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研究者情報

マスター

アカウント（マスター）

  • 氏名

    木村　勇気(キムラ　ユウキ), キムラ　ユウキ

所属（マスター）

  • 低温科学研究所　雪氷新領域部門

所属（マスター）

  • 低温科学研究所　雪氷新領域部門

独自項目

syllabus

  • 2021, 宇宙低温物質科学特論, Advanced Course in Planetary Material Science, 修士課程, 理学院, 星間分子雲，彗星，化学進化，ダスト、核生成、結晶成長、地球外有機物，生命の起源、電子顕微鏡、ナノ粒子
  • 2021, 大学院共通授業科目（一般科目）：自然科学・応用科学, Inter-Graduate School Classes(General Subject):Natural and Applied Sciences, 修士課程, 大学院共通科目, 宇宙、構造、形成・進化
  • 2021, 宇宙理学入門, Introduction to Cosmosciences, 修士課程, 理学院, 宇宙、構造、形成・進化

researchmap

プロフィール情報

所属

  • 北海道大学, 大学院理学院 宇宙理学専攻, 教授

学位

  • 博士 （理学）（立命館大学）

プロフィール情報

  • 姓

    木村, キムラ

  • 名

    勇気, ユウキ

  • ID各種

    200901020947437592

対象リソース

所属

  • 北海道大学, 大学院理学院 宇宙理学専攻, 教授

業績リスト

研究キーワード

  • 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   

研究分野

  • 自然科学一般 / 磁性、超伝導、強相関系
  • 自然科学一般 / 宇宙惑星科学
  • 自然科学一般 / 天文学
  • 自然科学一般 / 固体地球科学
  • ナノテク・材料 / ナノ構造物理
  • ナノテク・材料 / ナノ構造化学

経歴

  • 2023年03月 - 現在 北海道大学 低温科学研究所 教授
  • 2014年04月 - 2023年02月 北海道大学 低温科学研究所 准教授
  • 2009年01月 - 2014年03月 東北大学 理学(系)研究科(研究院) 助教
  • 2008年04月 - 2008年12月 北海道大学 研究員
  • 2006年05月 - 2008年03月 立命館大学 研究員
  • 2004年04月 - 2006年04月 NASA 学術振興会海外特別研究員
  • 2004年 - 2006年 NASA, Goddard Space Flight Center
  • 2002年04月 - 2004年03月 立命館大学 学術振興会特別研究員 PD
  • 2001年04月 - 2002年03月 立命館大学 助手

学歴

  •         - 2002年   立命館大学   理工学研究科   物質理工学専攻
  •         - 2001年   立命館大学   理工学研究科   物質理工学専攻
  •         - 1999年   立命館大学   理学部   数学物理学科 物理学課程

委員歴

  • 2019年07月 - 現在   国際結晶学連合   国際宇宙空間研究委員会（COSPAR）代表
  • 2016年04月 - 現在   日本結晶成長学会   理事
  • 2015年09月 - 現在   宇宙航空研究開発機構宇宙科学研究所   観測ロケット専門委員会委員
  • 2015年09月 - 現在   宇宙航空研究開発機構宇宙科学研究所   宇宙環境利用専門委員会委員
  • 2015年06月 - 現在   文部科学省   宇宙航空科学技術推進委託費審査評価会専門ワーキンググループ委員
  • 2006年 - 現在   日本惑星科学会 編集委員会   委員   日本惑星科学会 編集委員会
  • 2015年04月 - 2020年12月   日本惑星科学会   総務専門委員会 行事部会
  • 2007年 - 2009年   日本惑星科学会 学会賞選考委員   幹事   日本惑星科学会 学会賞選考委員

受賞

  • 2024年04月 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年03月 日本金属学会 第73回金属組織写真賞 奨励賞
  • 2022年07月 日本セラミックス協会 第47回学術写真賞 最優秀賞
  • 2021年03月 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年10月 日本結晶成長学会 第36回論文賞
     均質核生成実験による宇宙塵の生成過程の解明 
    受賞者: 木村 勇気
  • 2019年05月 日本地球惑星科学連合 第3回西田賞
     
    受賞者: 木村 勇気
  • 2019年02月 北海道大学 平成30年度北海道大学教育研究総長表彰（研究）
     
    受賞者: 木村 勇気
  • 2018年02月 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年01月 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年01月 北海道大学 北海道大学研究総長賞
     
    受賞者: 木村 勇気
  • 2016年10月 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年03月 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年 "Schieber Prize", the International Organization for Crystal Growth
  • 2012年 日本物理学会領域9若手奨励賞
  • 2011年 Best Poster Award at the International Conference on Materials for Advanced Technologies, 2011.
  • 2010年 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年 International School of Crystallization 2009 Accommodation Grant
  • 2008年 日本結晶成長学会 第六回奨励賞
  • 2007年 2006年度 日本惑星科学会 最優秀研究者賞
  • 2002年 第32回 結晶成長国内会議 講演奨励賞

論文

  • Yuga Yashima, Tomoya Yamazaki, Yuki Kimura
    ACS omega 9 38 39914 - 39924 2024年09月24日 
    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.
  • Hiromasa Niinomi, Hiroki Nada, Tomoya Yamazaki, Tetsuya Hama, Akira Kouchi, Tomoya Oshikiri, Masaru Nakagawa, Yuki Kimura
    The Journal of Physical Chemistry C 2024年09月09日
  • 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 2024年05月
  • 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年04月29日 
    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.
  • Yuki Nakano, Yuki Kimura, Akihiko Hashimoto
    Monthly Notices of the Royal Astronomical Society: Letters 2024年03月29日
  • 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年01月29日 
    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.
  • Hiromasa Niinomi, Tomoya Yamazaki, Hiroki Nada, Tetsuya Hama, Akira Kouchi, Tomoya Oshikiri, Masaru Nakagawa, Yuki Kimura
    The Journal of Physical Chemistry Letters 659 - 664 2024年01月11日
  • 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 2023年12月22日 
    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.
  • 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年12月21日 
    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.
  • Yuki KIMURA, Hiroyasu KATSUNO, Shizuka HIRAKAWA, Tomoya YAMAZAKI
    Vacuum and Surface Science 66 12 700 - 705 2023年12月10日
  • Joonsoo Kim, Yuki Kimura, Brian Puchala, Tomoya Yamazaki, Udo Becker, Wenhao Sun
    Science (New York, N.Y.) 382 6673 915 - 920 2023年11月24日 
    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.
  • Tomoya Yamazaki, Akira Kouchi, Ken-ichiro Murata, Hiroyasu Katsuno, Hiroki Nada, Tetsuya Hama, Yuki Kimura
    Monthly Notices of the Royal Astronomical Society 2023年11月06日 
    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.
  • Hiromasa Niinomi, Tomoya Yamazaki, Hiroki Nada, Tetsuya Hama, Akira Kouchi, Tomoya Oshikiri, Masaru Nakagawa, Yuki Kimura
    Scientific Reports 13 1 2023年10月11日 
    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 Ih, 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.
  • 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 2023年09月 
    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.
  • 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 2023年08月29日 
    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.
  • Akira Kouchi, Tomoya Yamazaki, Hiroyasu Katsuno, Hiroki Nada, Tetsuya Hama, Yuki Kimura
    Chemical Physics 572 111966 - 111966 2023年08月
  • 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 2023年02月 
    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.
  • Yuki Kimura, Kyoko K. Tanaka, Yuko Inatomi, Coskun Aktas, Jürgen Blum
    Science Advances 9 2 2023年01月13日 
    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.
  • 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 2022年11月
  • Yoko Ohtomo, Jeehyun Yang, Miu Nishikata, Daisuke Kawamoto, Yuki Kimura, Tsubasa Otake, Tsutomu Sato
    Minerals 2022年08月30日 
    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.
  • 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年08月22日 
    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.
  • Tomoya Yamazaki, Hiromasa Niinomi, Yuki Kimura
    Microscopy (Oxford, England) 71 4 231 - 237 2022年08月01日 
    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.
  • Yuta Sasaki, Tomoya Yamazaki, Yuki Kimura
    ACS Applied Nano Materials 2022年07月22日
  • Yuki Kimura, Hiroyasu Katsuno, Tomoya Yamazaki
    Faraday discussions 235 81 - 94 2022年07月14日 
    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.
  • Yuki Kimura, Kyoko K. Tanaka, Yuko Inatomi, Frank T. Ferguson, Joseph A. Nuth
    ASTROPHYSICAL JOURNAL LETTERS 934 1 2022年07月 
    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.
  • Hiromasa Niinomi, Akira Kouch, Tetsuya Hama, Hiroki Nada, Tomoya Yamazaki, Yuki Kimura
    JOURNAL OF PHYSICAL CHEMISTRY LETTERS 13 19 4251 - 4256 2022年05月 
    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.
  • Yuki Kimura
    Microscopy 2022年01月29日 
    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.
  • 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 2022年 [査読有り][招待有り]
  • Hiroyasu Katsuno, Yuki Kimura, Tomoya Yamazaki, Ichigaku Takigawa
    Frontiers in chemistry 10 818230 - 818230 2022年 [査読有り]
     
    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.
  • 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 49 1 n/a  日本結晶成長学会 2022年
  • 勇気 木村
    顕微鏡 2021年12月30日
  • 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年12月08日 
    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.
  • Kyoko Tanaka, Ingrid Mann, Yuki Kimura
    Atmospheric Chemistry and Physics 2021年10月14日 
    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.
  • 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 2021年09月01日 [査読有り]
  • 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 2021年08月01日 [査読有り]
  • Yuki Kimura, Kazuo Yamamoto, Shigeru Wakita
    The Astrophysical Journal Letters 917 1 L5 - L5 2021年08月01日 [査読有り]
  • 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 2021年06月03日 [査読有り]
     
    ABSTRACT 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.
  • Tomoya Yamazaki, Yuki Kimura
    Microscopy and Microanalysis 27 3 459 - 465 2021年06月 [査読有り]
     
    Abstract
  • Hiroyasu Katsuno, Yuki Kimura, Tomoya Yamazaki, Ichigaku Takigawa
    CoRR abs/2106.01718 2021年
  • Yohei Igami, Akira Tsuchiyama, Tomoya Yamazaki, Megumi Matsumoto, Yuki Kimura
    Geochimica et Cosmochimica Acta 293 86 - 102 2021年01月 [査読有り]
     
    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+
  • 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年12月 [査読有り][通常論文]
  • 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 2020年08月20日 [査読有り]
  • Kichitaro Nakajima, Tomoya Yamazaki, Yuki Kimura, Masatomo So, Yuji Goto, Hirotsugu Ogi
    The journal of physical chemistry letters 11 15 6176 - 6184 2020年08月06日 [査読有り]
     
    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.
  • 木村勇気, 佐藤理佳子, 𡈽山明, 為則雄祐, 羽馬哲也, 日髙宏, 渡部直樹, 香内晃, 永原裕子
    低温科学 78 79 - 90 2020年03月 [査読有り]
  • Tomoya Yamazaki, Alexander E. S. Van Driessche, Yuki Kimura
    Soft Matter 16 8 1955 - 1960 2020年 [査読有り]
     

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

  • Aki Takigawa, Yoshihiro Furukawa, Yuki Kimura, Bjorn Davidsson, Tomoki Nakamura
    ASTROPHYSICAL JOURNAL 881 1 27  2019年08月 [査読有り][通常論文]
     
    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.
  • Masashi Tsuge, Tetsuya Hama, Yuki Kimura, Akira Kouchi, Naoki Watanabe
    The Astrophysical Journal 878 1 23  2019年06月 [査読有り][通常論文]
     
    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.
  • Kyoko K. Tanaka, Yuki Kimura
    Physical Chemistry Chemical Physics 21 2410 - 2418 2019年01月 [査読有り][通常論文]
  • 左近樹, 遠藤いずみ, 池内綾人, 尾中敬, 木村勇気, 木村誠二, 和田節子, 中村正人, 市村淳, 小川奈々子, 大河内直彦, 稲富裕光
    航空宇宙学会誌 66 12 381 - 387 一般社団法人 日本航空宇宙学会 2018年12月 [査読有り][通常論文]
     

    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．

  • 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年11月01日 [査読有り][通常論文]
  • Shinnosuke Ishizuka, Yuki Kimura, Itsuki Sakon, Hiroshi Kimura, Tomoya Yamazaki, Shinsuke Takeuchi, Yuko Inatomi
    Nature Communications 9 1 3820 - 3820 2018年09月 [査読有り][通常論文]
     
    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.
  • 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  2018年07月 [査読有り][通常論文]
     
    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).
  • Y. Kimura, M. Tsuge, V. Pirronello, A. Kouchi, N. Watanabe
    Astrophysical Journal Letters 858 2 23  2018年05月10日 [査読有り][通常論文]
     
    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.
  • Hisao Satoh, Yuki Kimura, Erika Furukawa
    Industrial and Engineering Chemistry Research 57 1 79 - 83 2018年01月10日 [査読有り][通常論文]
     
    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.
  • 超高真空極低温透過型電子顕微鏡の開発、─氷のその場観察をめざして─
    香内晃, 日高宏, 羽馬哲也, 木村勇気, 渡部直樹, 中坪俊一, 藤田和之, 新堀邦夫, 池田正幸
    日本雪氷学会誌 雪氷 80 1 19 - 36 2018年01月 [査読有り][通常論文]
  • Kaori Yokoyama, Yuki Kimura, Chihiro Kaito
    ACS EARTH AND SPACE CHEMISTRY 1 10 601 - 607 2017年12月 [査読有り][通常論文]
     
    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.
  • 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年09月 [査読有り][通常論文]
     
    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.
  • Shinnosuke Ishizuka, Yuki Kimura, Satoki Yokoi, Tomoya Yamazaki, Rikako Sato, Tetsuya Hama
    NANOSCALE 9 28 10109 - 10116 2017年07月 [査読有り][通常論文]
     
    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.
  • Tetsuya Hama, Shinnosuke Ishizuka, Tomoya Yamazaki, Yuki Kimura, Akira Kouchi, Naoki Watanabe, Toshiki Sugimoto, Valerio Pirronello
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 27 17677 - 17684 2017年07月 [査読有り][通常論文]
     
    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.
  • Rafael Escribano, Emilio Artacho, Akira Kouchi, Tetusya Hama, Yuki Kimura, Hiroshi Hidaka, Naoki Watanabe
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 10 7280 - 7287 2017年03月 [査読有り][通常論文]
     
    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.
  • Rafael Escribano, Emilio Artacho, Akira Kouchi, Tetusya Hama, Yuki Kimura, Hiroshi Hidaka, Naoki Watanabe
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 10 7280 - 7287 2017年03月 [査読有り][通常論文]
     
    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.
  • 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  2017年03月 [査読有り][通常論文]
     
    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.
  • 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 2017年02月 [査読有り][通常論文]
     
    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.
  • 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 2017年02月 [査読有り][通常論文]
     
    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.
  • 木村 勇気
    日本結晶成長学会誌 44 1 11 - 16 日本結晶成長学会 2017年 

      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.

