Researcher Database

Yuki Kimura
Institute of Low Temperature Science Joint Research Division
Associate Professor

Researcher Profile and Settings

Affiliation

  • Institute of Low Temperature Science Joint Research Division

Job Title

  • Associate Professor

URL

J-Global ID

Research Interests

  • 透過型電子顕微鏡   核形成   宇宙ダスト   結晶成長   結晶   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   電子顕微鏡   実験   宇宙塵   ナノ粒子   microscopy   experiments   cosmic dust   Nanoparticles   

Research Areas

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

Academic & Professional Experience

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

Education

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

Association Memberships

  • THE JAPAN SOCIETY OF MICROGRAVITY APPLICATION   JAPAN GEOSCIENCE UNION   日本天文学会   日本物理学会   アメリカ天文学会   日本惑星科学会   結晶成長学会   Reviewer of the award in the Japanese Society for Planetary Sciences   日本物理学会領域9   日本惑星科学会 編集委員会   日本天文学会   日本物理学会   アメリカ天文学会   日本惑星科学会   結晶成長学会   

Research Activities

Published Papers

  • Aki Takigawa, Yoshihiro Furukawa, Yuki Kimura, Bjorn Davidsson, Tomoki Nakamura
    ASTROPHYSICAL JOURNAL 881 (1) 27  0004-637X 2019/08 [Refereed][Not invited]
     
    Hydration is a major mineral alteration process in primitive asteroids and it might occur in comet nuclei; however, it is poorly understood at low temperatures, especially below the freezing point of water. Long-duration experiments were performed with exposures of amorphous silicate nanoparticles and organic compounds (glycine and ribose) to D2O and D2O + NH3 ices and vapors at temperatures of -17 degrees C and -27 degrees C for 10-120 days; and with exposure of amorphous silicates to H2O vapor/liquid at >25 degrees C for 10 days. The amorphous silicates were analyzed by X-ray diffraction and Fourier-transform infrared spectroscopy, and recovery of organic molecules was determined by liquid chromatography-mass spectrometry. No hydration of amorphous silicates or organic compounds was observed after exposure at temperatures below -17 degrees C for 120 days to ices with or without NH3, whereas hydration of the amorphous silicates was observed in experiments above room temperature. The estimated thermal history of the nucleus of the short-period comet 67P/Churyumov-Gerasimenko indicates that the surface temperature does not exceed -45 degrees C, even in a region exposed to strong solar illumination during the perihelion passage. Assuming hydration is controlled by the collision frequency between H2O molecules and dust particles, the present results indicate that cometary dust does not hydrate for more than 25-510 periods of comet 67P. This is consistent with the absence of phyllosilicates on 67P and suggests that amino acids and sugars have not been altered.
  • Masashi Tsuge, Tetsuya Hama, Yuki Kimura, Akira Kouchi, Naoki Watanabe
    The Astrophysical Journal 878 23  2019/06 [Refereed][Not invited]
  • Kyoko K. Tanaka, Yuki Kimura
    Physical Chemistry Chemical Physics 21 2410 - 2418 2019/01 [Refereed][Not invited]
  • I. Sakon, I. Endo, A. Ikeuchi, T. Onaka, Y. Kimura, S. Kimura, S. Wada, M. Nakamura, J. Ichimura, N. Ogawa, N. Ohkouchi, Y. Inatomi
    航空宇宙学会誌 66 (12) 381 - 387 2018/12 [Refereed][Not invited]
  • Shinnosuke Ishizuka, Yuki Kimura, Jun Kawano, Rafael Escribano, Tomoya Yamazaki, Tetsuya Hama, Rikako Sato
    The Journal of Physical Chemistry, Part C 122 25092  2018/10 [Refereed][Not invited]
  • Shinnosuke Ishizuka, Yuki Kimura, Itsuki Sakon, Hiroshi Kimura, Tomoya Yamazaki, Shinsuke Takeuchi, Yuko Inatomi
    Nature Communications 9 (1) 3820  2018/09 [Refereed][Not invited]
  • 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 350305  2018/07 [Refereed][Not invited]
  • Y. Kimura, M. Tsuge, V. Pirronello, A. Kouchi, N. Watanabe
    Astrophysical Journal Letters 858 (2) 23  2041-8213 2018/05/10 [Refereed][Not invited]
     
    The diffusion of hydrogen atoms on dust grains is a key process in the formation of interstellar H2 and some hydrogenated molecules such as formaldehyde and methanol. We investigate the adsorption and diffusion of H atoms on pure solid CO as an analog of dust surfaces observed toward some cold interstellar regions. Using a combination of photostimulated desorption and resonance-enhanced multiphoton ionization methods to detect H atoms directly, the relative adsorption probabilities and diffusion coefficients of the H atoms are measured on pure solid CO at 8, 12, and 15 K. There is little difference between the diffusion coefficients of the hydrogen and deuterium atoms, indicating that the diffusion is limited by thermal hopping. The activation energies controlling the H-atom diffusion depend on the surface temperature, and values of 22, 30, and ∼37 meV were obtained for 8, 12, and 15 K, respectively.
  • Hisao Satoh, Yuki Kimura, Erika Furukawa
    Industrial and Engineering Chemistry Research 57 (1) 79 - 83 1520-5045 2018/01/10 [Refereed][Not invited]
     
    Unlike other solidified materials, concrete has an internal structure that contains small pores that vary in size from several nanometers to the submicrometer range. These pores govern the strength of the material and hence the lifetime of concrete buildings. The size of the pores is governed by the presence of calcium silicate hydrate (CaO·2SiO2·4H2O, C-S-H). To identify how the pore size is determined during the concretion process, we used transmission electron microscopy to examine the early solidification of a simplified reaction system consisting of silica, portlandite [Ca(OH)2, CH], and water. The silica particles, used to suppress the degradation of concrete, expanded and, consequently, embedded the pores through hydration before C-S-H was formed, contrary to the predicted decrease in pore size by C-S-H formation after simple dissolution of silica. Visualization of this type of solidification process should permit improvement in the mechanical strength of concrete.
  • Development of an ultrahigh vacuum low temperature transmission electron microscope for in-situ observation of ices
    Akira KOUCHI, Hiroshi HIDAKA, Naoki WATANABE, Tetsuya HAMA, Yuki KIMURA, Shunichi NAKATSUBO, Kazuyuki FUJITA, Kunio SINBORI, Masayuki IKEDA
    日本雪氷学会誌 雪氷 80 (1) 19 - 36 2018/01 [Refereed][Not invited]
  • Kaori Yokoyama, Yuki Kimura, Chihiro Kaito
    ACS EARTH AND SPACE CHEMISTRY 1 (10) 601 - 607 2472-3452 2017/12 [Refereed][Not invited]
     
    To achieve a better understanding of material evolution in the early solar system, experiments have been performed to constrain the environments in which many of the dust grains formed. Sulfur is an element whose chemical processes and mineralization of related grains are poorly understood. The high reactivity of sulfur makes it difficult to perform experiments in conventional metallic chambers, because these become heavily contaminated. Nevertheless, sulfur is expected to be a key element to understand processes in the early solar system. Here, we performed experiments on the condensation of calcium sulfide (CaS) in a glass chamber in an attempt to identify constraints on the possible formation environments of components of enstatite chondrites in terms of the effects of oxygen. Condensation experiments showed that calcium sulfate (CaSO4) or solid-solution particles of CaS and calcium oxide (CaO), i.e., [Ca(S,O)], were formed at various partial pressures of oxygen. Our results expand the range of possible conditions for the condensation of meteoritic CaS (oldhamite) from a nebula gas and extend the range of environments for the formation of the parent bodies of enstatite chondrites to include those more oxidizing environments in the solar nebula, where the atomic ratio of oxygen to sulfur was less than 6 and where CaS could have incorporated oxygen to form Ca(S,O) without the formation of CaSO4.
  • Shogo Tachibana, Akira Kouchi, Tetsuya Hama, Yasuhiro Oba, Laurette Piani, Iyo Sugawara, Yukiko Endo, Hiroshi Hidaka, Yuki Kimura, Ken-Ichiro Murata, Hisayoshi Yurimoto, Naoki Watanabe
    Science advances 3 (9) eaao2538  2017/09 [Refereed][Not invited]
     
    Interstellar ice is believed to be a cradle of complex organic compounds, commonly found within icy comets and interstellar clouds, in association with ultraviolet (UV) irradiation and subsequent warming. We found that UV-irradiated amorphous ices composed of H2O, CH3OH, and NH3 and of pure H2O behave like liquids over the temperature ranges of 65 to 150 kelvin and 50 to 140 kelvin, respectively. This low-viscosity liquid-like ice may enhance the formation of organic compounds including prebiotic molecules and the accretion of icy dust to form icy planetesimals under certain interstellar conditions.
  • Shinnosuke Ishizuka, Yuki Kimura, Satoki Yokoi, Tomoya Yamazaki, Rikako Sato, Tetsuya Hama
    NANOSCALE 9 (28) 10109 - 10116 2040-3364 2017/07 [Refereed][Not invited]
     
    Nucleation and subsequent rapid growth are enigmatic due to the unrevealed pathways. Despite the relatively simpler mechanism compared to nucleation and growth in solution, that in vapor has received little attention. The largest hindrance to unveiling this process may be observing the rapid and mesoscopic-scale phenomena. To overcome this hindrance, we combine an experimental approach with in situ spatial scanning Fourier-transform infrared spectroscopy, which reveals the nucleating and growing nanoparticles in vapor. The nanoparticles are then collected at different evolutionary stages and analyzed by ex situ transmission electron microscopy (TEM). Needle-shaped molybdenum oxide (MoO3) nanoparticles were formed within similar to 0.1 s after homogeneous nucleation from a highly supersaturated vapor. Over one second, the needle particles gradually evolved into a cubic shape by fusion in a crystallographically favored orientation in a free-flying state in vapor. The similar sizes of the elongated axes of the needle and cubic structures suggest an additional growth stage, in which the needle particles become the growth units of the cubic particles. The morphology of a final crystal should reflect the formation environment of the particle because growing crystals are sensitive to the formation conditions such as temperature, concentration, and impurities. Although nucleation under very high supersaturation induces the anisotropic growth of the needle particles, this information of the initial nucleation environment is lost in the final cubic crystal. These findings enrich our understanding of pathways in the nucleation and growth of nanoparticles and provide new insights into the growth stages driven by oriented attachment.
  • Tetsuya Hama, Shinnosuke Ishizuka, Tomoya Yamazaki, Yuki Kimura, Akira Kouchi, Naoki Watanabe, Toshiki Sugimoto, Valerio Pirronello
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 (27) 17677 - 17684 1463-9076 2017/07 [Refereed][Not invited]
     
    Crystalline ice formation requires water molecules to be sufficiently mobile to find and settle on the thermodynamically most stable site. Upon cooling, however, diffusion and rearrangement become increasingly kinetically difficult. Water ice grown by the condensation of water vapor in laboratory is thus generally assumed to be in a metastable amorphous form below 100 K. Here, we demonstrate the possibility of crystalline ice formation at extremely low temperature using a water/neon matrix (1/1000, 30000 monolayers) prepared at 6 K, which is subsequently warmed to 11-12 K. In situ infrared spectroscopy revealed the assembly of the dispersed water molecules, forming crystalline ice I during the sublimation of the neon matrix for 40-250 seconds. This finding indicates that the high mobility of the water molecules during matrix sublimation can overcome the kinetic barrier to form crystals even at extremely low temperature.
  • Rafael Escribano, Emilio Artacho, Akira Kouchi, Tetusya Hama, Yuki Kimura, Hiroshi Hidaka, Naoki Watanabe
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 (10) 7280 - 7287 1463-9076 2017/03 [Refereed][Not invited]
     
    Models for the inclusion of water molecules in carbon monoxide matrices are developed using density functional theory applied to amorphous solid systems. The models cover a large range of systems for smaller or larger CO matrices with different water content, consisting of either individual H2O molecules or small clusters linked by H-bonds. The vibrational spectra of the samples are predicted at the minimum of their potential energy surface. The spectra allow instances where the water molecules remain isolated or form aggregates to be discerned, and they also provide an indication of the strength of the H-bonding, when present. The calculations support recent experimental observations that linked IR bands at 3707 cm(-1) and 3617 cm(-1) to the presence of unbound water molecules in water-poor CO/H2O mixed ices. Assignment of some observed bands to water dimers or trimers is suggested as well. The residual static pressure in fixed-volume simulation cells is also calculated.
  • Rafael Escribano, Emilio Artacho, Akira Kouchi, Tetusya Hama, Yuki Kimura, Hiroshi Hidaka, Naoki Watanabe
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 (10) 7280 - 7287 1463-9076 2017/03 [Refereed][Not invited]
     
    Models for the inclusion of water molecules in carbon monoxide matrices are developed using density functional theory applied to amorphous solid systems. The models cover a large range of systems for smaller or larger CO matrices with different water content, consisting of either individual H2O molecules or small clusters linked by H-bonds. The vibrational spectra of the samples are predicted at the minimum of their potential energy surface. The spectra allow instances where the water molecules remain isolated or form aggregates to be discerned, and they also provide an indication of the strength of the H-bonding, when present. The calculations support recent experimental observations that linked IR bands at 3707 cm(-1) and 3617 cm(-1) to the presence of unbound water molecules in water-poor CO/H2O mixed ices. Assignment of some observed bands to water dimers or trimers is suggested as well. The residual static pressure in fixed-volume simulation cells is also calculated.
  • L. Piani, S. Tachibana, T. Hama, H. Tanaka, Y. Endo, I. Sugawara, L. Dessimoulie, Y. Kimura, A. Miyake, J. Matsuno, A. Tsuchiyama, K. Fujita, S. Nakatsubo, H. Fukushi, S. Mori, T. Chigai, H. Yurimoto, A. Kouchi
    ASTROPHYSICAL JOURNAL 837 (1) 35  0004-637X 2017/03 [Refereed][Not invited]
     
    Refractory organic compounds formed in molecular clouds are among the building blocks of the solar system objects and could be the precursors of organic matter found in primitive meteorites and cometary materials. However, little is known about the evolutionary pathways of molecular cloud organics from dense molecular clouds to planetary systems. In this study, we focus on the evolution of the morphological and viscoelastic properties of molecular cloud refractory organic matter. We found that the organic residue, experimentally synthesized at similar to 10 K from UV-irradiated H2O-CH3OH-NH3 ice, changed significantly in terms of its nanometer to micrometer-scale morphology and viscoelastic properties after UV irradiation at room temperature. The dose of this irradiation was equivalent to that experienced after short residence in diffuse clouds (<= 10(4) years) or irradiation in outer protoplanetary disks. The irradiated organic residues became highly porous and more rigid and formed amorphous nanospherules. These nanospherules are morphologically similar to organic nanoglobules observed in the least-altered chondrites, chondritic porous interplanetary dust particles, and cometary samples, suggesting that irradiation of refractory organics could be a possible formation pathway for such nanoglobules. The storage modulus (elasticity) of photo-irradiated organic residues is similar to 100 MPa irrespective of vibrational frequency, a value that is lower than the storage moduli of minerals and ice. Dust grains coated with such irradiated organics would therefore stick together efficiently, but growth to larger grains might be suppressed due to an increase in aggregate brittleness caused by the strong connections between grains.
  • 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 Proceedings of the National Academy of Sciences 201606948  2017/02 [Refereed][Not invited]
  • 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 201606948  2017 [Refereed][Not invited]
  • Kanji Ishii, Yuki Kimura, Tomoya Yamazaki, Yuya Oaki, Hiroaki Imai
    RSC ADVANCES 7 (57) 35711 - 35716 2046-2069 2017 [Refereed][Not invited]
     
    The evolution of a V2O5.nH(2)O gel skeleton through the hydration of vanadium alkoxide was monitored using ex situ and in situ transmission electron microscopy and X-ray diffractometry. We successfully observed the morphological evolution of the gel skeleton by vacuum drying after replacing the pore liquid of acetone with cyclohexane. The gel skeleton comprised of nanofibers 10-20 nm wide and over 300 nm long was formed from ultrathin films 1-3 nm thick through thin fibrils 3-7 nm wide and about 100 nm long. Fixation of the thin fibrils by a simple vacuum-drying technique provided xerogels having a specific surface area as high as similar to 320 m(2) g(-1) at ambient temperature. Highly porous polypyrrole frameworks were obtained as replicas of the V2O5.nH(2)O xerogels.
  • Yuki Kimura, Kyoko K. Tanaka, Takaya Nozawa, Shinsuke Takeuchi, Yuko Inatomi
    SCIENCE ADVANCES 3 (1) e1601992  2375-2548 2017/01 [Refereed][Not invited]
     
    The abundant forms in which the major elements in the universe exist have been determined from numerous astronomical observations and meteoritic analyses. Iron (Fe) is an exception, in that only depletion of gaseous Fe has been detected in the interstellar medium, suggesting that Fe is condensed into a solid, possibly the astronomically invisible metal. To determine the primary form of Fe, we replicated the formation of Fe grains in gaseous ejecta of evolved stars by means of microgravity experiments. We found that the sticking probability for the formation of Fe grains is extremely small; only a few atoms will stick per hundred thousand collisions so that homogeneous nucleation of metallic Fe grains is highly ineffective, even in the Fe-rich ejecta of type Ia supernovae. This implies that most Fe is locked up as grains of Fe compounds or as impurities accreted onto other grains in the interstellar medium.
  • Shinnosuke Ishizuka, Yuki Kimura, Tomoya Yamazaki, Tetsuya Hama, Naoki Watanabe, Akira Kouchi
    CHEMISTRY OF MATERIALS 28 (23) 8732 - 8741 0897-4756 2016/12 [Refereed][Not invited]
     
    Multiple pathways in crystal nucleation are now known to be more common than previously predicted; it is, therefore, crucial to understand the early stages of crystallization. Even in relatively simple vapor-phase homogeneous nucleation, the process has significant potential diversity. Here, we experimentally show crystalline Al2O3 nanoparticles forming via precisely two steps in the nucleation process from supersaturated vapor with a moderate cooling rate. In situ FT-IR measurement of nucleation allowed us to observe the formation of Al2O3 nanoparticles. Liquid-like particles first nucleated from the vapor before crystallizing. The crystalline phase was preserved by quenching without further transformation into the most stable alpha-Al2O3 polymorph. The precipitated phase changed from delta-Al2O3 for pure Al2O3 to gamma-Al2O3 or theta-Al2O3 by adding Sb or Cr, respectively. We demonstrate that a two-step process occurs in homogeneous nucleation of refractory materials from supersaturated vapor, which may facilitate polymorphic control in industry formation in space. and improve understanding of cosmic dust
  • Shinnosuke Ishizuka, Yuki Kimura, Tomoya Yamazaki
    JOURNAL OF CRYSTAL GROWTH 450 168 - 173 0022-0248 2016/09 [Refereed][Not invited]
     
    The formation of nanoparticles of titanium oxides by homogeneous nucleation from highly supersaturated vapors was investigated by in situ Fourier transform IR spectroscopy and by observation of the resulting nanoparticles by transmission electron microscopy (TEM). Titanium metal was thermally evaporated in a specially designed chamber under a gaseous atmosphere of oxygen and argon. Nano particles nucleated and subsequently grew as they flew freely through the oxidizing gas atmosphere. Nascent nanoparticles of titanium oxides showed a broad IR absorption band at 10-20 mu m. Subsequently, the cooled nanoparticles showed a sharp crystalline anatase feature at 12.8 mu m. TEM observations showed the formation of spherical anatase nanoparticles. The IR spectral evolution showed that the titanium oxides nucleated as metastable liquid droplets, and that crystallization proceeded through secondary nucleation from the supercooled liquid droplets. This suggests that history of the titanium oxide nanoparticles, such as the temperature and oxidation that they experience after nucleation, determines their polymorphic form. (C) 2016 Elsevier B.V. All rights reserved.
  • A. Kouchi, T. Hama, Y. Kimura, H. Hidaka, R. Escribano, N. Watanabe
    CHEMICAL PHYSICS LETTERS 658 287 - 292 0009-2614 2016/08 [Refereed][Not invited]
     
    A novel method for the formation of amorphous ice involving matrix sublimation has been developed. A CO-rich CO:H2O mixed ice was deposited at 8-10 K under ultra-high vacuum condition, which was then allowed to warm. After the sublimation of matrix CO at 35 K, amorphous ice remained. The amorphous ice formed exhibits a highly porous microscale texture; however, it also rather exhibits a density similar to that of high-density amorphous ice formed under high pressure. Furthermore, unlike conventional vapor-deposited amorphous ice, the amorphous ice is stable up to 140 K, where it transforms directly to cubic ice Ic. (C) 2016 Elsevier B.V. All rights reserved.
  • Yuki Kimura, Kenta Murayama, Tomoya Yamazaki, Takao Maki
    PROGRESS IN CRYSTAL GROWTH AND CHARACTERIZATION OF MATERIALS 62 (2) 400 - 403 0960-8974 2016/06 [Refereed][Not invited]
     
    The principle of interferometers and its applicability to our research on crystal growth can be understood through assembling interferometers. In particular, practical skills such as techniques for assembling interferometers and selecting optical components, which are not covered by general textbooks, can be learned. (C) 2016 Elsevier Ltd. All rights reserved.
  • T. Yamazaki, K. Tsukamoto, I. Yoshizaki, S. Fukuyama, H. Miura, T. Shimaoka, T. Maki, K. Oshi, Y. Kimura
    REVIEW OF SCIENTIFIC INSTRUMENTS 87 (3) 033107  0034-6748 2016/03 [Refereed][Not invited]
     
    To clarify the growth mechanism of a protein crystal, it is essential to measure its growth rate with respect to the supersaturation. We developed a compartment (growth cell) for measuring the growth rate (<0.1 nm s(-1)) of the face of a protein crystal at a controlled supersaturation by interferometry over a period of half a year in space. The growth cell mainly consists of quartz glass, in which the growth solution and a seed crystal are enclosed by capillaries, the screw sample holder, and a helical insert. To avoid the destruction of the cell and the evaporation of the water from the solution inside the cell, we selected the materials for these components with care. The equipment was successfully used to examine the growth of a lysozyme crystal at a controlled supersaturation in space, where convection is negligible because of the microgravity environment, thereby advancing our understanding of the mechanism of protein crystal growth from solution. The technique used to develop the growth cell is useful not only for space experiments but also for kinetic studies of materials with very slow growth and dissolution rates (<10(-3) nm s(-1)). (C) 2016 AIP Publishing LLC.
  • Itsuki Sakon, Shigeyuki Sako, Takashi Onaka, Takaya Nozawa, Yuki Kimura, Takuya Fujiyoshi, Takashi Shimonishi, Fumihiko Usui, Hidenori Takahashi, Ryou Ohsawa, Akira Arai, Makoto Uemura, Takahiro Nagayama, Bon-Chul Koo, Takashi Kozasa
    ASTROPHYSICAL JOURNAL 817 (2) 145  0004-637X 2016/02 [Refereed][Not invited]
     
    We present infrared multi-epoch observations of the dust-forming nova V1280 Sco over similar to 2000 days from the outburst. The temporal evolution of the infrared spectral energy distributions at 1272, 1616, and 1947 days can be explained by the emissions produced by amorphous carbon dust of mass (6.6-8.7) x 10(-8) M-circle dot with a representative grain size of 0.01. mu m and astronomical silicate dust of mass (3.4-4.3) x 10(-7) M-circle dot with a representative grain size of 0.3-0.5 mu m. Both of these dust species travel farther away from the white dwarf without apparent mass evolution throughout those later epochs. The dust formation scenario around V1280 Sco suggested from our analyses is that the amorphous carbon dust is formed in the nova ejecta followed by the formation of silicate dust either in the expanding nova ejecta or as a result of the interaction between the nova wind and the circumstellar medium.
  • Mihiro Takasaki, Yuki Kimura, Tomoya Yamazaki, Yuya Oaki, Hiroaki Imai
    RSC ADVANCES 6 (66) 61346 - 61350 2046-2069 2016 [Refereed][Not invited]
     
    The oriented attachment of calcite, which is a main component of biominerals, was experimentally demonstrated in an aqueous system at ambient temperatures. Calcite nanoblocks similar to 50 nm in size were prepared by carbonation of Ca(OH)(2). One-dimensional (1D) alignment of the calcite nanoblocks was induced at ambient temperatures under a basic condition (pH similar to 12), and single-crystalline rods over 1 mm were then formed through elongation in the c direction. The oriented attachment of the nanoscale building blocks was enhanced by increasing the collision frequency with stirring of the system, but was halted under a neutral pH condition with further carbonation. The controllable non-classical growth mode of calcium carbonate nano-crystals would provide significant information for biogenic and biomimetic mineralization in aqueous solutions.
  • Moe Matsuoka, Tomoki Nakamura, Yuki Kimura, Takahiro Hiroi, Ryosuke Nakamura, Satoshi Okumura, Sho Sasaki
    ICARUS 254 135 - 143 0019-1035 2015/07 [Refereed][Not invited]
     
    We performed pulse-laser irradiation experiments of a primitive meteorite to simulate space weathering by micrometeorite bombardments on C-type asteroids. Pellets of powdered Murchison CM2 chondrite were set in vacuum and exposed to pulse laser with a diameter of 0.5 mm and delivered energies of 5, 10, and 15 mJ. We measured reflectance spectra of unirradiated and irradiated surfaces of the pellets. During analysis the pellet was heated to approximately 100 degrees C and purged in N-2 gas in order to reduce absorption of ambient water. The spectra become darker and bluer with increasing laser energies. Their UV reflectance increases and 0.7- and 3-mu m band depths decrease from 0 to 15 mJ. The spectral bluing observed in our experiments reproduces the bluing occurred during space weathering of C-type asteroids. High-resolution observation by a transmission electron microscope showed that the laser heating causes preferential melting and evaporation in FeS-rich fine-grained portions, which results in dispersion and deposition of numerous FeS-rich amorphous silicate particles 20-1000 nm in size on the surface of the pellet. In addition, at the laser-irradiated but unmelted areas, heat-induced amorphization and decomposition of serpentine occur. These mineralogical changes make the reflectance spectra of the Murchison CM chondrite darker and bluer. (C) 2015 Elsevier Inc. All rights reserved.
  • S. K. Simakov, A. Kouchi, N. N. Mel'nik, V. Scribano, Y. Kimura, T. Hama, N. Suzuki, H. Saito, T. Yoshizawa
    SCIENTIFIC REPORTS 5 10765  2045-2322 2015/06 [Refereed][Not invited]
     
    Most of Earth's diamonds are connected with deep-seated mantle rocks; however, in recent years, mu m-sized diamonds have been found in shallower metamorphic rocks, and the process of shallow-seated diamond formation has become a hotly debated topic. Nanodiamonds occur mainly in chondrite meteorites associated with organic matter and water. They can be synthesized in the stability field of graphite from organic compounds under hydrothermal conditions. Similar physicochemical conditions occur in serpentinite-hosted hydrothermal systems. Herein, we report the first finding of nanodiamonds, primarily of 6 and 10 nm, in Hyblean asphaltene-bearing serpentinite xenoliths (Sicily, Italy). The discovery was made by electron microscopy observations coupled with Raman spectroscopy analyses. The finding reveals new aspects of carbon speciation and diamond formation in shallow crustal settings. Nanodiamonds can grow during the hydrothermal alteration of ultramafic rocks, as well as during the lithogenesis of sediments bearing organic matter.
  • Shinnosuke Ishizuka, Yuki Kimura, Itsuki Sakon
    ASTROPHYSICAL JOURNAL 803 (2) 88  0004-637X 2015/04 [Refereed][Not invited]
     
    We developed a new experimental system for infrared (IR) measurements on free-flying nucleating nanoparticles in situ and applied it to studies on silicate particles. We monitored the condensation of magnesium-bearing silicate nanoparticles from thermally evaporated magnesium and silicon monoxide vapor under an atmosphere of oxygen and argon. The IR spectrum of newly condensed particles showed a spectral feature for non-crystalline magnesium-bearing silicate that is remarkably consistent with the IR spectrum of astronomically observed non-crystalline silicate around oxygen-rich evolved stars. The silicate crystallized at <500 K and eventually developed a high crystallinity. Because of the size effects of nanoparticles, the silicate would be expected to be like a liquid at least during the initial stages of nucleation and growth. Our experimental results therefore suggest decreasing the possible formation temperature of crystalline silicates in dust formation environments with relatively higher pressure.
  • Initial processes of crystallization in mesoscopic region
    Yuki Kimura, Shinnosuke Ishizuka, Kyoko Tanaka, Itsuki Sakon, Shinsuke Takeuchi, Yuko Inatomi
    Space Utilization Research 29 100 - 102 2015 [Not refereed][Not invited]
  • Yuki Sugiura, Kazuo Onuma, Masahiro Nagao, Koichi Momma, Yuki Kimura, Atsushi Yamazaki
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 122 (1428) 679 - 687 1882-0743 2014/08 [Refereed][Not invited]
     
    Vaterite is a crystalline polymorph of calcium carbonate that exhibits low stability in comparison with the other crystalline polymorphs of calcium carbonate. It often assumes a spherical shape. The physical properties of vaterite are utilized in advanced biomaterials such as drug delivery systems (DDSs). The potential application of vaterite in DDSs demands a comprehensive understanding of its dissolution rate as a function of PO4 concentration. Using in situ optical studies, we analyzed the dissolution behavior of vaterite in a simulated PO4-containing biogenic environment. The varying physicality (i. e., the pseudo-physiological conditions) of vaterite were investigated using high-resolution cryogenic transmission electron microscopy and small-angle X-ray scattering. In addition, we measured the PO4/Ca ratio in each part of vaterite spherulites using field-emission scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy and inductively coupled plasma atomic emission spectrometry. We categorized the vaterite spherulites into three parts - the shell, mantle, and core parts - on the basis of their dissolution behavior and PO4 response. The PO4 response to the dissolution dynamics increases toward the outer part, although the adsorption rate decreases in the presence of PO4 and PO4 fluorescence materials. The composition of the shell part was nearly identical to that of ideal vaterite, whereas the inner part exhibited a high C/Ca ratio and a poorly crystalline phase referred to as vaterite-like material. The dissolution rate of each part was 0.23-1.58nm/s (shell), 0.63-3.19nm/s (mantle), and 1.38-5.71 nm/s (core). The vaterite and vaterite-like materials were further identified according to their composition and particle size distribution. (C) 2014 The Ceramic Society of Japan. All rights reserved.
  • Hiromasa Niinomi, Hitoshi Miura, Yuki Kimura, Makio Uwaha, Hiroyasu Katsuno, Shunta Harada, Toru Ujihara, Katsuo Tsukamoto
    CRYSTAL GROWTH & DESIGN 14 (7) 3596 - 3602 1528-7483 2014/07 [Refereed][Not invited]
     
    Chiral symmetry breaking during the chiral crystallization from a sodium chlorate (NaClO3) aqueous solution is an intriguing phenomenon because it provides insights into the prebiotic process of biohomochirality. However, a mechanism of the emergence and amplification of chirality remains controversial, especially for crystallization from highly supersaturated solution, and one of the hypotheses proposed before is a transition toward the homochiral state during the early stages of crystallization. In this contribution, we directly examined the early stage of crystallization by in situ polarized-light microscopy. The observation revealed that achiral crystals, which appear prior to the formation of chiral crystals, transform to the chiral crystal through two kinds of polymorphic transformations: (1) martensitic transformation (MT) and (2) solution-mediated phase transition (SMPT). The SMPT is remarkably facilitated by contact with a chiral crystal. Notably, the resulting enantiomorph through contact-facilitated SMPT is strongly directed by the contacting enantiomorph. In contrast, the MT yields two enantiomorphs in equal probability. The emergence and amplification of chirality has generally been considered to be a result of direct nucleation of a chiral crystal and its fragmentation. In contrast, our observations provide a possibility that the MT and contact-facilitated SMPT play a role for the emergence and amplification of chirality, respectively.
  • Kenta Murayama, Katsuo Tsukamoto, Atul Srivastava, Hitoshi Miura, Etsuro Yokoyama, Yuki Kimura
    CRYSTAL RESEARCH AND TECHNOLOGY 49 (5) 315 - 322 0232-1300 2014/05 [Refereed][Not invited]
     
    The two-dimensional (2D) distributions of surface supersaturation of sodium chlorate crystals with and without solutal convection have been measured by means of a multidirectional interferometry (MDI) technique coupled with the principles of three-dimensional (3D) computer tomography. When solutal convection was present over a top face, the supersaturation at the center of the face was depleted by a factor of >0.9 with reference to the value at the edges of the crystal. When the convection was suppressed using an upside-down geometry, the depletion of supersaturation at the center of the face was much smaller, <0.4. Therefore, the supersaturation difference between the edges and the face center, which is responsible for the morphological stability due to volume diffusion for the solute, becomes less important compared to the effect of convection due to hydrodynamic reasons. This result should give us a key to solve why the crystal quality is sometimes better in convection-free microgravity conditions because of improved stability of a crystal face caused by more homogeneous distribution of supersaturation over the crystal surface.
  • Hiromasa Niinomi, Atsushi Horio, Shunta Harada, Toru Ujihara, Hitoshi Miura, Yuki Kimura, Katsuo Tsukamoto
    JOURNAL OF CRYSTAL GROWTH 394 106 - 111 0022-0248 2014/05 [Refereed][Not invited]
     
