Synthesis and hydrogen storage characteristics of the composite alloy La2Mg17-x wt% MmNi4.5Al0.5

Abstract

Recently, composite type materials consisting of known hydrogen storage systems e.g. Mg-LaNi5, ZrFeCr-Mg, etc. 1, H. Nagai et al., J. Less-Common Metals 157, 15 (1990); [2], H. Fujii et al., J. Less-Common Metals 175, 243 (1991) have been shown to have better hydrogen absorbing/desorbing properties. The present paper reports the synthesis and hydrogenation/dehydrogenation behaviour of the composite alloy La2Mg17-x wt% MmNi4.5Al0.5. It has been shown that the optimum hydrogen storage characteristics are possessed by the material with x = 10% i.e. La2Mg17-10% MmNi4.5Al0.5. The hydrogen storage capacity for this material, where effective dehydrogenation occurs at 400°C, is 4.85%. Also, the kinetics for the said composite material are much better than La2Mg17 alone. The x = 10 wt% material also has a faster kinetics-about 3 times faster than that of La2Mg17 alone. Evidence and arguments have been advanced to show that the improved hydrogenation-storage capacity and better kinetics of the composite material arise due to the multiphase nature of the material (besides the majority phase La2Mg17, other minority phases exist, e.g. MgNi2, Mm2Ni7 and Ni are present). © 1993.