  • 西方 美羽, 大友 陽子, 大竹 翼, 木村 勇気, 川本 大祐, 佐藤 努
    日本地球化学会年会要旨集 64 310 - 310 一般社団法人日本地球化学会 2017年 

    縞状鉄鉱層中のクロムのホスト鉱物はクロムスピネルであるがその起源は明らかになっていない。本研究では縞状鉄鉱層の初期沈殿物を模した鉄、クロム水酸化物を合成しフロースルー型実験装置を用いて二価鉄を含む150℃の熱水と1週間反応させた。生成物の固体分析の結果から主生成物がゲーサイトでありさらにスピネル鉱物が生成していることがわかった。さらにSEM分析ではスピネル様の結晶が観察でき、TEM分析からスピネル鉱物と同様の面間隔の値を持つクロムを含むスピネル様の粒子の凝集体が観察されたことからクロムスピネルが熱水実験により合成されたことが明らかになった。

  • 木村 勇気, 石塚 紳之介, 田中 今日子, 竹内 伸介, 稲富 裕光
    日本物理学会講演概要集 72 0 2571 - 2571 一般社団法人 日本物理学会 2017年 

    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。

  • K. Ishii, Y. Kimura, T. Yamazaki, Y. Oaki, H. Imai
    RSC Advances 7 57 35711 - 35716 2017年 [査読有り][通常論文]
     
    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.
  • Yuki Kimura, Kyoko K. Tanaka, Takaya Nozawa, Shinsuke Takeuchi, Yuko Inatomi
    SCIENCE ADVANCES 3 1 e1601992  2017年01月 [査読有り][通常論文]
     
    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.
  • Shinnosuke Ishizuka, Yuki Kimura, Tomoya Yamazaki, Tetsuya Hama, Naoki Watanabe, Akira Kouchi
    CHEMISTRY OF MATERIALS 28 23 8732 - 8741 2016年12月 [査読有り][通常論文]
     
    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
  • Shinnosuke Ishizuka, Yuki Kimura, Tomoya Yamazaki
    JOURNAL OF CRYSTAL GROWTH 450 168 - 173 2016年09月 [査読有り][通常論文]
     
    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.
  • A. Kouchi, T. Hama, Y. Kimura, H. Hidaka, R. Escribano, N. Watanabe
    CHEMICAL PHYSICS LETTERS 658 287 - 292 2016年08月 [査読有り][通常論文]
     
    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.
  • 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 728 062006  {IOP} Publishing 2016年07月 [査読有り][通常論文]
  • Yuki Kimura, Kenta Murayama, Tomoya Yamazaki, Takao Maki
    PROGRESS IN CRYSTAL GROWTH AND CHARACTERIZATION OF MATERIALS 62 2 400 - 403 2016年06月 [査読有り][通常論文]
     
    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.
  • 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  2016年03月 [査読有り][通常論文]
     
    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.
  • 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  2016年02月 [査読有り][通常論文]
     
    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.
  • 木村 勇気
    日本物理学会講演概要集 71 2609 - 2610 一般社団法人日本物理学会 2016年
  • Mihiro Takasaki, Yuki Kimura, Tomoya Yamazaki, Yuya Oaki, Hiroaki Imai
    RSC ADVANCES 6 66 61346 - 61350 2016年 [査読有り][通常論文]
     
    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.
  • Tomoya Yamazaki, Manabu Shirai, Hiroaki Matsumoto, Yuki Kimura
    Microscopy and Microanalysis 21 S3 255 - 256 2015年08月 [査読無し]
  • Moe Matsuoka, Tomoki Nakamura, Yuki Kimura, Takahiro Hiroi, Ryosuke Nakamura, Satoshi Okumura, Sho Sasaki
    ICARUS 254 135 - 143 2015年07月 [査読有り][通常論文]
     
    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.
  • 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  2015年06月 [査読有り][通常論文]
     
    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.
  • Shinnosuke Ishizuka, Yuki Kimura, Itsuki Sakon
    ASTROPHYSICAL JOURNAL 803 2 88  2015年04月 [査読有り][通常論文]
     
    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.
  • 木村勇気, 石塚紳之介, 田中今日子, 左近樹, 竹内伸介, 稲富裕光
    Space Utilization Research 29 29 100 - 102 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS) 2015年 [査読無し][通常論文]
     
    第29回宇宙環境利用シンポジウム (2015年1月24日-25日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)), 相模原市, 神奈川県資料番号: SA6000035039レポート番号: ISAS-SUR29-S34
  • Yuki Sugiura, Kazuo Onuma, Masahiro Nagao, Koichi Momma, Yuki Kimura, Atsushi Yamazaki
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 122 1428 679 - 687 2014年08月 [査読有り][通常論文]
     
    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.
  • Hiromasa Niinomi, Hitoshi Miura, Yuki Kimura, Makio Uwaha, Hiroyasu Katsuno, Shunta Harada, Toru Ujihara, Katsuo Tsukamoto
    CRYSTAL GROWTH & DESIGN 14 7 3596 - 3602 2014年07月 [査読有り][通常論文]
     
    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.
  • Kenta Murayama, Katsuo Tsukamoto, Atul Srivastava, Hitoshi Miura, Etsuro Yokoyama, Yuki Kimura
    CRYSTAL RESEARCH AND TECHNOLOGY 49 5 315 - 322 2014年05月 [査読有り][通常論文]
     
    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.
  • Hiromasa Niinomi, Atsushi Horio, Shunta Harada, Toru Ujihara, Hitoshi Miura, Yuki Kimura, Katsuo Tsukamoto
    JOURNAL OF CRYSTAL GROWTH 394 106 - 111 2014年05月 [査読有り][通常論文]
     
    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.
  • Yuki Kimura, Hiromasa Niinomi, Katsuo Tsukamoto, Juan M. Garcia-Ruiz
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 136 5 1762 - 1765 2014年02月 [査読有り][通常論文]
     
    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.
  • Yuki Kimura, Hiromasa Niinomi, Katsuo Tsukamoto, Juan M. Garcia-Ruiz
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 136 5 1762 - 1765 2014年02月 [査読無し][通常論文]
     
    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.
  • 木村勇気, 田中今日子, 左近樹, 野沢貴也, 三浦均, 塚本勝男, 竹内伸介, 稲富裕光
    日本マイクログラビティ応用学会誌 31 3 130 - 136 日本マイクログラビティ応用学会 2014年 [査読有り][通常論文]
     
    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.
  • 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年 [査読有り][通常論文]
  • 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 2013年12月 [査読有り][通常論文]
     
    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.
  • 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 2013年12月 [査読有り][通常論文]
     
    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.
  • Yuki Kimura, Takeshi Sato, Norihiro Nakamura, Jun Nozawa, Tomoki Nakamura, Katsuo Tsukamoto, Kazuo Yamamoto
    Nature Communications 4 2649  2013年10月22日 [査読有り][通常論文]
     
    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.
  • T. Nakamura, T. Noguchi, Y. Kimura, T. Hiroi, I. Ahn, J. I. Lee, S. Sasaki
    METEORITICS & PLANETARY SCIENCE 48 A258 - A258 2013年07月 [査読有り][通常論文]
  • Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Katsuo Tsukamoto, Atsushi Yamazaki
    AMERICAN MINERALOGIST 98 1 262 - 270 2013年01月 [査読無し][通常論文]
     
    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.
  • Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Katsuo Tsukamoto, Atsushi Yamazaki
    AMERICAN MINERALOGIST 98 1 262 - 270 2013年01月 [査読無し][通常論文]
     
    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.
  • Tetsuya Hama, Kazuaki Kuwahata, Naoki Watanabe, Akira Kouchi, Yuki Kimura, Takeshi Chigai, Valerio Pirronello
    ASTROPHYSICAL JOURNAL 757 2 185 - 196 2012年10月 [査読無し][通常論文]
     
    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.
  • HAMA Tetsuya, KUWAHATA Kazuaki, WATANABE Naoki, KOUCHI Akira, KIMURA Yuki, CHIGAI Takeshi, PIRRONELLO Valerio
    Astrophys J 757 2,Pt.1 185,1-185,12  2012年10月01日 [査読無し][通常論文]
  • Tetsuya Hama, Kazuaki Kuwahata, Naoki Watanabe, Akira Kouchi, Yuki Kimura, Takeshi Chigai, Valerio Pirronello
    ASTROPHYSICAL JOURNAL 757 2 2012年10月 [査読有り][通常論文]
     
    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.
  • 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 39 2 68 - 74 2012年07月 [査読無し][通常論文]
  • Y. Kimura, K. K. Tanaka, H. Miura, K. Tsukamoto
    CRYSTAL GROWTH & DESIGN 12 6 3278 - 3284 2012年06月 [査読無し][通常論文]
     
    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.
  • A. Gucsik, K. Tsukamoto, H. Nishido, H. Miura, M. Kayama, K. Ninagawa, Y. Kimura
    JOURNAL OF LUMINESCENCE 132 4 1041 - 1047 2012年04月 [査読無し][通常論文]
     
    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.
  • Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto
    JOURNAL OF CRYSTAL GROWTH 332 1 58 - 67 2011年10月 [査読無し][通常論文]
     
    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.
  • Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto
    JOURNAL OF CRYSTAL GROWTH 332 1 58 - 67 2011年10月 [査読無し][通常論文]
     
    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.
  • Y. Kimura, K. K. Tanaka, H. Miura, K. Tsukamoto
    METEORITICS & PLANETARY SCIENCE 46 A124 - A124 2011年07月 [査読有り][通常論文]
  • 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 2011年06月 [査読有り][通常論文]
     
    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.
  • 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 2011年06月 [査読無し][通常論文]
     
    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.
  • 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 2011年06月 [査読無し][通常論文]
     
    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.
  • Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto, Chaorong Li, Takao Maki
    JOURNAL OF CRYSTAL GROWTH 316 1 196 - 200 2011年02月 [査読無し][通常論文]
     
    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.
  • Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto, Chaorong Li, Takao Maki
    JOURNAL OF CRYSTAL GROWTH 316 1 196 - 200 2011年02月 [査読無し][通常論文]
     
    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.
  • 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 2011年02月 [査読有り][通常論文]
     
    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.
  • Yuki Kimura, Joseph A. Nuth, Katsuo Tsukamoto, Chihiro Kaito
    METEORITICS & PLANETARY SCIENCE 46 1 92 - 102 2011年01月 [査読無し][通常論文]
     
    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年 [査読無し][通常論文]
  • Yuki Kimura, Joseph A. Nuth, Katsuo Tsukamoto, Chihiro Kaito
    METEORITICS & PLANETARY SCIENCE 46 1 92 - 102 2011年01月 [査読無し][通常論文]
     
    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.
  • Yuki Kimura, Joseph A. Nuth, Katsuo Tsukamoto, Chihiro Kaito
    METEORITICS & PLANETARY SCIENCE 46 1 92 - 102 2011年01月 [査読有り][通常論文]
     
    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.
  • WATANABE Naoki, KIMURA Yuki, KOUCHI Akira, CHIGAI Takeshi, HAMA Tetsuya, PIRRONELLO Valerio
    Astrophys J 714 2,Pt.2 L233-L237  2010年05月10日 [査読無し][通常論文]
  • Naoki Watanabe, Akira Kouchi, Hiroshi Hidaka, Yuki Kimura, Tetsuya Hama
    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 239 2010年03月 [査読有り][通常論文]
  • Joseph A. Nuth, Yuki Kimura, Christopher Lucas, Frank Ferguson, Natasha M. Johnson
    ASTROPHYSICAL JOURNAL LETTERS 710 1 L98 - L101 2010年02月 [査読無し][通常論文]
     
    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.
  • Joseph A. Nuth, Yuki Kimura, Christopher Lucas, Frank Ferguson, Natasha M. Johnson
    ASTROPHYSICAL JOURNAL LETTERS 710 1 L98 - L101 2010年02月 [査読無し][通常論文]
     
    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.
  • Midori Saito, Itsuki Sakon, Chihiro Kaito, Yuki Kimura
    EARTH PLANETS AND SPACE 62 1 81 - 90 2010年 [査読無し][通常論文]
     
    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.
  • N. Watanabe, Y. Kimura, A. Kouchi, T. Chigai, T. Hama, V. Pirronello
    The Astrophysical Journal Letters 714 L233-L237  2010年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • Midori Saito, Itsuki Sakon, Chihiro Kaito, Yuki Kimura
    EARTH PLANETS AND SPACE 62 1 81 - 90 2010年 [査読無し][通常論文]
     
    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.
  • Jun Nozawa, Katsuo Tsukamoto, Hidekazu Kobatake, Junya Yamada, Hisao Satoh, Ken Nagashima, Hitoshi Miura, Yuki Kimura
    ICARUS 204 2 681 - 686 2009年12月 [査読無し][通常論文]
     
