H-sorption in MgH2 nanocomposites containing Fe or Ni with fluorine

Ball milling techniques were used to introduce both fluorine and catalytic transition metals (Fe, Ni) into MgH2 nanograined powders. XRD was carried out to follow the structural evolution upon milling, whereas the thermal stability against H-desorption was investigated by DSC and TG analysis. The latter showed that fluorine additions with the Fe catalyst effectively decrease the desorption temperature to about 500 K. Results on the absorption/desorption kinetics, which was investigated by volumetric techniques, are presented and discussed with respect to both the simultaneous catalytic activity of Fe or Ni with F and the effect of solid-state processes which may occur upon mechanical alloying. (c) 2005 Elsevier B.V. All rights reserved.