Tests on mechanically alloyed Mg2Ni for hydrogen storage

Mg2Ni alloy was prepared by mechanical milling followed by annealing at 480 °C under argon atmosphere. The alloy was tested for hydrogen absorption/desorption characteristics on a small sample of 5 g in a laboratory equipment, and for storage properties on a large sample of 375 g in a reactor. Kinetics studies on the small sample showed the same fast absorption at 250–330 °C under 30 bar pressure, and complete desorption at 300–330 °C. Studies were carried out in the temperature range of 200–300 °C with a supply pressure up to 20 bar in the storage device. The large sample showed increase in both absorption rate and storage capacity with supply pressure. However, while storage capacity increased with increase in initial bed temperature, average absorption rate decreased with increase in temperature. At a given bed temperature, absorption kinetics were significantly faster than the desorption kinetics. Maximum hydrogen storage capacity of 3.67 wt%, close to the theoretical limit, was observed in the reactor at a supply pressure of 20 bar and initial bed temperature of 300 °C. The hydrogen storage capacity of the larger mass in the reactor was comparable to the smaller sample mass.