    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.
  • Midori Saito, Yuki Kimura
    ASTROPHYSICAL JOURNAL LETTERS 703 2 L147 - L151 2009年10月 [査読無し][通常論文]
     
    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.
  • Yuki Kimura, Joseph A. Nuth
    ASTROPHYSICAL JOURNAL LETTERS 697 1 L10 - L13 2009年05月 [査読有り][通常論文]
     
    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.
  • 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 26 2 139 - 143 日本マイクログラビティ応用学会 2009年04月30日 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • Midori Saito, Yuki Kimura
    Astrophysical Journal 703 2 L147 - L151 2009年 [査読無し][通常論文]
     
    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.
  • 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 - + 2009年 
    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.
  • Y. Kimura, S. Sasaki, H. Suzuki, A. Kumamoto, M. Saito, C. Kaito
    ASTROPHYSICAL JOURNAL 684 2 1496 - 1501 2008年09月 [査読無し][通常論文]
     
    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.
  • 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年09月 [査読無し][通常論文]
     
    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.
  • 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年09月 [査読無し][通常論文]
     
    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.
  • Yuki Kimura, Chihiro Kaito
    ASTROPHYSICAL JOURNAL LETTERS 685 1 L83 - L86 2008年09月 [査読有り][通常論文]
     
    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.
  • Chihiro Kaito, Yasuhiko Kinuta, Hitoshi Suzuki, Syunsuke Adachi, Akihito Kumamoto, Yoshio Saito, Yuki Kimura
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 9 2008年09月 [査読有り][通常論文]
     
    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.
  • Kenji Nina, Yuki Kimura, Kaorl Yokoyama, Osamu Kido, Gong Binyo, Chihiro Kaito
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 40 9 2995 - 2998 2008年08月 [査読無し][通常論文]
     
    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.
  • 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年08月 [査読無し][通常論文]
     
    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.
  • 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年08月 [査読無し][通常論文]
     
    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.
  • Y. Kimura, C. Kaito, J. A. Nuth
    METEORITICS & PLANETARY SCIENCE 43 7 A76 - A76 2008年07月 [査読有り][通常論文]
  • Yuki Kimura, Yu Miyazaki, Akihito Kumamoto, Midori Saito, Chihiro Kaito
    ASTROPHYSICAL JOURNAL LETTERS 680 1 L89 - L92 2008年06月 [査読無し][通常論文]
     
    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.
  • Yuki Kimura, Chihiro Kaito
    SURFACE & COATINGS TECHNOLOGY 202 17 4159 - 4162 2008年05月 [査読無し][通常論文]
     
    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.
  • Frans J. M. Rietmeijer, Aurora Pun, Yuki Kimura, Joseph A. Nuth
    ICARUS 195 1 493 - 503 2008年05月 [査読無し][通常論文]
     
    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.
  • Frans J. M. Rietmeijer, Aurora Pun, Yuki Kimura, Joseph A. Nuth
    ICARUS 195 1 493 - 503 2008年05月 [査読有り][通常論文]
     
    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.
  • 木村勇気
    日本惑星科学会誌 遊・星・人 17 1 62 - 68 日本惑星科学会 2008年03月25日 [査読無し][通常論文]
     
    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年 [査読無し][通常論文]
  • Y. Kimura, C. Kaito
    The Astrophysical Journal Letters 685 83 - 86 2008年 [査読無し][通常論文]
  • Kumamoto A, Kimura Y, Kaito C, Wada S
    IAU Symposium Proceedings Series 4 433 - 434 2008年 [査読有り][通常論文]
  • 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年12月 [査読無し][通常論文]
     
    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.
  • C. Kaito, Y. Miyazaki, A. Kumamoto, Y. Kimura
    The Astrophysical Journal Letters, 666 1 L57 - L60 2007年09月 [査読無し][通常論文]
     
    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.
  • Yuki Kimura, Joseph A. Nuth
    ASTROPHYSICAL JOURNAL 664 2 1253 - 1263 2007年08月 [査読無し][通常論文]
     
    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.
  • Yuki Kimura, Joseph A. Nuth, Subrata Chakpaborty, Mark H. Thiemens
    METEORITICS & PLANETARY SCIENCE 42 7-8 1429 - 1439 2007年07月 [査読無し][通常論文]
     
    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.
  • 木村勇気, 墻内千尋
    日本結晶成長学会誌 34 2 89 - 93 2007年07月 [査読無し][通常論文]
  • 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年01月01日 [査読無し][通常論文]
     
    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.
  • Akihito Kumamoto, Mami Kurumada, Yuki Kimura, Chihiro Kaito
    Advances in Geosciences: Volume 7: Planetary Science (PS) 7 93 - 99 2007年01月01日 [査読無し][通常論文]
     
    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年 [査読無し][通常論文]
  • H. Suzuki, H. Shingu, S. Morikawa, S. Ohyagi, Y. Kimura, M. Shintaku, A. Kumamoto, C. Kaito
    ECS Transactions 5 1 79 - 87 2007年 
    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.
  • Y. Kimura, J. A. Nuth
    METEORITICS & PLANETARY SCIENCE 41 8 A95 - A95 2006年08月 [査読有り][通常論文]
  • C. Kaito, S. Sasaki, Y. Miyazaki, M. Kurumada, A. Kumamoto, H. Suzuki, Y. Kimura, C. Koike
    METEORITICS & PLANETARY SCIENCE 41 8 A91 - A91 2006年08月 [査読有り][通常論文]
  • 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年05月 [査読無し][通常論文]
     
    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.
  • 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年05月 [査読無し][通常論文]
     
    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.
  • Yuki Kimura, Joseph A. Nuth, Frank T. Ferguson
    METEORITICS & PLANETARY SCIENCE 41 5 673 - 680 2006年05月 [査読無し][通常論文]
     
    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.
  • 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年03月 [査読無し][通常論文]
     
    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.
  • K. Yokoyama, Y. Kimura, O. Kido, M. Kurumada, A. Kumamoto, C. Kaito
    Advances in Geosciences 7 115 - 123 2006年 [査読無し][通常論文]
  • Y Kimura, M Kurumada, K Tamura, C Koike, H Chihara, C Kaito
    ASTRONOMY & ASTROPHYSICS 442 2 507 - 512 2005年11月 [査読無し][通常論文]
     
    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.
  • Y. Kimura, Joseph A. Nuth III, Frank T. Ferguson
    The Astrophysical Journal Letters 632 2 L159 - L162 2005年10月 [査読無し][通常論文]
     
    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.
  • Y Kimura, JA Nuth, FT Ferguson
    ASTROPHYSICAL JOURNAL 632 2 L159 - L162 2005年10月 [査読有り][通常論文]
     
    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.
  • Y Kimura, K Tamura, C Koike, H Chihara, C Kaito
    ICARUS 177 1 280 - 285 2005年09月 [査読無し][通常論文]
     
    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.
  • Y Kimura, JA Nuth
    ASTROPHYSICAL JOURNAL 630 1 637 - 641 2005年09月 [査読有り][通常論文]
     
    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.
  • Y Kimura, C Kaito
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 28 3 281 - 285 2005年08月 [査読無し][通常論文]
     
    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.
  • 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年07月 [査読無し][通常論文]
     
    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.
  • A. Kouchi, H. Nakano, Y. Kimura, C. Kaito
    Astrophysical Journal 626 2 L129 - L132 2005年06月20日 [査読無し][通常論文]
     
    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.
  • Y Kimura, T Sato, C Kaito
    CARBON 43 7 1570 - 1574 2005年06月 [査読無し][通常論文]
  • Y Kimura, C Kaito
    THIN SOLID FILMS 476 1 65 - 67 2005年04月 [査読無し][通常論文]
     
    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.
  • Y. Kimura, M. Ishikawa, M. Kurumada, T. Tanigaki, H. Suzuki, C. Kaito
    JOURNAL OF CRYSTAL GROWTH 275 1-2 E977 - E981 2005年02月 [査読無し][通常論文]
     
    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.
  • 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年02月 [査読無し][通常論文]
     
    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.
  • 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年02月 [査読無し][通常論文]
     
    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.
  • 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年02月 [査読無し][通常論文]
     
    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.
  • Y. Kimura, J. A. Nuth III
    The Astrophysical Journal 630 637 - 641 2005年 [査読無し][通常論文]
  • K Kamitsuji, H Suzuki, Y Kimura, T Sato, Y Saito, C Kaito
    ASTRONOMY & ASTROPHYSICS 429 1 205 - 208 2005年01月 [査読無し][通常論文]
     
    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.
  • O Kido, H Suzuki, Y Kimura, T Sato, Y Saito, C Kaito
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 25 4 619 - 624 2005年01月 [査読無し][通常論文]
     
    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.
  • 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年 [査読無し][通常論文]
     
    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.
  • 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年08月 [査読無し][通常論文]
     
    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.
  • 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年07月 [査読無し][通常論文]
     
    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.
  • 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年07月 [査読無し][通常論文]
     
    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.
  • 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年07月 [査読有り][通常論文]
     
    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.
  • 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年07月 [査読有り][通常論文]
     
    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.
  • Y Kimura, A Ikegami, M Kurumada, K Kamitsuji, C Kaito
    ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 152 2 297 - 301 2004年06月 [査読無し][通常論文]
     
    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.
  • M Kurumada, Y Kimura, H Suzuki, O Kido, Y Saito, C Kaito
    SCRIPTA MATERIALIA 50 11 1413 - 1416 2004年06月 [査読無し][通常論文]
     
    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.
  • 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年06月 [査読無し][通常論文]
     
    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.
  • Y Kimura, A Ikegami, M Kurumada, K Kamitsuji, C Kaito
    ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 152 2 297 - 301 2004年06月 [査読有り][通常論文]
     
    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.
  • T Tanigaki, Y Kimura, H Suzuki, M Kurumada, C Kaito
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 5 1375 - 1376 2004年05月 [査読無し][通常論文]
  • 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年04月 [査読無し][通常論文]
     
    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.
  • 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年04月 [査読有り][通常論文]
     
    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.
  • Y Kimura, T Sato, C Kaito
    CARBON 42 1 33 - 38 2004年 [査読無し][通常論文]
     
    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.
  • T Tanigaki, Y Kimura, H Suzuki, C Kaito
    JOURNAL OF CRYSTAL GROWTH 260 3-4 298 - 303 2004年01月 [査読無し][通常論文]
     
    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.
  • Y Ishikawa, O Kido, Y Kimura, M Kurumada, H Suzuki, Y Saito, C Kaito
    SURFACE SCIENCE 548 1-3 276 - 280 2004年01月 [査読無し][通常論文]
     
    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.
  • T Sato, O Kido, M Kurumada, Y Kimura, H Suzuki, Y Saito, C Kaito
    CARBON 42 8-9 1875 - 1877 2004年 [査読無し][通常論文]
  • 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年12月 [査読無し][通常論文]
     
    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.
  • Y Kimura, C Kaito
    ASTRONOMY & ASTROPHYSICS 409 1 159 - 161 2003年10月 [査読無し][通常論文]
     
    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.
  • T Tanigaki, H Suzuki, Y Kimura, O Kido, Y Saito, C Kaito
    JOURNAL OF CRYSTAL GROWTH 256 3-4 317 - 323 2003年09月 [査読無し][通常論文]
     
    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.
  • 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年09月 [査読無し][通常論文]
     
    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.
  • Y. Kimura, C. Kaito
    Monthly Notices of the Royal Astronomical Society 343 2 385 - 389 2003年08月01日 [査読無し][通常論文]
     
    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.
  • Y Kimura, C Kaito
    JOURNAL OF CRYSTAL GROWTH 255 3-4 282 - 285 2003年08月 [査読無し][通常論文]
     
    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.
  • 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年08月 [査読無し][通常論文]
     
    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.
  • 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年08月 [査読無し][通常論文]
     
    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.
  • 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年08月 [査読無し][通常論文]
     
    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.
  • 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年08月 [査読有り][通常論文]
     
    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.
  • 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年06月 [査読無し][通常論文]
     
    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.
  • Y Kimura, C Kaito
    JOURNAL OF CRYSTAL GROWTH 250 3-4 450 - 457 2003年04月 [査読無し][通常論文]
     
    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.
  • 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年04月 [査読無し][通常論文]
     
    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.
  • T Tanigaki, H Suzuki, Y Kimura, C Kaito, Y Saito
    SURFACE REVIEW AND LETTERS 10 2-3 455 - 459 2003年04月 [査読無し][通常論文]
     
    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.
  • M Kurumada, H Suzuki, Y Kimura, Y Saito, C Kaito
    JOURNAL OF CRYSTAL GROWTH 250 3-4 444 - 449 2003年04月 [査読無し][通常論文]
     
    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.
  • 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年04月 [査読有り][通常論文]
     
    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.
  • T Chigai, T Yamamoto, C Kaito, Y Kimura
    ASTROPHYSICAL JOURNAL 587 2 771 - 776 2003年04月 [査読有り][通常論文]
     
    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.
  • Y Kimura, Y Saito, C Kaito
    SURFACE SCIENCE 527 1-3 L219 - L221 2003年03月 [査読無し][通常論文]
     
    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.
  • 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年02月 [査読無し][通常論文]
     
    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.
  • C Kaito, Y Kimura, S Tominaga, S Kimura, T Nakada, Y Saito
    PHYSICS OF LOW-DIMENSIONAL STRUCTURES 5-6 1 - 7 2003年 [査読無し][通常論文]
     
    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.
  • T. Chigai, T. Yamamoto, C. Kaito, Y. Kimura
    The Astrophysical Journal 587 2 771 - 776 2003年 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
     
    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年 [査読無し][通常論文]
  • 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年11月 [査読無し][通常論文]
     
    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.
  • H Suzuki, N Fukuzawa, T Tanigaki, T Sato, O Kido, Y Kimura, C Kaito
    JOURNAL OF CRYSTAL GROWTH 244 2 168 - 172 2002年10月 [査読無し][通常論文]
     
