Effects of Nickel and Iron Oxide Addition by Milling under Hydrogen on the Hydrogen-Storage Characteristics of Mg-Based Alloys

Abstract

Samples of pure Mg, 76.5 wt%Mg-23.5 wt%Ni, and 71.5 wt%Mg-23.5 wt%Ni-5 wt%Fe2O3 were prepared by reactive mechanical grinding and their hydriding and dehydriding properties were then investigated. The reactive mechanical grinding of Mg with Ni is considered to facilitate nucleation and to shorten diffusion distances of hydrogen atoms. After hydriding-dehydriding cycling, the 76.5 wt%Mg- 23.5 wt%Ni and 71.5 wt%Mg-23.5 wt%Ni-5 wt%Fe2O3 samples contained Mg2Ni phase. In addition to the effects of the creation of defects and the decrease in particle size, the addition of Ni increases the hydriding and dehydriding rates by the formation of Mg2Ni. Expansion and contraction of the hydride-forming materials (Mg and Mg2Ni) with the hydriding and dehydriding reactions are also considered to increase the hydriding and dehydriding rates of the mixture by forming defects and cracks leading to the fragmentation of particles. The reactive mechanical grinding of Mg-Ni alloy with Fe2O3 is considered to decrease the particle size.