Search for New Hydrogen Absorbing Alloys

为了抑制二氧化碳气体引起的全球温室效应，必须开发新的能源，如太阳能和地热能，以取代石油和煤炭。吸氢合金可以安全、方便地储存这些能量。本项目的目的是寻找和开发新的优良的吸氢合金。第一个目的是为方便地寻找新合金提供指导原则。本研究表明，金属间化合物在氢气氛中的吸氢性能可以通过差热分析（DTA）来评估。根据放热峰和吸热峰温度的压力依赖性，我们可以确定氢的吸收和解吸焓变和熵变等热力学数据。根据这一指导原则，对Ti、Zr和稀土金属基金属间化合物进行了加氢引起的结构变化、吸氢量和吸氢解吸的热力学参数的评价。特别是对C15 Laves化合物的吸氢性能进行了较为详细的研究。主要结果如下：(1)氢的四面体位置小于0.033 nm的金属间化合物不溶解氢；(2)原子尺寸比小于1.37的化合物在结晶状态下吸收约1.0 （H/M）的氢，而原子尺寸比大于1.37的化合物则被加氢非晶化，不表现出压力平台。

In order to suppress the global greenhouse effect caused by CO_2 gas, it is essential to develop new energy sources such as the solar heat and the heat of the earth in place of petroleum and coal. Hydrogen absorbing alloys can storage such energies safely and conveniently. The purpose of the present project is to search and develop new excellent hydrogen absorbing alloys. The first aim is to make clear the guide principle for searching new alloys convenicntly. The present work has demonstrated that hydrogen absorbing properties can bee evaluted by differential thermal analysis(DTA) of intermetallic compounds in a hydrogen atmosphere. From the pressure dependence of the peak temperature of the exothemic and endothermic peaks, we can determine the thermodynamic data such as the enthalpy and entropy change of hydrogen absorption and desorption. According to this guide principle, the structural changes caused by hydrogenation, the amounts of absorbed hydrogen and the thermodynamic parameters for hydrogen absorption and desorption have been evaluated for Ti, Zr and rare earth metal based intermetallic compounds. Especially, hydrogen absorbing properties of the C15 Laves compounds have been investigated in details. The main results are summarized as follows: (1) hydrogen is not dissolved in the intermetallic compounds in which the tetrahedral sites for hydrogen occupation ARE LESS THAN 0.033 nm, (2) the compounds having the atomic size ratio less than 1.37 absorbs about 1.0 (H/M) of hydrogen in the crystalline state, while those having the ratio more than it amorphize by hydrogenation, which do not exhibit the pressure plateau.