Development of the ultracentrifuge system of condensed matter

对于凝聚态物质中离心力或引力场引起的原子或分子扩散现象（原子沉降），还没有进行过广泛的理论或实验研究。本研究的目的是研制一种能在高温下长时间加速到100万9以上的超高速加速场产生系统（超高速加速场系统），以实现凝聚态物质中原子的沉降。我们生产了转速高于200，000 rpm、样品外径为40 mm的超高旋转系统。该系统由带油浮轴承的高温空气涡轮机电机和钛合金样品保持器组成，可加热至200 ℃以上。我们实现了大于220，000 rpm的超高转速，其中实现的最大加速场大于1，000，000 9。我们对Au-In系统进行了超离心实验，条件是转速160，000 rpm（加速度约570，000 g），温度110 ℃，时间8小时，以检查沉降。通过扫描电镜观察了Au的浓度分布。另一方面，研究者之一（真下）通过平均场理论近似提出了凝聚态中原子沉降的自洽理论。并对二组分和三组分体系中原子沉降的平衡态进行了数值分析，讨论了原子沉降的应用。

No extensive theoretical or experimental studies have been made of the diffusion phenomena of atoms or molecules induced by a centrifugal or gravitational field in condensed matter (sedimentation of atoms). The purpose of this research was the development of the generation system of an ultra-high speed accelerated field up to over 1, 000, 000 9 at high temperature for long time (ultracentrifuge system), to achieve the sedimentation of atoms in condensed matter. We have produced the ultra-high rotating system whose rotation rate is higher than 200, 000 rpm and whose outer specimen diameter is 40 mm. The system consists of the high-temperature air turbine motor with an oil float bearing and the titanium-alloy specimen holder, which can be heated up to over 200 degrees C. We realized the ultra-high rotation of greater than 220, 000 rpm, where the achieved maximum accelerated field was greater than 1, 000, 000 9. We have performed the ultracentrifuge experiment on the Au-In system, when the conditions were 160, 000 rpm in rotation rate (about 570, 000 g in acceleration), 110 degrees C in temperature and 8 hours in time duration, to examine the sedimentation. We observed the distribution of Au concentration by the SEM observation. On the other hand, one of the investigators (Mashimo) proposed the self-consistent theory of the sedimentation of atoms in condensed matter by the mean-field theory approximation. And the numerical analysis at equilibrium state of the sedimentation in two and three component systems was performed to discuss the applications of the sedimentation of atoms.