Operating conditions for hydriding combustion synthesis of pure Mg₂NiH₄

To study the relationship between hydrogen pressure and holding time for hydrogenation at 680 K, hydriding combustion synthesis of Mg₂NiH₄ were conducted at different heat patterns and hydrogen pressures. The obtained results were summarized in the form of an operating map, which visualized clearly the possible operating conditions for industrializing the process. Pure Mg₂NiH₄ can be synthesized at a high pressure of hydrogen and a short holding time at 680 K. At a lower pressure of hydrogen such as 0.5 MPa, 7.2 ks of a holding time at 680 K is enough to obtain 100% pure Mg₂NiH₄ as a product. The pressure composition isotherm of Mg₂NiH₄ at 623 K, showed a hydrogen capacity very near the theoretical value of 3.6%, together with a reasonable plateau. The specific surface areas of several samples suggested that the product is a porous material.