Microstructual Control Using High-Pressure Allotropy

2018 Fiscal Year Final Research Report

• Project/Area Number: 26220909
• Research Category: Grant-in-Aid for Scientific Research (S)
• Allocation Type: Single-year Grants
• Research Field: Material processing/Microstructural control engineering
• Research Institution: Kyushu University
• Principal Investigator: HORITA Zenji 九州大学, 工学研究院, 教授 (20173643)
• Co-Investigator(Kenkyū-buntansha): 有田 誠 九州大学, 工学研究院, 助教 (30284540) ; 生駒 嘉史 九州大学, 工学研究院, 助教 (90315119)
• Research Collaborator: WATANABE masashi ; EDALATI kaveh ; TANAKA isao
• Project Period (FY): 2014-05-30 – 2019-03-31
• Keywords: 巨大ひずみ加工 / 同素変態 / 高圧力 / 金属（Ti, Zr） / 半導体 / セラミックス

Outline of Final Research Achievements

Metallic elements such as Ti and Zr take a hexagonal close-packed (hcp) structure at ambient pressure and temperature and they transform from the hcp structure (α phase) to a hexagonal structure (ω phase) as the pressure increases [1,2]. This ω phase with a hard and brittle nature was successfully used as a strengthening phase in the α matrix. Semiconductors such as Si and Ge and ceramics such as TiO2 and ZnO exhibited phase transformation upon application of high pressures together with intense strains. Because the grain sizes became in the nano range, photoluminescence appeared in Si and Ge due to a quantum confinement effect. The band gaps were changed in TiO2 and ZnO so that their ranges were equivalent to visible light and they were able to split water to generate hydrogen.It was confirmed that functional properties improved in Si and Ge including TiO2 and ZnO.

Free Research Field

工学

Academic Significance and Societal Importance of the Research Achievements

高圧巨大ひずみ加工することで、純Tiや純Zrは合金元素添加せずとも、高圧相であるω相を微細に分散させることができ、高強度・高延性化を達成した。宇宙航空および生体材料の発展にも期待できる。SiやGeの半導体では、ナノ結晶粒組織を得ることができ、アニール処理と組み合わせることで可視光域で強い発光特性が発現した。同様にTiO2の酸化物セラミックスでもナノ結晶化でき、可視光線に対しても水分解できる状態に改質できた。いずれも世界で初めての成果で学術的意義は大きい。