    The solubility of the metastable achiral monoclinic phase in NaClO3 crystallization from an aqueous solution, which appears prior to the nucleation of chiral crystals, was successfully measured in the range from 10 degrees C to 23 degrees C. Antisolvent crystallization method was used to obtain metastable crystals for the measurement. The solubility was determined to be about 1.6 times higher than that of the chiral stable cubic phase by observing growth or dissolution of the crystal in aqueous solution at the temperature and concentration of which is predetermined. (C) 2014 Elsevier B.V. All rights reserved.
  • Yuki Kimura, Hiromasa Niinomi, Katsuo Tsukamoto, Juan M. Garcia-Ruiz
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 136 (5) 1762 - 1765 0002-7863 2014/02 [Refereed][Not invited]
     
    The formation of crystals from solution requires the initial self-assembly of units of matter into stable periodic structures reaching a critical size. The early stages of this process, called nucleation, are very difficult to visualize. Here we describe a novel method that allows real time observation of the dynamics of nucleation and dissolution of sodium chlorate clusters in an ionic liquid solution using in situ transmission electron microscopy. Using ionic liquids as solvent circumvents the problem of evaporation and charging, while the nucleation frequency was reduced by using saturated solutions. We observe simultaneous formation and dissolution of prenucleation clusters, suggesting that high-density fluctuations leading to solid cluster formation exist even under equilibrium conditions. In situ electron diffraction patterns reveal the simultaneous formation of crystalline nuclei of two polymorphic structures, the stable cubic phase and the metastable monoclinic phase, during the earliest stages of nucleation. These results demonstrate that molecules in solution can form clusters of different polymorphic phases independently of their respective solubility.
  • Yuki Kimura, Hiromasa Niinomi, Katsuo Tsukamoto, Juan M. Garcia-Ruiz
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 136 (5) 1762 - 1765 0002-7863 2014/02 [Not refereed][Not invited]
     
    The formation of crystals from solution requires the initial self-assembly of units of matter into stable periodic structures reaching a critical size. The early stages of this process, called nucleation, are very difficult to visualize. Here we describe a novel method that allows real time observation of the dynamics of nucleation and dissolution of sodium chlorate clusters in an ionic liquid solution using in situ transmission electron microscopy. Using ionic liquids as solvent circumvents the problem of evaporation and charging, while the nucleation frequency was reduced by using saturated solutions. We observe simultaneous formation and dissolution of prenucleation clusters, suggesting that high-density fluctuations leading to solid cluster formation exist even under equilibrium conditions. In situ electron diffraction patterns reveal the simultaneous formation of crystalline nuclei of two polymorphic structures, the stable cubic phase and the metastable monoclinic phase, during the earliest stages of nucleation. These results demonstrate that molecules in solution can form clusters of different polymorphic phases independently of their respective solubility.
  • Nucleation Experiment of Cosmic Dust under Microgravity using a Sounding Rocket S-520-28
    Yuki Kimura
    Int. J. Microgravity Sci. Appl. 31 130 - 136 2014 [Refereed][Not invited]
  • Y. Inatomi, Y. Kimura, K. Tsukamoto, Y. Takagi, S. Takeuchi, N. Ishii
    Transactions of the Japan Society for Aeronautical and Space Sciences, Aerospace Technology Japan 12 Th_31 - Th_34 2014 [Refereed][Not invited]
  • Hiromasa Niinomi, Tomoya Yamazaki, Shunta Harada, Toru Ujihara, Hitoshi Miura, Yuki Kimura, Takahiro Kuribayashi, Makio Uwaha, Katsuo Tsukamoto
    CRYSTAL GROWTH & DESIGN 13 (12) 5188 - 5192 1528-7483 2013/12 [Refereed][Not invited]
     
    Chiral symmetry breaking in NaClO3 crystallization from an aqueous solution with perturbations has been of great interest. To understand the mechanism, several models focusing on the early stage of the crystallization have been proposed. However, they are ambiguous because the early stage has been barely explored directly. Here, we investigate the early stages of the crystallization process driven by droplet evaporation using a combination of direct in situ microscopic observations and cryogenic single-crystal XRD experiments. We demonstrate that an achiral crystal having P2(1)/a symmetry, which is newly discovered for a solution growth, first appears in the droplet and then transforms into the chiral crystals. Additionally, determination of the lattice constants by XRD experiments (a = 8.42 angstrom, b = 5.26 angstrom, c = 6.70 angstrom, beta = 109.71 degrees) revealed that the achiral phase should be identical to Phase III (a = 8.78 angstrom, b = 5.17 angstrom, c = 6.83 angstrom, beta = 110 degrees), which is a high-temperature phase from a melt growth of NaClO3. We advocate further assessment of the achiral crystal and a new pathway for the formation of chiral crystals via crystalline phase transition from achiral Phase III.
  • Arnold Gucsik, Taro Endo, Hirotsugu Nishido, Kiyotaka Ninagawa, Masahiro Kayama, Szaniszlo Berczi, Szabolcs Nagy, Peter Abraham, Yuki Kimura, Hitoshi Miura, Ildiko Gyollai, Irakli Simonia, Peter Rozsa, Jozsef Posta, Daniel Apai, Krisztian Mihalyi, Mihaly Nagy, Ulrich Ott
    METEORITICS & PLANETARY SCIENCE 48 (12) 2577 - 2596 1086-9379 2013/12 [Refereed][Not invited]
     
    Highly forsteritic olivine (Fo: 99.2-99.7) in the Kaba meteorite emits bright cathodoluminescence (CL). CL spectra of red luminescent forsterite grains have two broad emission bands at approximately 630nm (impurity center of divalent Mn ions) in the red region and above 700nm (trivalent Cr ions) in the red-IR region. The cores of the grains show CL blue luminescence giving a characteristic broad band emission at 400nm, also associated with minor red emissions related to Mn and Cr ions. CL color variation of Kaba forsterite is attributed to structural defects. Electron probe microanalyzer (EPMA) analysis shows concentrations of Ca, Al, and Ti in the center of the forsterite grain. The migration of diffusible ions of Mn, Cr, and Fe to the rim of the Kaba meteoritic forsterite was controlled by the hydrothermal alteration at relatively low temperature (estimated at about 250 degrees C), while Ca and Al ions might still lie in the core. A very unusual phase of FeO (wustite) was also observed, which may be a terrestrial alteration product of FeNi-metal.
  • Yuki Kimura, Takeshi Sato, Norihiro Nakamura, Jun Nozawa, Tomoki Nakamura, Katsuo Tsukamoto, Kazuo Yamamoto
    Nature Communications 4 2649  2041-1723 2013/10/22 [Refereed][Not invited]
     
    The majority of water has vanished from modern meteorites, yet there remain signatures of water on ancient asteroids. How and when water disappeared from the asteroids is important, because the final fluid-concentrated chemical species played critical roles in the early evolution of organics and in the final minerals in meteorites. Here we show evidence of vestigial traces of water based on a nanometre-scale palaeomagnetic method, applying electron holography to the framboids in the Tagish Lake meteorite. The framboids are colloidal crystals composed of three-dimensionally ordered magnetite nanoparticles and therefore are only able to form against the repulsive force induced by the surface charge of the magnetite as a water droplet parches in microgravity. We demonstrate that the magnetites have a flux closure vortex structure, a unique magnetic configuration in nature that permits the formation of colloidal crystals just before exhaustion of water from a local system within a hydrous asteroid.
  • Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Katsuo Tsukamoto, Atsushi Yamazaki
    AMERICAN MINERALOGIST 98 (1) 262 - 270 0003-004X 2013/01 [Not refereed][Not invited]
     
    Phase transformation of amorphous calcium carbonate (ACC) into vaterite and its subsequent stability was investigated at a constant pH (similar to 8.2), ionic strength, and temperature that simulated the biological environment. Solutions containing the same concentrations of CaCl2, Na2CO3, and tris(hydroxymethyl)aminomethane buffer and various concentrations of PO4 (0-62.5 mu M) were prepared, and precipitates in the solutions were sampled at a constant interval to observe the morphology and type of calcium carbonate polymorphs that appeared. The change in the Ca-ion concentration over time, which served as a guide for phase transformation of ACC into crystalline phases, was measured in relation to the PO4 concentration. The starting time of phase transformation was at the minimum point when the concentration was similar to 2-3 mu M. Vaterite spherulites consisting of needle-like crystals (0.5-2 mu m in length) formed only in this PO4 range and survived the experimental procedure (similar to 2.5 h). In contrast, the starting time of phase transformation increased exponentially with the PO4 concentration when it was higher than 5 mu M. The vaterite spherulites and calcite crystals co-precipitated, and both polymorphs grew over time. The PO4 was shown to be an accelerator for phase transformation from ACC into vaterite at low concentrations (Ca/PO4 molar ratio <3000) and an inhibitor for transformation at high concentrations. We investigated the kinetics of vaterite formation in the presence of PO4 and derived an advanced concept for cluster-based phase transformation. This investigation showed that the appearance and stability of calcium carbonate polymorphs is easily controlled by adjusting the PO4 concentration.
  • Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Katsuo Tsukamoto, Atsushi Yamazaki
    AMERICAN MINERALOGIST 98 (1) 262 - 270 0003-004X 2013/01 [Not refereed][Not invited]
     
    Phase transformation of amorphous calcium carbonate (ACC) into vaterite and its subsequent stability was investigated at a constant pH (similar to 8.2), ionic strength, and temperature that simulated the biological environment. Solutions containing the same concentrations of CaCl2, Na2CO3, and tris(hydroxymethyl)aminomethane buffer and various concentrations of PO4 (0-62.5 mu M) were prepared, and precipitates in the solutions were sampled at a constant interval to observe the morphology and type of calcium carbonate polymorphs that appeared. The change in the Ca-ion concentration over time, which served as a guide for phase transformation of ACC into crystalline phases, was measured in relation to the PO4 concentration. The starting time of phase transformation was at the minimum point when the concentration was similar to 2-3 mu M. Vaterite spherulites consisting of needle-like crystals (0.5-2 mu m in length) formed only in this PO4 range and survived the experimental procedure (similar to 2.5 h). In contrast, the starting time of phase transformation increased exponentially with the PO4 concentration when it was higher than 5 mu M. The vaterite spherulites and calcite crystals co-precipitated, and both polymorphs grew over time. The PO4 was shown to be an accelerator for phase transformation from ACC into vaterite at low concentrations (Ca/PO4 molar ratio <3000) and an inhibitor for transformation at high concentrations. We investigated the kinetics of vaterite formation in the presence of PO4 and derived an advanced concept for cluster-based phase transformation. This investigation showed that the appearance and stability of calcium carbonate polymorphs is easily controlled by adjusting the PO4 concentration.
  • Nakamura T, Noguchi T, Kimura Y, Hiroi T, Ahn I, Lee J. I, Sasaki S
    Meteoritics & Planetary Science 48 A258  2013 [Refereed][Not invited]
  • Tetsuya Hama, Kazuaki Kuwahata, Naoki Watanabe, Akira Kouchi, Yuki Kimura, Takeshi Chigai, Valerio Pirronello
    ASTROPHYSICAL JOURNAL 757 (2) 185 - 196 0004-637X 2012/10 [Not refereed][Not invited]
     
    To understand elementary processes leading to H-2 formation, and the hydrogenation and deuteration reactions of adsorbed species on dust grains in dense clouds, we experimentally investigated the diffusion of atomic hydrogen and deuterium on amorphous solidwater (ASW) at temperatures of 8-15 K. The present study extended our previous study for selective detections of H and D atoms, and of H-2 (J = 0 and 1) and D-2 (J = 0 and 1) molecules adsorbed on ASW using both photo-stimulated desorption and resonance-enhanced multiphoton ionization, to investigate potential sites on ASW for diffusion, recombination dynamics, and the diffusion mechanism of H and D atoms. Our results demonstrate that the ASW surface contains various potential sites that can be categorized into at least three groups: very shallow, middle-, and deep-potential sites, with diffusion activation energies of <= 18, 22 (23 meV for D atoms), and >= 30 meV, respectively. The present study pictured the outline of H-2 formation on cosmic ice dust at low temperatures: H atoms landing on the dust will diffuse rapidly at the abundant shallow and middle sites on ASW, and finally become trapped at deep sites. The H atoms that arrive next recombine with such trapped H atoms to yield H-2 molecules. The small isotopic difference between the diffusion of H and D atoms on ASW indicates that the diffusion mechanism can be explained by thermal hopping, at least at middle-potential sites.
  • HAMA TETSUYA, KUWAHATA KAZUAKI, WATANABE NAOKI, KOUCHI AKIRA, KIMURA YUKI, CHIGAI TAKESHI, PIRRONELLO VALERIO
    Astrophys J 757 (2,Pt.1) 185,1-185,12  0004-637X 2012/10/01 [Not refereed][Not invited]
  • Tetsuya Hama, Kazuaki Kuwahata, Naoki Watanabe, Akira Kouchi, Yuki Kimura, Takeshi Chigai, Valerio Pirronello
    ASTROPHYSICAL JOURNAL 757 (2) 0004-637X 2012/10 [Refereed][Not invited]
     
    To understand elementary processes leading to H-2 formation, and the hydrogenation and deuteration reactions of adsorbed species on dust grains in dense clouds, we experimentally investigated the diffusion of atomic hydrogen and deuterium on amorphous solidwater (ASW) at temperatures of 8-15 K. The present study extended our previous study for selective detections of H and D atoms, and of H-2 (J = 0 and 1) and D-2 (J = 0 and 1) molecules adsorbed on ASW using both photo-stimulated desorption and resonance-enhanced multiphoton ionization, to investigate potential sites on ASW for diffusion, recombination dynamics, and the diffusion mechanism of H and D atoms. Our results demonstrate that the ASW surface contains various potential sites that can be categorized into at least three groups: very shallow, middle-, and deep-potential sites, with diffusion activation energies of <= 18, 22 (23 meV for D atoms), and >= 30 meV, respectively. The present study pictured the outline of H-2 formation on cosmic ice dust at low temperatures: H atoms landing on the dust will diffuse rapidly at the abundant shallow and middle sites on ASW, and finally become trapped at deep sites. The H atoms that arrive next recombine with such trapped H atoms to yield H-2 molecules. The small isotopic difference between the diffusion of H and D atoms on ASW indicates that the diffusion mechanism can be explained by thermal hopping, at least at middle-potential sites.
  • KIMURA YUKI, INATOMI YUKO, TANAKA KYOKO, MAKI TAKAO, MIURA HITOSHI, SAKON ITSUKI, NOZAWA TAKAYA, TSUKAMOTO KATSUO
    日本結晶成長学会誌 39 (2) 68 - 74 0385-6275 2012/07 [Not refereed][Not invited]
  • Y. Kimura, K. K. Tanaka, H. Miura, K. Tsukamoto
    CRYSTAL GROWTH & DESIGN 12 (6) 3278 - 3284 1528-7483 2012/06 [Not refereed][Not invited]
     
    We examined the homogeneous condensation of thermally evaporated manganese vapor in an atmosphere of argon gas and determined the temperature and concentration during homogeneous nucleation in the vapor phase by using a Mach-Zehnder type interferometer. Condensation occurred at 660-785 K below the equilibrium temperature and the degree of supersaturation was as high as similar to 5 x 10(4). Using the condensation temperature and size of the condensed particles, which were measured by transmission electron microscopy, we determined the surface free energy and sticking coefficient of Mn at 1106 +/- 50 K to be 1.55 +/- 0.10 J/m(2) and 0.39(-0.20)(+0.39) respectively, by classical nucleation theory (CNT) and 1.57 +/- 0.35 J/m(2) and 0.42(-0.21)(+0.42), respectively, by a semiphenomenological theory (SP). The nucleation theories predict that the critical nucleus contains only three and six atoms for CNT and SP, respectively, which are fewer than the number of atoms in a unit cell of Mn. This suggests that the polymorphic form of manganese is decided during particle growth rather than during nucleation from the vapor phase.
  • A. Gucsik, K. Tsukamoto, H. Nishido, H. Miura, M. Kayama, K. Ninagawa, Y. Kimura
    JOURNAL OF LUMINESCENCE 132 (4) 1041 - 1047 0022-2313 2012/04 [Not refereed][Not invited]
     
    Cathodoluminescence (CL) of laboratory forsterite chondrules has been characterized to clarify the formation process of chondrules and related mechanism of the crystal growth in a supercooled melt. Color CL image of the experimentally grown forsterite exhibits significant blue luminescence in the main branches of the interior structure of lab-chondrule, which reflects to the anisotropy of crystallization. A new CL band centered at 450-525 nm (2.76-2.36 eV) in blue to green region might be assigned to a microdefect-related center, which is a diagnostic peak for the forsterite that was formed due to the rapid growth as high as similar to 10 mm/s or higher from a supercooled melt. (C) 2011 Elsevier B.V. All rights reserved.
  • Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto
    JOURNAL OF CRYSTAL GROWTH 332 (1) 58 - 67 0022-0248 2011/10 [Not refereed][Not invited]
     
    Nucleation of amorphous calcium phosphate (ACP) and its phase transformation with a decrease in solution pH were investigated at a constant temperature of 32 degrees C. A solution containing a mixture of CaCl2 and KH2PO4 was prepared (initial pH=7.7), and a drop was sampled at a constant interval to observe the morphological evolution of the precipitates that formed in the solution. A gel-like solution structure formed immediately after mixing and contained a small amount of sea-urchin-like ACP spherulites (3-20 mu m in size). These spherulites consisted of 1.5-10-mu m-long flexible needles that formed simultaneously with numerous ACP spherical particles. They first transformed into beta-tri calcium phosphate-like material (called "pseudo beta-TCP") and then into single crystals of octacalcium phosphate (OCP) without dissolution. The flexible needles in the spherulites changed into blade springs, then into flexible plates, and finally into rigid plates during the transformation. The OCP structure appeared in the pseudo beta-TCP plates and gradually substituted for the beta-TCP structure over time. The macroscopic spherulite morphology of the initial ACP remained unchanged during the phase transformation, suggesting that OCP is a pseudomorph of ACP. This feature was observed only when the ACP spherulites formed in the initial solution. Fiber-like aggregates consisting of beta-TCP single crystals nucleated around the ACP spherical particles and grew over time. They survived until the final stage of the reaction, and OCP polycrystals formed in the mixture of beta-TCP and ACP spheres. The OCP polycrystals gradually substituted for the ACP spheres without phase transformation of beta-TCP into OCP. (C) 2011 Elsevier B.V. All rights reserved.
  • Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto
    JOURNAL OF CRYSTAL GROWTH 332 (1) 58 - 67 0022-0248 2011/10 [Not refereed][Not invited]
     
    Nucleation of amorphous calcium phosphate (ACP) and its phase transformation with a decrease in solution pH were investigated at a constant temperature of 32 degrees C. A solution containing a mixture of CaCl2 and KH2PO4 was prepared (initial pH=7.7), and a drop was sampled at a constant interval to observe the morphological evolution of the precipitates that formed in the solution. A gel-like solution structure formed immediately after mixing and contained a small amount of sea-urchin-like ACP spherulites (3-20 mu m in size). These spherulites consisted of 1.5-10-mu m-long flexible needles that formed simultaneously with numerous ACP spherical particles. They first transformed into beta-tri calcium phosphate-like material (called "pseudo beta-TCP") and then into single crystals of octacalcium phosphate (OCP) without dissolution. The flexible needles in the spherulites changed into blade springs, then into flexible plates, and finally into rigid plates during the transformation. The OCP structure appeared in the pseudo beta-TCP plates and gradually substituted for the beta-TCP structure over time. The macroscopic spherulite morphology of the initial ACP remained unchanged during the phase transformation, suggesting that OCP is a pseudomorph of ACP. This feature was observed only when the ACP spherulites formed in the initial solution. Fiber-like aggregates consisting of beta-TCP single crystals nucleated around the ACP spherical particles and grew over time. They survived until the final stage of the reaction, and OCP polycrystals formed in the mixture of beta-TCP and ACP spheres. The OCP polycrystals gradually substituted for the ACP spheres without phase transformation of beta-TCP into OCP. (C) 2011 Elsevier B.V. All rights reserved.
  • Jun Nozawa, Katsuo Tsukamoto, Willem van Enckevort, Tomoki Nakamura, Yuki Kimura, Hitoshi Miura, Hisao Satoh, Ken Nagashima, Makoto Konoto
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 133 (23) 8782 - 8785 0002-7863 2011/06 [Refereed][Not invited]
     
    Three-dimensional colloidal crystals made of ferromagnetic particles, such as magnetite (Fe(3)O(4)), cannot be synthesized in principle because of the strong attractive magnetic interaction. However, we discovered colloidal crystals composed of polyhedral magnetite nanocrystallites of uniform size in the range of a few hundred nanometers in the Tagish Lake meteorite. Those colloidal crystals were formed 4.6 billion years ago and thus are much older than natural colloidal crystals on earth, such as opals, which formed about 100 million years ago.(1) We found that the size of each individual magnetite particle determines its morphology, which in turn plays an important role in deciding the packing structure of the colloidal crystals. We also hypothesize that each particle has a flux-closed magnetic domain structure, which reduces the interparticle magnetic force significantly.
  • Jun Nozawa, Katsuo Tsukamoto, Willem van Enckevort, Tomoki Nakamura, Yuki Kimura, Hitoshi Miura, Hisao Satoh, Ken Nagashima, Makoto Konoto
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 133 (23) 8782 - 8785 0002-7863 2011/06 [Not refereed][Not invited]
     
    Three-dimensional colloidal crystals made of ferromagnetic particles, such as magnetite (Fe(3)O(4)), cannot be synthesized in principle because of the strong attractive magnetic interaction. However, we discovered colloidal crystals composed of polyhedral magnetite nanocrystallites of uniform size in the range of a few hundred nanometers in the Tagish Lake meteorite. Those colloidal crystals were formed 4.6 billion years ago and thus are much older than natural colloidal crystals on earth, such as opals, which formed about 100 million years ago.(1) We found that the size of each individual magnetite particle determines its morphology, which in turn plays an important role in deciding the packing structure of the colloidal crystals. We also hypothesize that each particle has a flux-closed magnetic domain structure, which reduces the interparticle magnetic force significantly.
  • Jun Nozawa, Katsuo Tsukamoto, Willem van Enckevort, Tomoki Nakamura, Yuki Kimura, Hitoshi Miura, Hisao Satoh, Ken Nagashima, Makoto Konoto
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 133 (23) 8782 - 8785 0002-7863 2011/06 [Not refereed][Not invited]
     
    Three-dimensional colloidal crystals made of ferromagnetic particles, such as magnetite (Fe(3)O(4)), cannot be synthesized in principle because of the strong attractive magnetic interaction. However, we discovered colloidal crystals composed of polyhedral magnetite nanocrystallites of uniform size in the range of a few hundred nanometers in the Tagish Lake meteorite. Those colloidal crystals were formed 4.6 billion years ago and thus are much older than natural colloidal crystals on earth, such as opals, which formed about 100 million years ago.(1) We found that the size of each individual magnetite particle determines its morphology, which in turn plays an important role in deciding the packing structure of the colloidal crystals. We also hypothesize that each particle has a flux-closed magnetic domain structure, which reduces the interparticle magnetic force significantly.
  • Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto, Chaorong Li, Takao Maki
    JOURNAL OF CRYSTAL GROWTH 316 (1) 196 - 200 0022-0248 2011/02 [Not refereed][Not invited]
     
    To investigate the homogeneous nucleation and growth process of nanoparticles in vapor phase, interferometric observation was attempted for the first time to the gas evaporation method, which has been a commonly accepted physical production method of nanoparticles. Tungsten oxide was evaporated by electrical heating of a tungsten wire in a mixture gas of Ar and O-2. WO3 nanoparticles were formed via homogeneous nucleation and growth during a gas cools following a thermal convection produced by the evaporation source. The degree of supersaturation for nucleation was extremely high, 6.6 x 10(6), which was determined from the interferogram. Surface free energy of WO3 at 1100 K was calculated based on the classical nucleation theory and was 1.38 x 10(3) erg cm(-2), which is within the reported values. A part of the difference between actual formation rate of produced nanoparticles, which were determined based on a transmission electron microscope, and calculated values based on the classical nucleation theory were well explained if we adopt the idea of coalescence growth. (C) 2011 Elsevier B.V. All rights reserved.
  • Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto, Chaorong Li, Takao Maki
    JOURNAL OF CRYSTAL GROWTH 316 (1) 196 - 200 0022-0248 2011/02 [Not refereed][Not invited]
     
    To investigate the homogeneous nucleation and growth process of nanoparticles in vapor phase, interferometric observation was attempted for the first time to the gas evaporation method, which has been a commonly accepted physical production method of nanoparticles. Tungsten oxide was evaporated by electrical heating of a tungsten wire in a mixture gas of Ar and O-2. WO3 nanoparticles were formed via homogeneous nucleation and growth during a gas cools following a thermal convection produced by the evaporation source. The degree of supersaturation for nucleation was extremely high, 6.6 x 10(6), which was determined from the interferogram. Surface free energy of WO3 at 1100 K was calculated based on the classical nucleation theory and was 1.38 x 10(3) erg cm(-2), which is within the reported values. A part of the difference between actual formation rate of produced nanoparticles, which were determined based on a transmission electron microscope, and calculated values based on the classical nucleation theory were well explained if we adopt the idea of coalescence growth. (C) 2011 Elsevier B.V. All rights reserved.
  • Yuki Kimura, Joseph A. Nuth, Natasha M. Johnson, Kevin D. Farmer, Kenneth P. Roberts, Syed R. Hussaini
    NANOSCIENCE AND NANOTECHNOLOGY LETTERS 3 (1) 4 - 10 1941-4900 2011/02 [Refereed][Not invited]
     
    Stacked-cup carbon nanotubes were formed by either Fischer-Tropsch type or Haber-Bosch type reactions in a metal free system. Graphite particles were used as the catalyst. The samples were heated at 600 degrees C in a gas mixture of CO 75 Torr, N-2 75 Torr and H-2 550 Torr for three days. Transmission electron microscope analysis of the catalyst surface at the completion of the experiment recognized the growth of nanotubes. They were 10-50 nm in diameter and similar to 1 mu m in length. They had a hollow channel of 5-20 nm in the center. The nanotubes may have grown on graphite surfaces by the CO disproportionation reaction and the surface tension of the carbon nucleus may have determined the diameter. Although, generally, the diameter of a carbon nanotube depends on the size of the catalytic particles, the diameter of the nanotubes on graphite particles was independent of the particle size and significantly confined within a narrow range compared with that produced using catalytic amorphous iron-silicate nanoparticles. Therefore, they must have an unknown formation process that is different than the generally accepted mechanism.
  • Yuki Kimura, Joseph A. Nuth, Katsuo Tsukamoto, Chihiro Kaito
    METEORITICS & PLANETARY SCIENCE 46 (1) 92 - 102 1086-9379 2011/01 [Not refereed][Not invited]
     
    Exothermic reactions during the annealing of laboratory synthesized amorphous magnesium-bearing silicate particles used as grain analogs of cosmic dust were detected by differential scanning calorimetry (DSC) in air. With infrared spectroscopy and transmission electron microscopy, we show that cosmic dust could possibly undergo fusion to larger particles, with oxidation of magnesium silicide and crystallization of forsterite as exothermic reactions in the early solar system. The reactions begin at approximately 425, approximately 625, and approximately 1000 K, respectively, and the reaction energies (enthalpies) are at least 727, 4151, and 160.22 J g-1, respectively. During the crystallization of forsterite particles, the spectral evolution of the 10 mu m feature from amorphous to crystalline was observed to begin at lower temperature than the crystallization temperature of 1003 K. During spectral evolution at lower temperature, nucleation and/or the formation of nanocrystallites of forsterite at the surface of the grain analogs was observed.
  • Interferometric observation of temperature distributions in the smoke experiment
    Y. Kimura, K. Tsukamoto
    J. Jpn. Soc. Microgravity Appl 2011 [Not refereed][Not invited]
  • Yuki Kimura, Joseph A. Nuth, Katsuo Tsukamoto, Chihiro Kaito
    METEORITICS & PLANETARY SCIENCE 46 (1) 92 - 102 1086-9379 2011/01 [Not refereed][Not invited]
     
    Exothermic reactions during the annealing of laboratory synthesized amorphous magnesium-bearing silicate particles used as grain analogs of cosmic dust were detected by differential scanning calorimetry (DSC) in air. With infrared spectroscopy and transmission electron microscopy, we show that cosmic dust could possibly undergo fusion to larger particles, with oxidation of magnesium silicide and crystallization of forsterite as exothermic reactions in the early solar system. The reactions begin at approximately 425, approximately 625, and approximately 1000 K, respectively, and the reaction energies (enthalpies) are at least 727, 4151, and 160.22 J g-1, respectively. During the crystallization of forsterite particles, the spectral evolution of the 10 mu m feature from amorphous to crystalline was observed to begin at lower temperature than the crystallization temperature of 1003 K. During spectral evolution at lower temperature, nucleation and/or the formation of nanocrystallites of forsterite at the surface of the grain analogs was observed.
  • Yuki Kimura, Joseph A. Nuth, Katsuo Tsukamoto, Chihiro Kaito
    METEORITICS & PLANETARY SCIENCE 46 (1) 92 - 102 1086-9379 2011/01 [Refereed][Not invited]
     
    Exothermic reactions during the annealing of laboratory synthesized amorphous magnesium-bearing silicate particles used as grain analogs of cosmic dust were detected by differential scanning calorimetry (DSC) in air. With infrared spectroscopy and transmission electron microscopy, we show that cosmic dust could possibly undergo fusion to larger particles, with oxidation of magnesium silicide and crystallization of forsterite as exothermic reactions in the early solar system. The reactions begin at approximately 425, approximately 625, and approximately 1000 K, respectively, and the reaction energies (enthalpies) are at least 727, 4151, and 160.22 J g-1, respectively. During the crystallization of forsterite particles, the spectral evolution of the 10 mu m feature from amorphous to crystalline was observed to begin at lower temperature than the crystallization temperature of 1003 K. During spectral evolution at lower temperature, nucleation and/or the formation of nanocrystallites of forsterite at the surface of the grain analogs was observed.
  • Kimura Y, Tanaka K. K, Miura H, Tsukamoto K
    Meteoritics & Planetary Science 46 A124  2011 [Refereed][Not invited]
  • WATANABE NAOKI, KIMURA YUKI, KOUCHI AKIRA, CHIGAI TAKESHI, HAMA TETSUYA, PIRRONELLO VALERIO
    Astrophys J 714 (2,Pt.2) L233-L237  0004-637X 2010/05/10 [Not refereed][Not invited]
  • Joseph A. Nuth, Yuki Kimura, Christopher Lucas, Frank Ferguson, Natasha M. Johnson
    ASTROPHYSICAL JOURNAL LETTERS 710 (1) L98 - L101 2010/02 [Not refereed][Not invited]
     
    It has been suggested that carbonaceous grains are efficiently destroyed in the interstellar medium and must either reform in situ at very low pressures and temperatures or in an alternative environment more conducive to grain growth. Graphite whiskers have been discovered associated with high-temperature phases in meteorites such as calcium aluminum inclusions and chondrules, and it has been suggested that the expulsion of such material from protostellar nebulae could significantly affect the optical properties of the average interstellar grain population. We have experimentally studied the potential for Fischer-Tropsch and Haber-Bosch type reactions to produce organic materials in protostellar systems from the abundant H(2), CO, and N(2) reacting on the surfaces of available silicate grains. When graphite grains are repeatedly exposed to H(2), CO, and N(2) at 875 K abundant graphite whiskers are observed to form on or from the surfaces of the graphite grains. In a dense, turbulent nebula, such extended whiskers are very likely to be broken off, and fragments could be ejected either in polar jets or by photon pressure after transport to the outer reaches of the nebula.
  • Joseph A. Nuth, Yuki Kimura, Christopher Lucas, Frank Ferguson, Natasha M. Johnson
    ASTROPHYSICAL JOURNAL LETTERS 710 (1) L98 - L101 0004-637X 2010/02 [Not refereed][Not invited]
     
    It has been suggested that carbonaceous grains are efficiently destroyed in the interstellar medium and must either reform in situ at very low pressures and temperatures or in an alternative environment more conducive to grain growth. Graphite whiskers have been discovered associated with high-temperature phases in meteorites such as calcium aluminum inclusions and chondrules, and it has been suggested that the expulsion of such material from protostellar nebulae could significantly affect the optical properties of the average interstellar grain population. We have experimentally studied the potential for Fischer-Tropsch and Haber-Bosch type reactions to produce organic materials in protostellar systems from the abundant H(2), CO, and N(2) reacting on the surfaces of available silicate grains. When graphite grains are repeatedly exposed to H(2), CO, and N(2) at 875 K abundant graphite whiskers are observed to form on or from the surfaces of the graphite grains. In a dense, turbulent nebula, such extended whiskers are very likely to be broken off, and fragments could be ejected either in polar jets or by photon pressure after transport to the outer reaches of the nebula.
  • Midori Saito, Itsuki Sakon, Chihiro Kaito, Yuki Kimura
    EARTH PLANETS AND SPACE 62 (1) 81 - 90 1343-8832 2010 [Not refereed][Not invited]
     
