Hydriding and Dehydriding Kinetics of Nanocrystalline and Amorphous Mg<sub>20</sub>Ni<sub>10-x</sub>M<sub>x</sub> (M=Cu, Mn; x = 0-4) Alloys Prepared by Melt Spinning

Abstract

The partial substitution of M (M=Cu, Mn) for Ni has been performed in order to ameliorate the hydriding and dehydriding kinetics of Mg2Ni-type hydrogen storage alloys. The melt spinning technology was used to prepare the Mg20Ni10-xMx (M=Cu, Mn; x=0, 1, 2, 3, 4) alloys. The structures of the as-spun alloys were characterized by XRD and TEM. The hydriding and dehydriding kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The results show that the as-spun (M=Cu) alloys hold a typical nanocrystalline structure, whereas the as-spun (M=Mn) alloys display a nanocrystalline and amorphous structure, confirming that the substitution of Mn for Ni facilitates the glass formation in the Mg2Ni-type alloy. Furthermore, Mn substitution results in the formation of the secondary phases MnNi and Mg instead of changing the major phase of Mg2Ni. The substitution of M (M=Cu, Mn) for Ni exerts an insignificant effect on the hydriding kinetics, but it ameliorates the hydrogen desorption kinetics of the alloys dramatically. The hydrogen desorption ratio ( ) is enhanced form 20.84% to 52.88% for the (M=Cu) alloy spun at 20 m/s, and from 20.84% to 53.87% for the (M=Mn) alloy spun at 20 m/s by increasing the M (M=Cu, Mn) content from 0 to 4.