Correlation between microstructural and mechanical behavior of nanostructured MgH2 upon hydrogen cycling

In-situ dilatometry measurements were performed on samples prepared with 2 different additives (pure vanadium or Ti-V-Cr alloy). We systematically observe a stabilization of the irreversible expansion after about 50 cycles. A bi-modal distribution of the as-milled powders is observed by granulometry measurements. Upon cycling, the coalescence of the “small” MgH2 particles tends to create large agglomerates and results in mono-disperse powders. This behavior induces an increase in porosity, which explain the progressive swelling of the composites. The maximum of deformation strongly depends on the additive and is lower with vanadium addition than with Ti-V-Cr alloy.