Microstructural effects in the hydrogenation kinetics of commercial-type LaNi5 alloy

The influence of amorphous and nanocrystalline microstructures on the H-thermodynamics and kinetics of commercial-type AB5.2 alloys have been investigated. On thermodynamic properties, amorphous phase exhibits a H-capacity reduction as compared to that of polycrystalline alloy. As concerns to kinetic properties, amorphous phase leads to slow kinetics which is controlled by hydrogen diffusion. Nanocrystalline alloy exhibits a slight capacity reduction as compared to polycrystalline which is related to a slopped plateau pressure. H-kinetics of nanocrystalline alloy is faster than both amorphous and polycrystalline alloys. The rate limiting step for the absorption kinetics in nanocrystalline alloy changes during hydrogen uptake from hydrogen diffusion to α/β phase transformation.