Deuterium storage in Mg-Nb films

Microcrystaline Mg film samples containing 5 at.% Nb have been prepared by r.f. magnetron sputtering. Structural analysis suggests that Nb is atomically dispersed in the as deposited Mg lattice. When exposed to H-2 or D-2 gas at 10 atm and 600 K the film samples absorb -7.6 wt.% H-2 indicating a complete h-Mg to beta-MgH2 phase transition. The H-2 desorption from the pure Mg hydride is controlled by the nucleation and growth of the h-Mg phase and occurs with 141 +/- 5 KJ mol(-1) H activation energy and a kinetics order n approximate to 4. The H-2 desorption kinetics from the Nb doped Mg hydride is of order n approximate to I with activation energy value of 52 5 KJ mol(-1) H. It is suggested that Nb impurities catalyse the dissociation of the Mg hydride by reducing the thermodynamic stability of the hydride phase. (c) 2005 Elsevier B.V. All rights reserved.