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Speed-up of thermal decomposition of magnesium hydride due to uniaxial pressing, including pressing in presence of nickel catalyst, was studied by barometry, SEM, DSC, XRD methods, and using mathematical modeling. Pressing even with no catalyst is shown to hasten the hydrogen desorption. The most probable reason for this is the formation of multiple defects in crystal lattice. They can serve as nucleation centers: metal nuclei significantly hasten hydrogen desorption. Besides, metal magnesium not converted to the hydride during the synthesis stage can possibly appear at surface. Adding nickel powder before pressing hastens dehydriding process even more. Comparing hydrogen evolution curves for samples with different amount of nickel allowed to propose the probable mechanism of hydrogen evolution. It is based on description of reactions of hydrogen desorption and hydride decomposition and of the metal-hydride phase morphology change due to these reactions. We develop a mathematical model in form of ordinary differential equations that fits the experimental data well. The model is based on conservation and symmetry assumptions. The fitting allowed to evaluate rate parameters of hydride phase decomposition.

The synthesis procedure of a thin aluminum-hydrogen film on a silicon substrate is described and its result thoroughly investigated by a number of experimental methods. The reactive sputtering deposition was carried out to obtain a structure containing aluminum hydride. The resulting film has characteristic non-metallic properties, though according to thermal desorption studies its hydrogen content is close to AlH1.1, which is lower than stoichiometric aluminum hydride AlH3. Thermal desorption of hydrogen differs significantly from that of AlH3 powder as it has not one but several peaks. According to transmission electron microscopy the film is mostly amorphous but contains crystalline phase. Our interpretation of the experimental data suggests that some hydride phase microcrystals were formed as the film was deposited, but most hydrogen was stored inside the film without forming a crystalline structure in both bounded and unbounded states. The luminescent properties of the synthesized film are similar to aluminum hydride, and it can be concluded that the amorphous Al-H structure of the synthesized film shows resemblance with AlH3 crystals populated with hydrogen vacancies.