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KINETIC ISOTOPE EFFECTS ON HYDROGEN ABSORPTION AND DESORPTION BY Pd-ALLOYS

动力学同位素对 Pd 合金吸放氢的影响

基本信息

批准号：
10480106
负责人：
WATANABE Kuniaki
金额：
$ 2.69万
依托单位：
TOYAMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-10480106/
关键词：
hydrogen isotopes Pd-based alloys isotope effect adsorption desorption diffusion kinetics thermodynamics

项目摘要

The present authors have developed a new type of gas chromatography for separation of hydrogen isotopes. It can be operated near room temperature with any replacement gases by use of a column prepared from powder of Pt-8 at%Pd. It is important, however, to investigate in detail isotope effects on hydrogen absorption and desorption to improve the separation efficiency under much moderate operation conditions. The objective of the present research project is to understand mechanisms of hydrogen absorption and desorption, and to evaluate the kinetic as well as thermodynamic isotope effects.Materials considered in this program were Pt-based alloys : Pt-Pd and Pt-Ni alloys. The kinetics was measured using a vacuum microbalance and the thermodynamic properties of alloys were determined from PCT curves obtained by using a conventional constant volume apparatus.It was found that the rates of hydrogen absorption and desorption were determined by adsorption and desorption on the surface, and dif … More fusion in the bulk, where all of them contribute equally. Then the kinetics was described by a diffusion equations as<<numerical formula>>All of the reaction curves obtained in the present study could be reproduced well by this kinetic model. According to the kinetic analyses, the rate of diffusion were not so fast, about 100 times slower than that in pure Pd. The analyses showed that the rate of protium adsorption on the surface is about 1.5 times greater than that of deuterium, whereas protium desorbs from the surface about 1/2 slower than deuterium. As for the diffusion, deuterium can migrate in the bulk about 2 times faster than protium near room temperature for Pd-4at%Pt alloy. This alloy showed a large thermodynamic isotope effect : the isotope effect defined by a ratio of equilibrium pressures, P_<D_2>/P_<H_2>, was found to be about 5 around room temperature. The present research project reveled that the separation efficiency can be improved much by preparing the separation column from materials having large thermodynamic isotope effects, since the kinetic isotope effects are expected to be relative smaller. In this case, however, the present study also showed that powder particles for the column should be small enough to assure equilibrium conditions. These conclusions can be a guiding principle to improve the newly developed gas chromatograph for hydrogen isotope separation working at room temperature using any replacement gases. Less

本文作者研制了一种分离氢同位素的新型气相色谱。它可以在近室温下使用任何置换气体，通过使用由Pt-8at%Pd粉末制备的柱来操作。然而，重要的是，详细研究同位素对氢的吸收和解吸的影响，以提高分离效率在更温和的操作条件下。本研究项目的目的是了解氢的吸收和解吸机制，并评估动力学以及热力学同位素效应。在这个程序中考虑的材料是铂基合金：铂钯和铂镍合金。用真空微天平测定了合金的吸氢动力学，用常规定容仪测定了合金的PCT曲线，并根据PCT曲线确定了合金的热力学性质.结果表明，合金的吸氢和放氢速率取决于表面的吸附和脱附，不同的吸附和脱附速率对合金的吸氢和放氢速率有不同的影响. ...更多信息在大规模的核聚变中，所有的核聚变都有同样的贡献。用扩散方程描述了反应动力学<numerical formula>，得到的动力学曲线均能很好地重现。根据动力学分析，扩散速率不是那么快，大约比纯Pd慢100倍。分析表明，在表面上的吸附率约为氘的1.5倍，而从表面上解吸的速度约为氘的1/2。对于Pd-4at%Pt合金，在室温附近，氘在体相中的迁移速度比氚快2倍。该合金表现出很大的热力学同位素效应：在室温附近，由平衡压力之比P_ /P_定义的同位素效应<D_2><H_2>约为5。本研究项目揭示，由于动力学同位素效应相对较小，因此通过制备具有大的热力学同位素效应的材料的分离柱可以大大提高分离效率。然而，在这种情况下，本研究还表明，用于柱的粉末颗粒应该足够小以确保平衡条件。这些结论对改进新研制的室温氢同位素分离气相色谱仪具有指导意义。少