Development of hydrogen-storage alloys of Mg– [formula omitted] system by reactive mechanical grinding

Abstract

We have improved the H 2 -sorption properties of Mg by mechanical grinding under H 2 (reactive mechanical grinding) with Fe 2 O 3 . The sample Mg–10 wt% Fe 2 O 3 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 H 2 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 H 2 for 60 min. The reactive grinding of Mg with Fe 2 O 3 increases the H 2 -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 H 2 -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.