Mechanisms for Activation of Intermetallic Hydrogen Absorbers

As far as ease of activation is concerned, the H absorbing intermetallic compounds divide, roughly, into two groups: FeTi, some ternary variants of FeTi and other Ti/transition-metal compounds, for which significantly troublesome activation processes are necessary; and most of the other intermetallics, for which a rather modest acitvation procedure is required, the paradigm of these being also one of the originals: LaNi sub 5 . For the concomitant problem of resistance to "poisoning" of the H being absorbed, another two groups could be formed: the LaNi sub 5 family, and particularly LaNi sub 5 in one group; and, on the basis of the rather incomplete information presently available, all the rest of the intermetallics in the other group. For the elemental metals, another two groups can be formed, with Pd the sole member of one, and the rest, although this again could be altered by better information (e.g. the case of La), forming the other group. As far as the models of activation behaviour are concerned, progress made so far has reached the point where a need for new beginnings is indicated for many, and perhaps all, of the intermetallic compounds. 86 ref.--AA