Hydrogen absorption processes in Mg(2)Ni-based systems: Thermal and mechanochemical kinetics

Mg2Ni/Ni and LaMg2Ni alloy powders were exposed to hydrogen under isothermal and
mechanical treatment conditions. In the former case, the amount of hydrogen absorbed
tends with time to a final asymptotic value. Once such a value has been reached, further
hydrogen absorption can be obtained only by submitting the powders to mechanical processing
in the presence of hydrogen. Hydrogen absorption processes under isothermal and
mechanical treatment conditions exhibited different kinetics and their rates have been
compared on a phenomenological basis starting from kinetic evidences. It appeared that
mechanical treatment enhances the rate of hydrogen absorption by four orders of
magnitude as a consequence of a mix of surface area enlargement, temperature rise and local structural excitation processes.