    It has been known for sonic time that the properties of a material are changed in nanometer size. Since it is nontrivial that polycyclic aromatic hydrocarbon (PAH) grains at the nanometer scale show similar properties with that of macroscopic scale, PAH grains were synthesized by a gas evaporation method and were analyzed using a transmission electron microscope and their UV-Vis and mid-IR spectra were Measured. Results from these experiments showed that condensed anthracene grains from the gas phase had a planar form and showed similar infrared peaks compared to anthracene molecules, but With somewhat wider bands and different relative intensities. Sonic new features were also observed. The anthracene molecules formed photodimer ill their grain and showed different infrared features after UV irradiation. This Would be the first report concerning nanometer-sized PAH grains.
  • N. Watanabe, Y. Kimura, A. Kouchi, T. Chigai, T. Hama, V. Pirronello
    The Astrophysical Journal Letters 714 L233-L237  2010 [Not refereed][Not invited]
  • Synthesis of stacked-cup carbon nanotubes in a metal free low temperature system
    Y. Kimura, J. A. Nuth III, N. M. Johnson, K. D. Farmer, K. P. Roberts, S. R. Hussaini
    Nanoscience and Nanotechnology Letters 3 1 - 7 2010 [Not refereed][Not invited]
  • Midori Saito, Itsuki Sakon, Chihiro Kaito, Yuki Kimura
    EARTH PLANETS AND SPACE 62 (1) 81 - 90 1343-8832 2010 [Not refereed][Not invited]
     
    It has been known for sonic time that the properties of a material are changed in nanometer size. Since it is nontrivial that polycyclic aromatic hydrocarbon (PAH) grains at the nanometer scale show similar properties with that of macroscopic scale, PAH grains were synthesized by a gas evaporation method and were analyzed using a transmission electron microscope and their UV-Vis and mid-IR spectra were Measured. Results from these experiments showed that condensed anthracene grains from the gas phase had a planar form and showed similar infrared peaks compared to anthracene molecules, but With somewhat wider bands and different relative intensities. Sonic new features were also observed. The anthracene molecules formed photodimer ill their grain and showed different infrared features after UV irradiation. This Would be the first report concerning nanometer-sized PAH grains.
  • Watanabe Naoki, Kouchi Akira, Hidaka Hiroshi, Kimura Yuki, Hama Tetsuya
    Abstracts of Papers of the American Chemical Society 239 2010 [Refereed][Not invited]
  • Jun Nozawa, Katsuo Tsukamoto, Hidekazu Kobatake, Junya Yamada, Hisao Satoh, Ken Nagashima, Hitoshi Miura, Yuki Kimura
    ICARUS 204 (2) 681 - 686 0019-1035 2009/12 [Not refereed][Not invited]
     
    By means of nanoscale surface observation, we have proposed a new approach for investigating fine crystals of cosmic materials to reveal their origin and growth conditions. Several different morphologies of polyhedral fine olivines with faceted faces have been found in Allende carbonaceous chondrite (4.5 byr in geochronological age). In the present work, molecular level topography of the faceted matrix olivine by Atomic Force Microscopy (AFM) has Successfully been performed, The matrix olivine found to have preserved growth step pattern on its surface even though quite long time has passed since they formed in the early Solar System. The Surface pattern Suggests that the faceted matrix olivine could have been condensed from the gas phase, and possibly that these olivine crystals had continued to grow under a rapid cooling condition (0.1-1 K s(-1)). The estimated cooling rate agrees well with predictions based on hypothetical rapid heating and cooling events such as shock wave heating. (C) 2009 Elsevier Inc. All rights reserved.
  • Midori Saito, Yuki Kimura
    ASTROPHYSICAL JOURNAL LETTERS 703 (2) L147 - L151 2009/10 [Not refereed][Not invited]
     
    Analogs of organic hollow globules, which have been found in carbonaceous chondrite meteorites and interplanetary dust particles, were synthesized in our laboratory from benzene and anthracene using plasma. Our results suggest that organic globules could be made from aromatic rings in circumstellar envelopes around evolved stars. The hollow interior could be formed by coagulation of vacancies, formed by electronic excitation and/or knock-out of carbon atoms following irradiation by plasma particles such as protons and He(+) ions. This experimental result suggests that organic globules are possibly the final products in the evolution of carbonaceous matter from acetylene and benzene to polycyclic aromatic hydrocarbons in ejecta gas from evolved stars.
  • 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 0915-3616 2009/04/30 [Not refereed][Not invited]
  • 46億年昔の宇宙空間での結晶化
    木村勇気, 三浦均, 塚本勝男
    日本マイクログラビティ応用学会誌 2009 [Not refereed][Not invited]
  • M. Saito, Y. Kimura
    The Astrophysical Journal Letters 703 L147-L151  2009 [Not refereed][Not invited]
  • KAITO CHIHIRO, KINUTA YASUHIKO, SUZUKI HITOSHI, ADACHI SYUNSUKE, KUMAMOTO AKIHITO, SAITO YOSHIO, KIMURA YUKI
    J Phys Soc Jpn 77 (9) 094708.1-094708.4  0031-9015 2008/09/15 [Not refereed][Not invited]
  • Y. Kimura, S. Sasaki, H. Suzuki, A. Kumamoto, M. Saito, C. Kaito
    ASTROPHYSICAL JOURNAL 684 (2) 1496 - 1501 0004-637X 2008/09 [Not refereed][Not invited]
     
    Mg-bearing silicate grains were produced directly from the vapor phase from magnesium and silicon oxide in a mixed atmosphere of Ar and O-2 in the laboratory. It was found that the crystallinity, which was deduced from the shape of the 10 mu m feature, of the grains depends on the ratio of magnesium to silicon oxide in the vapor phase. When the Mg/SiOx ratio was high, crystalline forsterite grains were produced owing to annealing of the silicate accompanied by large exothermic energy due to the oxidation of magnesium. The experimental result suggests that the crystallinity of circumstellar silicates could be determined by the balance between heat generation by magnesium oxidation and heat dissipation due to radiation. In this situation, later annealing of the silicate fraction or the use of a warm substrate for condensation of crystalline silicate is unnecessary. Crystalline silicates found in young stars are also able to be produced following our hypothesis after simultaneous evaporation of silicates and ices during energetic shocks in protostellar nebulae.
  • Chihiro Kaito, Yasuhiko Kinuta, Hitoshi Suzuki, Syunsuke Adachi, Akihito Kumamoto, Yoshio Saito, Yuki Kimura
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 (9) 094708-1-094708-4  0031-9015 2008/09 [Not refereed][Not invited]
     
    The apparent morphological difference between ZnO particles with and without an electric field applied during the growth process was elucidated by high-resolution transmission electron microscopy. The ZnO smoke produced immediately below the electric field by burning zinc in a gas mixture of O-2, and Ar, curved towards a negative plate. The typical tetrapod- or needle-shaped ZnO particles were seldom observed in the electric field; spherical particles were predominantly produced. Some of these spherical particles were composed of multiply twinned particles with an antiphase boundary. The growth of these multiply twinned particles was due to an increment in the ionicity in the crystallographic polar direction of ZnO bonding induced by the applied electric field.
  • Chihiro Kaito, Yasuhiko Kinuta, Hitoshi Suzuki, Syunsuke Adachi, Akihito Kumamoto, Yoshio Saito, Yuki Kimura
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 (9) 0031-9015 2008/09 [Refereed][Not invited]
     
    The apparent morphological difference between ZnO particles with and without an electric field applied during the growth process was elucidated by high-resolution transmission electron microscopy. The ZnO smoke produced immediately below the electric field by burning zinc in a gas mixture of O-2, and Ar, curved towards a negative plate. The typical tetrapod- or needle-shaped ZnO particles were seldom observed in the electric field; spherical particles were predominantly produced. Some of these spherical particles were composed of multiply twinned particles with an antiphase boundary. The growth of these multiply twinned particles was due to an increment in the ionicity in the crystallographic polar direction of ZnO bonding induced by the applied electric field.
  • Kenji Nina, Yuki Kimura, Kaorl Yokoyama, Osamu Kido, Gong Binyo, Chihiro Kaito
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 40 (9) 2995 - 2998 1386-9477 2008/08 [Not refereed][Not invited]
     
    The formation process of MoO(2) crystal from amorphous MoO(3) film has been imaged by in situ observation with a transmission electron microscope. Selective growth of flower-shaped MoO(2) crystals by heating above 673 K in vacuum was directly observed. Since the MoO(2) crystal has metallic conductivity of the order of indium oxide film containing tin (ITO film), the thin film growth of the MoO(2) phase has been discussed on the basis of a new substitute for ITO film. (C) 2008 Elsevier B.V. All rights reserved.
  • Chihiro Kaito, Masayuki Shintaku, Ryuta Sakao, Akihito Kumamoto, Midori Saito, Yuki Kimura, Shinsuke Ohyagi, Shigeru Morikawa, Hiroshi Suzuki
    JAPANESE JOURNAL OF APPLIED PHYSICS 47 (8) 6588 - 6591 0021-4922 2008/08 [Not refereed][Not invited]
     
    High-resolution transmission electron microscopy (HRTEM) of carbon particles has been carried out at 80 degrees C in saturated water vapor, to evaluate any structural alterations. Amorphous particles or microcrystallites of carbon based on the graphitic structure were altered to more stable graphitic structures such as ribbons or onion-like structures. The stable graphitic structure was altered again to the amorphous structure. Results are interpreted in terms of the oxidation of carbon particles in air. The differences in alterations among carbon particles, Pt clusters on carbon particles, and Pt clusters in carbon particles are presented on the basis of HRTEM images.
  • Chihiro Kaito, Masayuki Shintaku, Ryuta Sakao, Akihito Kumamoto, Midori Saito, Yuki Kimura, Shinsuke Ohyagi, Shigeru Morikawa, Hiroshi Suzuki
    JAPANESE JOURNAL OF APPLIED PHYSICS 47 (8) 6588 - 6591 0021-4922 2008/08 [Not refereed][Not invited]
     
    High-resolution transmission electron microscopy (HRTEM) of carbon particles has been carried out at 80 degrees C in saturated water vapor, to evaluate any structural alterations. Amorphous particles or microcrystallites of carbon based on the graphitic structure were altered to more stable graphitic structures such as ribbons or onion-like structures. The stable graphitic structure was altered again to the amorphous structure. Results are interpreted in terms of the oxidation of carbon particles in air. The differences in alterations among carbon particles, Pt clusters on carbon particles, and Pt clusters in carbon particles are presented on the basis of HRTEM images.
  • Yuki Kimura, Chihiro Kaito
    SURFACE & COATINGS TECHNOLOGY 202 (17) 4159 - 4162 0257-8972 2008/05 [Not refereed][Not invited]
     
    Generally, molybdenum, tungsten or tantalum is used as the evaporation source of many kinds of materials because of their high melting points and reasonably low vapor pressures. Therefore, the production of ultrafine particles of molybdenum, tungsten and tantalum has not been achieved by gas evaporation method. In this paper, it is shown that ultrafine particles of molybdenum, tungsten and tantalum were produced by a modified gas evaporation method. Transmission electron microscope observations show that the produced particles had a bcc structure with a size of less than 50 nm. Then, the thicknesses and the structures of the natural oxide layers were determined. Metallic particles develop an oxide layer on their surface and produce composite material automatically. Therefore, when metallic particles are used industrially or are treated in theoretical calculation studies, in view of realistic materials, the effect of the natural oxide layer must be considered. By the use of this modified gas evaporation method, ultrafine particles of many kinds of refractory materials will be produced. (C) 2008 Elsevier B.V. All rights reserved.
  • Frans J. M. Rietmeijer, Aurora Pun, Yuki Kimura, Joseph A. Nuth
    ICARUS 195 (1) 493 - 503 0019-1035 2008/05 [Not refereed][Not invited]
     
    Condensates produced in a laboratory condensation experiment of a refractory Ca-SiO-H(2)-O(2) vapor define four specific and predictable deep metastable eutectic calciosilica compositions. The condensed nanograins are amorphous solids, including those with the stoichiometric CaSiO(3) pyroxene composition. In evolving dust-condensing astronomical environments they will be highly suitable precursors for thermally supported, dust-aging reactions whereby the condensates form more complex refractory silicates, e.g., diopside and wollastonite, and calcite and dolomite carbonates. This kinetically controlled condensation experiment shows how the aging of amorphous refractory. condensates could produce the same minerals that are thought to require high-temperature equilibrium condensation. We submit that evidence for this thermal annealing of dust will be the astronomical detection of silica (amorphous or crystalline) that is the common, predicted, by-product of most of these reactions. (C) 2007 Elsevier Inc. All rights reserved.
  • Frans J. M. Rietmeijer, Aurora Pun, Yuki Kimura, Joseph A. Nuth
    ICARUS 195 (1) 493 - 503 0019-1035 2008/05 [Refereed][Not invited]
     
    Condensates produced in a laboratory condensation experiment of a refractory Ca-SiO-H(2)-O(2) vapor define four specific and predictable deep metastable eutectic calciosilica compositions. The condensed nanograins are amorphous solids, including those with the stoichiometric CaSiO(3) pyroxene composition. In evolving dust-condensing astronomical environments they will be highly suitable precursors for thermally supported, dust-aging reactions whereby the condensates form more complex refractory silicates, e.g., diopside and wollastonite, and calcite and dolomite carbonates. This kinetically controlled condensation experiment shows how the aging of amorphous refractory. condensates could produce the same minerals that are thought to require high-temperature equilibrium condensation. We submit that evidence for this thermal annealing of dust will be the astronomical detection of silica (amorphous or crystalline) that is the common, predicted, by-product of most of these reactions. (C) 2007 Elsevier Inc. All rights reserved.
  • 木村勇気
    日本惑星科学会誌 遊・星・人 17 (1) 62 - 68 0918-273X 2008/03/25 [Not refereed][Not invited]
  • Y. Kimura, Y. Miyazaki, A. Kumamoto, M. Saito, C. Kaito
    The Astrophysical Journal Letters 680 89 - 92 2008 [Not refereed][Not invited]
  • 原始太陽系星雲中での物質進化に関わるダストの振る舞い,
    木村勇気
    日本惑星科学会誌 17 62 - 68 2008 [Not refereed][Not invited]
  • Y. Kimura, C. Kaito
    The Astrophysical Journal Letters 685 83 - 86 2008 [Not refereed][Not invited]
  • Kimura Yuki, Kaito Chihiro
    Astrophysical Journal Letters 685 (1) L83 - L86 2008 [Refereed][Not invited]
  • Kimura Y, Kaito C, Nuth J. A. III
    Meteoritics & Planetary Science 43 (7) A76  2008 [Refereed][Not invited]
  • Chihiro Kaito, Ryoichi Ono, Ryuta Sakao, Akihito Kuniamoto, Midori Saito, Yuki Kimura, Shinsuke Ohyagi
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 46 (45-49) L1141 - L1142 0021-4922 2007/12 [Not refereed][Not invited]
     
    The effects of H-2 and O-2 gases on the typical fuel cell catalyst of Pt clusters on carbon particles (Pt on Q were examined using a special side-entry sample holder for high-resolution transmission electron microscopy, The holder can be used to transfer the specimen without exposure to air. The effects of H-2 and O-2 were detected after the specimen was exposed to the gases at 60 degrees C for 15 h. The predominant effect of H-2 was the coagulation of the Pt clusters. The effect of O-2 was to alter the structure of the carbon particles by oxidation.
  • Yuki Kimura, Joseph A. Nuth
    ASTROPHYSICAL JOURNAL 664 (2) 1253 - 1263 0004-637X 2007/08 [Not refereed][Not invited]
     
    We discuss room-temperature condensation experiments using either an electrical discharge or ultraviolet radiation to initiate gas-phase reactions resulting in silicate smokes. This formation process could represent processes occurring in low-density environments, because it is possible that the gases, which can condense at higher temperatures, remain after it cools, e. g., following a shock. In these environments, many condensates could be formed simultaneously. However, in the case of our iron silicate experiments, many of the smoke particles are iron silicate with a uniform composition that reflects the composition of the ambient gas atmosphere where they were produced. In these experiments, smoke particles of other materials such as iron oxide and silica were not formed. In the case of our Si-O experiments, hydro-silicate smoke particles are produced together with anhydrous silicate particles directly from the gas phase without later hydro alteration. The infrared spectra of these silicate particles show a very strong 11.36 mu m feature attributed to H2Si2O4 and possibly to Si2O3 compared with a simultaneously observed 9.2 mu m feature due to the Si-O vibration. We believe that finding the driving force for grain growth under a wide range of environmental conditions is important if we are to understand grain formation, because silicate grains, which formed in a plasma field or under UV irradiation, show different compositions, structures, shapes, and spectra from thermally condensed grains.
  • Non-mass-dependent oxygen isotopic fractionation in smokes produced in an electrical discharge
    Yuki Kimura, Joseph A. Nuth, Subrata Chakpaborty, Mark H. Thiemens
    METEORITICS & PLANETARY SCIENCE 42 (7-8) 1429 - 1439 1086-9379 2007/07 [Not refereed][Not invited]
     
    We report the first production of non-mass-dependently fractionated silicate smokes from the gas phase at room temperature from a stream of silane and/or pentacarbonyl iron in a molecular hydrogen (or helium) flow mixed with molecular oxygen (or nitrous oxide). The smokes were formed at the Goddard Space Flight Center (GSFC) at total pressures of just under 100 Torr in an electrical discharge powered by a Tesla coil, were collected from the surfaces of the copper electrodes after each experiment and sent to the University of California at San Diego (UCSD) for oxygen isotopic analysis. Transmission electron microscopy studies of the smokes show that they grew in the gas phase rather than on the surfaces of the electrodes. We hypothesize at least two types of fractionation processes occurred during formation of the solids: a mass-dependent process that made isotopically lighter oxides compared to our initial oxygen gas composition followed by a mass-independent process that produced oxides enriched in (17)O and (18)O. The nnaximum Delta(17)O observed is +4.7 parts per thousand for an iron oxide produced in flowing hydrogen, using O(2) as the oxidant. More typical displacements are 1-2 parts per thousand above the equilibrium fractionation line. The chemical reaction mechanisms that yield these smokes are still under investigation.
  • KIMURA YUKI, KAITO CHIHIRO
    日本結晶成長学会誌 34 (2) 89 - 93 0385-6275 2007/07 [Not refereed][Not invited]
  • Chihiro Kaito, Shinichi Sasaki, Yu Miyazaki, Akihito Kumamoto, Mami Kurumada, Kaori Yokoyama, Midori Saito, Yuki Kimura, Hitoshi Suzuki
    Advances in Geosciences: Volume 7: Planetary Science (PS) 7 125 - 131 2007/01/01 [Not refereed][Not invited]
     
    The crystallization of amorphous Mg-bearing silicate grains into Mg2SiO4 crystal covered with a thin carbon layer was directly observed by in-situ transmission electron microscopy. The temperature of crystallization of the sample was observed to be 200°C lower than that of the sample without the carbon layer. The graphitization energy of the surface amorphous carbon layer with the mean thickness of 10 nm accelerated the crystallization of the central amorphous Mg-bearing silicate grain of 100 nm order. Sample results for crystallization at room temperature are presented.
  • Akihito Kumamoto, Mami Kurumada, Yuki Kimura, Chihiro Kaito
    Advances in Geosciences: Volume 7: Planetary Science (PS) 7 93 - 99 2007/01/01 [Not refereed][Not invited]
     
    By making a carbon rod covered with Ti on the surface without exposure to air, TiC grains less than 10nm in diameter were predominantly produced. The introduction of a small amount of oxygen in Ar gas (partial pressure 1/1000), allowed the continuous formation of TiO2 and TiO-TiC. The infrared spectra of TiO2, TiO, and TiC were measured. An absorption feature attributed to TiO phase in oxidized TiC grains showed a characteristic peak at 14.7 µm.
  • 原始太陽系における物質進化に関わる結晶成長
    木村勇気, 墻内千尋
    2007 [Not refereed][Not invited]
  • C. Kaito, Y. Miyazaki, A. Kumamoto, Y. Kimura
    The Astrophysical Journal Letters, 666 L57-L60  2007 [Not refereed][Not invited]
  • T Sato, M Kurumada, K Kamitsuji, O Kido, H Suzuki, M Shintaku, Y Kimura, Y Saito, C Kaito
    PLANETARY AND SPACE SCIENCE 54 (6) 612 - 616 0032-0633 2006/05 [Not refereed][Not invited]
     
    The production of Fe2SiO4 (fayalite) crystalline grains was performed by two processes, namely, grain formation in a plasma field by evaporating a mixture powder of Fe and SiO and heat treatment of the product collected on the radio-frequency (RF) electrode side. Fe grains < 20 nm in size covered with an amorphous SiO layer selectively formed Fe2SiO4 grains by heating at 800 degrees C. By heating at 600 degrees C, in addition to the formation of Fe2SiO4 crystal grains, the FeO phase appeared. The doping effect of excited oxygen in a plasma field into the Fe small grains may be the trigger on the formation of fayalite through the FeO phase formation. The present experimental result suggests that the probability Of Fe2SiO4 grain formation in space is low. (c) 2006 Published by Elsevier Ltd.
  • T Sato, K Kamitsuji, M Shintaku, Y Kimura, M Kurumada, O Kido, H Suzuki, Y Saito, C Kaito
    PLANETARY AND SPACE SCIENCE 54 (6) 617 - 620 0032-0633 2006/05 [Not refereed][Not invited]
     
    Crystalline enstatite (MgSiO3) grains were produced by the simultaneous evaporation of SiO grains and Mg vapor in a plasma field. The MgSiO3 grains were spherical or needlelike. The necessity of a plasma field in astromineralogy is suggested in the present study. (c) 2006 Published by Elsevier Ltd.
  • Formation of TiC core-graphitic mantle grains from CO gas
    Yuki Kimura, Joseph A. Nuth, Frank T. Ferguson
    METEORITICS & PLANETARY SCIENCE 41 (5) 673 - 680 1086-9379 2006/05 [Not refereed][Not invited]
     
    We demonstrate a new formation route for TiC core-graphitic mantle spherules that does not require carbon-atom addition and the very long time scales associated with such growth (Bernatowicz et al. 1996). Carbonaceous materials can be formed from C2H2 and its derivatives, as well as from CO gas. In this paper, we will demonstrate that large-cage-structure carbon particles can be produced from CO gas by the Boudouard reaction. Since the sublimation temperature for such fullerenes is low, the large cages can be deposited onto previously nucleated TiC and produce TiC core-graphitic mantle spherules. New constraints for the formation conditions and the time scale for the formation of TiC core-graphitic mantle spherules are suggested by the results of this study. In particular, TiC core-graphitic mantle grains that are found in primitive meteorites that have never experienced hydration Could be mantled by fullerenes or carbon nanotubes rather than by graphite. In situ observations of these grains in primitive anhydrous meteoritic matrix could confirm or refute this prediction and would demonstrate that the graphitic mantle on such grains is a metamorphic feature due to interaction of the presolar fullerenes with water within the meteorite matrix.
  • O Kido, M Kurumada, K Kamltsuji, T Tanigaki, T Sato, Y Kimura, H Suzuki, Y Saito, C Kaito
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 31 (2) 169 - 173 1386-9477 2006/03 [Not refereed][Not invited]
     
    The synthesis of Al-Cr single quasicrystal (QC) nanoparticles of the decagonal phase was achieved by introducing an advanced gas flow evaporation method. By obtaining Successive electron diffraction patterns for single-QC nanoparticles, the phase transformation temperature of a single-QC nanoparticle was determined to be 700 degrees C. It was also determined that part of the QC nanoparticle decomposed into hex-AI(8)Cr(5) and Al during the phase transformation. Since the grain growth did not occur during the phase transformation in the present experiment, the inherent phase transformation temperature could be measured. (c) 2006 Elsevier B.V. All rights reserved.
  • K. Yokoyama, Y. Kimura, O. Kido, M. Kurumada, A. Kumamoto, C. Kaito
    Advances in Geosciences 7 115 - 123 2006 [Not refereed][Not invited]
  • Kimura Y, Nuth J. A. III
    Meteoritics & Planetary Science 41 (8) A95  2006 [Refereed][Not invited]
  • Kaito C, Sasaki S, Miyazaki Y, Kurumada M, Kumamoto A, Suzuki H, Kimura Y, Koike C
    Meteoritics & Planetary Science 41 (8) A91  2006 [Refereed][Not invited]
  • Y Kimura, M Kurumada, K Tamura, C Koike, H Chihara, C Kaito
    ASTRONOMY & ASTROPHYSICS 442 (2) 507 - 512 0004-6361 2005/11 [Not refereed][Not invited]
     
    Nanosized MgS grains, which have been considered the origin of the 30 mu m emission feature of carbon-rich evolved objects, were produced from the gas phase using an advanced gas evaporation method. The far-infrared spectrum of cubic MgS grains showed a characteristic absorption peak at 311 cm(-1) (32.1 mu m) with three shoulders at 460, 400 and 262 cm(-1) (21.7, 25.0 and 38.2 mu m). On the other hand, when the grains were roundish or network-like, the absorption peak at 250 cm(-1) became predominant. The cubic MgS grains were produced by direct nucleation from the gas phase. In the case of production via a gas-solid reaction, the MgS grains were network-like. Therefore, the formation environments of MgS grains around carbon-rich evolved objects may be predicted from the intensity of 310 and 250 cm(-1) bands. We suggest that the origins of the absorption band at 310 and 250 cm(-1) are (100), (110) and/or (111) surfaces of MgS grains, respectively.
  • Y Kimura, K Tamura, C Koike, H Chihara, C Kaito
    ICARUS 177 (1) 280 - 285 0019-1035 2005/09 [Not refereed][Not invited]
     
    A new method of producing pyrrhotite grains, which are most commonly found in cometary material and interplanetary dust particles, was developed. Pyrrhotite grains in the monophase having a 7C structure were predominately produced using a solid-solid reaction between iron and sulfur grains at room temperature. The characteristic infrared peaks were observed at 602, 563, and 397 cm(-1) (16.6, 17.8, and 25.2 mu m). (c) 2005 Elsevier Inc. All rights reserved.
  • Y Kimura, JA Nuth
    ASTROPHYSICAL JOURNAL 630 (1) 637 - 641 0004-637X 2005/09 [Refereed][Not invited]
     
    We demonstrate that CaO and Ca(OH)(2) are excellent candidates to explain the 6.8 mu m feature, which is one of the most obscure features in young stellar objects. We discuss the condensation of CaO grains and the potential formation of a Ca(OH)(2) surface layer. The infrared spectra of these grains are compared with the spectra of 15 young stellar objects. We note that CaO-rich grains are seen in all meteoritic CAIs (calcium-aluminum-rich inclusions) and that the 6.8 mu m feature has only been observed in young stellar objects. Therefore, we consider CaO grains to be a plausible candidate to explain the 6.8 mu m feature and hypothesize that they are produced in the hot interiors of young stellar environments.
  • Y Kimura, C Kaito
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 28 (3) 281 - 285 1386-9477 2005/08 [Not refereed][Not invited]
     
    It was shown that a carbon nanotube was selectively formed from carbon film containing Ti, supported by a standard Mo transmission electron microscopic grid, by heating at 800 degrees C in vacuum. With heating above 950 degrees C, graphite and rutile crystals of TiO2 predominately appeared. The formation of oxide is due to the supply of oxygen from the Mo grid. The formation mechanism of the carbon nanotubes was discussed on the basis of the heat of combustion due to the oxidation of titanium. The present result will lead to the development of an efficient method of production of carbon nanotubes. (c) 2005 Elsevier B.V. All rights reserved.
  • C Kaito, K Kamitsuji, S Tanaka, O Kido, M Kurumada, T Sato, Y Kimura, H Suzuki, Y Saito
    THIN SOLID FILMS 483 (1-2) 396 - 399 0040-6090 2005/07 [Not refereed][Not invited]
     
    The dynamic behavior of a film produced by coevaporation of Ge-SiO was observed in situ using a transmission electron microscope. The film produced had an amorphous structure containing Si, Ge and SiO2. A characteristic change of the film was observed above 500 degrees C. Upon heating at 750 degrees C, in addition to the growth of the SiGe mixed crystal with the diamond structure, the liquidlike mixed phase of SiGe-SiO2 was also produced. The growth process of the liquidlike phase was directly observed in situ. The growth process of Ge and GeSi nanocrystallites has been elucidated by cooling the mixed film to room temperature. (c) 2004 Elsevier B.V All rights reserved.
  • A. Kouchi, H. Nakano, Y. Kimura, C. Kaito
    Astrophysical Journal 626 (2) L129 - L132 1538-4357 2005/06/20 [Not refereed][Not invited]
     
    We have identified new formation routes of diamond in interstellar clouds and parent bodies of carbonaceous chondrites in laboratory experiments. The diamond precursor nucleated under UV photolysis of interstellar ice mixtures in molecular clouds and grew with further UV irradiation in diffuse clouds. The present study supports the occurrence of diamonds in interstellar clouds and suggests that diamond is ubiquitous in space. We also performed experiments on the processes of aqueous alteration and subsequent thermal metamorphism of organic materials formed in molecular clouds, and the results were consistent with the formation of diamonds by this process in the parent bodies of carbonaceous chondrites. The various characteristics of nanodiamonds in chondrites and interplanetary dust are well explained by these new formation routes. © 2005. The American Astronomical Society. All rights reserved.
  • Y Kimura, T Sato, C Kaito
    CARBON 43 (7) 1570 - 1574 0008-6223 2005/06 [Not refereed][Not invited]
  • Y Kimura, C Kaito
    THIN SOLID FILMS 476 (1) 65 - 67 0040-6090 2005/04 [Not refereed][Not invited]
     
    New carbide crystallites, which have a solid-solution phase with diamond structure, were formed from amorphous carbon film containing a transition metal such as Fe, Co, Mo or Ti by vacuum heating at 500-800 degrees C. The lattice constants for each solid-solution phase have been determined from electron diffraction patterns and high-resolution transmission electron microscope images. The formation of carbon polymorphs has been summarized as being dependent on the heat treatment temperature. (c) 2004 Elsevier B.V. All rights reserved.
  • Y. Kimura, M. Ishikawa, M. Kurumada, T. Tanigaki, H. Suzuki, C. Kaito
    JOURNAL OF CRYSTAL GROWTH 275 (1-2) E977 - E981 0022-0248 2005/02 [Not refereed][Not invited]
     
    Si (10-50%)-containing carbon (C-Si) films were prepared by ion sputtering of carbon and silicon carbide mixture pellets. The C-Si film was composed of a solid-solution phase of carbon and silicon with a diamond structure. The film showed a higher transparency than a simultaneously evaporated C-Si mixture film. Diamond crystals 100 nm in diameter were also produced by vacuum heating of C-Si film at 800 degrees C: The infrared spectrum showed significant absorption features at 9.5 and 21 mu m; in contrast to the 11 and 12 mm of SiC. The 21 mu m feature is one of the candidate unidentified infrared bands on the spectra of carbon-rich post-asymptotic giant branch stars. (C) 2004 Elsevier B.V. All rights reserved.
  • Mami Kurumada, Osamu Kido, Takeshi Sato, Hitoshi Suzuki, Yuki Kimura, Katsuya Kamitsuji, Yoshio Saito, Chihiro Kaito
    JOURNAL OF CRYSTAL GROWTH 275 (1-2) E1673 - E1678 0022-0248 2005/02 [Not refereed][Not invited]
     
    WO3 nanoparticles from 10 to 250nm in diameter were formed by burning tungsten wire in low-oxygen-partial-pressure atmosphere in Ar gas. The structure of the 10-nm-order particle was cubic WO3, and for the particle larger than 50 nm, the structure was triclinic WO3. The color of the produced samples changed from blue to yellowish green and yellow depending on the particle size. It was also shown that the present particle is a good transmittance material for mid-IR light with wavelength between 5 and 20 mu m. The growth of huge particles by coalescence growth in smoke has been discussed. (C) 2004 Elsevier B.V. All rights reserved.
  • Takeshi Sato, Hitoshi Suzuki, Osamu Kido, Mami Kurumada, Katsuya Kamitsuji, Yuki Kimura, Hiromichi Kawasaki, Satoo Kaneko, Yoshio Saito, Chihiro Kaito
    JOURNAL OF CRYSTAL GROWTH 275 (1-2) E983 - E987 0022-0248 2005/02 [Not refereed][Not invited]
     
    Transition metals, such as tungsten (W), molybdenum (Mo) and chromium (Cr), were doped into ZnO nanoparticles using an RF plasma system. The resulting ZnO nanoparticles with the size of 30-50 nm changed from white to yellowish or to orange depending on the doped transition metals. The doping position of these transition metals in the ZnO crystal was the same as that determined in a previous paper (J. Crystal Growth 265 (2004) 149). It was found that light with wavelength shorter than 385 nm can be removed by doping. The morphological change due to doping of elements was discussed in terms of the difference of ionicity. (C) 2004 Elsevier B. V. All rights reserved.
  • Osamu Kido, Katsuya Kamitsuji, Mami Kurumada, Takeshi Sato, Yuki Kimura, Hitoshi Suzuki, Yoshio Saito, Chihiro Kaito
    JOURNAL OF CRYSTAL GROWTH 275 (1-2) E1745 - E1750 0022-0248 2005/02 [Not refereed][Not invited]
     
