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 Y Ni2Al3 addition, mixtures with a nominal content of 1 and 50 wt% of the int ermetallic compound were also investigated. The crystal structure of the YN i4Al 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 composite s significantly improved the kinetics of hydrogen absorption and desorption , whereas YNi5 did not affect the sorption process. An explanation of the r esults obtained, based on the catalytic effect of the YNi4Al and YNi2Al3 in termetallics is proposed. It is shown that a higher intermetallic content o f 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 Scie nce S.A. All rights reserved.