmy quenched carbonaceous composite

  Kumamoto A, Kimura Y, Kaito C, Wada S

  IAU Symposium Proceedings Series 4 433 - 434 2008 [Refereed][Not invited]
  
• Structural alteration of nanostructure carbon particles carrying Pt clusters in H-2 and O-2 gases

  Chihiro Kaito, Ryoichi Ono, Ryuta Sakao, Akihito Kuniamoto, Midori Saito, Yuki Kimura, Shinsuke Ohyagi

  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 46 (45-49) L1141 - L1142 0021-4922 2007/12 [Not refereed][Not invited]
   

  The effects of H-2 and O-2 gases on the typical fuel cell catalyst of Pt clusters on carbon particles (Pt on Q were examined using a special side-entry sample holder for high-resolution transmission electron microscopy, The holder can be used to transfer the specimen without exposure to air. The effects of H-2 and O-2 were detected after the specimen was exposed to the gases at 60 degrees C for 15 h. The predominant effect of H-2 was the coagulation of the Pt clusters. The effect of O-2 was to alter the structure of the carbon particles by oxidation.
• Exothermic chemical reactions can drive nonthermal crystallization of amorphous silicate grains

  Chihiro Kaito, Yu Miyazaki, Akihito Kumamoto, Yuki Kimura

  ASTROPHYSICAL JOURNAL 666 (1) L57 - L60 0004-637X 2007/09 [Not refereed][Not invited]
   

  explain how cometary silicates crystallize yet still preserve volatile interstellar ices in their parent comets, we experimentally demonstrate the possibility of chemical-reaction-driven crystallization, which is called nonthermal crystallization, using laboratory-synthesized amorphous Mg-bearing silicate grains. Analog silicate grains similar to 50- 100 nm in diameter covered with a carbonaceous layer consisting of amorphous carbon, CH 4, and other organics to a thickness of similar to 10-30 nm were used as models. The analog silicate grains crystallized via the direct flow of surface reaction energy, which is produced by the graphitization of the carbonaceous layer due to oxidation at room temperature in air, into the silicates. The experimental results imply that amorphous silicates are transformed into crystalline silicates as the grains leave the comet's surface, rather than as the comet was accreted 4.5 billion years ago. Thus, primordial ices and amorphous silicate grains are predicted to reside in most comets until they approach the Sun.
• What is the driving force to form refractory oxide grains? Silicate spectra depend on their formation environment

  Yuki Kimura, Joseph A. Nuth

  ASTROPHYSICAL JOURNAL 664 (2) 1253 - 1263 0004-637X 2007/08 [Not refereed][Not invited]
   

  We discuss room-temperature condensation experiments using either an electrical discharge or ultraviolet radiation to initiate gas-phase reactions resulting in silicate smokes. This formation process could represent processes occurring in low-density environments, because it is possible that the gases, which can condense at higher temperatures, remain after it cools, e. g., following a shock. In these environments, many condensates could be formed simultaneously. However, in the case of our iron silicate experiments, many of the smoke particles are iron silicate with a uniform composition that reflects the composition of the ambient gas atmosphere where they were produced. In these experiments, smoke particles of other materials such as iron oxide and silica were not formed. In the case of our Si-O experiments, hydro-silicate smoke particles are produced together with anhydrous silicate particles directly from the gas phase without later hydro alteration. The infrared spectra of these silicate particles show a very strong 11.36 mu m feature attributed to H2Si2O4 and possibly to Si2O3 compared with a simultaneously observed 9.2 mu m feature due to the Si-O vibration. We believe that finding the driving force for grain growth under a wide range of environmental conditions is important if we are to understand grain formation, because silicate grains, which formed in a plasma field or under UV irradiation, show different compositions, structures, shapes, and spectra from thermally condensed grains.
• Non-mass-dependent oxygen isotopic fractionation in smokes produced in an electrical discharge

  Yuki Kimura, Joseph A. Nuth, Subrata Chakpaborty, Mark H. Thiemens

  METEORITICS & PLANETARY SCIENCE 42 (7-8) 1429 - 1439 1086-9379 2007/07 [Not refereed][Not invited]
   

  We report the first production of non-mass-dependently fractionated silicate smokes from the gas phase at room temperature from a stream of silane and/or pentacarbonyl iron in a molecular hydrogen (or helium) flow mixed with molecular oxygen (or nitrous oxide). The smokes were formed at the Goddard Space Flight Center (GSFC) at total pressures of just under 100 Torr in an electrical discharge powered by a Tesla coil, were collected from the surfaces of the copper electrodes after each experiment and sent to the University of California at San Diego (UCSD) for oxygen isotopic analysis. Transmission electron microscopy studies of the smokes show that they grew in the gas phase rather than on the surfaces of the electrodes. We hypothesize at least two types of fractionation processes occurred during formation of the solids: a mass-dependent process that made isotopically lighter oxides compared to our initial oxygen gas composition followed by a mass-independent process that produced oxides enriched in (17)O and (18)O. The nnaximum Delta(17)O observed is +4.7 parts per thousand for an iron oxide produced in flowing hydrogen, using O(2) as the oxidant. More typical displacements are 1-2 parts per thousand above the equilibrium fractionation line. The chemical reaction mechanisms that yield these smokes are still under investigation.
• Crystal Growth on Mineralogical Evolution in the Early Solar Nebula

  KIMURA YUKI, KAITO CHIHIRO

  日本結晶成長学会誌 34 (2) 89 - 93 0385-6275 2007/07 [Not refereed][Not invited]
  
• Direct observation of the crystallization of carbon-coated amorphous Mg-bearing silicate grains

  Chihiro Kaito, Shinichi Sasaki, Yu Miyazaki, Akihito Kumamoto, Mami Kurumada, Kaori Yokoyama, Midori Saito, Yuki Kimura, Hitoshi Suzuki

  Advances in Geosciences: Volume 7: Planetary Science (PS) 7 125 - 131 2007/01/01 [Not refereed][Not invited]
   

  The crystallization of amorphous Mg-bearing silicate grains into Mg2SiO4 crystal covered with a thin carbon layer was directly observed by in-situ transmission electron microscopy. The temperature of crystallization of the sample was observed to be 200°C lower than that of the sample without the carbon layer. The graphitization energy of the surface amorphous carbon layer with the mean thickness of 10 nm accelerated the crystallization of the central amorphous Mg-bearing silicate grain of 100 nm order. Sample results for crystallization at room temperature are presented.
• New method of producing titanium carbide, monoxide, and dioxide grains in laboratory

  Akihito Kumamoto, Mami Kurumada, Yuki Kimura, Chihiro Kaito

  Advances in Geosciences: Volume 7: Planetary Science (PS) 7 93 - 99 2007/01/01 [Not refereed][Not invited]
   

  By making a carbon rod covered with Ti on the surface without exposure to air, TiC grains less than 10nm in diameter were predominantly produced. The introduction of a small amount of oxygen in Ar gas (partial pressure 1/1000), allowed the continuous formation of TiO2 and TiO-TiC. The infrared spectra of TiO2, TiO, and TiC were measured. An absorption feature attributed to TiO phase in oxidized TiC grains showed a characteristic peak at 14.7 µm.
• 原始太陽系における物質進化に関わる結晶成長

  木村勇気, 墻内千尋

  2007 [Not refereed][Not invited]
  
• Electric field effect for Pt particle on carbon particle

  H. Suzuki, H. Shingu, S. Morikawa, S. Ohyagi, Y. Kimura, M. Shintaku, A. Kumamoto, C. Kaito

  ECS Transactions 5 (1) 79 - 87 1938-5862 2007 

  The electric field influence of 1 volt on the typical polymer electrolyte fuel cell catalyst system carrying Pt clusters on amorphous carbon particles have been elucidated by transmission electron microscope observation. The same position was observed before and after exposing to the electric field. Surface of Pt clusters were covered with a few graphitic layers. The slight graphitization of amorphous carbon particles has been also occurred. The growth of Pt clusters has been discussed as the aggregation of the Pt atoms which exist on carbon particles. ©The Electrochemical Society.
• Variety of refractory oxide grains depend on formation environments

  Y. Kimura, J. A. Nuth

  METEORITICS & PLANETARY SCIENCE 41 (8) A95 - A95 1086-9379 2006/08 [Refereed][Not invited]
  
• Demonstration of crystal forsterite and stall state grain formations

  C. Kaito, S. Sasaki, Y. Miyazaki, M. Kurumada, A. Kumamoto, H. Suzuki, Y. Kimura, C. Koike

  METEORITICS & PLANETARY SCIENCE 41 (8) A91 - A91 1086-9379 2006/08 [Refereed][Not invited]
  
• Influence of plasma on formation of crystalline Fe2SiO4 grains

  T Sato, M Kurumada, K Kamitsuji, O Kido, H Suzuki, M Shintaku, Y Kimura, Y Saito, C Kaito

  PLANETARY AND SPACE SCIENCE 54 (6) 612 - 616 0032-0633 2006/05 [Not refereed][Not invited]
   

  The production of Fe2SiO4 (fayalite) crystalline grains was performed by two processes, namely, grain formation in a plasma field by evaporating a mixture powder of Fe and SiO and heat treatment of the product collected on the radio-frequency (RF) electrode side. Fe grains < 20 nm in size covered with an amorphous SiO layer selectively formed Fe2SiO4 grains by heating at 800 degrees C. By heating at 600 degrees C, in addition to the formation of Fe2SiO4 crystal grains, the FeO phase appeared. The doping effect of excited oxygen in a plasma field into the Fe small grains may be the trigger on the formation of fayalite through the FeO phase formation. The present experimental result suggests that the probability Of Fe2SiO4 grain formation in space is low. (c) 2006 Published by Elsevier Ltd.
• Laboratory analogy of crystalline enstatite grain formation in plasma field

  T Sato, K Kamitsuji, M Shintaku, Y Kimura, M Kurumada, O Kido, H Suzuki, Y Saito, C Kaito

  PLANETARY AND SPACE SCIENCE 54 (6) 617 - 620 0032-0633 2006/05 [Not refereed][Not invited]
   

  Crystalline enstatite (MgSiO3) grains were produced by the simultaneous evaporation of SiO grains and Mg vapor in a plasma field. The MgSiO3 grains were spherical or needlelike. The necessity of a plasma field in astromineralogy is suggested in the present study. (c) 2006 Published by Elsevier Ltd.
• Formation of TiC core-graphitic mantle grains from CO gas

  Yuki Kimura, Joseph A. Nuth, Frank T. Ferguson

  METEORITICS & PLANETARY SCIENCE 41 (5) 673 - 680 1086-9379 2006/05 [Not refereed][Not invited]
   

  We demonstrate a new formation route for TiC core-graphitic mantle spherules that does not require carbon-atom addition and the very long time scales associated with such growth (Bernatowicz et al. 1996). Carbonaceous materials can be formed from C2H2 and its derivatives, as well as from CO gas. In this paper, we will demonstrate that large-cage-structure carbon particles can be produced from CO gas by the Boudouard reaction. Since the sublimation temperature for such fullerenes is low, the large cages can be deposited onto previously nucleated TiC and produce TiC core-graphitic mantle spherules. New constraints for the formation conditions and the time scale for the formation of TiC core-graphitic mantle spherules are suggested by the results of this study. In particular, TiC core-graphitic mantle grains that are found in primitive meteorites that have never experienced hydration Could be mantled by fullerenes or carbon nanotubes rather than by graphite. In situ observations of these grains in primitive anhydrous meteoritic matrix could confirm or refute this prediction and would demonstrate that the graphitic mantle on such grains is a metamorphic feature due to interaction of the presolar fullerenes with water within the meteorite matrix.
• Synthesis of Al-Cr decagonal quasicrystal nanoparticles and their temperature of phase transformation to stable crystal phase

  O Kido, M Kurumada, K Kamltsuji, T Tanigaki, T Sato, Y Kimura, H Suzuki, Y Saito, C Kaito

  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 31 (2) 169 - 173 1386-9477 2006/03 [Not refereed][Not invited]
   

  The synthesis of Al-Cr single quasicrystal (QC) nanoparticles of the decagonal phase was achieved by introducing an advanced gas flow evaporation method. By obtaining Successive electron diffraction patterns for single-QC nanoparticles, the phase transformation temperature of a single-QC nanoparticle was determined to be 700 degrees C. It was also determined that part of the QC nanoparticle decomposed into hex-AI(8)Cr(5) and Al during the phase transformation. Since the grain growth did not occur during the phase transformation in the present experiment, the inherent phase transformation temperature could be measured. (c) 2006 Elsevier B.V. All rights reserved.
• Formation of CaTiO3 crystalline dust in laboratory

  K. Yokoyama, Y. Kimura, O. Kido, M. Kurumada, A. Kumamoto, C. Kaito

  Advances in Geosciences 7 115 - 123 2006 [Not refereed][Not invited]
  
• Laboratory production of magnesium sulfide grains and their characteristic infrared spectra due to shape

  Y Kimura, M Kurumada, K Tamura, C Koike, H Chihara, C Kaito

  ASTRONOMY & ASTROPHYSICS 442 (2) 507 - 512 0004-6361 2005/11 [Not refereed][Not invited]
   

  Nanosized MgS grains, which have been considered the origin of the 30 mu m emission feature of carbon-rich evolved objects, were produced from the gas phase using an advanced gas evaporation method. The far-infrared spectrum of cubic MgS grains showed a characteristic absorption peak at 311 cm(-1) (32.1 mu m) with three shoulders at 460, 400 and 262 cm(-1) (21.7, 25.0 and 38.2 mu m). On the other hand, when the grains were roundish or network-like, the absorption peak at 250 cm(-1) became predominant. The cubic MgS grains were produced by direct nucleation from the gas phase. In the case of production via a gas-solid reaction, the MgS grains were network-like. Therefore, the formation environments of MgS grains around carbon-rich evolved objects may be predicted from the intensity of 310 and 250 cm(-1) bands. We suggest that the origins of the absorption band at 310 and 250 cm(-1) are (100), (110) and/or (111) surfaces of MgS grains, respectively.
• Is the 21 micron feature observed in some post-AGB stars caused by the interaction between Ti atoms and fullerenes?

  Y Kimura, JA Nuth, FT Ferguson

  ASTROPHYSICAL JOURNAL 632 (2) L159 - L162 0004-637X 2005/10 [Not refereed][Not invited]
   

  Recent measurements of fullerenes and Ti atoms recorded in our laboratory have demonstrated the presence of an infrared feature near 21 mu m. The feature observed has nearly the same shape and position as is observed for one of the most enigmatic features in post-asymptotic giant branch (AGB) stars. In our experimental system, large-cage carbon particles, such as large fullerenes, were produced from CO gas by the Boudouard reaction. Large-cage carbon particles intermixed with Ti atoms were produced by the evaporation of a Ti-metal-wrapped carbon electrode in CO gas. The infrared spectra of large fullerenes interacting with Ti atoms show a characteristic feature at 20.3 mu m that closely corresponds to the 20.1 mu m feature observed in post-AGB stars. Both the laboratory and stellar spectra also show a small but significant peak at 19.0 mu m, which is attributed to fullerenes. Here we propose that the interaction between fullerenes and Ti atoms may be a plausible explanation for the 21 mu m feature seen in some post-AGB stars.
• Is the 21 micron feature observed in some post-AGB stars caused by the interaction between Ti atoms and fullerenes?

  Y Kimura, JA Nuth, FT Ferguson

  ASTROPHYSICAL JOURNAL 632 (2) L159 - L162 0004-637X 2005/10 [Refereed][Not invited]
   

  Recent measurements of fullerenes and Ti atoms recorded in our laboratory have demonstrated the presence of an infrared feature near 21 mu m. The feature observed has nearly the same shape and position as is observed for one of the most enigmatic features in post-asymptotic giant branch (AGB) stars. In our experimental system, large-cage carbon particles, such as large fullerenes, were produced from CO gas by the Boudouard reaction. Large-cage carbon particles intermixed with Ti atoms were produced by the evaporation of a Ti-metal-wrapped carbon electrode in CO gas. The infrared spectra of large fullerenes interacting with Ti atoms show a characteristic feature at 20.3 mu m that closely corresponds to the 20.1 mu m feature observed in post-AGB stars. Both the laboratory and stellar spectra also show a small but significant peak at 19.0 mu m, which is attributed to fullerenes. Here we propose that the interaction between fullerenes and Ti atoms may be a plausible explanation for the 21 mu m feature seen in some post-AGB stars.
• Laboratory production of monophase pyrrhotite grains using solid-solid reaction and their characteristic infrared spectra

  Y Kimura, K Tamura, C Koike, H Chihara, C Kaito

  ICARUS 177 (1) 280 - 285 0019-1035 2005/09 [Not refereed][Not invited]
   

  A new method of producing pyrrhotite grains, which are most commonly found in cometary material and interplanetary dust particles, was developed. Pyrrhotite grains in the monophase having a 7C structure were predominately produced using a solid-solid reaction between iron and sulfur grains at room temperature. The characteristic infrared peaks were observed at 602, 563, and 397 cm(-1) (16.6, 17.8, and 25.2 mu m). (c) 2005 Elsevier Inc. All rights reserved.
• Laboratory synthesized calcium oxide and calcium hydroxide grains: A candidate to explain the 6.8 mu m band

  Y Kimura, JA Nuth

  ASTROPHYSICAL JOURNAL 630 (1) 637 - 641 0004-637X 2005/09 [Refereed][Not invited]
   

  We demonstrate that CaO and Ca(OH)(2) are excellent candidates to explain the 6.8 mu m feature, which is one of the most obscure features in young stellar objects. We discuss the condensation of CaO grains and the potential formation of a Ca(OH)(2) surface layer. The infrared spectra of these grains are compared with the spectra of 15 young stellar objects. We note that CaO-rich grains are seen in all meteoritic CAIs (calcium-aluminum-rich inclusions) and that the 6.8 mu m feature has only been observed in young stellar objects. Therefore, we consider CaO grains to be a plausible candidate to explain the 6.8 mu m feature and hypothesize that they are produced in the hot interiors of young stellar environments.
• Formation of carbon nanotubes from mixture film of carbon and titanium

  Y Kimura, C Kaito

  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 28 (3) 281 - 285 1386-9477 2005/08 [Not refereed][Not invited]
   

  It was shown that a carbon nanotube was selectively formed from carbon film containing Ti, supported by a standard Mo transmission electron microscopic grid, by heating at 800 degrees C in vacuum. With heating above 950 degrees C, graphite and rutile crystals of TiO2 predominately appeared. The formation of oxide is due to the supply of oxygen from the Mo grid. The formation mechanism of the carbon nanotubes was discussed on the basis of the heat of combustion due to the oxidation of titanium. The present result will lead to the development of an efficient method of production of carbon nanotubes. (c) 2005 Elsevier B.V. All rights reserved.
• Direct observation of thermal alteration of mixed film of Ge and SiO

  C Kaito, K Kamitsuji, S Tanaka, O Kido, M Kurumada, T Sato, Y Kimura, H Suzuki, Y Saito

  THIN SOLID FILMS 483 (1-2) 396 - 399 0040-6090 2005/07 [Not refereed][Not invited]
   

  The dynamic behavior of a film produced by coevaporation of Ge-SiO was observed in situ using a transmission electron microscope. The film produced had an amorphous structure containing Si, Ge and SiO2. A characteristic change of the film was observed above 500 degrees C. Upon heating at 750 degrees C, in addition to the growth of the SiGe mixed crystal with the diamond structure, the liquidlike mixed phase of SiGe-SiO2 was also produced. The growth process of the liquidlike phase was directly observed in situ. The growth process of Ge and GeSi nanocrystallites has been elucidated by cooling the mixed film to room temperature. (c) 2004 Elsevier B.V All rights reserved.
• Novel routes for diamond formation in interstellar ices and meteoritic parent bodies

  A. Kouchi, H. Nakano, Y. Kimura, C. Kaito

  Astrophysical Journal 626 (2) L129 - L132 1538-4357 2005/06/20 [Not refereed][Not invited]
   

  We have identified new formation routes of diamond in interstellar clouds and parent bodies of carbonaceous chondrites in laboratory experiments. The diamond precursor nucleated under UV photolysis of interstellar ice mixtures in molecular clouds and grew with further UV irradiation in diffuse clouds. The present study supports the occurrence of diamonds in interstellar clouds and suggests that diamond is ubiquitous in space. We also performed experiments on the processes of aqueous alteration and subsequent thermal metamorphism of organic materials formed in molecular clouds, and the results were consistent with the formation of diamonds by this process in the parent bodies of carbonaceous chondrites. The various characteristics of nanodiamonds in chondrites and interplanetary dust are well explained by these new formation routes. © 2005. The American Astronomical Society. All rights reserved.
• Production of diamond and solid-solution nanoparticles in the carbon-silicon system using radio-frequency plasma

  Y Kimura, T Sato, C Kaito

  CARBON 43 (7) 1570 - 1574 0008-6223 2005/06 [Not refereed][Not invited]
  
• Formation of new carbides with diamond structure from carbon film containing transition metal.

  Y Kimura, C Kaito

  THIN SOLID FILMS 476 (1) 65 - 67 0040-6090 2005/04 [Not refereed][Not invited]
   

  New carbide crystallites, which have a solid-solution phase with diamond structure, were formed from amorphous carbon film containing a transition metal such as Fe, Co, Mo or Ti by vacuum heating at 500-800 degrees C. The lattice constants for each solid-solution phase have been determined from electron diffraction patterns and high-resolution transmission electron microscope images. The formation of carbon polymorphs has been summarized as being dependent on the heat treatment temperature. (c) 2004 Elsevier B.V. All rights reserved.
• Crystal structure and growth of carbon-silicon mixture film prepared by ion sputtering

  Y. Kimura, M. Ishikawa, M. Kurumada, T. Tanigaki, H. Suzuki, C. Kaito

  JOURNAL OF CRYSTAL GROWTH 275 (1-2) E977 - E981 0022-0248 2005/02 [Not refereed][Not invited]
   

  Si (10-50%)-containing carbon (C-Si) films were prepared by ion sputtering of carbon and silicon carbide mixture pellets. The C-Si film was composed of a solid-solution phase of carbon and silicon with a diamond structure. The film showed a higher transparency than a simultaneously evaporated C-Si mixture film. Diamond crystals 100 nm in diameter were also produced by vacuum heating of C-Si film at 800 degrees C: The infrared spectrum showed significant absorption features at 9.5 and 21 mu m; in contrast to the 11 and 12 mm of SiC. The 21 mu m feature is one of the candidate unidentified infrared bands on the spectra of carbon-rich post-asymptotic giant branch stars. (C) 2004 Elsevier B.V. All rights reserved.
• Structure of WO3 ultrafine particles and their characteristic solid states

  Mami Kurumada, Osamu Kido, Takeshi Sato, Hitoshi Suzuki, Yuki Kimura, Katsuya Kamitsuji, Yoshio Saito, Chihiro Kaito

  JOURNAL OF CRYSTAL GROWTH 275 (1-2) E1673 - E1678 0022-0248 2005/02 [Not refereed][Not invited]
   

  WO3 nanoparticles from 10 to 250nm in diameter were formed by burning tungsten wire in low-oxygen-partial-pressure atmosphere in Ar gas. The structure of the 10-nm-order particle was cubic WO3, and for the particle larger than 50 nm, the structure was triclinic WO3. The color of the produced samples changed from blue to yellowish green and yellow depending on the particle size. It was also shown that the present particle is a good transmittance material for mid-IR light with wavelength between 5 and 20 mu m. The growth of huge particles by coalescence growth in smoke has been discussed. (C) 2004 Elsevier B.V. All rights reserved.
• Production of transition metal-doped ZnO nanoparticles by using RF plasma field

  Takeshi Sato, Hitoshi Suzuki, Osamu Kido, Mami Kurumada, Katsuya Kamitsuji, Yuki Kimura, Hiromichi Kawasaki, Satoo Kaneko, Yoshio Saito, Chihiro Kaito

  JOURNAL OF CRYSTAL GROWTH 275 (1-2) E983 - E987 0022-0248 2005/02 [Not refereed][Not invited]
   

  Transition metals, such as tungsten (W), molybdenum (Mo) and chromium (Cr), were doped into ZnO nanoparticles using an RF plasma system. The resulting ZnO nanoparticles with the size of 30-50 nm changed from white to yellowish or to orange depending on the doped transition metals. The doping position of these transition metals in the ZnO crystal was the same as that determined in a previous paper (J. Crystal Growth 265 (2004) 149). It was found that light with wavelength shorter than 385 nm can be removed by doping. The morphological change due to doping of elements was discussed in terms of the difference of ionicity. (C) 2004 Elsevier B. V. All rights reserved.
• Morphological alteration upon phase transition and effects of oxygen impurities of chromium nanoparticles

  Osamu Kido, Katsuya Kamitsuji, Mami Kurumada, Takeshi Sato, Yuki Kimura, Hitoshi Suzuki, Yoshio Saito, Chihiro Kaito

  JOURNAL OF CRYSTAL GROWTH 275 (1-2) E1745 - E1750 0022-0248 2005/02 [Not refereed][Not invited]
   

  The morphological alteration from delta- to alpha-Cr nanoparticles and the phase transition temperature were directly observed by in situ experiment using a transmission electron microscope. The icositetrahedral nanoparticle of delta-Cr transformed into a rhombic dodecahedral nanoparticle of alpha-Cr upon heating at 550 degrees C: It was demonstrated that the most stable shape of the alpha-Cr nanoparticle is the rhombic dodecahedron. Upon heating the alpha-Cr nanoparticle at 650 degrees C; the (1 1 3) layer of Cr2O3 grew topotactically in the direction of [100] of alpha-Cr nanoparticle. We concluded that the alpha-Cr nanoparticle includes about 20-30 at% oxygen, as estimated from the volume of the Cr2O3 surface layer. (C) 2004 Elsevier B.V. All rights reserved.
• Laboratory synthesized calcium oxide and calcium hydroxide grains: A candidate to explain the 6.8 μm band

  Y. Kimura, J. A. Nuth III

  The Astrophysical Journal 630 637 - 641 2005 [Not refereed][Not invited]
  
• Crystalline Mg2SiO4 and amorphous Mg-bearing silicate grain formation by coalescence and growth

  K Kamitsuji, H Suzuki, Y Kimura, T Sato, Y Saito, C Kaito

  ASTRONOMY & ASTROPHYSICS 429 (1) 205 - 208 0004-6361 2005/01 [Not refereed][Not invited]
   

  A novel method for producing MgO and SiO2 smokes was developed. Mg-bearing silicate grain formation using the coalescence and growth of MgO and SiO2 grains was carried out in our laboratory. It becomes evident that single and poly crystalline Mg2SiO4 (forsterite) and amorphous Mg-bearing silicate grains can be produced by the coalescence and growth of MgO and SiO2 grains. This result suggests that the observed crystalline Mg2SiO4 grains and amorphous Mg-bearing silicate particles in Red Super Giant (RSG), Asymptotic Giant Branch (AGB), post-AGB and planetary nebula (PNe) could be produced by the coalescence and growth of MgO and SiO2 grains.
• Transition temperature to crystal phase of Al86Mn14 quasicrystal ultrafine particles determined by direct observation and characterization of surface oxide layer

  O Kido, H Suzuki, Y Kimura, T Sato, Y Saito, C Kaito

  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 25 (4) 619 - 624 1386-9477 2005/01 [Not refereed][Not invited]
   

  Al-Mn quasicrystal ultrafine particles can be produced by the advanced gas evaporation method (AGEM), which is a method of preparing ultrafine alloy particles by coalescence growth among the particles near the evaporation sources. We investigated the phase transition temperature from a quasicrystal to a stable crystal, by examining successive electron diffraction patterns of an ultrafine particle in an in situ experiment using a transmission electron microscope. In spite of the report that the Al86Mn14 quasicrystal transforms into the crystal phase at around 400-670 degreesC on thin film specimens, the quasicrystal ultrafine particle transformed at 800 degreesC, i.e., the quasicrystal ultrafine particle is more stable. Since the cross-sectional view of the surface oxide layer of the quasicrystal ultrafine particles can be easily observed, the surface oxides of eta-Al2O3 and MnO were characterized as a result of the oxidation of residual atoms on the surface of the produced alloy particles including the quasicrystals. The conditions required for Al-Mn quasicrystal ultrafine particle formation by the AGEM can be estimated under the cooling rate of 105 K/s. (C) 2004 Elsevier B.V. All rights reserved.
• Direct observation of the formation of alumina phase by metallic Al solid-SiO(2) solid reaction

  S Sasaki, H Suzuki, Y Kimura, T Sato, T Tanigaki, O Kido, K Kamitsuji, M Kurumada, C Kaito

  EARTH PLANETS AND SPACE 57 (5) 399 - 401 1343-8832 2005 [Not refereed][Not invited]
   

  The formation of Al(2)O(3) phases by the solid-solid reaction of a metallic Al layer evaporated on a SiO(2) amorphous grain has been induced by heating above 600 degrees C in vacuum (1 x 10(-6) Pa). The distortion process of the amorphous SiO(2) grains by the formation of Al(2)O(3) have been directly imaged by in-situ TEM observation. A partly deposited Al layer covered the SiO(2) grains after heating at 750 degrees C, and gamma-Al(2)O(3) grains of about 25 nm diameters were formed on the SiO(2) surface. Upon the growth of Al(2)O(3), the SiO(2) grain decomposed into a mixture of metallic Si and SiO(2) and disappeared as a result of sublimation due to the formation of SiO(x) at high temperatures. The present result on dust surface dynamics will become an important field with respect to the metamorphism of grains from the astromineralogical viewpoint.
• Direct observation of the metamorphism of silicon oxide grains

  K Kamitsuji, S Ueno, H Suzuki, Y Kimura, T Sato, T Tanigaki, O Kido, M Kurumada, C Kaito

  ASTRONOMY & ASTROPHYSICS 422 (3) 975 - 979 0004-6361 2004/08 [Not refereed][Not invited]
   

  Experimental studies on the metamorphism of SiO(x) grains under heating at 10(-6) Pa have been conducted using a high-resolution transmission electron microscope. Si crystallites were predominantly grown at 500 to 700 degreesC in SiO(x) grains. The Si crystallites disappeared at 800 degreesC and evaporated as the SiO phase.
• Growth of diamond from Si-containing amorphous carbon film using synchrotron radiation

  Y Kimura, O Kido, M Oomoto, K Ogawa, H Namba, C Kaito

  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 43 (7A) L888 - L890 0021-4922 2004/07 [Not refereed][Not invited]
   

  Si-doped amorphous carbon film prepared by the simultaneous vacuum evaporation of carbon and silicon has been irradiated by a synchrotron radiation (SR) beam. The preferential growth of diamond crystals was found by transmission electron microscope observation conducted after SR irradiation. It was also found that the solid-solution phase of carbon and silicon with the diamond structure was produced in the as-deposited film and at the initial stage of the crystallization. The solid-solution crystal remained in the stable phase up to 6 nm in size. The catalytic effect of Si was prominent in the growth of diamond.
• Phase transition temperature of gamma-Fe2O3 ultrafine particle

  O Kido, Y Higashino, K Kamitsuji, M Kurumada, T Sato, Y Kimura, H Suzuki, Y Saito, C Kaito

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 (7) 2014 - 2016 0031-9015 2004/07 [Not refereed][Not invited]
   

  The iron oxide ultrafine particles prepared by the gas evaporation method, in which commercial alpha-Fe2O3 powder is evaporated, are composed of alpha-Fe2O3 particles covered with a gamma-Fe2O3 mantle layer. To study the phase transition temperature of the gamma-Fe2O3 mantle layer, the particles were heated and observed in a transmission electron microscope. The present specimen of gamma-Fe2O3 transformed completely to alpha-Fe2O3 at above 700degreesC, and this phase transition was irreversible. The phase transition temperature was 1.4 times higher than the bulk value. The growth mechanism of the present specimen of alpha-Fe2O3 particles covered with the gamma-Fe2O3 mantle layer has been discussed in terms of the difference in the cooling rates between the inside and the surface of the particle at around the evaporation source.
• Phase transition temperature of gamma-Fe2O3 ultrafine particle

  O Kido, Y Higashino, K Kamitsuji, M Kurumada, T Sato, Y Kimura, H Suzuki, Y Saito, C Kaito

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 (7) 2014 - 2016 0031-9015 2004/07 [Refereed][Not invited]
   

  The iron oxide ultrafine particles prepared by the gas evaporation method, in which commercial alpha-Fe2O3 powder is evaporated, are composed of alpha-Fe2O3 particles covered with a gamma-Fe2O3 mantle layer. To study the phase transition temperature of the gamma-Fe2O3 mantle layer, the particles were heated and observed in a transmission electron microscope. The present specimen of gamma-Fe2O3 transformed completely to alpha-Fe2O3 at above 700degreesC, and this phase transition was irreversible. The phase transition temperature was 1.4 times higher than the bulk value. The growth mechanism of the present specimen of alpha-Fe2O3 particles covered with the gamma-Fe2O3 mantle layer has been discussed in terms of the difference in the cooling rates between the inside and the surface of the particle at around the evaporation source.
• Growth of diamond from Si-containing amorphous carbon film using synchrotron radiation

  Y Kimura, O Kido, M Oomoto, K Ogawa, H Namba, C Kaito

  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 43 (7A) L888 - L890 0021-4922 2004/07 [Refereed][Not invited]
   

  Si-doped amorphous carbon film prepared by the simultaneous vacuum evaporation of carbon and silicon has been irradiated by a synchrotron radiation (SR) beam. The preferential growth of diamond crystals was found by transmission electron microscope observation conducted after SR irradiation. It was also found that the solid-solution phase of carbon and silicon with the diamond structure was produced in the as-deposited film and at the initial stage of the crystallization. The solid-solution crystal remained in the stable phase up to 6 nm in size. The catalytic effect of Si was prominent in the growth of diamond.
• Correlations between crystallite size, shape, surface, and infrared spectra using the Ti-C system

  Y Kimura, A Ikegami, M Kurumada, K Kamitsuji, C Kaito

  ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 152 (2) 297 - 301 0067-0049 2004/06 [Not refereed][Not invited]
   

  crystallites less than 10 nm in size showed an absorption feature at 14.3 mum. This 14.3 mum absorption was rarely seen in specimens ranging from bulk material to grains of 50 nm in size. The 14.3 mum feature was weakened as a result of the growth of TiC crystallites by heat treatment. When the carbide grains were covered with a carbon layer, the absorption peaks were considerably weakened, i.e., the absorption intensity depended on the grain surface state. A possible explanation is that the effects of size and shape on the spectra depend on the surface anisotropy.
• TEM study of early Ni4Ti3 precipitation and R-phase in Ni-rich NiTi nanoparticles

