AN INVESTIGATION OF THE MECHANICAL-BEHAVIOR OF HYDROGEN STORAGE METAL BEDS ON HYDRIDING AND DEHYDRIDING AND SEVERAL METHODS OF PREVENTING THE DAMAGE OF HYDRIDE CONTAINERS CAUSED BY THE EXPANSION OF HYDROGEN STORAGE METALS

The present authors observed the disintegrating and compacting processes of hydrogen storage materials and measured the variation in density of the hydrogen storage metal beds during hydriding and dehydriding. The variation in the strain of the hydride container wall was measured with strain gauges. The experiments demonstrated that during hydriding and dehydriding high strains were produced in the container wall in vertical hydride containers with MlNi5 (where Ml denotes misch metal rich in lanthanum) beds having large initial bulk densities. These strains increased rapidly and markedly with increasing number of cycles. On the basis of the study of the mechanical behaviour of the bed, the present authors also experimented with several methods of preventing swell damage to hydride containers. The results showed that the strain in the hydride container wall was reduced greatly by mixing MlNi5 powder (-400 mesh) with 6 wt.% silicone oil. Pressed composite pellets composed of powders of 30 wt.% Al and a hydride with a high hydrogen content had a high crack resistance, displaying only a few minute cracks after 1000 hydriding and dehydriding cycles. An MlNi5-polyurethane composite also had high crack resistance owing to its high plasticity but it could not withstand temperatures over 120 °C. © 1987.