M(M=Sm,Nd,Pr)替代La对A_2B_7型贮氢合金电化学性能的影响(英文)

Effects of substituting La with M(M=Sm, Nd, Pr) on electrochemical hydrogen storage characteristics of A_2B_7-type electrode alloys

采用M(M=Sm,Nd,Pr)部分替代La,用合金熔炼及退火的方法制备La0.8–xMxMg0.2Ni3.35Al0.1Si0.05(M=Sm,Nd,Pr;x=0–0.4)电极合金,以提高RE–Mg–Ni系A2B7型贮氢合金的电化学性能。用X射线衍射(XRD)及扫描电子显微镜(SEM)分析合金的相组成和显微结构。结果表明,合金由六方结构Ce2Ni7型的(La,Mg)2Ni7相与六方结构Ca Cu5型的La Ni5相组成。随着M替换量的增加,铸态及退火态合金的放电容量均出现最大值。铸态及退火态合金的循环稳定性均随着M替换量的增加而增加。此外,合金的电化学动力学性能(包括高倍率放电性能、电荷传递速率、极限电流密度、氢扩散系数)均随着M替换量的增加呈现先上升后下降的趋势。

The partial substitution of M （M=Sm, Nd, Pr） for La was performed in order to ameliorate the electrochemical hydrogen storage performance of RE–Mg–Ni-based A2B7-type electrode alloys. The La0.8–xMxMg0.2Ni3.35Al0.1Si0.05 （M=Sm, Nd, Pr;x=0-0.4） electrode alloys were fabricated by casting and annealing and their microstructures were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The major phases （La, Mg）2Ni7 with the hexagonal Ce2Ni7-type structure and LaNi5 with the hexagonal CaCu5-type structure make up the basic microstructure of the experimental alloys. The discharge capacities of the as-cast and annealed alloys all gain their maximum values with the M （M=Sm, Nd, Pr） content varying. The electrochemical cycle stability of the as-cast and annealed alloys clearly rises with the M （M=Sm, Nd, Pr） content growing. Furthermore, the electrochemical kinetics of the alloys, including the high rate discharge ability, charge transfer rate, limiting current density and hydrogen diffusion coefficient, all present a increase trend at first and then decrease with the rising of M （M=Sm, Nd, Pr） content.