Effect of annealing treatment on the anti-pulverization and anti-corrosion properties of La0.67Mg0.33Ni2.5Co0.5 hydrogen storage alloy

• Published in: Journal of rare earths Vol. 33; no. 4; pp. 417 - 424
• Main Author: 李平 张骏 翟富强 马光 徐丽 曲选辉
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2015
• Subjects: AB2型; cyclical stability; electrochemical performance; hydrogen storage alloy; ICP-AES; La-Mg based metal hydride; rare earths; X射线衍射分析; 抗粉化; 抗腐蚀能力; 特性; 贮氢合金; 退火处理; hydrogen storage alloy; La-Mg based metal hydride; electrochemical performance; cyclical stability; rare earths
• ISSN: 1002-0721; 2509-4963
• DOI: 10.1016/S1002-0721(14)60435-X

The Lao.67Mg0.33Ni2.5Co0.5 hydrogen storage alloy was prepared by the vacuum intermediate frequency induction furnace followed by annealing treatment. The pulverization degree of both the as-cast and annealed alloy powders after gaseous hydriding and dehydriding cycle was investigated and the discovery was that annealing treatment could hardly ameliorate their anti-pulverization ability. The element content of La, Mg, Ni and Co existing in electrolyte before and after the electrochemical cycles by using ICP-AES technology was also analyzed and it showed that a large amount of La and Mg were dissolved in the electrolyte, but the amount of dissolution for La and Mg significantly declined when the alloy was annealed. The XRD analysis revealed that all the al- loys consisted of two main phases AB3 and AB2 and a residual phase AB5 while annealing treatment made the AB2 phase decrease slightly. Furthermore, the anti-corrosion abilities of various elements in different phases of the as-cast and annealed alloy samples were studied by analyzing the element （La, Mg, Ni, Co） change with the corrosion time in phases AB3 and AB2 by means of EDS. It turned out that the element of La was mainly corroded out from the phase AB2 while not easily from the phase AB3. However, the element of Mg was both easily corroded out from the phases AB2 and AB3, but the corrosion was more obvious in the phase AB3. Therefore, annealing improved the anti-corrosion performances of La and Mg in the phase AB2.