  M Kurumada, Y Kimura, H Suzuki, O Kido, Y Saito, C Kaito

  SCRIPTA MATERIALIA 50 (11) 1413 - 1416 1359-6462 2004/06 [Not refereed][Not invited]
   

  The structure of NiTi shape memory alloy nanoparticles was determined by high-resolution electron microscopy. The mixture of Ni4Ti3 and R-phases was observed, which clearly showed lattice relationships of (2 (1) over bar 1)(B2)//(1 0 1)Ni4Ti3 and (2 (2) over bar 0)(B2)//(1 3 1)Ni4Ni3. Lattice images of an R-phase particle suggested the existence of a Ni-rich Guinier-Preston zone (G.P. zone). (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
• Growth and structure of Ge clusters produced by Ge-C co-evaporation

  S Tanaka, O Kida, M Kurumada, K Kamitsuji, Y Kimura, H Suzuki, Y Saito, C Kaito

  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 23 (1-2) 108 - 113 1386-9477 2004/06 [Not refereed][Not invited]
   

  Complete mixture films of carbon and germanium produced by the co-evaporation in vacuum were directly heated in a transmission electron microscope. It was noticed that the diffusion and growth of Ge dots in the mixture film take place at approximately 500degreesC. On the other hand, Ge dots coated with amorphous carbon were produced by simultaneous evaporation of carbon and Ge in Ar gas at 10 kPa. In addition to Ge clusters of 3-10 nm in size, multiple-twin Ge clusters with the size of 10 nm have been produced in carbon soot. These Ge clusters showed a diamond structure. The growth process of Ge clusters in amorphous carbon soot has been discussed using the result in the mixture film experiment and temperature distribution in the particle formation process. (C) 2004 Elsevier B.V. All rights reserved.
• Correlations between crystallite size, shape, surface, and infrared spectra using the Ti-C system

  Y Kimura, A Ikegami, M Kurumada, K Kamitsuji, C Kaito

  ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 152 (2) 297 - 301 0067-0049 2004/06 [Refereed][Not invited]
   

  crystallites less than 10 nm in size showed an absorption feature at 14.3 mum. This 14.3 mum absorption was rarely seen in specimens ranging from bulk material to grains of 50 nm in size. The 14.3 mum feature was weakened as a result of the growth of TiC crystallites by heat treatment. When the carbide grains were covered with a carbon layer, the absorption peaks were considerably weakened, i.e., the absorption intensity depended on the grain surface state. A possible explanation is that the effects of size and shape on the spectra depend on the surface anisotropy.
• Pentagonal configuration in GaP ultrafine particle

  T Tanigaki, Y Kimura, H Suzuki, M Kurumada, C Kaito

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 (5) 1375 - 1376 0031-9015 2004/05 [Not refereed][Not invited]
  
• Novel method of doping tungsten into zinc oxide ultrafine particle using RF plasma system

  T Sato, H Suzuki, O Kido, M Kurumada, K Kamitsuji, Y Kimura, A Takeda, S Kaneko, Y Saito, C Kaito

  JOURNAL OF CRYSTAL GROWTH 265 (1-2) 149 - 153 0022-0248 2004/04 [Not refereed][Not invited]
   

  A tungsten plate was set on a one-plate electrode in RF plasma using parallel plates in a mixed gas of argon (9.75 Torr) and oxygen (0.25 Torr). Zn smoke was introduced into the plasma field. W atoms were doped in the ZnO smoke formation field in the RF plasma system. The resulting particles with a size of 30 run were identified to be hexagonal ZnO particles. The collected particles changed from white to yellow, i.e., W atoms were doped into ZnO particles. The image of the (0 0 0 1) lattice, which is the forbidden reflection, appeared predominantly in the W-doped ZnO particle. Furthermore, by optical measurement. it Was found that the existence of W atoms can control the recombination radiation due to the exciton. On the basis of high-resolution transmission electron microscopic images, the doped W positions are discussed as being in the commensurate Configuration of W items in the ZnO crystal at positions equivalent to those in the cubic anti-fluoride structure. (C) 2004 Elsevier B.V. All rights reserved.
• Novel method of doping tungsten into zinc oxide ultrafine particle using RF plasma system

  T Sato, H Suzuki, O Kido, M Kurumada, K Kamitsuji, Y Kimura, A Takeda, S Kaneko, Y Saito, C Kaito

  JOURNAL OF CRYSTAL GROWTH 265 (1-2) 149 - 153 0022-0248 2004/04 [Refereed][Not invited]
   

  A tungsten plate was set on a one-plate electrode in RF plasma using parallel plates in a mixed gas of argon (9.75 Torr) and oxygen (0.25 Torr). Zn smoke was introduced into the plasma field. W atoms were doped in the ZnO smoke formation field in the RF plasma system. The resulting particles with a size of 30 run were identified to be hexagonal ZnO particles. The collected particles changed from white to yellow, i.e., W atoms were doped into ZnO particles. The image of the (0 0 0 1) lattice, which is the forbidden reflection, appeared predominantly in the W-doped ZnO particle. Furthermore, by optical measurement. it Was found that the existence of W atoms can control the recombination radiation due to the exciton. On the basis of high-resolution transmission electron microscopic images, the doped W positions are discussed as being in the commensurate Configuration of W items in the ZnO crystal at positions equivalent to those in the cubic anti-fluoride structure. (C) 2004 Elsevier B.V. All rights reserved.
• Production and structural characterization of carbon soot with narrow UV absorption feature

  Y Kimura, T Sato, C Kaito

  CARBON 42 (1) 33 - 38 0008-6223 2004 [Not refereed][Not invited]
   

  In the present study, by a simple method, carbon soot with a narrow absorption features at around 220 nm was produced by pyrolysis of methane gas at a hot (1400-2800degreesC) filament. A detailed correlation between the structure and the optical spectra of carbon soot was carried out using a high-resolution transmission electron microscope. It appears that the origin of the narrow absorption peak is an onion-like graphitic structure. Interestingly, we found that the absorption peak position and the size of the soot can be controlled by the production temperature. The absorption peak is located at 217.5 nm, i.e., at the position of an intense interstellar absorption, when the onion structure has about 5 nm diameter. Infrared spectroscopy was applied to further elucidate the chemical composition of the obtained soot. (C) 2003 Elsevier Ltd. All rights reserved.
• Direct observation of sublimation process on a CdTe(111) surface using an ultrafine particle

  T Tanigaki, Y Kimura, H Suzuki, C Kaito

  JOURNAL OF CRYSTAL GROWTH 260 (3-4) 298 - 303 0022-0248 2004/01 [Not refereed][Not invited]
   

  A particle with a CdTe core and carbon mantle was produced by the advanced carbon-coating method which enables direct coverage with a carbon layer using an electron microscope. The coagulated particles containing approximately 30-200 CdTe particles produced by the gas evaporation method were covered with a carbon layer of about 7 nm thickness at 300 degreesC. By heating these particles above 500 degreesC, the sublimation process of a part of the CdTe particle can be directly captured by high-resolution transmission electron microscopy and recorded in real time on videotape. Sublimation on the CdTe(111) surfaces occurred in the step flow mode of two (111) layers. It was observed that two (111) zinc-blende layers changed to the (0002) wurtzite configuration unit just before sublimation. The condensation of CdTe on the sublimated particle surface and growth of CdTe in the carbon layers were also captured in the video image. These sublimation processes were discussed in terms of the existence of the polarity of II-VI compounds. (C) 2003 Elsevier B.V. All rights reserved.
• Mechanism of copper selenide growth on copper-oxide-selenium system

  Y Ishikawa, O Kido, Y Kimura, M Kurumada, H Suzuki, Y Saito, C Kaito

  SURFACE SCIENCE 548 (1-3) 276 - 280 0039-6028 2004/01 [Not refereed][Not invited]
   

  Transmission electron microscopy was used to study spontaneous copper selenide formation on Cu particles covered with an oxide layer. Even if the copper particle surface was covered with a Cu2O layer, selenides were formed by diffusion through the metal oxide layer. For a particle size less than 50 nm, selenide was formed in Cu particles by the diffusion of Se atoms passing through the Cu2O layer. For particles larger than 100 nm in size, selenide was formed in Se film. It was also found that the thickness of the Cu2O layer on the surface of Cu particle accelerated diffusion of Se atoms to the copper particle. (C) 2003 Elsevier B.V. All rights reserved.
• Effect of RF plasma field on the growth of C-60 crystals

  T Sato, O Kido, M Kurumada, Y Kimura, H Suzuki, Y Saito, C Kaito

  CARBON 42 (8-9) 1875 - 1877 0008-6223 2004 [Not refereed][Not invited]
  
• Structure and thickness of natural oxide layer on ultrafine particle

  K Tamura, Y Kimura, H Suzuki, O Kido, T Sato, T Tanigaki, M Kurumada, Y Saito, C Kaito

  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 42 (12) 7489 - 7492 0021-4922 2003/12 [Not refereed][Not invited]
   

  Ultrafine particles of various metals [Cr, Mn, Fe, Al, Ni, Cu, In, Si, Ge, Zn, Mg and Sn], produced by the gas evaporation method were covered with the oxide layer of thickness less than 10 nm by exposure to air. In order to clarify the structure and thickness of the surface oxide layer, on various metal ultrafine particles, high-resolution electron microscopy and infrared spectroscopy have been extensively used.
• Infrared spectra of ZrC presolar grain analogues

  Y Kimura, C Kaito

  ASTRONOMY & ASTROPHYSICS 409 (1) 159 - 161 0004-6361 2003/10 [Not refereed][Not invited]
   

  The origins of spectral feature of stellar source are identified on the basis of laboratory studies. Although ZrC grains were identified as the crystalline presolar grains in meteorites, the spectral data of ZrC grains have not been measured in the laboratory. Therefore, ZrC grains with the same size as the presolar grains were produced in the laboratory. It has been found that the infrared spectrum of ZrC grains shows broad absorption features at 9.4 and 12.4 mum.
• Dynamic behavior of SiO- and SiO2-coated ZnO ultrafine particles and growth mechanism of Zn2SiO4 crystal

  T Tanigaki, H Suzuki, Y Kimura, O Kido, Y Saito, C Kaito

  JOURNAL OF CRYSTAL GROWTH 256 (3-4) 317 - 323 0022-0248 2003/09 [Not refereed][Not invited]
   

  In order to elucidate the stability of a silicon oxide layer on zoo, the dynamic behavior of SiO- and SiO2-layer-coated ZnO ultrafine particle surfaces were directly observed by heating in a transmission electron microscope up to 700degreesC. In the case of SiO-coated ZnO ultrafine particles, ZnO nanocrystallites with the size of 2 nm grew in the SiO layer at 500degreesC. In the case of SiO-coated ZnO ultrafine particles, beta-cristobalite with the size of 10nm order was grown at 600degreesC. Zn2SiO4 particles were grown by coalescence between beta-cristobalite and ZnO at 700degreesC. By comparing the SiO and SiO, layers on ZnO ultrafine particles, it was found that the behaviors of the two silicon oxide layers are clearly different. (C) 2003 Elsevier B.V. All rights reserved.
• Structural control of silicon oxide particles by oxygen partial pressure in RF plasma

  T Sato, A Takeda, Y Kimura, H Suzuki, Y Saito, C Kaito

  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 42 (9A) 5896 - 5897 0021-4922 2003/09 [Not refereed][Not invited]
   

  Amorphous silicon oxide particles with the size of 30-100 nm were produced by spraying Si(C2H5O)(4) liquid into a plasma region. Plasma was generated at a high pressure of 10 Torr in a mixture gas of argon and oxygen. The production of two silicon oxide particles with the structure of SiO and SiO2 could be controlled by the oxygen partial pressure in plasma.
• Titanium carbide particles as pre-solar grains

  Y. Kimura, C. Kaito

  Monthly Notices of the Royal Astronomical Society 343 (2) 385 - 389 0035-8711 2003/08/01 [Not refereed][Not invited]
   

  Focusing on the growth of metal carbide particles and the formation of pre-solar grains, a new attempt has been made for titanium carbide (TiC) systems. Using the noble gas evaporation method, we succeeded in producing TiC core (50-nm) carbon mantle (2-nm) grains of the same core size as pre-solar grains. The infrared spectrum has broad absorption features at 9.5 and 12.5 μm. It was also found that these absorption peaks became weaker by an increase to 15 nm of carbon mantle layer. The determination method of the contact angle of carbon on the TiC grain has been developed using a high-resolution electron microscopic technique. The contact angles between TiC and carbon were 22°8 ± 0°7 and 24°0 ± 0°4 on the (111) and (100) TiC grain surfaces, respectively.
• Production of nanodiamond from carbon film containing silicon

  Y Kimura, C Kaito

  JOURNAL OF CRYSTAL GROWTH 255 (3-4) 282 - 285 0022-0248 2003/08 [Not refereed][Not invited]
   

  It was shown that nanodiamonds were easily formed from carbon film containing Si. The growth of diamond and beta-Sic. is controllable by adjusting the heating temperature and the proportion of Si. Present result will develop a wide range of new opportunities for research and applications in the field of nanotechnology. (C) 2003 Elsevier Science B.V. All rights reserved.
• Dynamic behavior of Au cluster on the surface of silicon nanoparticles

  Y Kimura, H Ueno, H Suzuki, T Tanigaki, T Sato, Y Saito, C Kaito

  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 19 (3) 298 - 302 1386-9477 2003/08 [Not refereed][Not invited]
   

  The high-temperature behavior of Au clusters on a Si nanoparticle surface has been studied using the atomic-resolution high-temperature stage of a transmission electron microscope. Au atoms diffuse into the Si nanoparticle at 680degreesC and return to the surface at room temperature. The movement of diffused Au atoms on the Si surface steps and the movement of Guinier-Presion-zone-like contrast observed for the segregation of An atoms on the (lll) Si plane, have been directly observed. These phenomena, which can be detected only at high temperatures, are presented in this paper. (C) 2003 Elsevier B.V. All rights reserved.
• Growth process of TiC clusters from Ti nanoparticles with evaporated carbon layer

  A Ikegami, Y Kimura, H Suzuki, T Sato, T Tanigaki, O Kido, M Kurumada, Y Saito, C Kaito

  SURFACE SCIENCE 540 (2-3) 395 - 400 0039-6028 2003/08 [Not refereed][Not invited]
   

  Titanium carbide formation by the solid-solid reaction on the surface of Ti nanoparticles was studied in situ using a high-resolution transmission electron microscope with a heating stage. The cross-sectional image of the Ti surface was clearly observed. Vacuum-deposited carbon covered the whole the surface of Ti nanoparticles in spite of the partly evaporation on the nanoparticle surface. The diffusion of the carbon atoms inside the Ti nanoparticles depended on the size of the nanoparticles. When the Ti nanoparticle diameter was less than 30 nm, carbon atoms diffused into the Ti nanoparticle and formed TiC. The superstructure of the Ti nanoparticles was observed, which revealed the growth process of TiC to be the diffusion of carbon atoms. For Ti nanoparticles with diameter larger than 30 run it was observed that diffusion of Ti atoms into the carbon layer was dominant, which resulted in formation of TiC in the carbon layer at the surface of Ti nanoparticles. (C) 2003 Elsevier B.V. All rights reserved.
• Structure and optical spectrum of ZnO nanoparticles produced in RF plasma

  T Sato, T Tanigaki, H Suzuki, Y Saito, O Kido, Y Kimura, C Kaito, A Takeda, S Kaneko

  JOURNAL OF CRYSTAL GROWTH 255 (3-4) 313 - 316 0022-0248 2003/08 [Not refereed][Not invited]
   

  ZnO particles were produced by dropping Zn powder into a heated boat just below the plasma electrodes in a mixture gas of argon and oxygen. The resulting particles look spherical with the size of 30 nm and were of tetrapod configuration having four [0 0 0 1] axes of ZnO. The dispersion became better than that in the case of another method without plasma. The ultraviolet-visible light transmittance of the specimen showed sharp absorption. The electric charge in the plasma field controlled the coalescence growth of each particle and improved the dispersion of the particles due to the plasma effect. (C) 2003 Elsevier Science B.V. All rights reserved.
• Dynamic behavior of Au cluster on the surface of silicon nanoparticles

  Y Kimura, H Ueno, H Suzuki, T Tanigaki, T Sato, Y Saito, C Kaito

  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 19 (3) 298 - 302 1386-9477 2003/08 [Refereed][Not invited]
   

  The high-temperature behavior of Au clusters on a Si nanoparticle surface has been studied using the atomic-resolution high-temperature stage of a transmission electron microscope. Au atoms diffuse into the Si nanoparticle at 680degreesC and return to the surface at room temperature. The movement of diffused Au atoms on the Si surface steps and the movement of Guinier-Presion-zone-like contrast observed for the segregation of An atoms on the (lll) Si plane, have been directly observed. These phenomena, which can be detected only at high temperatures, are presented in this paper. (C) 2003 Elsevier B.V. All rights reserved.
• In situ observation of silicon carbide formation process using electron microscope

  M Ishikawa, Y Kimura, H Suzuki, O Kida, T Tanigaki, T Sato, Y Saito, C Kaito

  JOURNAL OF CRYSTAL GROWTH 254 (1-2) 131 - 136 0022-0248 2003/06 [Not refereed][Not invited]
   

  The silicon core and carbon mantle particles were produced by using the advanced carbon coating method which enables direct covering with the carbon layer using an electron microscope. The growth of SiC crystal was observed upon heating at 500degreesC in vacuum. The growth process of SiC on both the carbon layer and silicon particles was directly observed by in situ observation. The inward movement of carbon into silicon began at the twinned part. The growth rate of SiC on the carbon mantle layer was estimated from in situ images and found to be 8 times faster than the growth rate of silicon carbide in silicon particles. (C) 2003 Elsevier Science B.V. All rights reserved.
• Characteristic crystal growth from amorphous WO3 film by vacuum heating

  Y Kimura, C Kaito

  JOURNAL OF CRYSTAL GROWTH 250 (3-4) 450 - 457 0022-0248 2003/04 [Not refereed][Not invited]
   

  Selective growth of WO2, W and WO3-x crystals from amorphous WO3 film by vacuum heating at 400-900degreesC was clarified. The grown WO3-x crystals were incommensurate structure based on crystallographic share structure. The growth process of WO2 crystal in the amorphous film was directly observed at high temperature in the electron microscope. The growth front of the WO2 crystal consumes WO3 microcrystallites with various orientations. The growth speed of the WO2 depended on WO3 microcrystallites orientation. The origin of the wavy growth front of WO2 was due to an orientation dependence of the WO3 microcrystallites. (C) 2003 Elsevier Science B.V. All rights reserved.
• Dynamic behavior of a silicon oxide layer on silicon ultrafine particles

  Y Kimura, H Ueno, H Suzuki, T Sato, T Tanigaki, O Kido, C Kaito, Y Saito

  SURFACE REVIEW AND LETTERS 10 (2-3) 361 - 364 0218-625X 2003/04 [Not refereed][Not invited]
   

  In order to clarify the high-temperature behavior of a silicon oxide layer on the surface of Si ultrafine particles, the oxide layer has been studied using the atomic-resolution high-temperature stage of a transmission electron microscope. The natural oxide layer grown on Si ultrafine particles by exposure to air was an amorphous silicon oxide layer with a thickness of 1.5 nm. This oxide layer started to dissolve into the Si crystal upon heating at 500degreesC, and was fully dissolved into the Si crystal at 600degreesC in vacuum. When the specimen was cooled back to room temperature, the silicon oxide layer reappeared on the Si surface. This phenomenon, which can be detected only at high temperatures, is presented in this paper.
• Atomic observation of the sublimation process of the Pb (111) surface

  T Tanigaki, H Suzuki, Y Kimura, C Kaito, Y Saito

  SURFACE REVIEW AND LETTERS 10 (2-3) 455 - 459 0218-625X 2003/04 [Not refereed][Not invited]
   

  The dynamic behavior of the sublimation process using ultrafine Pb particles produced by the gas evaporation technique was examined at the level of atomic resolution using a transmission electron microscope equipped with a real-time video-recording system. The ultrafine Pb particles coated with a carbon layer with a thickness of the order of 5 nm were prepared in the electron microscope by heating particles on carbon film at 300degreesC. Sublimation of the Pb particle covered with the carbon layer took place above 470degreesC, which is slightly higher than the melting point of Pb. Sublimation occurred at the surface with a higher surface energy. The sublimation process of the (111) surface was clearly observed at an atomic level. It was found that two- or four-atomic-layer step flow was observed at the (111) surface. At the (111) surface between the stacking faults, two-layer and successive one-layer sublimation occurred.
• Dynamic process of crystallization of Sb2Se3 from Sb50Se50 amorphous film

  M Kurumada, H Suzuki, Y Kimura, Y Saito, C Kaito

  JOURNAL OF CRYSTAL GROWTH 250 (3-4) 444 - 449 0022-0248 2003/04 [Not refereed][Not invited]
   

  Dynamics of crystallization of amorphous antimony-selenium film deposited on carbon substrate have been studied by the high-resolution transmission electron microscopy. The amorphous film was suddenly crystallized at 200degreesC by heating in vacuum. By the electron beam irradiation crystallization occurred at the focused electron beam region in the amorphous film. The growth process of crystallization by electron beam irradiation was recorded on a video image at the atomic resolution mode. The growth front of crystallization showed nano-concave and -convex shapes. The recrystallization with the different orientation at the first grown crystal have been found, and discussed as the influence of remaining antimony crystallites at the first crystallized film region. (C) 2003 Elsevier Science B.V. All rights reserved.
• Dynamic behavior of a silicon oxide layer on silicon ultrafine particles

  Y Kimura, H Ueno, H Suzuki, T Sato, T Tanigaki, O Kido, C Kaito, Y Saito

  SURFACE REVIEW AND LETTERS 10 (2-3) 361 - 364 0218-625X 2003/04 [Refereed][Not invited]
   

  In order to clarify the high-temperature behavior of a silicon oxide layer on the surface of Si ultrafine particles, the oxide layer has been studied using the atomic-resolution high-temperature stage of a transmission electron microscope. The natural oxide layer grown on Si ultrafine particles by exposure to air was an amorphous silicon oxide layer with a thickness of 1.5 nm. This oxide layer started to dissolve into the Si crystal upon heating at 500degreesC, and was fully dissolved into the Si crystal at 600degreesC in vacuum. When the specimen was cooled back to room temperature, the silicon oxide layer reappeared on the Si surface. This phenomenon, which can be detected only at high temperatures, is presented in this paper.
• Are TiC grains a carrier of the 21 micron emission band observed around post-asymptotic giant branch objects?

  T Chigai, T Yamamoto, C Kaito, Y Kimura

  ASTROPHYSICAL JOURNAL 587 (2) 771 - 776 0004-637X 2003/04 [Refereed][Not invited]
   

  The carrier of the 21 mum band observed in post-asymptotic giant branch (post-AGB) stars is examined. We analyze the infrared spectra of the TiC clusters measured by von Helden et al. in 2000 and determine the absorption efficiency Q in the 21 mum band. Using Q, we estimate the Ti/Si abundance ratios needed to realize the flux ratios of the 21 and 11 mum emission observed in the infrared spectra of the post-AGB stars exhibiting both 21 and 11 mum emission. In view of the nature of the TiC condensation by which TiC grains are quickly mantled by graphite, we calculate the emission spectra of the graphite-coated TiC grains and other possible types of core-mantle grains and compare with the observed spectra. Both the abundance and condensation considerations strongly suggest that TiC is an implausible carrier of the observed infrared 21 mum feature around carbon-rich post-AGB stars.
• High-temperature behavior of an amorphous carbon layer on SiC particles

  Y Kimura, Y Saito, C Kaito

  SURFACE SCIENCE 527 (1-3) L219 - L221 0039-6028 2003/03 [Not refereed][Not invited]
   

  The dynamic behavior of an amorphous carbon layer of 3 nm thickness on a SiC particle was examined at high temperature using a high-resolution electron microscope equipped with a real-times video recording system. It was found that the surface carbon layer began to solve into the SiC particle at 600 degreesC. The layer was completely solved into SiC crystal at 800 degreesC. The lattice image of SiC changed negligibly at high temperature. If the specimen was cooled back to room temperature, the carbon layer on the SiC particle was recovered. (C) 2002 Elsevier Science B.V. All rights reserved.
• Novel method for the preparation of silicon oxide layer on TiO2 particle and dynamic behavior of silicon oxide layer on TiO2 particle

  Y Atou, H Suzuki, Y Kimura, T Sato, T Tanigaki, Y Saito, C Kaito

  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 16 (2) 179 - 189 1386-9477 2003/02 [Not refereed][Not invited]
   

  Two methods for the preparation of TiO2 particles using the gas evaporation methods have been proposed. A method for selective growth of the anatase and/or rutile particles as well as a method of covering TiO2 particles with an SiO2 layer has been developed. The process of dissolving the SiO2 layer into TiO2 particles has been observed by an in situ observation using high-resolution electron microscopy. SiO2 layers of 5 nm order were dissolved completely into TiO2 particles of the order of 30 nm at 750degreesC. These SiO2 layers appeared again at room temperature on the surfaces of TiO2 particles. This phenomenon was observed only at a high temperature. By the use of the phenomenon of dissolving the SiO2 layer into TiO2 particles at high temperature, the growth of TiO2 particles covered with the SiO2 layer has been discussed. (C) 2002 Elsevier Science B.V. All rights reserved.
• Characteristic behavior of Bi clusters and growth process to the continuous film

  C Kaito, Y Kimura, S Tominaga, S Kimura, T Nakada, Y Saito

  PHYSICS OF LOW-DIMENSIONAL STRUCTURES 5-6 1 - 7 0204-3467 2003 [Not refereed][Not invited]
   

  The instability of the Bi cluster predicted on the surface of amorphous carbon substrate under electron beam observation has been captured in high-resolution electron microscope video images, which indicates the intuitive nature of the cluster. It is also shown that the intuitive nature of the clusters is important for the growth process of the film. With the changing of the film thickness up to 15 nm, the marked changes in the growth orientation have been observed.
• Are TiC grains a carrier of the 21-μm emission band observed around the post-AGB objects?

  T. Chigai, T. Yamamoto, C. Kaito, Y. Kimura

  The Astrophysical Journal 587 (2) 771 - 776 2003 [Not refereed][Not invited]
  
• Demonstration of crystalline forsterite grain formation due to coalescence growth of Mg and SiO smoke particles

  C Kaito, Y Ojima, K Kamitsuri, O Kido, Y Kimura, H Suzuki, T Sato, T Nakada, Y Saito, C Koike

  METEORITICS & PLANETARY SCIENCE 38 (1) 49 - 57 1086-9379 2003/01 [Not refereed][Not invited]
   

  Experimental studies of coalescence between Mg grains and SiO grains in smoke reveal the direct production of crystalline forsterite grains. The present results also show that different materials can be produced by grain-grain collisions, which have been considered one of the models of grain formation in the interstellar medium. The fundamentals of coalescence growth in smoke, which have been developed in our series of experiments, are presented in this paper. Mg2Si polyhedral grains were obtained in a Mg grain-rich atmosphere. Mg2SiO4 polyhedral grains were obtained in a SiO grain-rich atmosphere. The IR spectra of the resultant grains showed the characteristics of crystalline forsterite.
• Diffusion Constant of Hydrogen Atoms in H2O + CO Ice

  Kimura, Y, Chigai, T, Yamamoto, T, Shalabiea, O. M, Awad, Z

  Proceedings of the 36th ISAS Lunar and Planetary Symposium 254 - 257 2003 [Not refereed][Not invited]
  
• Alteration of interstellar organic materials in meteorites' parent bodies: a novel route for diamond formation

  H Nakano, A Kouchi, M Arakawa, Y Kimura, C Kaito, H Ohno, T Hondoh

  PROCEEDINGS OF THE JAPAN ACADEMY SERIES B-PHYSICAL AND BIOLOGICAL SCIENCES 78 (9) 277 - 281 0386-2208 2002/11 [Not refereed][Not invited]
   

  Based on experiments that model interstellar organic materials, we found that both C and N contents and IR spectra of insoluble organic materials in carbonaceous chondrites could be reproduced well by the aqueous alteration and the subsequent thermal metamorphism. The resulting sample shows strong evidence of diamond, which indicates that this process is an unexpected mechanism that might produce extensive amount of diamond in meteorites' parent bodies. Because this process requires neither high pressures nor energetic processes, the present results suggest an alternate origin of diamonds in meteorites.
• Fabrication of an amorphous carbon tube from copper oxide whisker

  H Suzuki, N Fukuzawa, T Tanigaki, T Sato, O Kido, Y Kimura, C Kaito

  JOURNAL OF CRYSTAL GROWTH 244 (2) 168 - 172 0022-0248 2002/10 [Not refereed][Not invited]
   

  The reduction process of tenorite whiskers grown on a copper mesh by heating in vacuum has been directly observed using a transmission electron microscope equipped with a real-time video-recording system. The coating of the carbon layer and reduction of the tenorite whisker covered with a carbon layer have also been captured in real time on video images. The growth process of an amorphous carbon tube has been elucidated. (C) 2002 Elsevier Science B.V. All rights reserved.
• Irradiation effect of synchrotron radiation on crystallization of thin amorphous WO3 film

  Y Kimura, K Hanamoto, Y Nakayama, C Kaito

  NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 194 (2) 187 - 192 0168-583X 2002/08 [Not refereed][Not invited]
   

  In order to elucidate the effect of synchrotron radiation (SR) irradiation on crystal growth, crystallization of WO3 films has been performed in vacuum under SR irradiation. The main results were compared with the results of heat treatment of the same film. Upon SR irradiation for 80 s using a toroidal mirror, a catastrophic change occurred, i.e. W3O crystals (A-15 type) with a size of less than 30 nm appeared. Decomposition of the WO3 film started at above 750 degreesC during vacuum heating. W, WO2 and incommensurate WO3 crystals appeared. W3O crystal produced neither intense electron beam irradiation nor vacuum heating. These results will be discussed in terms of the differences caused by excitation with a SR beam, i.e. strong inner shell excitation and ionization of W and O may have taken place. (C) 2002 Elsevier Science B.V. All rights reserved.
• Process of crystallization in thin amorphous tin oxide film

  T Kobayashi, Y Kimura, H Suzuki, T Sato, T Tanigaki, Y Saito, C Kaito

  JOURNAL OF CRYSTAL GROWTH 243 (1) 143 - 150 0022-0248 2002/08 [Not refereed][Not invited]
   

  Amorphous tin oxide films deposited on carbon substrates have been studied by high-resolution transmission electron microscopy. As-deposited film was composed of a mixture of microcrystallites of SnO, SnO2 and SnO3 with size of 2 nm. Crystallization took place above 450degreesC. SnO crystals appeared between 450degreesC and 500degreesC, whereas SnO2 crystals appeared above 550degreesC. The appearance of beta-tin crystals with the reduction of tin oxide has been verified using the heating stage of the electron microscope. A drop of liquid tin was recognized upon heating above 500degreesC. The difference in crystallization upon applying an electron beam, synchrotron radiation and heating in vacuum has been summarized and discussed with respect to the problem of the excitation of crystallites. (C) 2002 Elsevier Science B.V. All rights reserved.
• Aqueousalteration and thermal metamorphism of interstellar organic materials on the parent bodies ofcarbonaceous chondrites

  Hideyuki NAKANO, Akira KOUCHI, Masahiko ARAKAWA, Yuki KIMURA, Chihiro KAITO, Hiroshi OHNO, Takeo HONDOH

  Proceedings of the 35th ISAS Lunar and Planetary Symposium 宇宙科学研究所 183 - 186 2002/08 [Not refereed][Not invited]
  
• Effects of SR irradiation on tin-doped indium oxide thin film prepared by rf magnetron sputtering

  M Sasaki, K Hanamoto, Y Kimura, C Kaito, H Miki, Y Nakayama

  REVIEW OF SCIENTIFIC INSTRUMENTS 73 (3) 1384 - 1386 0034-6748 2002/03 [Not refereed][Not invited]
   

  The effects of synchrotron radiation (SR) irradiation on the electrical properties of tin-doped In2O3 (ITO) thin films prepared by rf magnetron sputtering have been studied. A white SR beam focused by a cylindrical mirror was used to irradiate ITO thin films at doses of 0.35, 1.98, 3.50, and 6.64 mA h. We have achieved resistivity of 2x10(-4) Omega cm on ITO thin film at an irradiation dose of 3.5 mA h without extra heating. The mobility of the ITO films did not decrease after SR irradiation. The electrical properties in connection with the structural change due to SR are discussed. (C) 2002 American Institute of Physics.
• Spontaneous mixing of binary alkali halide crystal by successive evaporation

  Y Kimura, Y Saito, T Nakada, C Kaito

  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 13 (1) 11 - 23 1386-9477 2002/01 [Not refereed][Not invited]
   

  Experimental studies on the mixing of alkali halide clusters of 200 nm sizes were performed systematically by the successive evaporation of different alkali halides on carbon substrates. The alkali halides used were NaCl, NaBr, KCl, KBr, KI, RbCl, RbBr, CsCl and CsBr. Intermixing took place independent of the crystal structure. It became evident that the limit of mixing was governed by the ratio of ionic radii. If the ratio of ionic radii between the cation and/or anion was more than 68%, intermixing occurred. It was also found that the crystal structure formed by intermixing between NaCl-type and CsCl-type structures becomes the NaCl type. If four different elements of cations and anions are involved, two mixture phases grew. The key elements of mixing were the nearest ionic radii. (C) 2002 Elsevier Science B.V. All rights reserved.
• Growth process of carbyne crystals by synchrotron irradiation

  Y Kimura, C Kaito, K Hanamoto, M Sasaki, S Kimura, T Nakada, Y Saito, Y Nakayama

  CARBON 40 (7) 1043 - 1050 0008-6223 2002 [Not refereed][Not invited]
   

  Growth of small carbyne crystals in a thin amorphous carbon film has been observed by high-resolution transmission electron microscopy (HRTEM). The as-deposited film was composed of diamond and graphite crystallites of size 1 nm. Circular alpha-phase carbyne crystals predominantly grew to 20 nm in size and transformed into (alpha+beta)-phase crystals with an elongated shape of 100 nm in length. The typical correlation during the transformation is (220)(alpha)//(301)((alpha+beta)) The c-axes of both grown crystals were oblique to the direction of the electron beam. The growth process of carbyne crystals will be discussed in terms of selective excitation of graphite crystallites by an SR beam. (C) 2002 Elsevier Science Ltd. All rights reserved.
• Crystallization and selective growth of amorphous Y-Ba-Cu-O film

