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

本项目的目的是设计一种高压装置，该装置使用一种材料，该材料在温度或磁场诱导的相变上显示出长度的变化。在本工作中，我们使用形状记忆合金或超磁致伸缩合金作为产生高压的装置。1)选用了Ti-Ni形状记忆合金作为压力源，马氏体相变长度变化约为3%。这意味着当我们使用30 mm的钛镍棒时，预计长度将改变1 mm。研究了该合金的基本性质。2)利用这种钛镍单向形状记忆合金，当我们使用直径为3 mm的Bridgman型装置时，可以达到10 Gpa左右。3)在通常的实验中，我们重复加热和冷却过程，以获得体积或磁化率等物理量的温度依赖关系。为此，我们采用了长度变化小于单向形状记忆合金的两种形状记忆合金。结果表明，使用该合金可以获得5 Gpa的压力，而使用Ti-Ni形状记忆合金可以达到10 Gpa或更高，这使得这一领域的研究取得了很大的进展。将这种方法应用到钻石顶锤上，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.