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Sedimentation of substitutional solute atoms in condensed matter; New type of diffusion

凝縮物質中の置換型溶質原子の沈降; 新しいタイプの拡散

真下 茂

Mashimo, Tsutomu

100万Gレベルの超重力場下では凝縮物質中で原子の沈降や非平衡な結晶化学状態が期待できる。しかしながら、生化学分野で分子や高分子の沈降が使われていながら、超重力場下の物質研究は未踏の分野として残っている。われわれは100万Gレベルの重力場を高温で発生できる装置を開発し、Bi-Sb, In-Pb, Bi-PB系などの合金系や金属間化合物で置換型溶質原子の沈降を世界ではじめて実現した。Bi-Sb系では沈降の拡散係数は化学ポテンシャルによる拡散係数に比べて20倍以上大きく見積もられた。そのメカニズムはまだ不明であるが、この凝縮物質中の置換型溶質原子の沈降は新しいタイプの拡散に位置付ることができる。本論文では超重力場下の原子の沈降の研究の最近の発展をレビューし、拡散メカニズムと応用を議論した。

Mega-gravity field realizes the sedimentation of even atoms, and is expected to create a nonequilibrium crystal-chemical state in condensed matter. We presented a self-consistent diffusion equation for sedimentation of atoms in condensed matter. Next, we developed an ultracentrifuge to generate strong acceleration field of over 1 million g, and, recently, succeeded in realization of the sedimentation of substitutional solute atoms in some alloys. The diffusion coefficients of sedimentation on Bi-Sb alloy were estimated to be much greater than those of conventional one. It is suggested that the sedimentation of substitutional atoms in solids or liquids can be included in a new type of diffusion, where the diffusion mechanism was yet unknown. In this article, the recent progress in the investigation of sedimentation of atoms under mega-gravity field is reviewed, and the diffusion mechanism is discussed. The application of the mega-gravity field is also discussed.

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