Preparation and property of magnesium based hydrogen storage alloy hydride Mg₂NiH₄

Magnesium based hydrogen storage alloy hydride Mg₂NiH₄ was prepared by hydriding combustion synthesis (HCS) at the condition of synthesis temperature of 850 K and initial hydrogen pressure of 1.8 MPa, using the uncompressed Mg-Ni mixed powder directly. Phase composition and hydrogen storage property were also investigated by means of X-ray diffraction and pressure composition isotherm. The results indicated that the composition was pure Mg₂NiH₄. The hydriding activity was very high so that it absorbed the saturated amount of hydrogen without any activation process. The kinetic property of hydrogen storage was better than the product of conventional ingot metallurgy at every hydriding temperature, and the amount of hydrogen storage decreased slowly with the decrease of temperature. The relationships between the equilibrium plateau pressure and the temperature were lgP (0.1 MPa)=-3187.6/T+6.3624 for hydriding and lgP (0.1 MPa)=-3468.4/T +6.6943 for dehydriding.