Effect of annealing temperature on microstructure and electrochemical performance of La0.75Mg0.25Ni3.5Co0.2 hydrogen storage electrode alloy

• Published in: Journal of rare earths Vol. 26; no. 1; pp. 99 - 104
• Main Author: 董小平 吕反修 张羊换 杨丽颖 王新林
• Format: Journal Article
• Language: English
• Published: Department of Functional Material Research, Central Iron and Steel Research Institute,Beijing 100081,China 01.02.2008; School of Materials Science and Engineering,University of Science and Technology Beijing,Beijing 1O0083,China; Department of Functional Material Research, Central Iron and Steel Research Institute,Beijing 100081,China%School of Materials Science and Engineering,University of Science and Technology Beijing,Beijing 1O0083%Department of Functional Material Research, Central Iron and Steel Research Institute,Beijing 100081,China; School of Material,Inner Mongolia University of Science and Technology,Baotou 014010,China%School of Materials Science and Engineering,University of Science and Technology Beijing,Beijing 100083%China
• Subjects: 微观结构; 电气化学; 退火工艺; annealing temperature; microstructure; A2B7-type La-Mg-Ni based alloy; cyclic stability; rare earths
• ISSN: 1002-0721; 2509-4963
• DOI: 10.1016/S1002-0721(08)60046-0

To improve the cyclic stability of La-Mg-Ni system alloy, as-cast La0.75Mg0.25Ni3.5Co0.2 alloy was annealed at 1123, 1223, and 1323 K for 10 h in 0.3 MPa argon. The microstructure and electrochemical performance of different annealed alloys were investigated systematically by X-Ray Diffraction （XRD）, Scanning Electron Microscopy （SEM）, X-Ray Photoelectron Spectroscopy （XPS）, and electrochemical experiments. The results obtained by XRD and SEM showed that the as-cast and annealed （1123 K） alloys had multiphase structure containing LaNis, （La, Mg）2（Ni, Co）7 and few LaNi2 phases. When annealing temperatures approached 1223 and 1323 K, LaNi2 phase disappeared. The annealed alloys at 1223 and 1323 K were composed of LaNi5, （La, Mg）2（Ni, Co）7 and （La, Mg）（Ni, Co）3 phases. With increasing annealing temperature, the maximum discharge capacity of the alloy decreased monotonously, but the cyclic stability was improved owing to structure homogeneity and grain growth after annealing, as well as the enhancement of anti-oxidation/corrosion ability and the suppression of pulverization during cycling in KOH electrolyte.