Formation of Mg(OH)2 in Mg–Ni–Fe2O3 alloys prepared using reactive mechanical grinding

Nickel and purchased Fe2O3 or Fe2O3 synthesized by spray conversion were added to Mg via reactive mechanical grinding (mechanical grinding in H2). Samples with compositions of 71.5 wt%Mg–23.5 wt%Ni–5 wt%Fe2O3 (purchased) and 71.5 wt%Mg–23.5 wt%Ni–5 wt%Fe2O3 (synthesized by spray conversion) were prepared, and the phase changes in the samples were examined using X-ray diffraction analysis following hydriding–dehydriding cycling, as well as following reactive mechanical grinding. Both samples contained an Mg(OH)2 phase after hydriding–dehydriding cycling, as well as after reactive mechanical grinding. To the best of our knowledge, the formation of Mg(OH)2 phase is not reported in Mg-Ni-Fe2O3 system hydrogen storage materials.