    The morphological alteration from delta- to alpha-Cr nanoparticles and the phase transition temperature were directly observed by in situ experiment using a transmission electron microscope. The icositetrahedral nanoparticle of delta-Cr transformed into a rhombic dodecahedral nanoparticle of alpha-Cr upon heating at 550 degrees C: It was demonstrated that the most stable shape of the alpha-Cr nanoparticle is the rhombic dodecahedron. Upon heating the alpha-Cr nanoparticle at 650 degrees C; the (1 1 3) layer of Cr2O3 grew topotactically in the direction of [100] of alpha-Cr nanoparticle. We concluded that the alpha-Cr nanoparticle includes about 20-30 at% oxygen, as estimated from the volume of the Cr2O3 surface layer. (C) 2004 Elsevier B.V. All rights reserved.
  • Y. Kimura, J. A. Nuth III
    The Astrophysical Journal 630 637 - 641 2005 [Not refereed][Not invited]
  • K Kamitsuji, H Suzuki, Y Kimura, T Sato, Y Saito, C Kaito
    ASTRONOMY & ASTROPHYSICS 429 (1) 205 - 208 0004-6361 2005/01 [Not refereed][Not invited]
     
    A novel method for producing MgO and SiO2 smokes was developed. Mg-bearing silicate grain formation using the coalescence and growth of MgO and SiO2 grains was carried out in our laboratory. It becomes evident that single and poly crystalline Mg2SiO4 (forsterite) and amorphous Mg-bearing silicate grains can be produced by the coalescence and growth of MgO and SiO2 grains. This result suggests that the observed crystalline Mg2SiO4 grains and amorphous Mg-bearing silicate particles in Red Super Giant (RSG), Asymptotic Giant Branch (AGB), post-AGB and planetary nebula (PNe) could be produced by the coalescence and growth of MgO and SiO2 grains.
  • O Kido, H Suzuki, Y Kimura, T Sato, Y Saito, C Kaito
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 25 (4) 619 - 624 1386-9477 2005/01 [Not refereed][Not invited]
     
    Al-Mn quasicrystal ultrafine particles can be produced by the advanced gas evaporation method (AGEM), which is a method of preparing ultrafine alloy particles by coalescence growth among the particles near the evaporation sources. We investigated the phase transition temperature from a quasicrystal to a stable crystal, by examining successive electron diffraction patterns of an ultrafine particle in an in situ experiment using a transmission electron microscope. In spite of the report that the Al86Mn14 quasicrystal transforms into the crystal phase at around 400-670 degreesC on thin film specimens, the quasicrystal ultrafine particle transformed at 800 degreesC, i.e., the quasicrystal ultrafine particle is more stable. Since the cross-sectional view of the surface oxide layer of the quasicrystal ultrafine particles can be easily observed, the surface oxides of eta-Al2O3 and MnO were characterized as a result of the oxidation of residual atoms on the surface of the produced alloy particles including the quasicrystals. The conditions required for Al-Mn quasicrystal ultrafine particle formation by the AGEM can be estimated under the cooling rate of 105 K/s. (C) 2004 Elsevier B.V. All rights reserved.
  • S Sasaki, H Suzuki, Y Kimura, T Sato, T Tanigaki, O Kido, K Kamitsuji, M Kurumada, C Kaito
    EARTH PLANETS AND SPACE 57 (5) 399 - 401 1343-8832 2005 [Not refereed][Not invited]
     
    The formation of Al(2)O(3) phases by the solid-solid reaction of a metallic Al layer evaporated on a SiO(2) amorphous grain has been induced by heating above 600 degrees C in vacuum (1 x 10(-6) Pa). The distortion process of the amorphous SiO(2) grains by the formation of Al(2)O(3) have been directly imaged by in-situ TEM observation. A partly deposited Al layer covered the SiO(2) grains after heating at 750 degrees C, and gamma-Al(2)O(3) grains of about 25 nm diameters were formed on the SiO(2) surface. Upon the growth of Al(2)O(3), the SiO(2) grain decomposed into a mixture of metallic Si and SiO(2) and disappeared as a result of sublimation due to the formation of SiO(x) at high temperatures. The present result on dust surface dynamics will become an important field with respect to the metamorphism of grains from the astromineralogical viewpoint.
  • Y. Kimura, Joseph A. Nuth III, Frank T. Ferguson
    The Astrophysical Journal Letters 632 L159-L162  2005 [Not refereed][Not invited]
  • Kimura Y, Nuth JA, Ferguson FT
    Astrophysical Journal 632 (2) L159 - L162 2005 [Refereed][Not invited]
  • K Kamitsuji, S Ueno, H Suzuki, Y Kimura, T Sato, T Tanigaki, O Kido, M Kurumada, C Kaito
    ASTRONOMY & ASTROPHYSICS 422 (3) 975 - 979 0004-6361 2004/08 [Not refereed][Not invited]
     
    Experimental studies on the metamorphism of SiO(x) grains under heating at 10(-6) Pa have been conducted using a high-resolution transmission electron microscope. Si crystallites were predominantly grown at 500 to 700 degreesC in SiO(x) grains. The Si crystallites disappeared at 800 degreesC and evaporated as the SiO phase.
  • O Kido, Y Higashino, K Kamitsuji, M Kurumada, T Sato, Y Kimura, H Suzuki, Y Saito, C Kaito
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 (7) 2014 - 2016 0031-9015 2004/07 [Not refereed][Not invited]
     
    The iron oxide ultrafine particles prepared by the gas evaporation method, in which commercial alpha-Fe2O3 powder is evaporated, are composed of alpha-Fe2O3 particles covered with a gamma-Fe2O3 mantle layer. To study the phase transition temperature of the gamma-Fe2O3 mantle layer, the particles were heated and observed in a transmission electron microscope. The present specimen of gamma-Fe2O3 transformed completely to alpha-Fe2O3 at above 700degreesC, and this phase transition was irreversible. The phase transition temperature was 1.4 times higher than the bulk value. The growth mechanism of the present specimen of alpha-Fe2O3 particles covered with the gamma-Fe2O3 mantle layer has been discussed in terms of the difference in the cooling rates between the inside and the surface of the particle at around the evaporation source.
  • O Kido, Y Higashino, K Kamitsuji, M Kurumada, T Sato, Y Kimura, H Suzuki, Y Saito, C Kaito
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 (7) 2014 - 2016 0031-9015 2004/07 [Refereed][Not invited]
     
    The iron oxide ultrafine particles prepared by the gas evaporation method, in which commercial alpha-Fe2O3 powder is evaporated, are composed of alpha-Fe2O3 particles covered with a gamma-Fe2O3 mantle layer. To study the phase transition temperature of the gamma-Fe2O3 mantle layer, the particles were heated and observed in a transmission electron microscope. The present specimen of gamma-Fe2O3 transformed completely to alpha-Fe2O3 at above 700degreesC, and this phase transition was irreversible. The phase transition temperature was 1.4 times higher than the bulk value. The growth mechanism of the present specimen of alpha-Fe2O3 particles covered with the gamma-Fe2O3 mantle layer has been discussed in terms of the difference in the cooling rates between the inside and the surface of the particle at around the evaporation source.
  • Y Kimura, O Kido, M Oomoto, K Ogawa, H Namba, C Kaito
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 43 (7A) L888 - L890 0021-4922 2004/07 [Refereed][Not invited]
     
    Si-doped amorphous carbon film prepared by the simultaneous vacuum evaporation of carbon and silicon has been irradiated by a synchrotron radiation (SR) beam. The preferential growth of diamond crystals was found by transmission electron microscope observation conducted after SR irradiation. It was also found that the solid-solution phase of carbon and silicon with the diamond structure was produced in the as-deposited film and at the initial stage of the crystallization. The solid-solution crystal remained in the stable phase up to 6 nm in size. The catalytic effect of Si was prominent in the growth of diamond.
  • Y Kimura, A Ikegami, M Kurumada, K Kamitsuji, C Kaito
    ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 152 (2) 297 - 301 0067-0049 2004/06 [Not refereed][Not invited]
     
    crystallites less than 10 nm in size showed an absorption feature at 14.3 mum. This 14.3 mum absorption was rarely seen in specimens ranging from bulk material to grains of 50 nm in size. The 14.3 mum feature was weakened as a result of the growth of TiC crystallites by heat treatment. When the carbide grains were covered with a carbon layer, the absorption peaks were considerably weakened, i.e., the absorption intensity depended on the grain surface state. A possible explanation is that the effects of size and shape on the spectra depend on the surface anisotropy.
  • M Kurumada, Y Kimura, H Suzuki, O Kido, Y Saito, C Kaito
    SCRIPTA MATERIALIA 50 (11) 1413 - 1416 1359-6462 2004/06 [Not refereed][Not invited]
     
    The structure of NiTi shape memory alloy nanoparticles was determined by high-resolution electron microscopy. The mixture of Ni4Ti3 and R-phases was observed, which clearly showed lattice relationships of (2 (1) over bar 1)(B2)//(1 0 1)Ni4Ti3 and (2 (2) over bar 0)(B2)//(1 3 1)Ni4Ni3. Lattice images of an R-phase particle suggested the existence of a Ni-rich Guinier-Preston zone (G.P. zone). (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
  • S Tanaka, O Kida, M Kurumada, K Kamitsuji, Y Kimura, H Suzuki, Y Saito, C Kaito
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 23 (1-2) 108 - 113 1386-9477 2004/06 [Not refereed][Not invited]
     
    Complete mixture films of carbon and germanium produced by the co-evaporation in vacuum were directly heated in a transmission electron microscope. It was noticed that the diffusion and growth of Ge dots in the mixture film take place at approximately 500degreesC. On the other hand, Ge dots coated with amorphous carbon were produced by simultaneous evaporation of carbon and Ge in Ar gas at 10 kPa. In addition to Ge clusters of 3-10 nm in size, multiple-twin Ge clusters with the size of 10 nm have been produced in carbon soot. These Ge clusters showed a diamond structure. The growth process of Ge clusters in amorphous carbon soot has been discussed using the result in the mixture film experiment and temperature distribution in the particle formation process. (C) 2004 Elsevier B.V. All rights reserved.
  • Y Kimura, A Ikegami, M Kurumada, K Kamitsuji, C Kaito
    ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 152 (2) 297 - 301 0067-0049 2004/06 [Refereed][Not invited]
     
    crystallites less than 10 nm in size showed an absorption feature at 14.3 mum. This 14.3 mum absorption was rarely seen in specimens ranging from bulk material to grains of 50 nm in size. The 14.3 mum feature was weakened as a result of the growth of TiC crystallites by heat treatment. When the carbide grains were covered with a carbon layer, the absorption peaks were considerably weakened, i.e., the absorption intensity depended on the grain surface state. A possible explanation is that the effects of size and shape on the spectra depend on the surface anisotropy.
  • T Tanigaki, Y Kimura, H Suzuki, M Kurumada, C Kaito
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 (5) 1375 - 1376 0031-9015 2004/05 [Not refereed][Not invited]
  • T Sato, H Suzuki, O Kido, M Kurumada, K Kamitsuji, Y Kimura, A Takeda, S Kaneko, Y Saito, C Kaito
    JOURNAL OF CRYSTAL GROWTH 265 (1-2) 149 - 153 0022-0248 2004/04 [Not refereed][Not invited]
     
    A tungsten plate was set on a one-plate electrode in RF plasma using parallel plates in a mixed gas of argon (9.75 Torr) and oxygen (0.25 Torr). Zn smoke was introduced into the plasma field. W atoms were doped in the ZnO smoke formation field in the RF plasma system. The resulting particles with a size of 30 run were identified to be hexagonal ZnO particles. The collected particles changed from white to yellow, i.e., W atoms were doped into ZnO particles. The image of the (0 0 0 1) lattice, which is the forbidden reflection, appeared predominantly in the W-doped ZnO particle. Furthermore, by optical measurement. it Was found that the existence of W atoms can control the recombination radiation due to the exciton. On the basis of high-resolution transmission electron microscopic images, the doped W positions are discussed as being in the commensurate Configuration of W items in the ZnO crystal at positions equivalent to those in the cubic anti-fluoride structure. (C) 2004 Elsevier B.V. All rights reserved.
  • T Sato, H Suzuki, O Kido, M Kurumada, K Kamitsuji, Y Kimura, A Takeda, S Kaneko, Y Saito, C Kaito
    JOURNAL OF CRYSTAL GROWTH 265 (1-2) 149 - 153 0022-0248 2004/04 [Refereed][Not invited]
     
    A tungsten plate was set on a one-plate electrode in RF plasma using parallel plates in a mixed gas of argon (9.75 Torr) and oxygen (0.25 Torr). Zn smoke was introduced into the plasma field. W atoms were doped in the ZnO smoke formation field in the RF plasma system. The resulting particles with a size of 30 run were identified to be hexagonal ZnO particles. The collected particles changed from white to yellow, i.e., W atoms were doped into ZnO particles. The image of the (0 0 0 1) lattice, which is the forbidden reflection, appeared predominantly in the W-doped ZnO particle. Furthermore, by optical measurement. it Was found that the existence of W atoms can control the recombination radiation due to the exciton. On the basis of high-resolution transmission electron microscopic images, the doped W positions are discussed as being in the commensurate Configuration of W items in the ZnO crystal at positions equivalent to those in the cubic anti-fluoride structure. (C) 2004 Elsevier B.V. All rights reserved.
  • Y Kimura, T Sato, C Kaito
    CARBON 42 (1) 33 - 38 0008-6223 2004 [Not refereed][Not invited]
     
    In the present study, by a simple method, carbon soot with a narrow absorption features at around 220 nm was produced by pyrolysis of methane gas at a hot (1400-2800degreesC) filament. A detailed correlation between the structure and the optical spectra of carbon soot was carried out using a high-resolution transmission electron microscope. It appears that the origin of the narrow absorption peak is an onion-like graphitic structure. Interestingly, we found that the absorption peak position and the size of the soot can be controlled by the production temperature. The absorption peak is located at 217.5 nm, i.e., at the position of an intense interstellar absorption, when the onion structure has about 5 nm diameter. Infrared spectroscopy was applied to further elucidate the chemical composition of the obtained soot. (C) 2003 Elsevier Ltd. All rights reserved.
  • Y. Kimura, O. Kido, M. Oomoto, K. Ogawa, H. Namba, C. Kaito
    Japanese Journal of Applied Physics 43 (7) L888-L890  2004 [Not refereed][Not invited]
  • T Tanigaki, Y Kimura, H Suzuki, C Kaito
    JOURNAL OF CRYSTAL GROWTH 260 (3-4) 298 - 303 0022-0248 2004/01 [Not refereed][Not invited]
     
    A particle with a CdTe core and carbon mantle was produced by the advanced carbon-coating method which enables direct coverage with a carbon layer using an electron microscope. The coagulated particles containing approximately 30-200 CdTe particles produced by the gas evaporation method were covered with a carbon layer of about 7 nm thickness at 300 degreesC. By heating these particles above 500 degreesC, the sublimation process of a part of the CdTe particle can be directly captured by high-resolution transmission electron microscopy and recorded in real time on videotape. Sublimation on the CdTe(111) surfaces occurred in the step flow mode of two (111) layers. It was observed that two (111) zinc-blende layers changed to the (0002) wurtzite configuration unit just before sublimation. The condensation of CdTe on the sublimated particle surface and growth of CdTe in the carbon layers were also captured in the video image. These sublimation processes were discussed in terms of the existence of the polarity of II-VI compounds. (C) 2003 Elsevier B.V. All rights reserved.
  • Y Ishikawa, O Kido, Y Kimura, M Kurumada, H Suzuki, Y Saito, C Kaito
    SURFACE SCIENCE 548 (1-3) 276 - 280 0039-6028 2004/01 [Not refereed][Not invited]
     
    Transmission electron microscopy was used to study spontaneous copper selenide formation on Cu particles covered with an oxide layer. Even if the copper particle surface was covered with a Cu2O layer, selenides were formed by diffusion through the metal oxide layer. For a particle size less than 50 nm, selenide was formed in Cu particles by the diffusion of Se atoms passing through the Cu2O layer. For particles larger than 100 nm in size, selenide was formed in Se film. It was also found that the thickness of the Cu2O layer on the surface of Cu particle accelerated diffusion of Se atoms to the copper particle. (C) 2003 Elsevier B.V. All rights reserved.
  • T Sato, O Kido, M Kurumada, Y Kimura, H Suzuki, Y Saito, C Kaito
    CARBON 42 (8-9) 1875 - 1877 0008-6223 2004 [Not refereed][Not invited]
  • K Tamura, Y Kimura, H Suzuki, O Kido, T Sato, T Tanigaki, M Kurumada, Y Saito, C Kaito
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 42 (12) 7489 - 7492 0021-4922 2003/12 [Not refereed][Not invited]
     
    Ultrafine particles of various metals [Cr, Mn, Fe, Al, Ni, Cu, In, Si, Ge, Zn, Mg and Sn], produced by the gas evaporation method were covered with the oxide layer of thickness less than 10 nm by exposure to air. In order to clarify the structure and thickness of the surface oxide layer, on various metal ultrafine particles, high-resolution electron microscopy and infrared spectroscopy have been extensively used.
  • Y Kimura, C Kaito
    ASTRONOMY & ASTROPHYSICS 409 (1) 159 - 161 0004-6361 2003/10 [Not refereed][Not invited]
     
    The origins of spectral feature of stellar source are identified on the basis of laboratory studies. Although ZrC grains were identified as the crystalline presolar grains in meteorites, the spectral data of ZrC grains have not been measured in the laboratory. Therefore, ZrC grains with the same size as the presolar grains were produced in the laboratory. It has been found that the infrared spectrum of ZrC grains shows broad absorption features at 9.4 and 12.4 mum.
  • T Tanigaki, H Suzuki, Y Kimura, O Kido, Y Saito, C Kaito
    JOURNAL OF CRYSTAL GROWTH 256 (3-4) 317 - 323 0022-0248 2003/09 [Not refereed][Not invited]
     
    In order to elucidate the stability of a silicon oxide layer on zoo, the dynamic behavior of SiO- and SiO2-layer-coated ZnO ultrafine particle surfaces were directly observed by heating in a transmission electron microscope up to 700degreesC. In the case of SiO-coated ZnO ultrafine particles, ZnO nanocrystallites with the size of 2 nm grew in the SiO layer at 500degreesC. In the case of SiO-coated ZnO ultrafine particles, beta-cristobalite with the size of 10nm order was grown at 600degreesC. Zn2SiO4 particles were grown by coalescence between beta-cristobalite and ZnO at 700degreesC. By comparing the SiO and SiO, layers on ZnO ultrafine particles, it was found that the behaviors of the two silicon oxide layers are clearly different. (C) 2003 Elsevier B.V. All rights reserved.
  • T Sato, A Takeda, Y Kimura, H Suzuki, Y Saito, C Kaito
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 42 (9A) 5896 - 5897 0021-4922 2003/09 [Not refereed][Not invited]
     
    Amorphous silicon oxide particles with the size of 30-100 nm were produced by spraying Si(C2H5O)(4) liquid into a plasma region. Plasma was generated at a high pressure of 10 Torr in a mixture gas of argon and oxygen. The production of two silicon oxide particles with the structure of SiO and SiO2 could be controlled by the oxygen partial pressure in plasma.
  • Y. Kimura, C. Kaito
    Monthly Notices of the Royal Astronomical Society 343 (2) 385 - 389 0035-8711 2003/08/01 [Not refereed][Not invited]
     
    Focusing on the growth of metal carbide particles and the formation of pre-solar grains, a new attempt has been made for titanium carbide (TiC) systems. Using the noble gas evaporation method, we succeeded in producing TiC core (50-nm) carbon mantle (2-nm) grains of the same core size as pre-solar grains. The infrared spectrum has broad absorption features at 9.5 and 12.5 μm. It was also found that these absorption peaks became weaker by an increase to 15 nm of carbon mantle layer. The determination method of the contact angle of carbon on the TiC grain has been developed using a high-resolution electron microscopic technique. The contact angles between TiC and carbon were 22°8 ± 0°7 and 24°0 ± 0°4 on the (111) and (100) TiC grain surfaces, respectively.
  • Y Kimura, C Kaito
    JOURNAL OF CRYSTAL GROWTH 255 (3-4) 282 - 285 0022-0248 2003/08 [Not refereed][Not invited]
     
    It was shown that nanodiamonds were easily formed from carbon film containing Si. The growth of diamond and beta-Sic. is controllable by adjusting the heating temperature and the proportion of Si. Present result will develop a wide range of new opportunities for research and applications in the field of nanotechnology. (C) 2003 Elsevier Science B.V. All rights reserved.
  • Y Kimura, H Ueno, H Suzuki, T Tanigaki, T Sato, Y Saito, C Kaito
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 19 (3) 298 - 302 1386-9477 2003/08 [Not refereed][Not invited]
     
    The high-temperature behavior of Au clusters on a Si nanoparticle surface has been studied using the atomic-resolution high-temperature stage of a transmission electron microscope. Au atoms diffuse into the Si nanoparticle at 680degreesC and return to the surface at room temperature. The movement of diffused Au atoms on the Si surface steps and the movement of Guinier-Presion-zone-like contrast observed for the segregation of An atoms on the (lll) Si plane, have been directly observed. These phenomena, which can be detected only at high temperatures, are presented in this paper. (C) 2003 Elsevier B.V. All rights reserved.
  • A Ikegami, Y Kimura, H Suzuki, T Sato, T Tanigaki, O Kido, M Kurumada, Y Saito, C Kaito
    SURFACE SCIENCE 540 (2-3) 395 - 400 0039-6028 2003/08 [Not refereed][Not invited]
     
    Titanium carbide formation by the solid-solid reaction on the surface of Ti nanoparticles was studied in situ using a high-resolution transmission electron microscope with a heating stage. The cross-sectional image of the Ti surface was clearly observed. Vacuum-deposited carbon covered the whole the surface of Ti nanoparticles in spite of the partly evaporation on the nanoparticle surface. The diffusion of the carbon atoms inside the Ti nanoparticles depended on the size of the nanoparticles. When the Ti nanoparticle diameter was less than 30 nm, carbon atoms diffused into the Ti nanoparticle and formed TiC. The superstructure of the Ti nanoparticles was observed, which revealed the growth process of TiC to be the diffusion of carbon atoms. For Ti nanoparticles with diameter larger than 30 run it was observed that diffusion of Ti atoms into the carbon layer was dominant, which resulted in formation of TiC in the carbon layer at the surface of Ti nanoparticles. (C) 2003 Elsevier B.V. All rights reserved.
  • T Sato, T Tanigaki, H Suzuki, Y Saito, O Kido, Y Kimura, C Kaito, A Takeda, S Kaneko
    JOURNAL OF CRYSTAL GROWTH 255 (3-4) 313 - 316 0022-0248 2003/08 [Not refereed][Not invited]
     
    ZnO particles were produced by dropping Zn powder into a heated boat just below the plasma electrodes in a mixture gas of argon and oxygen. The resulting particles look spherical with the size of 30 nm and were of tetrapod configuration having four [0 0 0 1] axes of ZnO. The dispersion became better than that in the case of another method without plasma. The ultraviolet-visible light transmittance of the specimen showed sharp absorption. The electric charge in the plasma field controlled the coalescence growth of each particle and improved the dispersion of the particles due to the plasma effect. (C) 2003 Elsevier Science B.V. All rights reserved.
  • Y Kimura, H Ueno, H Suzuki, T Tanigaki, T Sato, Y Saito, C Kaito
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 19 (3) 298 - 302 1386-9477 2003/08 [Refereed][Not invited]
     
    The high-temperature behavior of Au clusters on a Si nanoparticle surface has been studied using the atomic-resolution high-temperature stage of a transmission electron microscope. Au atoms diffuse into the Si nanoparticle at 680degreesC and return to the surface at room temperature. The movement of diffused Au atoms on the Si surface steps and the movement of Guinier-Presion-zone-like contrast observed for the segregation of An atoms on the (lll) Si plane, have been directly observed. These phenomena, which can be detected only at high temperatures, are presented in this paper. (C) 2003 Elsevier B.V. All rights reserved.
  • M Ishikawa, Y Kimura, H Suzuki, O Kida, T Tanigaki, T Sato, Y Saito, C Kaito
    JOURNAL OF CRYSTAL GROWTH 254 (1-2) 131 - 136 0022-0248 2003/06 [Not refereed][Not invited]
     
    The silicon core and carbon mantle particles were produced by using the advanced carbon coating method which enables direct covering with the carbon layer using an electron microscope. The growth of SiC crystal was observed upon heating at 500degreesC in vacuum. The growth process of SiC on both the carbon layer and silicon particles was directly observed by in situ observation. The inward movement of carbon into silicon began at the twinned part. The growth rate of SiC on the carbon mantle layer was estimated from in situ images and found to be 8 times faster than the growth rate of silicon carbide in silicon particles. (C) 2003 Elsevier Science B.V. All rights reserved.
  • Y Kimura, C Kaito
    JOURNAL OF CRYSTAL GROWTH 250 (3-4) 450 - 457 0022-0248 2003/04 [Not refereed][Not invited]
     
    Selective growth of WO2, W and WO3-x crystals from amorphous WO3 film by vacuum heating at 400-900degreesC was clarified. The grown WO3-x crystals were incommensurate structure based on crystallographic share structure. The growth process of WO2 crystal in the amorphous film was directly observed at high temperature in the electron microscope. The growth front of the WO2 crystal consumes WO3 microcrystallites with various orientations. The growth speed of the WO2 depended on WO3 microcrystallites orientation. The origin of the wavy growth front of WO2 was due to an orientation dependence of the WO3 microcrystallites. (C) 2003 Elsevier Science B.V. All rights reserved.
  • Dynamic behavior of a silicon oxide layer on silicon ultrafine particles
    Y Kimura, H Ueno, H Suzuki, T Sato, T Tanigaki, O Kido, C Kaito, Y Saito
    SURFACE REVIEW AND LETTERS 10 (2-3) 361 - 364 0218-625X 2003/04 [Not refereed][Not invited]
     
    In order to clarify the high-temperature behavior of a silicon oxide layer on the surface of Si ultrafine particles, the oxide layer has been studied using the atomic-resolution high-temperature stage of a transmission electron microscope. The natural oxide layer grown on Si ultrafine particles by exposure to air was an amorphous silicon oxide layer with a thickness of 1.5 nm. This oxide layer started to dissolve into the Si crystal upon heating at 500degreesC, and was fully dissolved into the Si crystal at 600degreesC in vacuum. When the specimen was cooled back to room temperature, the silicon oxide layer reappeared on the Si surface. This phenomenon, which can be detected only at high temperatures, is presented in this paper.
  • Atomic observation of the sublimation process of the Pb (111) surface
    T Tanigaki, H Suzuki, Y Kimura, C Kaito, Y Saito
    SURFACE REVIEW AND LETTERS 10 (2-3) 455 - 459 0218-625X 2003/04 [Not refereed][Not invited]
     
    The dynamic behavior of the sublimation process using ultrafine Pb particles produced by the gas evaporation technique was examined at the level of atomic resolution using a transmission electron microscope equipped with a real-time video-recording system. The ultrafine Pb particles coated with a carbon layer with a thickness of the order of 5 nm were prepared in the electron microscope by heating particles on carbon film at 300degreesC. Sublimation of the Pb particle covered with the carbon layer took place above 470degreesC, which is slightly higher than the melting point of Pb. Sublimation occurred at the surface with a higher surface energy. The sublimation process of the (111) surface was clearly observed at an atomic level. It was found that two- or four-atomic-layer step flow was observed at the (111) surface. At the (111) surface between the stacking faults, two-layer and successive one-layer sublimation occurred.
  • M Kurumada, H Suzuki, Y Kimura, Y Saito, C Kaito
    JOURNAL OF CRYSTAL GROWTH 250 (3-4) 444 - 449 0022-0248 2003/04 [Not refereed][Not invited]
     
    Dynamics of crystallization of amorphous antimony-selenium film deposited on carbon substrate have been studied by the high-resolution transmission electron microscopy. The amorphous film was suddenly crystallized at 200degreesC by heating in vacuum. By the electron beam irradiation crystallization occurred at the focused electron beam region in the amorphous film. The growth process of crystallization by electron beam irradiation was recorded on a video image at the atomic resolution mode. The growth front of crystallization showed nano-concave and -convex shapes. The recrystallization with the different orientation at the first grown crystal have been found, and discussed as the influence of remaining antimony crystallites at the first crystallized film region. (C) 2003 Elsevier Science B.V. All rights reserved.
  • Y Kimura, H Ueno, H Suzuki, T Sato, T Tanigaki, O Kido, C Kaito, Y Saito
    SURFACE REVIEW AND LETTERS 10 (2-3) 361 - 364 0218-625X 2003/04 [Refereed][Not invited]
     
    In order to clarify the high-temperature behavior of a silicon oxide layer on the surface of Si ultrafine particles, the oxide layer has been studied using the atomic-resolution high-temperature stage of a transmission electron microscope. The natural oxide layer grown on Si ultrafine particles by exposure to air was an amorphous silicon oxide layer with a thickness of 1.5 nm. This oxide layer started to dissolve into the Si crystal upon heating at 500degreesC, and was fully dissolved into the Si crystal at 600degreesC in vacuum. When the specimen was cooled back to room temperature, the silicon oxide layer reappeared on the Si surface. This phenomenon, which can be detected only at high temperatures, is presented in this paper.
  • T Chigai, T Yamamoto, C Kaito, Y Kimura
    ASTROPHYSICAL JOURNAL 587 (2) 771 - 776 0004-637X 2003/04 [Refereed][Not invited]
     
    The carrier of the 21 mum band observed in post-asymptotic giant branch (post-AGB) stars is examined. We analyze the infrared spectra of the TiC clusters measured by von Helden et al. in 2000 and determine the absorption efficiency Q in the 21 mum band. Using Q, we estimate the Ti/Si abundance ratios needed to realize the flux ratios of the 21 and 11 mum emission observed in the infrared spectra of the post-AGB stars exhibiting both 21 and 11 mum emission. In view of the nature of the TiC condensation by which TiC grains are quickly mantled by graphite, we calculate the emission spectra of the graphite-coated TiC grains and other possible types of core-mantle grains and compare with the observed spectra. Both the abundance and condensation considerations strongly suggest that TiC is an implausible carrier of the observed infrared 21 mum feature around carbon-rich post-AGB stars.
  • Y Kimura, Y Saito, C Kaito
    SURFACE SCIENCE 527 (1-3) L219 - L221 0039-6028 2003/03 [Not refereed][Not invited]
     
    The dynamic behavior of an amorphous carbon layer of 3 nm thickness on a SiC particle was examined at high temperature using a high-resolution electron microscope equipped with a real-times video recording system. It was found that the surface carbon layer began to solve into the SiC particle at 600 degreesC. The layer was completely solved into SiC crystal at 800 degreesC. The lattice image of SiC changed negligibly at high temperature. If the specimen was cooled back to room temperature, the carbon layer on the SiC particle was recovered. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Y Atou, H Suzuki, Y Kimura, T Sato, T Tanigaki, Y Saito, C Kaito
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 16 (2) 179 - 189 1386-9477 2003/02 [Not refereed][Not invited]
     
    Two methods for the preparation of TiO2 particles using the gas evaporation methods have been proposed. A method for selective growth of the anatase and/or rutile particles as well as a method of covering TiO2 particles with an SiO2 layer has been developed. The process of dissolving the SiO2 layer into TiO2 particles has been observed by an in situ observation using high-resolution electron microscopy. SiO2 layers of 5 nm order were dissolved completely into TiO2 particles of the order of 30 nm at 750degreesC. These SiO2 layers appeared again at room temperature on the surfaces of TiO2 particles. This phenomenon was observed only at a high temperature. By the use of the phenomenon of dissolving the SiO2 layer into TiO2 particles at high temperature, the growth of TiO2 particles covered with the SiO2 layer has been discussed. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Characteristic behavior of Bi clusters and growth process to the continuous film
    C. Kaito, Y. Kimura, S. Tominaga, S. Kimura, T. Nakada, Y. Saito
    Physics of Low-Dimensional Structures 5/6 1 - 8 2003 [Not refereed][Not invited]
  • T. Chigai, T. Yamamoto, C. Kaito, Y. Kimura
    The Astrophysical Journal 587 (2) 771 - 776 2003 [Not refereed][Not invited]
  • Demonstration of crystalline forsterite grain formation due to coalescence growth of Mg and SiO smoke particles
    C Kaito, Y Ojima, K Kamitsuri, O Kido, Y Kimura, H Suzuki, T Sato, T Nakada, Y Saito, C Koike
    METEORITICS & PLANETARY SCIENCE 38 (1) 49 - 57 1086-9379 2003/01 [Not refereed][Not invited]
     
    Experimental studies of coalescence between Mg grains and SiO grains in smoke reveal the direct production of crystalline forsterite grains. The present results also show that different materials can be produced by grain-grain collisions, which have been considered one of the models of grain formation in the interstellar medium. The fundamentals of coalescence growth in smoke, which have been developed in our series of experiments, are presented in this paper. Mg2Si polyhedral grains were obtained in a Mg grain-rich atmosphere. Mg2SiO4 polyhedral grains were obtained in a SiO grain-rich atmosphere. The IR spectra of the resultant grains showed the characteristics of crystalline forsterite.
  • H Nakano, A Kouchi, M Arakawa, Y Kimura, C Kaito, H Ohno, T Hondoh
    PROCEEDINGS OF THE JAPAN ACADEMY SERIES B-PHYSICAL AND BIOLOGICAL SCIENCES 78 (9) 277 - 281 0386-2208 2002/11 [Not refereed][Not invited]
     
