SYNTHESIS AND HYDROGEN STORAGE CHARACTERISTICS OF THE COMPOSITE ALLOYLA2MG17-X WT-PERCENT-MMNI4.5AL0.5

Recently, composite type materials consisting of known hydrogen storag e systems e.g. Mg-LaNi5, ZrFeCr-Mg, etc. {[1], H. Nagai et al., J. Les s-Common Metals 157, 15 (1990); [2], H. Fujii et al., J. Less-Common M etals 175, 243 (1991)} have been shown to have better hydrogen absorbi ng/desorbing properties. The present paper reports the synthesis and h ydrogenation/dehydrogenation behaviour of the composite alloy La2Mg17- x wt% MmNi4.5Al0.5. It has been shown that the optimum hydrogen storag e characteristics are possessed by the material with x = 10% i.e. La2M g17-10%. MmNi4.5Al0.5. The hydrogen storage capacity for this material , where effective dehydrogenation occurs at 400-degrees-C, is 4.85%. A lso, the kinetics for the said composite material are much better than La2Mg17 alone. The x = 10 wt% material also has au faster kinetics-ab out 3 times faster than that of La2Mg17 alone. Evidence and arguments have been advanced to show that the improved hydrogenation-storage cap acity and better kinetics of the composite material arise due to the m ultiphase nature of the material (besides the majority phase La2Mg17, other minority phases exist, e.g. MgNi2, Mm3Ni7 and Ni are present).