Study of Mg-M (M = Co, Ni and Fe) mixture elaborated by reactive mechanical alloying - hydrogen sorption properties

Reactive mechanical alloying (MA in H-2) of magnesium powder allowed us to obtain a partial conversion of Mg to MgH2. The ratio MgH2/Mg can be improved by increasing the milling time or by adding a 3 d-element (with the same initial particle size). X-ray diffraction was applied successfully to determine the quantity of MgH2 formed. The RMA allows us to eliminate the activation procedure generally requested for magnesium. The hydriding results from the combination of two steps: nucleation at first and then diffusion. A direct relationship exists between the nucleation duration and the specific surface area. It is demonstrated that RMA for a short time (2 h) is an effective way to strongly improve the hydrogen storage properties of both magnesium and (Mg + 10 wt.% Co, Ni or Fe) mixtures. (C) 2000 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.