Design of new high pressure apparatus using a phase transition induced by temperature or magnetic field

本计画的目的是设计一种高压装置，使用一种在温度或磁场诱导下，相变长度会改变的材料。在目前的工作中，我们使用的形状记忆合金或超磁致伸缩合金作为一个装置，以产生高压。1）选用Ti-Ni形状记忆合金作为压力源，在压力作用下，马氏体相变的长度变化为3%。这意味着当我们使用30 mm Ti-Ni棒时，预计长度变化为1 mm。研究了该合金的基本性能。2）利用这种Ti-Ni单向形状记忆合金，在Bridgman型的3 mm口径的实验装置上，实验压力可达10 GPa左右。3）在常规实验中，我们重复加热和冷却过程，以获得体积和磁化率等物理量的温度依赖性。为此，我们使用了两种方式的形状记忆合金，其中长度的变化小于单向合金。实验结果表明，该合金可以达到5GPa，而Ti-Ni形状记忆合金可以达到10 GPa以上，这是该领域研究的一个重要进展。通过将这种方法应用于金刚石砧，我们将能够获得高于10 GPa的压力。

The purpose of this project is to design a high pressure apparatus using a material which shows a change of the length on the phase transition induced by temperature or magnetic fields. In the present work, we used a shape memory alloy or giant magnetostrictive alloy as a device to generate high pressure. The results im the present work are summarized as follows,1)We selected Ti-Ni shape memory alloy to generate a pressure, in which 3% lengh change is expected on the martensitic transformation. This means that 1 mm length change is expected when we use 30 mm Ti-Ni rod. The fundamental properties of this alloy are investigated.2) By using this Ti-Ni one way shape memory alloy, it was revealed that we can reach about 10 GPa when we use Bridgman type apparatus having a face of 3 mm in diameter.3) In the usual experiments, we repeat heating and cooling process to obtain the temperature dependence of the physical quantities such as volume or magnetic susceptibilities. For this reason, we used the two ways shape memory alloys in which the change in the length is smaller than that of one way alloys. It is found that we can get 5 GPa by using this alloy.To conclude, we can reach 10 GPa or more using the Ti-Ni shape memory alloys, which gives a large progress in this research area. By applying this method to the diamond anvils, we will be able to get higher pressure than 10 GPa.