Hydrogen storage characteristics of magnesium mechanically alloyed with YNi5-xAlx (x=0, 1 and 3) intermetallics

The hydrogen sorption properties of the composite materials Mg+10 wt% YNi5-xAlx (x=0, 1 and 3) prepared by ball milling were studied. In the case of YNi2Al3 addition, mixtures with a nominal content of 1 and 50 wt% of the intermetallic compound were also investigated. The crystal structure of the YNi4Al phase was determined (CaCu5 type structure, a=0.4940 nm, c=0.4036 nm). It was established that the presence of YNi4Al or YNi2Al3 in the composites significantly improved the kinetics of hydrogen absorption and desorption, whereas YNi5 did not affect the sorption process. An explanation of the results obtained, based on the catalytic effect of the YNi4Al and YNi2Al3 intermetallics is proposed. It is shown that a higher intermetallic content of the composites is accompanied by: (i) an increase of the initial rate of their hydriding, (ii) a decrease of the maximum hydrogen capacity, and (iii) an increasing of the latent period of dehydriding. (C) 2000 Elsevier Science S.A. All rights reserved.