HYDROGENATION PROPERTIES OF MG-BASED LAVES PHASE ALLOYS

MgNi2 and MgCu2 do not form hydrides under conventional hydrogenation conditions. It is assumed that hydrogenation does not occur because th e enthalpy of formation of the hydride phase is large and positive. Us ing Miedema's rule, we calculated the enthalpy of formation of substit uted alloys based on these two compounds. For certain alloys, the enth alpy of formation is 10-20 kJ mol(-1) lower. We synthesized alloys wit h the above calculation as a guide, however no hydride was formed unde r the conditions used, 4 MPa at 573 K. The size of the interstitial ho les compared to the hydrogen atomic size explains these results. (C) 1 998 Published by Elsevier Science S.A.