Abstract
Hydrogen storage by alloys with composition La 2− x Ca x Mg 17 (1.4 ⩽ x ⩽ 1.8) representing a mixture of the phases La 2Mg 17, CaMg 2 and magnesium in various ratios has been investigated. It is found that these alloys have good absorption-desorption characteristics and exhibit the highest hydrogen capacity at the lowest hydriding pressure (5 bar). Prolonged cycling with the alloy La 0.4Ca 1.6Mg 17 has shown an initial decrease in its absorption capacity till the 80–100th cycle, after which it remained constant and fairly high till the 250th hydriding-dehydriding cycle. The desorption characteristics of the alloys under investigation are close to those of single-phase alloys with the same general formula and a high lanthanum content ( x < 0.4) and considerably better than the characteristics of the binary alloy La 2Mg 17. On the basis of electron microscopy studies and data from the literature, an explanation of the peculiarities in the behaviour of the alloys is proposed.
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