Development of the ultracentrifuge system of condensed matter

对于凝聚态物质中由离心力或重力场引起的原子或分子的扩散现象（原子的沉降），还没有进行广泛的理论或实验研究。本研究的目的是开发超高速加速场在高温下长时间产生系统（超离心系统），以实现凝聚态物质中原子的沉降。我们生产了转速超过20万转/分钟，外径40毫米的超高旋转系统。该系统由带油浮轴承的高温空气涡轮电机和可加热到200℃以上的钛合金试样架组成，实现了大于22万转/分的超高转速，最大加速场大于1 000 000 9。在转速为160000转/分（加速度约为570000克）、温度为110℃、时间为8小时的Au-In系统上进行了超离心实验，考察了沉淀情况。通过扫描电镜观察了金的浓度分布。另一方面，其中一位研究者（Mashimo）用平均场理论近似提出了凝聚态物质中原子沉降的自洽理论。并对二组分和三组分体系的平衡态沉降进行了数值分析，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.