Effects of nanometer-scale structure on hydriding properties of Mg-Ni alloys: A review

The materials, which are produced by mechanical grinding/alloying, possess superior hydriding properties depending on their nanometer-scale structures. In this review paper, we present our recent works on the hydriding properties and nanometer-scale structures of some mechanically produced Mg-Ni alloys. The first topic is the properties of some nanostructured Mg₂Ni (Mg-33 at%Ni) consisting of nanometer-scale crystallite (intra-grain) and inter-grain regions. In this system, the existence of the inter-grain region gives rise to notable hydriding properties of the nanostructured Mg₂Ni such as the enhanced hydrogen dissolution and low-temperature dehydriding. The second topic is the properties of the alloys Mg-33, 38, 43 and 50 at% Ni in which a different amount of the amorphous (a-)MgNi phase depending on Ni content is homogeneously dispersed around nanometer-scale Mg₂Ni crystallites. In this system, the total hydrogen content increases with increasing Ni content. This experimental result is well explained by a model based on three nanostructural constituents of these alloys and their hydriding properties.