The effects of dynamic structural transformations on hydrogenation properties of Mg and MgNi thin films

Mg capped with Al and Ti thin layers and MgxNi films have been sputter-deposited on quartz substrates and hydrogenated at 600 kPa for 250 °C. A complete fast transformation of metallic into hydride phase is registered for the films, demonstrating the dynamic state of the internal microstructure under hydrogenation. It leads to local and long-range restructuring and the fast hydrogenation rate is attributed to the fast hydrogen uptake and transport along columns and grain boundaries of nanocrystallites. A slow H-loading is observed when the dynamic structural relaxation processes are suppressed by internal and external inhomogeneities such as barrier layers on the surface, new phases in the bulk and impurities. A partial transformation of metallic into hydride phase is registered when the structural formations newly nucleated at the initial stages of hydrogenation suppress dynamic processes and prevent the H-uptake.