    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.
  • 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年08月 [査読無し][通常論文]
     
    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.
  • T Kobayashi, Y Kimura, H Suzuki, T Sato, T Tanigaki, Y Saito, C Kaito
    JOURNAL OF CRYSTAL GROWTH 243 1 143 - 150 2002年08月 [査読無し][通常論文]
     
    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 183 - 186 宇宙科学研究所 2002年08月 [査読無し][通常論文]
  • M Sasaki, K Hanamoto, Y Kimura, C Kaito, H Miki, Y Nakayama
    REVIEW OF SCIENTIFIC INSTRUMENTS 73 3 1384 - 1386 2002年03月 [査読無し][通常論文]
     
    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.
  • Y Kimura, Y Saito, T Nakada, C Kaito
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 13 1 11 - 23 2002年01月 [査読無し][通常論文]
     
    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.
  • Y Kimura, C Kaito, K Hanamoto, M Sasaki, S Kimura, T Nakada, Y Saito, Y Nakayama
    CARBON 40 7 1043 - 1050 2002年 [査読無し][通常論文]
     
    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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
     
    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.
  • H Suzuki, T Tanigaki, T Sato, O Kido, Y Atou, Y Kimura, C Kaito
    PHYSICS OF LOW-DIMENSIONAL STRUCTURES 7-8 99 - 105 2002年 [査読無し][通常論文]
     
    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.
  • Y Kimura, C Kaito, K Hanamoto, M Sasaki, S Kimura, T Nakada, Y Saito, Y Nakayama
    CARBON 40 7 1043 - 1050 2002年 [査読有り][通常論文]
     
    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.
  • 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 2002年 [査読有り][通常論文]
     
    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.
  • 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年07月 [査読無し][通常論文]
     
    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.
  • 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年07月 [査読無し][通常論文]
     
    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.
  • 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年07月 [査読無し][通常論文]
     
    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.
  • C Kaito, A Ito, S Kimura, Y Kimura, Y Saito, T Nakada
    JOURNAL OF CRYSTAL GROWTH 218 2-4 259 - 264 2000年09月 [査読無し][通常論文]
     
    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.
  • T Nakao, T Nakada, Y Nakayama, K Miyatani, Y Kimura, Y Saito, C Kaito
    THIN SOLID FILMS 370 1-2 155 - 162 2000年07月 [査読無し][通常論文]
     
    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.
  • Y Kimura, Y Saito, T Nakada, C Kaito
    PHYSICS OF LOW-DIMENSIONAL STRUCTURES 1-2 L1 - L7 2000年 [査読無し][通常論文]
     
    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.
  • C Kaito, H Nakamura, S Kimura, Y Kimura, T Nakada, Y Saito
    THIN SOLID FILMS 359 2 283 - 287 2000年01月 [査読無し][通常論文]
     
    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.
  • C Kaito, H Nakamura, S Kimura, Y Kimura, T Nakada, Y Saito
    THIN SOLID FILMS 359 2 283 - 287 2000年01月 [査読有り][通常論文]
     
    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.
  • C Kaito, T Nakao, Y Ato, Y Kimura, S Kimura, T Nakada, Y Saito
    PHYSICS OF LOW-DIMENSIONAL STRUCTURES 12 53 - 60 1999年 [査読無し][通常論文]
     
    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.
  • Y KIMURA, A IKEGAMI
    JOURNAL OF MEMBRANE BIOLOGY 85 3 225 - 231 1985年 [査読有り][通常論文]

MISC

  • 中村 智樹, 天野 香菜, 松岡 萌, 黒澤 耕介, 二宮 和彦, 大澤 崇人, 木村 勇気, 玄田 英典, 田中 智, はやぶさ2初期分析「石」チーム 遊・星・人 = Planetary people : 日本惑星科学会誌 32 (3) 226 -235 2023年09月 
    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．
  • 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年
  • 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年01月 
    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
  • 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年
  • 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年
  • 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年
  • 木村 勇気, 香内 晃, 山﨑 智也, 佐藤 陽亮, 齋藤 史明, 稲富 裕光, 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年01月 
    第34回宇宙環境利用シンポジウム (2020年1月21日-22日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)), 相模原市, 神奈川県資料番号: SA6000145005
  • 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年
  • 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年
  • 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年
  • 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年
  • 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年
  • 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年
  • 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年
  • 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年
  • 木村 勇気, 石塚 紳之介, Sturm Saso, 田中 今日子, 山﨑 智也, 齋藤 史明, 佐藤 陽亮, 稲富 裕光, 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年01月 
    第31回宇宙環境利用シンポジウム (2017年1月16日-17日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)), 相模原市, 神奈川県資料番号: SA6000061013レポート番号: SUS31-M06
  • 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年09月
  • 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年
  • 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年
  • 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年
  • 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年
  • 木村 勇気, 石塚 紳之介, 中坪 俊一, 齋藤 史明, 山﨑 智也, 左近 樹, 竹内 伸介, 稲富 裕光, 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年01月 
    第16回宇宙科学シンポジウム (2016年1月6日-7日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県資料番号: SA6000046242レポート番号: S4-005
  • 木村 勇気, 石塚 紳之介, 中坪 俊一, 齋藤 史明, 山﨑 智也, 左近 樹, 竹内 伸介, 稲富 裕光, 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年01月 
    第30回宇宙環境利用シンポジウム (2016年1月19日-20日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)), 相模原市, 神奈川県資料番号: SA6000048035レポート番号: G-31
  • 木村 勇気, 田中 今日子, 本田 充彦, 左近 樹, 三浦 均, 下西 隆, 瀧川 晶, 上塚 貴史, 野沢 貴也 日本惑星科学会誌遊星人 25 (1) 21 -23 2016年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 木村 勇気, 石塚 紳之介, 中坪 俊一, 齋藤 史明, 山﨑 智也, 左近 樹, 竹内 伸介, 稲富 裕光, 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年11月 
    大気球シンポジウム 平成27年度（2015年11月5-6日. 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)）, 相模原市, 神奈川県資料番号: SA6000044010レポート番号: isas15-sbs-010
  • 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年08月 [査読無し][通常論文]
  • 本田 充彦, 左近 樹, 木村 勇気, 三浦 均, 下西 隆, 瀧川 晶, 田中 今日子, 上塚 貴史 遊・星・人 : 日本惑星科学会誌 24 (1) 60 -62 2015年03月
  • 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年
  • 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年
  • 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年
  • 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年 [査読無し][通常論文]
  • 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年09月10日
  • 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年09月10日
  • 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年03月11日 [査読無し][通常論文]
  • 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年
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Katsuo Tsukamoto, Atsushi Yamazaki AMERICAN MINERALOGIST 98 (1) 262 -270 2013年01月 [査読無し][通常論文]
     
    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.
  • 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 JASMA : Journal of the Japan Society of Microgravity Application 29 (4) 184 -189 2012年10月31日 [査読無し][通常論文]
  • 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年10月24日 [査読無し][通常論文]
  • Tetsuya Hama, Kazuaki Kuwahata, Naoki Watanabe, Akira Kouchi, Yuki Kimura, Takeshi Chigai, Valerio Pirronello ASTROPHYSICAL JOURNAL 757 (2) 185 -196 2012年10月 [査読無し][通常論文]
     
    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.
  • Y. Kimura, K. K. Tanaka, H. Miura, K. Tsukamoto CRYSTAL GROWTH & DESIGN 12 (6) 3278 -3284 2012年06月 [査読無し][通常論文]
     
    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.
  • A. Gucsik, K. Tsukamoto, H. Nishido, H. Miura, M. Kayama, K. Ninagawa, Y. Kimura JOURNAL OF LUMINESCENCE 132 (4) 1041 -1047 2012年04月 [査読無し][通常論文]
     
    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.
  • 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年03月 [査読無し][通常論文]
  • 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年
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto JOURNAL OF CRYSTAL GROWTH 332 (1) 58 -67 2011年10月 [査読無し][通常論文]
     
    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.
  • 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 66 (2) 909 -909 2011年08月24日 [査読無し][通常論文]
  • 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年08月22日 [査読無し][通常論文]
  • A. Gucsik, K. Tsukamoto, Y. Kimura, H. Miura, H. Nishido, M. Kayama, K. Ninagawa, Y. Endo METEORITICS & PLANETARY SCIENCE 46 A84 -A84 2011年07月 [査読無し][通常論文]
  • 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 66 (1) 220 -220 2011年03月03日
  • 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年03月 [査読無し][通常論文]
  • Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto, Chaorong Li, Takao Maki JOURNAL OF CRYSTAL GROWTH 316 (1) 196 -200 2011年02月 [査読無し][通常論文]
     
    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.
  • Yuki Kimura, Yuko Inatomi, Hitoshi Miura, Takao Maki, Katsuo Tsukamoto ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES 67 C117 -C117 2011年
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • Interferometric observation of temperature distributions in the smoke experiment
    Y. Kimura, K. Tsukamoto J. Jpn. Soc. Microgravity Appl 2011年 [査読無し][通常論文]
  • 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年10月07日 [査読無し][通常論文]
  • 木村勇気, 塚本勝男 日本物理学会講演概要集 65 (2) 330 2010年08月18日 [査読無し][通常論文]
  • 木村 勇気, 塚本 勝男 日本物理学会講演概要集 65 (2) 330 -330 2010年08月18日 [査読無し][通常論文]
  • 木村 勇気, 塚本 勝男 日本物理学会講演概要集 65 (2) 867 -867 2010年08月18日 [査読無し][通常論文]
  • Y. Kimura, K. Tsukamoto, T. Maki METEORITICS & PLANETARY SCIENCE 45 A104 -A104 2010年07月 [査読無し][通常論文]
  • Naoki Watanabe, Yuki Kimura, Akira Kouchi, Takeshi Chigai, Tetsuya Hama, Valerio Pirronello ASTROPHYSICAL JOURNAL LETTERS 714 (2) L233 -L237 2010年05月 [査読無し][通常論文]
     
    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.
  • Joseph A. Nuth, Yuki Kimura, Christopher Lucas, Frank Ferguson, Natasha M. Johnson ASTROPHYSICAL JOURNAL LETTERS 710 (1) L98 -L101 2010年02月 [査読無し][通常論文]
     
    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.
  • Midori Saito, Itsuki Sakon, Chihiro Kaito, Yuki Kimura EARTH PLANETS AND SPACE 62 (1) 81 -90 2010年 [査読無し][通常論文]
     
    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.
  • Y. Kimura, J. A. Nuth III, C. Kaito Meteoritics & Planetary Science 46 92 -102 2010年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • Jun Nozawa, Katsuo Tsukamoto, Hidekazu Kobatake, Junya Yamada, Hisao Satoh, Ken Nagashima, Hitoshi Miura, Yuki Kimura ICARUS 204 (2) 681 -686 2009年12月 [査読無し][通常論文]
     
    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.
  • Midori Saito, Yuki Kimura ASTROPHYSICAL JOURNAL LETTERS 703 (2) L147 -L151 2009年10月 [査読無し][通常論文]
     
    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.
  • 渡部 直樹, 香内 晃, 木村 勇気 日本物理学会講演概要集 64 (2) 96 -96 2009年08月18日
  • 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年08月18日 [査読無し][通常論文]
  • 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年08月18日 [査読無し][通常論文]
  • 野澤純, 塚本勝男, 甲野藤真, 木村勇気 結晶成長国内会議予稿集 39th 186 2009年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • M. Saito, Y. Kimura The Astrophysical Journal Letters 703 L147-L151 2009年 [査読無し][通常論文]
  • Y. Kimura, S. Sasaki, H. Suzuki, A. Kumamoto, M. Saito, C. Kaito ASTROPHYSICAL JOURNAL 684 (2) 1496 -1501 2008年09月 [査読無し][通常論文]
     
    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.
  • 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年09月 [査読無し][通常論文]
     
    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.
  • Kenji Nina, Yuki Kimura, Kaorl Yokoyama, Osamu Kido, Gong Binyo, Chihiro Kaito PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 40 (9) 2995 -2998 2008年08月 [査読無し][通常論文]
     
    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.
  • 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年08月 [査読無し][通常論文]
     
    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.
  • Yuki Kimura, Yu Miyazaki, Akihito Kumamoto, Midori Saito, Chihiro Kaito ASTROPHYSICAL JOURNAL LETTERS 680 (1) L89 -L92 2008年06月 [査読無し][通常論文]
     
    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.
  • Frans J. M. Rietmeijer, Aurora Pun, Yuki Kimura, Joseph A. Nuth ICARUS 195 (1) 493 -503 2008年05月 [査読無し][通常論文]
     
    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年 [査読無し][通常論文]
  • Y. Kimura, C. Kaito Surface and Coatings Technology 202 4159 -4162 2008年 [査読無し][通常論文]
  • Y. Kimura, C. Kaito The Astrophysical Journal Letters 685 83 -86 2008年 [査読無し][通常論文]
  • 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年12月 [査読無し][通常論文]
     
    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.
  • Yuki Kimura, Joseph A. Nuth ASTROPHYSICAL JOURNAL 664 (2) 1253 -1263 2007年08月 [査読無し][通常論文]
     
    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.
  • Yuki Kimura, Joseph A. Nuth, Subrata Chakpaborty, Mark H. Thiemens METEORITICS & PLANETARY SCIENCE 42 (7-8) 1429 -1439 2007年07月 [査読無し][通常論文]
     
    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.
  • 木村 勇気, 墻内 千尋 日本物理学会講演概要集 62 (1) 889 -889 2007年02月28日
  • 弥永 英臣, 熊本 明仁, 新宅 正行, 木村 勇気, 墻内 千尋 日本物理学会講演概要集 62 (1) 889 -889 2007年02月28日
  • 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年 [査読無し][通常論文]
  • Chihiro Kaito, Yu Miyazaki, Akihito Kumamoto, Yuki Kimura Astrophysical Journal 666 (1) L57 -L60 2007年 [査読無し][通常論文]
     