  T. Tanigaki, S. Ariumi, H. Suzuki, Y. Kimura, S. Kimura, T. Sato, N. Tsuda, T. Nakada, Y. Saito, C. Kaito

  Physics of Low-Dimensional Structures 11/12 77 - 84 2002 [Not refereed][Not invited]
  
• Ordered alloy formation by the use of reaction between ultrafine particle and cluster

  T Tsurusako, T Tanigaki, H Suzuki, Y Kimura, T Sato, O Kido, Y Saito, C Kaito

  PHYSICS OF LOW-DIMENSIONAL STRUCTURES 7-8 77 - 86 0204-3467 2002 [Not refereed][Not invited]
   

  To observe the singularity of clusters and ultrafine particles in low dimensions, a new experiment has been started on the Au-Cu system. The diffusion of atoms in the cluster and ultrafine particles has been observed including the direct observation at the interface. The alloy formation temperature decreases by about 50degreesC compared with the film-ultrafine particle. The diffusion rate difference observed in bulk phase is preserved in the alloy formation process.
• A new-attempt on reduction of ultrafine oxide particles

  H Suzuki, T Tanigaki, T Sato, O Kido, Y Atou, Y Kimura, C Kaito

  PHYSICS OF LOW-DIMENSIONAL STRUCTURES 7-8 99 - 105 0204-3467 2002 [Not refereed][Not invited]
   

  A method to coat the surface of ultrafine particles by an amorphous carbon layer was developed and a characteristic reduction of the ultrafine particles has been observed for WO3 ultrafine particles. The carbon layer formation and the reduction process have been observed in situ in a transmission electron microscope. The growth of the carbon layer predominately occurred upon heating at 200degreesC by using a heating stage. The characteristic graphitization of the carbon layer took place at about 400degreesC. The characteristic gap formation at the interface of the carbon layer and WO3 particles started at about 400degreesC. The reduction indicates that a, reaction between 0 and C atoms occurred and CO or CO2 gas evaporated into vacuum during the observation. The WO3, particles with the gap between carbon layers were also reduced.
• Growth process of carbyne crystals by synchrotron irradiation

  Y Kimura, C Kaito, K Hanamoto, M Sasaki, S Kimura, T Nakada, Y Saito, Y Nakayama

  CARBON 40 (7) 1043 - 1050 0008-6223 2002 [Refereed][Not invited]
   

  Growth of small carbyne crystals in a thin amorphous carbon film has been observed by high-resolution transmission electron microscopy (HRTEM). The as-deposited film was composed of diamond and graphite crystallites of size 1 nm. Circular alpha-phase carbyne crystals predominantly grew to 20 nm in size and transformed into (alpha+beta)-phase crystals with an elongated shape of 100 nm in length. The typical correlation during the transformation is (220)(alpha)//(301)((alpha+beta)) The c-axes of both grown crystals were oblique to the direction of the electron beam. The growth process of carbyne crystals will be discussed in terms of selective excitation of graphite crystallites by an SR beam. (C) 2002 Elsevier Science Ltd. All rights reserved.
• Characterization and selective growth of amorphous Y-Ba-Cu-O film

  T Tanigaki, S Ariumi, H Suzuki, Y Kimura, S Kimura, T Sato, N Tsuda, T Nakada, Y Saito, C Kaito

  PHYSICS OF LOW-DIMENSIONAL STRUCTURES 11-2 77 - 84 0204-3467 2002 [Refereed][Not invited]
   

  Amorphous Y-Ba-Cu-O films prepared by Ar ion sputtering at room temperature have been studied by high-resolution transmission electron microscopy (HRTEM). As-deposited film was composed of a mixture of microcrystallites of YBa2Cu3Ox, YBa2Cu4Ox, Y2BaCuOx, and Y2Ba4Cu7Ox phases with the size of 3-5 nm. The produced film was crystallized above 300degreesC by heating in air. The selective crystal growth of the above four phases was observed upon heating up to 600degreesC, which was a lower temperature than the general epitaxial growth temperature of Y-Ba-Cu-O film.
• Effect of SR irradiation on crystallization of amorphous tin oxide film

  Y Kimura, T Kobayashi, K Hanamoto, M Sasaki, S Kimura, T Nakada, Y Nakayama, C Kaito

  NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 467 1221 - 1224 0168-9002 2001/07 [Not refereed][Not invited]
   

  In order to see the effect of SR irradiation on crystal growth., crystallization of tin oxide films has been performed in vacuum under SR irradiation, A thin amorphous tin oxide film 50 nm thick was prepared on the carbon substrate by vacuum evaporation of SnO2 power, A SnO crystal appeared between 450-500 degreesC upon vacuum heating, with a preferred orientation of (0 0 1). By SR irradiation using a cylindrical mirror for 20 s, the SnO crystal appeared with the preferred orientation of (1 1 1). The crystal with the crystallographic shear structure was grown by SR irradiation. This growth under a SR beam is discussed in terms of SR beam excitation of lone-pair electrons seen in the SnO crystal structure. (C). 2001 Elsevier Science B.V. All rights reserved.
• Carbyne formation by synchrotron radiation

  C Kaito, Y Kimura, K Hanamoto, M Sasaki, S Kimura, T Nakada, Y Saito, C Koike, Y Nakayama

  NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 467 1217 - 1220 0168-9002 2001/07 [Not refereed][Not invited]
   

  Thin carbon films prepared by vacuum evaporation using the arc method were mounted on a standard electron microscope copper grid. They were irradiated by white synchrotron radiation (SR) beam by the use of cylindrical and toroidal mirrors. The irradiated film was examined using a high-resolution electron microscope alpha and alpha + beta mixture carbyne crystals were grown in round and the elongated shapes. The round crystals were composed of 5-10 nm crystallites of a carbyne form. The elongated crystal grew into a single crystal 100 nm in size. The c-axes of both grown crystals were oblique to the film. The growth of the carbynes was discussed as being the result of nucleation due to graphite microcrystallites formed by SR beam irradiation. (C) 2001 Elsevier Science B.V. All rights reserved.
• Effect of SR irradiation on In2O3 film

  K Hanamoto, A Hirai, M Sasaki, Y Kimura, K Miyatani, C Kaito, Y Nakayama

  NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 467 1213 - 1216 0168-9002 2001/07 [Not refereed][Not invited]
   

  The effect of SR irradiation on the crystal growth of indium oxide films prepared by electron-beam evaporation have been studied by X-ray diffraction and high-resolution electron microscopy. An as-deposited film showed In2O3 crystallites with a size of 2-10 nm. The crystallites were destroyed by SR irradiation under oxygen flow, SR irradiation without oxygen flow showed the growth of In2O3 crystallites up to 20 nm in size with accompanying deoxidation and indium-particle growth. The as-deposited film was composed of variously oriented particles. Periodic oxygen decomposition of the film preferentially took place on the (0 0 1)-oriented particle. (C) 2001 Elsevier Science B.V. All rights reserved.
• Topotactical growth of indium sulfide by evaporation of metal onto molybdenite

  C Kaito, A Ito, S Kimura, Y Kimura, Y Saito, T Nakada

  JOURNAL OF CRYSTAL GROWTH 218 (2-4) 259 - 264 0022-0248 2000/09 [Not refereed][Not invited]
   

  The growth of In2S3 and InS by vacuum evaporation of indium metal on the surface of molybdenite has been observed in the initial stage of film growth. By the increment of In2S3 particle size, InS was also produced. By the increase of the film thickness to more than 20 nm, indium crystal predominately grew. The topotactic relations among the substrate and sulfide are as follows: (0 0 0 1)(MoS2) parallel to(1 1 0)(In2S3), [1 0 (1) over bar 0](MoS2) parallel to[1 1 1](In2S3) or (0 0 0 1)(MoS2) parallel to(1 1 0)(In2S3), [1 0 (1) over bar 0](MoS2) parallel to[1 0 0](In2S3). (C) 2000 Elsevier Science B.V. All rights reserved.
• Characterization of indium tin oxide film and practical ITO film by electron microscopy

  T Nakao, T Nakada, Y Nakayama, K Miyatani, Y Kimura, Y Saito, C Kaito

  THIN SOLID FILMS 370 (1-2) 155 - 162 0040-6090 2000/07 [Not refereed][Not invited]
   

  In order to clarify the structure of indium oxide him containing tin and tin oxides, various In2O3 based films prepared by vacuum evaporation were studied using high-resolution electron microscope (HREM). Indium tin oxide (ITO) film was composed of In2O3 and SnO. SnO crystal also contained (110) or (101) crystallographic shear (CS) structures that indicate excess amounts of tin. The CS structure was also found in a commercial ITO film having the resistivity of 2 x 10(-4) Omega cm. (C) 2000 Elsevier Science S.A. All rights reserved.
• Spontaneous alkali halide formation by the use of KBr-KCl system

  Y Kimura, Y Saito, T Nakada, C Kaito

  PHYSICS OF LOW-DIMENSIONAL STRUCTURES 1-2 L1 - L7 0204-3467 2000 [Not refereed][Not invited]
   

  Mixing of the KBr-KCl system obtained by successive evaporation has been studied by electron microscopy. Evaporation was done on amorphous carbon film at room temperature. The spontaneous mixture particles have been observed with various ratios by controlling the mean film thickness. The spontaneous mixture occurs at 200 nm size that is a hundred times larger than in the metallic alloy system.
• The structure of thin Cr film prepared by the vacuum evaporation method

  C Kaito, H Nakamura, S Kimura, Y Kimura, T Nakada, Y Saito

  THIN SOLID FILMS 359 (2) 283 - 287 0040-6090 2000/01 [Not refereed][Not invited]
   

  In order to clarify the structures of thin Cr films by their real space images, Cr films of various thicknesses, prepared using vacuum deposition, have been observed using a high resolution electron microscope. The amorphous chromium films were composed of microcrystallites of the order of 3 nm. The crystallite structure was delta-Cr. The well-known bcc chromium particles were observed in thick and large crystal particles. The stability of small particles is discussed. (C) 2000 Published by Elsevier Science S.A. All rights reserved.
• The structure of thin Cr film prepared by the vacuum evaporation method

  C Kaito, H Nakamura, S Kimura, Y Kimura, T Nakada, Y Saito

  THIN SOLID FILMS 359 (2) 283 - 287 0040-6090 2000/01 [Refereed][Not invited]
   

  In order to clarify the structures of thin Cr films by their real space images, Cr films of various thicknesses, prepared using vacuum deposition, have been observed using a high resolution electron microscope. The amorphous chromium films were composed of microcrystallites of the order of 3 nm. The crystallite structure was delta-Cr. The well-known bcc chromium particles were observed in thick and large crystal particles. The stability of small particles is discussed. (C) 2000 Published by Elsevier Science S.A. All rights reserved.
• Surface oxide on tin and indium ultrafine particles and their oxidation process

  C Kaito, T Nakao, Y Ato, Y Kimura, S Kimura, T Nakada, Y Saito

  PHYSICS OF LOW-DIMENSIONAL STRUCTURES 12 53 - 60 0204-3467 1999 [Not refereed][Not invited]
   

  The structure of surface oxide on tin and indium metallic particles and their oxidation process at a temperature higher than the melting point of the particles have been elucidated on the basis of observations using a high-resolution electron microscope (HREM). In the case of tin particles, the surface oxide layer spontaneously produced by exposure to air was composed of microcrystallites with the size of 1 similar to 2 nm. In the case of indium, the (222) crystal of In2O3 covered the surface of indium particles. In the oxidation of tin at a temperature higher than its melting point, crystal shear structure which were present as the metal-excess Sn3O2 or Sn4O3 oxides have been found. In the case of indium particles, a definite crystallographic correlation, i.e., In2O3 (111) // In(110), has also been observed during the solidification of central metal. The fundamental behaviors of low-dimensional In and Sn particles can be observed.
• LOCAL DIELECTRIC-PROPERTIES AROUND POLAR-REGION OF LIPID BILAYER-MEMBRANES

  Y KIMURA, A IKEGAMI

  JOURNAL OF MEMBRANE BIOLOGY 85 (3) 225 - 231 0022-2631 1985 [Refereed][Not invited]
  

MISC

• Phoenix "Hayabusa": A tale of the future (30) - Scientific results from the Ryugu "Stone" analysis team -

  Nakamura T., Amano K., Matsuoka M., Kurosawa K., Ninomiya K., Osawa T., Kimura Y., Genda H., Tanaka S., Initial analysis Stone team  Planetary People - The Japanese Society for Planetary Sciences  32-  (3)  226  -235  2023/09  

  初期分析「石」分析チームではリュウグウのミリメータサイズのサンプル（探査機が2回目のタッチダウンで採集した最大サンプルを含む17粒子）を日米欧の放射光施設，ミュオン施設などを利用し物質分析を行った[1]．その結果，リュウグウ母天体の原始惑星系円盤内での形成位置，集積物質の岩石鉱物学的情報，集積した氷の種類，天体内部での水との反応による化学進化，天体衝突の影響について知見が得られた．リュウグウサンプルには，水岩石反応の進行度が異なる物質が混在していることが判明した．リュウグウサンプルの物性（破壊強度，熱拡散係数，比熱，密度など）を実測した．この実測値を使って，リュウグウ母天体形成後の天体内部の加熱による温度経時変化，および衝突破壊プロセスの数値シミュレーションを行い，リュウグウの形成進化を再現した．
• 観測ロケットによる微小重力実験で見られた非古典的核生成経由のダスト形成

  木村勇気, 稲富裕光, 田中今日子, 齋藤史明, 千貝健, 森章一, 中坪俊一, 竹内伸介, AKTAS Coskun, BLUM Juergen  日本惑星科学会秋季講演会予稿集(Web)  2023-  2023
• 航空機を用いた微小重力環境下における氷ナノ粒子の核生成実験の速報—Preliminary Results of Nucleation Experiments of Ice Nanoparticles in Microgravity Using an Aircraft

  木村, 勇気, 山﨑, 智也, 屋嶋, 悠河, 中埜, 夕希, 森, 章一, 稲富, 裕光, KIMURA, Yuki, YAMAZAKI, Tomoya, YASHIMA, Yuga, NAKANO, Yuki, MORI, Shoichi, INATOMI, Yuko  宇宙環境利用シンポジウム 第37回： 令和四年度 = Space Utilization Research, Vol. 37 2022: Proceedings of The Thirty-seventh Space Utilization Symposium  2023/01  

  第37回宇宙環境利用シンポジウム (2023年1月17日-18日. オンライン開催) Space Utilization Research (January 17-18, 2023. Online Meeting) 資料番号: SA6000180005 F-4
• Nucleation pathway by detection of nucleation of LC-TEM image using machine learning

  勝野弘康, 木村勇気, 山崎智也, 瀧川一学, 瀧川一学  日本物理学会講演概要集(CD-ROM)  77-  (2)  2022
• Investigation of formation efficiency of silica nanoparticles for understanding the formation process of circumstellar dust

  木村勇気, 田中今日子, 稲富裕光, 稲富裕光, FERGUSON Frank T., FERGUSON Frank T., NUTH Joseph A.,III  結晶成長国内会議予稿集(CD-ROM)  51st-  2022
• Homogeneous nucleation experiments of silicate nanoparticles under microgravity environment in global cooperation

  木村勇気, NUTH Joseph A., FERGUSON Frank T., 斎藤史明, 中坪俊一, 千貝健, 森章一, 稲富裕光  日本物理学会講演概要集(CD-ROM)  75-  (1)  2020
• Preparation for nucleation experiment of ice nanoparticles by the low-temperature gas evaporation method under microgravity condition

  Kimura Yuki, Kouchi Akira, Yamazaki Tomoya, Satoh Yosuke, Saito Fumiaki, Inatomi Yuko  宇宙環境利用シンポジウム 第34回： 令和元年度 = Space Utilization Research, Vol. 34 2019: Proceedings of The Thirty-fourth Space Utilization Symposium  (34)  2020/01  

  Space Utilization Research (January 21-22, 2020. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)), Sagamihara, Kanagawa JapanE-04
• 国際協力による微小重力環境下での炭化チタン粒子の均質核生成実験

  木村勇気, 斎藤史明, 中坪俊一, 千貝健, 森章一, 稲富裕光  日本物理学会講演概要集(CD-ROM)  74-  (2)  2019
• Elucidate of the formation processes of presolar TiC grains by nucleation experiment from a vapor phase

  木村勇気, 稲富裕光, 稲富裕光, 斎藤史明, 中坪俊一, 千貝健, 森章一  結晶成長国内会議予稿集(CD-ROM)  48th-  2019
• アモルファスMg₂SiO₄微粒子を覆った氷の光化学反応によるフォルステライト結晶の生成

  香内晃, 木村勇気, 大場康弘, 羽馬哲也, 渡部直樹, 橘省吾, 土山明, 延寿里美, 大坪貴文  日本地球惑星科学連合大会予稿集(Web)  2019-  2019
• 宇宙環境曝露実験によって探る炭素質星間塵の性質

  左近樹, 池内綾人, 遠藤いずみ, 尾中敬, 木村誠二, 木村勇気, 中村正人, 市村淳, 藪田ひかる, 小川奈々子, 大河内直彦, 稲富裕光, 和田節子  日本天文学会年会講演予稿集  2018-  2018
• The effect of exposure to the space environment on the infrared properties of carbon and silicate dust

  遠藤いずみ, 左近樹, 尾中敬, 木村勇気, 木村誠二, 中村正人, 市村淳, 稲富裕光, 和田節子  宇宙科学技術連合講演会講演集(CD-ROM)  62nd-  2018
• 観測ロケットを用いた微小重力環境下でのダスト生成過程の再現実験

  木村勇気, NUTH Joseph, BLUM Jurgen, 石塚紳之介, 田中今日子, 野沢貴也, 左近樹, 田中秀和, 木村宏, 山崎智也, 渡部直樹, 香内晃, STURM Saso, VELU Nirmal Kuma, 竹内伸介, 松原英雄, 稲富裕光  日本惑星科学会秋季講演会予稿集(Web)  2018-  2018
• 国際宇宙ステーション「きぼう」利用 簡易曝露実験装置ExHAMを利用した炭素質ダストの宇宙曝露実験(3)

  左近樹, 尾中敬, 木村誠二, 木村勇気, 中村正人, 市村淳, 小川奈々子, 大河内直彦, 稲富裕光, 和田節子  日本天文学会年会講演予稿集  2017-  2017
• The Effect of Exposure of Carbonaceous Dust Samples to the Space Environment

  左近樹, 池内綾人, 遠藤いずみ, 尾中敬, 木村勇気, 木村誠二, 中村正人, 市村淳, 稲富裕光, 小川奈々子, 大河内直彦, 薮田ひかる, 和田節子  宇宙科学技術連合講演会講演集(CD-ROM)  61st-  2017
• Elucidating the early processes of cosmic dust formation based on microgravity experiments using aircrafts

  Kimura Yuki, Ishizuka Shinnosuke, Sturm Saso, Tanaka Kyoko K., Yamazaki Tomoya, Saito Fumiaki, Satoh Yosuke, Inatomi Yuko  宇宙環境利用シンポジウム 第31回： 平成28年度 = Space Utilization Research, Vol. 31 2016: Proceedings of The Thirty-first Space Utilization Sysmposium  (31)  2017/01  

  Space Utilization Research (January 16-17, 2017. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)), Sagamihara, Kanagawa Japan
• QCCプロジェクト進捗報告 : 曝露実験試料の現状—Latest Progress Report on the QCC Project : Status of Exposure Experiment Samples

  左近 樹, 尾中 敬, 木村 勇気, 木村 誠二, 中村 正人, 市村 淳, 稲富 裕光, 小川 奈々子, 大河内 直彦, 和田 節子  宇宙科学技術連合講演会講演集  60-  4p  2016/09
• Nucleation experiment of alumina and silica from vapor phase using the sounding rocket S-520-30

  KIMURA Yuki, ISHIZUKA Shinnosuke, YAMAZAKI Tomoya, TANAKA Kyoko, TAKEUCHI Shinsuke, INATOMI Yuko  日本地球惑星科学連合大会予稿集(Web)  2016-  2016
• In-situ IR measurement in homogeneous nucleation process of alumina under μG environment

  ISHIZUKA Shinnosuke, KIMURA Yuki, YAMAZAKI Tomoya, SAKON Itsuki, INATOMI Yuko  日本地球惑星科学連合大会予稿集(Web)  2016-  2016
• 国際宇宙ステーション「きぼう」利用簡易曝露実験装置ExHAMを利用した炭素質ダストの宇宙環境曝露実験(2)

  左近樹, 尾中敬, 木村誠二, 木村勇気, 中村正人, 市村淳, 小川奈々子, 大河内直彦, 稲富裕光, 和田節子  日本天文学会年会講演予稿集  2016-  2016
• QCCプロジェクト進捗報告~曝露実験試料の現状

  左近樹, 尾中敬, 木村勇気, 木村誠二, 中村正人, 市村淳, 稲富裕光, 小川奈々子, 大河内直彦, 和田節子  宇宙科学技術連合講演会講演集(CD-ROM)  60th-  2016
• Microgravity experiments using S-520 sounding rockets to elucidate formation process of cosmic dust

  Kimura Yuki, Ishizuka Shinnosuke, Nakatsubo Shunichi, Saito Fumiaki, Yamazaki Tomoya, Sakon Itsuki, Takeuchi Shinsuke, Inatomi Yuko  第16回宇宙科学シンポジウム 講演集 = Proceedings of the 16th Space Science Symposium  2016/01  

  16th Space Science Symposium (January 6-7, 2016. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)Sagamihara Campus), Sagamihara, Kanagawa Japan
• Reproduction experiment of cosmic dust particles using the Sounding rocket S-520-30

  Kimura Yuki, Ishizuka Shinnosuke, Nakatsubo Shunichi, Saito Fumiaki, Yamazaki Tomoya, Sakon Itsuki, Takeuchi Shinsuke, Inatomi Yuko  宇宙環境利用シンポジウム 第30回： 平成27年度 = Space Utilization Research, Vol. 30 2015: Proceedings of The Thirtieth Space Utilization Symposium  (30)  2016/01  

  Space Utilization Research (January 19-20, 2016. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)), Sagamihara, Kanagawa Japan
• Account of "32nd Grain Formation Workshop"

  Kimura Y, Tanaka K. K, Honda M, Sakon I, Miura H  Planetary People - The Japanese Society for Planetary Sciences  25-  (1)  21  -23  2016  [Not refereed][Not invited]
  
• 低温光化学反応による分子雲での有機物形成・進化

  Piani Laurette, 橘 省吾, 羽馬 哲也, 菅原 いよ, 大場 康弘, 田中 秀和, 木村 勇気, 三宅 亮, 松 野 淳也, 土山 明, 圦本 尚義, 香内 晃  日本地球惑星科学連合2016年大会  2016  [Not refereed][Not invited]
  
• Experimental results of sounding rocket S-520-30 and future plan

  Kimura Yuki, Ishizuka Shinnosuke, Nakatsubo Shunichi, Sakon Itsuki, Takeuchi Shinsuke, Inatomi Yuko  大気球シンポジウム: 平成27年度 = Balloon Symposium: 2015  2015/11  

  Balloon Symposium 2015 (November 5-6, 2015. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan
• PHOTOCHEMISTRY IN MOLECULAR CLOUDS: STRUCTURE AND PHYSICAL PROPERTIES OF ORGANIC RESIDUES AND ICE AND SUBLIMATION OF VOLATILE MOLECULES.

  S. Tachibana, L. Piani, L. Dessimoulie, T. Hama, Y. Kimura, Y. Endo, K. Fujita, S. Nakatsubo, H. Fukushi, S. Mori, T. Chigai, H. Yurimoto, A. Kouchi  METEORITICS & PLANETARY SCIENCE  50-  2015/08  [Not refereed][Not invited]
  
• Report on the 31st Grain Formation Workshop

  Honda M., Sakon I., Kimura Y., Miura H., Shimonishi T.  Planetary People  24-  (1)  60  -62  2015/03
• ISS「きぼう」日本実験棟ExHAMを利用したダストの宇宙曝露実験計画

  左近樹, 尾中敬, 木村誠二, 和田節子, 木村勇気, 中村正人, 市村淳, 小川奈々子, 大河内直彦, 稲富裕光, 佐藤一輝, 島本早也佳, 渡辺英幸, 赤城弘樹, 佐巻義昭  日本天文学会年会講演予稿集  2015-  2015
• 国際宇宙ステーション「きぼう」利用簡易曝露実験装置ExHAMを利用した炭素質ダストの宇宙環境曝露実験

  左近樹, 尾中敬, 木村誠二, 和田節子, 木村勇気, 中村正人, 市村淳, 小川奈々子, 大河内直彦, 稲富裕光, 渡辺英幸, 赤城弘樹, 杉紀夫  日本天文学会年会講演予稿集  2015-  2015
• 炭素質ナノ粒子の宇宙風化と星間有機物進化の実証研究

  左近樹, 尾中敬, 木村勇気, 木村誠二, 中村正人, 市村淳, 稲富裕光, 小川奈々子, 大河内直彦, 渡辺英幸, 赤城弘樹, 杉紀夫, 和田節子  宇宙科学技術連合講演会講演集(CD-ROM)  59th-  2015
• 様々な手法を用いた非晶質珪酸塩薄膜の生成実験

  土`山明, 三宅亮, 羽馬哲也, 橘省吾, 寺崎英紀, 近藤忠, 安達裕, 日高宏, 渡部直樹, 木村勇気, 香内晃  日本鉱物科学会2015年年会  2015  [Not refereed][Not invited]
  
• P1-38 浮遊法による全溶融した放射状輝石コンドリュールの再現実験(ポスターセッション1,ポスター発表)

  野村 逸郎, 中村 智樹, 木村 勇気, 塚本 勝男  日本惑星科学会秋期講演会予稿集  2014-  "P1  -38"  2014/09/10
• O10-03 タギシュレイク隕石中に見られるフランボイダルマグネタイトの形成過程(口頭発表セッション10 隕石・実験,口頭発表)

  木村 勇気, 佐藤 岳志, 中村 智樹, 中村 教博, 野澤 純, 塚本 勝男, 山本 和生  日本惑星科学会秋期講演会予稿集  2014-  "O10  -03"  2014/09/10
• 観測ロケットS‐520‐28号機を用いた微小重力実験

  稲富裕光, 木村勇気, 塚本勝男, 竹内伸介, 石井信明  応用物理学会春季学術講演会講演予稿集(CD-ROM)  60th-  ROMBUNNO.29P-B6-2  2013/03/11  [Not refereed][Not invited]
  
• 観測ロケットS-520-28号機を用いた微小重力環境での鉄の均質核生成実験

  木村勇気, 田中今日子, 竹内伸介, 塚本勝男, 三浦均, 稲富裕光  結晶成長国内会議予稿集(CD-ROM)  43rd-  2013
• 観測ロケットS‐520‐28号機を用いた微小重力環境での鉄の均質核生成実験

  木村勇気, 田中今日子, 竹内伸介, 塚本勝男, 三浦均, 稲富裕光  結晶成長国内会議予稿集(CD-ROM)  43rd-  ROMBUNNO.08AC06  2013  [Not refereed][Not invited]
  
• NaClO₃溶液成長におけるアキラルな準安定相を介したキラル結晶形成過程

  新家寛正, 原田俊太, 宇治原徹, 三浦均, 木村勇気, 栗林貴弘, 上羽牧夫, 塚本勝男  結晶成長国内会議予稿集(CD-ROM)  43rd-  ROMBUNNO.08AC11  2013  [Not refereed][Not invited]
  
• 観測ロケット“S‐520‐28号機”を用いた微小重力実験から探る鉄微粒子の生成過程

  木村勇気, 田中今日子, 塚本勝男, 竹内伸介, 稲富裕光  日本惑星科学会秋季講演会予稿集  2013-  106  2013  [Not refereed][Not invited]
  
• 結晶成長過程の解明に向けた三次元干渉計の開発と応用

  村山健太, 塚本勝男, 木村勇気  結晶成長国内会議予稿集(CD-ROM)  43rd-  ROMBUNNO.06PB02  2013  [Not refereed][Not invited]
  
• NaClO₃溶液成長におけるアキラルな準安定相の溶解度測定

  新家寛正, 原田俊太, 宇治原徹, 三浦均, 木村勇気, 上羽牧夫, 塚本勝男  結晶成長国内会議予稿集(CD-ROM)  43rd-  ROMBUNNO.07PS29  2013  [Not refereed][Not invited]
  
• Acceleration and inhibition effects of phosphate on phase transformation of amorphous calcium carbonate into vaterite

  Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Katsuo Tsukamoto, Atsushi Yamazaki  AMERICAN MINERALOGIST  98-  (1)  262  -270  2013/01  [Not refereed][Not invited]
   

  Phase transformation of amorphous calcium carbonate (ACC) into vaterite and its subsequent stability was investigated at a constant pH (similar to 8.2), ionic strength, and temperature that simulated the biological environment. Solutions containing the same concentrations of CaCl2, Na2CO3, and tris(hydroxymethyl)aminomethane buffer and various concentrations of PO4 (0-62.5 mu M) were prepared, and precipitates in the solutions were sampled at a constant interval to observe the morphology and type of calcium carbonate polymorphs that appeared. The change in the Ca-ion concentration over time, which served as a guide for phase transformation of ACC into crystalline phases, was measured in relation to the PO4 concentration. The starting time of phase transformation was at the minimum point when the concentration was similar to 2-3 mu M. Vaterite spherulites consisting of needle-like crystals (0.5-2 mu m in length) formed only in this PO4 range and survived the experimental procedure (similar to 2.5 h). In contrast, the starting time of phase transformation increased exponentially with the PO4 concentration when it was higher than 5 mu M. The vaterite spherulites and calcite crystals co-precipitated, and both polymorphs grew over time. The PO4 was shown to be an accelerator for phase transformation from ACC into vaterite at low concentrations (Ca/PO4 molar ratio <3000) and an inhibitor for transformation at high concentrations. We investigated the kinetics of vaterite formation in the presence of PO4 and derived an advanced concept for cluster-based phase transformation. This investigation showed that the appearance and stability of calcium carbonate polymorphs is easily controlled by adjusting the PO4 concentration.
• Simultaneous Determination of Surface Free Energy and Sticking Probability of Nanoparticles Formed under Highly Supersaturated Environments and Importance of Microgravity Experiments

  KIMURA Yuki, NOZAWA Takaya, TANAKA Kyoko K, MIURA Hitoshi, MAKI Takao, TSUKAMOTO Katsuo, SAKON Itsuki, INATOMI Yuko  JASMA : Journal of the Japan Society of Microgravity Application  29-  (4)  184  -189  2012/10/31  [Not refereed][Not invited]
  
• O8-03 ダスト生成に重要な吸着係数と表面自由エネルギーの同時決定(口頭発表セッション8(室内実験II,惑星形成論I),口頭発表)

  木村 勇気, 田中 今日子, 三浦 均, 塚本 勝男, 稲富 裕光  日本惑星科学会秋期講演会予稿集  2012-  2012/10/24  [Not refereed][Not invited]
  
• THE MECHANISM OF SURFACE DIFFUSION OF H AND D ATOMS ON AMORPHOUS SOLID WATER: EXISTENCE OF VARIOUS POTENTIAL SITES

  Tetsuya Hama, Kazuaki Kuwahata, Naoki Watanabe, Akira Kouchi, Yuki Kimura, Takeshi Chigai, Valerio Pirronello  ASTROPHYSICAL JOURNAL  757-  (2)  185  -196  2012/10  [Not refereed][Not invited]
   

  To understand elementary processes leading to H-2 formation, and the hydrogenation and deuteration reactions of adsorbed species on dust grains in dense clouds, we experimentally investigated the diffusion of atomic hydrogen and deuterium on amorphous solidwater (ASW) at temperatures of 8-15 K. The present study extended our previous study for selective detections of H and D atoms, and of H-2 (J = 0 and 1) and D-2 (J = 0 and 1) molecules adsorbed on ASW using both photo-stimulated desorption and resonance-enhanced multiphoton ionization, to investigate potential sites on ASW for diffusion, recombination dynamics, and the diffusion mechanism of H and D atoms. Our results demonstrate that the ASW surface contains various potential sites that can be categorized into at least three groups: very shallow, middle-, and deep-potential sites, with diffusion activation energies of <= 18, 22 (23 meV for D atoms), and >= 30 meV, respectively. The present study pictured the outline of H-2 formation on cosmic ice dust at low temperatures: H atoms landing on the dust will diffuse rapidly at the abundant shallow and middle sites on ASW, and finally become trapped at deep sites. The H atoms that arrive next recombine with such trapped H atoms to yield H-2 molecules. The small isotopic difference between the diffusion of H and D atoms on ASW indicates that the diffusion mechanism can be explained by thermal hopping, at least at middle-potential sites.
• Direct Observation of the Homogeneous Nucleation of Manganese in the Vapor Phase and Determination of Surface Free Energy and Sticking Coefficient

  Y. Kimura, K. K. Tanaka, H. Miura, K. Tsukamoto  CRYSTAL GROWTH & DESIGN  12-  (6)  3278  -3284  2012/06  [Not refereed][Not invited]
   

  We examined the homogeneous condensation of thermally evaporated manganese vapor in an atmosphere of argon gas and determined the temperature and concentration during homogeneous nucleation in the vapor phase by using a Mach-Zehnder type interferometer. Condensation occurred at 660-785 K below the equilibrium temperature and the degree of supersaturation was as high as similar to 5 x 10(4). Using the condensation temperature and size of the condensed particles, which were measured by transmission electron microscopy, we determined the surface free energy and sticking coefficient of Mn at 1106 +/- 50 K to be 1.55 +/- 0.10 J/m(2) and 0.39(-0.20)(+0.39) respectively, by classical nucleation theory (CNT) and 1.57 +/- 0.35 J/m(2) and 0.42(-0.21)(+0.42), respectively, by a semiphenomenological theory (SP). The nucleation theories predict that the critical nucleus contains only three and six atoms for CNT and SP, respectively, which are fewer than the number of atoms in a unit cell of Mn. This suggests that the polymorphic form of manganese is decided during particle growth rather than during nucleation from the vapor phase.
• Cathodoluminescence microcharacterization of forsterite in the chondrule experimentally grown under super cooling

  A. Gucsik, K. Tsukamoto, H. Nishido, H. Miura, M. Kayama, K. Ninagawa, Y. Kimura  JOURNAL OF LUMINESCENCE  132-  (4)  1041  -1047  2012/04  [Not refereed][Not invited]
   