    Based on experiments that model interstellar organic materials, we found that both C and N contents and IR spectra of insoluble organic materials in carbonaceous chondrites could be reproduced well by the aqueous alteration and the subsequent thermal metamorphism. The resulting sample shows strong evidence of diamond, which indicates that this process is an unexpected mechanism that might produce extensive amount of diamond in meteorites' parent bodies. Because this process requires neither high pressures nor energetic processes, the present results suggest an alternate origin of diamonds in meteorites.
  • H Suzuki, N Fukuzawa, T Tanigaki, T Sato, O Kido, Y Kimura, C Kaito
    JOURNAL OF CRYSTAL GROWTH 244 (2) 168 - 172 0022-0248 2002/10 [Not refereed][Not invited]
     
    The reduction process of tenorite whiskers grown on a copper mesh by heating in vacuum has been directly observed using a transmission electron microscope equipped with a real-time video-recording system. The coating of the carbon layer and reduction of the tenorite whisker covered with a carbon layer have also been captured in real time on video images. The growth process of an amorphous carbon tube has been elucidated. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Y Kimura, K Hanamoto, Y Nakayama, C Kaito
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 194 (2) 187 - 192 0168-583X 2002/08 [Not refereed][Not invited]
     
    In order to elucidate the effect of synchrotron radiation (SR) irradiation on crystal growth, crystallization of WO3 films has been performed in vacuum under SR irradiation. The main results were compared with the results of heat treatment of the same film. Upon SR irradiation for 80 s using a toroidal mirror, a catastrophic change occurred, i.e. W3O crystals (A-15 type) with a size of less than 30 nm appeared. Decomposition of the WO3 film started at above 750 degreesC during vacuum heating. W, WO2 and incommensurate WO3 crystals appeared. W3O crystal produced neither intense electron beam irradiation nor vacuum heating. These results will be discussed in terms of the differences caused by excitation with a SR beam, i.e. strong inner shell excitation and ionization of W and O may have taken place. (C) 2002 Elsevier Science B.V. All rights reserved.
  • T Kobayashi, Y Kimura, H Suzuki, T Sato, T Tanigaki, Y Saito, C Kaito
    JOURNAL OF CRYSTAL GROWTH 243 (1) 143 - 150 0022-0248 2002/08 [Not refereed][Not invited]
     
    Amorphous tin oxide films deposited on carbon substrates have been studied by high-resolution transmission electron microscopy. As-deposited film was composed of a mixture of microcrystallites of SnO, SnO2 and SnO3 with size of 2 nm. Crystallization took place above 450degreesC. SnO crystals appeared between 450degreesC and 500degreesC, whereas SnO2 crystals appeared above 550degreesC. The appearance of beta-tin crystals with the reduction of tin oxide has been verified using the heating stage of the electron microscope. A drop of liquid tin was recognized upon heating above 500degreesC. The difference in crystallization upon applying an electron beam, synchrotron radiation and heating in vacuum has been summarized and discussed with respect to the problem of the excitation of crystallites. (C) 2002 Elsevier Science B.V. All rights reserved.
  • M Sasaki, K Hanamoto, Y Kimura, C Kaito, H Miki, Y Nakayama
    REVIEW OF SCIENTIFIC INSTRUMENTS 73 (3) 1384 - 1386 0034-6748 2002/03 [Not refereed][Not invited]
     
    The effects of synchrotron radiation (SR) irradiation on the electrical properties of tin-doped In2O3 (ITO) thin films prepared by rf magnetron sputtering have been studied. A white SR beam focused by a cylindrical mirror was used to irradiate ITO thin films at doses of 0.35, 1.98, 3.50, and 6.64 mA h. We have achieved resistivity of 2x10(-4) Omega cm on ITO thin film at an irradiation dose of 3.5 mA h without extra heating. The mobility of the ITO films did not decrease after SR irradiation. The electrical properties in connection with the structural change due to SR are discussed. (C) 2002 American Institute of Physics.
  • Y Kimura, Y Saito, T Nakada, C Kaito
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 13 (1) 11 - 23 1386-9477 2002/01 [Not refereed][Not invited]
     
    Experimental studies on the mixing of alkali halide clusters of 200 nm sizes were performed systematically by the successive evaporation of different alkali halides on carbon substrates. The alkali halides used were NaCl, NaBr, KCl, KBr, KI, RbCl, RbBr, CsCl and CsBr. Intermixing took place independent of the crystal structure. It became evident that the limit of mixing was governed by the ratio of ionic radii. If the ratio of ionic radii between the cation and/or anion was more than 68%, intermixing occurred. It was also found that the crystal structure formed by intermixing between NaCl-type and CsCl-type structures becomes the NaCl type. If four different elements of cations and anions are involved, two mixture phases grew. The key elements of mixing were the nearest ionic radii. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Y Kimura, C Kaito, K Hanamoto, M Sasaki, S Kimura, T Nakada, Y Saito, Y Nakayama
    CARBON 40 (7) 1043 - 1050 0008-6223 2002 [Not refereed][Not invited]
     
    Growth of small carbyne crystals in a thin amorphous carbon film has been observed by high-resolution transmission electron microscopy (HRTEM). The as-deposited film was composed of diamond and graphite crystallites of size 1 nm. Circular alpha-phase carbyne crystals predominantly grew to 20 nm in size and transformed into (alpha+beta)-phase crystals with an elongated shape of 100 nm in length. The typical correlation during the transformation is (220)(alpha)//(301)((alpha+beta)) The c-axes of both grown crystals were oblique to the direction of the electron beam. The growth process of carbyne crystals will be discussed in terms of selective excitation of graphite crystallites by an SR beam. (C) 2002 Elsevier Science Ltd. All rights reserved.
  • Crystallization and selective growth of amorphous Y-Ba-Cu-O film
    T. Tanigaki, S. Ariumi, H. Suzuki, Y. Kimura, S. Kimura, T. Sato, N. Tsuda, T. Nakada, Y. Saito, C. Kaito
    Physics of Low-Dimensional Structures 11/12 77 - 84 2002 [Not refereed][Not invited]
  • Ordered alloy formation by the use of reaction between ultrafine particle and cluster
    T Tsurusako, T Tanigaki, H Suzuki, Y Kimura, T Sato, O Kido, Y Saito, C Kaito
    PHYSICS OF LOW-DIMENSIONAL STRUCTURES 7-8 77 - 86 0204-3467 2002 [Not refereed][Not invited]
     
    To observe the singularity of clusters and ultrafine particles in low dimensions, a new experiment has been started on the Au-Cu system. The diffusion of atoms in the cluster and ultrafine particles has been observed including the direct observation at the interface. The alloy formation temperature decreases by about 50degreesC compared with the film-ultrafine particle. The diffusion rate difference observed in bulk phase is preserved in the alloy formation process.
  • A new attempt on reduction of ultrafine oxide particles
    H. Suzuki, T. Tanigaki, T. Sato, O. Kido, Y. Atou, Y. Kimura, C. Kaito
    Physics of Low-Dimensional Structures 7/8 99 - 106 2002 [Not refereed][Not invited]
  • Y Kimura, C Kaito, K Hanamoto, M Sasaki, S Kimura, T Nakada, Y Saito, Y Nakayama
    CARBON 40 (7) 1043 - 1050 0008-6223 2002 [Refereed][Not invited]
     
    Growth of small carbyne crystals in a thin amorphous carbon film has been observed by high-resolution transmission electron microscopy (HRTEM). The as-deposited film was composed of diamond and graphite crystallites of size 1 nm. Circular alpha-phase carbyne crystals predominantly grew to 20 nm in size and transformed into (alpha+beta)-phase crystals with an elongated shape of 100 nm in length. The typical correlation during the transformation is (220)(alpha)//(301)((alpha+beta)) The c-axes of both grown crystals were oblique to the direction of the electron beam. The growth process of carbyne crystals will be discussed in terms of selective excitation of graphite crystallites by an SR beam. (C) 2002 Elsevier Science Ltd. All rights reserved.
  • T Tanigaki, S Ariumi, H Suzuki, Y Kimura, S Kimura, T Sato, N Tsuda, T Nakada, Y Saito, C Kaito
    PHYSICS OF LOW-DIMENSIONAL STRUCTURES 11-2 77 - 84 0204-3467 2002 [Refereed][Not invited]
     
    Amorphous Y-Ba-Cu-O films prepared by Ar ion sputtering at room temperature have been studied by high-resolution transmission electron microscopy (HRTEM). As-deposited film was composed of a mixture of microcrystallites of YBa2Cu3Ox, YBa2Cu4Ox, Y2BaCuOx, and Y2Ba4Cu7Ox phases with the size of 3-5 nm. The produced film was crystallized above 300degreesC by heating in air. The selective crystal growth of the above four phases was observed upon heating up to 600degreesC, which was a lower temperature than the general epitaxial growth temperature of Y-Ba-Cu-O film.
  • Y Kimura, T Kobayashi, K Hanamoto, M Sasaki, S Kimura, T Nakada, Y Nakayama, C Kaito
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 467 1221 - 1224 0168-9002 2001/07 [Not refereed][Not invited]
     
    In order to see the effect of SR irradiation on crystal growth., crystallization of tin oxide films has been performed in vacuum under SR irradiation, A thin amorphous tin oxide film 50 nm thick was prepared on the carbon substrate by vacuum evaporation of SnO2 power, A SnO crystal appeared between 450-500 degreesC upon vacuum heating, with a preferred orientation of (0 0 1). By SR irradiation using a cylindrical mirror for 20 s, the SnO crystal appeared with the preferred orientation of (1 1 1). The crystal with the crystallographic shear structure was grown by SR irradiation. This growth under a SR beam is discussed in terms of SR beam excitation of lone-pair electrons seen in the SnO crystal structure. (C). 2001 Elsevier Science B.V. All rights reserved.
  • C Kaito, Y Kimura, K Hanamoto, M Sasaki, S Kimura, T Nakada, Y Saito, C Koike, Y Nakayama
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 467 1217 - 1220 0168-9002 2001/07 [Not refereed][Not invited]
     
    Thin carbon films prepared by vacuum evaporation using the arc method were mounted on a standard electron microscope copper grid. They were irradiated by white synchrotron radiation (SR) beam by the use of cylindrical and toroidal mirrors. The irradiated film was examined using a high-resolution electron microscope alpha and alpha + beta mixture carbyne crystals were grown in round and the elongated shapes. The round crystals were composed of 5-10 nm crystallites of a carbyne form. The elongated crystal grew into a single crystal 100 nm in size. The c-axes of both grown crystals were oblique to the film. The growth of the carbynes was discussed as being the result of nucleation due to graphite microcrystallites formed by SR beam irradiation. (C) 2001 Elsevier Science B.V. All rights reserved.
  • K Hanamoto, A Hirai, M Sasaki, Y Kimura, K Miyatani, C Kaito, Y Nakayama
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 467 1213 - 1216 0168-9002 2001/07 [Not refereed][Not invited]
     
    The effect of SR irradiation on the crystal growth of indium oxide films prepared by electron-beam evaporation have been studied by X-ray diffraction and high-resolution electron microscopy. An as-deposited film showed In2O3 crystallites with a size of 2-10 nm. The crystallites were destroyed by SR irradiation under oxygen flow, SR irradiation without oxygen flow showed the growth of In2O3 crystallites up to 20 nm in size with accompanying deoxidation and indium-particle growth. The as-deposited film was composed of variously oriented particles. Periodic oxygen decomposition of the film preferentially took place on the (0 0 1)-oriented particle. (C) 2001 Elsevier Science B.V. All rights reserved.
  • C Kaito, A Ito, S Kimura, Y Kimura, Y Saito, T Nakada
    JOURNAL OF CRYSTAL GROWTH 218 (2-4) 259 - 264 0022-0248 2000/09 [Not refereed][Not invited]
     
    The growth of In2S3 and InS by vacuum evaporation of indium metal on the surface of molybdenite has been observed in the initial stage of film growth. By the increment of In2S3 particle size, InS was also produced. By the increase of the film thickness to more than 20 nm, indium crystal predominately grew. The topotactic relations among the substrate and sulfide are as follows: (0 0 0 1)(MoS2) parallel to(1 1 0)(In2S3), [1 0 (1) over bar 0](MoS2) parallel to[1 1 1](In2S3) or (0 0 0 1)(MoS2) parallel to(1 1 0)(In2S3), [1 0 (1) over bar 0](MoS2) parallel to[1 0 0](In2S3). (C) 2000 Elsevier Science B.V. All rights reserved.
  • T Nakao, T Nakada, Y Nakayama, K Miyatani, Y Kimura, Y Saito, C Kaito
    THIN SOLID FILMS 370 (1-2) 155 - 162 0040-6090 2000/07 [Not refereed][Not invited]
     
    In order to clarify the structure of indium oxide him containing tin and tin oxides, various In2O3 based films prepared by vacuum evaporation were studied using high-resolution electron microscope (HREM). Indium tin oxide (ITO) film was composed of In2O3 and SnO. SnO crystal also contained (110) or (101) crystallographic shear (CS) structures that indicate excess amounts of tin. The CS structure was also found in a commercial ITO film having the resistivity of 2 x 10(-4) Omega cm. (C) 2000 Elsevier Science S.A. All rights reserved.
  • Spontaneous Alkali Halide Formation by the Use of KBr-KCl System
    Y. Kimura, Y. Saito, T. Nakada, C. Kaito
    Physics of Low-Dimensional Structures 1/2 L1-L7  2000 [Not refereed][Not invited]
  • C Kaito, H Nakamura, S Kimura, Y Kimura, T Nakada, Y Saito
    THIN SOLID FILMS 359 (2) 283 - 287 0040-6090 2000/01 [Not refereed][Not invited]
     
    In order to clarify the structures of thin Cr films by their real space images, Cr films of various thicknesses, prepared using vacuum deposition, have been observed using a high resolution electron microscope. The amorphous chromium films were composed of microcrystallites of the order of 3 nm. The crystallite structure was delta-Cr. The well-known bcc chromium particles were observed in thick and large crystal particles. The stability of small particles is discussed. (C) 2000 Published by Elsevier Science S.A. All rights reserved.
  • C Kaito, H Nakamura, S Kimura, Y Kimura, T Nakada, Y Saito
    THIN SOLID FILMS 359 (2) 283 - 287 0040-6090 2000/01 [Refereed][Not invited]
     
    In order to clarify the structures of thin Cr films by their real space images, Cr films of various thicknesses, prepared using vacuum deposition, have been observed using a high resolution electron microscope. The amorphous chromium films were composed of microcrystallites of the order of 3 nm. The crystallite structure was delta-Cr. The well-known bcc chromium particles were observed in thick and large crystal particles. The stability of small particles is discussed. (C) 2000 Published by Elsevier Science S.A. All rights reserved.
  • Surface oxide on tin and indium ultrafine particles and their oxidation process
    C Kaito, T Nakao, Y Ato, Y Kimura, S Kimura, T Nakada, Y Saito
    PHYSICS OF LOW-DIMENSIONAL STRUCTURES 12 53 - 60 0204-3467 1999 [Not refereed][Not invited]
     
    The structure of surface oxide on tin and indium metallic particles and their oxidation process at a temperature higher than the melting point of the particles have been elucidated on the basis of observations using a high-resolution electron microscope (HREM). In the case of tin particles, the surface oxide layer spontaneously produced by exposure to air was composed of microcrystallites with the size of 1 similar to 2 nm. In the case of indium, the (222) crystal of In2O3 covered the surface of indium particles. In the oxidation of tin at a temperature higher than its melting point, crystal shear structure which were present as the metal-excess Sn3O2 or Sn4O3 oxides have been found. In the case of indium particles, a definite crystallographic correlation, i.e., In2O3 (111) // In(110), has also been observed during the solidification of central metal. The fundamental behaviors of low-dimensional In and Sn particles can be observed.

Books etc

Conference Activities & Talks

  • Formation experiments of cosmic dust analogues in microgravity environments  [Not invited]
    KIMURA Yuki
    33rd Grain Formation Workshop  2016/12
  • 航空機を用いた微小重力実験  [Not invited]
    木村勇気, 斎藤史明, 佐藤陽亮, 中坪俊一, 石塚紳之介, 山﨑智也
    第22回 低温科学研究所 技術部 技術報告会  2016/12
  • 鉄ニッケル合金基板を用いた FT 型触媒反応実験  [Not invited]
    KIMURA Yuki
    科研費新学術領域 分子進化 第12回ワークショップ  2016/10
  • In-situ TEM Observation Reveals Early Stages of Crystallization Governed by Singular Phenomena of Nanoparticles  [Not invited]
    Yuki Kimura, Tomoya Yamazaki
    The 18th International Conference on Crystal Growth and Epitaxy  2016/08
  • In-situ observation studies of nucleation and dissolution processes  [Not invited]
    KIMURA Yuki
    The 16th International Summer School on Crystal Growth  2016/08
  • 雪の昇華過程のその場観察と水・氷の均質核生成実験に向けて  [Not invited]
    KIMURA Yuki
    低温物質の界面・ナノ現象ワークショップ2016  2016/07
  • Advanced TEM studies give us new perspectives in water-mineral reactions  [Not invited]
    KIMURA Yuki
    International Workshop on Water-mineral Interactions  2016/07
  • Elucidating the early stages of protein crystallization by TEM  [Not invited]
    KIMURA Yuki
    Goldschmidt 2016  2016/06
  • Temperature dependence of reaction efficiency in the Fischer-Tropsh-type catalytic reaction on an iron substrate  [Not invited]
    KIMURA Yuki
    日本地球惑星科学連合2016年大会  2016/05
  • Nucleation experiment of alumina and silica from vapor phase using the sounding rocket S-520-30  [Not invited]
    木村勇気, 石塚紳之介, 山﨑智也, 左近樹, 田中今日子, 竹内伸介, 稲富裕光
    日本地球惑星科学連合2016年大会  2016/05
  • Nucleation of interstellar dust  [Invited]
    KIMURA Yuki
    International School of Crystallography for Space Sciences  2016/04
  • 鉄基板を触媒としたFT 反応の温度依存性  [Not invited]
    KIMURA Yuki
    科研費新学術領域 分子進化 第7回ワークショップ  2016/03
  • 透過電子顕微鏡を用いた溶液からの核生成の“その場”観察  [Not invited]
    KIMURA Yuki
    日本物理学会 第71回年次大会  2016/03
  • Nucleation experiment to understand formation of cosmic dust  [Invited]
    KIMURA Yuki
    Astrophysical Ices in the Lab  2016/03
  • 観測ロケットS-520-30号機を用いた宇宙ダストの再現実験  [Not invited]
    木村勇気, 石塚紳之介, 中坪俊一, 斎藤史明, 山﨑智也, 左近樹, 田中今日子, 竹内伸介, 稲富裕光
    第30回宇宙環境利用シンポジウム  2016/01
  • Microgravity experiments using S-520 sounding rockets to elucidate formation process of cosmic dust  [Not invited]
    KIMURA Yuki
    第16回宇宙科学シンポジウム  2016/01
  • 木村勇気、中坪 俊一、斎藤 史明、石塚 紳之介、山﨑 智也、稲富 裕光  [Not invited]
    木村勇気, 中坪 俊一, 斎藤 史明, 石塚 紳之介, 山﨑 智也, 稲富 裕光
    第21回 低温科学研究所 技術部 技術報告会  2015/12
  • Nucleation experiments under microgravity condition  [Not invited]
    KIMURA Yuki
    32nd Grain Formation Workshop  2015/12
  • Nucleation from a supersaturated vapor  [Not invited]
    Yuki Kimura, Kyoko K. Tanaka, Kouchi Akira, Naoki Watanabe, Shunichi Nakatsubo, Shinnosuke Ishizuka, Yuko Inatomi
    ILTS International Symposium on Low Temperature Science  2015/12
  • In-situ observation of nucleation from solution phase  [Not invited]
    KIMURA Yuki
    Japan-Slovenia Bilateral Symposium of Transmission Electron Microscopy  2015/11
  • Experimental results of sounding rocket S-520-30 and future plan  [Not invited]
    KIMURA Yuki
    大気球シンポジウム  2015/11
  • ナノ粒子~小さな結晶の不思議な振る舞い~  [Invited]
    木村 勇気
    平成27年度低温科学研究所公開講座  2015/11
  • Homogeneous nucleation experiments reveal formation process of cosmic dust particles  [Invited]
    KIMURA Yuki
    第45回結晶成長国内会議  2015/10
  • Nucleation and dissolution processes studied by in-situ observation using transmission electron microscopy  [Invited]
    KIMURA Yuki
    Department lecture of Jozef Stefan Institute  2015/10
  • Nucleation processes studied by in-situ observation using transmission electron microscopes  [Invited]
    KIMURA Yuki
    International Discussion Meeting on Crystal Growth (39th Toronkai)  2015/09
  • Assembling interferometers and in-situ observation of ambient phases and solid-liquid interfaces  [Invited]
    KIMURA Yuki
    International Discussion Meeting on Crystal Growth (39th Toronkai)  2015/09
  • Gravity Effects on the Formation of Ultrafine Particles by the Gas Evaporation Method  [Not invited]
    KIMURA Yuki
    The Joint Conference of 6th International Symposium on Physical Science in Space (ISPS-6) and 10th International Conference on Two-Phase Systems for Space and Ground Applications (ITTW2015)  2015/09
  • Electron Holography Unveiled Formation Process of Extraterrestrial Magnetite  [Invited]
    Yuki Kimura, Kazuo Yamamoto, Takeshi Sato
    Microscopy & Microanalysis  2015/08
  • Direct Liquid In Situ TEM Obseration of a Libing Protein Crystal  [Invited]
    KIMURA Yuki
    Microscopy & Microanalysis  2015/08
  • Nucleation governing mineral evolution in space  [Invited]
    KIMURA Yuki
    Space Science Colloquium  2015/07
  • ナノ粒子の生成過程と溶解過程  [Invited]
    木村 勇気
    低温研セミナー  2015/06
  • Reproduction experiment of molecular formation based on Fischer-Tropsh-type catalytic reaction in the early solar nebula  [Not invited]
    KIMURA Yuki, YAMAZAKI Tomoya, TSUCHIYAMA Akira, NAGAHARA Hiroko, HAMA Tetsuya, HIDAKA Hiroshi, WATANABE Naoki, KOUCHI Akira
    JPGU meeting 2015  2015/05
  • TEM observation of dissolution process of sodium chlorate nanocrystals  [Not invited]
    KIMURA Yuki, YAMAZAKI Tomoya, SATO Hisao
    JPGU meeting 2015  2015/05
  • 左近樹, 酒向重行, 大澤亮, 中村友彦, 下西隆, 宮田隆志, 高橋英則, 島本早也佳, 尾中敬, 野沢貴也, 木村勇気, 小笹隆司, 藤吉拓哉, 植村誠, 新井彰
    日本天文学会年会講演予稿集  2014/02
  • 石塚紳之介, 木村勇気, 中村智樹
    日本天文学会年会講演予稿集  2013/08
  • 稲富裕光, 木村勇気, 塚本勝男, 竹内伸介, 石井信明
    応用物理学会春季学術講演会講演予稿集(CD-ROM)  2013/03
  • 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
  • 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
  • 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
  • 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
  • 木村勇気, 田中今日子, 竹内伸介, 塚本勝男, 三浦均, 稲富裕光
    結晶成長国内会議予稿集(CD-ROM)  2013
  • 観測ロケットS-520-28号機を用いた微小重力環境における鉄蒸気からの均質核生成実験  [Not invited]
    日本地球惑星科学連合2013年大会  2013
  • Nucleation and growth take into account physical properties of nanoparticles  [Not invited]
    The 2013 Collaborative Conference on Crystal Growth (3CG)  2013
  • Nucleation experiments of iron dust under microgravity  [Not invited]
    Cosmic Dust VI  2013
  • Nucleation experiment in vapor phase under microgravity using the sounding rocket S-520-28  [Not invited]
    17th International Conference on Crystal Growth and Epitaxy  2013
  • Nucleation and growth of cosmic nanominerals based on size effects in mesoscale  [Not invited]
    17th International Conference on Crystal Growth and Epitaxy  2013
  • Microgravity experiment using the sounding rocket S-520-28 for understanding a formation process of cosmic dust  [Not invited]
    3rd International Conference on Crystallogenesis and Mineralogy  2013
  • 観測ロケットS-520-28号機を用いた微小重力環境における鉄蒸気からの均質核生成実験  [Not invited]
    日本地球惑星科学連合2013年大会  2013
  • Nucleation and growth take into account physical properties of nanoparticles  [Not invited]
    The 2013 Collaborative Conference on Crystal Growth (3CG)  2013
  • Nucleation experiments of iron dust under microgravity  [Not invited]
    Cosmic Dust VI  2013
  • Nucleation experiment in vapor phase under microgravity using the sounding rocket S-520-28  [Not invited]
    17th International Conference on Crystal Growth and Epitaxy  2013
  • Nucleation and growth of cosmic nanominerals based on size effects in mesoscale  [Not invited]
    17th International Conference on Crystal Growth and Epitaxy  2013
  • Microgravity experiment using the sounding rocket S-520-28 for understanding a formation process of cosmic dust  [Not invited]
    3rd International Conference on Crystallogenesis and Mineralogy  2013
  • 左近樹, 酒向重行, 大澤亮, 中村友彦, 下西隆, 宮田隆志, 高橋英則, 尾中敬, 野沢貴也, 木村勇気, 小笹隆司, 藤吉拓哉, 植村誠, 新井彰
    日本天文学会年会講演予稿集  2012/08
  • 木村勇気
    日本物理学会講演概要集  2012/03
  • 木村勇気, 稲富裕光, 三浦均, 田中今日子, 左近樹, 野沢貴也, 中村智樹, 塚本勝男
    宇宙利用シンポジウム  2012/03
  • 左近樹, 酒向重行, 大澤亮, 下西隆, 宮田隆志, 高橋英則, 尾中敬, 野沢貴也, 木村勇気, 小笹隆司, 藤吉拓哉, 植村誠, 新井彰
    日本天文学会年会講演予稿集  2012/02
  • 微小重力環境利用に向けた宇宙ダスト生成の“その場”観察実験  [Not invited]
    木村勇気, 稲富裕光, 田中今日子, 真木孝雄, 三浦均, 左近樹, 野沢貴也, 塚本勝男
    日本結晶成長学会誌  2012
  • 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
  • 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
  • 大島嘉文, 三浦均, 木村勇気, 佐藤久夫, 塚本勝男
    結晶成長国内会議予稿集(CD-ROM)  2012
  • メゾスコピック領域の物性を考慮した宇宙ダストの結晶成長  [Not invited]
    日本物理学会2012年春季大会  2012
  • 宇宙ダストを模擬した核生成の“その場”観察実験  [Not invited]
    文部科学省 先端研究施設共用イノベーション創出事業ナノテクノロジー・ネットワーク 中部地区ナノテク総合支援:ナノ材料創製加工と先端機器分析 平成23年度成果報告会  2012
  • Formation process of colloidal magnetite in the Tagish Lake meteorite  [Not invited]
    Workshop on Minerals-Water-Organics in the Early Solar System  2012
  • 航空機による微小重力環境を利用した核生成の“その場”観察実験  [Not invited]
    日本地球惑星科学連合2012年大会  2012
  • 溶液成長における核生成と溶解過程のTEM中“その場”観察  [Not invited]
    日本地球惑星科学連合2012年大会  2012
  • Simultaneous determination of sticking probability and surface free energy by the homogeneous nucleation experiment  [Not invited]
    3rd Workshop of Nucleation Related to Cosmic Dust & its contribution to the organic formation in 4.6 billion years ago  2012
  • Simultaneous determination of surface free energy and sticking probability based on formation experiment of cosmic dust and nucleation theories  [Not invited]
    The 5th meeting on Cosmic Dust  2012
  • 宇宙における微粒子生成  [Not invited]
    平成24年度東北大通研共同プロジェクト研究会プログラム、微粒子プラズマの応用に関する基礎研究  2012
  • ダスト生成に重要な吸着係数と表面自由エネルギーの同時決定  [Not invited]
    日本惑星科学会 2012年秋季講演会  2012
  • In-situ observation of nucleation and growth environment of cosmic dust analogues using an interferogram in laboratory  [Not invited]
    Achievements of G-COE Program for Earth and Planetary Dynamics and the Future Perspectives  2012
  • Dual-wavelength interferometric observation of homogeneous nucleation from supercooled vapor under 1G and μG  [Not invited]
    9th China-Japan-Korea Workshop on Microgravity Sciences, Asian Microgravity Pre-Symposium  2012
  • メゾスコピック領域の物性を考慮した宇宙ダストの結晶成長  [Not invited]
    日本物理学会2012年春季大会  2012
  • 宇宙ダストを模擬した核生成の“その場”観察実験  [Not invited]
    文部科学省 先端研究施設共用イノベーション創出事業ナノテクノロジー・ネットワーク 中部地区ナノテク総合支援:ナノ材料創製加工と先端機器分析 平成23年度成果報告会  2012
  • Formation process of colloidal magnetite in the Tagish Lake meteorite  [Not invited]
    Workshop on Minerals-Water-Organics in the Early Solar System  2012
  • 航空機による微小重力環境を利用した核生成の“その場”観察実験  [Not invited]
    日本地球惑星科学連合2012年大会  2012
  • 溶液成長における核生成と溶解過程のTEM中“その場”観察  [Not invited]
    日本地球惑星科学連合2012年大会  2012
  • Simultaneous determination of sticking probability and surface free energy by the homogeneous nucleation experiment  [Not invited]
    3rd Workshop of Nucleation Related to Cosmic Dust & its contribution to the organic formation in 4.6 billion years ago  2012
  • Simultaneous determination of surface free energy and sticking probability based on formation experiment of cosmic dust and nucleation theories  [Not invited]
    The 5th meeting on Cosmic Dust  2012
  • 宇宙における微粒子生成  [Not invited]
    平成24年度東北大通研共同プロジェクト研究会プログラム、微粒子プラズマの応用に関する基礎研究  2012
  • ダスト生成に重要な吸着係数と表面自由エネルギーの同時決定  [Not invited]
    日本惑星科学会 2012年秋季講演会  2012
  • In-situ observation of nucleation and growth environment of cosmic dust analogues using an interferogram in laboratory  [Not invited]
    Achievements of G-COE Program for Earth and Planetary Dynamics and the Future Perspectives  2012
  • Dual-wavelength interferometric observation of homogeneous nucleation from supercooled vapor under 1G and μG  [Not invited]
    9th China-Japan-Korea Workshop on Microgravity Sciences, Asian Microgravity Pre-Symposium  2012
  • 木村勇気, 田中今日子, 三浦均, 稲富裕光, 塚本勝男
    日本物理学会講演概要集  2011/08
  • 仙波稔己, 三浦均, 木村勇気, 塚本勝男
    コロイドおよび界面化学討論会講演要旨集  2011/08
  • 羽馬哲也, 渡部直樹, 香内晃, 木村勇気, PIRRONELLO V
    日本物理学会講演概要集  2011/03
  • 木村勇気, 田中今日子, 三浦均, 塚本勝男, 稲富裕光
    宇宙利用シンポジウム  2011/03
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 荒木優希, 木村勇気, 塚本勝男, 高木良介, 宮下知幸, 大藪範昭, 小林圭, 山田啓文
    結晶成長国内会議予稿集(CD-ROM)  2011
  • 超高過飽和ガスから生成するダスト類似物の均質核形成と接合成長  [Not invited]
    日本地球惑星科学連合2011年大会  2011
  • 高速“その場”観察による気相中でのパルス的均質核形成プロセス  [Not invited]
    日本地球惑星科学連合2011年大会  2011
  • Separate process of nucleation, coalescence and growth in vapor phase  [Not invited]
    International conference on materials for advanced teqhunologies (ICMAT) Symposium DD: CGCT-5-Fundamentals of Crystallization and Low Dimensional Crystalization  2011
  • Condensation of Cosmic Dust far from equilibrium condition  [Not invited]
    Asia Oceania Geosciences Society 8th Annual Meeting  2011
  • Agreement of experiment and theory in homogeneous nucleation  [Not invited]
    74th Annual Meeting of the Meteoritical Society  2011
  • Double Wavelength Interferometry for Direct Observation of Homogeneous Nucleation in Vapor Phase  [Not invited]
    XXII Congress and General Assembly International Union of Crystallography (IUCr2011)  2011
  • 二波長干渉計による気相からの均質核生成のその場観察実験  [Not invited]
    日本物理学会2011年秋季大会  2011
  • Homogeneous nucleation and growth of nanoparticles in vapor phase  [Not invited]
    BIT’s 1st Annual World Congress of Nano-Science & Technology  2011
  • TEMを用いた液中“その場”観察:塩素酸ナトリウムの核生成  [Not invited]
    第41回結晶成長国内会議  2011
  • Interferometric Direct Observation of Nanocrystal Formation via Homogeneous Nucleation in Vapor Phase  [Not invited]
    The 20th Nisshin Engineering Particle Technology International Seminar (NEPTIS-20), Modeling of Nucleation and Growth on Crystallization Processes  2011
  • 超高過飽和ガスから生成するダスト類似物の均質核形成と接合成長  [Not invited]
    日本地球惑星科学連合2011年大会  2011
  • 高速“その場”観察による気相中でのパルス的均質核形成プロセス  [Not invited]
    日本地球惑星科学連合2011年大会  2011
  • Separate process of nucleation, coalescence and growth in vapor phase  [Not invited]
    International conference on materials for advanced teqhunologies (ICMAT) Symposium DD: CGCT-5-Fundamentals of Crystallization and Low Dimensional Crystalization  2011
  • Condensation of Cosmic Dust far from equilibrium condition  [Not invited]
    Asia Oceania Geosciences Society 8th Annual Meeting  2011
  • Agreement of experiment and theory in homogeneous nucleation  [Not invited]
    74th Annual Meeting of the Meteoritical Society  2011
  • Double Wavelength Interferometry for Direct Observation of Homogeneous Nucleation in Vapor Phase  [Not invited]
    XXII Congress and General Assembly International Union of Crystallography (IUCr2011)  2011
  • 二波長干渉計による気相からの均質核生成のその場観察実験  [Not invited]
    日本物理学会2011年秋季大会  2011
  • Homogeneous nucleation and growth of nanoparticles in vapor phase  [Not invited]
    BIT’s 1st Annual World Congress of Nano-Science & Technology  2011
  • TEMを用いた液中“その場”観察:塩素酸ナトリウムの核生成  [Not invited]
    第41回結晶成長国内会議  2011
  • Interferometric Direct Observation of Nanocrystal Formation via Homogeneous Nucleation in Vapor Phase  [Not invited]
    The 20th Nisshin Engineering Particle Technology International Seminar (NEPTIS-20), Modeling of Nucleation and Growth on Crystallization Processes  2011
  • 杉浦悠紀, 木村勇気, 三浦均, 小沼一雄, 塚本勝男
    無機リン化学討論会講演予稿集  2010/10
  • 木村勇気, 塚本勝男
    日本物理学会講演概要集  2010/08
  • HAMA Tetsuya, KIMURA Yuki, KOUCHI Akira, WATABE Naoki
    原子衝突研究協会年会講演概要集  2010/08
  • A terminal of PAH evolution  [Not invited]
    215th Meeting of the American Astronomical Society  2010
  • Synthesis of organic hollow globules based on singular phenomena of nanoparticles  [Not invited]
    The 41th Lunar and Planetary Science Conference  2010
  • 干渉法を用いたナノ粒子凝縮過程の観察  [Not invited]
    日本地球惑星科学連合2010年大会  2010
  • プラズマを用いた宇宙固体微粒子の再現実験  [Not invited]
    日本地球惑星科学連合2010年大会  2010
  • Silicate Condensation Experiments in a Hydrogen Dominant Gas and Its Thermal History  [Not invited]
    73rd Annual Meeting of the Meteoritical Society  2010
  • Condensation Takes Place in Far from Equilibrium Condition  [Not invited]
    73rd Annual Meeting of the Meteoritical Society  2010
  • Experimental demonstration of a forsterite cycle from evolved stars to the solar system  [Not invited]
    The 20th General Meeting of the International Mineralogical Association  2010
  • In-situ observation by interferometer during condensation of smoke particles  [Not invited]
    The 20th General Meeting of the International Mineralogical Association  2010
  • A terminal of PAH evolution  [Not invited]
    215th Meeting of the American Astronomical Society  2010
  • Synthesis of organic hollow globules based on singular phenomena of nanoparticles  [Not invited]
    The 41th Lunar and Planetary Science Conference  2010
  • 干渉法を用いたナノ粒子凝縮過程の観察  [Not invited]
    日本地球惑星科学連合2010年大会  2010
  • プラズマを用いた宇宙固体微粒子の再現実験  [Not invited]
    日本地球惑星科学連合2010年大会  2010
  • Silicate Condensation Experiments in a Hydrogen Dominant Gas and Its Thermal History  [Not invited]
    73rd Annual Meeting of the Meteoritical Society  2010
  • Condensation Takes Place in Far from Equilibrium Condition  [Not invited]
    73rd Annual Meeting of the Meteoritical Society  2010
  • Experimental demonstration of a forsterite cycle from evolved stars to the solar system  [Not invited]
    The 20th General Meeting of the International Mineralogical Association  2010
  • In-situ observation by interferometer during condensation of smoke particles  [Not invited]
    The 20th General Meeting of the International Mineralogical Association  2010
  • 齊藤碧, 木村勇気
    日本天文学会年会講演予稿集  2009/08
  • 木村勇気, NUTH Joseph A.,III
    日本天文学会年会講演予稿集  2009/08
  • 渡部直樹, 香内晃, 木村勇気
    日本物理学会講演概要集  2009/08
  • 野澤純, 塚本勝男, 木村勇気, 甲野藤真
    日本物理学会講演概要集  2009/08
  • NOZAWA JUN, TSUKAMOTO KATSUO, KONOTO MAKOTO, KIMURA YUKI
    結晶成長国内会議予稿集  2009
  • KIMURA YUKI, NUTH JOSEPH A.,III
    結晶成長国内会議予稿集  2009
  • 水素原子の表面拡散は速いか?:CO固体表面の場合  [Not invited]
    日本地球惑星科学連合2009年大会  2009
  • Crystallization of silicate nanoparticles at lower temperature  [Not invited]
    International School of Crystallization  2009
  • Formation of Magnesium Silicates is Limited around Evolved Stars  [Not invited]
    The 214th Meeting of the American Astronomical Society  2009
  • 実験から導かれたシリケイト微粒子の新しい生成過程  [Not invited]
    日本天文学会2009年秋季年会  2009
  • ケイ酸塩ダストの新しい生成シナリオ  [Not invited]
    日本惑星科学会2009年秋季講演会  2009
  • 晩期星における珪酸塩ダスト生成の再現実験  [Not invited]
    第27回Grain Formation Workshop / 平成21年度銀河のダスト研究会  2009
  • 気相実験が示す“かんらん石”宇宙ダスト粒子の起源  [Not invited]
    第39回結晶成長国内会議  2009
  • 水素原子の表面拡散は速いか?:CO固体表面の場合  [Not invited]
    日本地球惑星科学連合2009年大会  2009
  • Crystallization of silicate nanoparticles at lower temperature  [Not invited]
    International School of Crystallization  2009
  • Formation of Magnesium Silicates is Limited around Evolved Stars  [Not invited]
    The 214th Meeting of the American Astronomical Society  2009
  • 実験から導かれたシリケイト微粒子の新しい生成過程  [Not invited]
    日本天文学会2009年秋季年会  2009
  • ケイ酸塩ダストの新しい生成シナリオ  [Not invited]
    日本惑星科学会2009年秋季講演会  2009
  • 晩期星における珪酸塩ダスト生成の再現実験  [Not invited]
    第27回Grain Formation Workshop / 平成21年度銀河のダスト研究会  2009
  • 気相実験が示す“かんらん石”宇宙ダスト粒子の起源  [Not invited]
    第39回結晶成長国内会議  2009
  • 木村勇気, 宮下徹平, 熊本明仁, 齊藤碧, 墻内千尋
    日本天文学会年会講演予稿集  2008/02
  • 木村勇気
    日本惑星科学会秋季講演会予稿集  2007
  • YANAGA HIDEOMI, KUMAMOTO AKIHITO, KIMURA YUKI, KAITO CHIHIRO
    結晶成長国内会議予稿集  2007
  • 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
  • YAMASHITA TEPPEI, KIMURA YUKI, KIDO OSAMU, KUMAMOTO AKIHITO, KAITO CHIHIRO
    結晶成長国内会議予稿集  2007
  • NIINA KENJI, KUMAMOTO AKIHITO, KIMURA YUKI, KAITO CHIHIRO
    結晶成長国内会議予稿集  2007
  • KUMAMOTO AKIHITO, KIMURA YUKI, KAITO CHIHIRO, SAITO YOSHIO
    結晶成長国内会議予稿集  2007
  • YOKOYAMA KAORI, YAMASHITA TEPPEI, KUMAMOTO AKIHITO, KIMURA YUKI, KOIKE CHIYOE, KAITO CHIHIRO
    結晶成長国内会議予稿集  2007
  • ADACHI SHUNSUKE, KUMAMOTO AKIHITO, SHINTAKU MASAYUKI, KIMURA YUKI, KINUTA YASUHIKO, KAITO CHIHIRO
    日本結晶成長学会誌  2006/11
  • KUMAMOTO AKIHITO, SHINTAKU MASAYUKI, KURUMADA MAMI, KIDO OSAMU, KIMURA YUKI, KAITO CHIHIRO
    日本結晶成長学会誌  2006/11
  • KIMURA YUKI, NUTH JOSEPH A, III, CHAKRABORTY SUBRATA, THIEMENS MARK H
    日本結晶成長学会誌  2006/11
  • 木村勇気, NUTH Joseph A.,III
    日本天文学会年会講演予稿集  2006/08
  • 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
  • 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
  • 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
  • 木村勇気, かき内千尋
    日本惑星科学会秋季講演会予稿集  2003/10
  • 木村勇気, 池上亜紀美, 鈴木仁志, かき内千尋
    日本惑星科学会秋季講演会予稿集  2003/10
  • 木村勇気, 佐藤岳志, かき内千尋
    日本惑星科学会秋季講演会予稿集  2003/10
  • 佐藤岳志, 上辻勝也, 木村勇気, 鈴木仁志, 谷垣俊明, 城戸修, 車田真実, かい内千尋, 塚本勝男
    日本岩石鉱物鉱床学会学術講演会講演要旨集  2003/09
  • 上辻勝也, かい内千尋, 木村勇気, 鈴木仁志, 佐藤岳志, 谷垣俊明, 城戸修, 車田真実, 塚本勝男
    日本岩石鉱物鉱床学会学術講演会講演要旨集  2003/09
  • SUZUKI HITOSHI, SATO TAKESHI, KIMURA YUKI, SAITO YOSHIO, KAITO CHIHIRO
    日本結晶成長学会誌  2003/07
  • KIDO OSAMU, SASAKI SHIN'ICHI, KURUMADA MAMI, SUZUKI HITOSHI, KIMURA YUKI, SAITO YOSHIO, KAITO CHIHIRO
    日本結晶成長学会誌  2003/07
  • IKEGAMI AKIMI, KIMURA YUKI, SUZUKI HITOSHI, SAITO YOSHIO, KAITO CHIHIRO
    日本結晶成長学会誌  2003/07
  • KIMURA YUKI, TANIGAKI TOSHIAKI, SUZUKI HITOSHI, SATO TAKESHI, KAITO CHIHIRO
    日本結晶成長学会誌  2003/07
  • KAMITSUJI KATSUYA, SUZUKI HITOSHI, KIMURA YUKI, SAITO YOSHIO, KAITO CHIHIRO
    日本結晶成長学会誌  2003/07
  • SASAKI SHIN'ICHI, KIMURA YUKI, SAITO YOSHIO, TAKEDA ATSUSHI, KAITO CHIHIRO
    日本結晶成長学会誌  2003/07
  • KURUMADA MAMI, KIMURA YUKI, SUZUKI HITOSHI, KIDO OSAMU, SAITO YOSHIO, KAITO CHIHIRO
    日本結晶成長学会誌  2003/07
  • 香内晃, 木村勇気, かい内千尋
    日本惑星科学会秋季講演会予稿集  2002/10
  • 中野英之, 香内晃, 荒川政彦, 木村勇気, かい内千尋, 大野浩, 本堂武夫
    日本惑星科学会秋季講演会予稿集  2002/10
  • 木村勇気, かい内千尋
    日本惑星科学会秋季講演会予稿集  2002/10
  • 佐藤岳志, 斎藤嘉夫, 木村勇気, 鈴木仁志, かい内千尋
    日本惑星科学会秋季講演会予稿集  2002/10
  • KAMITSUJI KATSUYA, SAITO YOSHIO, SUZUKI HITOSHI, KIMURA YUKI, KAITO CHIHIRO
    日本結晶成長学会誌  2002/07
  • ISHIKAWA YOSUKE, KIMURA YUKI, SUZUKI HITOSHI, SAITO YOSHIO, KAITO CHIHIRO
    日本結晶成長学会誌  2002/07
  • KIMURA YUKI, KAITO CHIHIRO
    日本結晶成長学会誌  2002/07
  • KIDO OSAMU, SHINTAKU MASAYUKI, KIMURA JUN, KIMURA YUKI, SUZUKI HITOSHI, SAITO YOSHIO, KAITO CHIHIRO
    日本結晶成長学会誌  2002/07
  • SATO TAKASHI, SAITO YOSHIO, KIMURA YUKI, SUZUKI HITOSHI, KAITO CHIHIRO
    日本結晶成長学会誌  2002/07
  • ISHIKAWA MANABU, KIMURA YUKI, SUZUKI HITOSHI, SAITO YOSHIO, KAITO CHIHIRO
    日本結晶成長学会誌  2002/07
  • TANAKA SHUJI, KIMURA YUKI, SUZUKI HITOSHI, SAITO YOSHIO, KAITO CHIHIRO
    日本結晶成長学会誌  2002/07
  • KIMURA YUKI, KAITO CHIHIRO
    日本天文学会年会講演予稿集  2002
  • 木村勇気, 中尾智子, 上野洋, 斎藤嘉夫, かき内千尋
    日本惑星科学会秋季講演会予稿集  2001/10
  • 佐々木宗生, 花元克巳, 木村勇気, 三木秀二郎, 墻内千尋, 中山康之
    応用物理学関係連合講演会講演予稿集  2001/03
  • 木村勇気, 花本克巳, 佐々木宗生, 木村誠二, 中田俊隆, 斎藤嘉夫, 小池千代枝, 中山康之, しょう内千尋
    日本惑星科学会秋季講演会予稿集  2000/10
  • TANIGAKI TOSHIAKI, KIMURA YUKI, KIMURA SEIJI, SAITO YOSHIO, KAITO CHIHIRO
    日本結晶成長学会誌  2000/07
  • KIMURA YUKI, HANAMOTO KATSUMI, NAKAYAMA YASUYUKI, KAITO CHIHIRO
    日本結晶成長学会誌  2000/07
  • KOBAYASHI TAKAHITO, KIMURA YUKI, HANAMOTO KATSUMI, NAKAYAMA YASUYUKI, KAITO CHIHIRO
    日本結晶成長学会誌  2000/07
  • 木村勇気, 木村誠二, 中田俊隆, 斎藤嘉夫, かい内千尋
    日本物理学会講演概要集  1999/09
  • KIMURA YUKI, KIMURA SEIJI, NAKADA TOSHITAKA, SAITO YOSHIO, KAITO CHIHIRO
    日本結晶成長学会誌  1999/07
  • 木村勇気, 木村誠二, 斎藤嘉夫, かい内千尋, 中田俊隆
    日本物理学会講演概要集  1999/03
  • 有機分子進化におけるFT反応の寄与  [Not invited]
    KIMURA Yuki
    新学術領域「宇宙分子進化」全体集会