    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.
  • 熊本 明仁, 新宅 正行, 車田 真実, 城戸 修, 木村 勇気, 墻内 千尋 日本結晶成長学会誌 33 (4) 312 -312 2006年11月30日 
    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.
  • 木村 勇気, NUTH Joseph A. III, CHAKRABORTY Subrata, THIEMENS Mark H. 日本結晶成長学会誌 33 (4) 315 -315 2006年11月30日 
    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.
  • 足立 俊輔, 熊本 明仁, 新宅 正行, 木村 勇気, 衣田 康彦, 墻内 千尋 日本結晶成長学会誌 33 (4) 311 -311 2006年11月30日 
    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.
  • 新宅 正行, 鈴木 仁志, 木村 勇気, 城戸 修, 車田 真実, 齋藤 嘉夫, 墻内 千尋 日本物理学会講演概要集 61 (2) 738 -738 2006年08月18日
  • 木村 勇気, Nuth III Joseph A. 日本物理学会講演概要集 61 (2) 739 -739 2006年08月18日
  • 車田 真実, 齊藤 碧, 木村 勇気, 墻内 千尋 日本物理学会講演概要集 61 (2) 740 -740 2006年08月18日
  • 足立 俊輔, 木村 勇気, 衣田 康彦, 墻内 千尋 日本物理学会講演概要集 61 (2) 738 -738 2006年08月18日
  • 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年05月 [査読無し][通常論文]
     
    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.
  • 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年05月 [査読無し][通常論文]
     
    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.
  • Yuki Kimura, Joseph A. Nuth, Frank T. Ferguson METEORITICS & PLANETARY SCIENCE 41 (5) 673 -680 2006年05月 [査読無し][通常論文]
     
    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.
  • 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年03月 [査読無し][通常論文]
     
    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.
  • 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年 [査読無し][通常論文]
  • K. Yokoyama, Y. Kimura, O. Kido, M. Kurumada, A. Kumamoto, C. Kaito Advances in Geosciences 7 115 -123 2006年 [査読無し][通常論文]
  • A. Kumamoto, M. Kurumada, Y. Kimura, C. Kaito Advances in Geosciences 7 93 -99 2006年 [査読無し][通常論文]
  • Y Kimura, M Kurumada, K Tamura, C Koike, H Chihara, C Kaito ASTRONOMY & ASTROPHYSICS 442 (2) 507 -512 2005年11月 [査読無し][通常論文]
     
    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.
  • Y Kimura, JA Nuth, FT Ferguson ASTROPHYSICAL JOURNAL 632 (2) L159 -L162 2005年10月 [査読無し][通常論文]
     
    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.
  • Y Kimura, K Tamura, C Koike, H Chihara, C Kaito ICARUS 177 (1) 280 -285 2005年09月 [査読無し][通常論文]
     
    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.
  • Y Kimura, JA Nuth ASTROPHYSICAL JOURNAL 630 (1) 637 -641 2005年09月 [査読無し][通常論文]
     
    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.
  • Y Kimura, C Kaito PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 28 (3) 281 -285 2005年08月 [査読無し][通常論文]
     
    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.
  • 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年07月 [査読無し][通常論文]
     
    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.
  • Y Kimura, T Sato, C Kaito CARBON 43 (7) 1570 -1574 2005年06月 [査読無し][通常論文]
  • A Kouchi, H Nakano, Y Kimura, C Kaito ASTROPHYSICAL JOURNAL 626 (2) L129 -L132 2005年06月 [査読無し][通常論文]
     
    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.
  • Y Kimura, C Kaito THIN SOLID FILMS 476 (1) 65 -67 2005年04月 [査読無し][通常論文]
     
    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.
  • Y. Kimura, M. Ishikawa, M. Kurumada, T. Tanigaki, H. Suzuki, C. Kaito JOURNAL OF CRYSTAL GROWTH 275 (1-2) E977 -E981 2005年02月 [査読無し][通常論文]
     
    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.
  • 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年02月 [査読無し][通常論文]
     
    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.
  • 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年02月 [査読無し][通常論文]
     
    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.
  • 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年02月 [査読無し][通常論文]
     
    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.
  • K Kamitsuji, H Suzuki, Y Kimura, T Sato, Y Saito, C Kaito ASTRONOMY & ASTROPHYSICS 429 (1) 205 -208 2005年01月 [査読無し][通常論文]
     
    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.
  • O Kido, H Suzuki, Y Kimura, T Sato, Y Saito, C Kaito PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 25 (4) 619 -624 2005年01月 [査読無し][通常論文]
     
    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.
  • 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年 [査読無し][通常論文]
     
    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.
  • 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年08月 [査読無し][通常論文]
     
    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.
  • 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年07月 [査読無し][通常論文]
     
    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.
  • 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年07月 [査読無し][通常論文]
     
    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.
  • Y Kimura, A Ikegami, M Kurumada, K Kamitsuji, C Kaito ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 152 (2) 297 -301 2004年06月 [査読無し][通常論文]
     
    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.
  • M Kurumada, Y Kimura, H Suzuki, O Kido, Y Saito, C Kaito SCRIPTA MATERIALIA 50 (11) 1413 -1416 2004年06月 [査読無し][通常論文]
     
    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.
  • 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年06月 [査読無し][通常論文]
     
    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.
  • T Tanigaki, Y Kimura, H Suzuki, M Kurumada, C Kaito JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 (5) 1375 -1376 2004年05月 [査読無し][通常論文]
  • 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年04月 [査読無し][通常論文]
     
    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.
  • 木村 勇気, 佐藤 岳志, 鈴木 仁志, 墻内 千尋 日本物理学会講演概要集 59 (1) 920 -920 2004年03月03日
  • 車田 真実, 城戸 修, 上辻 勝也, 木村 勇気, 佐藤 岳志, 鈴木 仁志, 齋藤 嘉夫, 墻内 千尋 日本物理学会講演概要集 59 (1) 921 -921 2004年03月03日
  • 上辻 勝也, 佐藤 岳志, 木村 勇気, 鈴木 仁志, 齋藤 嘉夫, 墻内 千尋 日本物理学会講演概要集 59 (1) 921 -921 2004年03月03日
  • 城戸 修, 鈴木 仁志, 上辻 勝也, 車田 真実, 佐藤 岳志, 木村 勇気, 齋藤 嘉夫, 墻内 千尋 日本物理学会講演概要集 59 (1) 920 -920 2004年03月03日
  • 衣田 康彦, 鈴木 仁志, 小玉 詳, 車田 真実, 城戸 修, 谷垣 俊明, 木村 勇気, 齋藤 嘉夫, 墻内 千尋 日本物理学会講演概要集 59 (1) 920 -920 2004年03月03日
  • 新宅 正行, 鈴木 仁志, 木村 勇気, 谷垣 俊明, 城戸 修, 佐藤 岳志, 齋藤 嘉夫, 墻内 千尋 日本物理学会講演概要集 59 (1) 921 -921 2004年03月03日
  • Y Kimura, T Sato, C Kaito CARBON 42 (1) 33 -38 2004年 [査読無し][通常論文]
     
    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.
  • T Tanigaki, Y Kimura, H Suzuki, C Kaito JOURNAL OF CRYSTAL GROWTH 260 (3-4) 298 -303 2004年01月 [査読無し][通常論文]
     
    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.
  • Y Ishikawa, O Kido, Y Kimura, M Kurumada, H Suzuki, Y Saito, C Kaito SURFACE SCIENCE 548 (1-3) 276 -280 2004年01月 [査読無し][通常論文]
     
    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.
  • T Sato, O Kido, M Kurumada, Y Kimura, H Suzuki, Y Saito, C Kaito CARBON 42 (8-9) 1875 -1877 2004年 [査読無し][通常論文]
  • 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年12月 [査読無し][通常論文]
     
    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.
  • 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年09月28日 [査読無し][通常論文]
  • 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年09月28日 [査読無し][通常論文]
  • T Tanigaki, H Suzuki, Y Kimura, O Kido, Y Saito, C Kaito JOURNAL OF CRYSTAL GROWTH 256 (3-4) 317 -323 2003年09月 [査読無し][通常論文]
     
    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.
  • 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年09月 [査読無し][通常論文]
     
    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.
  • 新宅 正行, 鈴木 仁志, 木村 勇気, 佐藤 岳志, 城戸 修, 墻内 千尋 日本物理学会講演概要集 58 (2) 767 -767 2003年08月15日
  • 城戸 修, 鈴木 仁志, 中島 康子, 上辻 勝也, 池上 亜紀美, 車田 真実, 佐藤 岳志, 木村 勇気, 齋藤 嘉夫, 墻内 千尋 日本物理学会講演概要集 58 (2) 767 -767 2003年08月15日
  • 小玉 群, 鈴木 仁志, 城戸 修, 上辻 勝也, 車田 真実, 谷垣 俊明, 木村 勇気, 齋藤 嘉夫, 墻内 千尋 日本物理学会講演概要集 58 (2) 768 -768 2003年08月15日
  • 陸 亨, 佐藤 岳志, 鈴木 仁志, 城戸 修, 車田 真実, 木村 勇気, 齋藤 嘉夫, 墻内 千尋 日本物理学会講演概要集 58 (2) 768 -768 2003年08月15日
  • Y Kimura, C Kaito MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 343 (2) 385 -389 2003年08月 [査読無し][通常論文]
     
    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.
  • 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年08月 [査読無し][通常論文]
     
    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.
  • 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年08月 [査読無し][通常論文]
     
    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.
  • 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年08月 [査読無し][通常論文]
     
    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.
  • 木村 勇気, 谷垣 俊明, 鈴木 仁志, 佐藤 岳志, 墻内 千尋 日本結晶成長学会誌 30 (3) 16 -16 2003年07月05日 
    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.
  • 車田 真実, 木村 勇気, 鈴木 仁志, 城戸 修, 齋藤 嘉夫, 墻内 千尋 日本結晶成長学会誌 30 (3) 40 -40 2003年07月05日 
    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.
  • 上辻 勝也, 鈴木 仁志, 木村 勇気, 齋藤 嘉夫, 墻内 千尋 日本結晶成長学会誌 30 (3) 34 -34 2003年07月05日 
    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.
  • 佐々木 晋一, 木村 勇気, 齋藤 嘉夫, 竹田 篤, 墻内 千尋 日本結晶成長学会誌 30 (3) 35 -35 2003年07月05日 
    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℃.
  • 鈴木 仁志, 佐藤 岳志, 木村 勇気, 齋藤 嘉夫, 墻内 千尋 日本結晶成長学会誌 30 (3) 36 -36 2003年07月05日 
    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.
  • 池上 亜紀美, 木村 勇気, 鈴木 仁志, 齋藤 嘉夫, 墻内 千尋 日本結晶成長学会誌 30 (3) 41 -41 2003年07月05日 
    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.
  • 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年06月 [査読無し][通常論文]
     
    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.
  • 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年04月 [査読無し][通常論文]
     
    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.
  • T Tanigaki, H Suzuki, Y Kimura, C Kaito, Y Saito SURFACE REVIEW AND LETTERS 10 (2-3) 455 -459 2003年04月 [査読無し][通常論文]
     
    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.
  • M Kurumada, H Suzuki, Y Kimura, Y Saito, C Kaito JOURNAL OF CRYSTAL GROWTH 250 (3-4) 444 -449 2003年04月 [査読無し][通常論文]
     
    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.
  • Yuki Kimura, Yoshio Saito, Chihiro Kaito Surface Science 527 (1-3) L219 -L221 2003年03月10日 [査読無し][通常論文]
     
    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.
  • 木村 勇気, 石河 学, 谷垣 俊明, 鈴木 仁志, 齋藤 嘉夫, 墻内 千尋 日本物理学会講演概要集 58 (1) 835 -835 2003年03月06日
  • 佐藤 岳志, 谷垣 俊明, 鈴木 仁志, 齋藤 嘉夫, 木村 勇気, 墻内 千尋 日本物理学会講演概要集 58 (1) 835 -835 2003年03月06日
  • 鈴木 仁志, 谷垣 俊明, 木村 勇気, 齋藤 嘉夫, 墻内 千尋 日本物理学会講演概要集 58 (1) 834 -834 2003年03月06日
  • 車田 真実, 鈴木 仁志, 木村 勇気, 齋藤 嘉夫, 墻内 千尋 日本物理学会講演概要集 58 (1) 835 -835 2003年03月06日
  • 谷垣 俊明, 木村 勇気, 鈴木 仁志, 城戸 修, 墻内 千尋 日本物理学会講演概要集 58 (1) 835 -835 2003年03月06日
  • 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年02月 [査読無し][通常論文]
     
    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.
  • Y. Kimura, C. Kaito Journal of Crystal Growth 250 (3-4) 450 -457 2003年 [査読無し][通常論文]
  • Y. Kimura, C. Kaito Journal of Crystal Growth 255 (3-4) 282 -285 2003年 [査読無し][通常論文]
  • Y. Kimura, C. Kaito Astronomy and Astrophysics 409 159 -161 2003年 [査読無し][通常論文]
  • C Kaito, Y Kimura, S Tominaga, S Kimura, T Nakada, Y Saito PHYSICS OF LOW-DIMENSIONAL STRUCTURES 5-6 1 -7 2003年 [査読無し][通常論文]
     
    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.
  • T. Chigai, T. Yamamoto, C. Kaito, Y. Kimura The Astrophysical Journal 587 (2) 771 -776 2003年 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
     
    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.
  • 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年11月 [査読無し][通常論文]
     
    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.
  • H Suzuki, N Fukuzawa, T Tanigaki, T Sato, O Kido, Y Kimura, C Kaito JOURNAL OF CRYSTAL GROWTH 244 (2) 168 -172 2002年10月 [査読無し][通常論文]
     