  Cathodoluminescence (CL) of laboratory forsterite chondrules has been characterized to clarify the formation process of chondrules and related mechanism of the crystal growth in a supercooled melt. Color CL image of the experimentally grown forsterite exhibits significant blue luminescence in the main branches of the interior structure of lab-chondrule, which reflects to the anisotropy of crystallization. A new CL band centered at 450-525 nm (2.76-2.36 eV) in blue to green region might be assigned to a microdefect-related center, which is a diagnostic peak for the forsterite that was formed due to the rapid growth as high as similar to 10 mm/s or higher from a supercooled melt. (C) 2011 Elsevier B.V. All rights reserved.
• S‐520観測ロケットを用いた宇宙ダストの核生成実験にむけて:WG初年度活動報告

  木村勇気, 稲富裕光, 三浦均, 田中今日子, 左近樹, 野沢貴也, 中村智樹, 塚本勝男  宇宙利用シンポジウム  28th-  23  -25  2012/03  [Not refereed][Not invited]
  
• Simultaneous Determination of Surface Free Energy and Sticking Probability of Nanoparticles Formed under Highly Supersaturated Environments and Importance of Microgravity Experiments

  木村勇気, 野沢貴也, 田中今日子, 三浦均, 真木孝雄, 塚本勝男, 左近樹, 稲富裕光  日本マイクログラビティ応用学会誌(Web)  29-  (4)  2012
• 炭酸水中におけるCa(OH)₂/CaCO₃のdissolution/precipitation反応の“その場”観察

  大島嘉文, 三浦均, 木村勇気, 佐藤久夫, 塚本勝男  結晶成長国内会議予稿集(CD-ROM)  42nd-  ROMBUNNO.09PD03  2012  [Not refereed][Not invited]
  
• 針状アラゴナイト結晶の成長メカニズム

  小隅誠司, 塚本勝男, 木村勇気, 三浦均  結晶成長国内会議予稿集(CD-ROM)  42nd-  ROMBUNNO.10PS22  2012  [Not refereed][Not invited]
  
• バテライト形成過程における結晶質の前駆体

  杉浦悠紀, 小沼一雄, 木村勇気, 門馬綱一, 塚本勝男, 山崎淳司  結晶成長国内会議予稿集(CD-ROM)  42nd-  ROMBUNNO.10AD09  2012  [Not refereed][Not invited]
  
• In-situ observation of cosmic dust formation toward micgrogravity experiment

  Yuki Kimura, Yuko Inatomi, Kyoko K. Tanaka, Takao Maki, Hitoshi Miura, Itsuki Sakon, Takaya Nozawa, Katsuo Tsukamoto  Journal of the Japanese Association for Crystal Growth  39-  68  -74  2012  [Not refereed][Not invited]
  
• Morphological evolution of precipitates during transformation of amorphous calcium phosphate into octacalcium phosphate in relation to role of intermediate phase

  Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto  JOURNAL OF CRYSTAL GROWTH  332-  (1)  58  -67  2011/10  [Not refereed][Not invited]
   

  Nucleation of amorphous calcium phosphate (ACP) and its phase transformation with a decrease in solution pH were investigated at a constant temperature of 32 degrees C. A solution containing a mixture of CaCl2 and KH2PO4 was prepared (initial pH=7.7), and a drop was sampled at a constant interval to observe the morphological evolution of the precipitates that formed in the solution. A gel-like solution structure formed immediately after mixing and contained a small amount of sea-urchin-like ACP spherulites (3-20 mu m in size). These spherulites consisted of 1.5-10-mu m-long flexible needles that formed simultaneously with numerous ACP spherical particles. They first transformed into beta-tri calcium phosphate-like material (called "pseudo beta-TCP") and then into single crystals of octacalcium phosphate (OCP) without dissolution. The flexible needles in the spherulites changed into blade springs, then into flexible plates, and finally into rigid plates during the transformation. The OCP structure appeared in the pseudo beta-TCP plates and gradually substituted for the beta-TCP structure over time. The macroscopic spherulite morphology of the initial ACP remained unchanged during the phase transformation, suggesting that OCP is a pseudomorph of ACP. This feature was observed only when the ACP spherulites formed in the initial solution. Fiber-like aggregates consisting of beta-TCP single crystals nucleated around the ACP spherical particles and grew over time. They survived until the final stage of the reaction, and OCP polycrystals formed in the mixture of beta-TCP and ACP spheres. The OCP polycrystals gradually substituted for the ACP spheres without phase transformation of beta-TCP into OCP. (C) 2011 Elsevier B.V. All rights reserved.
• 22aJB-1 In-situ observation of homogeneous nucleation in vapor phase using double wavelength interferometry

  Kimura Y, Tanaka K. K, Miura H, Inatomi Y, Tsukamoto K  Meeting abstracts of the Physical Society of Japan  66-  (2)  909  -909  2011/08/24  [Not refereed][Not invited]
  
• 光ピンセットを利用したコロイド結晶の核形成制御

  仙波稔己, 三浦均, 木村勇気, 塚本勝男  コロイドおよび界面化学討論会講演要旨集  63rd-  509  2011/08/22  [Not refereed][Not invited]
  
• CATHODOLUMINESCENCE PROPERTIES OF THE FORSTERITE FORMED UNDER SUPER COOLING: AN IMPLICATION FOR METEORITICS

  A. Gucsik, K. Tsukamoto, Y. Kimura, H. Miura, H. Nishido, M. Kayama, K. Ninagawa, Y. Endo  METEORITICS & PLANETARY SCIENCE  46-  A84  -A84  2011/07  [Not refereed][Not invited]
  
• 28aRA-12 Diffusion mechanism of hydrogen atoms adsorbed on water ice at low temperature

  Hama Tetsuya, Watanabe Naoki, Kouchi Akira, Kimura Yuki, Pirronello V.  Meeting abstracts of the Physical Society of Japan  66-  (1)  220  -220  2011/03/03
• 宇宙ダスト生成過程の解明に向けた気相からの均質核形成のその場観察実験

  木村勇気, 田中今日子, 三浦均, 塚本勝男, 稲富裕光  宇宙利用シンポジウム  27th-  47  -50  2011/03  [Not refereed][Not invited]
  
• Interferometric in-situ observation during nucleation and growth of WO3 nanocrystals in vapor phase

  Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto, Chaorong Li, Takao Maki  JOURNAL OF CRYSTAL GROWTH  316-  (1)  196  -200  2011/02  [Not refereed][Not invited]
   

  To investigate the homogeneous nucleation and growth process of nanoparticles in vapor phase, interferometric observation was attempted for the first time to the gas evaporation method, which has been a commonly accepted physical production method of nanoparticles. Tungsten oxide was evaporated by electrical heating of a tungsten wire in a mixture gas of Ar and O-2. WO3 nanoparticles were formed via homogeneous nucleation and growth during a gas cools following a thermal convection produced by the evaporation source. The degree of supersaturation for nucleation was extremely high, 6.6 x 10(6), which was determined from the interferogram. Surface free energy of WO3 at 1100 K was calculated based on the classical nucleation theory and was 1.38 x 10(3) erg cm(-2), which is within the reported values. A part of the difference between actual formation rate of produced nanoparticles, which were determined based on a transmission electron microscope, and calculated values based on the classical nucleation theory were well explained if we adopt the idea of coalescence growth. (C) 2011 Elsevier B.V. All rights reserved.
• Double wavelength interferometry for direct observation of homogeneous nucleation in vapor phase

  Yuki Kimura, Yuko Inatomi, Hitoshi Miura, Takao Maki, Katsuo Tsukamoto  ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES  67-  C117  -C117  2011
• アラゴナイト形成過程原子分解能その場観察

  荒木優希, 木村勇気, 塚本勝男, 高木良介, 宮下知幸, 大藪範昭, 小林圭, 山田啓文  結晶成長国内会議予稿集(CD-ROM)  41st-  ROMBUNNO.03AC08  2011  [Not refereed][Not invited]
  
• 隕石中のマグネタイトコロイド結晶

  野澤純, 塚本勝男, 木村勇気, 三浦均  結晶成長国内会議予稿集(CD-ROM)  41st-  ROMBUNNO.04AA04  2011  [Not refereed][Not invited]
  
• リン酸第8カルシウム(OCP)モルフォロジー形成時における中間相の役割

  杉浦悠紀, 小沼一雄, 木村勇気, 三浦均, 塚本勝男  結晶成長国内会議予稿集(CD-ROM)  41st-  ROMBUNNO.05AA01  2011  [Not refereed][Not invited]
  
• TEMを用いた液中“その場”観察:塩素酸ナトリウムの核生成

  木村勇気, 新家寛正, 三浦均, 塚本勝男  結晶成長国内会議予稿集(CD-ROM)  41st-  ROMBUNNO.03AC05  2011  [Not refereed][Not invited]
  
• 光ピンセットを利用した二次元コロイド結晶の核形成制御

  仙波稔己, 三浦均, 木村勇気, 石川正道, 塚本勝男  結晶成長国内会議予稿集(CD-ROM)  41st-  ROMBUNNO.03AC02  2011  [Not refereed][Not invited]
  
• 二酸化炭素固定化に向けた水酸化カルシウム結晶の面溶解・成長速度測定

  大島嘉文, 三浦均, 木村勇気, 佐藤久夫, 塚本勝男  結晶成長国内会議予稿集(CD-ROM)  41st-  ROMBUNNO.03AC06  2011  [Not refereed][Not invited]
  
• 金平糖の角(つの)の数

  塚本勝男, 三浦均, 木村勇気, 伊藤正憲, 佐藤久夫  結晶成長国内会議予稿集(CD-ROM)  41st-  ROMBUNNO.03AC10  2011  [Not refereed][Not invited]
  
• JEM内での溶液からの結晶成長“その場”観察用セル

  山崎智也, 三浦均, 木村勇気, 吉崎泉, 福山誠二郎, 真木孝雄, 塚本勝男  結晶成長国内会議予稿集(CD-ROM)  41st-  ROMBUNNO.03AC09  2011  [Not refereed][Not invited]
  
• Magnetite 3-D Colloidal Crystals Formed in the Early Solar System 4.6 Billion Years Ago

  J. Nozawa, K. Tsukamoto, W. J, P. Enckevort, T. Nakamura, Y. Kimura, H. Miura, H. Satoh, K. Nagashima, M. Konoto  Journal of the American Chemical Society  133-  8782  -8785  2011  [Not refereed][Not invited]
  
• Interferometric observation of temperature distributions in the smoke experiment

  Y. Kimura, K. Tsukamoto  J. Jpn. Soc. Microgravity Appl  2011  [Not refereed][Not invited]
  
• Calcite(100)面におけるOCPエピタキシャル成長

  杉浦悠紀, 木村勇気, 三浦均, 小沼一雄, 塚本勝男  無機リン化学討論会講演予稿集  20th-  94  -95  2010/10/07  [Not refereed][Not invited]
  
• ナノ粒子に現れる準安定相

  木村勇気, 塚本勝男  日本物理学会講演概要集  65-  (2)  330  2010/08/18  [Not refereed][Not invited]
  
• 24pWG-7 Metastable phase appearing in nanoparticles

  Kimura Yuki, Tsukamoto Katsuo  Meeting abstracts of the Physical Society of Japan  65-  (2)  330  -330  2010/08/18  [Not refereed][Not invited]
  
• 24pWG-7 Metastable phase appearing in nanoparticles(Symposium on nucleation of metastable crystal)

  Kimura Yuki, Tsukamoto Katsuo  Meeting abstracts of the Physical Society of Japan  65-  (2)  867  -867  2010/08/18  [Not refereed][Not invited]
  
• CONDENSATION TAKES PLACE IN FAR FROM EQUILIBRIUM CONDITION

  Y. Kimura, K. Tsukamoto, T. Maki  METEORITICS & PLANETARY SCIENCE  45-  A104  -A104  2010/07  [Not refereed][Not invited]
  
• DIRECT MEASUREMENTS OF HYDROGEN ATOM DIFFUSION AND THE SPIN TEMPERATURE OF NASCENT H-2 MOLECULE ON AMORPHOUS SOLID WATER

  Naoki Watanabe, Yuki Kimura, Akira Kouchi, Takeshi Chigai, Tetsuya Hama, Valerio Pirronello  ASTROPHYSICAL JOURNAL LETTERS  714-  (2)  L233  -L237  2010/05  [Not refereed][Not invited]
   

  Physicochemical processes (H-atom sticking, diffusion, recombination, and the nuclear spin temperature of nascent H-2 molecules) important in the formation of molecular hydrogen have been experimentally investigated on amorphous solid water (ASW). A new type of experiment is performed to shed light on a longstanding dispute. The diffusion rate of H atom is directly measured at 8 K and is found to consist of a fast and a slow component due to the presence of at least two types of potential sites with the energy depths of similar to 20 and >50 meV, respectively. The fast diffusion at the shallow sites enables efficient H-2 formation on interstellar ice dust even at 8 K, while H atoms trapped in the deeper sites hardly migrate. The spin temperature of nascent H-2 formed by recombination on ASW has been obtained for the first time and is higher than approximately 200 K. After formation, H-2 molecules are trapped and their spin temperature decreases due to the conversion of spin states on ASW.
• THE FORMATION OF GRAPHITE WHISKERS IN THE PRIMITIVE SOLAR NEBULA

  Joseph A. Nuth, Yuki Kimura, Christopher Lucas, Frank Ferguson, Natasha M. Johnson  ASTROPHYSICAL JOURNAL LETTERS  710-  (1)  L98  -L101  2010/02  [Not refereed][Not invited]
   

  It has been suggested that carbonaceous grains are efficiently destroyed in the interstellar medium and must either reform in situ at very low pressures and temperatures or in an alternative environment more conducive to grain growth. Graphite whiskers have been discovered associated with high-temperature phases in meteorites such as calcium aluminum inclusions and chondrules, and it has been suggested that the expulsion of such material from protostellar nebulae could significantly affect the optical properties of the average interstellar grain population. We have experimentally studied the potential for Fischer-Tropsch and Haber-Bosch type reactions to produce organic materials in protostellar systems from the abundant H(2), CO, and N(2) reacting on the surfaces of available silicate grains. When graphite grains are repeatedly exposed to H(2), CO, and N(2) at 875 K abundant graphite whiskers are observed to form on or from the surfaces of the graphite grains. In a dense, turbulent nebula, such extended whiskers are very likely to be broken off, and fragments could be ejected either in polar jets or by photon pressure after transport to the outer reaches of the nebula.
• Formation of polycyclic aromatic hydrocarbon grains using anthracene and their stability under UV irradiation

  Midori Saito, Itsuki Sakon, Chihiro Kaito, Yuki Kimura  EARTH PLANETS AND SPACE  62-  (1)  81  -90  2010  [Not refereed][Not invited]
   

  It has been known for sonic time that the properties of a material are changed in nanometer size. Since it is nontrivial that polycyclic aromatic hydrocarbon (PAH) grains at the nanometer scale show similar properties with that of macroscopic scale, PAH grains were synthesized by a gas evaporation method and were analyzed using a transmission electron microscope and their UV-Vis and mid-IR spectra were Measured. Results from these experiments showed that condensed anthracene grains from the gas phase had a planar form and showed similar infrared peaks compared to anthracene molecules, but With somewhat wider bands and different relative intensities. Sonic new features were also observed. The anthracene molecules formed photodimer ill their grain and showed different infrared features after UV irradiation. This Would be the first report concerning nanometer-sized PAH grains.
• Laboratory annealing experiments of refractory silicate grain analogs using differential scanning calorimetry

  Y. Kimura, J. A. Nuth III, C. Kaito  Meteoritics & Planetary Science  46-  92  -102  2010  [Not refereed][Not invited]
  
• Synthesis of stacked-cup carbon nanotubes in a metal free low temperature system

  Y. Kimura, J. A. Nuth III, N. M. Johnson, K. D. Farmer, K. P. Roberts, S. R. Hussaini  Nanoscience and Nanotechnology Letters  3-  1  -7  2010  [Not refereed][Not invited]
  
• AFM study on surface nanotopography of matrix olivines in Allende carbonaceous chondrite

  Jun Nozawa, Katsuo Tsukamoto, Hidekazu Kobatake, Junya Yamada, Hisao Satoh, Ken Nagashima, Hitoshi Miura, Yuki Kimura  ICARUS  204-  (2)  681  -686  2009/12  [Not refereed][Not invited]
   

  By means of nanoscale surface observation, we have proposed a new approach for investigating fine crystals of cosmic materials to reveal their origin and growth conditions. Several different morphologies of polyhedral fine olivines with faceted faces have been found in Allende carbonaceous chondrite (4.5 byr in geochronological age). In the present work, molecular level topography of the faceted matrix olivine by Atomic Force Microscopy (AFM) has Successfully been performed, The matrix olivine found to have preserved growth step pattern on its surface even though quite long time has passed since they formed in the early Solar System. The Surface pattern Suggests that the faceted matrix olivine could have been condensed from the gas phase, and possibly that these olivine crystals had continued to grow under a rapid cooling condition (0.1-1 K s(-1)). The estimated cooling rate agrees well with predictions based on hypothetical rapid heating and cooling events such as shock wave heating. (C) 2009 Elsevier Inc. All rights reserved.
• ORIGIN OF ORGANIC GLOBULES IN METEORITES: LABORATORY SIMULATION USING AROMATIC HYDROCARBONS

  Midori Saito, Yuki Kimura  ASTROPHYSICAL JOURNAL LETTERS  703-  (2)  L147  -L151  2009/10  [Not refereed][Not invited]
   

  Analogs of organic hollow globules, which have been found in carbonaceous chondrite meteorites and interplanetary dust particles, were synthesized in our laboratory from benzene and anthracene using plasma. Our results suggest that organic globules could be made from aromatic rings in circumstellar envelopes around evolved stars. The hollow interior could be formed by coagulation of vacancies, formed by electronic excitation and/or knock-out of carbon atoms following irradiation by plasma particles such as protons and He(+) ions. This experimental result suggests that organic globules are possibly the final products in the evolution of carbonaceous matter from acetylene and benzene to polycyclic aromatic hydrocarbons in ejecta gas from evolved stars.
• 27pZB-7 Diffusion and desorption of hydrogen atoms on amorphous solid water at very low temperatures

  Watanabe Naoki, Kouchi Akira, Kimura Yuki  Meeting abstracts of the Physical Society of Japan  64-  (2)  96  -96  2009/08/18
• 隕石中のマグネタイトのコロイド結晶

  野澤純, 塚本勝男, 木村勇気, 甲野藤真  日本物理学会講演概要集  64-  (2)  297  -297  2009/08/18  [Not refereed][Not invited]
  
• 28aYH-5 Magnetite colloidal crystals in the meteorite

  野澤 純, 塚本 勝男, 木村 勇気, 甲野藤 真  Meeting abstracts of the Physical Society of Japan  64-  (2)  297  -297  2009/08/18  [Not refereed][Not invited]
  
• Colloidal crystallization of magnetite particles in the meteorite

  NOZAWA JUN, TSUKAMOTO KATSUO, KONOTO MAKOTO, KIMURA YUKI  結晶成長国内会議予稿集  39th-  186  2009  [Not refereed][Not invited]
  
• 46億年昔の宇宙空間での結晶化

  木村勇気, 三浦均, 塚本勝男  日本マイクログラビティ応用学会誌  2009  [Not refereed][Not invited]
  
• Laboratory Simulation using Aromatic Hydrocarbons

  M. Saito, Y. Kimura  The Astrophysical Journal Letters  703-  L147-L151  2009  [Not refereed][Not invited]
  
• Experimental demonstration of condensation of Mg-bearing silicate grains around evolved stars

  Y. Kimura, S. Sasaki, H. Suzuki, A. Kumamoto, M. Saito, C. Kaito  ASTROPHYSICAL JOURNAL  684-  (2)  1496  -1501  2008/09  [Not refereed][Not invited]
   

  Mg-bearing silicate grains were produced directly from the vapor phase from magnesium and silicon oxide in a mixed atmosphere of Ar and O-2 in the laboratory. It was found that the crystallinity, which was deduced from the shape of the 10 mu m feature, of the grains depends on the ratio of magnesium to silicon oxide in the vapor phase. When the Mg/SiOx ratio was high, crystalline forsterite grains were produced owing to annealing of the silicate accompanied by large exothermic energy due to the oxidation of magnesium. The experimental result suggests that the crystallinity of circumstellar silicates could be determined by the balance between heat generation by magnesium oxidation and heat dissipation due to radiation. In this situation, later annealing of the silicate fraction or the use of a warm substrate for condensation of crystalline silicate is unnecessary. Crystalline silicates found in young stars are also able to be produced following our hypothesis after simultaneous evaporation of silicates and ices during energetic shocks in protostellar nebulae.
• Morphological alteration and structure of ZnO particles produced in electric field

  Chihiro Kaito, Yasuhiko Kinuta, Hitoshi Suzuki, Syunsuke Adachi, Akihito Kumamoto, Yoshio Saito, Yuki Kimura  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN  77-  (9)  094708-1-094708-4  2008/09  [Not refereed][Not invited]
   

  The apparent morphological difference between ZnO particles with and without an electric field applied during the growth process was elucidated by high-resolution transmission electron microscopy. The ZnO smoke produced immediately below the electric field by burning zinc in a gas mixture of O-2, and Ar, curved towards a negative plate. The typical tetrapod- or needle-shaped ZnO particles were seldom observed in the electric field; spherical particles were predominantly produced. Some of these spherical particles were composed of multiply twinned particles with an antiphase boundary. The growth of these multiply twinned particles was due to an increment in the ionicity in the crystallographic polar direction of ZnO bonding induced by the applied electric field.
• Direct observation of MoO(2) crystal growth from amorphous MoO(3) film

  Kenji Nina, Yuki Kimura, Kaorl Yokoyama, Osamu Kido, Gong Binyo, Chihiro Kaito  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES  40-  (9)  2995  -2998  2008/08  [Not refereed][Not invited]
   

  The formation process of MoO(2) crystal from amorphous MoO(3) film has been imaged by in situ observation with a transmission electron microscope. Selective growth of flower-shaped MoO(2) crystals by heating above 673 K in vacuum was directly observed. Since the MoO(2) crystal has metallic conductivity of the order of indium oxide film containing tin (ITO film), the thin film growth of the MoO(2) phase has been discussed on the basis of a new substitute for ITO film. (C) 2008 Elsevier B.V. All rights reserved.
• Structural Alterations of Carbon Particles in Saturated Water Vapor

  Chihiro Kaito, Masayuki Shintaku, Ryuta Sakao, Akihito Kumamoto, Midori Saito, Yuki Kimura, Shinsuke Ohyagi, Shigeru Morikawa, Hiroshi Suzuki  JAPANESE JOURNAL OF APPLIED PHYSICS  47-  (8)  6588  -6591  2008/08  [Not refereed][Not invited]
   

  High-resolution transmission electron microscopy (HRTEM) of carbon particles has been carried out at 80 degrees C in saturated water vapor, to evaluate any structural alterations. Amorphous particles or microcrystallites of carbon based on the graphitic structure were altered to more stable graphitic structures such as ribbons or onion-like structures. The stable graphitic structure was altered again to the amorphous structure. Results are interpreted in terms of the oxidation of carbon particles in air. The differences in alterations among carbon particles, Pt clusters on carbon particles, and Pt clusters in carbon particles are presented on the basis of HRTEM images.
• Characteristic low-temperature crystallization of amorphous Mg-bearing silicate grains under electron irradiation

  Yuki Kimura, Yu Miyazaki, Akihito Kumamoto, Midori Saito, Chihiro Kaito  ASTROPHYSICAL JOURNAL LETTERS  680-  (1)  L89  -L92  2008/06  [Not refereed][Not invited]
   

  Amorphous Mg-bearing silicate grains, which were produced by the coalescence between MgO and SiOx smoke particles, were crystallized to forsterite (Mg2SiO4) by electron-beam irradiation in a transmission electron microscope at room temperature. The crystallization induced by electron beams was accelerated by the presence of CH4 adsorbed on the surface and incorporated interior of the grains. This experimental result implies the possibility of low-temperature crystallization in a silicate carbon star. In the case of binary stars, since the materials that flow from the stars stationarily exist around the star, the formed amorphous silicate grains will be irradiated by electrons from the star for a long duration. As a result, a significant amount of crystalline silicates can be produced.
• A refractory Ca-SiO-H(2)-O(2) vapor condensation experiment with implications for calciosilica dust transforming to silicate and carbonate minerals

  Frans J. M. Rietmeijer, Aurora Pun, Yuki Kimura, Joseph A. Nuth  ICARUS  195-  (1)  493  -503  2008/05  [Not refereed][Not invited]
   

  Condensates produced in a laboratory condensation experiment of a refractory Ca-SiO-H(2)-O(2) vapor define four specific and predictable deep metastable eutectic calciosilica compositions. The condensed nanograins are amorphous solids, including those with the stoichiometric CaSiO(3) pyroxene composition. In evolving dust-condensing astronomical environments they will be highly suitable precursors for thermally supported, dust-aging reactions whereby the condensates form more complex refractory silicates, e.g., diopside and wollastonite, and calcite and dolomite carbonates. This kinetically controlled condensation experiment shows how the aging of amorphous refractory. condensates could produce the same minerals that are thought to require high-temperature equilibrium condensation. We submit that evidence for this thermal annealing of dust will be the astronomical detection of silica (amorphous or crystalline) that is the common, predicted, by-product of most of these reactions. (C) 2007 Elsevier Inc. All rights reserved.
• Behavior of cosmic dust with the material evolution in the early solar nebula

  Yuki Kimura  The Japanese Society for Planetary Sciences  17-  62  -68  2008  [Not refereed][Not invited]
  
• Production of refractory-metal ultrafine particles by gas evaporation method and their surface oxide layer

  Y. Kimura, C. Kaito  Surface and Coatings Technology  202-  4159  -4162  2008  [Not refereed][Not invited]
  
• Possible Driving Force behind Formation of Cosmic Carbyne Crystals

  Y. Kimura, C. Kaito  The Astrophysical Journal Letters  685-  83  -86  2008  [Not refereed][Not invited]
  
• Structural alteration of nanostructure carbon particles carrying Pt clusters in H-2 and O-2 gases

  Chihiro Kaito, Ryoichi Ono, Ryuta Sakao, Akihito Kuniamoto, Midori Saito, Yuki Kimura, Shinsuke Ohyagi  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS  46-  (45-49)  L1141  -L1142  2007/12  [Not refereed][Not invited]
   

  The effects of H-2 and O-2 gases on the typical fuel cell catalyst of Pt clusters on carbon particles (Pt on Q were examined using a special side-entry sample holder for high-resolution transmission electron microscopy, The holder can be used to transfer the specimen without exposure to air. The effects of H-2 and O-2 were detected after the specimen was exposed to the gases at 60 degrees C for 15 h. The predominant effect of H-2 was the coagulation of the Pt clusters. The effect of O-2 was to alter the structure of the carbon particles by oxidation.
• What is the driving force to form refractory oxide grains? Silicate spectra depend on their formation environment

  Yuki Kimura, Joseph A. Nuth  ASTROPHYSICAL JOURNAL  664-  (2)  1253  -1263  2007/08  [Not refereed][Not invited]
   

  We discuss room-temperature condensation experiments using either an electrical discharge or ultraviolet radiation to initiate gas-phase reactions resulting in silicate smokes. This formation process could represent processes occurring in low-density environments, because it is possible that the gases, which can condense at higher temperatures, remain after it cools, e. g., following a shock. In these environments, many condensates could be formed simultaneously. However, in the case of our iron silicate experiments, many of the smoke particles are iron silicate with a uniform composition that reflects the composition of the ambient gas atmosphere where they were produced. In these experiments, smoke particles of other materials such as iron oxide and silica were not formed. In the case of our Si-O experiments, hydro-silicate smoke particles are produced together with anhydrous silicate particles directly from the gas phase without later hydro alteration. The infrared spectra of these silicate particles show a very strong 11.36 mu m feature attributed to H2Si2O4 and possibly to Si2O3 compared with a simultaneously observed 9.2 mu m feature due to the Si-O vibration. We believe that finding the driving force for grain growth under a wide range of environmental conditions is important if we are to understand grain formation, because silicate grains, which formed in a plasma field or under UV irradiation, show different compositions, structures, shapes, and spectra from thermally condensed grains.
• Non-mass-dependent oxygen isotopic fractionation in smokes produced in an electrical discharge

  Yuki Kimura, Joseph A. Nuth, Subrata Chakpaborty, Mark H. Thiemens  METEORITICS & PLANETARY SCIENCE  42-  (7-8)  1429  -1439  2007/07  [Not refereed][Not invited]
   

  We report the first production of non-mass-dependently fractionated silicate smokes from the gas phase at room temperature from a stream of silane and/or pentacarbonyl iron in a molecular hydrogen (or helium) flow mixed with molecular oxygen (or nitrous oxide). The smokes were formed at the Goddard Space Flight Center (GSFC) at total pressures of just under 100 Torr in an electrical discharge powered by a Tesla coil, were collected from the surfaces of the copper electrodes after each experiment and sent to the University of California at San Diego (UCSD) for oxygen isotopic analysis. Transmission electron microscopy studies of the smokes show that they grew in the gas phase rather than on the surfaces of the electrodes. We hypothesize at least two types of fractionation processes occurred during formation of the solids: a mass-dependent process that made isotopically lighter oxides compared to our initial oxygen gas composition followed by a mass-independent process that produced oxides enriched in (17)O and (18)O. The nnaximum Delta(17)O observed is +4.7 parts per thousand for an iron oxide produced in flowing hydrogen, using O(2) as the oxidant. More typical displacements are 1-2 parts per thousand above the equilibrium fractionation line. The chemical reaction mechanisms that yield these smokes are still under investigation.
• 19pTG-3 Crystallization of carbonaceous materials in an amornhous carbon film including a metal in various gas environments

  Kimura Yuki, Kaito Chihiro  Meeting abstracts of the Physical Society of Japan  62-  (1)  889  -889  2007/02/28
• 19pTG-2 Growth of NiO and stabilized ZrO_2 nanoparticles

  Iyanaga Hideomi, Kumamoto Akihito, Shintaku Masayuki, Kimura Yuki, Kaito Chihiro  Meeting abstracts of the Physical Society of Japan  62-  (1)  889  -889  2007/02/28
• 原始太陽系における物質進化に関わる結晶成長

  木村勇気, 墻内千尋  2007  [Not refereed][Not invited]
  
• Exothermic chemical reactions can drive nonthermal crystallization of amorphous silicate grains

  Chihiro Kaito, Yu Miyazaki, Akihito Kumamoto, Yuki Kimura  Astrophysical Journal  666-  (1)  L57  -L60  2007  [Not refereed][Not invited]
   

  To explain how cometary silicates crystallize yet still preserve volatile interstellar ices in their parent comets, we experimentally demonstrate the possibility of chemical-reaction-driven crystallization, which is called non-thermal crystallization, using laboratory-synthesized amorphous Mg-bearing silicate grains. Analog silicate grains ∼50-100 nm in diameter covered with a carbonaceous layer consisting of amorphous carbon, CH 4, and other organics to a thickness of ∼10-30 nm were used as models. The analog silicate grains crystallized via the direct flow of surface reaction energy, which is produced by the graphitization of the carbonaceous layer due to oxidation at room temperature in air, into the silicates. The experimental results imply that amorphous silicates are transformed into crystalline silicates as the grains leave the comet's surface, rather than as the comet was accreted 4.5 billion years ago. Thus, primordial ices and amorphous silicate grains are predicted to reside in most comets until they approach the Sun.
• Growth of TiO and TiO_2 Smoke Particles from TiC Smoke

  KUMAMOTO Akihito, SHINTAKU Masayuki, KURUMADA Mami, KIMURA Yuki, KAITO Chihiro  Journal of the Japanese Association of Crystal Growth  33-  (4)  312  -312  2006/11/30  

  TiO and TiO_2 particles were produced from TiC smoke in a gas mixture by the alteration of the partial pressure of O_2. In the case of the partial of 0.075 Torr of oxygen in Argon pressure at 75 Torr, successive growth of TiO_2, TiO and mixture of TiC and TiO have been formed.
• Silicate Grain Formation with Non-Mass Dependent Oxygen Isotopic Fractionation

  KIMURA Yuki, NUTH Joseph A. III, CHAKRABORTY Subrata, THIEMENS Mark H.  Journal of the Japanese Association of Crystal Growth  33-  (4)  315  -315  2006/11/30  

  We found that electrical discharge can produce non-mass dependent oxygen isotopic fractionation in refractory oxide grains. So far, only photodissociation has been known to produce non-mass dependent oxygen isotopic fractionation. Our results may provide another possible path, caused by the processing of presolar silicate materials and leading to the non-mass dependent oxygen isotopic fractionation of CAIs and chondrules.
• Electric field effect on the growth of metallic and polar crystal particles

  ADACHI S., KUMAMOTO A., SHINTAKU M., KIMURA Y., KINUTA Y., KAITO C.  Journal of the Japanese Association of Crystal Growth  33-  (4)  311  -311  2006/11/30  

  Successive to the oxide particle formation in electric field, electric field effects have been elucidated for the metallic and polar particles. Metallic and ZnO particles were curved to the minus plate. The multiple twined particles were observed in ZnO. The emergency of multiple twined particles in Ag also becomes prominent.
• 24pYH-3 Structural alteration of carbon nanoparticle by heating at 80℃ II

  Shintaku M., Suzuki H., Kimura Y., Kido O., Kurumada M., Saito Y., Kaito C.  Meeting abstracts of the Physical Society of Japan  61-  (2)  738  -738  2006/08/18
• 24pYH-6 Growth of silicate grains depends on the formation environments and their infrared spectra

  Kimura Yuki, Nuth III Joseph A.  Meeting abstracts of the Physical Society of Japan  61-  (2)  739  -739  2006/08/18
• 24pYH-12 Lowering of theta-alpha transition temperature by size decreasing of alumina nanoparticles

  Kurumada Mami, Saito Midori, Kimura Yuki, Kaito Chihiro  Meeting abstracts of the Physical Society of Japan  61-  (2)  740  -740  2006/08/18
• 24pYH-2 Effect of Electric Field for Growth of Metal and Semimetal Nano-particles

  Adachi S., Kimura Y., Kinuta Y., Kaito C.  Meeting abstracts of the Physical Society of Japan  61-  (2)  738  -738  2006/08/18
• Influence of plasma on formation of crystalline Fe2SiO4 grains

  T Sato, M Kurumada, K Kamitsuji, O Kido, H Suzuki, M Shintaku, Y Kimura, Y Saito, C Kaito  PLANETARY AND SPACE SCIENCE  54-  (6)  612  -616  2006/05  [Not refereed][Not invited]
   

