摘要
The effects of the alloy preparation methods, including the conventional casting, annealing and melt-spinning, on the crystallographic and electrochemical properties of the Co-free LaNi4.95Sn0.3 alloy samples were investigated. The results reveal that the as-cast alloy consists of a main phase of CaCu5-type structure and a little second phase (Sn) with noticeable composition segregation and rather poor cycling stability (S200=40.1%). While the annealed and melt-spun alloys are of single CaCu5-type structure phase with a more homogeneous composition and lower cell volume expansion rate (?V/V) on hydriding, and a dramatically improved cyclic stability (S200=73.6%?76.2%), although their activation rate, initial capacity and high-rate dischargeability are lowered somewhat. It is found that the decrease in both the electrocatalytic activity and the hydrogen diffusion rate of the annealed and melt-spun alloys is the main cause for their relatively lower high-rate dischargeability, and the improved cycling stability is due to their lower volume expansion on hydriding and more uniform composition.
The effects of the alloy preparation methods, including the conventional casting, annealing and melt-spinning, on the crystallographic and electrochemical properties of the Co-free LaNi4.95Sn0.3 alloy samples were investigated. The results reveal that the as-cast alloy consists of a main phase of CaCu5-type structure and a little second phase (Sn) with noticeable composition segregation and rather poor cycling stability (S200=40.1%). While the annealed and melt-spun alloys are of single CaCu5-type structure phase with a more homogeneous composition and lower cell volume expansion rate (AV/V) on hydriding, and a dramatically improved cyclic stability (S200=73.6% -76.2%), although their activation rate, initial capacity and high-rate dischargeability are lowered somewhat. It is found that the decrease in both the electrocatalytic activity and the hydrogen diffusion rate of the annealed and melt-spun alloys is the main cause for their relatively lower high-rate dischargeability, and the improved cycling stability is due to their lower volume expansion on hydriding and more uniform composition.
出处
《中国有色金属学会会刊:英文版》
EI
CSCD
2006年第3期527-531,共5页
Transactions of Nonferrous Metals Society of China
基金
Project(50131040) supported by the National Natural Science Foundation of China
关键词
贮氢合金
钴基合金
材料处理
晶体结构
电化学性能
结晶
稀土
hydrogen storage alloy
Co-free alloy
material processing
crystal structure
electrochemical property