    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.
  • 城戸 修, 鈴木 仁志, 木村 勇気, 齋藤 嘉夫, 墻内 千尋 日本物理学会講演概要集 57 (2) 769 -769 2002年08月13日
  • 墻内 千尋, 谷垣 俊明, 木村 勇気, 鈴木 仁志 日本物理学会講演概要集 57 (2) 768 -768 2002年08月13日
  • 木村 勇気, 墻内 千尋 日本物理学会講演概要集 57 (2) 768 -768 2002年08月13日
  • 池上 亜紀美, 木村 勇気, 鈴木 仁志, 齋藤 嘉夫, 墻内 千尋 日本物理学会講演概要集 57 (2) 768 -768 2002年08月13日
  • 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年08月 [査読無し][通常論文]
     
    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.
  • T Kobayashi, Y Kimura, H Suzuki, T Sato, T Tanigaki, Y Saito, C Kaito JOURNAL OF CRYSTAL GROWTH 243 (1) 143 -150 2002年08月 [査読無し][通常論文]
     
    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.
  • 石川 陽介, 木村 勇気, 鈴木 仁志, 齋藤 嘉夫, 墻内 千尋 日本結晶成長学会誌 29 (2) 165 -165 2002年07月01日 
    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.
  • 佐藤 岳志, 齋藤 嘉夫, 木村 勇気, 鈴木 仁志, 墻内 千尋 日本結晶成長学会誌 29 (2) 159 -159 2002年07月01日 
    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.
  • 石河 学, 木村 勇気, 鈴木 仁志, 斎藤 嘉夫, 墻内 千尋 日本結晶成長学会誌 29 (2) 161 -161 2002年07月01日 
    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.
  • 木村 勇気, 墻内 千尋 日本結晶成長学会誌 29 (2) 106 -106 2002年07月01日 
    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.
  • 城戸 修, 新宅 正行, 木村 純, 木村 勇気, 鈴木 仁志, 齋藤 嘉夫, 墻内 千尋 日本結晶成長学会誌 29 (2) 164 -164 2002年07月01日 
    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.
  • 上辻 勝也, 齋藤 嘉夫, 鈴木 仁志, 木村 勇気, 墻内 千尋 日本結晶成長学会誌 29 (2) 107 -107 2002年07月01日 
    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.
  • 田中 秀治, 木村 勇気, 鈴木 仁志, 斎藤 嘉夫, 墻内 千尋 日本結晶成長学会誌 29 (2) 160 -160 2002年07月01日 
    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.
  • Yuki Kimura, Chihiro Kaito, Katsumi Hanamoto, Muneo Sasaki, Seiji Kimura, Toshitaka Nakada, Yoshio Saito, Yasuyuki Nakayama Carbon 40 (7) 1043 -1050 2002年06月 [査読無し][通常論文]
     
    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.
  • M Sasaki, K Hanamoto, Y Kimura, C Kaito, H Miki, Y Nakayama REVIEW OF SCIENTIFIC INSTRUMENTS 73 (3) 1384 -1386 2002年03月 [査読無し][通常論文]
     
    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.
  • Y Kimura, Y Saito, T Nakada, C Kaito PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 13 (1) 11 -23 2002年01月 [査読無し][通常論文]
     
    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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
     
    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.
  • H Suzuki, T Tanigaki, T Sato, O Kido, Y Atou, Y Kimura, C Kaito PHYSICS OF LOW-DIMENSIONAL STRUCTURES 7-8 99 -105 2002年 [査読無し][通常論文]
     
    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.
  • 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年08月 [査読無し][通常論文]
  • 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年07月 [査読無し][通常論文]
     
    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.
  • 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年07月 [査読無し][通常論文]
     
    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.
  • 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年07月 [査読無し][通常論文]
     
    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.
  • 小川 昌子, 山岸 義弘, 木村 勇気, 半田 克巳, 原見 忠彦 日本物理学会講演概要集 56 (1) 853 -853 2001年03月09日
  • 木村 勇気, 花本 克巳, 中田 俊隆, 中山 康之, 墻内 千尋 日本物理学会講演概要集 56 (1) 782 -782 2001年03月09日
  • 木村 勇気, 花本 克巳, 佐々木 宗生, 木村 誠二, 中田 俊隆, 齋藤 嘉夫, 小池 千代枝, 中山 康之, 墻内 千尋 日本物理学会講演概要集 55 (2) 745 -745 2000年09月10日
  • C Kaito, A Ito, S Kimura, Y Kimura, Y Saito, T Nakada JOURNAL OF CRYSTAL GROWTH 218 (2-4) 259 -264 2000年09月 [査読無し][通常論文]
     
    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.
  • 谷垣 俊明, 木村 勇気, 木村 誠二, 齋藤 嘉夫, 墻内 千尋 日本結晶成長学会誌 27 (1) 171 -171 2000年07月01日 
    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.
  • 小林 崇仁, 木村 勇気, 花本 克巳, 中山 康之, 墻内 千尋 日本結晶成長学会誌 27 (1) 144 -144 2000年07月01日 
    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.
  • 木村 勇気, 花本 克巳, 中山 康之, 墻内 千尋 日本結晶成長学会誌 27 (1) 143 -143 2000年07月01日 
    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.
  • T Nakao, T Nakada, Y Nakayama, K Miyatani, Y Kimura, Y Saito, C Kaito THIN SOLID FILMS 370 (1-2) 155 -162 2000年07月 [査読無し][通常論文]
     
    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.
  • 木村 勇気, 木村 誠二, 中田 俊隆, 齋藤 嘉夫, 墻内 千尋 日本物理学会講演概要集 55 (1) 766 -766 2000年03月10日
  • C. Kaito, H. Nakamura, S. Kimura, Y. Kimura, T. Nakada, Y. Saito Thin Solid Films 359 (2) 283 -287 2000年01月31日 [査読無し][通常論文]
     
    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年 [査読無し][通常論文]
  • 木村 勇気, 木村 誠二, 中田 俊隆, 斎藤 嘉夫, 墻内 千尋 日本物理学会講演概要集 54 (2) 796 -796 1999年09月03日
  • 木村 勇気, 木村 誠二, 中田 俊隆, 齋藤 嘉夫, 墻内 千尋 日本結晶成長学会誌 26 (2) 35 -35 1999年07月01日 
    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.
  • 木村 勇気, 木村 誠二, 齋藤 嘉夫, 墻内 千尋, 中田 俊隆 日本物理学会講演概要集 54 (1) 94 -94 1999年03月15日
  • Kaito Chihiro, Kimura Seiji, Sato Kengo, KIMURA Yuki, OJIMA Yuki, HERRMANN Rudolf, KOIKE Chiyoe 立命舘大学理工学研究所紀要 58 11 -21 1999年
  • C Kaito, T Nakao, Y Ato, Y Kimura, S Kimura, T Nakada, Y Saito PHYSICS OF LOW-DIMENSIONAL STRUCTURES 12 53 -60 1999年 [査読無し][通常論文]
     
    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.