  The production of Fe2SiO4 (fayalite) crystalline grains was performed by two processes, namely, grain formation in a plasma field by evaporating a mixture powder of Fe and SiO and heat treatment of the product collected on the radio-frequency (RF) electrode side. Fe grains < 20 nm in size covered with an amorphous SiO layer selectively formed Fe2SiO4 grains by heating at 800 degrees C. By heating at 600 degrees C, in addition to the formation of Fe2SiO4 crystal grains, the FeO phase appeared. The doping effect of excited oxygen in a plasma field into the Fe small grains may be the trigger on the formation of fayalite through the FeO phase formation. The present experimental result suggests that the probability Of Fe2SiO4 grain formation in space is low. (c) 2006 Published by Elsevier Ltd.
• Laboratory analogy of crystalline enstatite grain formation in plasma field

  T Sato, K Kamitsuji, M Shintaku, Y Kimura, M Kurumada, O Kido, H Suzuki, Y Saito, C Kaito  PLANETARY AND SPACE SCIENCE  54-  (6)  617  -620  2006/05  [Not refereed][Not invited]
   

  Crystalline enstatite (MgSiO3) grains were produced by the simultaneous evaporation of SiO grains and Mg vapor in a plasma field. The MgSiO3 grains were spherical or needlelike. The necessity of a plasma field in astromineralogy is suggested in the present study. (c) 2006 Published by Elsevier Ltd.
• Formation of TiC core-graphitic mantle grains from CO gas

  Yuki Kimura, Joseph A. Nuth, Frank T. Ferguson  METEORITICS & PLANETARY SCIENCE  41-  (5)  673  -680  2006/05  [Not refereed][Not invited]
   

  We demonstrate a new formation route for TiC core-graphitic mantle spherules that does not require carbon-atom addition and the very long time scales associated with such growth (Bernatowicz et al. 1996). Carbonaceous materials can be formed from C2H2 and its derivatives, as well as from CO gas. In this paper, we will demonstrate that large-cage-structure carbon particles can be produced from CO gas by the Boudouard reaction. Since the sublimation temperature for such fullerenes is low, the large cages can be deposited onto previously nucleated TiC and produce TiC core-graphitic mantle spherules. New constraints for the formation conditions and the time scale for the formation of TiC core-graphitic mantle spherules are suggested by the results of this study. In particular, TiC core-graphitic mantle grains that are found in primitive meteorites that have never experienced hydration Could be mantled by fullerenes or carbon nanotubes rather than by graphite. In situ observations of these grains in primitive anhydrous meteoritic matrix could confirm or refute this prediction and would demonstrate that the graphitic mantle on such grains is a metamorphic feature due to interaction of the presolar fullerenes with water within the meteorite matrix.
• Synthesis of Al-Cr decagonal quasicrystal nanoparticles and their temperature of phase transformation to stable crystal phase

  O Kido, M Kurumada, K Kamltsuji, T Tanigaki, T Sato, Y Kimura, H Suzuki, Y Saito, C Kaito  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES  31-  (2)  169  -173  2006/03  [Not refereed][Not invited]
   

  The synthesis of Al-Cr single quasicrystal (QC) nanoparticles of the decagonal phase was achieved by introducing an advanced gas flow evaporation method. By obtaining Successive electron diffraction patterns for single-QC nanoparticles, the phase transformation temperature of a single-QC nanoparticle was determined to be 700 degrees C. It was also determined that part of the QC nanoparticle decomposed into hex-AI(8)Cr(5) and Al during the phase transformation. Since the grain growth did not occur during the phase transformation in the present experiment, the inherent phase transformation temperature could be measured. (c) 2006 Elsevier B.V. All rights reserved.
• Direct observation of the crystallization of carbon-coated amorphous Mg-bearing silicate grains

  C. Kaito, S. Sasaki, Y. Miyazaki, A. Kumamoto, M. Kurumada, K. Yokoyama, M. Saito, Y. Kimura, H. Suzuki  Advances in Geosciences  7-  125  -131  2006  [Not refereed][Not invited]
  
• Formation of CaTiO3 crystalline dust in laboratory

  K. Yokoyama, Y. Kimura, O. Kido, M. Kurumada, A. Kumamoto, C. Kaito  Advances in Geosciences  7-  115  -123  2006  [Not refereed][Not invited]
  
• A New method of producing titanium carbide, monoxide, and dioxide grains in laboratory

  A. Kumamoto, M. Kurumada, Y. Kimura, C. Kaito  Advances in Geosciences  7-  93  -99  2006  [Not refereed][Not invited]
  
• Laboratory production of magnesium sulfide grains and their characteristic infrared spectra due to shape

  Y Kimura, M Kurumada, K Tamura, C Koike, H Chihara, C Kaito  ASTRONOMY & ASTROPHYSICS  442-  (2)  507  -512  2005/11  [Not refereed][Not invited]
   

  Nanosized MgS grains, which have been considered the origin of the 30 mu m emission feature of carbon-rich evolved objects, were produced from the gas phase using an advanced gas evaporation method. The far-infrared spectrum of cubic MgS grains showed a characteristic absorption peak at 311 cm(-1) (32.1 mu m) with three shoulders at 460, 400 and 262 cm(-1) (21.7, 25.0 and 38.2 mu m). On the other hand, when the grains were roundish or network-like, the absorption peak at 250 cm(-1) became predominant. The cubic MgS grains were produced by direct nucleation from the gas phase. In the case of production via a gas-solid reaction, the MgS grains were network-like. Therefore, the formation environments of MgS grains around carbon-rich evolved objects may be predicted from the intensity of 310 and 250 cm(-1) bands. We suggest that the origins of the absorption band at 310 and 250 cm(-1) are (100), (110) and/or (111) surfaces of MgS grains, respectively.
• Is the 21 micron feature observed in some post-AGB stars caused by the interaction between Ti atoms and fullerenes?

  Y Kimura, JA Nuth, FT Ferguson  ASTROPHYSICAL JOURNAL  632-  (2)  L159  -L162  2005/10  [Not refereed][Not invited]
   

  Recent measurements of fullerenes and Ti atoms recorded in our laboratory have demonstrated the presence of an infrared feature near 21 mu m. The feature observed has nearly the same shape and position as is observed for one of the most enigmatic features in post-asymptotic giant branch (AGB) stars. In our experimental system, large-cage carbon particles, such as large fullerenes, were produced from CO gas by the Boudouard reaction. Large-cage carbon particles intermixed with Ti atoms were produced by the evaporation of a Ti-metal-wrapped carbon electrode in CO gas. The infrared spectra of large fullerenes interacting with Ti atoms show a characteristic feature at 20.3 mu m that closely corresponds to the 20.1 mu m feature observed in post-AGB stars. Both the laboratory and stellar spectra also show a small but significant peak at 19.0 mu m, which is attributed to fullerenes. Here we propose that the interaction between fullerenes and Ti atoms may be a plausible explanation for the 21 mu m feature seen in some post-AGB stars.
• Laboratory production of monophase pyrrhotite grains using solid-solid reaction and their characteristic infrared spectra

  Y Kimura, K Tamura, C Koike, H Chihara, C Kaito  ICARUS  177-  (1)  280  -285  2005/09  [Not refereed][Not invited]
   

  A new method of producing pyrrhotite grains, which are most commonly found in cometary material and interplanetary dust particles, was developed. Pyrrhotite grains in the monophase having a 7C structure were predominately produced using a solid-solid reaction between iron and sulfur grains at room temperature. The characteristic infrared peaks were observed at 602, 563, and 397 cm(-1) (16.6, 17.8, and 25.2 mu m). (c) 2005 Elsevier Inc. All rights reserved.
• Laboratory synthesized calcium oxide and calcium hydroxide grains: A candidate to explain the 6.8 mu m band

  Y Kimura, JA Nuth  ASTROPHYSICAL JOURNAL  630-  (1)  637  -641  2005/09  [Not refereed][Not invited]
   

  We demonstrate that CaO and Ca(OH)(2) are excellent candidates to explain the 6.8 mu m feature, which is one of the most obscure features in young stellar objects. We discuss the condensation of CaO grains and the potential formation of a Ca(OH)(2) surface layer. The infrared spectra of these grains are compared with the spectra of 15 young stellar objects. We note that CaO-rich grains are seen in all meteoritic CAIs (calcium-aluminum-rich inclusions) and that the 6.8 mu m feature has only been observed in young stellar objects. Therefore, we consider CaO grains to be a plausible candidate to explain the 6.8 mu m feature and hypothesize that they are produced in the hot interiors of young stellar environments.
• Formation of carbon nanotubes from mixture film of carbon and titanium

  Y Kimura, C Kaito  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES  28-  (3)  281  -285  2005/08  [Not refereed][Not invited]
   

  It was shown that a carbon nanotube was selectively formed from carbon film containing Ti, supported by a standard Mo transmission electron microscopic grid, by heating at 800 degrees C in vacuum. With heating above 950 degrees C, graphite and rutile crystals of TiO2 predominately appeared. The formation of oxide is due to the supply of oxygen from the Mo grid. The formation mechanism of the carbon nanotubes was discussed on the basis of the heat of combustion due to the oxidation of titanium. The present result will lead to the development of an efficient method of production of carbon nanotubes. (c) 2005 Elsevier B.V. All rights reserved.
• Direct observation of thermal alteration of mixed film of Ge and SiO

  C Kaito, K Kamitsuji, S Tanaka, O Kido, M Kurumada, T Sato, Y Kimura, H Suzuki, Y Saito  THIN SOLID FILMS  483-  (1-2)  396  -399  2005/07  [Not refereed][Not invited]
   

  The dynamic behavior of a film produced by coevaporation of Ge-SiO was observed in situ using a transmission electron microscope. The film produced had an amorphous structure containing Si, Ge and SiO2. A characteristic change of the film was observed above 500 degrees C. Upon heating at 750 degrees C, in addition to the growth of the SiGe mixed crystal with the diamond structure, the liquidlike mixed phase of SiGe-SiO2 was also produced. The growth process of the liquidlike phase was directly observed in situ. The growth process of Ge and GeSi nanocrystallites has been elucidated by cooling the mixed film to room temperature. (c) 2004 Elsevier B.V All rights reserved.
• Production of diamond and solid-solution nanoparticles in the carbon-silicon system using radio-frequency plasma

  Y Kimura, T Sato, C Kaito  CARBON  43-  (7)  1570  -1574  2005/06  [Not refereed][Not invited]
  
• Novel routes for diamond formation in interstellar ices and meteoritic parent bodies

  A Kouchi, H Nakano, Y Kimura, C Kaito  ASTROPHYSICAL JOURNAL  626-  (2)  L129  -L132  2005/06  [Not refereed][Not invited]
   

  We have identified new formation routes of diamond in interstellar clouds and parent bodies of carbonaceous chondrites in laboratory experiments. The diamond precursor nucleated under UV photolysis of interstellar ice mixtures in molecular clouds and grew with further UV irradiation in diffuse clouds. The present study supports the occurrence of diamonds in interstellar clouds and suggests that diamond is ubiquitous in space. We also performed experiments on the processes of aqueous alteration and subsequent thermal metamorphism of organic materials formed in molecular clouds, and the results were consistent with the formation of diamonds by this process in the parent bodies of carbonaceous chondrites. The various characteristics of nanodiamonds in chondrites and interplanetary dust are well explained by these new formation routes.
• Formation of new carbides with diamond structure from carbon film containing transition metal.

  Y Kimura, C Kaito  THIN SOLID FILMS  476-  (1)  65  -67  2005/04  [Not refereed][Not invited]
   

  New carbide crystallites, which have a solid-solution phase with diamond structure, were formed from amorphous carbon film containing a transition metal such as Fe, Co, Mo or Ti by vacuum heating at 500-800 degrees C. The lattice constants for each solid-solution phase have been determined from electron diffraction patterns and high-resolution transmission electron microscope images. The formation of carbon polymorphs has been summarized as being dependent on the heat treatment temperature. (c) 2004 Elsevier B.V. All rights reserved.
• Crystal structure and growth of carbon-silicon mixture film prepared by ion sputtering

  Y. Kimura, M. Ishikawa, M. Kurumada, T. Tanigaki, H. Suzuki, C. Kaito  JOURNAL OF CRYSTAL GROWTH  275-  (1-2)  E977  -E981  2005/02  [Not refereed][Not invited]
   

  Si (10-50%)-containing carbon (C-Si) films were prepared by ion sputtering of carbon and silicon carbide mixture pellets. The C-Si film was composed of a solid-solution phase of carbon and silicon with a diamond structure. The film showed a higher transparency than a simultaneously evaporated C-Si mixture film. Diamond crystals 100 nm in diameter were also produced by vacuum heating of C-Si film at 800 degrees C: The infrared spectrum showed significant absorption features at 9.5 and 21 mu m; in contrast to the 11 and 12 mm of SiC. The 21 mu m feature is one of the candidate unidentified infrared bands on the spectra of carbon-rich post-asymptotic giant branch stars. (C) 2004 Elsevier B.V. All rights reserved.
• Structure of WO3 ultrafine particles and their characteristic solid states

  Mami Kurumada, Osamu Kido, Takeshi Sato, Hitoshi Suzuki, Yuki Kimura, Katsuya Kamitsuji, Yoshio Saito, Chihiro Kaito  JOURNAL OF CRYSTAL GROWTH  275-  (1-2)  E1673  -E1678  2005/02  [Not refereed][Not invited]
   

  WO3 nanoparticles from 10 to 250nm in diameter were formed by burning tungsten wire in low-oxygen-partial-pressure atmosphere in Ar gas. The structure of the 10-nm-order particle was cubic WO3, and for the particle larger than 50 nm, the structure was triclinic WO3. The color of the produced samples changed from blue to yellowish green and yellow depending on the particle size. It was also shown that the present particle is a good transmittance material for mid-IR light with wavelength between 5 and 20 mu m. The growth of huge particles by coalescence growth in smoke has been discussed. (C) 2004 Elsevier B.V. All rights reserved.
• Production of transition metal-doped ZnO nanoparticles by using RF plasma field

  Takeshi Sato, Hitoshi Suzuki, Osamu Kido, Mami Kurumada, Katsuya Kamitsuji, Yuki Kimura, Hiromichi Kawasaki, Satoo Kaneko, Yoshio Saito, Chihiro Kaito  JOURNAL OF CRYSTAL GROWTH  275-  (1-2)  E983  -E987  2005/02  [Not refereed][Not invited]
   

  Transition metals, such as tungsten (W), molybdenum (Mo) and chromium (Cr), were doped into ZnO nanoparticles using an RF plasma system. The resulting ZnO nanoparticles with the size of 30-50 nm changed from white to yellowish or to orange depending on the doped transition metals. The doping position of these transition metals in the ZnO crystal was the same as that determined in a previous paper (J. Crystal Growth 265 (2004) 149). It was found that light with wavelength shorter than 385 nm can be removed by doping. The morphological change due to doping of elements was discussed in terms of the difference of ionicity. (C) 2004 Elsevier B. V. All rights reserved.
• Morphological alteration upon phase transition and effects of oxygen impurities of chromium nanoparticles

  Osamu Kido, Katsuya Kamitsuji, Mami Kurumada, Takeshi Sato, Yuki Kimura, Hitoshi Suzuki, Yoshio Saito, Chihiro Kaito  JOURNAL OF CRYSTAL GROWTH  275-  (1-2)  E1745  -E1750  2005/02  [Not refereed][Not invited]
   

  The morphological alteration from delta- to alpha-Cr nanoparticles and the phase transition temperature were directly observed by in situ experiment using a transmission electron microscope. The icositetrahedral nanoparticle of delta-Cr transformed into a rhombic dodecahedral nanoparticle of alpha-Cr upon heating at 550 degrees C: It was demonstrated that the most stable shape of the alpha-Cr nanoparticle is the rhombic dodecahedron. Upon heating the alpha-Cr nanoparticle at 650 degrees C; the (1 1 3) layer of Cr2O3 grew topotactically in the direction of [100] of alpha-Cr nanoparticle. We concluded that the alpha-Cr nanoparticle includes about 20-30 at% oxygen, as estimated from the volume of the Cr2O3 surface layer. (C) 2004 Elsevier B.V. All rights reserved.
• Crystalline Mg2SiO4 and amorphous Mg-bearing silicate grain formation by coalescence and growth

  K Kamitsuji, H Suzuki, Y Kimura, T Sato, Y Saito, C Kaito  ASTRONOMY & ASTROPHYSICS  429-  (1)  205  -208  2005/01  [Not refereed][Not invited]
   

  A novel method for producing MgO and SiO2 smokes was developed. Mg-bearing silicate grain formation using the coalescence and growth of MgO and SiO2 grains was carried out in our laboratory. It becomes evident that single and poly crystalline Mg2SiO4 (forsterite) and amorphous Mg-bearing silicate grains can be produced by the coalescence and growth of MgO and SiO2 grains. This result suggests that the observed crystalline Mg2SiO4 grains and amorphous Mg-bearing silicate particles in Red Super Giant (RSG), Asymptotic Giant Branch (AGB), post-AGB and planetary nebula (PNe) could be produced by the coalescence and growth of MgO and SiO2 grains.
• Transition temperature to crystal phase of Al86Mn14 quasicrystal ultrafine particles determined by direct observation and characterization of surface oxide layer

  O Kido, H Suzuki, Y Kimura, T Sato, Y Saito, C Kaito  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES  25-  (4)  619  -624  2005/01  [Not refereed][Not invited]
   

  Al-Mn quasicrystal ultrafine particles can be produced by the advanced gas evaporation method (AGEM), which is a method of preparing ultrafine alloy particles by coalescence growth among the particles near the evaporation sources. We investigated the phase transition temperature from a quasicrystal to a stable crystal, by examining successive electron diffraction patterns of an ultrafine particle in an in situ experiment using a transmission electron microscope. In spite of the report that the Al86Mn14 quasicrystal transforms into the crystal phase at around 400-670 degreesC on thin film specimens, the quasicrystal ultrafine particle transformed at 800 degreesC, i.e., the quasicrystal ultrafine particle is more stable. Since the cross-sectional view of the surface oxide layer of the quasicrystal ultrafine particles can be easily observed, the surface oxides of eta-Al2O3 and MnO were characterized as a result of the oxidation of residual atoms on the surface of the produced alloy particles including the quasicrystals. The conditions required for Al-Mn quasicrystal ultrafine particle formation by the AGEM can be estimated under the cooling rate of 105 K/s. (C) 2004 Elsevier B.V. All rights reserved.
• Direct observation of the formation of alumina phase by metallic Al solid-SiO(2) solid reaction

  S Sasaki, H Suzuki, Y Kimura, T Sato, T Tanigaki, O Kido, K Kamitsuji, M Kurumada, C Kaito  EARTH PLANETS AND SPACE  57-  (5)  399  -401  2005  [Not refereed][Not invited]
   

  The formation of Al(2)O(3) phases by the solid-solid reaction of a metallic Al layer evaporated on a SiO(2) amorphous grain has been induced by heating above 600 degrees C in vacuum (1 x 10(-6) Pa). The distortion process of the amorphous SiO(2) grains by the formation of Al(2)O(3) have been directly imaged by in-situ TEM observation. A partly deposited Al layer covered the SiO(2) grains after heating at 750 degrees C, and gamma-Al(2)O(3) grains of about 25 nm diameters were formed on the SiO(2) surface. Upon the growth of Al(2)O(3), the SiO(2) grain decomposed into a mixture of metallic Si and SiO(2) and disappeared as a result of sublimation due to the formation of SiO(x) at high temperatures. The present result on dust surface dynamics will become an important field with respect to the metamorphism of grains from the astromineralogical viewpoint.
• Direct observation of the metamorphism of silicon oxide grains

  K Kamitsuji, S Ueno, H Suzuki, Y Kimura, T Sato, T Tanigaki, O Kido, M Kurumada, C Kaito  ASTRONOMY & ASTROPHYSICS  422-  (3)  975  -979  2004/08  [Not refereed][Not invited]
   

  Experimental studies on the metamorphism of SiO(x) grains under heating at 10(-6) Pa have been conducted using a high-resolution transmission electron microscope. Si crystallites were predominantly grown at 500 to 700 degreesC in SiO(x) grains. The Si crystallites disappeared at 800 degreesC and evaporated as the SiO phase.
• Growth of diamond from Si-containing amorphous carbon film using synchrotron radiation

  Y Kimura, O Kido, M Oomoto, K Ogawa, H Namba, C Kaito  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS  43-  (7A)  L888  -L890  2004/07  [Not refereed][Not invited]
   

  Si-doped amorphous carbon film prepared by the simultaneous vacuum evaporation of carbon and silicon has been irradiated by a synchrotron radiation (SR) beam. The preferential growth of diamond crystals was found by transmission electron microscope observation conducted after SR irradiation. It was also found that the solid-solution phase of carbon and silicon with the diamond structure was produced in the as-deposited film and at the initial stage of the crystallization. The solid-solution crystal remained in the stable phase up to 6 nm in size. The catalytic effect of Si was prominent in the growth of diamond.
• Phase transition temperature of gamma-Fe2O3 ultrafine particle

  O Kido, Y Higashino, K Kamitsuji, M Kurumada, T Sato, Y Kimura, H Suzuki, Y Saito, C Kaito  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN  73-  (7)  2014  -2016  2004/07  [Not refereed][Not invited]
   

  The iron oxide ultrafine particles prepared by the gas evaporation method, in which commercial alpha-Fe2O3 powder is evaporated, are composed of alpha-Fe2O3 particles covered with a gamma-Fe2O3 mantle layer. To study the phase transition temperature of the gamma-Fe2O3 mantle layer, the particles were heated and observed in a transmission electron microscope. The present specimen of gamma-Fe2O3 transformed completely to alpha-Fe2O3 at above 700degreesC, and this phase transition was irreversible. The phase transition temperature was 1.4 times higher than the bulk value. The growth mechanism of the present specimen of alpha-Fe2O3 particles covered with the gamma-Fe2O3 mantle layer has been discussed in terms of the difference in the cooling rates between the inside and the surface of the particle at around the evaporation source.
• Correlations between crystallite size, shape, surface, and infrared spectra using the Ti-C system

  Y Kimura, A Ikegami, M Kurumada, K Kamitsuji, C Kaito  ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES  152-  (2)  297  -301  2004/06  [Not refereed][Not invited]
   

  crystallites less than 10 nm in size showed an absorption feature at 14.3 mum. This 14.3 mum absorption was rarely seen in specimens ranging from bulk material to grains of 50 nm in size. The 14.3 mum feature was weakened as a result of the growth of TiC crystallites by heat treatment. When the carbide grains were covered with a carbon layer, the absorption peaks were considerably weakened, i.e., the absorption intensity depended on the grain surface state. A possible explanation is that the effects of size and shape on the spectra depend on the surface anisotropy.
• TEM study of early Ni4Ti3 precipitation and R-phase in Ni-rich NiTi nanoparticles

  M Kurumada, Y Kimura, H Suzuki, O Kido, Y Saito, C Kaito  SCRIPTA MATERIALIA  50-  (11)  1413  -1416  2004/06  [Not refereed][Not invited]
   

  The structure of NiTi shape memory alloy nanoparticles was determined by high-resolution electron microscopy. The mixture of Ni4Ti3 and R-phases was observed, which clearly showed lattice relationships of (2 (1) over bar 1)(B2)//(1 0 1)Ni4Ti3 and (2 (2) over bar 0)(B2)//(1 3 1)Ni4Ni3. Lattice images of an R-phase particle suggested the existence of a Ni-rich Guinier-Preston zone (G.P. zone). (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
• Growth and structure of Ge clusters produced by Ge-C co-evaporation

  S Tanaka, O Kida, M Kurumada, K Kamitsuji, Y Kimura, H Suzuki, Y Saito, C Kaito  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES  23-  (1-2)  108  -113  2004/06  [Not refereed][Not invited]
   

  Complete mixture films of carbon and germanium produced by the co-evaporation in vacuum were directly heated in a transmission electron microscope. It was noticed that the diffusion and growth of Ge dots in the mixture film take place at approximately 500degreesC. On the other hand, Ge dots coated with amorphous carbon were produced by simultaneous evaporation of carbon and Ge in Ar gas at 10 kPa. In addition to Ge clusters of 3-10 nm in size, multiple-twin Ge clusters with the size of 10 nm have been produced in carbon soot. These Ge clusters showed a diamond structure. The growth process of Ge clusters in amorphous carbon soot has been discussed using the result in the mixture film experiment and temperature distribution in the particle formation process. (C) 2004 Elsevier B.V. All rights reserved.
• Pentagonal configuration in GaP ultrafine particle

  T Tanigaki, Y Kimura, H Suzuki, M Kurumada, C Kaito  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN  73-  (5)  1375  -1376  2004/05  [Not refereed][Not invited]
  
• Novel method of doping tungsten into zinc oxide ultrafine particle using RF plasma system

  T Sato, H Suzuki, O Kido, M Kurumada, K Kamitsuji, Y Kimura, A Takeda, S Kaneko, Y Saito, C Kaito  JOURNAL OF CRYSTAL GROWTH  265-  (1-2)  149  -153  2004/04  [Not refereed][Not invited]
   

  A tungsten plate was set on a one-plate electrode in RF plasma using parallel plates in a mixed gas of argon (9.75 Torr) and oxygen (0.25 Torr). Zn smoke was introduced into the plasma field. W atoms were doped in the ZnO smoke formation field in the RF plasma system. The resulting particles with a size of 30 run were identified to be hexagonal ZnO particles. The collected particles changed from white to yellow, i.e., W atoms were doped into ZnO particles. The image of the (0 0 0 1) lattice, which is the forbidden reflection, appeared predominantly in the W-doped ZnO particle. Furthermore, by optical measurement. it Was found that the existence of W atoms can control the recombination radiation due to the exciton. On the basis of high-resolution transmission electron microscopic images, the doped W positions are discussed as being in the commensurate Configuration of W items in the ZnO crystal at positions equivalent to those in the cubic anti-fluoride structure. (C) 2004 Elsevier B.V. All rights reserved.
• 28pYE-9 Production of diamond nanoparticles by the simultaneous evaporation of C and Si in plasma field

  Kimura Y., Sato T., Suzuki H., Kaito C.  Meeting abstracts of the Physical Society of Japan  59-  (1)  920  -920  2004/03/03
• 28pYE-11 Morphology and structure of WO_3 ultrafine particles and their sublimation process

  Kurumada M, Kido O, Kamitsuji K, Kimura Y, Sato T, Suzuki H, Saito Y, Kaito C  Meeting abstracts of the Physical Society of Japan  59-  (1)  921  -921  2004/03/03
• 28pYE-12 Forsterite(Mg_2SiO_4) particle formation and crystallization

  Kamitsuji K., Sato T., Kimura Y., Suzuki H., Saito Y., Kaito C.  Meeting abstracts of the Physical Society of Japan  59-  (1)  921  -921  2004/03/03
• 28pYE-7 Transition temperature from δ- to α-Cr and the size dependence

  Kido Osamu, Suzuki Hitoshi, Kamitsuji Katsuya, Kurumada Mami, Soto Takeshi, Kimura Yuki, Saito Yoshio, Kaito Chihiro  Meeting abstracts of the Physical Society of Japan  59-  (1)  920  -920  2004/03/03
• 28pYE-8 Size control and sublimation process of CdS ultrafine particles

  Kinuta Y., Suzuki H., Kodama S., Kurumada M., Kido O., Tanigaki T., Kimura Y., Saito Y., Kaito C.  Meeting abstracts of the Physical Society of Japan  59-  (1)  920  -920  2004/03/03
• 28pYE-10 Solid reaction between Sn-Pb mixed particle and metal

  Shintaku M., Suzuki H., Kimura Y., Tanigaki T., Kido O., Sato T., Saito Y., Kaito C.  Meeting abstracts of the Physical Society of Japan  59-  (1)  921  -921  2004/03/03
• Production and structural characterization of carbon soot with narrow UV absorption feature

  Y Kimura, T Sato, C Kaito  CARBON  42-  (1)  33  -38  2004  [Not refereed][Not invited]
   

  In the present study, by a simple method, carbon soot with a narrow absorption features at around 220 nm was produced by pyrolysis of methane gas at a hot (1400-2800degreesC) filament. A detailed correlation between the structure and the optical spectra of carbon soot was carried out using a high-resolution transmission electron microscope. It appears that the origin of the narrow absorption peak is an onion-like graphitic structure. Interestingly, we found that the absorption peak position and the size of the soot can be controlled by the production temperature. The absorption peak is located at 217.5 nm, i.e., at the position of an intense interstellar absorption, when the onion structure has about 5 nm diameter. Infrared spectroscopy was applied to further elucidate the chemical composition of the obtained soot. (C) 2003 Elsevier Ltd. All rights reserved.
• Direct observation of sublimation process on a CdTe(111) surface using an ultrafine particle

  T Tanigaki, Y Kimura, H Suzuki, C Kaito  JOURNAL OF CRYSTAL GROWTH  260-  (3-4)  298  -303  2004/01  [Not refereed][Not invited]
   

  A particle with a CdTe core and carbon mantle was produced by the advanced carbon-coating method which enables direct coverage with a carbon layer using an electron microscope. The coagulated particles containing approximately 30-200 CdTe particles produced by the gas evaporation method were covered with a carbon layer of about 7 nm thickness at 300 degreesC. By heating these particles above 500 degreesC, the sublimation process of a part of the CdTe particle can be directly captured by high-resolution transmission electron microscopy and recorded in real time on videotape. Sublimation on the CdTe(111) surfaces occurred in the step flow mode of two (111) layers. It was observed that two (111) zinc-blende layers changed to the (0002) wurtzite configuration unit just before sublimation. The condensation of CdTe on the sublimated particle surface and growth of CdTe in the carbon layers were also captured in the video image. These sublimation processes were discussed in terms of the existence of the polarity of II-VI compounds. (C) 2003 Elsevier B.V. All rights reserved.
• Mechanism of copper selenide growth on copper-oxide-selenium system

  Y Ishikawa, O Kido, Y Kimura, M Kurumada, H Suzuki, Y Saito, C Kaito  SURFACE SCIENCE  548-  (1-3)  276  -280  2004/01  [Not refereed][Not invited]
   

  Transmission electron microscopy was used to study spontaneous copper selenide formation on Cu particles covered with an oxide layer. Even if the copper particle surface was covered with a Cu2O layer, selenides were formed by diffusion through the metal oxide layer. For a particle size less than 50 nm, selenide was formed in Cu particles by the diffusion of Se atoms passing through the Cu2O layer. For particles larger than 100 nm in size, selenide was formed in Se film. It was also found that the thickness of the Cu2O layer on the surface of Cu particle accelerated diffusion of Se atoms to the copper particle. (C) 2003 Elsevier B.V. All rights reserved.
• Effect of RF plasma field on the growth of C-60 crystals

  T Sato, O Kido, M Kurumada, Y Kimura, H Suzuki, Y Saito, C Kaito  CARBON  42-  (8-9)  1875  -1877  2004  [Not refereed][Not invited]
  
• Structure and thickness of natural oxide layer on ultrafine particle

  K Tamura, Y Kimura, H Suzuki, O Kido, T Sato, T Tanigaki, M Kurumada, Y Saito, C Kaito  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS  42-  (12)  7489  -7492  2003/12  [Not refereed][Not invited]
   

  Ultrafine particles of various metals [Cr, Mn, Fe, Al, Ni, Cu, In, Si, Ge, Zn, Mg and Sn], produced by the gas evaporation method were covered with the oxide layer of thickness less than 10 nm by exposure to air. In order to clarify the structure and thickness of the surface oxide layer, on various metal ultrafine particles, high-resolution electron microscopy and infrared spectroscopy have been extensively used.
• 非晶質シリケイトの高温での挙動の直接観察

  上辻勝也, かい内千尋, 木村勇気, 鈴木仁志, 佐藤岳志, 谷垣俊明, 城戸修, 車田真実, 塚本勝男  日本岩石鉱物鉱床学会学術講演会講演要旨集  2003-  144  2003/09/28  [Not refereed][Not invited]
  
• プラズマ中でのカーボングレインの挙動

  佐藤岳志, 上辻勝也, 木村勇気, 鈴木仁志, 谷垣俊明, 城戸修, 車田真実, かい内千尋, 塚本勝男  日本岩石鉱物鉱床学会学術講演会講演要旨集  2003-  143  2003/09/28  [Not refereed][Not invited]
  
• Dynamic behavior of SiO- and SiO2-coated ZnO ultrafine particles and growth mechanism of Zn2SiO4 crystal

  T Tanigaki, H Suzuki, Y Kimura, O Kido, Y Saito, C Kaito  JOURNAL OF CRYSTAL GROWTH  256-  (3-4)  317  -323  2003/09  [Not refereed][Not invited]
   

  In order to elucidate the stability of a silicon oxide layer on zoo, the dynamic behavior of SiO- and SiO2-layer-coated ZnO ultrafine particle surfaces were directly observed by heating in a transmission electron microscope up to 700degreesC. In the case of SiO-coated ZnO ultrafine particles, ZnO nanocrystallites with the size of 2 nm grew in the SiO layer at 500degreesC. In the case of SiO-coated ZnO ultrafine particles, beta-cristobalite with the size of 10nm order was grown at 600degreesC. Zn2SiO4 particles were grown by coalescence between beta-cristobalite and ZnO at 700degreesC. By comparing the SiO and SiO, layers on ZnO ultrafine particles, it was found that the behaviors of the two silicon oxide layers are clearly different. (C) 2003 Elsevier B.V. All rights reserved.
• Structural control of silicon oxide particles by oxygen partial pressure in RF plasma

  T Sato, A Takeda, Y Kimura, H Suzuki, Y Saito, C Kaito  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS  42-  (9A)  5896  -5897  2003/09  [Not refereed][Not invited]
   

  Amorphous silicon oxide particles with the size of 30-100 nm were produced by spraying Si(C2H5O)(4) liquid into a plasma region. Plasma was generated at a high pressure of 10 Torr in a mixture gas of argon and oxygen. The production of two silicon oxide particles with the structure of SiO and SiO2 could be controlled by the oxygen partial pressure in plasma.
• Solid reaction between Sn-Zn mixed particle and metal particle

  Shintaku Masayuki, Suzuki Hitoshi, Kimura Yuki, Sato Takeshi, Kido Osamu, Kaito Chihiro  Meeting abstracts of the Physical Society of Japan  58-  (2)  767  -767  2003/08/15
• Transition Temperature from γ-to α-phase on Cr nano-particles

