Papers by Keyword: Ultra-Strong Gravitational Field

Abstract: In this study, we investigate the crystalline states and conditions for the grain-refinement of Bi70Sb30 (at.%) alloy. It was considered under an ultra strong gravity field, the crystals were fine-grained from the primary grain sizes of several mm to several tens of mm, and the crystal growth followed with formation of graded-composition structure due to sedimentation of atoms along the direction of gravity. It was found that for the crystal-grain refinement in Bi70Sb30 alloy the minimum gravitational field and the minimum time duration were at least 160,000 G and 10 hours, respectively at about 200 °C.

Abstract: Ultra-strong gravitational field (Mega-gravity field) causes the sedimentation of even atoms (diffusion), and is expected to create a nonequilibrium crystal-chemical state in multi-component condensed matter. However, the materials science research under mega-gravity field has now remained as an unexploited field, while the sedimentation of molecules or polymer had been used in biochemistory. We presented a self-consistent diffusion equation for sedimentation of atoms in condensed matter. Next, we developed an ultracentrifuge apparatus to generate strong acceleration field of over 1 million (1x106) g at temperature range up to 〜300 °C, and, recently, succeeded in realization of the sedimentation of substitutional solute atoms in some alloys of Bi-Sb, In-Pb, Bi-Pb systems, etc. The diffusion coefficients in sedimentation on Bi-Sb alloy were estimated to be much greater than those at normal conditions by a factor of >20. It is suggested that the sedimentation of substitutional atoms in solids or liquids can be explained in a new type of diffusion, where the diffusion mechanism for substitutional solute atoms 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.