書籍等出版物

講演・口頭発表等

  • Formation experiments of cosmic dust analogues in microgravity environments  [通常講演]
    木村 勇気
    第33回 Grain Formation Workshop 2016年12月 口頭発表（一般）
  • 航空機を用いた微小重力実験  [通常講演]
    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年12月 口頭発表（一般）
  • 鉄ニッケル合金基板を用いた FT 型触媒反応実験  [通常講演]
    木村 勇気
    科研費新学術領域 分子進化 第12回ワークショップ 2016年10月 口頭発表（一般）
  • In-situ TEM Observation Reveals Early Stages of Crystallization Governed by Singular Phenomena of Nanoparticles  [通常講演]
    Yuki Kimura, Tomoya Yamazaki
    The 18th International Conference on Crystal Growth and Epitaxy 2016年08月 口頭発表（一般）
  • In-situ observation studies of nucleation and dissolution processes  [通常講演]
    木村 勇気
    The 16th International Summer School on Crystal Growth 2016年08月 ポスター発表
  • 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  [通常講演]
    木村 勇気
    低温物質の界面・ナノ現象ワークショップ2016 2016年07月 口頭発表（一般）
  • Advanced TEM studies give us new perspectives in water-mineral reactions  [通常講演]
    木村 勇気
    International Workshop on Water-mineral Interactions 2016年07月 口頭発表（一般）
  • Elucidating the early stages of protein crystallization by TEM  [通常講演]
    木村 勇気
    Goldschmidt 2016 2016年06月 口頭発表（一般）
  • 鉄基板上でのFT型触媒反応実験における反応効率の温度依存性  [通常講演]
    木村勇気, 佐藤理佳子, 土’山明, 永原裕子, 羽馬哲也, 日高宏, 渡部直樹, 香内晃
    日本地球惑星科学連合2016年大会 2016年05月 口頭発表（一般）
  • 観測ロケットS-520-30号機を用いたアルミナとシリカの気相からの核生成実験  [通常講演]
    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年05月 ポスター発表
  • Nucleation of interstellar dust  [招待講演]
    木村 勇気
    International School of Crystallography for Space Sciences 2016年04月 口頭発表（招待・特別）
  • 鉄基板を触媒としたFT 反応の温度依存性  [通常講演]
    木村 勇気
    科研費新学術領域 分子進化 第７回ワークショップ 2016年03月 口頭発表（一般）
  • 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  [通常講演]
    木村 勇気
    日本物理学会 第71回年次大会 2016年03月 口頭発表（一般）
  • Nucleation experiment to understand formation of cosmic dust  [招待講演]
    木村 勇気
    Astrophysical Ices in the Lab 2016年03月 口頭発表（基調）
  • 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  [通常講演]
    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年01月 口頭発表（一般）
  • 宇宙ダストの形成過程の解明に向けたS-520観測ロケットによる微小重力実験  [通常講演]
    木村勇気, 石塚紳之介, 中坪俊一, 斎藤史明, 山﨑智也, 左近樹, 竹内伸介, 稲富裕光
    第16回宇宙科学シンポジウム 2016年01月 口頭発表（一般）
  • 観測ロケットを用いた微小重力実験用装置の開発  [通常講演]
    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年12月
  • Nucleation experiments under microgravity condition  [通常講演]
    木村 勇気
    第32回Grain Formation Workshop 2015年12月
  • Nucleation from a supersaturated vapor  [通常講演]
    Yuki Kimura, Kyoko K. Tanaka, Kouchi Akira, Naoki Watanabe, Shunichi Nakatsubo, Shinnosuke Ishizuka, Yuko Inatomi
    ILTS International Symposium on Low Temperature Science 2015年12月 口頭発表（一般）
  • In-situ observation of nucleation from solution phase  [通常講演]
    木村 勇気
    Japan-Slovenia Bilateral Symposium of Transmission Electron Microscopy 2015年11月 口頭発表（一般）
  • S-520-30 号機の実験結果と今後の計画  [通常講演]
    木村勇気
    大気球シンポジウム 2015年11月 口頭発表（一般）
  • ナノ粒子～小さな結晶の不思議な振る舞い～  [招待講演]
    木村 勇気
    平成2７年度低温科学研究所公開講座 2015年11月 公開講演，セミナー，チュートリアル，講習，講義等
  • 均質核生成実験で探る宇宙ダストの形成過程  [招待講演]
    木村 勇気
    第45回結晶成長国内会議 2015年10月 口頭発表（招待・特別）
  • Nucleation and dissolution processes studied by in-situ observation using transmission electron microscopy  [招待講演]
    木村 勇気
    Department lecture of Jozef Stefan Institute 2015年10月 公開講演，セミナー，チュートリアル，講習，講義等
  • 透過電子顕微鏡による“その場”観察実験から探る核生成  [招待講演]
    木村 勇気
    第39回結晶成長討論会 2015年09月 口頭発表（招待・特別）
  • 干渉計の組立と環境相および固液界面のその場観察  [招待講演]
    木村 勇気
    第39回結晶成長討論会 2015年09月 公開講演，セミナー，チュートリアル，講習，講義等
  • Gravity Effects on the Formation of Ultrafine Particles by the Gas Evaporation Method  [通常講演]
    木村 勇気
    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年09月 口頭発表（一般）
  • Electron Holography Unveiled Formation Process of Extraterrestrial Magnetite  [招待講演]
    Yuki Kimura, Kazuo Yamamoto, Takeshi Sato
    Microscopy & Microanalysis 2015年08月 口頭発表（招待・特別）
  • Direct Liquid In Situ TEM Obseration of a Libing Protein Crystal  [招待講演]
    木村 勇気
    Microscopy & Microanalysis 2015年08月 公開講演，セミナー，チュートリアル，講習，講義等
  • Nucleation governing mineral evolution in space  [招待講演]
    木村 勇気
    宇宙科学談話会 2015年07月 公開講演，セミナー，チュートリアル，講習，講義等
  • ナノ粒子の生成過程と溶解過程  [招待講演]
    木村 勇気
    低温研セミナー 2015年06月 公開講演，セミナー，チュートリアル，講習，講義等
  • 初期太陽系星雲中でのFT型触媒反応による分子形成の再現実験  [通常講演]
    木村勇気, 山﨑智也, 土山明, 永原裕子, 羽馬哲也, 日高宏, 渡部直樹, 香内晃
    日本地球惑星科学連合2015年大会 2015年05月 口頭発表（一般）
  • 塩素酸ナトリウムナノ結晶の溶解過程のTEM観察  [通常講演]
    木村勇気, 山﨑智也, 佐藤久夫
    日本地球惑星科学連合2015年大会 2015年05月 口頭発表（一般）
  • 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年02月
  • 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年08月
  • 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年03月
  • 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年
  • 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年
  • 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年
  • 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年
  • 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年
  • 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  [通常講演]
    日本地球惑星科学連合2013年大会 2013年 ポスター発表
  • Nucleation and growth take into account physical properties of nanoparticles  [通常講演]
    The 2013 Collaborative Conference on Crystal Growth (3CG) 2013年
  • Nucleation experiments of iron dust under microgravity  [通常講演]
    Cosmic Dust VI 2013年
  • Nucleation experiment in vapor phase under microgravity using the sounding rocket S-520-28  [通常講演]
    17th International Conference on Crystal Growth and Epitaxy 2013年
  • Nucleation and growth of cosmic nanominerals based on size effects in mesoscale  [通常講演]
    17th International Conference on Crystal Growth and Epitaxy 2013年
  • Microgravity experiment using the sounding rocket S-520-28 for understanding a formation process of cosmic dust  [通常講演]
    3rd International Conference on Crystallogenesis and Mineralogy 2013年
  • 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  [通常講演]
    日本地球惑星科学連合2013年大会 2013年 ポスター発表
  • Nucleation and growth take into account physical properties of nanoparticles  [通常講演]
    The 2013 Collaborative Conference on Crystal Growth (3CG) 2013年
  • Nucleation experiments of iron dust under microgravity  [通常講演]
    Cosmic Dust VI 2013年
  • Nucleation experiment in vapor phase under microgravity using the sounding rocket S-520-28  [通常講演]
    17th International Conference on Crystal Growth and Epitaxy 2013年
  • Nucleation and growth of cosmic nanominerals based on size effects in mesoscale  [通常講演]
    17th International Conference on Crystal Growth and Epitaxy 2013年
  • Microgravity experiment using the sounding rocket S-520-28 for understanding a formation process of cosmic dust  [通常講演]
    3rd International Conference on Crystallogenesis and Mineralogy 2013年
  • 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年08月
  • 木村勇気
    日本物理学会講演概要集 2012年03月
  • 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年03月
  • 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年02月
  • 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  [通常講演]
    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年
  • 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年
  • 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年
  • 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年
  • 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  [通常講演]
    日本物理学会2012年春季大会 2012年
  • 宇宙ダストを模擬した核生成の“その場”観察実験  [通常講演]
    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年
  • Formation process of colloidal magnetite in the Tagish Lake meteorite  [通常講演]
    Workshop on Minerals-Water-Organics in the Early Solar System 2012年
  • 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  [通常講演]
    日本地球惑星科学連合2012年大会 2012年
  • 溶液成長における核生成と溶解過程のＴＥＭ中“その場”観察  [通常講演]
    日本地球惑星科学連合2012年大会 2012年 ポスター発表
  • Simultaneous determination of sticking probability and surface free energy by the homogeneous nucleation experiment  [通常講演]
    3rd Workshop of Nucleation Related to Cosmic Dust & its contribution to the organic formation in 4.6 billion years ago 2012年
  • Simultaneous determination of surface free energy and sticking probability based on formation experiment of cosmic dust and nucleation theories  [通常講演]
    The 5th meeting on Cosmic Dust 2012年
  • 宇宙における微粒子生成  [通常講演]
    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年
  • 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  [通常講演]
    日本惑星科学会 2012年秋季講演会 2012年
  • In-situ observation of nucleation and growth environment of cosmic dust analogues using an interferogram in laboratory  [通常講演]
    Achievements of G-COE Program for Earth and Planetary Dynamics and the Future Perspectives 2012年
  • Dual-wavelength interferometric observation of homogeneous nucleation from supercooled vapor under 1G and μG  [通常講演]
    9th China-Japan-Korea Workshop on Microgravity Sciences, Asian Microgravity Pre-Symposium 2012年
  • 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  [通常講演]
    日本物理学会2012年春季大会 2012年
  • 宇宙ダストを模擬した核生成の“その場”観察実験  [通常講演]
    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年
  • Formation process of colloidal magnetite in the Tagish Lake meteorite  [通常講演]
    Workshop on Minerals-Water-Organics in the Early Solar System 2012年
  • 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  [通常講演]
    日本地球惑星科学連合2012年大会 2012年
  • 溶液成長における核生成と溶解過程のＴＥＭ中“その場”観察  [通常講演]
    日本地球惑星科学連合2012年大会 2012年 ポスター発表
  • Simultaneous determination of sticking probability and surface free energy by the homogeneous nucleation experiment  [通常講演]
    3rd Workshop of Nucleation Related to Cosmic Dust & its contribution to the organic formation in 4.6 billion years ago 2012年
  • Simultaneous determination of surface free energy and sticking probability based on formation experiment of cosmic dust and nucleation theories  [通常講演]
    The 5th meeting on Cosmic Dust 2012年
  • 宇宙における微粒子生成  [通常講演]
    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年
  • 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  [通常講演]
    日本惑星科学会 2012年秋季講演会 2012年
  • In-situ observation of nucleation and growth environment of cosmic dust analogues using an interferogram in laboratory  [通常講演]
    Achievements of G-COE Program for Earth and Planetary Dynamics and the Future Perspectives 2012年
  • Dual-wavelength interferometric observation of homogeneous nucleation from supercooled vapor under 1G and μG  [通常講演]
    9th China-Japan-Korea Workshop on Microgravity Sciences, Asian Microgravity Pre-Symposium 2012年
  • 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年08月
  • 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年08月
  • 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年03月
  • 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年03月
  • 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年
  • 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年
  • 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年
  • 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年
  • 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年
  • 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年
  • 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年
  • 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年
  • 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  [通常講演]
    日本地球惑星科学連合2011年大会 2011年
  • 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  [通常講演]
    日本地球惑星科学連合2011年大会 2011年
  • Separate process of nucleation, coalescence and growth in vapor phase  [通常講演]
    International conference on materials for advanced teqhunologies (ICMAT) Symposium DD: CGCT-5-Fundamentals of Crystallization and Low Dimensional Crystalization 2011年 ポスター発表
  • Condensation of Cosmic Dust far from equilibrium condition  [通常講演]
    Asia Oceania Geosciences Society 8th Annual Meeting 2011年
  • Agreement of experiment and theory in homogeneous nucleation  [通常講演]
    74th Annual Meeting of the Meteoritical Society 2011年
  • Double Wavelength Interferometry for Direct Observation of Homogeneous Nucleation in Vapor Phase  [通常講演]
    XXII Congress and General Assembly International Union of Crystallography (IUCr2011) 2011年
  • 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  [通常講演]
    日本物理学会2011年秋季大会 2011年
  • Homogeneous nucleation and growth of nanoparticles in vapor phase  [通常講演]
    BIT’s 1st Annual World Congress of Nano-Science & Technology 2011年
  • TEMを用いた液中“その場”観察：塩素酸ナトリウムの核生成  [通常講演]
    第41回結晶成長国内会議 2011年
  • Interferometric Direct Observation of Nanocrystal Formation via Homogeneous Nucleation in Vapor Phase  [通常講演]
    The 20th Nisshin Engineering Particle Technology International Seminar (NEPTIS-20), Modeling of Nucleation and Growth on Crystallization Processes 2011年
  • 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  [通常講演]
    日本地球惑星科学連合2011年大会 2011年
  • 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  [通常講演]
    日本地球惑星科学連合2011年大会 2011年
  • Separate process of nucleation, coalescence and growth in vapor phase  [通常講演]
    International conference on materials for advanced teqhunologies (ICMAT) Symposium DD: CGCT-5-Fundamentals of Crystallization and Low Dimensional Crystalization 2011年 ポスター発表
  • Condensation of Cosmic Dust far from equilibrium condition  [通常講演]
    Asia Oceania Geosciences Society 8th Annual Meeting 2011年
  • Agreement of experiment and theory in homogeneous nucleation  [通常講演]
    74th Annual Meeting of the Meteoritical Society 2011年
  • Double Wavelength Interferometry for Direct Observation of Homogeneous Nucleation in Vapor Phase  [通常講演]
    XXII Congress and General Assembly International Union of Crystallography (IUCr2011) 2011年
  • 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  [通常講演]
    日本物理学会2011年秋季大会 2011年
  • Homogeneous nucleation and growth of nanoparticles in vapor phase  [通常講演]
    BIT’s 1st Annual World Congress of Nano-Science & Technology 2011年
  • TEMを用いた液中“その場”観察：塩素酸ナトリウムの核生成  [通常講演]
    第41回結晶成長国内会議 2011年
  • Interferometric Direct Observation of Nanocrystal Formation via Homogeneous Nucleation in Vapor Phase  [通常講演]
    The 20th Nisshin Engineering Particle Technology International Seminar (NEPTIS-20), Modeling of Nucleation and Growth on Crystallization Processes 2011年
  • 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年10月
  • 木村勇気, 塚本勝男
    日本物理学会講演概要集 2010年08月
  • HAMA Tetsuya, KIMURA Yuki, KOUCHI Akira, WATABE Naoki
    原子衝突研究協会年会講演概要集 2010年08月
  • A terminal of PAH evolution  [通常講演]
    215th Meeting of the American Astronomical Society 2010年
  • Synthesis of organic hollow globules based on singular phenomena of nanoparticles  [通常講演]
    The 41th Lunar and Planetary Science Conference 2010年
  • 干渉法を用いたナノ粒子凝縮過程の観察  [通常講演]
    日本地球惑星科学連合2010年大会 2010年
  • プラズマを用いた宇宙固体微粒子の再現実験  [通常講演]
    日本地球惑星科学連合2010年大会 2010年
  • Silicate Condensation Experiments in a Hydrogen Dominant Gas and Its Thermal History  [通常講演]
    73rd Annual Meeting of the Meteoritical Society 2010年
  • Condensation Takes Place in Far from Equilibrium Condition  [通常講演]
    73rd Annual Meeting of the Meteoritical Society 2010年 ポスター発表
  • Experimental demonstration of a forsterite cycle from evolved stars to the solar system  [通常講演]
    The 20th General Meeting of the International Mineralogical Association 2010年
  • In-situ observation by interferometer during condensation of smoke particles  [通常講演]
    The 20th General Meeting of the International Mineralogical Association 2010年
  • A terminal of PAH evolution  [通常講演]
    215th Meeting of the American Astronomical Society 2010年
  • Synthesis of organic hollow globules based on singular phenomena of nanoparticles  [通常講演]
    The 41th Lunar and Planetary Science Conference 2010年
  • 干渉法を用いたナノ粒子凝縮過程の観察  [通常講演]
    日本地球惑星科学連合2010年大会 2010年
  • プラズマを用いた宇宙固体微粒子の再現実験  [通常講演]
    日本地球惑星科学連合2010年大会 2010年
  • Silicate Condensation Experiments in a Hydrogen Dominant Gas and Its Thermal History  [通常講演]
    73rd Annual Meeting of the Meteoritical Society 2010年
  • Condensation Takes Place in Far from Equilibrium Condition  [通常講演]
    73rd Annual Meeting of the Meteoritical Society 2010年 ポスター発表
  • Experimental demonstration of a forsterite cycle from evolved stars to the solar system  [通常講演]
    The 20th General Meeting of the International Mineralogical Association 2010年
  • In-situ observation by interferometer during condensation of smoke particles  [通常講演]
    The 20th General Meeting of the International Mineralogical Association 2010年
  • 齊藤碧, 木村勇気
    日本天文学会年会講演予稿集 2009年08月
  • 木村勇気, NUTH Joseph A.,III
    日本天文学会年会講演予稿集 2009年08月
  • 渡部直樹, 香内晃, 木村勇気
    日本物理学会講演概要集 2009年08月
  • 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年08月
  • 野澤純, 塚本勝男, 甲野藤真, 木村勇気
    結晶成長国内会議予稿集 2009年
  • 木村勇気, NUTH Joseph A.,III
    結晶成長国内会議予稿集 2009年
  • 水素原子の表面拡散は速いか？：CO固体表面の場合  [通常講演]
    日本地球惑星科学連合2009年大会 2009年
  • Crystallization of silicate nanoparticles at lower temperature  [通常講演]
    International School of Crystallization 2009年 ポスター発表
  • Formation of Magnesium Silicates is Limited around Evolved Stars  [通常講演]
    The 214th Meeting of the American Astronomical Society 2009年
  • 実験から導かれたシリケイト微粒子の新しい生成過程  [通常講演]
    日本天文学会2009年秋季年会 2009年
  • ケイ酸塩ダストの新しい生成シナリオ  [通常講演]
    日本惑星科学会2009年秋季講演会 2009年
  • 晩期星における珪酸塩ダスト生成の再現実験  [通常講演]
    第27回Grain Formation Workshop / 平成21年度銀河のダスト研究会 2009年
  • 気相実験が示す“かんらん石”宇宙ダスト粒子の起源  [通常講演]
    第39回結晶成長国内会議 2009年
  • 水素原子の表面拡散は速いか？：CO固体表面の場合  [通常講演]
    日本地球惑星科学連合2009年大会 2009年
  • Crystallization of silicate nanoparticles at lower temperature  [通常講演]
    International School of Crystallization 2009年 ポスター発表
  • Formation of Magnesium Silicates is Limited around Evolved Stars  [通常講演]
    The 214th Meeting of the American Astronomical Society 2009年
  • 実験から導かれたシリケイト微粒子の新しい生成過程  [通常講演]
    日本天文学会2009年秋季年会 2009年
  • ケイ酸塩ダストの新しい生成シナリオ  [通常講演]
    日本惑星科学会2009年秋季講演会 2009年
  • 晩期星における珪酸塩ダスト生成の再現実験  [通常講演]
    第27回Grain Formation Workshop / 平成21年度銀河のダスト研究会 2009年
  • 気相実験が示す“かんらん石”宇宙ダスト粒子の起源  [通常講演]
    第39回結晶成長国内会議 2009年
  • 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年02月
  • 木村勇気
    日本惑星科学会秋季講演会予稿集 2007年
  • 弥永英臣, 熊本明仁, 木村勇気, 墻内千尋
    結晶成長国内会議予稿集 2007年
  • 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年
  • 山下鉄平, 木村勇気, 城戸修, 熊本明仁, 墻内千尋
    結晶成長国内会議予稿集 2007年
  • 新名賢治, 熊本明仁, 木村勇気, 墻内千尋
    結晶成長国内会議予稿集 2007年
  • 熊本明仁, 木村勇気, 墻内千尋, 齋藤嘉夫
    結晶成長国内会議予稿集 2007年
  • 横山香織, 山下鉄平, 熊本明仁, 木村勇気, 小池千代枝, 墻内千尋
    結晶成長国内会議予稿集 2007年
  • 足立俊輔, 熊本明仁, 新宅正行, 木村勇気, 衣田康彦, 墻内千尋
    日本結晶成長学会誌 2006年11月
  • 熊本明仁, 新宅正行, 車田真実, 城戸修, 木村勇気, 墻内千尋
    日本結晶成長学会誌 2006年11月
  • 木村勇気, NUTH Joseph A.,III, CHAKRABORTY Subrata, THIEMENS Mark H
    日本結晶成長学会誌 2006年11月
  • 木村勇気, NUTH Joseph A.,III
    日本天文学会年会講演予稿集 2006年08月
  • 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年
  • 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年
  • 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年
  • 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年10月
  • 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年10月
  • 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年10月
  • 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年09月
  • 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年09月
  • 鈴木仁志, 佐藤岳志, 木村勇気, 斎藤嘉夫, かい内千尋
    日本結晶成長学会誌 2003年07月
  • 城戸修, 佐々木晋一, 車田真実, 鈴木仁志, 木村勇気, 斎藤嘉夫, かい内千尋
    日本結晶成長学会誌 2003年07月
  • 池上亜紀美, 木村勇気, 鈴木仁志, 斎藤嘉夫, かい内千尋
    日本結晶成長学会誌 2003年07月
  • 木村勇気, 谷垣俊明, 鈴木仁志, 佐藤岳志, かい内千尋
    日本結晶成長学会誌 2003年07月
  • 上辻勝也, 鈴木仁志, 木村勇気, 斎藤嘉夫, かい内千尋
    日本結晶成長学会誌 2003年07月
  • 佐々木晋一, 木村勇気, 斎藤嘉夫, 竹田篤, かい内千尋
    日本結晶成長学会誌 2003年07月
  • 車田真実, 木村勇気, 鈴木仁志, 城戸修, 斎藤嘉夫, かい内千尋
    日本結晶成長学会誌 2003年07月
  • 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年10月
  • 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年10月
  • 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年10月
  • 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年10月
  • 上辻勝也, 斎藤嘉夫, 鈴木仁志, 木村勇気, かいと千尋
    日本結晶成長学会誌 2002年07月
  • 石川陽介, 木村勇気, 鈴木仁志, 斎藤嘉夫, かいと千尋
    日本結晶成長学会誌 2002年07月
  • 木村勇気, かいと千尋
    日本結晶成長学会誌 2002年07月
  • 城戸修, 新宅正行, 木村純, 木村勇気, 鈴木仁志, 斎藤嘉夫, かいと千尋
    日本結晶成長学会誌 2002年07月
  • 佐藤岳志, 斎藤嘉夫, 木村勇気, 鈴木仁志, かいと千尋
    日本結晶成長学会誌 2002年07月
  • 石河学, 木村勇気, 鈴木仁志, 斎藤嘉夫, かいと千尋
    日本結晶成長学会誌 2002年07月
  • 田中秀治, 木村勇気, 鈴木仁志, 斎藤嘉夫, かいと千尋
    日本結晶成長学会誌 2002年07月
  • 木村勇気, 墻内千尋
    日本天文学会年会講演予稿集 2002年
  • 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年10月
  • 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年03月
  • 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年10月
  • 谷垣俊明, 木村勇気, 木村誠二, 斎藤嘉夫, かい内千尋
    日本結晶成長学会誌 2000年07月
  • WO3薄膜の結晶化  [通常講演]
    木村勇気, 花本克巳, 中山康之, かい内千尋
    日本結晶成長学会誌 2000年07月
  • SnO2膜の結晶化  [通常講演]
    小林崇仁, 木村勇気, 花本克巳, 中山康之, かい内千尋
    日本結晶成長学会誌 2000年07月
  • 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年09月
  • 木村勇気, 木村誠二, 中田俊隆, 斎藤嘉夫, かいと千尋
    日本結晶成長学会誌 1999年07月
  • 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年03月
  • 有機分子進化におけるFT反応の寄与  [通常講演]
    木村勇気, 佐藤理佳子, 土’山明, 永原裕子, 羽馬哲也, 日高宏, 渡部直樹, 香内晃
    新学術領域「宇宙分子進化」全体集会 口頭発表（一般）

