Effects of nickel and indium ternary additions on the hydrogenation of MgAl intermetallic compounds

Alloying small amounts (2-3 wt%) of Ni and In with MgAl intermetallics causes a significant increase in the hydrogenation rates of these compounds. The catalitic effects of these ternary additions are accounted for by two mechanisms: (a) The formation of surface locations enriched with the ternary constituent which provide preferred dissociation sites for hydrogen and (b) More extensive cracking of the reacting particles during repeated hygrogenation-dehydrogenation cycles. The hydrogenation reaction of both, binary and ternary MgAl β-phase alloys, has been found to follow a law of a three dimensional diffusion through a growing product layer. The thermodynamic parameters associated with the hydrogenation reaction of the MgAl compounds, are evaluated.