  Kido Osamu, Suzuki Hitoshi, Nakashima Yasuko, Kamitsuji Katsuya, Ikegami Akimi, Kurumada Mami, Sato Takeshi, Kimura Yuki, Saito Yoshio, Kaito Chihiro  Meeting abstracts of the Physical Society of Japan  58-  (2)  767  -767  2003/08/15
• Production of BaTiO_3 ultrafine particles and their structures

  Kodama S., Suzuki H., Kido O., Kamitsuji K., Kurumada M., Tanigaki T., Kimura Y., Saito Y., Kaito C.  Meeting abstracts of the Physical Society of Japan  58-  (2)  768  -768  2003/08/15
• Production of InN and In_2O_3 ultrafine particles using RF plasma field in gas atmosphere

  Kuga T., Sato T., Suzuki H., Kido O., Kurumada M., Kimura Y., Saito Y., Kaito C.  Meeting abstracts of the Physical Society of Japan  58-  (2)  768  -768  2003/08/15
• Titanium carbide particles as pre-solar grains

  Y Kimura, C Kaito  MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY  343-  (2)  385  -389  2003/08  [Not refereed][Not invited]
   

  Focusing on the growth of metal carbide particles and the formation of pre-solar grains, a new attempt has been made for titanium carbide (TiC) systems. Using the noble gas evaporation method, we succeeded in producing TiC core (50-nm) carbon mantle (2-nm) grains of the same core size as pre-solar grains. The infrared spectrum has broad absorption features at 9.5 and 12.5 mum. It was also found that these absorption peaks became weaker by an increase to 15 nm of carbon mantle layer. The determination method of the contact angle of carbon on the TiC grain has been developed using a high-resolution electron microscopic technique. The contact angles between TiC and carbon were and on the (111) and (100) TiC grain surfaces, respectively.
• Dynamic behavior of Au cluster on the surface of silicon nanoparticles

  Y Kimura, H Ueno, H Suzuki, T Tanigaki, T Sato, Y Saito, C Kaito  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES  19-  (3)  298  -302  2003/08  [Not refereed][Not invited]
   

  The high-temperature behavior of Au clusters on a Si nanoparticle surface has been studied using the atomic-resolution high-temperature stage of a transmission electron microscope. Au atoms diffuse into the Si nanoparticle at 680degreesC and return to the surface at room temperature. The movement of diffused Au atoms on the Si surface steps and the movement of Guinier-Presion-zone-like contrast observed for the segregation of An atoms on the (lll) Si plane, have been directly observed. These phenomena, which can be detected only at high temperatures, are presented in this paper. (C) 2003 Elsevier B.V. All rights reserved.
• Growth process of TiC clusters from Ti nanoparticles with evaporated carbon layer

  A Ikegami, Y Kimura, H Suzuki, T Sato, T Tanigaki, O Kido, M Kurumada, Y Saito, C Kaito  SURFACE SCIENCE  540-  (2-3)  395  -400  2003/08  [Not refereed][Not invited]
   

  Titanium carbide formation by the solid-solid reaction on the surface of Ti nanoparticles was studied in situ using a high-resolution transmission electron microscope with a heating stage. The cross-sectional image of the Ti surface was clearly observed. Vacuum-deposited carbon covered the whole the surface of Ti nanoparticles in spite of the partly evaporation on the nanoparticle surface. The diffusion of the carbon atoms inside the Ti nanoparticles depended on the size of the nanoparticles. When the Ti nanoparticle diameter was less than 30 nm, carbon atoms diffused into the Ti nanoparticle and formed TiC. The superstructure of the Ti nanoparticles was observed, which revealed the growth process of TiC to be the diffusion of carbon atoms. For Ti nanoparticles with diameter larger than 30 run it was observed that diffusion of Ti atoms into the carbon layer was dominant, which resulted in formation of TiC in the carbon layer at the surface of Ti nanoparticles. (C) 2003 Elsevier B.V. All rights reserved.
• Structure and optical spectrum of ZnO nanoparticles produced in RF plasma

  T Sato, T Tanigaki, H Suzuki, Y Saito, O Kido, Y Kimura, C Kaito, A Takeda, S Kaneko  JOURNAL OF CRYSTAL GROWTH  255-  (3-4)  313  -316  2003/08  [Not refereed][Not invited]
   

  ZnO particles were produced by dropping Zn powder into a heated boat just below the plasma electrodes in a mixture gas of argon and oxygen. The resulting particles look spherical with the size of 30 nm and were of tetrapod configuration having four [0 0 0 1] axes of ZnO. The dispersion became better than that in the case of another method without plasma. The ultraviolet-visible light transmittance of the specimen showed sharp absorption. The electric charge in the plasma field controlled the coalescence growth of each particle and improved the dispersion of the particles due to the plasma effect. (C) 2003 Elsevier Science B.V. All rights reserved.
• Crystallization of carbon film containing metal atoms by vacuum heating

  KIMURA Y., TANIGAKI T., SUZUKI H., SATO T., KAITO C.  Journal of the Japanese Association of Crystal Growth  30-  (3)  16  -16  2003/07/05  

  Generally, several metals, such as Ni, Fe, Co and Mo, were doped as the catalysis on the production of diamond, fullerene and carbon nanotube. In the present method, heat treated carbon films containing such metale were analyzed based on transmission electron microscope technique. The difference of crystallization by doped metal has been elucidated. Present result will give the development to a wide range of new opportunities for research and applications in the field of nanotechnology.
• Properties and structure studies of R-phase on NiTi shape memory alloy nanoparticle

  KURUMADA Mami, KIMURA Yuki, SUZUKI Hitoshi, KIDO Osamu, SAITO Yoshio, KAITO Chihiro  Journal of the Japanese Association of Crystal Growth  30-  (3)  40  -40  2003/07/05  

  NiTi shape memory alloy nanoparticles were produced by the flash gas evaporation from the 50 at.% Ni-Ti mixture powder. The superlattice image of B2-phase that is called as the characteristic structure of R-phase has been captured by the high resolution electron microscopic image. The core of particle was R-phase and the mantle layer was B2-phase. These particles were heated directly in the electron microscope. It became evidently that R-phase has never changed to B2-phase, although the temperature has been much higher than the bulk's transition temperature. Therefore the R-phase is one of the stable phase at high temperature.
• Forsterite particle formation by coalescence growth of MgO and SiO_2 smoke particles

  KAMITSUJI Katsuya, SUZUKI Hitoshi, KIMURA Yuki, SAITO Yoshio, KAITO Chihiro  Journal of the Japanese Association of Crystal Growth  30-  (3)  34  -34  2003/07/05  

  In order to find the forsterite formation condition of crystalline grain, we achieved the coalescence experiment between MgO and SiO_2 smokes. It was found that foresterite spherical particles with the size of a few hundred nm in diameter were produced by the coalescence between cubic-shaped MgO particles and spherical SiO_2 particles.
• Dynamics of Al clusters on SiO_2 nanoparticles by in situ observation

  SASAKI S., KIMURA Y., SAITO Y., TAKEDA A., KAITO C.  Journal of the Japanese Association of Crystal Growth  30-  (3)  35  -35  2003/07/05  

  In order to clarify the characteristic of nanoparticle, temperature dependence of SiO_2 particle deposited Al clusters have been analyzed by transmission electron microscope. We produced Al clusters deposited SiO_2 nanoparticles. We found that a part of Al clusters changed to ν-Al_2O_3 crystalline phase at 600℃ and SiO_2 nanoparticles started to sublimate as SiO gas at 800℃.
• Structure of Copper Oxide Ultrafine Particles Produced in an Electric Field

  SUZUKI Hitoshi, SATO Takeshi, KIMURA Yuki, SAITO Yoshio, KAITO Chihiro  Journal of the Japanese Association of Crystal Growth  30-  (3)  36  -36  2003/07/05  

  Our developed method to separate oxide ultrafine particles in smoke has been used on the formation of copper oxide particles produced by the evaporation of metallic copper in a mixture gas. Yellow and white spherical particles were gathered on the negative and positive electrode . The yellow particles were crystalline particle of cuprite and paramelaconite. The white particles were amorphous, Since the white particles were gathered on the positive electrode, the oxide is excess oxygen particles. The detail analysis on these white cupper oxide particles is under way.
• Production of TiC nanocrystallites correlation between its size and infrared spectra

  IKEGAMI A., KIMURA Y., SUZUKI H., SAITO Y., KAITO C.  Journal of the Japanese Association of Crystal Growth  30-  (3)  41  -41  2003/07/05  

  Present TiC crystallites with the size of less than 3 nm were shown at 14 μm absorption feature. This 14 μm absorption was hardly seen from the bulk to 50 nm size. The absorption feature at 14 μm was weakening due to the growth of TiC crystallites by the heat treatment. Moreover the absorption intensity was depended on the grain surface, i.e., if the carbide grains were covered with carbon layer as is observed in the meteorite, the absorption peaks were remarkably weakening.
• In situ observation of silicon carbide formation process using electron microscope

  M Ishikawa, Y Kimura, H Suzuki, O Kida, T Tanigaki, T Sato, Y Saito, C Kaito  JOURNAL OF CRYSTAL GROWTH  254-  (1-2)  131  -136  2003/06  [Not refereed][Not invited]
   

  The silicon core and carbon mantle particles were produced by using the advanced carbon coating method which enables direct covering with the carbon layer using an electron microscope. The growth of SiC crystal was observed upon heating at 500degreesC in vacuum. The growth process of SiC on both the carbon layer and silicon particles was directly observed by in situ observation. The inward movement of carbon into silicon began at the twinned part. The growth rate of SiC on the carbon mantle layer was estimated from in situ images and found to be 8 times faster than the growth rate of silicon carbide in silicon particles. (C) 2003 Elsevier Science B.V. All rights reserved.
• Dynamic behavior of a silicon oxide layer on silicon ultrafine particles

  Y Kimura, H Ueno, H Suzuki, T Sato, T Tanigaki, O Kido, C Kaito, Y Saito  SURFACE REVIEW AND LETTERS  10-  (2-3)  361  -364  2003/04  [Not refereed][Not invited]
   

  In order to clarify the high-temperature behavior of a silicon oxide layer on the surface of Si ultrafine particles, the oxide layer has been studied using the atomic-resolution high-temperature stage of a transmission electron microscope. The natural oxide layer grown on Si ultrafine particles by exposure to air was an amorphous silicon oxide layer with a thickness of 1.5 nm. This oxide layer started to dissolve into the Si crystal upon heating at 500degreesC, and was fully dissolved into the Si crystal at 600degreesC in vacuum. When the specimen was cooled back to room temperature, the silicon oxide layer reappeared on the Si surface. This phenomenon, which can be detected only at high temperatures, is presented in this paper.
• Atomic observation of the sublimation process of the Pb (111) surface

  T Tanigaki, H Suzuki, Y Kimura, C Kaito, Y Saito  SURFACE REVIEW AND LETTERS  10-  (2-3)  455  -459  2003/04  [Not refereed][Not invited]
   

  The dynamic behavior of the sublimation process using ultrafine Pb particles produced by the gas evaporation technique was examined at the level of atomic resolution using a transmission electron microscope equipped with a real-time video-recording system. The ultrafine Pb particles coated with a carbon layer with a thickness of the order of 5 nm were prepared in the electron microscope by heating particles on carbon film at 300degreesC. Sublimation of the Pb particle covered with the carbon layer took place above 470degreesC, which is slightly higher than the melting point of Pb. Sublimation occurred at the surface with a higher surface energy. The sublimation process of the (111) surface was clearly observed at an atomic level. It was found that two- or four-atomic-layer step flow was observed at the (111) surface. At the (111) surface between the stacking faults, two-layer and successive one-layer sublimation occurred.
• Dynamic process of crystallization of Sb2Se3 from Sb50Se50 amorphous film

  M Kurumada, H Suzuki, Y Kimura, Y Saito, C Kaito  JOURNAL OF CRYSTAL GROWTH  250-  (3-4)  444  -449  2003/04  [Not refereed][Not invited]
   

  Dynamics of crystallization of amorphous antimony-selenium film deposited on carbon substrate have been studied by the high-resolution transmission electron microscopy. The amorphous film was suddenly crystallized at 200degreesC by heating in vacuum. By the electron beam irradiation crystallization occurred at the focused electron beam region in the amorphous film. The growth process of crystallization by electron beam irradiation was recorded on a video image at the atomic resolution mode. The growth front of crystallization showed nano-concave and -convex shapes. The recrystallization with the different orientation at the first grown crystal have been found, and discussed as the influence of remaining antimony crystallites at the first crystallized film region. (C) 2003 Elsevier Science B.V. All rights reserved.
• High-temperature behavior of an amorphous carbon layer on SiC particles

  Yuki Kimura, Yoshio Saito, Chihiro Kaito  Surface Science  527-  (1-3)  L219  -L221  2003/03/10  [Not refereed][Not invited]
   

  The dynamic behavior of an amorphous carbon layer of 3 nm thickness on a SiC particle was examined at high temperature using a high-resolution electron microscope equipped with a real-times video recording system. It was found that the surface carbon layer began to solve into the SiC particle at 600 °C. The layer was completely solved into SiC crystal at 800 °C. The lattice image of SiC changed negligibly at high temperature. If the specimen was cooled back to room temperature, the carbon layer on the SiC particle was recovered. © 2002 Elsevier Science B.V. All rights reserved.
• Crystallization on mixture film of silicon and carbon

  Kimura Yuki, Ishikawa Manabu, Tanigaki Toshiaki, Suzuki Hitoshi, Saito Yoshio, Kaito Chihiro  Meeting abstracts of the Physical Society of Japan  58-  (1)  835  -835  2003/03/06
• Production of ZnO particle produced by flash evaporation in RF plasma

  Sato Takeshi, Tanigaki Toshiaki, Suzuki Hitoshi, Saito Yoshio, Kimura Yuki, Kaito Chihiro  Meeting abstracts of the Physical Society of Japan  58-  (1)  835  -835  2003/03/06
• In situ observation of dendrite growth from ZnO whisker

  Suzuki Hitoshi, Tanigaki Toshiaki, Kimura Yuki, Saito Yoshio, Kaito Chihiro  Meeting abstracts of the Physical Society of Japan  58-  (1)  834  -834  2003/03/06
• The shapes and structure of the ultrafine particles in Ni-Ti alloy system

  Kurumada M., Suzuki H., Kimura Y., Saito Y., Kaito C.  Meeting abstracts of the Physical Society of Japan  58-  (1)  835  -835  2003/03/06
• in situ observation of the dynamic behavior of GaP ultra fine particles at high temperature

  Tanigaki Toshiaki, Kimura Yuki, Suzuki Hitoshi, Kido Osamu, Kaito Chihiro  Meeting abstracts of the Physical Society of Japan  58-  (1)  835  -835  2003/03/06
• Novel method for the preparation of silicon oxide layer on TiO2 particle and dynamic behavior of silicon oxide layer on TiO2 particle

  Y Atou, H Suzuki, Y Kimura, T Sato, T Tanigaki, Y Saito, C Kaito  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES  16-  (2)  179  -189  2003/02  [Not refereed][Not invited]
   

  Two methods for the preparation of TiO2 particles using the gas evaporation methods have been proposed. A method for selective growth of the anatase and/or rutile particles as well as a method of covering TiO2 particles with an SiO2 layer has been developed. The process of dissolving the SiO2 layer into TiO2 particles has been observed by an in situ observation using high-resolution electron microscopy. SiO2 layers of 5 nm order were dissolved completely into TiO2 particles of the order of 30 nm at 750degreesC. These SiO2 layers appeared again at room temperature on the surfaces of TiO2 particles. This phenomenon was observed only at a high temperature. By the use of the phenomenon of dissolving the SiO2 layer into TiO2 particles at high temperature, the growth of TiO2 particles covered with the SiO2 layer has been discussed. (C) 2002 Elsevier Science B.V. All rights reserved.
• Characteristic crystal growth from amorphous WO3 film by vacuum heating

  Y. Kimura, C. Kaito  Journal of Crystal Growth  250-  (3-4)  450  -457  2003  [Not refereed][Not invited]
  
• Production of nanodiamond from carbon film containing silicon

  Y. Kimura, C. Kaito  Journal of Crystal Growth  255-  (3-4)  282  -285  2003  [Not refereed][Not invited]
  
• Infrared spectra of ZrC presolar grain analogues

  Y. Kimura, C. Kaito  Astronomy and Astrophysics  409-  159  -161  2003  [Not refereed][Not invited]
  
• Characteristic behavior of Bi clusters and growth process to the continuous film

  C Kaito, Y Kimura, S Tominaga, S Kimura, T Nakada, Y Saito  PHYSICS OF LOW-DIMENSIONAL STRUCTURES  5-6-  1  -7  2003  [Not refereed][Not invited]
   

  The instability of the Bi cluster predicted on the surface of amorphous carbon substrate under electron beam observation has been captured in high-resolution electron microscope video images, which indicates the intuitive nature of the cluster. It is also shown that the intuitive nature of the clusters is important for the growth process of the film. With the changing of the film thickness up to 15 nm, the marked changes in the growth orientation have been observed.
• Are TiC grains a carrier of the 21-μm emission band observed around the post-AGB objects?

  T. Chigai, T. Yamamoto, C. Kaito, Y. Kimura  The Astrophysical Journal  587-  (2)  771  -776  2003  [Not refereed][Not invited]
  
• Demonstration of crystalline forsterite grain formation due to coalescence growth of Mg and SiO smoke particles

  C Kaito, Y Ojima, K Kamitsuri, O Kido, Y Kimura, H Suzuki, T Sato, T Nakada, Y Saito, C Koike  METEORITICS & PLANETARY SCIENCE  38-  (1)  49  -57  2003/01  [Not refereed][Not invited]
   

  Experimental studies of coalescence between Mg grains and SiO grains in smoke reveal the direct production of crystalline forsterite grains. The present results also show that different materials can be produced by grain-grain collisions, which have been considered one of the models of grain formation in the interstellar medium. The fundamentals of coalescence growth in smoke, which have been developed in our series of experiments, are presented in this paper. Mg2Si polyhedral grains were obtained in a Mg grain-rich atmosphere. Mg2SiO4 polyhedral grains were obtained in a SiO grain-rich atmosphere. The IR spectra of the resultant grains showed the characteristics of crystalline forsterite.
• Alteration of interstellar organic materials in meteorites' parent bodies: a novel route for diamond formation

  H Nakano, A Kouchi, M Arakawa, Y Kimura, C Kaito, H Ohno, T Hondoh  PROCEEDINGS OF THE JAPAN ACADEMY SERIES B-PHYSICAL AND BIOLOGICAL SCIENCES  78-  (9)  277  -281  2002/11  [Not refereed][Not invited]
   

  Based on experiments that model interstellar organic materials, we found that both C and N contents and IR spectra of insoluble organic materials in carbonaceous chondrites could be reproduced well by the aqueous alteration and the subsequent thermal metamorphism. The resulting sample shows strong evidence of diamond, which indicates that this process is an unexpected mechanism that might produce extensive amount of diamond in meteorites' parent bodies. Because this process requires neither high pressures nor energetic processes, the present results suggest an alternate origin of diamonds in meteorites.
• Fabrication of an amorphous carbon tube from copper oxide whisker

  H Suzuki, N Fukuzawa, T Tanigaki, T Sato, O Kido, Y Kimura, C Kaito  JOURNAL OF CRYSTAL GROWTH  244-  (2)  168  -172  2002/10  [Not refereed][Not invited]
   

  The reduction process of tenorite whiskers grown on a copper mesh by heating in vacuum has been directly observed using a transmission electron microscope equipped with a real-time video-recording system. The coating of the carbon layer and reduction of the tenorite whisker covered with a carbon layer have also been captured in real time on video images. The growth process of an amorphous carbon tube has been elucidated. (C) 2002 Elsevier Science B.V. All rights reserved.
• In-situ Observation of Phase Transition on Quasicrystal Ultrafine Particles in Transmission Electron Microscope

  Kido O., Suzuki H., Kimura Y., Saito Y., Kaito C.  Meeting abstracts of the Physical Society of Japan  57-  (2)  769  -769  2002/08/13
• High-temperature behavior of PbTe particles

  Kaito C., Tanigaki T., kimura Y., Suzuki H.  Meeting abstracts of the Physical Society of Japan  57-  (2)  768  -768  2002/08/13
• Production of presolar grains and its infrared spectra

  Kimura Yuki, Kaito Chihiro  Meeting abstracts of the Physical Society of Japan  57-  (2)  768  -768  2002/08/13
• In-situ observation of TiC production process on solid reaction.

  Ikegami A., Kimura Y., Suzuki H., Saito Y., Kaito C.  Meeting abstracts of the Physical Society of Japan  57-  (2)  768  -768  2002/08/13
• Irradiation effect of synchrotron radiation on crystallization of thin amorphous WO3 film

  Y Kimura, K Hanamoto, Y Nakayama, C Kaito  NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS  194-  (2)  187  -192  2002/08  [Not refereed][Not invited]
   

  In order to elucidate the effect of synchrotron radiation (SR) irradiation on crystal growth, crystallization of WO3 films has been performed in vacuum under SR irradiation. The main results were compared with the results of heat treatment of the same film. Upon SR irradiation for 80 s using a toroidal mirror, a catastrophic change occurred, i.e. W3O crystals (A-15 type) with a size of less than 30 nm appeared. Decomposition of the WO3 film started at above 750 degreesC during vacuum heating. W, WO2 and incommensurate WO3 crystals appeared. W3O crystal produced neither intense electron beam irradiation nor vacuum heating. These results will be discussed in terms of the differences caused by excitation with a SR beam, i.e. strong inner shell excitation and ionization of W and O may have taken place. (C) 2002 Elsevier Science B.V. All rights reserved.
• Process of crystallization in thin amorphous tin oxide film

  T Kobayashi, Y Kimura, H Suzuki, T Sato, T Tanigaki, Y Saito, C Kaito  JOURNAL OF CRYSTAL GROWTH  243-  (1)  143  -150  2002/08  [Not refereed][Not invited]
   

  Amorphous tin oxide films deposited on carbon substrates have been studied by high-resolution transmission electron microscopy. As-deposited film was composed of a mixture of microcrystallites of SnO, SnO2 and SnO3 with size of 2 nm. Crystallization took place above 450degreesC. SnO crystals appeared between 450degreesC and 500degreesC, whereas SnO2 crystals appeared above 550degreesC. The appearance of beta-tin crystals with the reduction of tin oxide has been verified using the heating stage of the electron microscope. A drop of liquid tin was recognized upon heating above 500degreesC. The difference in crystallization upon applying an electron beam, synchrotron radiation and heating in vacuum has been summarized and discussed with respect to the problem of the excitation of crystallites. (C) 2002 Elsevier Science B.V. All rights reserved.
• Mechanism of spontaneous copper selenide formation

  ISHIKAWA Yohsuke., KIMURA Yuki, SUZUKI Hitoshi, SAITO Yoshio, KAITO Chihiro  Journal of the Japanese Association of Crystal Growth  29-  (2)  165  -165  2002/07/01  

  Spontaneous copper selenide formation was studied by the use of Cu particles which were partly deposited Se amorphous films. The selenide crystals were formed in both selenium films and Cu particles. If the surface of Cu particles were covered with Cu2O thin layer, the direction of Se atoms was changed by the Cu particle size. In large size (130nm), selenide was formed in both Cu particle and Se film. In small size (40nm), selenide was formed in Cu particle by the diffusion of Se atoms passed through the Cu2O layer.
• Production of carbon grains by RF plasma

  SATO T., SAITO Y., KIMURA Y., SUZUKI H., KAITO C.  Journal of the Japanese Association of Crystal Growth  29-  (2)  159  -159  2002/07/01  

  In order to elucidate the correlation between production of carbon grains and plasma effect, carbon smoke was passed through the plasma field. Characteristic structure changes have been observed by passing through the plasma region.
• In-situ observation of Silicon Carbide formation process by ACCM.

  ISHIKAWA Manabu., KIMURA Yuki, SUZUKI Hitoshi, SAITO Yoshio, KAITO Chihiro  Journal of the Japanese Association of Crystal Growth  29-  (2)  161  -161  2002/07/01  

  By heating of the silicon core-carbon mantle particles produced by ACCM (Advanced Carbon Coating Method), formation process of α-SiC particles by the solid reaction between carbon and silicon have been observed by the use of electron microscopic heating stage. α-SiC particles were produced at 500℃. The diffusion of silicon into carbon mantle and carbon into silicon crystal has been observed. Two processes on the formation of silicon carbide are discussed as the size effect of silicon particles.
• Production of presolar grains by the gas evaporation method

  KIMURA Yuki, KAITO Chihiro.  Journal of the Japanese Association of Crystal Growth  29-  (2)  106  -106  2002/07/01  

  In spite of the increasing interest on the carbide grain formation by the identification as the pre-solar grain, the laboratory experiments on the carbide were hardly achieved. A new attempt has been made for carbide core (SiC, TiC, ZrC etc.)-carbon mantle grains. Using the noble gas evaporation method, we succeeded in producing carbide core-carbon mantle grains with the same size as carbide core of pre-solar grains.
• The structure and growth mechanism of rod shaped Mn ultrafine particles

  KIDO Osamu., SHINTAKU Masayuki, KIMURA Jun., KIMURA Yuki, SUZUKI Hitoshi, SAITO Yoshio, KAITO Chihiro  Journal of the Japanese Association of Crystal Growth  29-  (2)  164  -164  2002/07/01  

  Mn ultrafine particles prepared by gas evaporation method consist of mainly α-Mn particles and p-Mn particles, which have the habits of tristetrahedron and rhombic dodecahedron. But the structure of the rod shaped Mn ultrafine particles was unknown. The structure and morphology of this particle have been elucidated on the basis of selected area electron diffraction. The planer defects along to <110> direction have been included predominately for the rod shaped particle.
• Iron silicate formation by coalescence growth of Fe and SiO particles

  KAMITSUJI Katsuya, SAITO Yoshio, SUZUKI Hitoshi, KIMURA Yuki, KAITO Chihiro.  Journal of the Japanese Association of Crystal Growth  29-  (2)  107  -107  2002/07/01  

  With the increasing interest of crystalline silicate grains, smoke experiment on the formation of FeSiO_3 grains have been done by the coalescence growth between Fe and SiO particles. In addition to FeSiO_3 crystal grains, FeSi_2 grains were produced even in the present method. FeSi_2 and FeSiO_3 growth have been discussed as the problem of Si and O rich conditions.
• Structure and formation of Ge cluster produced by Ge-C co-evaporation

  TANAKA Shuji, KIMURA Yuki, SUZUKI Hitoshi, SAITO Yoshio, KAITO Chihiro  Journal of the Japanese Association of Crystal Growth  29-  (2)  160  -160  2002/07/01  

  Structures of Ge clusters covered with carbon have been studied by high resolution electron microscopy. The Ge clusters of diamond structure have been produced in carbon particles. Twin or Pentagonal decahedron of germanium with the size of 10nm was produced. The growth process of Ge clusters from the Ge-C mixture film at 500℃ is also shown.
• Growth process of carbyne crystals by synchrotron irradiation

  Yuki Kimura, Chihiro Kaito, Katsumi Hanamoto, Muneo Sasaki, Seiji Kimura, Toshitaka Nakada, Yoshio Saito, Yasuyuki Nakayama  Carbon  40-  (7)  1043  -1050  2002/06  [Not refereed][Not invited]
   

  Growth of small carbyne crystals in a thin amorphous carbon film has been observed by high-resolution transmission electron microscopy (HRTEM). The as-deposited film was composed of diamond and graphite crystallites of size 1 nm. Circular α-phase carbyne crystals predominantly grew to 20 nm in size and transformed into (α+β)-phase crystals with an elongated shape of 100 nm in length. The typical correlation during the transformation is (220α//(301)α+β. The c-axes of both grown crystals were oblique to the direction of the electron beam. The growth process of carbyne crystals will be discussed in terms of selective excitation of graphite crystallites by an SR beam. © 2002 Elsevier Science Ltd. All rights reserved.
• Effects of SR irradiation on tin-doped indium oxide thin film prepared by rf magnetron sputtering

  M Sasaki, K Hanamoto, Y Kimura, C Kaito, H Miki, Y Nakayama  REVIEW OF SCIENTIFIC INSTRUMENTS  73-  (3)  1384  -1386  2002/03  [Not refereed][Not invited]
   

  The effects of synchrotron radiation (SR) irradiation on the electrical properties of tin-doped In2O3 (ITO) thin films prepared by rf magnetron sputtering have been studied. A white SR beam focused by a cylindrical mirror was used to irradiate ITO thin films at doses of 0.35, 1.98, 3.50, and 6.64 mA h. We have achieved resistivity of 2x10(-4) Omega cm on ITO thin film at an irradiation dose of 3.5 mA h without extra heating. The mobility of the ITO films did not decrease after SR irradiation. The electrical properties in connection with the structural change due to SR are discussed. (C) 2002 American Institute of Physics.
• Spontaneous mixing of binary alkali halide crystal by successive evaporation

  Y Kimura, Y Saito, T Nakada, C Kaito  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES  13-  (1)  11  -23  2002/01  [Not refereed][Not invited]
   

  Experimental studies on the mixing of alkali halide clusters of 200 nm sizes were performed systematically by the successive evaporation of different alkali halides on carbon substrates. The alkali halides used were NaCl, NaBr, KCl, KBr, KI, RbCl, RbBr, CsCl and CsBr. Intermixing took place independent of the crystal structure. It became evident that the limit of mixing was governed by the ratio of ionic radii. If the ratio of ionic radii between the cation and/or anion was more than 68%, intermixing occurred. It was also found that the crystal structure formed by intermixing between NaCl-type and CsCl-type structures becomes the NaCl type. If four different elements of cations and anions are involved, two mixture phases grew. The key elements of mixing were the nearest ionic radii. (C) 2002 Elsevier Science B.V. All rights reserved.
• Crystallization and selective growth of amorphous Y-Ba-Cu-O film

  T. Tanigaki, S. Ariumi, H. Suzuki, Y. Kimura, S. Kimura, T. Sato, N. Tsuda, T. Nakada, Y. Saito, C. Kaito  Physics of Low-Dimensional Structures  11/12-  77  -84  2002  [Not refereed][Not invited]
  
• Ordered alloy formation by the use of reaction between ultrafine particle and cluster

  T Tsurusako, T Tanigaki, H Suzuki, Y Kimura, T Sato, O Kido, Y Saito, C Kaito  PHYSICS OF LOW-DIMENSIONAL STRUCTURES  7-8-  77  -86  2002  [Not refereed][Not invited]
   

  To observe the singularity of clusters and ultrafine particles in low dimensions, a new experiment has been started on the Au-Cu system. The diffusion of atoms in the cluster and ultrafine particles has been observed including the direct observation at the interface. The alloy formation temperature decreases by about 50degreesC compared with the film-ultrafine particle. The diffusion rate difference observed in bulk phase is preserved in the alloy formation process.
• A new-attempt on reduction of ultrafine oxide particles

  H Suzuki, T Tanigaki, T Sato, O Kido, Y Atou, Y Kimura, C Kaito  PHYSICS OF LOW-DIMENSIONAL STRUCTURES  7-8-  99  -105  2002  [Not refereed][Not invited]
   

  A method to coat the surface of ultrafine particles by an amorphous carbon layer was developed and a characteristic reduction of the ultrafine particles has been observed for WO3 ultrafine particles. The carbon layer formation and the reduction process have been observed in situ in a transmission electron microscope. The growth of the carbon layer predominately occurred upon heating at 200degreesC by using a heating stage. The characteristic graphitization of the carbon layer took place at about 400degreesC. The characteristic gap formation at the interface of the carbon layer and WO3 particles started at about 400degreesC. The reduction indicates that a, reaction between 0 and C atoms occurred and CO or CO2 gas evaporated into vacuum during the observation. The WO3, particles with the gap between carbon layers were also reduced.
• 放射光表面励起反応を用いた新素材創製の研究

  佐々木宗生, 花元克巳, 木村勇気, かい内千尋, 中山康之  滋賀県工業技術総合センター研究報告  (15)  46  -49  2001/08  [Not refereed][Not invited]
  
• Effect of SR irradiation on crystallization of amorphous tin oxide film

  Y Kimura, T Kobayashi, K Hanamoto, M Sasaki, S Kimura, T Nakada, Y Nakayama, C Kaito  NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT  467-  1221  -1224  2001/07  [Not refereed][Not invited]
   

  In order to see the effect of SR irradiation on crystal growth., crystallization of tin oxide films has been performed in vacuum under SR irradiation, A thin amorphous tin oxide film 50 nm thick was prepared on the carbon substrate by vacuum evaporation of SnO2 power, A SnO crystal appeared between 450-500 degreesC upon vacuum heating, with a preferred orientation of (0 0 1). By SR irradiation using a cylindrical mirror for 20 s, the SnO crystal appeared with the preferred orientation of (1 1 1). The crystal with the crystallographic shear structure was grown by SR irradiation. This growth under a SR beam is discussed in terms of SR beam excitation of lone-pair electrons seen in the SnO crystal structure. (C). 2001 Elsevier Science B.V. All rights reserved.
• Carbyne formation by synchrotron radiation

  C Kaito, Y Kimura, K Hanamoto, M Sasaki, S Kimura, T Nakada, Y Saito, C Koike, Y Nakayama  NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT  467-  1217  -1220  2001/07  [Not refereed][Not invited]
   

  Thin carbon films prepared by vacuum evaporation using the arc method were mounted on a standard electron microscope copper grid. They were irradiated by white synchrotron radiation (SR) beam by the use of cylindrical and toroidal mirrors. The irradiated film was examined using a high-resolution electron microscope alpha and alpha + beta mixture carbyne crystals were grown in round and the elongated shapes. The round crystals were composed of 5-10 nm crystallites of a carbyne form. The elongated crystal grew into a single crystal 100 nm in size. The c-axes of both grown crystals were oblique to the film. The growth of the carbynes was discussed as being the result of nucleation due to graphite microcrystallites formed by SR beam irradiation. (C) 2001 Elsevier Science B.V. All rights reserved.
• Effect of SR irradiation on In2O3 film

  K Hanamoto, A Hirai, M Sasaki, Y Kimura, K Miyatani, C Kaito, Y Nakayama  NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT  467-  1213  -1216  2001/07  [Not refereed][Not invited]
   

