New composite materials for hydrogen storage using magnesium as a binder

We have developed new composite materials for hydrogen storage containing ZrFe_1.4Cr_0.6 or TiMn_1.5 as a storage material and magnesium as a binder. The influences of composition, compacting pressure and heat treatment on hydrogen capacity, kinetics and cyclic durability of the composite pellets were examined by repeating absorption-desorption cycles. The pellets obtained by sintering the mixtures at 773 K for 20-40 h absorb hydrogen readily and very quickly under a hydrogen pressure of less than 1 MPa without any activation treatment, and exhibit no disintegration after 1000 hydriding-dehydriding cycles. Observations of the microstructure and distribution of metals and oxygen atoms in the composites, using scanning electron microscopy, electron probe microanalysis and electron spectroscopy for chemical analysis, indicate that the heat treatment at 773 K not only promotes the so-called magnesium reduction and makes the surface of the hydride clean, but it also helps to form a new thin composite phase on the boundary between the original hydride and unreacting magnesium metal which acts as a binder, keeping the pellet intact upon hydrogenation.