Hydrogen storage properties of the mechanically milled MgH2-V nanocomposite

In this paper we present the hydrogen storage properties of a new composite MgH2 +V prepared by ball milling. Intensive milling of magnesium hydride w ith vanadium produces a nanocomposite of beta-MgH2+gamma-MgH2 +VH0.81. The MgH2+5 at.% V composite produced by mechanical milling can desorb hydrogen at 473 K under vacuum and re-absorb hydrogen rapidly even at room temperatu re. The activation energy of hydrogen desorption was measured to be 62 kJ m ol(-1) H-2. The fast kinetics of the ball milled MgH2-V composite primarily comes from the catalytic effect of vanadium and the small powder size. The formation enthalpy and entropy of the composite are identical to that of p ure magnesium. (C) 1999 Elsevier Science S.A. All rights reserved.