The addition of an oxide Fe2O3 is considered to increase the hydriding rate of Mg by pulverization, and the addition of Ni to increase the hydriding and dehydriding rates by the formation Of Mg2Ni hydride. The sample Mg-10 wt.% (Fe2O3, Ni) was prepared by grinding Mg mechanically under H, (reactive mechanical grinding) with nano-structured Fe2O3 particles and Ni. The as-milled sample absorbed 4.24 wt.% hydrogen at 593 K under 12 bar H-2 for 60 min. Its activation was accomplished after two hydriding-dehydriding cycles. The activated sample absorbed 4.05 wt.% hydrogen at 593 K, 12 bar H-2 for 60 min and desorbed 3.05 wt.% hydrogen at 593 K, 1.0 bar H-2 for 60 min. After hydriding-dehydriding cycling, Mg2Ni is formed by the reaction of Mg with Ni, Fe2O3 is reduced, and a small fraction of Mg is oxidized. (c) 2006 Elsevier Ltd. All rights reserved.