International Journal of Hydrogen Energy, Vol.34, No.12, 5131-5137, 2009
The effects of dynamic structural transformations on hydrogenation properties of Mg and MgNi thin films
Mg capped with Al and Ti thin layers and Mg Ni films have been sputter-deposited on quartz substrates and hydrogenated at 600 kPa for 250 degrees 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. (c) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.