Combinatorial search for hydrogen storage alloys: Mg–Ni and Mg–Ni–Ti

A combinatorial study was carried out for hydrogen storage alloys involving processes similar to those normally used in their fabrication. The study utilized a single sample of combined elemental (or compound) powders which were milled and consolidated into a bulk form and subsequently deformed to heavy strains. The mixture was then subjected to a post annealing treatment, which brings about solid state reactions between the powders, yielding equilibrium phases in the respective alloy system. A sample, comprising the equilibrium phases, was then pulverized and screened for hydrogen storage compositions. X-ray diffraction was used as a screening tool, the sample having been examined both in the as processed and the hydrogenated state. The method was successfully applied to Mg–Ni and Mg–Ni–Ti yielding the well known Mg2Ni as the storage composition. It is concluded that a partitioning of the alloy system into regions of similar solidus temperature would be required to encompass the full spectrum of equilibrium phases.