Hydrogen storage performance of mechanical Mg₂Ni alloy evaluated with a high-pressure microbalance

Mechanical ball-milling was used to prepare Mg₂Ni alloy powder. Effects of milling time (5-20 h) on the crystal structure and morphology were studied with an X-ray diffractomcter (XRD) and a scanning electron microscope (SEM), respectively. The hydrogenation properties, which included storage capacity and absorption rate, of the prepared alloys were evaluated using a microbalance under a hydrogen pressure of 20 bar at 573 K. The experimental results indicated that prolonging the milling time caused the reduction both in the particle size and crystal size of the synthesized Mg₂Ni alloy powder, and thus improve the hydrogen uptake performance. The optimum hydrogen storage capacity found in this study was 2.89 wt% for the 20 h ball-milled Mg₂Ni alloy powder. A complete phase transformation from Mg₂Ni to Mg₂NiH₄ upon hydrogenation was recognized.