摘要
用冷坩埚磁悬浮熔炼方法制备铸态La0.7Mg0.3(Ni0.85Co0.15)3.4贮氢电极合金,并分别在1 073 K、1 173 K和1 273 K温度下热处理8 h得到热处理态合金,研究了合金的Mg含量、相结构、电化学性能、显微硬度及相应电极的表面状态.研究结果表明:合金中Mg的质量分数随着热处理温度的升高从2.38%降低到2.03%;铸态及1 173 K热处理态合金的主相均为Ce2Ni7型六方相,还包括CaCu5型六方相、PuNi3型菱方相、MgCu2型立方相及BCr型正交相,热处理还使各组成相的晶胞体积均有所增加;随着热处理温度的升高,合金放氢平台的平台压力先降低到0.004 3MPa,然后升高到0.012 1 MPa,再降低到0.007 1 MPa;合金电极的最大放电容量先增加到406.8mA.h/g,然后减小到361.8 mA.h/g;循环稳定性从铸态时的59.6%不断增加到76.0%.
The as-cast La0.7Mg0.3 （Ni0.85Co0.15）3.4 hydrogen storage electrode alloy was prepared by cold crucible melting, and then was heat-treated at 1 073 K, 1 173 K or 1 273 K for 8 hours under argon gas atmosphere. The magnesium content, phase structure, microhardness of the alloys, and the electrochemical properties and surface of the corresponding electrodes were investigated. The results show that the as-cast alloy and the one heat-treated at 1 173 K the consist of hexagonal Ce2Ni7-type main-phase, hexagonal CaCu5-type phase, rhombohedral PuNi3-type phase, cubic MgCu2-type Laves-phase and orthorhombic BCr-type phase; with the increasing heat treatment temperature, the magnesium content decreases from 2.38% to 2.03 %; the cell volume of all these phases increases; the hydrogen-desorption plateau pressure lowers to 0. 004 3 MPa, then heightens to 0.012 1 MPa, and lowers again to 0. 007 1 MPa; the maximum discharge capac ity first increases to 406.8 mA · h/g and then reduces to 361.8 mA · h/g; and the cyclic stability is improved from 59. 6% to 76.0% continuously.
出处
《西安交通大学学报》
EI
CAS
CSCD
北大核心
2007年第11期1373-1379,共7页
Journal of Xi'an Jiaotong University
基金
北京有色金属研究总院-厦门钨业股份有限公司贮氢合金联合实验室资助项目(2006090909)
关键词
热处理
贮氢电极合金
相结构
电化学性能
heat treatment
hydrogen storage alloy
phase structure
electrochemical property
