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Pb
intermetallic compoundOno, Masao; Huang, X. S.*; Shibata, Yasuhiro*; Iguchi, Yusuke*; Sakai, Seiji; Maekawa, Masaki; Chen, Z. Q.*; Osakabe, Toyotaka; Kawasuso, Atsuo; Naramoto, Hiroshi*; et al.
Proceedings of 1st International Conference on Diffusion in Solids and Liquids (DSL 2005), p.531 - 533, 2005/07
Recently, we formed atomic-scale graded structures in some miscible alloys and observed the decomposition in BiPb intermetallic compound by sedimentation of atoms under strong gravitational field. In this study, we measured positron lifetime of centrifuged BiPb, to which the composition change was very small as it was treated at low temperature. It was found that the positron lifetime became longer than that of starting state. This indicated that the point defects (vacancy or divacancy) increased in the sample by centrifugal treatment. We are now investigating the relationship between increase in point defects and sedimentation of atoms.
Ono, Masao; Kinoshita, Takahiro*; Ueno, Hideto*; Huang, X.*; Osakabe, Toyotaka; Mashimo, Tsutomu
Materials Transactions, 46(2), p.219 - 224, 2005/02
Times Cited Count：8 Percentile：54.95(Materials Science, Multidisciplinary)Ultracentrifuge experiments were performed on the In-Pb system to study the sedimentation of atoms and phase equilibrium. After the experiments, the graded structures were obtained. Pb-rich phase (f.c.c) and In-rich phase (tetragonal) appeared at the strong- and weak-gravitational field sides of the sample, respectively, from starting state of 
-phase. And, the continuous changes in lattice parameters were observed in each phase. These observation results showed that the graded structure was continuous in atomic scale, and was formed by the sedimentation of atoms. Composition profiles of the centrifuged samples for 31.3 h, 60 h and 150 h showed that the composition change reached the steady state within 60 hours. The diffusion coefficient for sedimentation was estimated to be about 8 times larger than that for usual diffusion by the simulation. The result indicated that the diffusion mechanism of the sedimentation was different from the conventional ones.
Mashimo, Tsutomu; Huang, X.; Osakabe, Toyotaka; Ono, Masao*; Nishihara, Masamichi*; Ihara, Hirotaka*; Sueyoshi, Masanori*; Shibasaki, Koji*; Shibasaki, Shiro*; Mori, Nobuo*
Review of Scientific Instruments, 74(1), p.160 - 163, 2003/01
Times Cited Count：54 Percentile：89.18(Instruments & Instrumentation)An ultracentrifuge apparatus, which could generate an ultra-strong gravitational field of even 
1,000,000 (1 million) G (1G = 9.8 m/s
) in a wide temperature range up to 500
C with high stability controls, was developed for new materials science research. The system consisted of an air turbine motor with ceramic ball bearings and dumper section, a sample rotor with an outer diameter up to 160 mm, a vacuum chamber and a heating system. The ultracentrifuge experiments using the 70 and 80 mm-diam rotors made of titanium alloy with rotational speeds of up to 170,000 rpm at temperatures of even over 200C for 100 hours with the ripples of 
0.05% and 1 degree, respectively, were successfully performed, where the maximum gravitational field at sample was 1,000,000 G, and the potential energy and sample volume were larger than those of the Kumamoto University one (Rev. Sci. Instr. 67, 3170 (1996)) by 1.9 and 4 times, respectively.
