Study on the Reactivity with Hydrogen of Planetary Ball Milled 90 wt% Mg+10 wt% MgH2: Analyses of Reaction Rates with Hydrogen and Microstructure

Much research has been performed on the synthesis of magnesium hydride with added catalysts, leading to the preparation of magnesium hydride with additives. High pressure, high temperature, and long periods are required to prepare a sample with an MgH2 phase without additives. In order to synthesize an additive(s)-free sample with a single MgH2 phase, 90 wt% Mg+10 wt% MgH2 (named 90Mg+10MgH(2)) was milled in a hydrogen atmosphere of 15 bar for 10 h. Hydrogen absorption and release properties of the prepared samples were investigated, and compared with those of a purchased MgH2. A sample whose large fraction is the MgH2 phase was prepared. Particles of 90Mg+10MgH(2) after hydriding-dehydriding cycling have a form of agglomerates consisting of fine particles and have more defects than are present in MgH2 after hydriding-dehydriding cycling. 90Mg+10MgH(2) released 0.06 wt% H for 8 min, 0.40 wt% H for 10 min, 4.66 wt% H for 20 min, 5.54 wt% H for 25 min, 5.62 wt% H for 30 min, 5.64 wt% H for 50 min, and 5.65 wt% H for 60 min at 648 K in the first cycle.