Enhanced volumetric hydrogen density in sodium alanate by compaction

Abstract

Powder compaction is a potential process for the enhancement of the volumetric and gravimetric capacities of hydrogen storage systems based on metal hydrides. This paper presents the hydrogen absorption and desorption behaviour of compacts of sodium alanate material prepared under different levels of compaction pressure. It is shown that even at high compaction levels and low initial porosities, hydrogen absorption and desorption kinetics can proceed comparatively fast in compacted material. Furthermore, experimental hydrogen weight capacities of compacted material are higher than the experimental values obtained in case of loose powder. It is demonstrated that the kinetic behaviour of the compacted material during cycling is directly associated to the volumetric expansion of the compact, which is quantitatively measured and analyzed during both hydrogen absorption and desorption processes. The cycling behaviour and dimensional changes of compacted sodium alanate material are a key consideration point if it is used as hydrogen storage materials in practical tank systems.