Enhanced Hydrogen Storage Kinetics of Melt Spun Nanocrystalline and Amorphous Mg<sub>2</sub>Ni-Type Alloy by Substituting Ni with Co

Abstract

The nanocrystalline and amorphous Mg2Ni1-xCox (x=0, 0.1, 0.2, 0.3, 0.4) alloys were prepared by melt-spinning technique. The structures of the alloys were studied by XRD, SEM and HRTEM. The hydrogen absorption and desorption kinetics and the high rate discharge ability (HRD) of the alloys were measured. The results show that the as-spun Co-free alloy holds a typical nanocrystalline structure, whereas the as-spun alloys containing Co display a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni facilitates the glass formation in the Mg2Ni-type alloy. The substitution of Co for Ni evidently improves the hydriding and dehydriding kinetics and the HRD of the alloys. With an increase in the amount of Co substitution from 0 to 0.4, the HRD value rises from 52.9% to 60.3% for the as-cast alloy, and from 65.9% to 76.0% for the as-spun (30 m/s) alloy.