NOTABLE HYDRIDING PROPERTIES OF A NANOSTRUCTURED COMPOSITE-MATERIAL OF THE MG2NI-H SYSTEM SYNTHESIZED BY REACTIVE MECHANICAL GRINDING

The intermetallic compound Mg2Ni was mechanically ground under a hydro gen atmosphere to synthesize a nanostructured composite material that is composed of nanocrystalline intra-grain and disordered inter-grain regions. Both the thermal and magnetic analyses confirmed that a volum e fraction of the latter region increases twenty times as much as that in the initial compound, nearly 30%, by grinding for only 60 min. As a result of this structural modification, notable hydriding properties emerged; the dissolved hydrogen content reaches up to 1.6 wt% (Mg2NiH 1.8) without changing the crystal structure (Mg2Ni type) of the nanocr ystalline intragrain region, and the cooperative dehydriding reaction between both the regions occurs even at 413 K. The hydriding propertie s are most likely reversible in the temperature ranges below 473 K, ab ove which the disordered inter-grain region transforms into a crystall ine phase. Copyright (C) 1996 Acta Metallurgica Inc.