所属学協会

  • アメリカ顕微鏡学会   日本マイクログラビティ応用学会   アメリカ天文学会   日本地球惑星科学連合   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（作品等）

  • 気相からの核形成と宇宙ダスト
    2013年 -2014年
  • 気相からの核形成と宇宙ダスト
    2013年 -2014年
  • 気相からの核形成と宇宙ダスト
    2012年 -2013年
  • 気相からの核形成と宇宙ダスト
    2012年 -2013年
  • 宇宙の塵（ちり）の不思議なでき方
    2011年 -2012年
  • 気相からの核形成と宇宙ダスト
    2011年 -2012年
  • 宇宙の塵（ちり）の不思議なでき方
    2011年 -2012年
  • 気相からの核形成と宇宙ダスト
    2011年 -2012年
  • 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年 -2012年
  • 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年 -2012年
  • 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年 -2010年
  • 原始惑星系円盤における低温結晶成長過程
    2009年 -2010年
  • 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年 -2010年
  • 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年 -2010年
  • Nano Dust in the Solar System: Formation, Interactions and Detection
    2009年 -2010年
  • 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年 -2010年
  • 原始惑星系円盤における低温結晶成長過程
    2009年 -2010年
  • 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年 -2010年
  • 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年 -2010年
  • Nano Dust in the Solar System: Formation, Interactions and Detection
    2009年 -2010年

共同研究・競争的資金等の研究課題

  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2023年04月 -2027年03月 
    代表者 : 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)
    研究期間 : 2024年04月 -2027年03月 
    代表者 : 新家寛正, 木村勇気, 灘浩樹, 羽馬哲也
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2023年04月 -2025年03月 
    代表者 : 木村 勇気
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2020年08月 -2025年03月 
    代表者 : 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：
    研究期間 : 2023年04月 -2024年03月 
    代表者 : 釣優香, 木村勇気, 山﨑智也
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2020年04月 -2021年03月 
    代表者 : 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。
  • 日本学術振興会：科学研究費補助金 基盤研究（S）
    研究期間 : 2015年04月 -2020年03月 
    代表者 : 木村 勇気
     
    我々は、独自の実験装置群を構築して結晶化の初期過程に多角的に迫ることで、気相からの核生成を支配する鍵因子はナノ粒子の融点降下と付着確率（ダイマーの形成）にあることを示した。また、溶液からの核生成過程をその場観察できる透過型電子顕微鏡法を確立し、タンパク質の結晶化における水和層の役割を解明した。気相と溶液の両方を扱うことで、初めて核生成と前駆体のかかわりをナノ領域に現れる特異性の観点から直接的に示した。さらに、核生成の理解には、臨界核の形成に留まらず、ナノ領域を超えて安定なバルク結晶に成長するまでを考える必要があることを明確にした。さらに、ナノ領域の物性を考慮した核生成モデルの提案まで行った。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2013年06月 -2018年03月 
    代表者 : 永原 裕子, 為則 雄祐, 星野 真人, 青木 貞雄, 木村 勇気, 高橋 修, 渡辺 紀生, 土山 明
     
    原始惑星系円盤進化における，固体粒子表面におけるFischer-Tropsh反応を，新規開発実験装置により実験的に検討した．金属表面および非晶質珪酸塩上で，直鎖状炭素等単純な有機物が形成され，非晶質珪酸塩上では金属上より高温において反応が進行することが明らかとなった．SPring-8 に高分解能結像型軟X線分光装置を開発した．高分解能で物質の化学組成，分子の結合形態等を求めることの出来る装置であり，本領域研究のさまざまな班との共同研究に供された．無機結晶，有機物の表面反応を第一原理計算により計算するためのツール開発をおこなった．さらに，円盤進化過程における有機物と氷の時空分布を求めた．
  • 日本学術振興会：科学研究費補助金 挑戦的萌芽
    研究期間 : 2016年04月 -2018年03月 
    代表者 : 木村 勇気
     
    電子線ホログラフィーを用いることで、残留磁化から温度や磁場などの生成環境を紐解く岩石磁気学的手法を隕石中のナノメートルサイズの粒子に適用することに成功した。さらに、従来の隕石のバルク分析では隠れていた、構成粒子個々の残留磁化の可視化から生成環境を解読できることを示した。炭素質隕石中に含まれるマグネタイト粒子に着目し、残留磁化の温度依存性をその場観察した結果、経験した温度が高くなるに従って磁化の強さが変化することが分かり、46億年前にマグネタイトが生成した際の温度を決定することに成功した。
  • 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
    研究期間 : 2015年04月 -2017年03月 
    代表者 : 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
    研究期間 : 2016年10月 -2017年02月 
    代表者 : 木村 勇気
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2013年10月 -2016年03月 
    代表者 : 香内 晃, 日高 宏, 大場 康弘, 羽馬 哲也, 千貝 健, 渡部 直樹, 木村 勇気, 都丸 隆行
     
    氷の構造（ミクロ～マクロ）を解析するための超高真空極低温透過型電子顕微鏡を開発した．鏡体内で制御された条件での氷の作製が可能であり，氷に紫外線を照射することもできる． 本装置を用いて以下の研究を行った．(1)アモルファス氷のミクロな欠陥構造を初めて直接観察した．(2)氷Ih，氷Icへ75-100Kで紫外線を照射することにより，氷XIが生成されることを発見した．一方，アモルファス氷では相転移は観察されなかった．(3)CO:H2O=10:1-50:1を10Kで蒸着しその後温度を上昇させCOを昇華させると，高密度アモルファス氷が生成されることを見出した．この方法をマトリックス昇華法と命名した．
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2010年04月 -2014年03月 
    代表者 : 塚本 勝男, 中村 智樹, 中本 泰史, 稲富 裕光, 中村 教博, 木村 勇気, 三浦 均
     
    原始太陽系と同じ非接触環境を模擬した、コンドリュールメルト液滴からの結晶化の“その場”観察を行なった．その結果，天然の組織を再現するには、これまで考えられていた条件より遥かに大きい超過冷却度（300~ 1100 K）が必要で、数秒の短時間で完了することが分かった．さらに，過冷却度に応じて多様な凝固組織の出現を確認し、天然隕石に見られる多様性との対応を行った．この結果をもとにすることで、コンドリュール組織形成に関する速度論的な理論モデル化が初めて行えた。
  • 文部科学省：科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2013年 -2014年 
    代表者 : 木村 勇気
     
    核生成時の前駆体の役割は、今世界的に注目されている課題である。本研究課題では、水に代えてイオン液体を溶媒に用いた透過電子顕微鏡による溶液成長の“その場”観察実験により、核生成過程を相同定を含めてナノスケールで直接観察することに初めて成功した。その結果、安定相に加えて、準安定結晶も同時に生成することが分かった。また、準安定相が安定相に接触すると、瞬く間に取り込まれる現象や、成長速度はほとんど同じであるのに、溶解速度は準安定相の方が大きいことも分かり、これらの結果として最終生成物の結晶相が決まるという、全く新しい核生成径路を発見した。
  • 文部科学省：科学研究費補助金(若手研究(A))
    研究期間 : 2012年 -2014年 
    代表者 : 木村 勇気
     
    気相中で微粒子が核生成する際の温度と濃度を干渉計を用いて決定することに成功し、核生成理論を用いることで、ナノ粒子の表面自由エネルギーと付着確率の決定に成功した。その結果、均質核生成には10の4乗から10の14乗という超高過飽和が必要であり、付着確率は0.01%という小さな値を取ることが分かった。また、非晶質相が核生成した後に結晶相に転移することや、核生成初期には結晶構造が未決定なことなど、均質核生成の描像の一端を解明した。
  • 文部科学省：科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2010年 -2011年 
    代表者 : 木村 勇気, 左近 樹
     
    天体のスペクトルに多数の未同定バンドが残っている一因はナノ領域に現れる特異現象にあると考え、ナノ粒子の赤外スペクトルを実験室で得ることを目的に研究を立ち上げた。赤外スペクトルその場観測装置を新たに作製し、気相中をフリーに漂うナノ粒子の赤外スペクトルを測定できるようになった。実際に測定した結果、従来のバルクやKBr錠剤法に比べ、ピーク位置のシフトと半値幅の大幅な減少が確認でき、未同定バンドの解明に向けた突破口が拓けた。
  • 文部科学省：科学研究費補助金(若手研究(A))
    研究期間 : 2010年 -2011年 
    代表者 : 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
    研究期間 : 2008年 -2011年
  • Grain formation 4.6 Billion Years Ago based on anomalous phenomena appeared in nano-region
    Grant-in-Aid for Scientific Research
    研究期間 : 2008年 -2011年
  • 文部科学省：科学研究費補助金(若手研究(スタートアップ))
    研究期間 : 2007年 -2008年 
    代表者 : 木村 勇気
     
    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
    研究期間 : 2007年 -2008年
  • 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
    研究期間 : 2004年 -2006年
  • 日本学術振興会：科学研究費補助金
    研究期間 : 2002年 -2003年 
    代表者 : 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。

社会貢献活動

  • ナノ粒子特有の振る舞いから宇宙の謎に迫る
    期間 : 2017年11月11日 - 2017年11月11日
    役割 : 講師
    イベント・番組・新聞雑誌名 : 第26回先端科学移動大学2017（市民講座）
    社会人・一般　旭川市科学館「サイパル」
  • 煙ってなあに
    期間 : 2017年11月10日 - 2017年11月10日
    役割 : 講師
    イベント・番組・新聞雑誌名 : 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

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