Activation mechanism of hydrogen-storage electrode alloy Ml(NiCoMnTi)5 produced by gas atomization

Electrochemical activation behaviour of hydrogen-storage alloy Ml(NiCoMnTi)(5) produced by conventional induction melting (CIM) and by Ar gas atomization (AGA) has been studied. It has been found that the surface oxide layer plays a minor part, while the change of energy inside alloy before and after hydriding is the major factor affecting the behaviour of activation. The larger the change of energy inside the alloy or the strain energy caused by H-atoms entering tetrahedral and octahedral sites during hydriding, the more difficult is the activation. The effect of surface oxide him on the activation could to be considered as the oxide film causing the energy of H-atoms entering the alloy to be increased, since H-atoms must consume some energy to break the surface oxide film initially, before entering the alloy. (C) 1997 International Association for Hydrogen Energy.