Hydrogen Absorption and Release Properties of MgH2, Mg2Ni, and Ni-Added Mg via Reactive Mechanical Grinding

In this work, MgH2, Mg2Ni, and Ni were added to Mg in order to improve the hydrogen-storage properties of Mg. A 84 wt% Mg + 10 wt% MgH2 + 5 wt% Mg2Ni + 1 wt% Ni sample (designated the Mg-based sample) was prepared by milling under a hydrogen atmosphere in a planetary ball mill for 5 h. The hydrogen absorption and release properties of the prepared sample were investigated and compared with those of a 94 wt% MgH2 + 5 wt% Mg2Ni + 1 wt% Ni sample (the MgH2-based sample). The Mg-based sample had larger quantities of hydrogen absorbed and released for 60 min than the MgH2-based sample. The Mg-based sample had an effective hydrogen-storage capacity (the quantity of hydrogen absorbed for 60 min) of near 5.7 wt%. At n = 2, the Mg-based sample absorbed 5.18 wt% for 2 min, 5.57 wt% for 10 min, and 5.67 wt% for 60 min at 648 K. At n = 1, the Mg-based sample released 0.083 wt% for 2 min, 5.13 wt% for 10 min, and 5.49 wt% for 60 min at 648 K. The addition of MgH2, Mg2Ni, and Ni to Mg had stronger effects than the addition of Mg2Ni and Ni to MgH2. It is believed that the effects of the reactive mechanical grinding (reducing the Mg particle size, making clean surfaces, and creating defects) are stronger in the Mg-based sample than in the MgH2-based sample. (Received August 16, 2017; Accepted September 29, 2017)