Enhanced gaseous hydrogen storage kinetics of Mg2Ni-type alloys by melt spinning and substituting Ni with Cu

The Mg2Ni-type Mg20Ni10-xCux (x = 0, 1, 2, 3,4) hydrogen storage alloys were prepared by a melt-spinning technology. The structures of the as-cast and spun alloys are characterized by XRD, SEM and TEM. The gaseous hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The results show that all the as-spun alloys hold an entire nanocrystalline structure and are free of amorphous phase. The substitution of Cu for Ni leads to a significant refinement of the grains of the as-cast alloys without changing the major phase Mg2Ni. Both the melt spinning and the substitution of Cu for Ni evidently ameliorate the hydriding and dehydriding kinetics of the alloys. The hydrogen absorption saturation ratio (R-5(a)) and the hydrogen desorption ratio (R-20(d)) of the Cu-2 alloy are enhanced from 56.72 to 92.74% and from 14.89 to 40.37% respectively by rising spinning rate from 0 (as-cast was defined as spinning rate of 0 m/s) to 30 m/s. And those of the as-spun (20 m/s) alloys are increased from 85.99 to 91.22% and from 20.84 to 52.88 respectively by growing Cu content from 0 to 4.