F-TREATMENT EFFECT ON THE INITIAL ACTIVATION CHARACTERISTICS OF MG-LA-NI AMORPHOUS-ALLOYS

Treatment of MgLa1-xNix (x = 0.4-0.7) amorphous alloys with a fluorine -containing aqueous solution leads to a material easily activated unde r moderate conditions. The maximum H-capacity of the F-treated MgLa0.3 Ni0.7 during 10 h activation at 75 degrees C reached about 1.3 in H/M ratio or 2.4 wt.%, three times that of the untreated one. The amorphou s structure and the ribbon shape were maintained after hydrogenation. With increasing temperature, the non-crystalline structure of the amor phous alloy tended to become crystalline, resulting in a decrease of H -capacity. XRD analysis suggested that the initial hydriding of the am orphous alloys caused an irreversible decomposition of the alloys with the formation of LaH3 and of Mg and Mg2Ni hydrides after crystallizat ion. A La-Mg-fluorinated surface with a net-like structure was formed after F-treatment which is believed to play an important role in the r apid hydrogen absorption under such moderate conditions.