  The effect of SR irradiation on the crystal growth of indium oxide films prepared by electron-beam evaporation have been studied by X-ray diffraction and high-resolution electron microscopy. An as-deposited film showed In2O3 crystallites with a size of 2-10 nm. The crystallites were destroyed by SR irradiation under oxygen flow, SR irradiation without oxygen flow showed the growth of In2O3 crystallites up to 20 nm in size with accompanying deoxidation and indium-particle growth. The as-deposited film was composed of variously oriented particles. Periodic oxygen decomposition of the film preferentially took place on the (0 0 1)-oriented particle. (C) 2001 Elsevier Science B.V. All rights reserved.
• Photo-stimulated luminescence of Alkali-borate glasses containing halogen ions

  Ogawa A., Yamagishi Y., Kimura Y., Handa K., Harami T.  Meeting abstracts of the Physical Society of Japan  56-  (1)  853  -853  2001/03/09
• Crystallization of WO_3 thin film

  Kimura Yuki, Hanamoto Katsumi, Nakada Toshitaka, Nakayama Yasuyuki, Kaito Chihiro  Meeting abstracts of the Physical Society of Japan  56-  (1)  782  -782  2001/03/09
• Carbynes Formation by Synchrotron Radiation

  Kimura Y., Hanamoto K., Sasaki M., Kimura S., Nakada T., Saito Y., Koike C., Nakayama Y., Kaito C.  Meeting abstracts of the Physical Society of Japan  55-  (2)  745  -745  2000/09/10
• Topotactical growth of indium sulfide by evaporation of metal onto molybdenite

  C Kaito, A Ito, S Kimura, Y Kimura, Y Saito, T Nakada  JOURNAL OF CRYSTAL GROWTH  218-  (2-4)  259  -264  2000/09  [Not refereed][Not invited]
   

  The growth of In2S3 and InS by vacuum evaporation of indium metal on the surface of molybdenite has been observed in the initial stage of film growth. By the increment of In2S3 particle size, InS was also produced. By the increase of the film thickness to more than 20 nm, indium crystal predominately grew. The topotactic relations among the substrate and sulfide are as follows: (0 0 0 1)(MoS2) parallel to(1 1 0)(In2S3), [1 0 (1) over bar 0](MoS2) parallel to[1 1 1](In2S3) or (0 0 0 1)(MoS2) parallel to(1 1 0)(In2S3), [1 0 (1) over bar 0](MoS2) parallel to[1 0 0](In2S3). (C) 2000 Elsevier Science B.V. All rights reserved.
• Structure of II-VI semiconductor ultra-fine particles covered with SiO or carbon layer

  TANIGAKI Toshiaki, KIMURA Yuki, KIMURA Seiji, SAITO Yoshio, KAITO Chihiro  Journal of the Japanese Association of Crystal Growth  27-  (1)  171  -171  2000/07/01  

  ZnTe, CdTe, ZnSe and ZnS nanocrystals were prepared by simultaneously evaporation of II-VI compounds and carbon or SiO in Ar gas (80 torr). It has been found that zinc-blende particle covered with oxide or carbon layer has been produced predominantly.
• Crystallization of vacuum evaporated amorphous SnO_2 film

  KOBAYASHI Takahito, KIMURA Yuki, HANAMOTO Katsumi, NAKAYAMA Yasuyuki, KAITO Chihiro  Journal of the Japanese Association of Crystal Growth  27-  (1)  144  -144  2000/07/01  

  こばやし,たかひと / きむら,ゆき / はなもと,かつみ / なかやま,やすゆき / かいと,ちひろCrystallization process of amorphous tin oxide film have been studied by the heating in vacuum. The crystallization of SR irradiation was also observed. The difference of SR irradiation and the vacuum heating have been discussed on the grown crystal structure.
• Crystallization of WO_3 thin film

  KIMURA Yuki, HANAMOTO Katsumi, KAITO Chihiro  Journal of the Japanese Association of Crystal Growth  27-  (1)  143  -143  2000/07/01  

  Crystallization of thin amorphous film prepared by vacuum evaporation of WO_3 powder has been done by means of the SR white beam irradiation. The crystallization and crystal structure have been discussed with the results on electron beam irradiation and vacuum heating results.
• Characterization of indium tin oxide film and practical ITO film by electron microscopy

  T Nakao, T Nakada, Y Nakayama, K Miyatani, Y Kimura, Y Saito, C Kaito  THIN SOLID FILMS  370-  (1-2)  155  -162  2000/07  [Not refereed][Not invited]
   

  In order to clarify the structure of indium oxide him containing tin and tin oxides, various In2O3 based films prepared by vacuum evaporation were studied using high-resolution electron microscope (HREM). Indium tin oxide (ITO) film was composed of In2O3 and SnO. SnO crystal also contained (110) or (101) crystallographic shear (CS) structures that indicate excess amounts of tin. The CS structure was also found in a commercial ITO film having the resistivity of 2 x 10(-4) Omega cm. (C) 2000 Elsevier Science S.A. All rights reserved.
• Formation of carbide particles by the advanced gas evaporation method

  Kimura Yuki, Kimura Seiji, Nakada Toshitaka, Saito Yoshio, Kaito Chihiro  Meeting abstracts of the Physical Society of Japan  55-  (1)  766  -766  2000/03/10
• Structure of thin Cr film prepared by the vacuum evaporation method

  C. Kaito, H. Nakamura, S. Kimura, Y. Kimura, T. Nakada, Y. Saito  Thin Solid Films  359-  (2)  283  -287  2000/01/31  [Not refereed][Not invited]
   

  In order to clarify the structures of thin Cr films by their real space images, Cr films of various thicknesses, prepared using vacuum deposition, have been observed using a high resolution electron microscope. The amorphous chromium films were composed of microcrystallites of the order of 3 nm. The crystallite structure was δ-Cr. The well-known bcc chromium particles were observed in thick and large crystal particles. The stability of small particles is discussed.
• Spontaneous Alkali Halide Formation by the Use of KBr-KCl System

  Y. Kimura, Y. Saito, T. Nakada, C. Kaito  Physics of Low-Dimensional Structures  1/2-  L1-L7  2000  [Not refereed][Not invited]
  
• 24pZ-3 Formation of NaBr layer at the interface of KBr-NaCl system by Successive Evaporation

  Kimura Yuki, Kimura Seiji, Nakada Toshitaka, Saito Yoshio, Kaito Chihiro  Meeting abstracts of the Physical Society of Japan  54-  (2)  796  -796  1999/09/03
• Spontaneous Growth of Binary Alkali Halide Crystal by Successive Evaporation

  KIMURA Yuki, KIMURA Seiji, NAKADA Toshitaka, SAITO Yoshio, KAITO Chihiro  Journal of the Japanese Association of Crystal Growth  26-  (2)  35  -35  1999/07/01  

  It has been found that KBr-KCl binary alkali halide crystals can be produced at room temperature by successive evaporation of KCl and/or KBr on KBr and/or KCl particles in spite of large particles (200nm). The results on KCl-NaCl, NaCl-NaBr and KBr-NaCl have been shown.
• 30p-N-6 Spontaneous Growth of Binary Alkali Halide Crystal by Successive Evaporation

  Kimura Yuki, Kimura Seiji, Saito Yoshio, Kaito Chihiro, Nakada Toshitaka  Meeting abstracts of the Physical Society of Japan  54-  (1)  94  -94  1999/03/15
• On the spectral index of amorphous carbon grains in the mid infrared region

  KAITO Chihiro, KIMURA Seiji, SATO Kengo, KIMURA Yuki, OJIMA Yuki, HERRMANN Rudolf, KOIKE Chiyoe  Memoirs of the Research Institute of Science & Engineering, Ritumeikan University  58-  11  -21  1999
• Surface oxide on tin and indium ultrafine particles and their oxidation process

  C Kaito, T Nakao, Y Ato, Y Kimura, S Kimura, T Nakada, Y Saito  PHYSICS OF LOW-DIMENSIONAL STRUCTURES  12-  53  -60  1999  [Not refereed][Not invited]
   

  The structure of surface oxide on tin and indium metallic particles and their oxidation process at a temperature higher than the melting point of the particles have been elucidated on the basis of observations using a high-resolution electron microscope (HREM). In the case of tin particles, the surface oxide layer spontaneously produced by exposure to air was composed of microcrystallites with the size of 1 similar to 2 nm. In the case of indium, the (222) crystal of In2O3 covered the surface of indium particles. In the oxidation of tin at a temperature higher than its melting point, crystal shear structure which were present as the metal-excess Sn3O2 or Sn4O3 oxides have been found. In the case of indium particles, a definite crystallographic correlation, i.e., In2O3 (111) // In(110), has also been observed during the solidification of central metal. The fundamental behaviors of low-dimensional In and Sn particles can be observed.

Books etc

• Nanodust in the Solar System: Discoveries and Interpretations (Astrophysics and Space Science Library)

  Ingrid Mann, Nicole Meyer-Vernet, Andrzej Czechowski 
  Springer 2014/06 (ISBN: 3642436439) 222

  
• 1.シリーズ現代の天文学 第６巻「星間物質と星形成」

  日本評論社 2008

Presentations

• Formation experiments of cosmic dust analogues in microgravity environments  [Not invited]

  KIMURA Yuki

  33rd Grain Formation Workshop  2016/12
• 航空機を用いた微小重力実験  [Not invited]

  木村勇気, 斎藤史明, 佐藤陽亮, 中坪俊一, 石塚紳之介, 山﨑智也

  第22回 低温科学研究所 技術部 技術報告会  2016/12
• 鉄ニッケル合金基板を用いた FT 型触媒反応実験  [Not invited]

  KIMURA Yuki

  科研費新学術領域 分子進化 第12回ワークショップ  2016/10
• In-situ TEM Observation Reveals Early Stages of Crystallization Governed by Singular Phenomena of Nanoparticles  [Not invited]

  Yuki Kimura, Tomoya Yamazaki

  The 18th International Conference on Crystal Growth and Epitaxy  2016/08
• In-situ observation studies of nucleation and dissolution processes  [Not invited]

  KIMURA Yuki

  The 16th International Summer School on Crystal Growth  2016/08
• 雪の昇華過程のその場観察と水・氷の均質核生成実験に向けて  [Not invited]

  KIMURA Yuki

  低温物質の界面・ナノ現象ワークショップ2016  2016/07
• Advanced TEM studies give us new perspectives in water-mineral reactions  [Not invited]

  KIMURA Yuki

  International Workshop on Water-mineral Interactions  2016/07
• Elucidating the early stages of protein crystallization by TEM  [Not invited]

  KIMURA Yuki

  Goldschmidt 2016  2016/06
• Temperature dependence of reaction efficiency in the Fischer-Tropsh-type catalytic reaction on an iron substrate  [Not invited]

  KIMURA Yuki

  日本地球惑星科学連合2016年大会  2016/05
• Nucleation experiment of alumina and silica from vapor phase using the sounding rocket S-520-30  [Not invited]

  木村勇気, 石塚紳之介, 山﨑智也, 左近樹, 田中今日子, 竹内伸介, 稲富裕光

  日本地球惑星科学連合2016年大会  2016/05
• Nucleation of interstellar dust  [Invited]

  KIMURA Yuki

  International School of Crystallography for Space Sciences  2016/04
• 鉄基板を触媒としたFT 反応の温度依存性  [Not invited]

  KIMURA Yuki

  科研費新学術領域 分子進化 第７回ワークショップ  2016/03
• 透過電子顕微鏡を用いた溶液からの核生成の“その場”観察  [Not invited]

  KIMURA Yuki

  日本物理学会 第71回年次大会  2016/03
• Nucleation experiment to understand formation of cosmic dust  [Invited]

  KIMURA Yuki

  Astrophysical Ices in the Lab  2016/03
• 観測ロケットS-520-30号機を用いた宇宙ダストの再現実験  [Not invited]

  木村勇気, 石塚紳之介, 中坪俊一, 斎藤史明, 山﨑智也, 左近樹, 田中今日子, 竹内伸介, 稲富裕光

  第30回宇宙環境利用シンポジウム  2016/01
• Microgravity experiments using S-520 sounding rockets to elucidate formation process of cosmic dust  [Not invited]

  KIMURA Yuki

  第16回宇宙科学シンポジウム  2016/01
• 木村勇気、中坪 俊一、斎藤 史明、石塚 紳之介、山﨑 智也、稲富 裕光  [Not invited]

  木村勇気, 中坪 俊一, 斎藤 史明, 石塚 紳之介, 山﨑 智也, 稲富 裕光

  第21回 低温科学研究所 技術部 技術報告会  2015/12
• Nucleation experiments under microgravity condition  [Not invited]

  KIMURA Yuki

  32nd Grain Formation Workshop  2015/12
• Nucleation from a supersaturated vapor  [Not invited]

  Yuki Kimura, Kyoko K. Tanaka, Kouchi Akira, Naoki Watanabe, Shunichi Nakatsubo, Shinnosuke Ishizuka, Yuko Inatomi

  ILTS International Symposium on Low Temperature Science  2015/12
• In-situ observation of nucleation from solution phase  [Not invited]

  KIMURA Yuki

  Japan-Slovenia Bilateral Symposium of Transmission Electron Microscopy  2015/11
• Experimental results of sounding rocket S-520-30 and future plan  [Not invited]

  KIMURA Yuki

  大気球シンポジウム  2015/11
• ナノ粒子～小さな結晶の不思議な振る舞い～  [Invited]

  木村 勇気

  平成2７年度低温科学研究所公開講座  2015/11
• Homogeneous nucleation experiments reveal formation process of cosmic dust particles  [Invited]

  KIMURA Yuki

  第45回結晶成長国内会議  2015/10
• Nucleation and dissolution processes studied by in-situ observation using transmission electron microscopy  [Invited]

  KIMURA Yuki

  Department lecture of Jozef Stefan Institute  2015/10
• Nucleation processes studied by in-situ observation using transmission electron microscopes  [Invited]

  KIMURA Yuki

  International Discussion Meeting on Crystal Growth (39th Toronkai)  2015/09
• Assembling interferometers and in-situ observation of ambient phases and solid-liquid interfaces  [Invited]

  KIMURA Yuki

  International Discussion Meeting on Crystal Growth (39th Toronkai)  2015/09
• Gravity Effects on the Formation of Ultrafine Particles by the Gas Evaporation Method  [Not invited]

  KIMURA Yuki

  The Joint Conference of 6th International Symposium on Physical Science in Space (ISPS-6) and 10th International Conference on Two-Phase Systems for Space and Ground Applications (ITTW2015)  2015/09
• Electron Holography Unveiled Formation Process of Extraterrestrial Magnetite  [Invited]

  Yuki Kimura, Kazuo Yamamoto, Takeshi Sato

  Microscopy & Microanalysis  2015/08
• Direct Liquid In Situ TEM Obseration of a Libing Protein Crystal  [Invited]

  KIMURA Yuki

  Microscopy & Microanalysis  2015/08
• Nucleation governing mineral evolution in space  [Invited]

  KIMURA Yuki

  Space Science Colloquium  2015/07
• ナノ粒子の生成過程と溶解過程  [Invited]

  木村 勇気

  低温研セミナー  2015/06
• Reproduction experiment of molecular formation based on Fischer-Tropsh-type catalytic reaction in the early solar nebula  [Not invited]

  KIMURA Yuki, YAMAZAKI Tomoya, TSUCHIYAMA Akira, NAGAHARA Hiroko, HAMA Tetsuya, HIDAKA Hiroshi, WATANABE Naoki, KOUCHI Akira

  JPGU meeting 2015  2015/05
• TEM observation of dissolution process of sodium chlorate nanocrystals  [Not invited]

  KIMURA Yuki, YAMAZAKI Tomoya, SATO Hisao

  JPGU meeting 2015  2015/05
• 新星周囲でのダスト形成過程の理解  [Not invited]

  左近樹, 酒向重行, 大澤亮, 中村友彦, 下西隆, 宮田隆志, 高橋英則, 島本早也佳, 尾中敬, 野沢貴也, 木村勇気, 小笹隆司, 藤吉拓哉, 植村誠, 新井彰

  日本天文学会年会講演予稿集  2014/02
• 酸素に富むAGB星周における高温凝縮ダスト形成過程解明への赤外分光スペクトルその場計測実験  [Not invited]

  石塚紳之介, 木村勇気, 中村智樹

  日本天文学会年会講演予稿集  2013/08
• 観測ロケットS‐520‐28号機を用いた微小重力実験  [Not invited]

  稲富裕光, 木村勇気, 塚本勝男, 竹内伸介, 石井信明

  応用物理学会春季学術講演会講演予稿集(CD-ROM)  2013/03
• NaClO₃溶液成長におけるアキラルな準安定相の溶解度測定  [Not invited]

  新家寛正, 原田俊太, 宇治原徹, 三浦均, 木村勇気, 上羽牧夫, 塚本勝男

  結晶成長国内会議予稿集(CD-ROM)  2013
• 結晶成長過程の解明に向けた三次元干渉計の開発と応用  [Not invited]

  村山健太, 塚本勝男, 木村勇気

  結晶成長国内会議予稿集(CD-ROM)  2013
• 観測ロケット“S‐520‐28号機”を用いた微小重力実験から探る鉄微粒子の生成過程  [Not invited]

  木村勇気, 田中今日子, 塚本勝男, 竹内伸介, 稲富裕光

  日本惑星科学会秋季講演会予稿集  2013
• NaClO₃溶液成長におけるアキラルな準安定相を介したキラル結晶形成過程  [Not invited]

  新家寛正, 原田俊太, 宇治原徹, 三浦均, 木村勇気, 栗林貴弘, 上羽牧夫, 塚本勝男

  結晶成長国内会議予稿集(CD-ROM)  2013
• 観測ロケットS‐520‐28号機を用いた微小重力環境での鉄の均質核生成実験  [Not invited]

  木村勇気, 田中今日子, 竹内伸介, 塚本勝男, 三浦均, 稲富裕光

  結晶成長国内会議予稿集(CD-ROM)  2013
• 観測ロケットS-520-28号機を用いた微小重力環境における鉄蒸気からの均質核生成実験  [Not invited]

  日本地球惑星科学連合2013年大会  2013
• Nucleation and growth take into account physical properties of nanoparticles  [Not invited]

  The 2013 Collaborative Conference on Crystal Growth (3CG)  2013
• Nucleation experiments of iron dust under microgravity  [Not invited]

  Cosmic Dust VI  2013
• Nucleation experiment in vapor phase under microgravity using the sounding rocket S-520-28  [Not invited]

  17th International Conference on Crystal Growth and Epitaxy  2013
• Nucleation and growth of cosmic nanominerals based on size effects in mesoscale  [Not invited]

  17th International Conference on Crystal Growth and Epitaxy  2013
• Microgravity experiment using the sounding rocket S-520-28 for understanding a formation process of cosmic dust  [Not invited]

  3rd International Conference on Crystallogenesis and Mineralogy  2013
• 観測ロケットS-520-28号機を用いた微小重力環境における鉄蒸気からの均質核生成実験  [Not invited]

  日本地球惑星科学連合2013年大会  2013
• Nucleation and growth take into account physical properties of nanoparticles  [Not invited]

  The 2013 Collaborative Conference on Crystal Growth (3CG)  2013
• Nucleation experiments of iron dust under microgravity  [Not invited]

  Cosmic Dust VI  2013
• Nucleation experiment in vapor phase under microgravity using the sounding rocket S-520-28  [Not invited]

  17th International Conference on Crystal Growth and Epitaxy  2013
• Nucleation and growth of cosmic nanominerals based on size effects in mesoscale  [Not invited]

  17th International Conference on Crystal Growth and Epitaxy  2013
• Microgravity experiment using the sounding rocket S-520-28 for understanding a formation process of cosmic dust  [Not invited]

  3rd International Conference on Crystallogenesis and Mineralogy  2013
• 赤外線継続観測に基づく新星V1280Sco周囲でのダスト形成史(2)  [Not invited]

  左近樹, 酒向重行, 大澤亮, 中村友彦, 下西隆, 宮田隆志, 高橋英則, 尾中敬, 野沢貴也, 木村勇気, 小笹隆司, 藤吉拓哉, 植村誠, 新井彰

  日本天文学会年会講演予稿集  2012/08
• メゾスコピック領域の物性を考慮した宇宙ダストの結晶成長  [Not invited]

  木村勇気

  日本物理学会講演概要集  2012/03
• S‐520観測ロケットを用いた宇宙ダストの核生成実験にむけて:WG初年度活動報告  [Not invited]

  木村勇気, 稲富裕光, 三浦均, 田中今日子, 左近樹, 野沢貴也, 中村智樹, 塚本勝男

  宇宙利用シンポジウム  2012/03
• 赤外線継続観測に基づく新星V1280Sco周囲でのダスト形成史  [Not invited]

  左近樹, 酒向重行, 大澤亮, 下西隆, 宮田隆志, 高橋英則, 尾中敬, 野沢貴也, 木村勇気, 小笹隆司, 藤吉拓哉, 植村誠, 新井彰

  日本天文学会年会講演予稿集  2012/02
• 微小重力環境利用に向けた宇宙ダスト生成の“その場”観察実験  [Not invited]

  木村勇気, 稲富裕光, 田中今日子, 真木孝雄, 三浦均, 左近樹, 野沢貴也, 塚本勝男

  日本結晶成長学会誌  2012
• バテライト形成過程における結晶質の前駆体  [Not invited]

  杉浦悠紀, 小沼一雄, 木村勇気, 門馬綱一, 塚本勝男, 山崎淳司

  結晶成長国内会議予稿集(CD-ROM)  2012
• 針状アラゴナイト結晶の成長メカニズム  [Not invited]

  小隅誠司, 塚本勝男, 木村勇気, 三浦均

  結晶成長国内会議予稿集(CD-ROM)  2012
• 炭酸水中におけるCa(OH)₂/CaCO₃のdissolution/precipitation反応の“その場”観察  [Not invited]

  大島嘉文, 三浦均, 木村勇気, 佐藤久夫, 塚本勝男

  結晶成長国内会議予稿集(CD-ROM)  2012
• メゾスコピック領域の物性を考慮した宇宙ダストの結晶成長  [Not invited]

  日本物理学会2012年春季大会  2012
• 宇宙ダストを模擬した核生成の“その場”観察実験  [Not invited]

  文部科学省 先端研究施設共用イノベーション創出事業ナノテクノロジー・ネットワーク 中部地区ナノテク総合支援：ナノ材料創製加工と先端機器分析 平成23年度成果報告会  2012
• Formation process of colloidal magnetite in the Tagish Lake meteorite  [Not invited]

  Workshop on Minerals-Water-Organics in the Early Solar System  2012
• 航空機による微小重力環境を利用した核生成の“その場”観察実験  [Not invited]

  日本地球惑星科学連合2012年大会  2012
• 溶液成長における核生成と溶解過程のＴＥＭ中“その場”観察  [Not invited]

  日本地球惑星科学連合2012年大会  2012
• Simultaneous determination of sticking probability and surface free energy by the homogeneous nucleation experiment  [Not invited]

  3rd Workshop of Nucleation Related to Cosmic Dust & its contribution to the organic formation in 4.6 billion years ago  2012
• Simultaneous determination of surface free energy and sticking probability based on formation experiment of cosmic dust and nucleation theories  [Not invited]

  The 5th meeting on Cosmic Dust  2012
• 宇宙における微粒子生成  [Not invited]

  平成24年度東北大通研共同プロジェクト研究会プログラム、微粒子プラズマの応用に関する基礎研究  2012
• ダスト生成に重要な吸着係数と表面自由エネルギーの同時決定  [Not invited]

  日本惑星科学会 2012年秋季講演会  2012
• In-situ observation of nucleation and growth environment of cosmic dust analogues using an interferogram in laboratory  [Not invited]

  Achievements of G-COE Program for Earth and Planetary Dynamics and the Future Perspectives  2012
• Dual-wavelength interferometric observation of homogeneous nucleation from supercooled vapor under 1G and μG  [Not invited]

  9th China-Japan-Korea Workshop on Microgravity Sciences, Asian Microgravity Pre-Symposium  2012
• メゾスコピック領域の物性を考慮した宇宙ダストの結晶成長  [Not invited]

  日本物理学会2012年春季大会  2012
• 宇宙ダストを模擬した核生成の“その場”観察実験  [Not invited]

  文部科学省 先端研究施設共用イノベーション創出事業ナノテクノロジー・ネットワーク 中部地区ナノテク総合支援：ナノ材料創製加工と先端機器分析 平成23年度成果報告会  2012
• Formation process of colloidal magnetite in the Tagish Lake meteorite  [Not invited]

  Workshop on Minerals-Water-Organics in the Early Solar System  2012
• 航空機による微小重力環境を利用した核生成の“その場”観察実験  [Not invited]

  日本地球惑星科学連合2012年大会  2012
• 溶液成長における核生成と溶解過程のＴＥＭ中“その場”観察  [Not invited]

  日本地球惑星科学連合2012年大会  2012
• Simultaneous determination of sticking probability and surface free energy by the homogeneous nucleation experiment  [Not invited]

  3rd Workshop of Nucleation Related to Cosmic Dust & its contribution to the organic formation in 4.6 billion years ago  2012
• Simultaneous determination of surface free energy and sticking probability based on formation experiment of cosmic dust and nucleation theories  [Not invited]

  The 5th meeting on Cosmic Dust  2012
• 宇宙における微粒子生成  [Not invited]

  平成24年度東北大通研共同プロジェクト研究会プログラム、微粒子プラズマの応用に関する基礎研究  2012
• ダスト生成に重要な吸着係数と表面自由エネルギーの同時決定  [Not invited]

  日本惑星科学会 2012年秋季講演会  2012
• In-situ observation of nucleation and growth environment of cosmic dust analogues using an interferogram in laboratory  [Not invited]

  Achievements of G-COE Program for Earth and Planetary Dynamics and the Future Perspectives  2012
• Dual-wavelength interferometric observation of homogeneous nucleation from supercooled vapor under 1G and μG  [Not invited]

  9th China-Japan-Korea Workshop on Microgravity Sciences, Asian Microgravity Pre-Symposium  2012
• 二波長干渉計による気相からの均質核生成のその場観察実験  [Not invited]

  木村勇気, 田中今日子, 三浦均, 稲富裕光, 塚本勝男

  日本物理学会講演概要集  2011/08
• 光ピンセットを利用したコロイド結晶の核形成制御  [Not invited]

  仙波稔己, 三浦均, 木村勇気, 塚本勝男

  コロイドおよび界面化学討論会講演要旨集  2011/08
• 低温氷表面に吸着した水素原子の拡散メカニズム  [Not invited]

  羽馬哲也, 渡部直樹, 香内晃, 木村勇気, PIRRONELLO V

  日本物理学会講演概要集  2011/03
• 宇宙ダスト生成過程の解明に向けた気相からの均質核形成のその場観察実験  [Not invited]

  木村勇気, 田中今日子, 三浦均, 塚本勝男, 稲富裕光

  宇宙利用シンポジウム  2011/03
• JEM内での溶液からの結晶成長“その場”観察用セル  [Not invited]

  山崎智也, 三浦均, 木村勇気, 吉崎泉, 福山誠二郎, 真木孝雄, 塚本勝男

  結晶成長国内会議予稿集(CD-ROM)  2011
• 金平糖の角(つの)の数  [Not invited]

  塚本勝男, 三浦均, 木村勇気, 伊藤正憲, 佐藤久夫

  結晶成長国内会議予稿集(CD-ROM)  2011
• 二酸化炭素固定化に向けた水酸化カルシウム結晶の面溶解・成長速度測定  [Not invited]

  大島嘉文, 三浦均, 木村勇気, 佐藤久夫, 塚本勝男

  結晶成長国内会議予稿集(CD-ROM)  2011
• 光ピンセットを利用した二次元コロイド結晶の核形成制御  [Not invited]

  仙波稔己, 三浦均, 木村勇気, 石川正道, 塚本勝男

  結晶成長国内会議予稿集(CD-ROM)  2011
• TEMを用いた液中“その場”観察:塩素酸ナトリウムの核生成  [Not invited]

  木村勇気, 新家寛正, 三浦均, 塚本勝男

  結晶成長国内会議予稿集(CD-ROM)  2011
• リン酸第8カルシウム(OCP)モルフォロジー形成時における中間相の役割  [Not invited]

  杉浦悠紀, 小沼一雄, 木村勇気, 三浦均, 塚本勝男

  結晶成長国内会議予稿集(CD-ROM)  2011
• 隕石中のマグネタイトコロイド結晶  [Not invited]

  野澤純, 塚本勝男, 木村勇気, 三浦均

  結晶成長国内会議予稿集(CD-ROM)  2011
• アラゴナイト形成過程原子分解能その場観察  [Not invited]

  荒木優希, 木村勇気, 塚本勝男, 高木良介, 宮下知幸, 大藪範昭, 小林圭, 山田啓文

  結晶成長国内会議予稿集(CD-ROM)  2011
• 超高過飽和ガスから生成するダスト類似物の均質核形成と接合成長  [Not invited]

  日本地球惑星科学連合2011年大会  2011
• 高速“その場”観察による気相中でのパルス的均質核形成プロセス  [Not invited]

  日本地球惑星科学連合2011年大会  2011
• Separate process of nucleation, coalescence and growth in vapor phase  [Not invited]

  International conference on materials for advanced teqhunologies (ICMAT) Symposium DD: CGCT-5-Fundamentals of Crystallization and Low Dimensional Crystalization  2011
• Condensation of Cosmic Dust far from equilibrium condition  [Not invited]

  Asia Oceania Geosciences Society 8th Annual Meeting  2011
• Agreement of experiment and theory in homogeneous nucleation  [Not invited]

  74th Annual Meeting of the Meteoritical Society  2011
• Double Wavelength Interferometry for Direct Observation of Homogeneous Nucleation in Vapor Phase  [Not invited]

  XXII Congress and General Assembly International Union of Crystallography (IUCr2011)  2011
• 二波長干渉計による気相からの均質核生成のその場観察実験  [Not invited]

  日本物理学会2011年秋季大会  2011
• Homogeneous nucleation and growth of nanoparticles in vapor phase  [Not invited]

  BIT’s 1st Annual World Congress of Nano-Science & Technology  2011
• TEMを用いた液中“その場”観察：塩素酸ナトリウムの核生成  [Not invited]

  第41回結晶成長国内会議  2011
• Interferometric Direct Observation of Nanocrystal Formation via Homogeneous Nucleation in Vapor Phase  [Not invited]

  The 20th Nisshin Engineering Particle Technology International Seminar (NEPTIS-20), Modeling of Nucleation and Growth on Crystallization Processes  2011
• 超高過飽和ガスから生成するダスト類似物の均質核形成と接合成長  [Not invited]

  日本地球惑星科学連合2011年大会  2011
• 高速“その場”観察による気相中でのパルス的均質核形成プロセス  [Not invited]

  日本地球惑星科学連合2011年大会  2011
• Separate process of nucleation, coalescence and growth in vapor phase  [Not invited]

  International conference on materials for advanced teqhunologies (ICMAT) Symposium DD: CGCT-5-Fundamentals of Crystallization and Low Dimensional Crystalization  2011
• Condensation of Cosmic Dust far from equilibrium condition  [Not invited]

  Asia Oceania Geosciences Society 8th Annual Meeting  2011
• Agreement of experiment and theory in homogeneous nucleation  [Not invited]

  74th Annual Meeting of the Meteoritical Society  2011
• Double Wavelength Interferometry for Direct Observation of Homogeneous Nucleation in Vapor Phase  [Not invited]

  XXII Congress and General Assembly International Union of Crystallography (IUCr2011)  2011
• 二波長干渉計による気相からの均質核生成のその場観察実験  [Not invited]

  日本物理学会2011年秋季大会  2011
• Homogeneous nucleation and growth of nanoparticles in vapor phase  [Not invited]

  BIT’s 1st Annual World Congress of Nano-Science & Technology  2011
• TEMを用いた液中“その場”観察：塩素酸ナトリウムの核生成  [Not invited]

  第41回結晶成長国内会議  2011
• Interferometric Direct Observation of Nanocrystal Formation via Homogeneous Nucleation in Vapor Phase  [Not invited]

  The 20th Nisshin Engineering Particle Technology International Seminar (NEPTIS-20), Modeling of Nucleation and Growth on Crystallization Processes  2011
• Calcite(100)面におけるOCPエピタキシャル成長  [Not invited]

  杉浦悠紀, 木村勇気, 三浦均, 小沼一雄, 塚本勝男

  無機リン化学討論会講演予稿集  2010/10
• ナノ粒子に現れる準安定相  [Not invited]

  木村勇気, 塚本勝男

  日本物理学会講演概要集  2010/08
• 水素原子のアモルファス氷表面拡散と水素分子生成  [Not invited]

  HAMA Tetsuya, KIMURA Yuki, KOUCHI Akira, WATABE Naoki

  原子衝突研究協会年会講演概要集  2010/08
• A terminal of PAH evolution  [Not invited]

  215th Meeting of the American Astronomical Society  2010
• Synthesis of organic hollow globules based on singular phenomena of nanoparticles  [Not invited]

  The 41th Lunar and Planetary Science Conference  2010
• 干渉法を用いたナノ粒子凝縮過程の観察  [Not invited]

  日本地球惑星科学連合2010年大会  2010
• プラズマを用いた宇宙固体微粒子の再現実験  [Not invited]

  日本地球惑星科学連合2010年大会  2010
• Silicate Condensation Experiments in a Hydrogen Dominant Gas and Its Thermal History  [Not invited]

  73rd Annual Meeting of the Meteoritical Society  2010
• Condensation Takes Place in Far from Equilibrium Condition  [Not invited]

  73rd Annual Meeting of the Meteoritical Society  2010
• Experimental demonstration of a forsterite cycle from evolved stars to the solar system  [Not invited]

  The 20th General Meeting of the International Mineralogical Association  2010
• In-situ observation by interferometer during condensation of smoke particles  [Not invited]

  The 20th General Meeting of the International Mineralogical Association  2010
• A terminal of PAH evolution  [Not invited]

  215th Meeting of the American Astronomical Society  2010
• Synthesis of organic hollow globules based on singular phenomena of nanoparticles  [Not invited]

  The 41th Lunar and Planetary Science Conference  2010
• 干渉法を用いたナノ粒子凝縮過程の観察  [Not invited]

  日本地球惑星科学連合2010年大会  2010
• プラズマを用いた宇宙固体微粒子の再現実験  [Not invited]

  日本地球惑星科学連合2010年大会  2010
• Silicate Condensation Experiments in a Hydrogen Dominant Gas and Its Thermal History  [Not invited]

  73rd Annual Meeting of the Meteoritical Society  2010
• Condensation Takes Place in Far from Equilibrium Condition  [Not invited]

  73rd Annual Meeting of the Meteoritical Society  2010
• Experimental demonstration of a forsterite cycle from evolved stars to the solar system  [Not invited]

  The 20th General Meeting of the International Mineralogical Association  2010
• In-situ observation by interferometer during condensation of smoke particles  [Not invited]

