Abstract
It has recently been shown that Severe Plastic Deformation (SPD) techniques could be used to obtain nanostructured metal hydrides with enhanced hydrogen sorption properties. In this paper we review the different SPD techniques used on metal hydrides and present some specific cases of the effect of cold rolling on the hydrogen storage properties and crystal structure of various types of metal hydrides such as magnesium-based alloys and body centered cubic (BCC) alloys. Results show that generally cold rolling is as effective as ball milling to enhance hydrogen sorption kinetics. However, for some alloys such as TiV0.9Mn1.1 alloy ball milling and cold rolling have detrimental effect on hydrogen capacity. The exact mechanism responsible for the change in hydrogenation properties may not be the same for ball milling and cold rolling. Nevertheless, particle size reduction and texture seems to play a leading role in the hydrogen sorption enhancement of cold rolled metal hydrides.
Highlights
The effects of mechanical deformation on the hydrogen storage behavior of metal hydrides have been intensively studied in the last decade
A common result of high energy Ball Milling (BM) and Severe Plastic Deformation (SPD) and SPD is the formation of nanocrystalline or amorphous structure along with formation of defects and increase of grain boundaries
Absorption kinetic data indicated that the maximum H-absorption capacity was increased by 30–50% after High Pressure Torsion (HPT) due to the creation of new possible hydrogen absorption sites at the grain boundaries and at lattice defects
Summary
The effects of mechanical deformation on the hydrogen storage behavior of metal hydrides have been intensively studied in the last decade. A common result of high energy Ball Milling (BM) and Severe Plastic Deformation (SPD) and SPD is the formation of nanocrystalline or amorphous structure along with formation of defects and increase of grain boundaries. In many systems such structure leads to enhanced mechanical and chemical properties. Defects could act as nucleation point for a chemical reaction (such as hydrogenation) while grain boundaries could act as fast diffusion pathways. These techniques are attractive for synthesis and preparation of metal hydrides materials. Each of these methods will be described and a few specific systems will be discussed by comparing ball milling with SPD techniques
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