Development of hydrogen-storage alloys of Mg-Fe2O3 system by reactive mechanical grinding

We have improved the H2-sorption properties of Mg by mechanical grinding under H2 (reactive mechanical grinding) with Fe2O3. The sample Mg-10 wt% Fe2O3 prepared by milling at the revolution speed of 250 rpm for 6 h has the best hydrogen-storage properties. It absorbs 3.43 wt% hydrogen at the first cycle at 593 K under 12 bar H2 for 60 min. Its activation is accomplished after three hydriding-dehydriding cycles. The activated sample absorbs 3.32 wt% hydrogen at 593 K, 12 bar H2 for 60 min. The reactive grinding of Mg with Fe2O3 increases the H2-sorption rates by facilitating nucleation (by creating defects on the surface of the Mg particles and by the additive) by making cracks on the surface of Mg particles and reducing the particle size of Mg and thus by shortening the diffusion distances of hydrogen atoms. Hydriding-dehydriding cycling increases the H2-sorption rates by making cracks on the surface of Mg particles and reducing the particle size of Mg. The agglomeration of the particles resulting from the annealing effect during cycling decreases the hydriding and dehydriding rates.