  The 20th General Meeting of the International Mineralogical Association  2010
• 晩期星周囲でPAHから作られる炭素質粒子  [Not invited]

  齊藤碧, 木村勇気

  日本天文学会年会講演予稿集  2009/08
• 実験から導かれたシリケイト微粒子の新しい生成過程  [Not invited]

  木村勇気, NUTH Joseph A.,III

  日本天文学会年会講演予稿集  2009/08
• 低温アモルファス氷表面における水素原子の拡散・脱離  [Not invited]

  渡部直樹, 香内晃, 木村勇気

  日本物理学会講演概要集  2009/08
• 隕石中のマグネタイトのコロイド結晶  [Not invited]

  野澤純, 塚本勝男, 木村勇気, 甲野藤真

  日本物理学会講演概要集  2009/08
• Colloidal crystallization of magnetite particles in the meteorite  [Not invited]

  NOZAWA JUN, TSUKAMOTO KATSUO, KONOTO MAKOTO, KIMURA YUKI

  結晶成長国内会議予稿集  2009
• Origin of forsterite cosmic dust particles based on vapor phase condensation experiment  [Not invited]

  KIMURA YUKI, NUTH JOSEPH A.,III

  結晶成長国内会議予稿集  2009
• 水素原子の表面拡散は速いか？：CO固体表面の場合  [Not invited]

  日本地球惑星科学連合2009年大会  2009
• Crystallization of silicate nanoparticles at lower temperature  [Not invited]

  International School of Crystallization  2009
• Formation of Magnesium Silicates is Limited around Evolved Stars  [Not invited]

  The 214th Meeting of the American Astronomical Society  2009
• 実験から導かれたシリケイト微粒子の新しい生成過程  [Not invited]

  日本天文学会2009年秋季年会  2009
• ケイ酸塩ダストの新しい生成シナリオ  [Not invited]

  日本惑星科学会2009年秋季講演会  2009
• 晩期星における珪酸塩ダスト生成の再現実験  [Not invited]

  第27回Grain Formation Workshop / 平成21年度銀河のダスト研究会  2009
• 気相実験が示す“かんらん石”宇宙ダスト粒子の起源  [Not invited]

  第39回結晶成長国内会議  2009
• 水素原子の表面拡散は速いか？：CO固体表面の場合  [Not invited]

  日本地球惑星科学連合2009年大会  2009
• Crystallization of silicate nanoparticles at lower temperature  [Not invited]

  International School of Crystallization  2009
• Formation of Magnesium Silicates is Limited around Evolved Stars  [Not invited]

  The 214th Meeting of the American Astronomical Society  2009
• 実験から導かれたシリケイト微粒子の新しい生成過程  [Not invited]

  日本天文学会2009年秋季年会  2009
• ケイ酸塩ダストの新しい生成シナリオ  [Not invited]

  日本惑星科学会2009年秋季講演会  2009
• 晩期星における珪酸塩ダスト生成の再現実験  [Not invited]

  第27回Grain Formation Workshop / 平成21年度銀河のダスト研究会  2009
• 気相実験が示す“かんらん石”宇宙ダスト粒子の起源  [Not invited]

  第39回結晶成長国内会議  2009
• 晩期星に見られる結晶質シリケイトの生成過程に対する再現実験  [Not invited]

  木村勇気, 宮下徹平, 熊本明仁, 齊藤碧, 墻内千尋

  日本天文学会年会講演予稿集  2008/02
• 原始太陽系星雲中での物質進化に関わるダストの振る舞い  [Not invited]

  木村勇気

  日本惑星科学会秋季講演会予稿集  2007
• Structure of ZrO2 nanoparticles produced by the advanced gas evaporation method  [Not invited]

  YANAGA HIDEOMI, KUMAMOTO AKIHITO, KIMURA YUKI, KAITO CHIHIRO

  結晶成長国内会議予稿集  2007
• PAHクラスターの成長に及ぼすプラズマ効果  [Not invited]

  齊藤碧, 木村勇気, 墻内千尋

  日本惑星科学会秋季講演会予稿集  2007
• Stricture of thin iron-nickel film produced simultaneous evaporation of iron and nickel and formation condition of tetrataenite phase  [Not invited]

  YAMASHITA TEPPEI, KIMURA YUKI, KIDO OSAMU, KUMAMOTO AKIHITO, KAITO CHIHIRO

  結晶成長国内会議予稿集  2007
• Structural alteration of Magnesium particles in a nitrogen plasma  [Not invited]

  NIINA KENJI, KUMAMOTO AKIHITO, KIMURA YUKI, KAITO CHIHIRO

  結晶成長国内会議予稿集  2007
• In-situ Observation for formation Process of Al Vacancy Clusters  [Not invited]

  KUMAMOTO AKIHITO, KIMURA YUKI, KAITO CHIHIRO, SAITO YOSHIO

  結晶成長国内会議予稿集  2007
• Effects of oxygen gas during a formation of CaS grains in early solar nebula  [Not invited]

  YOKOYAMA KAORI, YAMASHITA TEPPEI, KUMAMOTO AKIHITO, KIMURA YUKI, KOIKE CHIYOE, KAITO CHIHIRO

  結晶成長国内会議予稿集  2007
• Electric field effect on the growth of metallic and polar crystal particles  [Not invited]

  ADACHI SHUNSUKE, KUMAMOTO AKIHITO, SHINTAKU MASAYUKI, KIMURA YUKI, KINUTA YASUHIKO, KAITO CHIHIRO

  日本結晶成長学会誌  2006/11
• Growth of TiO and TiO2 Smoke Particles from TiC Smoke  [Not invited]

  KUMAMOTO AKIHITO, SHINTAKU MASAYUKI, KURUMADA MAMI, KIDO OSAMU, KIMURA YUKI, KAITO CHIHIRO

  日本結晶成長学会誌  2006/11
• Silicate Grain Formation with Non-Mass Dependent Oxygen Isotopic Fractionation  [Not invited]

  KIMURA YUKI, NUTH JOSEPH A, III, CHAKRABORTY SUBRATA, THIEMENS MARK H

  日本結晶成長学会誌  2006/11
• 異なる環境下でのシリケイトグレインの合成実験と赤外スペクトル  [Not invited]

  木村勇気, NUTH Joseph A.,III

  日本天文学会年会講演予稿集  2006/08
• 質量に依存しない酸素同位体分別を示す難揮発性微粒子の生成実験  [Not invited]

  木村勇気, NUTH Joseph, A. III, CHAKRABORTY Subrata, THIEMENS Mark H

  日本惑星科学会秋季講演会予稿集  2006
• マグネシウムシリケイトダストの結晶化  [Not invited]

  宮崎悠, 木村勇気, 新宅正行, 車田真実, 熊本明仁, 墻内千尋

  日本惑星科学会秋季講演会予稿集  2006
• カーボン‐シリコン系からのナノダイヤモンドの生成  [Not invited]

  木村勇気, 佐藤岳志, 墻内千尋

  日本天文学会年会講演予稿集  2004
• C‐Si混合膜からのナノダイヤモンドの成長  [Not invited]

  木村勇気, かき内千尋

  日本惑星科学会秋季講演会予稿集  2003/10
• TiCナノ微結晶と赤外線吸収スペクトルとの相関  [Not invited]

  木村勇気, 池上亜紀美, 鈴木仁志, かき内千尋

  日本惑星科学会秋季講演会予稿集  2003/10
• 216.5‐224.5nm減光ピークを示す煤の選択生成,及びピーク位置とグラファイト構造との関係  [Not invited]

  木村勇気, 佐藤岳志, かき内千尋

  日本惑星科学会秋季講演会予稿集  2003/10
• プラズマ中でのカーボングレインの挙動  [Not invited]

  佐藤岳志, 上辻勝也, 木村勇気, 鈴木仁志, 谷垣俊明, 城戸修, 車田真実, かい内千尋, 塚本勝男

  日本岩石鉱物鉱床学会学術講演会講演要旨集  2003/09
• 非晶質シリケイトの高温での挙動の直接観察  [Not invited]

  上辻勝也, かい内千尋, 木村勇気, 鈴木仁志, 佐藤岳志, 谷垣俊明, 城戸修, 車田真実, 塚本勝男

  日本岩石鉱物鉱床学会学術講演会講演要旨集  2003/09
• Structure of Copper Oxide Ultrafine Particles Produced in an Electric Field  [Not invited]

  SUZUKI HITOSHI, SATO TAKESHI, KIMURA YUKI, SAITO YOSHIO, KAITO CHIHIRO

  日本結晶成長学会誌  2003/07
• Phase transition temperature from Al-Cr quasicrystal to stable crystal phase on nano-particle by direct observation  [Not invited]

  KIDO OSAMU, SASAKI SHIN'ICHI, KURUMADA MAMI, SUZUKI HITOSHI, KIMURA YUKI, SAITO YOSHIO, KAITO CHIHIRO

  日本結晶成長学会誌  2003/07
• Production of TiC nanocrystallites and corre1ation between its size and infrared spectra  [Not invited]

  IKEGAMI AKIMI, KIMURA YUKI, SUZUKI HITOSHI, SAITO YOSHIO, KAITO CHIHIRO

  日本結晶成長学会誌  2003/07
• Crystallization of carbon film containing metal atoms by vacuum heating  [Not invited]

  KIMURA YUKI, TANIGAKI TOSHIAKI, SUZUKI HITOSHI, SATO TAKESHI, KAITO CHIHIRO

  日本結晶成長学会誌  2003/07
• Forsterite particle formation by coalescence growth of MgO and SiO2 smoke particles  [Not invited]

  KAMITSUJI KATSUYA, SUZUKI HITOSHI, KIMURA YUKI, SAITO YOSHIO, KAITO CHIHIRO

  日本結晶成長学会誌  2003/07
• Dynamics of Al clusters on SiO2 nanoparticles by in situ observation  [Not invited]

  SASAKI SHIN'ICHI, KIMURA YUKI, SAITO YOSHIO, TAKEDA ATSUSHI, KAITO CHIHIRO

  日本結晶成長学会誌  2003/07
• Properties and structure studies of R-phase on NiTi shape memory alloy nanoparticle  [Not invited]

  KURUMADA MAMI, KIMURA YUKI, SUZUKI HITOSHI, KIDO OSAMU, SAITO YOSHIO, KAITO CHIHIRO

  日本結晶成長学会誌  2003/07
• 星間雲での光化学反応によるプレソーラーダイヤモンドの生成  [Not invited]

  香内晃, 木村勇気, かい内千尋

  日本惑星科学会秋季講演会予稿集  2002/10
• モデル星間有機物の水質・熱変成実験  [Not invited]

  中野英之, 香内晃, 荒川政彦, 木村勇気, かい内千尋, 大野浩, 本堂武夫

  日本惑星科学会秋季講演会予稿集  2002/10
• ガス中同時蒸発によるSi‐Ti‐C微粒子の作製と赤外スペクトル  [Not invited]

  木村勇気, かい内千尋

  日本惑星科学会秋季講演会予稿集  2002/10
• 微粒子創製に及ぼすプラズマ効果  [Not invited]

  佐藤岳志, 斎藤嘉夫, 木村勇気, 鈴木仁志, かい内千尋

  日本惑星科学会秋季講演会予稿集  2002/10
• Iron silicate formation by coalescence growth of Fe and SiO particles.  [Not invited]

  KAMITSUJI KATSUYA, SAITO YOSHIO, SUZUKI HITOSHI, KIMURA YUKI, KAITO CHIHIRO

  日本結晶成長学会誌  2002/07
• Mechanism of spontaneous copper selenide formation.  [Not invited]

  ISHIKAWA YOSUKE, KIMURA YUKI, SUZUKI HITOSHI, SAITO YOSHIO, KAITO CHIHIRO

  日本結晶成長学会誌  2002/07
• Production of presolar grains by the gas evaporation method.  [Not invited]

  KIMURA YUKI, KAITO CHIHIRO

  日本結晶成長学会誌  2002/07
• The structure and growth mechanism of rod shaped Mn ultrafine particles.  [Not invited]

  KIDO OSAMU, SHINTAKU MASAYUKI, KIMURA JUN, KIMURA YUKI, SUZUKI HITOSHI, SAITO YOSHIO, KAITO CHIHIRO

  日本結晶成長学会誌  2002/07
• Production of carbon grains by RF plasma.  [Not invited]

  SATO TAKASHI, SAITO YOSHIO, KIMURA YUKI, SUZUKI HITOSHI, KAITO CHIHIRO

  日本結晶成長学会誌  2002/07
• In-situ observation of Silicon Carbide formation process by ACCM.  [Not invited]

  ISHIKAWA MANABU, KIMURA YUKI, SUZUKI HITOSHI, SAITO YOSHIO, KAITO CHIHIRO

  日本結晶成長学会誌  2002/07
• Structure and formation of Ge cluster produced by Ge-C co-evaporation.  [Not invited]

  TANAKA SHUJI, KIMURA YUKI, SUZUKI HITOSHI, SAITO YOSHIO, KAITO CHIHIRO

  日本結晶成長学会誌  2002/07
• Infrared spectra of TiC, SiC and (Si,Ti)-C grains  [Not invited]

  KIMURA YUKI, KAITO CHIHIRO

  日本天文学会年会講演予稿集  2002
• シリコン‐カーボン系における構造とスペクトルの相関  [Not invited]

  木村勇気, 中尾智子, 上野洋, 斎藤嘉夫, かき内千尋

  日本惑星科学会秋季講演会予稿集  2001/10
• ITO透明導電膜への放射光照射効果  [Not invited]

  佐々木宗生, 花元克巳, 木村勇気, 三木秀二郎, 墻内千尋, 中山康之

  応用物理学関係連合講演会講演予稿集  2001/03
• 放射光照射による非晶質カーボン膜からのカルビン結晶の生成  [Not invited]

  木村勇気, 花本克巳, 佐々木宗生, 木村誠二, 中田俊隆, 斎藤嘉夫, 小池千代枝, 中山康之, しょう内千尋

  日本惑星科学会秋季講演会予稿集  2000/10
• Structure of II-VI semiconductor ultra-fine particles covered with SiO or carbon layer.  [Not invited]

  TANIGAKI TOSHIAKI, KIMURA YUKI, KIMURA SEIJI, SAITO YOSHIO, KAITO CHIHIRO

  日本結晶成長学会誌  2000/07
• Crystallization of WO3 thin film.  [Not invited]

  KIMURA YUKI, HANAMOTO KATSUMI, NAKAYAMA YASUYUKI, KAITO CHIHIRO

  日本結晶成長学会誌  2000/07
• Crystallization of vacuum evaporated amorphous SnO2 film.  [Not invited]

  KOBAYASHI TAKAHITO, KIMURA YUKI, HANAMOTO KATSUMI, NAKAYAMA YASUYUKI, KAITO CHIHIRO

  日本結晶成長学会誌  2000/07
• KBr‐NaCl逐次蒸着膜におけるNaBr層の形成  [Not invited]

  木村勇気, 木村誠二, 中田俊隆, 斎藤嘉夫, かい内千尋

  日本物理学会講演概要集  1999/09
• Spontaneous Growth of Binary Alkali Halide Crystal by successive Evaporation.  [Not invited]

  KIMURA YUKI, KIMURA SEIJI, NAKADA TOSHITAKA, SAITO YOSHIO, KAITO CHIHIRO

  日本結晶成長学会誌  1999/07
• KBr‐KCl蒸着膜による二元アルカリハライド化合物  [Not invited]

  木村勇気, 木村誠二, 斎藤嘉夫, かい内千尋, 中田俊隆

  日本物理学会講演概要集  1999/03
• 有機分子進化におけるFT反応の寄与  [Not invited]

  KIMURA Yuki

  新学術領域「宇宙分子進化」全体集会

Association Memberships

• Microscopy Society of America   THE JAPAN SOCIETY OF MICROGRAVITY APPLICATION   アメリカ天文学会   JAPAN GEOSCIENCE UNION   日本天文学会   日本物理学会   日本惑星科学会   結晶成長学会   

Works

• 気相からの核形成と宇宙ダスト

  2013 -2014
• 気相からの核形成と宇宙ダスト

  2013 -2014
• 気相からの核形成と宇宙ダスト

  2012 -2013
• 気相からの核形成と宇宙ダスト

  2012 -2013
• 宇宙の塵（ちり）の不思議なでき方

  2011 -2012
• 気相からの核形成と宇宙ダスト

  2011 -2012
• 宇宙の塵（ちり）の不思議なでき方

  2011 -2012
• 気相からの核形成と宇宙ダスト

  2011 -2012
• 液体のように振舞う固体：ナノ領域の拡散現象と天文学

  2009 -2012
• 液体のように振舞う固体：ナノ領域の拡散現象と天文学

  2009 -2012
• 月面基地建設の為の月資源からの酸素抽出とセメント製造、セメントペーストの流動性予測及び月コンクリート迅速評価の基礎的研究

  2009 -2010
• 原始惑星系円盤における低温結晶成長過程

  2009 -2010
• ナノ粒子の特異現象を取り入れたその場観察実験による宇宙ダスト生成過程の解明

  2009 -2010
• 液体のように振舞う固体：ナノ領域の拡散現象と天文学

  2009 -2010
• Nano Dust in the Solar System: Formation, Interactions and Detection

  2009 -2010
• 月面基地建設の為の月資源からの酸素抽出とセメント製造、セメントペーストの流動性予測及び月コンクリート迅速評価の基礎的研究

  2009 -2010
• 原始惑星系円盤における低温結晶成長過程

  2009 -2010
• ナノ粒子の特異現象を取り入れたその場観察実験による宇宙ダスト生成過程の解明

  2009 -2010
• 液体のように振舞う固体：ナノ領域の拡散現象と天文学

  2009 -2010
• Nano Dust in the Solar System: Formation, Interactions and Detection

  2009 -2010

Research Projects

• Exploring new indicators representing the hygroscopicity of atmospheric organic aerosol

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2023/04 -2027/03 

  Author : 持田 陸宏, 佐藤 圭, 石塚 紳之介, 木村 勇気, 松井 仁志, 宮崎 雄三, 大畑 祥
• 水/氷界面に生成する同素不混和水の構造多様性の解明

  北海道大学低温科学研究所共同研究(開拓型)

  Date (from‐to) : 2024/04 -2027/03 

  Author : 新家寛正, 木村勇気, 灘浩樹, 羽馬哲也
• 原始太陽系星雲内における分子生成効率の理解に向けた氷ナノ粒子の核生成実験

  日本学術振興会：科学研究費助成事業

  Date (from‐to) : 2023/04 -2025/03 

  Author : 木村 勇気
• Paradigm shift in the method for observing non-equilibrium processes in real space: Elucidation of nucleation processes from solution by TEM

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2020/08 -2025/03 

  Author : 木村 勇気, 瀧川 一学, 川野 潤, 田中 今日子

   

  本研究課題は、水溶液からの核生成の透過型電子顕微鏡“その場”観察実験を軸に、水和層の役割を理解するために、水和層の無い気相からの核生成実験などを対照実験として実施する。水溶液からの核生成の透過型電子顕微鏡“その場”観察実験では、溶液試料を観察できる3つの手法（窓板ホルダー、溶液セル、グラフェン膜）から、核生成のその場観察に最も適した手法として初年度に選定を行った窓板ホルダーを用いて、機械学習による核生成の予測に必須の教師データの取得を行った。その結果、低電子線画像と高電子線画像をそれぞれ1,000枚取得して教師画像セットを準備することで低電子線量で得た暗い像を電子線量にして1万倍程度明るくすることに成功した。さらに、溶液から核生成する粒子を早期に検出することにも成功した。また、電子線が溶媒である水を放射性分解することで、結晶化条件が変化してしまうことをできるだけ避けるために、電子線をパルス化するシステムを導入した。テスト試料としてステアリン酸結晶の電子線損傷を調べた結果、照射時間が10%になるようにパルス幅を調整した所、結晶の寿命は10倍以上に延びる結果が得られており、想定以上に効果があることが分かった。 溶液からの核生成では、水和層が重要な役割を果たしていると考えられている。そこで、初年度に引き続き、水和層のない気相からの核生成実験を行い、その過程を干渉計でその場観察して核生成時の温度、圧力と過飽和度増加の時間スケールから核生成理論式に必須の物理量を炭素、チタン、炭化チタンに対して求めて論文を投稿した。
• 結晶成長過程における相転移機構の解明

  北海道大学低温科学研究所：

  Date (from‐to) : 2023/04 -2024/03 

  Author : 釣優香, 木村勇気, 山﨑智也
• Discovery of key factors in nucleation processes from aqueous solution by direct TEM observation

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2020/04 -2021/03 

  Author : 木村 勇気, 瀧川 一学, 川野 潤, 田中 今日子

   

  核生成は物質形成の最初期のプロセスであり、科学から産業に至る様々な分野の鍵となるにもかかわらず、その理解は極めて限定的である。これは、核生成がナノ領域で高速に、かつ確率的におこる現象で実空間観察が非常に困難なためである。 本研究では、「安定核の生成までに何が起こっているのか？」、「安定核の生成ルートはどのように決まるのか？」を核心をなす問いに据え、溶液中の核生成に影響する各因子の寄与の程度と物質依存性を明らかにし、核生成ルートを決めるキーファクターに制限を加えることを目的に研究を行った。キーファクターは、核生成理論式に必須の“核と水の界面エネルギー”とカイネティック係数(分子の取り込まれやすさ)、ダイマーの形成、脱水和や粘性、界面近傍のpHやイオン濃度、ナノ粒子特有の物性などである。 TEM観察では、結晶の成長速度、形、集合、配列、サイズなどを直接観察でき、加えて電子回折パターンで相同定も同時に行えるため、核生成の理解に対して飛躍的な成果が見込める。そのため、目的の達成には溶液から前駆体を経て結晶ができるまでの核生成過程の一部始終をTEMにより実空間で可視化するのが最も近道であると考えている。本研究課題の間には、TEM観察するうえでボトルネックとなっている、確率的な核生成現象を偶然に頼って観察している状況に対し、機械学習を取り入れることで核生成の時間と場所を予測して能動的に核生成の一部始終をTEM観察するという革新的な手法の構築に取り組んだ。その結果、人間の眼で判断するよりも早く核生成を捉えることに成功した。この研究は基盤研究（S）に発展的内容で引き継がれた。
• Nucleation

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2015/04 -2020/03 

  Author : Kimura Yuki

   

  We established an original experimental system to approach the initial process of crystallization. As a result, we found that the key factors controlling the nucleation from the gas phase are decreasing the melting point and the sticking probability of nanoparticles. We also established a transmission electron microscopy for in-situ observation of the nucleation processes from a solution in nanoscale. Then, we elucidated the role of the hydration layer in protein crystallization. For the first time, we have succeeded in directly demonstrating the relationship between nucleation and precursors in terms of the specificity that appears in the nanoscale by handling both vapor and solution phases. Furthermore, we clarified that the understanding of nucleation requires not only the formation of critical nuclei but also the growth beyond the nano-region to stable bulk crystals. Furthermore, we proposed a nucleation model that takes into account the physical properties of the nano-region.
• Formation and evolution of organic materials in protoplanetary disks

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2013/06 -2018/03 

  Author : Nagahara Hiroko

   

  Formation of organic molecules on the surface of solid materials in protoplanetary disks are experimentally performed. Gas species are hydrogen and carbon oxide, the two most abundant species, and the solids are Fe-, Ni-, and FeNi- metals and amorphous silicate. Methane and linear chain compound are formed. The reaction takes place at lower temperatures on ice than that on amorphous silicates. Micro-XANES equipment has been developed in a beam line of Spring-8 in order to observe organics formation reactions in situ and analyze the chemical bonds. The new equipment enables us to observe and analyze organic and inorganic materials by using energy edges, which was used for the experimental samples by other teams of the current research project. Theoretical study on the surface of silicates, metals, and amorphous silicate were conducted on the basis of the first principle calcuration. A new physico-chemical model on the solar system evolution has been developed.
• Nanometer-scale paleomagnetism by the electron holography

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2016/04 -2018/03 

  Author : Kimura Yuki, YAMAMOTO Kazuo, TANIGAKI Toshiaki, NAKAMURA Norihiro

   

  We applied well known paleomagnetism to a nanometer-scale mineral in a meteorite for determination of temperature and magnetic field at the time of formation of nano-minerals in a mother asteroid of carbonaceous chondrite 4.6 billion years ago based on magnetic remnant observed using the electron holography. We successfully visualized a magnetic remnant of individual nano-minerals, which has been hidden in a total bulk value in case of traditional bulk analysis. We focused on magnetite particles in a carbonaceous meteorite and successfully determined its formation temperature in their parent body based on in-situ electron holography observation in a heating experiment.
• フルイド反応透過電子顕微鏡を用いた微粒子合成と光触媒活性の溶液中その場観察研究

  日本学術振興会：日本学術振興会 二国間交流事業共同研究

  Date (from‐to) : 2015/04 -2017/03 

  Author : 木村 勇気
• 気相からの核生成と宇宙ダスト

  国立研究開発法人宇宙航空研究開発機構：平成28年度短時間微小重力実験

  Date (from‐to) : 2016/10 -2017/02 

  Author : 木村 勇気
• Development of ultrahigh vacuum (UHV) transmission electron microscope for in-situ observation of ice

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2013/10 -2016/03 

  Author : Kouchi Akira, HIDAKA Hiroshi, OBA Yasuhiro, HAMA Tetsuya, CHIGAI Takeshi, WATANABE Naoki, KIMURA Yuki, TOMARU Takayuki

   

  An ultrahigh vacuum (UHV) transmission electron microscope for in-situ observation of ice has been developed. We use a single tilt liquid He cooling holder for specimen cooling to 4 K. Two ports are directed to the specimen surface for in-situ studies: gas-inlet, and UV irradiation. Results of preliminary observation are as follows: (1) Macroscopic defect structure of vapor-deposited amorphous ice are observed at first time. (2) Formation of ice XI by UV irradiation onto ices Ih and Ic are observed at 75-100 K. On the other hand, no structural change has been observed by UV irradiation onto amorphous ice. (3) Formation of high-density amorphous ice by CO matrix sublimation method has been developed.
• Ultra-high Speed Crystallization in the Primitive Solar System

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2010/04 -2014/03 

  Author : TSUKAMOTO Katsuo, NAKAMURA Tomoki, NAKAMOTO Taishi, INATOMI Yuko, NAKAMURA Norihiro, KIMURA Yuki, MIRUA Hitoshi

   

  In-situ observations of crystallization from chondrule melts have successfully been conducted using gas get levitation method. It was found that hypercooling of 300-1100K is needed for the reproduction of various chondrule textures and the crystallization finishes within a few seconds. Based on the experimental data, a new kinetic model could be proposed for the chondrule texture formation.
• In-situ observation of nucleation from a solution using an ionic liquid in a TEM

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2013 -2014 

  Author : KIMURA Yuki

   

  Nucleation via metastable phases has been studied very attractively in recent years. In this study, we succeeded to visualize nucleation process by a novel method, which uses an ionic liquid solution instead of water solution, using in-situ transmission electron microscopy. We observe simultaneous formation of stable and metastable crystals. In addition, metastable crystals are immediately incorporated into a stable crystal, when they contact each other. Although the growth rate of metastable crystal is similar with stable crystal, the dissolution rate of metastable crystal is faster than that of stable crystal suggesting that final crystal is a result of this competition of formation and dissolution.
• Experimental approaches to reveal formation process of cosmic dust taken into account singular properties in mesoscale

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2012 -2014 

  Author : KIMURA Yuki

   

  We succeeded to measure the temperature and concentration of a vapor at the moments of nucleation using a specially designed interferometer. Surface free energy and sticking probability of nanoparticles can be determined based on nucleation theories. As the result, it has been found that extremely high supersaturation of ten to the power of 4th to 14th has been required and for homogeneous nucleation and then the sticking probability is as small as 0.01%. In addition, the nuclei form as a liquid phase and crystallize as temperature drops and, therefore, structure of nuclei does not determine at the time of initial nucleation.
• Research of IR spectral features caused by nanoparticle surfaces and metastable crystal structure

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(挑戦的萌芽研究)

  Date (from‐to) : 2010 -2011 

  Author : Yuki KIMURA, Itsuki SAKON

   

  There are a lot of unidentified infrared (UIR)features in the astronomical spectra. We assumed the reason that is characteristic physical parameters of nanoparticles, because no one ever considers the properties of nanoparticle, although cosmic dust has nanometer in size. To identify the UIR features, we constructed a new system, which is able to measure IR spectra of free frying as-grown nanoparticles. Our results showed that the free frying nanoparticles have different features compared with that in the spectra of bulk and nanoparticles embedded into a KBr pellets. UIR features will be identified based on our concept.
• 液体のように振舞うナノ粒子:宇宙ダスト類似物の生成過程を観る“その場"観察実験

  文部科学省：科学研究費補助金(若手研究(A))

  Date (from‐to) : 2010 -2011 

  Author : 木村 勇気

   

  惑星系の形成過程に伴う物質進化過程の解明という地球惑星科学の第一級の課題に対して、宇宙固体微粒子(宇宙ダスト)の形成や結晶化過程を実験的に解明する。宇宙ダストは容器の無い宇宙空間で生成する為に、大きな過冷却度がついた後に生成することが容易に想像できる。特に、気相からの凝縮実験(煙の実験)において非接触で生成するナノ粒子の成長過程を干渉計を用いてその場観察することで、気相中でのナノ粒子生成時の核形成温度(過冷却度)や成長速度などを定量化することが目的である。ここで、ナノ粒子の"液体のような"非常に早い拡散現象が鍵になると考えている。物質科学と地球惑星科学分野との境界領域に新たな研究分野を形成する研究課題になる。初年度に組んだ、2波長マッハツェンダー干渉計を用いて、核形成温度と濃度を同時に測定することに成功した。また、凝縮温度と生成粒子のサイズを同時に説明可能なナノ粒子の"実効的な"表面張力と吸着係数を、核生成理論を用いることで同時に決定できることが明らかになり、当初の想定以上の成果を挙げられた。例えば、マンガンに関しては、表面エネルギーはナノ粒子であっても、バルクと同程度の値で、吸着係数は約0.4であった。さらに、ナノ粒子の融点降下や拡散速度の特異現象により液滴状融合成長が頻繁に起こることで核の数を減らす現象を定量的に示した。これにより、実際に宇宙ダストが生成する温度、そのサイズ、数密度などを核生成理論から予測可能になると期待される。
• ナノ領域の特異現象と46億年前の微粒子形成

  科学研究費補助金

  Date (from‐to) : 2008 -2011
• Grain formation 4.6 Billion Years Ago based on anomalous phenomena appeared in nano-region

  Grant-in-Aid for Scientific Research

  Date (from‐to) : 2008 -2011
• Experimental approach concerning behavior of cosmic dust particlesboth inorganic and organic in proto Solar nebula

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(若手研究(スタートアップ))

  Date (from‐to) : 2007 -2008 

  Author : Yuki KIMURA

   

  宇宙固体微粒子(ダスト)の類似物としての微粒子を実際に研究室で合成し、その光学特性や高温での振る舞い等を調べる事で、星・惑星形成過程におけるダストの果たす役割を明らかとする事を目的に研究を展開した。その結果、(1)結晶質珪酸塩微粒子の生成条件と非晶質珪酸塩微粒子の低温での結晶化過程を明らかにした。(2) 質量に依存しない酸素の同位体分別を示す珪酸塩微粒子の生成に世界で初めて成功し、ダストの生成にプラズマが重要であることをしめした。(3) 様々な天体に幅広く分布しているPAH のクラスターを実験室で再現し、その光学特性を明らかにした。
• 原始太陽系星雲中での無機・有機ダストの振る舞いに関する実験的アプローチ」

  科学研究費補助金

  Date (from‐to) : 2007 -2008
• 宇宙環境下でのダストの創製・変成・挙動に関する実験的アプローチ

  科学研究費補助金

  Date (from‐to) : 2004 -2006
• ナノ構造粒子の創製および特異現象の解明実験

  日本学術振興会：科学研究費補助金

  Date (from‐to) : 2002 -2003 

  Author : 木村 勇気

   

  ナノ領域で見られる特異現象が半導体やナノチューブなども含めて今後のナノ機能性物質創製のキーポイントになる。そこで、昨年度研究費にて購入した動的観察画像処理装置を活用し、我々の研究室に設置されている高分解能電子顕微鏡とを結びつけることで、ナノ粒子の動的挙動をシステマティックに明らかにしてきた。ここでの成果は、物性分野から天文分野に広く展開され、研究費を使用して国内外問わず、種々の分野(Astrophysics of Dust Symposium、惑星科学会、結晶成長学会、日本物理学会、月・惑星シンポジウム、微粒子プラズマ研究会、天文学会(3月23日発表予定))で公表した。 動的観察画像処理装置を活用する事で、様々な元素を含んだカーボン薄膜における触媒効果の特異性、及び高温度領域における動的現象を原子オーダーで明らかにした。特にシリコンを含んだカーボン膜においてはナノダイヤモンドが優先的に生成する事を見出し、Journal of Crystal Growthに論文として発表した。また、チタンを含んだカーボン膜においては、真空加熱によりナノチューブが生成する事を電子顕微鏡中加熱による直接観察から明らかとした。さらに、触媒として鉄やコバルトといった遷移金属を用いる事で、カーボン膜中からカルビン、グラファイト、炭化物が加熱温度を調節する事により選択的に生成できることを見出した。これらの結果は論文としてまとめ、現在投稿中である。本研究は、元素を選ぶ事でカーボンの持つ多系をコントロール出来る画期的な成果といえる。 また、宇宙塵として注目を集めているSi、Ti、Zrの炭化物を作成し、構造と赤外吸収を結びつけた手法を用いることで惑星科学の観測の分野とも連携して研究を展開した。研究費を活用して5月にアメリカのデンバーで開かれたダストに関する国際会議に出席し、成果の公表を行なうとともに、論文としてまとめ、Monthly Notices、A&Aに掲載された。また、TiCグレインに関する研究の発展的内容がApJ Supplement Seriesに掲載の運びとなった。 今年度の成果として、投稿論文20編が発表された。

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• ナノ粒子特有の振る舞いから宇宙の謎に迫る

  Date (from-to) : 2017/11/11-2017/11/11

  Role : Lecturer

  Event, Program, Title : 第26回先端科学移動大学2017（市民講座）

  General 旭川市科学館「サイパル」
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  Date (from-to) : 2017/11/10-2017/11/10

  Role : Lecturer

  Event, Program, Title : 第26回先端科学移動大学2017（高等学校訪問授業）

  旭川南高等学校