Comparison of hydrogen storage properties of Mg–Ni from different preparation methods

In this work, a systematic study on the fabrication of Mg–Ni hydrogen storage materials is presented. Mg–6 wt% Ni base alloys were fabricated by a melting and casting process, and then ball milled by planetary ball milling. As a comparison, a sample of Mg + 6 wt% Ni was also prepared by ball milling pure elemental powders. X-ray diffraction patterns of the cast and ball-milled (BM)-cast samples show the existence of both Mg and Mg2Ni phases, while in the BM-powder sample there are some peaks corresponding to Ni particles. Hydrogen sorption properties of the samples were measured at 200 °C and 250 °C. The thermodynamic behaviour of hydrogenated samples was also investigated by differential scanning calorimetry. The ball-milled samples show enhanced hydrogen sorption properties in comparison with the cast samples, and ball-milling after casting results in superior hydrogen absorption/desorption properties in comparison with the ball-milled powder. Our discussion demonstrates that by ball-milling after casting, the Ni particles can penetrate into the deeper layers of magnesium particles and show a combination of the catalytic roles in terms of both hydrogen dissociation and hydrogen pumping to the interface between the catalyst and the Mg.