铸态和快淬态Mm(NiCoMnAl)5Bx (x=0～0.4)贮氢合金的微观结构与电化学性能

用铸造及快淬工艺制备了低钴AB5型MmNi3.8Co0.4Mn0.6Al0.2Bx (x=0, 0.1, 0.2, 0.3, 0.4)贮氢合金, 分析测试了铸态及快淬态合金的微观结构与电化学性能, 研究了硼及快淬工艺对合金微观结构及电化学性能的影响. 结果表明, 铸态合金具有双相组织, 主相为CaCu5型相, 还有少量CeCo4B第二相, 第二相的相丰度随硼含量x的增加而增大. 对合金进行了不同淬速的快淬处理, 随淬速的增加, 合金中第二相的量减少. 快淬使合金的晶格参数略有增大. 快淬工艺对合金的电化学性能产生显著影响, 随淬速的增加, 合金的容量下降, 循环稳定性显著提高. 快淬使合金的活化性能降低, 但随着硼含量的增加, 活化性能、高倍率放电能力及放电电压特性均得到不同程度的改善.

Microstructure and Electrochemical Characteristics of Mm(NiCoMnAl)5Bx (x=0～0.4) Hydrogen Storage Alloy Prepared by Cast and Rapid Quenching

Low Co AB_5-type MmNi_(3.8)Co_(0.4)Mn_(0.6)Al_(0.2)B_x (x=0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by cast and rapid quenching. The microstructures and electrochemical performances of the as-cast and quenched alloys were analysed and measured. The effects of boron additive and rapid quenching technique on the microstructures and electrochemical properties of as-cast and quenched alloys were investigated comprehensively. The experimental results show that the microstructure of as-cast MmNi_(3.8)Co_(0.4)Mn_(0.6)Al_(0.2)B_x (x=0, 0.1, 0.2, 0.3, 0.4) alloy is composed of CaCu_5-type main phase and a small amount of CeCo_4B-type secondary phase. The abundance of the secondary phase increases with the increase of boron content x. The rapid quenching technique was used in the preparation of the alloys. The amount of secondary phase in the alloys decreases with the increase of quenching rate. Rapid quenching made lattice constants increase slightly. The effects of rapid quenching on the electrochemical performances of the alloys are very significant. The discharge capacity of the alloys decreases obviously and the cycle stability of the alloys increases dramatically with the increase of quenching rate. Rapid quenching makes the activation performance of the alloys lower. However, the activation performance and high rate discharge capability as well as discharge voltage characteristics of the alloys are modified obviously with the increase of boron content x.