RE-Mg-Ni系A_2B_7型合金的循环稳定性及电化学贮氢动力学

The electrochemical cycle stability and the hydrogen storage kinetics of La-Mg-Ni-based A_2B_7-type alloys

为了改善La-Mg-Ni系A2B7电极合金的电化学循环稳定性,用Zr部分替代合金中的La,并采用熔体快淬技术制备了La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1(x=0,0.05,0.1,0.15,0.2)电极合金.用XRD,TEM分析了合金的微观结构,结果表明,快淬不含Zr合金具有完全的纳米晶结构,而快淬含Zr合金中出现明显的非晶相,证明Zr替代有利于提高合金的非晶形成能力.铸态及快淬态合金均具有多相结构,包括两个主相(La,Mg)2Ni7及LaNi5和残余相LaNi2,Zr替代及快淬导致LaNi5相增加和(La,Mg)2Ni7相减少.Zr替代及快淬处理显著提高了合金的电化学循环稳定性,但快淬明显降低Zr0.2合金的电化学贮氢动力学;随Zr替代量的增加,5 m/s快淬合金的电化学贮氢动力学先增加后降低.

In order to improve the electrochemical cycle stability of the La-Mg-Ni system A2 B7-type electrode alloys, the partial substi- tution of Zr for La has been performed. The La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1 （x = 0, O. 05, 0.1, 0.15, 0.2） electrode alloys were fabricated by casting and melt-spinning. The structure was characterized by XRD and TEM, and the results reveal that the as-spun Zr free alloy displays an entire nanocrystalline structure, but an amorphous structure was detected in the as-spun alloy substituted by Zr, suggesting that the substitution of Zr for La facilitates the amorphous formation. The ascast and spun alloys have a muhiphase struc- ture, composing of two main phases （ La, Mg）2 Ni7 and LaNi5 as well as a residual phase LaNi2 ;the phase abundance of LaNi5 was increased and that of （La, Mg）2 Ni7 was decreased by the substitution of Zr for La. The electrochemical measurement indicates that both the substitution of Zr for La and the melt spinning remarkably ameliorated the electrochemical cycle stability of the alloys, but the melt- spinning treatment decreased the hydrogen storage kinetics of the alloys. The hydrogen storage kinetics of the as-spun （5 m/s） alloys first increased and then decreased by increasing Zr content from 0 to 0.2.