Phase components and hydriding properties of the sintered Mg-xwt.% LaNi5 (x=20-50) composites

Powder mixtures of magnesium and LaNi5 with nominal composition Mg-x wt.% LaNi5 (x=20-50) were pressed into pellets and sintered at 973 K for 1 h. After sintering, it was found that when x=20-40 the major phases were pure Mg, Mg2Ni and La2Mg17, including small amounts of MgO. Further increasing x to 50, Mg,Ni and La,Mg,, remained the major phases but pure magnesium disappeared. In contrast to previously published results, the LaMg12 phase was not found in the above composition range. The phase abundance as a function of composition was quantitatively determined by Rietveld analysis. It was also found that changing the sintering temperature from 723 to 973 K did not change the resultants of the sintered Mg-50 wt.% LaNi5 composite as well as their relative amounts. All samples were easily activated at 623 K, and their pressure-composition isotherms of hydrogenation were measured at 573 K. (C) 1999 Elsevier Science S.A. All rights reserved.