Works

  • 気相からの核形成と宇宙ダスト
    2013 -2014
  • 気相からの核形成と宇宙ダスト
    2013 -2014
  • 気相からの核形成と宇宙ダスト
    2012 -2013
  • 気相からの核形成と宇宙ダスト
    2012 -2013
  • 宇宙の塵(ちり)の不思議なでき方
    2011 -2012
  • 気相からの核形成と宇宙ダスト
    2011 -2012
  • 宇宙の塵(ちり)の不思議なでき方
    2011 -2012
  • 気相からの核形成と宇宙ダスト
    2011 -2012
  • 液体のように振舞う固体:ナノ領域の拡散現象と天文学
    2009 -2012
  • 液体のように振舞う固体:ナノ領域の拡散現象と天文学
    2009 -2012
  • 月面基地建設の為の月資源からの酸素抽出とセメント製造、セメントペーストの流動性予測及び月コンクリート迅速評価の基礎的研究
    2009 -2010
  • 原始惑星系円盤における低温結晶成長過程
    2009 -2010
  • ナノ粒子の特異現象を取り入れたその場観察実験による宇宙ダスト生成過程の解明
    2009 -2010
  • 液体のように振舞う固体:ナノ領域の拡散現象と天文学
    2009 -2010
  • Nano Dust in the Solar System: Formation, Interactions and Detection
    2009 -2010
  • 月面基地建設の為の月資源からの酸素抽出とセメント製造、セメントペーストの流動性予測及び月コンクリート迅速評価の基礎的研究
    2009 -2010
  • 原始惑星系円盤における低温結晶成長過程
    2009 -2010
  • ナノ粒子の特異現象を取り入れたその場観察実験による宇宙ダスト生成過程の解明
    2009 -2010
  • 液体のように振舞う固体:ナノ領域の拡散現象と天文学
    2009 -2010
  • Nano Dust in the Solar System: Formation, Interactions and Detection
    2009 -2010

MISC

  • Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Katsuo Tsukamoto, Atsushi Yamazaki  AMERICAN MINERALOGIST  98-  (1)  262  -270  2013/01  [Not refereed][Not invited]
     
    Phase transformation of amorphous calcium carbonate (ACC) into vaterite and its subsequent stability was investigated at a constant pH (similar to 8.2), ionic strength, and temperature that simulated the biological environment. Solutions containing the same concentrations of CaCl2, Na2CO3, and tris(hydroxymethyl)aminomethane buffer and various concentrations of PO4 (0-62.5 mu M) were prepared, and precipitates in the solutions were sampled at a constant interval to observe the morphology and type of calcium carbonate polymorphs that appeared. The change in the Ca-ion concentration over time, which served as a guide for phase transformation of ACC into crystalline phases, was measured in relation to the PO4 concentration. The starting time of phase transformation was at the minimum point when the concentration was similar to 2-3 mu M. Vaterite spherulites consisting of needle-like crystals (0.5-2 mu m in length) formed only in this PO4 range and survived the experimental procedure (similar to 2.5 h). In contrast, the starting time of phase transformation increased exponentially with the PO4 concentration when it was higher than 5 mu M. The vaterite spherulites and calcite crystals co-precipitated, and both polymorphs grew over time. The PO4 was shown to be an accelerator for phase transformation from ACC into vaterite at low concentrations (Ca/PO4 molar ratio <3000) and an inhibitor for transformation at high concentrations. We investigated the kinetics of vaterite formation in the presence of PO4 and derived an advanced concept for cluster-based phase transformation. This investigation showed that the appearance and stability of calcium carbonate polymorphs is easily controlled by adjusting the PO4 concentration.
  • Tetsuya Hama, Kazuaki Kuwahata, Naoki Watanabe, Akira Kouchi, Yuki Kimura, Takeshi Chigai, Valerio Pirronello  ASTROPHYSICAL JOURNAL  757-  (2)  185  -196  2012/10  [Not refereed][Not invited]
     
    To understand elementary processes leading to H-2 formation, and the hydrogenation and deuteration reactions of adsorbed species on dust grains in dense clouds, we experimentally investigated the diffusion of atomic hydrogen and deuterium on amorphous solidwater (ASW) at temperatures of 8-15 K. The present study extended our previous study for selective detections of H and D atoms, and of H-2 (J = 0 and 1) and D-2 (J = 0 and 1) molecules adsorbed on ASW using both photo-stimulated desorption and resonance-enhanced multiphoton ionization, to investigate potential sites on ASW for diffusion, recombination dynamics, and the diffusion mechanism of H and D atoms. Our results demonstrate that the ASW surface contains various potential sites that can be categorized into at least three groups: very shallow, middle-, and deep-potential sites, with diffusion activation energies of <= 18, 22 (23 meV for D atoms), and >= 30 meV, respectively. The present study pictured the outline of H-2 formation on cosmic ice dust at low temperatures: H atoms landing on the dust will diffuse rapidly at the abundant shallow and middle sites on ASW, and finally become trapped at deep sites. The H atoms that arrive next recombine with such trapped H atoms to yield H-2 molecules. The small isotopic difference between the diffusion of H and D atoms on ASW indicates that the diffusion mechanism can be explained by thermal hopping, at least at middle-potential sites.
  • Y. Kimura, K. K. Tanaka, H. Miura, K. Tsukamoto  CRYSTAL GROWTH & DESIGN  12-  (6)  3278  -3284  2012/06  [Not refereed][Not invited]
     
    We examined the homogeneous condensation of thermally evaporated manganese vapor in an atmosphere of argon gas and determined the temperature and concentration during homogeneous nucleation in the vapor phase by using a Mach-Zehnder type interferometer. Condensation occurred at 660-785 K below the equilibrium temperature and the degree of supersaturation was as high as similar to 5 x 10(4). Using the condensation temperature and size of the condensed particles, which were measured by transmission electron microscopy, we determined the surface free energy and sticking coefficient of Mn at 1106 +/- 50 K to be 1.55 +/- 0.10 J/m(2) and 0.39(-0.20)(+0.39) respectively, by classical nucleation theory (CNT) and 1.57 +/- 0.35 J/m(2) and 0.42(-0.21)(+0.42), respectively, by a semiphenomenological theory (SP). The nucleation theories predict that the critical nucleus contains only three and six atoms for CNT and SP, respectively, which are fewer than the number of atoms in a unit cell of Mn. This suggests that the polymorphic form of manganese is decided during particle growth rather than during nucleation from the vapor phase.
  • A. Gucsik, K. Tsukamoto, H. Nishido, H. Miura, M. Kayama, K. Ninagawa, Y. Kimura  JOURNAL OF LUMINESCENCE  132-  (4)  1041  -1047  2012/04  [Not refereed][Not invited]
     
    Cathodoluminescence (CL) of laboratory forsterite chondrules has been characterized to clarify the formation process of chondrules and related mechanism of the crystal growth in a supercooled melt. Color CL image of the experimentally grown forsterite exhibits significant blue luminescence in the main branches of the interior structure of lab-chondrule, which reflects to the anisotropy of crystallization. A new CL band centered at 450-525 nm (2.76-2.36 eV) in blue to green region might be assigned to a microdefect-related center, which is a diagnostic peak for the forsterite that was formed due to the rapid growth as high as similar to 10 mm/s or higher from a supercooled melt. (C) 2011 Elsevier B.V. All rights reserved.
  • Yuki Kimura, Yuko Inatomi, Kyoko K. Tanaka, Takao Maki, Hitoshi Miura, Itsuki Sakon, Takaya Nozawa, Katsuo Tsukamoto  Journal of the Japanese Association for Crystal Growth  39-  68  -74  2012  [Not refereed][Not invited]
  • Yuki Sugiura, Kazuo Onuma, Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto  JOURNAL OF CRYSTAL GROWTH  332-  (1)  58  -67  2011/10  [Not refereed][Not invited]
     
    Nucleation of amorphous calcium phosphate (ACP) and its phase transformation with a decrease in solution pH were investigated at a constant temperature of 32 degrees C. A solution containing a mixture of CaCl2 and KH2PO4 was prepared (initial pH=7.7), and a drop was sampled at a constant interval to observe the morphological evolution of the precipitates that formed in the solution. A gel-like solution structure formed immediately after mixing and contained a small amount of sea-urchin-like ACP spherulites (3-20 mu m in size). These spherulites consisted of 1.5-10-mu m-long flexible needles that formed simultaneously with numerous ACP spherical particles. They first transformed into beta-tri calcium phosphate-like material (called "pseudo beta-TCP") and then into single crystals of octacalcium phosphate (OCP) without dissolution. The flexible needles in the spherulites changed into blade springs, then into flexible plates, and finally into rigid plates during the transformation. The OCP structure appeared in the pseudo beta-TCP plates and gradually substituted for the beta-TCP structure over time. The macroscopic spherulite morphology of the initial ACP remained unchanged during the phase transformation, suggesting that OCP is a pseudomorph of ACP. This feature was observed only when the ACP spherulites formed in the initial solution. Fiber-like aggregates consisting of beta-TCP single crystals nucleated around the ACP spherical particles and grew over time. They survived until the final stage of the reaction, and OCP polycrystals formed in the mixture of beta-TCP and ACP spheres. The OCP polycrystals gradually substituted for the ACP spheres without phase transformation of beta-TCP into OCP. (C) 2011 Elsevier B.V. All rights reserved.
  • Yuki Kimura, Hitoshi Miura, Katsuo Tsukamoto, Chaorong Li, Takao Maki  JOURNAL OF CRYSTAL GROWTH  316-  (1)  196  -200  2011/02  [Not refereed][Not invited]
     
    To investigate the homogeneous nucleation and growth process of nanoparticles in vapor phase, interferometric observation was attempted for the first time to the gas evaporation method, which has been a commonly accepted physical production method of nanoparticles. Tungsten oxide was evaporated by electrical heating of a tungsten wire in a mixture gas of Ar and O-2. WO3 nanoparticles were formed via homogeneous nucleation and growth during a gas cools following a thermal convection produced by the evaporation source. The degree of supersaturation for nucleation was extremely high, 6.6 x 10(6), which was determined from the interferogram. Surface free energy of WO3 at 1100 K was calculated based on the classical nucleation theory and was 1.38 x 10(3) erg cm(-2), which is within the reported values. A part of the difference between actual formation rate of produced nanoparticles, which were determined based on a transmission electron microscope, and calculated values based on the classical nucleation theory were well explained if we adopt the idea of coalescence growth. (C) 2011 Elsevier B.V. All rights reserved.
  • J. Nozawa, K. Tsukamoto, W. J, P. Enckevort, T. Nakamura, Y. Kimura, H. Miura, H. Satoh, K. Nagashima, M. Konoto  Journal of the American Chemical Society  133-  8782  -8785  2011  [Not refereed][Not invited]
  • Interferometric observation of temperature distributions in the smoke experiment
    Y. Kimura, K. Tsukamoto  J. Jpn. Soc. Microgravity Appl  2011  [Not refereed][Not invited]
  • Naoki Watanabe, Yuki Kimura, Akira Kouchi, Takeshi Chigai, Tetsuya Hama, Valerio Pirronello  ASTROPHYSICAL JOURNAL LETTERS  714-  (2)  L233  -L237  2010/05  [Not refereed][Not invited]
     
    Physicochemical processes (H-atom sticking, diffusion, recombination, and the nuclear spin temperature of nascent H-2 molecules) important in the formation of molecular hydrogen have been experimentally investigated on amorphous solid water (ASW). A new type of experiment is performed to shed light on a longstanding dispute. The diffusion rate of H atom is directly measured at 8 K and is found to consist of a fast and a slow component due to the presence of at least two types of potential sites with the energy depths of similar to 20 and >50 meV, respectively. The fast diffusion at the shallow sites enables efficient H-2 formation on interstellar ice dust even at 8 K, while H atoms trapped in the deeper sites hardly migrate. The spin temperature of nascent H-2 formed by recombination on ASW has been obtained for the first time and is higher than approximately 200 K. After formation, H-2 molecules are trapped and their spin temperature decreases due to the conversion of spin states on ASW.
  • Joseph A. Nuth, Yuki Kimura, Christopher Lucas, Frank Ferguson, Natasha M. Johnson  ASTROPHYSICAL JOURNAL LETTERS  710-  (1)  L98  -L101  2010/02  [Not refereed][Not invited]
     
    It has been suggested that carbonaceous grains are efficiently destroyed in the interstellar medium and must either reform in situ at very low pressures and temperatures or in an alternative environment more conducive to grain growth. Graphite whiskers have been discovered associated with high-temperature phases in meteorites such as calcium aluminum inclusions and chondrules, and it has been suggested that the expulsion of such material from protostellar nebulae could significantly affect the optical properties of the average interstellar grain population. We have experimentally studied the potential for Fischer-Tropsch and Haber-Bosch type reactions to produce organic materials in protostellar systems from the abundant H(2), CO, and N(2) reacting on the surfaces of available silicate grains. When graphite grains are repeatedly exposed to H(2), CO, and N(2) at 875 K abundant graphite whiskers are observed to form on or from the surfaces of the graphite grains. In a dense, turbulent nebula, such extended whiskers are very likely to be broken off, and fragments could be ejected either in polar jets or by photon pressure after transport to the outer reaches of the nebula.
  • Midori Saito, Itsuki Sakon, Chihiro Kaito, Yuki Kimura  EARTH PLANETS AND SPACE  62-  (1)  81  -90  2010  [Not refereed][Not invited]
     
    It has been known for sonic time that the properties of a material are changed in nanometer size. Since it is nontrivial that polycyclic aromatic hydrocarbon (PAH) grains at the nanometer scale show similar properties with that of macroscopic scale, PAH grains were synthesized by a gas evaporation method and were analyzed using a transmission electron microscope and their UV-Vis and mid-IR spectra were Measured. Results from these experiments showed that condensed anthracene grains from the gas phase had a planar form and showed similar infrared peaks compared to anthracene molecules, but With somewhat wider bands and different relative intensities. Sonic new features were also observed. The anthracene molecules formed photodimer ill their grain and showed different infrared features after UV irradiation. This Would be the first report concerning nanometer-sized PAH grains.
  • Y. Kimura, J. A. Nuth III, C. Kaito  Meteoritics & Planetary Science  46-  92  -102  2010  [Not refereed][Not invited]
  • Synthesis of stacked-cup carbon nanotubes in a metal free low temperature system
    Y. Kimura, J. A. Nuth III, N. M. Johnson, K. D. Farmer, K. P. Roberts, S. R. Hussaini  Nanoscience and Nanotechnology Letters  3-  1  -7  2010  [Not refereed][Not invited]
  • Jun Nozawa, Katsuo Tsukamoto, Hidekazu Kobatake, Junya Yamada, Hisao Satoh, Ken Nagashima, Hitoshi Miura, Yuki Kimura  ICARUS  204-  (2)  681  -686  2009/12  [Not refereed][Not invited]
     
    By means of nanoscale surface observation, we have proposed a new approach for investigating fine crystals of cosmic materials to reveal their origin and growth conditions. Several different morphologies of polyhedral fine olivines with faceted faces have been found in Allende carbonaceous chondrite (4.5 byr in geochronological age). In the present work, molecular level topography of the faceted matrix olivine by Atomic Force Microscopy (AFM) has Successfully been performed, The matrix olivine found to have preserved growth step pattern on its surface even though quite long time has passed since they formed in the early Solar System. The Surface pattern Suggests that the faceted matrix olivine could have been condensed from the gas phase, and possibly that these olivine crystals had continued to grow under a rapid cooling condition (0.1-1 K s(-1)). The estimated cooling rate agrees well with predictions based on hypothetical rapid heating and cooling events such as shock wave heating. (C) 2009 Elsevier Inc. All rights reserved.
  • Midori Saito, Yuki Kimura  ASTROPHYSICAL JOURNAL LETTERS  703-  (2)  L147  -L151  2009/10  [Not refereed][Not invited]
     
    Analogs of organic hollow globules, which have been found in carbonaceous chondrite meteorites and interplanetary dust particles, were synthesized in our laboratory from benzene and anthracene using plasma. Our results suggest that organic globules could be made from aromatic rings in circumstellar envelopes around evolved stars. The hollow interior could be formed by coagulation of vacancies, formed by electronic excitation and/or knock-out of carbon atoms following irradiation by plasma particles such as protons and He(+) ions. This experimental result suggests that organic globules are possibly the final products in the evolution of carbonaceous matter from acetylene and benzene to polycyclic aromatic hydrocarbons in ejecta gas from evolved stars.
  • 46億年昔の宇宙空間での結晶化
    木村勇気, 三浦均, 塚本勝男  日本マイクログラビティ応用学会誌  2009  [Not refereed][Not invited]
  • M. Saito, Y. Kimura  The Astrophysical Journal Letters  703-  L147-L151  2009  [Not refereed][Not invited]
  • Y. Kimura, S. Sasaki, H. Suzuki, A. Kumamoto, M. Saito, C. Kaito  ASTROPHYSICAL JOURNAL  684-  (2)  1496  -1501  2008/09  [Not refereed][Not invited]
     
    Mg-bearing silicate grains were produced directly from the vapor phase from magnesium and silicon oxide in a mixed atmosphere of Ar and O-2 in the laboratory. It was found that the crystallinity, which was deduced from the shape of the 10 mu m feature, of the grains depends on the ratio of magnesium to silicon oxide in the vapor phase. When the Mg/SiOx ratio was high, crystalline forsterite grains were produced owing to annealing of the silicate accompanied by large exothermic energy due to the oxidation of magnesium. The experimental result suggests that the crystallinity of circumstellar silicates could be determined by the balance between heat generation by magnesium oxidation and heat dissipation due to radiation. In this situation, later annealing of the silicate fraction or the use of a warm substrate for condensation of crystalline silicate is unnecessary. Crystalline silicates found in young stars are also able to be produced following our hypothesis after simultaneous evaporation of silicates and ices during energetic shocks in protostellar nebulae.
  • Chihiro Kaito, Yasuhiko Kinuta, Hitoshi Suzuki, Syunsuke Adachi, Akihito Kumamoto, Yoshio Saito, Yuki Kimura  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN  77-  (9)  094708-1-094708-4  2008/09  [Not refereed][Not invited]
     
    The apparent morphological difference between ZnO particles with and without an electric field applied during the growth process was elucidated by high-resolution transmission electron microscopy. The ZnO smoke produced immediately below the electric field by burning zinc in a gas mixture of O-2, and Ar, curved towards a negative plate. The typical tetrapod- or needle-shaped ZnO particles were seldom observed in the electric field; spherical particles were predominantly produced. Some of these spherical particles were composed of multiply twinned particles with an antiphase boundary. The growth of these multiply twinned particles was due to an increment in the ionicity in the crystallographic polar direction of ZnO bonding induced by the applied electric field.
  • Kenji Nina, Yuki Kimura, Kaorl Yokoyama, Osamu Kido, Gong Binyo, Chihiro Kaito  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES  40-  (9)  2995  -2998  2008/08  [Not refereed][Not invited]
     
