Hydrogen storage behaviours of nanocrystalline and amorphous Mg20Ni10-xCox (x=0-4) alloys prepared by melt spinning

The Mg2Ni-type alloys with nominal compositions of Mg20Ni10-xCox (x=0, 1, 2, 3, 4, %, mass fraction) were prepared by melt-spinning technology. The structures of the alloys were studied by XRD, SEM and HRTEM. The hydrogen absorption/desorption kinetics and the electrochemical performances of the alloys were measured. The results show that no amorphous phase forms in the as-spun Co-free alloy, but the as-spun alloys containing Co show a certain amount of amorphous phase. The hydrogen absorption capacities of the as-cast alloys first increase and then decrease with the incremental change of Co content. The hydrogen desorption capacities of as-cast and spun alloys rise with increasing Co content. The melt spinning significantly improves the hydrogenation and dehydrogenation capacities and kinetics of the alloys. The substitution of Co for Ni clearly enhances the discharge capacities of the alloys and the cycle stability of the as-spun alloys.