Preparation of Mg2Ni Hydrogen Storage Alloy Materials with Mg-Coated Structure by Mechanical Alloying

Abstract

In this paper, a hydrogen storage alloy material with good hydrogen storage performance, high preparation efficiency and a partially amorphous magnesium-coated Mg2Ni structure was prepared by high-energy ball milling mechanical alloying. The effects of different Mg and Ni mass ratios and ball milling speed on their synthesis were investigated. The results show that compared with the Mg2Ni alloy, the thermodynamic and kinetic properties of the hydrogen storage alloy material change less, but the hydrogen storage capacity increases significantly. In the case of different Mg and Ni mass ratios, the formation time of Mg2Ni alloys is not much different, the obtained particle sizes are all about 5 μm, and the hydrogen storage capacity increases with the increase of mass ratio. However, the formation of Mg2Ni alloy varies greatly at different rotational speeds. At low rotational speed, the formation of Mg2Ni alloy is incomplete or not, and the rotational speed for complete formation of Mg2Ni alloy is 1000/1100 rpm. Through SEM and XRD analysis, it is found that the particle size of the alloy after ball milling is small, and the alloy composition is uniform, which is one of the reasons for the better hydrogen storage performance of the alloy. And it can be seen that the alloy with extremely high phase purity can be obtained by ball milling for 5 h. Through TEM, Mapping and PCT curves combined with XRD analysis, it is found that the particles after ball milling have a structure of partially amorphous Mg-coated Mg2Ni alloy, and the hydrogen storage capacity of the alloy reaches 5 wt%. This is another reason for the two-stage plateau pressure and better hydrogen storage performance. Therefore, the Mg2Ni alloy obtained by the high-energy ball milling mechanical alloying method in this paper has a 90% increase in efficiency compared with the traditional mechanical alloying method; and compared with the melting method, the hydrogen storage performance is also improved.