    The formation process of MoO(2) crystal from amorphous MoO(3) film has been imaged by in situ observation with a transmission electron microscope. Selective growth of flower-shaped MoO(2) crystals by heating above 673 K in vacuum was directly observed. Since the MoO(2) crystal has metallic conductivity of the order of indium oxide film containing tin (ITO film), the thin film growth of the MoO(2) phase has been discussed on the basis of a new substitute for ITO film. (C) 2008 Elsevier B.V. All rights reserved.
  • Chihiro Kaito, Masayuki Shintaku, Ryuta Sakao, Akihito Kumamoto, Midori Saito, Yuki Kimura, Shinsuke Ohyagi, Shigeru Morikawa, Hiroshi Suzuki  JAPANESE JOURNAL OF APPLIED PHYSICS  47-  (8)  6588  -6591  2008/08  [Not refereed][Not invited]
     
    High-resolution transmission electron microscopy (HRTEM) of carbon particles has been carried out at 80 degrees C in saturated water vapor, to evaluate any structural alterations. Amorphous particles or microcrystallites of carbon based on the graphitic structure were altered to more stable graphitic structures such as ribbons or onion-like structures. The stable graphitic structure was altered again to the amorphous structure. Results are interpreted in terms of the oxidation of carbon particles in air. The differences in alterations among carbon particles, Pt clusters on carbon particles, and Pt clusters in carbon particles are presented on the basis of HRTEM images.
  • Frans J. M. Rietmeijer, Aurora Pun, Yuki Kimura, Joseph A. Nuth  ICARUS  195-  (1)  493  -503  2008/05  [Not refereed][Not invited]
     
    Condensates produced in a laboratory condensation experiment of a refractory Ca-SiO-H(2)-O(2) vapor define four specific and predictable deep metastable eutectic calciosilica compositions. The condensed nanograins are amorphous solids, including those with the stoichiometric CaSiO(3) pyroxene composition. In evolving dust-condensing astronomical environments they will be highly suitable precursors for thermally supported, dust-aging reactions whereby the condensates form more complex refractory silicates, e.g., diopside and wollastonite, and calcite and dolomite carbonates. This kinetically controlled condensation experiment shows how the aging of amorphous refractory. condensates could produce the same minerals that are thought to require high-temperature equilibrium condensation. We submit that evidence for this thermal annealing of dust will be the astronomical detection of silica (amorphous or crystalline) that is the common, predicted, by-product of most of these reactions. (C) 2007 Elsevier Inc. All rights reserved.
  • Y. Kimura, Y. Miyazaki, A. Kumamoto, M. Saito, C. Kaito  The Astrophysical Journal Letters  680-  89  -92  2008  [Not refereed][Not invited]
  • Behavior of cosmic dust with the material evolution in the early solar nebula
    Yuki Kimura  The Japanese Society for Planetary Sciences  17-  62  -68  2008  [Not refereed][Not invited]
  • Y. Kimura, C. Kaito  Surface and Coatings Technology  202-  4159  -4162  2008  [Not refereed][Not invited]
  • Y. Kimura, C. Kaito  The Astrophysical Journal Letters  685-  83  -86  2008  [Not refereed][Not invited]
  • Chihiro Kaito, Ryoichi Ono, Ryuta Sakao, Akihito Kuniamoto, Midori Saito, Yuki Kimura, Shinsuke Ohyagi  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS  46-  (45-49)  L1141  -L1142  2007/12  [Not refereed][Not invited]
     
    The effects of H-2 and O-2 gases on the typical fuel cell catalyst of Pt clusters on carbon particles (Pt on Q were examined using a special side-entry sample holder for high-resolution transmission electron microscopy, The holder can be used to transfer the specimen without exposure to air. The effects of H-2 and O-2 were detected after the specimen was exposed to the gases at 60 degrees C for 15 h. The predominant effect of H-2 was the coagulation of the Pt clusters. The effect of O-2 was to alter the structure of the carbon particles by oxidation.
  • Yuki Kimura, Joseph A. Nuth  ASTROPHYSICAL JOURNAL  664-  (2)  1253  -1263  2007/08  [Not refereed][Not invited]
     
    We discuss room-temperature condensation experiments using either an electrical discharge or ultraviolet radiation to initiate gas-phase reactions resulting in silicate smokes. This formation process could represent processes occurring in low-density environments, because it is possible that the gases, which can condense at higher temperatures, remain after it cools, e. g., following a shock. In these environments, many condensates could be formed simultaneously. However, in the case of our iron silicate experiments, many of the smoke particles are iron silicate with a uniform composition that reflects the composition of the ambient gas atmosphere where they were produced. In these experiments, smoke particles of other materials such as iron oxide and silica were not formed. In the case of our Si-O experiments, hydro-silicate smoke particles are produced together with anhydrous silicate particles directly from the gas phase without later hydro alteration. The infrared spectra of these silicate particles show a very strong 11.36 mu m feature attributed to H2Si2O4 and possibly to Si2O3 compared with a simultaneously observed 9.2 mu m feature due to the Si-O vibration. We believe that finding the driving force for grain growth under a wide range of environmental conditions is important if we are to understand grain formation, because silicate grains, which formed in a plasma field or under UV irradiation, show different compositions, structures, shapes, and spectra from thermally condensed grains.
  • Non-mass-dependent oxygen isotopic fractionation in smokes produced in an electrical discharge
    Yuki Kimura, Joseph A. Nuth, Subrata Chakpaborty, Mark H. Thiemens  METEORITICS & PLANETARY SCIENCE  42-  (7-8)  1429  -1439  2007/07  [Not refereed][Not invited]
     
    We report the first production of non-mass-dependently fractionated silicate smokes from the gas phase at room temperature from a stream of silane and/or pentacarbonyl iron in a molecular hydrogen (or helium) flow mixed with molecular oxygen (or nitrous oxide). The smokes were formed at the Goddard Space Flight Center (GSFC) at total pressures of just under 100 Torr in an electrical discharge powered by a Tesla coil, were collected from the surfaces of the copper electrodes after each experiment and sent to the University of California at San Diego (UCSD) for oxygen isotopic analysis. Transmission electron microscopy studies of the smokes show that they grew in the gas phase rather than on the surfaces of the electrodes. We hypothesize at least two types of fractionation processes occurred during formation of the solids: a mass-dependent process that made isotopically lighter oxides compared to our initial oxygen gas composition followed by a mass-independent process that produced oxides enriched in (17)O and (18)O. The nnaximum Delta(17)O observed is +4.7 parts per thousand for an iron oxide produced in flowing hydrogen, using O(2) as the oxidant. More typical displacements are 1-2 parts per thousand above the equilibrium fractionation line. The chemical reaction mechanisms that yield these smokes are still under investigation.
  • 原始太陽系における物質進化に関わる結晶成長
    木村勇気, 墻内千尋  2007  [Not refereed][Not invited]
  • Chihiro Kaito, Yu Miyazaki, Akihito Kumamoto, Yuki Kimura  Astrophysical Journal  666-  (1)  L57  -L60  2007  [Not refereed][Not invited]
     
    To explain how cometary silicates crystallize yet still preserve volatile interstellar ices in their parent comets, we experimentally demonstrate the possibility of chemical-reaction-driven crystallization, which is called non-thermal crystallization, using laboratory-synthesized amorphous Mg-bearing silicate grains. Analog silicate grains ∼50-100 nm in diameter covered with a carbonaceous layer consisting of amorphous carbon, CH 4, and other organics to a thickness of ∼10-30 nm were used as models. The analog silicate grains crystallized via the direct flow of surface reaction energy, which is produced by the graphitization of the carbonaceous layer due to oxidation at room temperature in air, into the silicates. The experimental results imply that amorphous silicates are transformed into crystalline silicates as the grains leave the comet's surface, rather than as the comet was accreted 4.5 billion years ago. Thus, primordial ices and amorphous silicate grains are predicted to reside in most comets until they approach the Sun.
  • T Sato, M Kurumada, K Kamitsuji, O Kido, H Suzuki, M Shintaku, Y Kimura, Y Saito, C Kaito  PLANETARY AND SPACE SCIENCE  54-  (6)  612  -616  2006/05  [Not refereed][Not invited]
     
    The production of Fe2SiO4 (fayalite) crystalline grains was performed by two processes, namely, grain formation in a plasma field by evaporating a mixture powder of Fe and SiO and heat treatment of the product collected on the radio-frequency (RF) electrode side. Fe grains < 20 nm in size covered with an amorphous SiO layer selectively formed Fe2SiO4 grains by heating at 800 degrees C. By heating at 600 degrees C, in addition to the formation of Fe2SiO4 crystal grains, the FeO phase appeared. The doping effect of excited oxygen in a plasma field into the Fe small grains may be the trigger on the formation of fayalite through the FeO phase formation. The present experimental result suggests that the probability Of Fe2SiO4 grain formation in space is low. (c) 2006 Published by Elsevier Ltd.
  • T Sato, K Kamitsuji, M Shintaku, Y Kimura, M Kurumada, O Kido, H Suzuki, Y Saito, C Kaito  PLANETARY AND SPACE SCIENCE  54-  (6)  617  -620  2006/05  [Not refereed][Not invited]
     
    Crystalline enstatite (MgSiO3) grains were produced by the simultaneous evaporation of SiO grains and Mg vapor in a plasma field. The MgSiO3 grains were spherical or needlelike. The necessity of a plasma field in astromineralogy is suggested in the present study. (c) 2006 Published by Elsevier Ltd.
  • Formation of TiC core-graphitic mantle grains from CO gas
    Yuki Kimura, Joseph A. Nuth, Frank T. Ferguson  METEORITICS & PLANETARY SCIENCE  41-  (5)  673  -680  2006/05  [Not refereed][Not invited]
     
    We demonstrate a new formation route for TiC core-graphitic mantle spherules that does not require carbon-atom addition and the very long time scales associated with such growth (Bernatowicz et al. 1996). Carbonaceous materials can be formed from C2H2 and its derivatives, as well as from CO gas. In this paper, we will demonstrate that large-cage-structure carbon particles can be produced from CO gas by the Boudouard reaction. Since the sublimation temperature for such fullerenes is low, the large cages can be deposited onto previously nucleated TiC and produce TiC core-graphitic mantle spherules. New constraints for the formation conditions and the time scale for the formation of TiC core-graphitic mantle spherules are suggested by the results of this study. In particular, TiC core-graphitic mantle grains that are found in primitive meteorites that have never experienced hydration Could be mantled by fullerenes or carbon nanotubes rather than by graphite. In situ observations of these grains in primitive anhydrous meteoritic matrix could confirm or refute this prediction and would demonstrate that the graphitic mantle on such grains is a metamorphic feature due to interaction of the presolar fullerenes with water within the meteorite matrix.
  • O Kido, M Kurumada, K Kamltsuji, T Tanigaki, T Sato, Y Kimura, H Suzuki, Y Saito, C Kaito  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES  31-  (2)  169  -173  2006/03  [Not refereed][Not invited]
     
    The synthesis of Al-Cr single quasicrystal (QC) nanoparticles of the decagonal phase was achieved by introducing an advanced gas flow evaporation method. By obtaining Successive electron diffraction patterns for single-QC nanoparticles, the phase transformation temperature of a single-QC nanoparticle was determined to be 700 degrees C. It was also determined that part of the QC nanoparticle decomposed into hex-AI(8)Cr(5) and Al during the phase transformation. Since the grain growth did not occur during the phase transformation in the present experiment, the inherent phase transformation temperature could be measured. (c) 2006 Elsevier B.V. All rights reserved.
  • C. Kaito, S. Sasaki, Y. Miyazaki, A. Kumamoto, M. Kurumada, K. Yokoyama, M. Saito, Y. Kimura, H. Suzuki  Advances in Geosciences  7-  125  -131  2006  [Not refereed][Not invited]
  • K. Yokoyama, Y. Kimura, O. Kido, M. Kurumada, A. Kumamoto, C. Kaito  Advances in Geosciences  7-  115  -123  2006  [Not refereed][Not invited]
  • A. Kumamoto, M. Kurumada, Y. Kimura, C. Kaito  Advances in Geosciences  7-  93  -99  2006  [Not refereed][Not invited]
  • Y Kimura, M Kurumada, K Tamura, C Koike, H Chihara, C Kaito  ASTRONOMY & ASTROPHYSICS  442-  (2)  507  -512  2005/11  [Not refereed][Not invited]
     
    Nanosized MgS grains, which have been considered the origin of the 30 mu m emission feature of carbon-rich evolved objects, were produced from the gas phase using an advanced gas evaporation method. The far-infrared spectrum of cubic MgS grains showed a characteristic absorption peak at 311 cm(-1) (32.1 mu m) with three shoulders at 460, 400 and 262 cm(-1) (21.7, 25.0 and 38.2 mu m). On the other hand, when the grains were roundish or network-like, the absorption peak at 250 cm(-1) became predominant. The cubic MgS grains were produced by direct nucleation from the gas phase. In the case of production via a gas-solid reaction, the MgS grains were network-like. Therefore, the formation environments of MgS grains around carbon-rich evolved objects may be predicted from the intensity of 310 and 250 cm(-1) bands. We suggest that the origins of the absorption band at 310 and 250 cm(-1) are (100), (110) and/or (111) surfaces of MgS grains, respectively.
  • Y Kimura, K Tamura, C Koike, H Chihara, C Kaito  ICARUS  177-  (1)  280  -285  2005/09  [Not refereed][Not invited]
     
    A new method of producing pyrrhotite grains, which are most commonly found in cometary material and interplanetary dust particles, was developed. Pyrrhotite grains in the monophase having a 7C structure were predominately produced using a solid-solid reaction between iron and sulfur grains at room temperature. The characteristic infrared peaks were observed at 602, 563, and 397 cm(-1) (16.6, 17.8, and 25.2 mu m). (c) 2005 Elsevier Inc. All rights reserved.
  • Y Kimura, JA Nuth  ASTROPHYSICAL JOURNAL  630-  (1)  637  -641  2005/09  [Not refereed][Not invited]
     
    We demonstrate that CaO and Ca(OH)(2) are excellent candidates to explain the 6.8 mu m feature, which is one of the most obscure features in young stellar objects. We discuss the condensation of CaO grains and the potential formation of a Ca(OH)(2) surface layer. The infrared spectra of these grains are compared with the spectra of 15 young stellar objects. We note that CaO-rich grains are seen in all meteoritic CAIs (calcium-aluminum-rich inclusions) and that the 6.8 mu m feature has only been observed in young stellar objects. Therefore, we consider CaO grains to be a plausible candidate to explain the 6.8 mu m feature and hypothesize that they are produced in the hot interiors of young stellar environments.
  • Y Kimura, C Kaito  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES  28-  (3)  281  -285  2005/08  [Not refereed][Not invited]
     
    It was shown that a carbon nanotube was selectively formed from carbon film containing Ti, supported by a standard Mo transmission electron microscopic grid, by heating at 800 degrees C in vacuum. With heating above 950 degrees C, graphite and rutile crystals of TiO2 predominately appeared. The formation of oxide is due to the supply of oxygen from the Mo grid. The formation mechanism of the carbon nanotubes was discussed on the basis of the heat of combustion due to the oxidation of titanium. The present result will lead to the development of an efficient method of production of carbon nanotubes. (c) 2005 Elsevier B.V. All rights reserved.
  • C Kaito, K Kamitsuji, S Tanaka, O Kido, M Kurumada, T Sato, Y Kimura, H Suzuki, Y Saito  THIN SOLID FILMS  483-  (1-2)  396  -399  2005/07  [Not refereed][Not invited]
     
    The dynamic behavior of a film produced by coevaporation of Ge-SiO was observed in situ using a transmission electron microscope. The film produced had an amorphous structure containing Si, Ge and SiO2. A characteristic change of the film was observed above 500 degrees C. Upon heating at 750 degrees C, in addition to the growth of the SiGe mixed crystal with the diamond structure, the liquidlike mixed phase of SiGe-SiO2 was also produced. The growth process of the liquidlike phase was directly observed in situ. The growth process of Ge and GeSi nanocrystallites has been elucidated by cooling the mixed film to room temperature. (c) 2004 Elsevier B.V All rights reserved.
  • Y Kimura, T Sato, C Kaito  CARBON  43-  (7)  1570  -1574  2005/06  [Not refereed][Not invited]
  • Y Kimura, C Kaito  THIN SOLID FILMS  476-  (1)  65  -67  2005/04  [Not refereed][Not invited]
     
    New carbide crystallites, which have a solid-solution phase with diamond structure, were formed from amorphous carbon film containing a transition metal such as Fe, Co, Mo or Ti by vacuum heating at 500-800 degrees C. The lattice constants for each solid-solution phase have been determined from electron diffraction patterns and high-resolution transmission electron microscope images. The formation of carbon polymorphs has been summarized as being dependent on the heat treatment temperature. (c) 2004 Elsevier B.V. All rights reserved.
  • Y. Kimura, M. Ishikawa, M. Kurumada, T. Tanigaki, H. Suzuki, C. Kaito  JOURNAL OF CRYSTAL GROWTH  275-  (1-2)  E977  -E981  2005/02  [Not refereed][Not invited]
     
    Si (10-50%)-containing carbon (C-Si) films were prepared by ion sputtering of carbon and silicon carbide mixture pellets. The C-Si film was composed of a solid-solution phase of carbon and silicon with a diamond structure. The film showed a higher transparency than a simultaneously evaporated C-Si mixture film. Diamond crystals 100 nm in diameter were also produced by vacuum heating of C-Si film at 800 degrees C: The infrared spectrum showed significant absorption features at 9.5 and 21 mu m; in contrast to the 11 and 12 mm of SiC. The 21 mu m feature is one of the candidate unidentified infrared bands on the spectra of carbon-rich post-asymptotic giant branch stars. (C) 2004 Elsevier B.V. All rights reserved.
  • Mami Kurumada, Osamu Kido, Takeshi Sato, Hitoshi Suzuki, Yuki Kimura, Katsuya Kamitsuji, Yoshio Saito, Chihiro Kaito  JOURNAL OF CRYSTAL GROWTH  275-  (1-2)  E1673  -E1678  2005/02  [Not refereed][Not invited]
     
    WO3 nanoparticles from 10 to 250nm in diameter were formed by burning tungsten wire in low-oxygen-partial-pressure atmosphere in Ar gas. The structure of the 10-nm-order particle was cubic WO3, and for the particle larger than 50 nm, the structure was triclinic WO3. The color of the produced samples changed from blue to yellowish green and yellow depending on the particle size. It was also shown that the present particle is a good transmittance material for mid-IR light with wavelength between 5 and 20 mu m. The growth of huge particles by coalescence growth in smoke has been discussed. (C) 2004 Elsevier B.V. All rights reserved.
  • Takeshi Sato, Hitoshi Suzuki, Osamu Kido, Mami Kurumada, Katsuya Kamitsuji, Yuki Kimura, Hiromichi Kawasaki, Satoo Kaneko, Yoshio Saito, Chihiro Kaito  JOURNAL OF CRYSTAL GROWTH  275-  (1-2)  E983  -E987  2005/02  [Not refereed][Not invited]
     
    Transition metals, such as tungsten (W), molybdenum (Mo) and chromium (Cr), were doped into ZnO nanoparticles using an RF plasma system. The resulting ZnO nanoparticles with the size of 30-50 nm changed from white to yellowish or to orange depending on the doped transition metals. The doping position of these transition metals in the ZnO crystal was the same as that determined in a previous paper (J. Crystal Growth 265 (2004) 149). It was found that light with wavelength shorter than 385 nm can be removed by doping. The morphological change due to doping of elements was discussed in terms of the difference of ionicity. (C) 2004 Elsevier B. V. All rights reserved.
  • Osamu Kido, Katsuya Kamitsuji, Mami Kurumada, Takeshi Sato, Yuki Kimura, Hitoshi Suzuki, Yoshio Saito, Chihiro Kaito  JOURNAL OF CRYSTAL GROWTH  275-  (1-2)  E1745  -E1750  2005/02  [Not refereed][Not invited]
     
    The morphological alteration from delta- to alpha-Cr nanoparticles and the phase transition temperature were directly observed by in situ experiment using a transmission electron microscope. The icositetrahedral nanoparticle of delta-Cr transformed into a rhombic dodecahedral nanoparticle of alpha-Cr upon heating at 550 degrees C: It was demonstrated that the most stable shape of the alpha-Cr nanoparticle is the rhombic dodecahedron. Upon heating the alpha-Cr nanoparticle at 650 degrees C; the (1 1 3) layer of Cr2O3 grew topotactically in the direction of [100] of alpha-Cr nanoparticle. We concluded that the alpha-Cr nanoparticle includes about 20-30 at% oxygen, as estimated from the volume of the Cr2O3 surface layer. (C) 2004 Elsevier B.V. All rights reserved.
  • K Kamitsuji, H Suzuki, Y Kimura, T Sato, Y Saito, C Kaito  ASTRONOMY & ASTROPHYSICS  429-  (1)  205  -208  2005/01  [Not refereed][Not invited]
     
    A novel method for producing MgO and SiO2 smokes was developed. Mg-bearing silicate grain formation using the coalescence and growth of MgO and SiO2 grains was carried out in our laboratory. It becomes evident that single and poly crystalline Mg2SiO4 (forsterite) and amorphous Mg-bearing silicate grains can be produced by the coalescence and growth of MgO and SiO2 grains. This result suggests that the observed crystalline Mg2SiO4 grains and amorphous Mg-bearing silicate particles in Red Super Giant (RSG), Asymptotic Giant Branch (AGB), post-AGB and planetary nebula (PNe) could be produced by the coalescence and growth of MgO and SiO2 grains.
  • O Kido, H Suzuki, Y Kimura, T Sato, Y Saito, C Kaito  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES  25-  (4)  619  -624  2005/01  [Not refereed][Not invited]
     
    Al-Mn quasicrystal ultrafine particles can be produced by the advanced gas evaporation method (AGEM), which is a method of preparing ultrafine alloy particles by coalescence growth among the particles near the evaporation sources. We investigated the phase transition temperature from a quasicrystal to a stable crystal, by examining successive electron diffraction patterns of an ultrafine particle in an in situ experiment using a transmission electron microscope. In spite of the report that the Al86Mn14 quasicrystal transforms into the crystal phase at around 400-670 degreesC on thin film specimens, the quasicrystal ultrafine particle transformed at 800 degreesC, i.e., the quasicrystal ultrafine particle is more stable. Since the cross-sectional view of the surface oxide layer of the quasicrystal ultrafine particles can be easily observed, the surface oxides of eta-Al2O3 and MnO were characterized as a result of the oxidation of residual atoms on the surface of the produced alloy particles including the quasicrystals. The conditions required for Al-Mn quasicrystal ultrafine particle formation by the AGEM can be estimated under the cooling rate of 105 K/s. (C) 2004 Elsevier B.V. All rights reserved.
  • A. Kouchi, H. Nakano, Y. Kimura, C. Kaito  The Astrophysical Journal Letters  626-  L129-L132  2005  [Not refereed][Not invited]
  • S Sasaki, H Suzuki, Y Kimura, T Sato, T Tanigaki, O Kido, K Kamitsuji, M Kurumada, C Kaito  EARTH PLANETS AND SPACE  57-  (5)  399  -401  2005  [Not refereed][Not invited]
     
    The formation of Al(2)O(3) phases by the solid-solid reaction of a metallic Al layer evaporated on a SiO(2) amorphous grain has been induced by heating above 600 degrees C in vacuum (1 x 10(-6) Pa). The distortion process of the amorphous SiO(2) grains by the formation of Al(2)O(3) have been directly imaged by in-situ TEM observation. A partly deposited Al layer covered the SiO(2) grains after heating at 750 degrees C, and gamma-Al(2)O(3) grains of about 25 nm diameters were formed on the SiO(2) surface. Upon the growth of Al(2)O(3), the SiO(2) grain decomposed into a mixture of metallic Si and SiO(2) and disappeared as a result of sublimation due to the formation of SiO(x) at high temperatures. The present result on dust surface dynamics will become an important field with respect to the metamorphism of grains from the astromineralogical viewpoint.
  • Y. Kimura, Joseph A. Nuth III, Frank T. Ferguson  The Astrophysical Journal Letters  632-  L159-L162  2005  [Not refereed][Not invited]
  • K Kamitsuji, S Ueno, H Suzuki, Y Kimura, T Sato, T Tanigaki, O Kido, M Kurumada, C Kaito  ASTRONOMY & ASTROPHYSICS  422-  (3)  975  -979  2004/08  [Not refereed][Not invited]
     
    Experimental studies on the metamorphism of SiO(x) grains under heating at 10(-6) Pa have been conducted using a high-resolution transmission electron microscope. Si crystallites were predominantly grown at 500 to 700 degreesC in SiO(x) grains. The Si crystallites disappeared at 800 degreesC and evaporated as the SiO phase.
  • O Kido, Y Higashino, K Kamitsuji, M Kurumada, T Sato, Y Kimura, H Suzuki, Y Saito, C Kaito  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN  73-  (7)  2014  -2016  2004/07  [Not refereed][Not invited]
     
    The iron oxide ultrafine particles prepared by the gas evaporation method, in which commercial alpha-Fe2O3 powder is evaporated, are composed of alpha-Fe2O3 particles covered with a gamma-Fe2O3 mantle layer. To study the phase transition temperature of the gamma-Fe2O3 mantle layer, the particles were heated and observed in a transmission electron microscope. The present specimen of gamma-Fe2O3 transformed completely to alpha-Fe2O3 at above 700degreesC, and this phase transition was irreversible. The phase transition temperature was 1.4 times higher than the bulk value. The growth mechanism of the present specimen of alpha-Fe2O3 particles covered with the gamma-Fe2O3 mantle layer has been discussed in terms of the difference in the cooling rates between the inside and the surface of the particle at around the evaporation source.
  • Y Kimura, A Ikegami, M Kurumada, K Kamitsuji, C Kaito  ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES  152-  (2)  297  -301  2004/06  [Not refereed][Not invited]
     
    crystallites less than 10 nm in size showed an absorption feature at 14.3 mum. This 14.3 mum absorption was rarely seen in specimens ranging from bulk material to grains of 50 nm in size. The 14.3 mum feature was weakened as a result of the growth of TiC crystallites by heat treatment. When the carbide grains were covered with a carbon layer, the absorption peaks were considerably weakened, i.e., the absorption intensity depended on the grain surface state. A possible explanation is that the effects of size and shape on the spectra depend on the surface anisotropy.
  • M Kurumada, Y Kimura, H Suzuki, O Kido, Y Saito, C Kaito  SCRIPTA MATERIALIA  50-  (11)  1413  -1416  2004/06  [Not refereed][Not invited]
     
    The structure of NiTi shape memory alloy nanoparticles was determined by high-resolution electron microscopy. The mixture of Ni4Ti3 and R-phases was observed, which clearly showed lattice relationships of (2 (1) over bar 1)(B2)//(1 0 1)Ni4Ti3 and (2 (2) over bar 0)(B2)//(1 3 1)Ni4Ni3. Lattice images of an R-phase particle suggested the existence of a Ni-rich Guinier-Preston zone (G.P. zone). (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
  • S Tanaka, O Kida, M Kurumada, K Kamitsuji, Y Kimura, H Suzuki, Y Saito, C Kaito  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES  23-  (1-2)  108  -113  2004/06  [Not refereed][Not invited]
     
    Complete mixture films of carbon and germanium produced by the co-evaporation in vacuum were directly heated in a transmission electron microscope. It was noticed that the diffusion and growth of Ge dots in the mixture film take place at approximately 500degreesC. On the other hand, Ge dots coated with amorphous carbon were produced by simultaneous evaporation of carbon and Ge in Ar gas at 10 kPa. In addition to Ge clusters of 3-10 nm in size, multiple-twin Ge clusters with the size of 10 nm have been produced in carbon soot. These Ge clusters showed a diamond structure. The growth process of Ge clusters in amorphous carbon soot has been discussed using the result in the mixture film experiment and temperature distribution in the particle formation process. (C) 2004 Elsevier B.V. All rights reserved.
  • T Tanigaki, Y Kimura, H Suzuki, M Kurumada, C Kaito  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN  73-  (5)  1375  -1376  2004/05  [Not refereed][Not invited]
  • T Sato, H Suzuki, O Kido, M Kurumada, K Kamitsuji, Y Kimura, A Takeda, S Kaneko, Y Saito, C Kaito  JOURNAL OF CRYSTAL GROWTH  265-  (1-2)  149  -153  2004/04  [Not refereed][Not invited]
     
    A tungsten plate was set on a one-plate electrode in RF plasma using parallel plates in a mixed gas of argon (9.75 Torr) and oxygen (0.25 Torr). Zn smoke was introduced into the plasma field. W atoms were doped in the ZnO smoke formation field in the RF plasma system. The resulting particles with a size of 30 run were identified to be hexagonal ZnO particles. The collected particles changed from white to yellow, i.e., W atoms were doped into ZnO particles. The image of the (0 0 0 1) lattice, which is the forbidden reflection, appeared predominantly in the W-doped ZnO particle. Furthermore, by optical measurement. it Was found that the existence of W atoms can control the recombination radiation due to the exciton. On the basis of high-resolution transmission electron microscopic images, the doped W positions are discussed as being in the commensurate Configuration of W items in the ZnO crystal at positions equivalent to those in the cubic anti-fluoride structure. (C) 2004 Elsevier B.V. All rights reserved.
  • Y Kimura, T Sato, C Kaito  CARBON  42-  (1)  33  -38  2004  [Not refereed][Not invited]
     
    In the present study, by a simple method, carbon soot with a narrow absorption features at around 220 nm was produced by pyrolysis of methane gas at a hot (1400-2800degreesC) filament. A detailed correlation between the structure and the optical spectra of carbon soot was carried out using a high-resolution transmission electron microscope. It appears that the origin of the narrow absorption peak is an onion-like graphitic structure. Interestingly, we found that the absorption peak position and the size of the soot can be controlled by the production temperature. The absorption peak is located at 217.5 nm, i.e., at the position of an intense interstellar absorption, when the onion structure has about 5 nm diameter. Infrared spectroscopy was applied to further elucidate the chemical composition of the obtained soot. (C) 2003 Elsevier Ltd. All rights reserved.
  • Y. Kimura, O. Kido, M. Oomoto, K. Ogawa, H. Namba, C. Kaito  Japanese Journal of Applied Physics  43-  (7)  L888-L890  2004  [Not refereed][Not invited]
  • T Tanigaki, Y Kimura, H Suzuki, C Kaito  JOURNAL OF CRYSTAL GROWTH  260-  (3-4)  298  -303  2004/01  [Not refereed][Not invited]
     
    A particle with a CdTe core and carbon mantle was produced by the advanced carbon-coating method which enables direct coverage with a carbon layer using an electron microscope. The coagulated particles containing approximately 30-200 CdTe particles produced by the gas evaporation method were covered with a carbon layer of about 7 nm thickness at 300 degreesC. By heating these particles above 500 degreesC, the sublimation process of a part of the CdTe particle can be directly captured by high-resolution transmission electron microscopy and recorded in real time on videotape. Sublimation on the CdTe(111) surfaces occurred in the step flow mode of two (111) layers. It was observed that two (111) zinc-blende layers changed to the (0002) wurtzite configuration unit just before sublimation. The condensation of CdTe on the sublimated particle surface and growth of CdTe in the carbon layers were also captured in the video image. These sublimation processes were discussed in terms of the existence of the polarity of II-VI compounds. (C) 2003 Elsevier B.V. All rights reserved.
  • Y Ishikawa, O Kido, Y Kimura, M Kurumada, H Suzuki, Y Saito, C Kaito  SURFACE SCIENCE  548-  (1-3)  276  -280  2004/01  [Not refereed][Not invited]
     
    Transmission electron microscopy was used to study spontaneous copper selenide formation on Cu particles covered with an oxide layer. Even if the copper particle surface was covered with a Cu2O layer, selenides were formed by diffusion through the metal oxide layer. For a particle size less than 50 nm, selenide was formed in Cu particles by the diffusion of Se atoms passing through the Cu2O layer. For particles larger than 100 nm in size, selenide was formed in Se film. It was also found that the thickness of the Cu2O layer on the surface of Cu particle accelerated diffusion of Se atoms to the copper particle. (C) 2003 Elsevier B.V. All rights reserved.
  • T Sato, O Kido, M Kurumada, Y Kimura, H Suzuki, Y Saito, C Kaito  CARBON  42-  (8-9)  1875  -1877  2004  [Not refereed][Not invited]
  • K Tamura, Y Kimura, H Suzuki, O Kido, T Sato, T Tanigaki, M Kurumada, Y Saito, C Kaito  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS  42-  (12)  7489  -7492  2003/12  [Not refereed][Not invited]
     
    Ultrafine particles of various metals [Cr, Mn, Fe, Al, Ni, Cu, In, Si, Ge, Zn, Mg and Sn], produced by the gas evaporation method were covered with the oxide layer of thickness less than 10 nm by exposure to air. In order to clarify the structure and thickness of the surface oxide layer, on various metal ultrafine particles, high-resolution electron microscopy and infrared spectroscopy have been extensively used.
  • T Tanigaki, H Suzuki, Y Kimura, O Kido, Y Saito, C Kaito  JOURNAL OF CRYSTAL GROWTH  256-  (3-4)  317  -323  2003/09  [Not refereed][Not invited]
     
