HISAKI Project Team

稲富 裕光

イナトミ ユウコウ  (Yuko Inatomi)

基本情報

所属
国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 学際科学研究系 教授 (研究主幹)
総合研究大学院大学 物理科学研究科 宇宙科学専攻 教授
学位
博士(工学)(1992年3月 東京大学)

研究者番号
50249934
ORCID ID
 https://orcid.org/0000-0002-2845-9636
J-GLOBAL ID
200901018824285220
researchmap会員ID
1000144502

宇宙環境の特性を利用した物質科学研究を通して地球上のみならず宇宙空間における物質の変化を探求しています。具体的には、観測ロケット・国際宇宙ステーションなど宇宙飛翔体による微小重力、遠心機による過重力、強磁場など様々な環境を利用して、凝固・結晶成長の素過程の解明、環境相中の輸送現象の解明と制御、新しい材料プロセスの開発に取り組んでいます。


論文

 197
  • Nirmal Kumar Velu, Yasuhiro Hayakawa, Haruhiko Udono, Shunya Sakane, Yuko Inatomi
    ACS Applied Materials and Interfaces 16(35) 46433-46441 2024年9月4日  査読有り最終著者
    Materials with enhanced electron and reduced phonon transport properties are preferred for thermoelectric applications. The defect engineering process can optimize the interrelated electron and phonon transport properties to enhance thermoelectric performance. As the influence of various crystalline defects on the functional properties of materials is diverse, it is crucial to scale, optimize, and understand them experimentally. With this perspective, crystalline defects in InGaSb ternary alloys were engineered and their influence on the thermoelectric properties was studied experimentally. Crystalline defects such as point defects, dislocations, and compositional segregations were induced in In0.95Ga0.05Sb crystals by the addition of excess constituent elements, In, Ga, or Sb. The addition of excess Ga increased point defects, whereas excess Sb reduced dislocation densities. The thermoelectric figure of merit value (ZT) of In0.95Ga0.05Sb+Ga0.02 was recorded to be 0.87 at 573 K, which is the highest among other reported values of III-V semiconductors. The collective interactions of compositional segregations, point defects, and dislocations with electrons and phonons enhanced the ZT in this study.
  • Rachid Ghritli, Yasunori Okano, Yuko Inatomi, Sadik Dos
    Journal of Chemical Engineering of Japan 56(1) 2222757 2023年12月31日  査読有り
  • Kimura, S., Ishikawa, S., Hayashi, N., Fujita, K., Inatomi, Y., Suzuki, S.
    Frontiers in Microbiology 14 1253436 2023年12月  査読有り
    <jats:p>Planetary protection is a guiding principle aiming to prevent microbial contamination of the solar system by spacecraft (forward contamination) and extraterrestrial contamination of the Earth (backward contamination). Bioburden reduction on spacecraft, including cruise and landing systems, is required to prevent microbial contamination from Earth during space exploration missions. Several sterilization methods are available; however, selecting appropriate methods is essential to eliminate a broad spectrum of microorganisms without damaging spacecraft components during manufacturing and assembly. Here, we compared the effects of different bioburden reduction techniques, including dry heat, UV light, isopropyl alcohol (IPA), hydrogen peroxide (H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>), vaporized hydrogen peroxide (VHP), and oxygen and argon plasma on microorganisms with different resistance capacities. These microorganisms included <jats:italic>Bacillus atrophaeus</jats:italic> spores and <jats:italic>Aspergillus niger</jats:italic> spores, <jats:italic>Deinococcus radiodurans</jats:italic>, and <jats:italic>Brevundimonas diminuta</jats:italic>, all important microorganisms for considering planetary protection. <jats:italic>Bacillus atrophaeus</jats:italic> spores showed the highest resistance to dry heat but could be reliably sterilized (i.e., under detection limit) through extended time or increased temperature. <jats:italic>Aspergillus niger</jats:italic> spores and <jats:italic>D. radiodurans</jats:italic> were highly resistant to UV light. Seventy percent of IPA and 7.5% of H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> treatments effectively sterilized <jats:italic>D. radiodurans</jats:italic> and <jats:italic>B. diminuta</jats:italic> but showed no immediate bactericidal effect against <jats:italic>B. atrophaeus</jats:italic> spores. IPA immediately sterilized <jats:italic>A. niger</jats:italic> spores, but H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> did not. During VHP treatment under reduced pressure, viable <jats:italic>B. atrophaeus</jats:italic> spores and <jats:italic>A. niger</jats:italic> spores were quickly reduced by approximately two log orders. Oxygen plasma sterilized <jats:italic>D. radiodurans</jats:italic> but did not eliminate <jats:italic>B. atrophaeus</jats:italic> spores. In contrast, argon plasma sterilized <jats:italic>B. atrophaeus</jats:italic> but not <jats:italic>D. radiodurans</jats:italic>. Therefore, dry heat could be used for heat-resistant component bioburden reduction, and VHP or plasma for non-heat-resistant components in bulk bioburden reduction. Furthermore, IPA, H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>, or UV could be used for additional surface bioburden reduction during assembly and testing. The systemic comparison of sterilization efficiencies under identical experimental conditions in this study provides basic criteria for determining which sterilization techniques should be selected during bioburden reduction for forward planetary protection.</jats:p>
  • Nirmal Kumar Velu, Yasuhiro Hayakawa, Haruhiko Udono, Yuko Inatomi
    Journal of Materials Science: Materials in Electronics 34(19) 1480 2023年7月  査読有り最終著者
    Thermoelectric materials with optimum carrier concentration of the order of 1019–1020/cm3 are required to obtain a high figure of merit (ZT) value. As undoped In0.8Ga0.2Sb has a lower carrier concentration (~1016/cm3), Te impurity was doped between low (1 × 1018/cm3) and high level (1 x 1021/cm3) to understand the effects of doping on its thermoelectric properties. The undoped and Te-doped In0.8Ga0.2Sb crystals retained cubic zinc blende crystal structure irrespective of heavy doping of Te element. In addition to the optical phonon vibrational modes, acoustic phonon modes were also present when the doping concentration exceeded 1 × 1018/cm3. The carrier concentration in Te-doped In0.8Ga0.2Sb crystals were varied in the range 1018–1020/cm3. Te-doped In0.8Ga0.2Sb with concentration 1 × 1018/cm3 was recorded a higher power factor because of its lower resistivity and higher mobility than other crystals. The ZT of Te-doped In0.8Ga0.2Sb (1 × 1018/cm3) was higher than other samples at 300–450 K. This study revealed that the optimum Te dopant concentration to enhance the ZT value of InxGa1−xSb is 1 x 1018/cm3 for optimizing its properties toward mid-temperature thermoelectric applications.
  • Nirmal Kumar Velu, Yasuhiro Hayakawa, Haruhiko Udono, Yuko Inatomi
    Journal of Materials Science 58(19) 7995-8004 2023年5月  査読有り最終著者
    Thermoelectric devices require p-type and n-type semiconductors with similar chemical, mechanical and thermoelectric properties to achieve maximum efficiency. To match with n-type In0.95Ga0.05Sb crystals for the fabrication of thermoelectric device, zinc (Zn) element was doped with In0.95Ga0.05Sb crystal intentionally to change its conductivity from n-type to p-type and its thermoelectric properties were studied. The Zn-doped In0.95Ga0.05Sb crystals grown by directional solidification were free from micro-cracks and their composition was distributed homogeneously. The carrier concentration was increased upon doping with Zn element. The resistivity of Zn-doped In0.95Ga0.05Sb increased with increasing temperature that showed degenerate semiconducting characteristics resulted from heavy doping. The Peierls distortion resulting from Sb–Sb interaction was observed in Zn-doped In0.95Ga0.05Sb crystals. The higher electron contribution and lower phonon contribution to total thermal conductivity were obtained in Zn-doped In0.95Ga0.05Sb than undoped crystals. The maximum ZT of 0.24 at 573 K was achieved by Zn-doped In0.95Ga0.05Sb with dopant concentration 1 × 1020 atoms/cm3. The ZT achieved is the highest among other reported values of p-type III–V semiconductors.

MISC

 277

書籍等出版物

 12

講演・口頭発表等

 550

担当経験のある科目(授業)

 4

共同研究・競争的資金等の研究課題

 36

産業財産権

 3

学術貢献活動

 5

社会貢献活動

 15