Pressure-composition-temperature properties of hydriding combustion-synthesized Mg₂NiH₄

Pure Mg₂NiH₄ was first prepared by Hydriding Combustion Synthesis (HCS), under which pressure and temperature were sensitively controlled. The purpose of this paper was to study "Pressure-Composition-Temperature (PCT)" properties of the HCSed product, in which hydrogen storage capacity, hydriding reaction rate, and PCT curves were mainly examined, in comparison to the commercially available product, i.e., Ingot Metallurgy product. The results showed that the HCSed Mg₂NiH₄ has 3.6 mass%, same as theoretical value, in hydrogen storage capacity in the first cycle just after synthesized without activation treatment, and very large reaction rate; only five minutes for full charge. Plateau pressure of the HCSed Mg₂NiH₄ in PCT curves also became relatively lower than the conventional one. One of the most interesting results is the high activity of our product: it stored hydrogen even at room temperature. These results appealed a possibility of new productive process of hydrogen storage alloy from the viewpoint of product property.