Structural and hydriding/dehydriding properties of Mg-La-Ni-based composites

In this study, two ternary hydrogen storage composites based on the Mg-La-Ni system were successfully synthesized from the mixture of Mg, La₂Mg₁₇ and Ni powders at the weight ratio of 11:6:3 by combustion synthesis (CS) and hydriding combustion synthesis (HCS), respectively. Then, part of each composite was treated by mechanical milling (MM). The crystal structures and surface morphologies of the composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The composite prepared by CS consisted of Mg, La₂Mg₁₇ and Mg₂Ni phases, while the composite prepared by HCS was composed of Mg, MgH₂, LaH₃, Mg₂NiH₄ and Mg₂NiH_0.3 phases. Compared with the composites prepared by CS, CS + MM and HCS, the composite prepared by HCS + MM exhibited the best hydriding/dehydriding properties. We show that the process of HCS + MM is very effective in preparing Mg-based hydrogen storage materials, which have large hydrogen storage capacity and fast kinetics at lower temperature.