Characterization of an MgH2-Ni Alloy Prepared by Mechanical Grinding under Hydrogen

MgH2, rather than Mg, was employed as a starting material in this work. A sample with a composition of 82 wt% MgH2-18 wt% Ni (designated MgH2-18Ni) was prepared by reactive mechanical grinding. Its hydriding and dehydriding properties were then examined. An MgH2-Ni hydrogen-storage alloy that does not require an activation process was developed. The alloy was prepared by grinding for 4 h in a planetary ball mill at a ball disc revolution speed of 250 rpm under a hydrogen pressure of about 12 bar. The sample absorbed 3.51 wt% H for 5 min and 3.96 wt% H for 60 min at 573 K under 12 bar H2, and desorbed 0.90 wt% H for 10 min and 3.24 wt% H for 60 min at 573 K under 1.0 bar H2. MgH2-18Ni after reactive mechanical grinding contained β-MgH2, Ni, γ-MgH2 (a high-pressure form of MgH2), and a very small amount of MgO. The specific surface area and average particle size of MgH2-18Ni after reactive mechanical grinding were analyzed.