Synergy of hydrogen sorption in ball-milled hydrides of Mg and Mg2Ni

A remarkable enhancement of hydrogen desorption kinetics has been found for magnesium-based materials, ball-milled in the hydrogenated state. Ball-mil ling has been used to introduce both strain and structural changes in the h ydrides of Mg, Mg2Ni and their mixtures, facilitating desorption of hydroge n and reducing the operational desorption temperature. Moreover, ball-milli ng of the mixtures of MgH2 and Mg2NiH4 results in a synergetic effect of de sorption, allowing the mixture to operate at temperatures of 220 degrees C- 240 degrees C, with excellent absorption/desorption kinetics and with total hydrogen capacity exceeding 5 wt.%. This behaviour has been maintained ove r hydrogenation cycling. It is concluded that mechanically-treated hydrides offer a new opportunity for magnesium-based materials, exploiting the high capacity of magnesium hydride while operating at much lower temperature th an conventional MgH2. (C) 1999 Published by Elsevier Science S.A. All right s reserved.