Abstract
This paper reports the effect of high-pressure torsion (HPT) on the first hydrogenation of LaNi5. We found that, for loose powder, reduction of particle size has an effect of increasing the incubation time and decreasing the hydrogen capacity. A higher amount of HPT turns only marginally reduce the incubation time but has no effect on hydrogen capacity. In all cases, the first dehydrogenation and subsequent hydrogenation have the same kinetics, irrespective of the particle size or number of HPT turns. Therefore, for LaNi5, HPT has a beneficial effect only for the first hydrogenation.
Highlights
Hydrogen is a key energy vector, especially for renewable energies
Desorption at 100 kPa is more suitable for practical applications, but for testing the effectiveness of high-pressure torsion (HPT) on sorption properties, we found that working at 5 kPa permitted faster kinetics and easier comparison
We found that HPT leads to the reduction of the crystallite size, but most of the effect was due to the first turn
Summary
Hydrogen is a key energy vector, especially for renewable energies. For a broad utilization of hydrogen, a suitable means of storage should be available. It is important to realize that cost should include the raw materials and the synthesis process of the hydride It is a common feature of metal hydrides that the first hydrogenation ( called activation) of the as-synthesized alloy is difficult, needing high temperature and hydrogen pressure [14,15]. In the synthesis of materials by HPT, a high shear strain could be reached, resulting in nanostructured alloys with high density of lattice defects, which can improve the hydrogen diffusion and would be beneficial to improving the hydrogen activation of metal hydrides [10,19,20]. By performing the same investigation with HPT, we want to explore the effect of high strain on the first hydrogenation of LaNi5
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