    In order to elucidate the stability of a silicon oxide layer on zoo, the dynamic behavior of SiO- and SiO2-layer-coated ZnO ultrafine particle surfaces were directly observed by heating in a transmission electron microscope up to 700degreesC. In the case of SiO-coated ZnO ultrafine particles, ZnO nanocrystallites with the size of 2 nm grew in the SiO layer at 500degreesC. In the case of SiO-coated ZnO ultrafine particles, beta-cristobalite with the size of 10nm order was grown at 600degreesC. Zn2SiO4 particles were grown by coalescence between beta-cristobalite and ZnO at 700degreesC. By comparing the SiO and SiO, layers on ZnO ultrafine particles, it was found that the behaviors of the two silicon oxide layers are clearly different. (C) 2003 Elsevier B.V. All rights reserved.
  • T Sato, A Takeda, Y Kimura, H Suzuki, Y Saito, C Kaito  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS  42-  (9A)  5896  -5897  2003/09  [Not refereed][Not invited]
     
    Amorphous silicon oxide particles with the size of 30-100 nm were produced by spraying Si(C2H5O)(4) liquid into a plasma region. Plasma was generated at a high pressure of 10 Torr in a mixture gas of argon and oxygen. The production of two silicon oxide particles with the structure of SiO and SiO2 could be controlled by the oxygen partial pressure in plasma.
  • Y Kimura, C Kaito  MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY  343-  (2)  385  -389  2003/08  [Not refereed][Not invited]
     
    Focusing on the growth of metal carbide particles and the formation of pre-solar grains, a new attempt has been made for titanium carbide (TiC) systems. Using the noble gas evaporation method, we succeeded in producing TiC core (50-nm) carbon mantle (2-nm) grains of the same core size as pre-solar grains. The infrared spectrum has broad absorption features at 9.5 and 12.5 mum. It was also found that these absorption peaks became weaker by an increase to 15 nm of carbon mantle layer. The determination method of the contact angle of carbon on the TiC grain has been developed using a high-resolution electron microscopic technique. The contact angles between TiC and carbon were and on the (111) and (100) TiC grain surfaces, respectively.
  • Y Kimura, H Ueno, H Suzuki, T Tanigaki, T Sato, Y Saito, C Kaito  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES  19-  (3)  298  -302  2003/08  [Not refereed][Not invited]
     
    The high-temperature behavior of Au clusters on a Si nanoparticle surface has been studied using the atomic-resolution high-temperature stage of a transmission electron microscope. Au atoms diffuse into the Si nanoparticle at 680degreesC and return to the surface at room temperature. The movement of diffused Au atoms on the Si surface steps and the movement of Guinier-Presion-zone-like contrast observed for the segregation of An atoms on the (lll) Si plane, have been directly observed. These phenomena, which can be detected only at high temperatures, are presented in this paper. (C) 2003 Elsevier B.V. All rights reserved.
  • A Ikegami, Y Kimura, H Suzuki, T Sato, T Tanigaki, O Kido, M Kurumada, Y Saito, C Kaito  SURFACE SCIENCE  540-  (2-3)  395  -400  2003/08  [Not refereed][Not invited]
     
    Titanium carbide formation by the solid-solid reaction on the surface of Ti nanoparticles was studied in situ using a high-resolution transmission electron microscope with a heating stage. The cross-sectional image of the Ti surface was clearly observed. Vacuum-deposited carbon covered the whole the surface of Ti nanoparticles in spite of the partly evaporation on the nanoparticle surface. The diffusion of the carbon atoms inside the Ti nanoparticles depended on the size of the nanoparticles. When the Ti nanoparticle diameter was less than 30 nm, carbon atoms diffused into the Ti nanoparticle and formed TiC. The superstructure of the Ti nanoparticles was observed, which revealed the growth process of TiC to be the diffusion of carbon atoms. For Ti nanoparticles with diameter larger than 30 run it was observed that diffusion of Ti atoms into the carbon layer was dominant, which resulted in formation of TiC in the carbon layer at the surface of Ti nanoparticles. (C) 2003 Elsevier B.V. All rights reserved.
  • T Sato, T Tanigaki, H Suzuki, Y Saito, O Kido, Y Kimura, C Kaito, A Takeda, S Kaneko  JOURNAL OF CRYSTAL GROWTH  255-  (3-4)  313  -316  2003/08  [Not refereed][Not invited]
     
    ZnO particles were produced by dropping Zn powder into a heated boat just below the plasma electrodes in a mixture gas of argon and oxygen. The resulting particles look spherical with the size of 30 nm and were of tetrapod configuration having four [0 0 0 1] axes of ZnO. The dispersion became better than that in the case of another method without plasma. The ultraviolet-visible light transmittance of the specimen showed sharp absorption. The electric charge in the plasma field controlled the coalescence growth of each particle and improved the dispersion of the particles due to the plasma effect. (C) 2003 Elsevier Science B.V. All rights reserved.
  • M Ishikawa, Y Kimura, H Suzuki, O Kida, T Tanigaki, T Sato, Y Saito, C Kaito  JOURNAL OF CRYSTAL GROWTH  254-  (1-2)  131  -136  2003/06  [Not refereed][Not invited]
     
    The silicon core and carbon mantle particles were produced by using the advanced carbon coating method which enables direct covering with the carbon layer using an electron microscope. The growth of SiC crystal was observed upon heating at 500degreesC in vacuum. The growth process of SiC on both the carbon layer and silicon particles was directly observed by in situ observation. The inward movement of carbon into silicon began at the twinned part. The growth rate of SiC on the carbon mantle layer was estimated from in situ images and found to be 8 times faster than the growth rate of silicon carbide in silicon particles. (C) 2003 Elsevier Science B.V. All rights reserved.
  • Dynamic behavior of a silicon oxide layer on silicon ultrafine particles
    Y Kimura, H Ueno, H Suzuki, T Sato, T Tanigaki, O Kido, C Kaito, Y Saito  SURFACE REVIEW AND LETTERS  10-  (2-3)  361  -364  2003/04  [Not refereed][Not invited]
     
    In order to clarify the high-temperature behavior of a silicon oxide layer on the surface of Si ultrafine particles, the oxide layer has been studied using the atomic-resolution high-temperature stage of a transmission electron microscope. The natural oxide layer grown on Si ultrafine particles by exposure to air was an amorphous silicon oxide layer with a thickness of 1.5 nm. This oxide layer started to dissolve into the Si crystal upon heating at 500degreesC, and was fully dissolved into the Si crystal at 600degreesC in vacuum. When the specimen was cooled back to room temperature, the silicon oxide layer reappeared on the Si surface. This phenomenon, which can be detected only at high temperatures, is presented in this paper.
  • Atomic observation of the sublimation process of the Pb (111) surface
    T Tanigaki, H Suzuki, Y Kimura, C Kaito, Y Saito  SURFACE REVIEW AND LETTERS  10-  (2-3)  455  -459  2003/04  [Not refereed][Not invited]
     
    The dynamic behavior of the sublimation process using ultrafine Pb particles produced by the gas evaporation technique was examined at the level of atomic resolution using a transmission electron microscope equipped with a real-time video-recording system. The ultrafine Pb particles coated with a carbon layer with a thickness of the order of 5 nm were prepared in the electron microscope by heating particles on carbon film at 300degreesC. Sublimation of the Pb particle covered with the carbon layer took place above 470degreesC, which is slightly higher than the melting point of Pb. Sublimation occurred at the surface with a higher surface energy. The sublimation process of the (111) surface was clearly observed at an atomic level. It was found that two- or four-atomic-layer step flow was observed at the (111) surface. At the (111) surface between the stacking faults, two-layer and successive one-layer sublimation occurred.
  • M Kurumada, H Suzuki, Y Kimura, Y Saito, C Kaito  JOURNAL OF CRYSTAL GROWTH  250-  (3-4)  444  -449  2003/04  [Not refereed][Not invited]
     
    Dynamics of crystallization of amorphous antimony-selenium film deposited on carbon substrate have been studied by the high-resolution transmission electron microscopy. The amorphous film was suddenly crystallized at 200degreesC by heating in vacuum. By the electron beam irradiation crystallization occurred at the focused electron beam region in the amorphous film. The growth process of crystallization by electron beam irradiation was recorded on a video image at the atomic resolution mode. The growth front of crystallization showed nano-concave and -convex shapes. The recrystallization with the different orientation at the first grown crystal have been found, and discussed as the influence of remaining antimony crystallites at the first crystallized film region. (C) 2003 Elsevier Science B.V. All rights reserved.
  • Yuki Kimura, Yoshio Saito, Chihiro Kaito  Surface Science  527-  (1-3)  L219  -L221  2003/03/10  [Not refereed][Not invited]
     
    The dynamic behavior of an amorphous carbon layer of 3 nm thickness on a SiC particle was examined at high temperature using a high-resolution electron microscope equipped with a real-times video recording system. It was found that the surface carbon layer began to solve into the SiC particle at 600 °C. The layer was completely solved into SiC crystal at 800 °C. The lattice image of SiC changed negligibly at high temperature. If the specimen was cooled back to room temperature, the carbon layer on the SiC particle was recovered. © 2002 Elsevier Science B.V. All rights reserved.
  • Y Atou, H Suzuki, Y Kimura, T Sato, T Tanigaki, Y Saito, C Kaito  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES  16-  (2)  179  -189  2003/02  [Not refereed][Not invited]
     
    Two methods for the preparation of TiO2 particles using the gas evaporation methods have been proposed. A method for selective growth of the anatase and/or rutile particles as well as a method of covering TiO2 particles with an SiO2 layer has been developed. The process of dissolving the SiO2 layer into TiO2 particles has been observed by an in situ observation using high-resolution electron microscopy. SiO2 layers of 5 nm order were dissolved completely into TiO2 particles of the order of 30 nm at 750degreesC. These SiO2 layers appeared again at room temperature on the surfaces of TiO2 particles. This phenomenon was observed only at a high temperature. By the use of the phenomenon of dissolving the SiO2 layer into TiO2 particles at high temperature, the growth of TiO2 particles covered with the SiO2 layer has been discussed. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Y. Kimura, C. Kaito  Journal of Crystal Growth  250-  (3-4)  450  -457  2003  [Not refereed][Not invited]
  • Y. Kimura, C. Kaito  Journal of Crystal Growth  255-  (3-4)  282  -285  2003  [Not refereed][Not invited]
  • Y. Kimura, C. Kaito  Astronomy and Astrophysics  409-  159  -161  2003  [Not refereed][Not invited]
  • Characteristic behavior of Bi clusters and growth process to the continuous film
    C. Kaito, Y. Kimura, S. Tominaga, S. Kimura, T. Nakada, Y. Saito  Physics of Low-Dimensional Structures  5/6-  1  -8  2003  [Not refereed][Not invited]
  • T. Chigai, T. Yamamoto, C. Kaito, Y. Kimura  The Astrophysical Journal  587-  (2)  771  -776  2003  [Not refereed][Not invited]
  • Demonstration of crystalline forsterite grain formation due to coalescence growth of Mg and SiO smoke particles
    C Kaito, Y Ojima, K Kamitsuri, O Kido, Y Kimura, H Suzuki, T Sato, T Nakada, Y Saito, C Koike  METEORITICS & PLANETARY SCIENCE  38-  (1)  49  -57  2003/01  [Not refereed][Not invited]
     
    Experimental studies of coalescence between Mg grains and SiO grains in smoke reveal the direct production of crystalline forsterite grains. The present results also show that different materials can be produced by grain-grain collisions, which have been considered one of the models of grain formation in the interstellar medium. The fundamentals of coalescence growth in smoke, which have been developed in our series of experiments, are presented in this paper. Mg2Si polyhedral grains were obtained in a Mg grain-rich atmosphere. Mg2SiO4 polyhedral grains were obtained in a SiO grain-rich atmosphere. The IR spectra of the resultant grains showed the characteristics of crystalline forsterite.
  • H Nakano, A Kouchi, M Arakawa, Y Kimura, C Kaito, H Ohno, T Hondoh  PROCEEDINGS OF THE JAPAN ACADEMY SERIES B-PHYSICAL AND BIOLOGICAL SCIENCES  78-  (9)  277  -281  2002/11  [Not refereed][Not invited]
     
    Based on experiments that model interstellar organic materials, we found that both C and N contents and IR spectra of insoluble organic materials in carbonaceous chondrites could be reproduced well by the aqueous alteration and the subsequent thermal metamorphism. The resulting sample shows strong evidence of diamond, which indicates that this process is an unexpected mechanism that might produce extensive amount of diamond in meteorites' parent bodies. Because this process requires neither high pressures nor energetic processes, the present results suggest an alternate origin of diamonds in meteorites.
  • H Suzuki, N Fukuzawa, T Tanigaki, T Sato, O Kido, Y Kimura, C Kaito  JOURNAL OF CRYSTAL GROWTH  244-  (2)  168  -172  2002/10  [Not refereed][Not invited]
     
    The reduction process of tenorite whiskers grown on a copper mesh by heating in vacuum has been directly observed using a transmission electron microscope equipped with a real-time video-recording system. The coating of the carbon layer and reduction of the tenorite whisker covered with a carbon layer have also been captured in real time on video images. The growth process of an amorphous carbon tube has been elucidated. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Y Kimura, K Hanamoto, Y Nakayama, C Kaito  NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS  194-  (2)  187  -192  2002/08  [Not refereed][Not invited]
     
    In order to elucidate the effect of synchrotron radiation (SR) irradiation on crystal growth, crystallization of WO3 films has been performed in vacuum under SR irradiation. The main results were compared with the results of heat treatment of the same film. Upon SR irradiation for 80 s using a toroidal mirror, a catastrophic change occurred, i.e. W3O crystals (A-15 type) with a size of less than 30 nm appeared. Decomposition of the WO3 film started at above 750 degreesC during vacuum heating. W, WO2 and incommensurate WO3 crystals appeared. W3O crystal produced neither intense electron beam irradiation nor vacuum heating. These results will be discussed in terms of the differences caused by excitation with a SR beam, i.e. strong inner shell excitation and ionization of W and O may have taken place. (C) 2002 Elsevier Science B.V. All rights reserved.
  • T Kobayashi, Y Kimura, H Suzuki, T Sato, T Tanigaki, Y Saito, C Kaito  JOURNAL OF CRYSTAL GROWTH  243-  (1)  143  -150  2002/08  [Not refereed][Not invited]
     
    Amorphous tin oxide films deposited on carbon substrates have been studied by high-resolution transmission electron microscopy. As-deposited film was composed of a mixture of microcrystallites of SnO, SnO2 and SnO3 with size of 2 nm. Crystallization took place above 450degreesC. SnO crystals appeared between 450degreesC and 500degreesC, whereas SnO2 crystals appeared above 550degreesC. The appearance of beta-tin crystals with the reduction of tin oxide has been verified using the heating stage of the electron microscope. A drop of liquid tin was recognized upon heating above 500degreesC. The difference in crystallization upon applying an electron beam, synchrotron radiation and heating in vacuum has been summarized and discussed with respect to the problem of the excitation of crystallites. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Yuki Kimura, Chihiro Kaito, Katsumi Hanamoto, Muneo Sasaki, Seiji Kimura, Toshitaka Nakada, Yoshio Saito, Yasuyuki Nakayama  Carbon  40-  (7)  1043  -1050  2002/06  [Not refereed][Not invited]
     
    Growth of small carbyne crystals in a thin amorphous carbon film has been observed by high-resolution transmission electron microscopy (HRTEM). The as-deposited film was composed of diamond and graphite crystallites of size 1 nm. Circular α-phase carbyne crystals predominantly grew to 20 nm in size and transformed into (α+β)-phase crystals with an elongated shape of 100 nm in length. The typical correlation during the transformation is (220α//(301)α+β. The c-axes of both grown crystals were oblique to the direction of the electron beam. The growth process of carbyne crystals will be discussed in terms of selective excitation of graphite crystallites by an SR beam. © 2002 Elsevier Science Ltd. All rights reserved.
  • M Sasaki, K Hanamoto, Y Kimura, C Kaito, H Miki, Y Nakayama  REVIEW OF SCIENTIFIC INSTRUMENTS  73-  (3)  1384  -1386  2002/03  [Not refereed][Not invited]
     
    The effects of synchrotron radiation (SR) irradiation on the electrical properties of tin-doped In2O3 (ITO) thin films prepared by rf magnetron sputtering have been studied. A white SR beam focused by a cylindrical mirror was used to irradiate ITO thin films at doses of 0.35, 1.98, 3.50, and 6.64 mA h. We have achieved resistivity of 2x10(-4) Omega cm on ITO thin film at an irradiation dose of 3.5 mA h without extra heating. The mobility of the ITO films did not decrease after SR irradiation. The electrical properties in connection with the structural change due to SR are discussed. (C) 2002 American Institute of Physics.
  • Y Kimura, Y Saito, T Nakada, C Kaito  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES  13-  (1)  11  -23  2002/01  [Not refereed][Not invited]
     
    Experimental studies on the mixing of alkali halide clusters of 200 nm sizes were performed systematically by the successive evaporation of different alkali halides on carbon substrates. The alkali halides used were NaCl, NaBr, KCl, KBr, KI, RbCl, RbBr, CsCl and CsBr. Intermixing took place independent of the crystal structure. It became evident that the limit of mixing was governed by the ratio of ionic radii. If the ratio of ionic radii between the cation and/or anion was more than 68%, intermixing occurred. It was also found that the crystal structure formed by intermixing between NaCl-type and CsCl-type structures becomes the NaCl type. If four different elements of cations and anions are involved, two mixture phases grew. The key elements of mixing were the nearest ionic radii. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Crystallization and selective growth of amorphous Y-Ba-Cu-O film
    T. Tanigaki, S. Ariumi, H. Suzuki, Y. Kimura, S. Kimura, T. Sato, N. Tsuda, T. Nakada, Y. Saito, C. Kaito  Physics of Low-Dimensional Structures  11/12-  77  -84  2002  [Not refereed][Not invited]
  • Ordered alloy formation by the use of reaction between ultrafine particle and cluster
    T Tsurusako, T Tanigaki, H Suzuki, Y Kimura, T Sato, O Kido, Y Saito, C Kaito  PHYSICS OF LOW-DIMENSIONAL STRUCTURES  7-8-  77  -86  2002  [Not refereed][Not invited]
     
    To observe the singularity of clusters and ultrafine particles in low dimensions, a new experiment has been started on the Au-Cu system. The diffusion of atoms in the cluster and ultrafine particles has been observed including the direct observation at the interface. The alloy formation temperature decreases by about 50degreesC compared with the film-ultrafine particle. The diffusion rate difference observed in bulk phase is preserved in the alloy formation process.
  • A new attempt on reduction of ultrafine oxide particles
    H. Suzuki, T. Tanigaki, T. Sato, O. Kido, Y. Atou, Y. Kimura, C. Kaito  Physics of Low-Dimensional Structures  7/8-  99  -106  2002  [Not refereed][Not invited]
  • 佐々木宗生, 花元克巳, 木村勇気, かい内千尋, 中山康之  滋賀県工業技術総合センター研究報告  (15)  46  -49  2001/08  [Not refereed][Not invited]
  • Y Kimura, T Kobayashi, K Hanamoto, M Sasaki, S Kimura, T Nakada, Y Nakayama, C Kaito  NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT  467-  1221  -1224  2001/07  [Not refereed][Not invited]
     
    In order to see the effect of SR irradiation on crystal growth., crystallization of tin oxide films has been performed in vacuum under SR irradiation, A thin amorphous tin oxide film 50 nm thick was prepared on the carbon substrate by vacuum evaporation of SnO2 power, A SnO crystal appeared between 450-500 degreesC upon vacuum heating, with a preferred orientation of (0 0 1). By SR irradiation using a cylindrical mirror for 20 s, the SnO crystal appeared with the preferred orientation of (1 1 1). The crystal with the crystallographic shear structure was grown by SR irradiation. This growth under a SR beam is discussed in terms of SR beam excitation of lone-pair electrons seen in the SnO crystal structure. (C). 2001 Elsevier Science B.V. All rights reserved.
  • C Kaito, Y Kimura, K Hanamoto, M Sasaki, S Kimura, T Nakada, Y Saito, C Koike, Y Nakayama  NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT  467-  1217  -1220  2001/07  [Not refereed][Not invited]
     
    Thin carbon films prepared by vacuum evaporation using the arc method were mounted on a standard electron microscope copper grid. They were irradiated by white synchrotron radiation (SR) beam by the use of cylindrical and toroidal mirrors. The irradiated film was examined using a high-resolution electron microscope alpha and alpha + beta mixture carbyne crystals were grown in round and the elongated shapes. The round crystals were composed of 5-10 nm crystallites of a carbyne form. The elongated crystal grew into a single crystal 100 nm in size. The c-axes of both grown crystals were oblique to the film. The growth of the carbynes was discussed as being the result of nucleation due to graphite microcrystallites formed by SR beam irradiation. (C) 2001 Elsevier Science B.V. All rights reserved.
  • K Hanamoto, A Hirai, M Sasaki, Y Kimura, K Miyatani, C Kaito, Y Nakayama  NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT  467-  1213  -1216  2001/07  [Not refereed][Not invited]
     
    The effect of SR irradiation on the crystal growth of indium oxide films prepared by electron-beam evaporation have been studied by X-ray diffraction and high-resolution electron microscopy. An as-deposited film showed In2O3 crystallites with a size of 2-10 nm. The crystallites were destroyed by SR irradiation under oxygen flow, SR irradiation without oxygen flow showed the growth of In2O3 crystallites up to 20 nm in size with accompanying deoxidation and indium-particle growth. The as-deposited film was composed of variously oriented particles. Periodic oxygen decomposition of the film preferentially took place on the (0 0 1)-oriented particle. (C) 2001 Elsevier Science B.V. All rights reserved.
  • C Kaito, A Ito, S Kimura, Y Kimura, Y Saito, T Nakada  JOURNAL OF CRYSTAL GROWTH  218-  (2-4)  259  -264  2000/09  [Not refereed][Not invited]
     
    The growth of In2S3 and InS by vacuum evaporation of indium metal on the surface of molybdenite has been observed in the initial stage of film growth. By the increment of In2S3 particle size, InS was also produced. By the increase of the film thickness to more than 20 nm, indium crystal predominately grew. The topotactic relations among the substrate and sulfide are as follows: (0 0 0 1)(MoS2) parallel to(1 1 0)(In2S3), [1 0 (1) over bar 0](MoS2) parallel to[1 1 1](In2S3) or (0 0 0 1)(MoS2) parallel to(1 1 0)(In2S3), [1 0 (1) over bar 0](MoS2) parallel to[1 0 0](In2S3). (C) 2000 Elsevier Science B.V. All rights reserved.
  • T Nakao, T Nakada, Y Nakayama, K Miyatani, Y Kimura, Y Saito, C Kaito  THIN SOLID FILMS  370-  (1-2)  155  -162  2000/07  [Not refereed][Not invited]
     
    In order to clarify the structure of indium oxide him containing tin and tin oxides, various In2O3 based films prepared by vacuum evaporation were studied using high-resolution electron microscope (HREM). Indium tin oxide (ITO) film was composed of In2O3 and SnO. SnO crystal also contained (110) or (101) crystallographic shear (CS) structures that indicate excess amounts of tin. The CS structure was also found in a commercial ITO film having the resistivity of 2 x 10(-4) Omega cm. (C) 2000 Elsevier Science S.A. All rights reserved.
  • C. Kaito, H. Nakamura, S. Kimura, Y. Kimura, T. Nakada, Y. Saito  Thin Solid Films  359-  (2)  283  -287  2000/01/31  [Not refereed][Not invited]
     
    In order to clarify the structures of thin Cr films by their real space images, Cr films of various thicknesses, prepared using vacuum deposition, have been observed using a high resolution electron microscope. The amorphous chromium films were composed of microcrystallites of the order of 3 nm. The crystallite structure was δ-Cr. The well-known bcc chromium particles were observed in thick and large crystal particles. The stability of small particles is discussed.
  • Spontaneous Alkali Halide Formation by the Use of KBr-KCl System
    Y. Kimura, Y. Saito, T. Nakada, C. Kaito  Physics of Low-Dimensional Structures  1/2-  L1-L7  2000  [Not refereed][Not invited]
  • Surface oxide on tin and indium ultrafine particles and their oxidation process
    C Kaito, T Nakao, Y Ato, Y Kimura, S Kimura, T Nakada, Y Saito  PHYSICS OF LOW-DIMENSIONAL STRUCTURES  12-  53  -60  1999  [Not refereed][Not invited]
     
    The structure of surface oxide on tin and indium metallic particles and their oxidation process at a temperature higher than the melting point of the particles have been elucidated on the basis of observations using a high-resolution electron microscope (HREM). In the case of tin particles, the surface oxide layer spontaneously produced by exposure to air was composed of microcrystallites with the size of 1 similar to 2 nm. In the case of indium, the (222) crystal of In2O3 covered the surface of indium particles. In the oxidation of tin at a temperature higher than its melting point, crystal shear structure which were present as the metal-excess Sn3O2 or Sn4O3 oxides have been found. In the case of indium particles, a definite crystallographic correlation, i.e., In2O3 (111) // In(110), has also been observed during the solidification of central metal. The fundamental behaviors of low-dimensional In and Sn particles can be observed.

Awards & Honors

  • 2019/10 The Japanese Association for Crystal Growth 36th Best Paper Award
     Elucidation of formation processes of cosmic dust particles based on homogeneous nucleation experiments 
    受賞者: KIMURA Yuki
  • 2019/05 Japan Geoscience Union The 3rd Nishida Prize
     
    受賞者: KIMURA Yuki
  • 2019/02 Hokkaido University President's Award for Outstanding Research
     
    受賞者: KIMURA Yuki
  • 2018/02 日本学術振興会 第14回(平成29年度)日本学術振興会賞
     
    受賞者: 木村 勇気
  • 2017/01 宇宙航空研究開発機構 宇宙科学研究所 第3回宇宙科学研究所賞
     
    受賞者: 木村 勇気
  • 2017/01 北海道大学 北海道大学研究総長賞
     
    受賞者: 木村 勇気
  • 2016/10 日本マイクログラビティ応用学会 第12回 (2016年度) 日本マイクログラビティ応用学会研究奨励賞
     
    受賞者: 木村 勇気
  • 2014/03 日本セラミックス協会 第39回学術写真賞 最優秀賞
     隕石内部のSEM, Holography 観察からわかる太陽系形成期の「水」の痕跡 
    受賞者: 佐藤岳志;山本和生;木村勇気
  • 2013 "Schieber Prize", the International Organization for Crystal Growth
  • 2013 "Schieber Prize", the International Organization for Crystal Growth
  • 2012 日本物理学会領域9若手奨励賞
  • 2012 日本物理学会領域9若手奨励賞
  • 2011 Best Poster Award at the International Conference on Materials for Advanced Technologies, 2011.
  • 2011 Best Poster Award at the International Conference on Materials for Advanced Technologies, 2011.
  • 2010 平成22年度科学技術分野の文部科学大臣表彰 若手科学者賞
  • 2010 平成22年度科学技術分野の文部科学大臣表彰 若手科学者賞
  • 2009 International School of Crystallization 2009 Accommodation Grant
  • 2009 International School of Crystallization 2009 Accommodation Grant
  • 2008 日本結晶成長学会 第六回奨励賞
  • 2008 日本結晶成長学会 第六回奨励賞
  • 2007 2006年度 日本惑星科学会 最優秀研究者賞
  • 2007 2006年度 日本惑星科学会 最優秀研究者賞
  • 2002 第32回 結晶成長国内会議 講演奨励賞
  • 2002 第32回 結晶成長国内会議 講演奨励賞

Research Grants & Projects

  • 核生成
    日本学術振興会:科学研究費補助金 基盤研究(S)
    Date (from‐to) : 2015/04 -2020/03 
    Author : 木村 勇気
  • 電子線ホログラフィーによるナノスケール隕石磁気学の提唱
    日本学術振興会:科学研究費補助金 挑戦的萌芽
    Date (from‐to) : 2016/04 -2018/03 
    Author : 木村 勇気
  • フルイド反応透過電子顕微鏡を用いた微粒子合成と光触媒活性の溶液中その場観察研究
    日本学術振興会:日本学術振興会 二国間交流事業共同研究
    Date (from‐to) : 2015/04 -2017/03 
    Author : 木村 勇気
  • 気相からの核生成と宇宙ダスト
    国立研究開発法人宇宙航空研究開発機構:平成28年度短時間微小重力実験
    Date (from‐to) : 2016/10 -2017/02 
    Author : 木村 勇気
  • 文部科学省:科学研究費補助金(挑戦的萌芽研究)
    Date (from‐to) : 2013 -2014 
    Author : 木村 勇気
  • 文部科学省:科学研究費補助金(若手研究(A))
    Date (from‐to) : 2012 -2014 
    Author : 木村 勇気
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(挑戦的萌芽研究)
    Date (from‐to) : 2010 -2011 
    Author : Yuki KIMURA, Itsuki SAKON
     
    There are a lot of unidentified infrared (UIR)features in the astronomical spectra. We assumed the reason that is characteristic physical parameters of nanoparticles, because no one ever considers the properties of nanoparticle, although cosmic dust has nanometer in size. To identify the UIR features, we constructed a new system, which is able to measure IR spectra of free frying as-grown nanoparticles. Our results showed that the free frying nanoparticles have different features compared with that in the spectra of bulk and nanoparticles embedded into a KBr pellets. UIR features will be identified based on our concept.
  • 文部科学省:科学研究費補助金(若手研究(A))
    Date (from‐to) : 2010 -2011 
    Author : 木村 勇気
     
    惑星系の形成過程に伴う物質進化過程の解明という地球惑星科学の第一級の課題に対して、宇宙固体微粒子(宇宙ダスト)の形成や結晶化過程を実験的に解明する。宇宙ダストは容器の無い宇宙空間で生成する為に、大きな過冷却度がついた後に生成することが容易に想像できる。特に、気相からの凝縮実験(煙の実験)において非接触で生成するナノ粒子の成長過程を干渉計を用いてその場観察することで、気相中でのナノ粒子生成時の核形成温度(過冷却度)や成長速度などを定量化することが目的である。ここで、ナノ粒子の"液体のような"非常に早い拡散現象が鍵になると考えている。物質科学と地球惑星科学分野との境界領域に新たな研究分野を形成する研究課題になる。初年度に組んだ、2波長マッハツェンダー干渉計を用いて、核形成温度と濃度を同時に測定することに成功した。また、凝縮温度と生成粒子のサイズを同時に説明可能なナノ粒子の"実効的な"表面張力と吸着係数を、核生成理論を用いることで同時に決定できることが明らかになり、当初の想定以上の成果を挙げられた。例えば、マンガンに関しては、表面エネルギーはナノ粒子であっても、バルクと同程度の値で、吸着係数は約0.4であった。さらに、ナノ粒子の融点降下や拡散速度の特異現象により液滴状融合成長が頻繁に起こることで核の数を減らす現象を定量的に示した。これにより、実際に宇宙ダストが生成する温度、そのサイズ、数密度などを核生成理論から予測可能になると期待される。
  • ナノ領域の特異現象と46億年前の微粒子形成
    科学研究費補助金
    Date (from‐to) : 2008 -2011
  • Grain formation 4.6 Billion Years Ago based on anomalous phenomena appeared in nano-region
    Grant-in-Aid for Scientific Research
    Date (from‐to) : 2008 -2011
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(若手研究(スタートアップ))
    Date (from‐to) : 2007 -2008 
    Author : Yuki KIMURA
     
    宇宙固体微粒子(ダスト)の類似物としての微粒子を実際に研究室で合成し、その光学特性や高温での振る舞い等を調べる事で、星・惑星形成過程におけるダストの果たす役割を明らかとする事を目的に研究を展開した。その結果、(1)結晶質珪酸塩微粒子の生成条件と非晶質珪酸塩微粒子の低温での結晶化過程を明らかにした。(2) 質量に依存しない酸素の同位体分別を示す珪酸塩微粒子の生成に世界で初めて成功し、ダストの生成にプラズマが重要であることをしめした。(3) 様々な天体に幅広く分布しているPAH のクラスターを実験室で再現し、その光学特性を明らかにした。
  • 原始太陽系星雲中での無機・有機ダストの振る舞いに関する実験的アプローチ」
    科学研究費補助金
    Date (from‐to) : 2007 -2008
  • 宇宙環境下でのダストの創製・変成・挙動に関する実験的アプローチ
    科学研究費補助金
    Date (from‐to) : 2004 -2006
  • ナノ構造粒子の創製および特異現象の解明実験
    科学研究費補助金
    Date (from‐to) : 2002 -2003

Educational Activities

Committee Membership

  • 2011 -2012   日本物理学会領域9   運営委員   日本物理学会領域9
  • 2007 -2009   Reviewer of the award in the Japanese Society for Planetary Sciences   幹事   Reviewer of the award in the Japanese Society for Planetary Sciences
  • 2006   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

Social Contribution

Social Contribution

Social Contribution

  • ナノ粒子特有の振る舞いから宇宙の謎に迫る
    Date (from-to) : 2017/11/11-2017/11/11
    Role : Lecturer
    Event, Program, Title : 第26回先端科学移動大学2017(市民講座)
    General 旭川市科学館「サイパル」
  • 煙ってなあに
    Date (from-to) : 2017/11/10-2017/11/10
    Role : Lecturer
    Event, Program, Title : 第26回先端科学移動大学2017(高等学校訪問授業)
    旭川南高等学校


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