Investigation of hydride powder bed swelling and shrinking during hydrogen absorption/desorption cycles under different compressive stresses

The solid storage through hydrides allows good compactness and safety due to low pressure. Intermetallic hydride materials have a significant volume increase and decrease (10–35%) upon absorption/desorption respectively. The measurement of the mechanical behavior of these materials is of major interest for the design of H2 storage tanks. In the present work, Ti–V–Cr hydride powder beds underwent hydrogen absorption/desorption cycles in a cylindrical instrumented cell with a mobile upper piston. Different compressive stresses have been applied by the piston and a spring on the powder bed. The variations of samples volume were measured upon cycling and analyzed while considering the mechanical behavior of this granular medium. In particular, part of the volume change is balanced by the variation of the intergranular porosity of the granular media. Changing upper stress reveals the combined importance of the powder sample friction on the cell side walls, and of internal friction strongly influenced by the grains interlocking in the cyclic powder densification process observed.

► Decrepitation creates hydride bed densification while cycling under hydrogen.
► Axial compressive stress decreases the ability of a hydride bed to change its volume.
► Internal friction increases along with cycles.
► Friction of the hydride with the side walls increases the powder density.