Numerical simulation of intrinsic absorption and desorption kinetics for Mg-3Ni-2MnO₂ hydrogen storage materials

Mg-3Ni-2MnO₂ hydrides are prepared by mechanical alloying under hydrogen atmosphere, and the absorption and desorption kinetics properties are measured. Intrinsic absorption and desorption equations are developed and calculated. The results show that these materials of excellent kinetics properties can be fabricated, and the absorption can be finished in 65 s at 200°C and 2.5 MPa, and the hydrogen absorption capacity is 6.23% (mass); the desorption can be finished in 550 s at 300°C and 0.1 MPa. An Avrami index of about 0.5 indicates that the main process is the growth of discal hydride along the direction of thickness for absorption; the materials behave the character of nucleation and growth for desorption; the new phase grows steadily (no new crystal nucleus appears) according to the Avrami index. The calculated values agree well with the experimental values; the temperature and pressure have effects on the intrinsic kinetic properties.