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Magnesium based composites MgH2 + X (X=Ti, Co) were synthesized by ball milling in an argon atmosphere using stainless steel vial and balls. The crystallographic behavior of the resulting powders was examined by XRD. Thermal stability and hydrogen desorption properties were investigated by thermal analysis methods. In order to obtain a deeper insight into bonding mechanisms of the transition metal in MgH2 relaxed structure, ab initio electronic structure calculation of MgH2 + X (X=Ti, Co) was performed using Full Potential Linearized Augmented Plane Wave method, implemented in WIEN2K code. DOS analysis, confirmed by DTA measurements, resulted in the conclusion that, in the composite, in comparison to MgH2, the bonding Mg-H was weakened, on account of the shortening of interatomic distances hydrogentransition metal.

Changes in structural and hydrogen desorption properties of MgH2 induced by ion irradiation have been investigated. MgH2 powder samples have been irradiated with 45 keV B3+ and 120 keV Ar8+ions, with ion fluence of 1015 ions/cm2. The effects of ion irradiation are estimated by numerical calculations using SRIM package. The induced material modifications and their consequences on hydrogen dynamics in the system are investigated by XRD, particle size distribution and TPD techniques. Changes of TPD spectra with irradiation conditions suggest that there are several mechanisms involved in desorption process which depend on defect concentration and their interaction and ordering. The results confirmed that the near-surface area of MgH2 and formation of a substoichiometric MgHx (x<2) play a crucial role in hydrogen kinetics and that various concentrations of induced defects substantially influence H diffusion and desorption kinetics in MgH2. The results also confirm that there is possibility to control the thermodynamic parameters by controlling vacancies concentration in the system

The influence of 3d transition metal addition (Fe, Co and Ni) on the desorption properties of magnesium hydride were studied. The ball milling of MgH2-3d metal blends was performed under Ar. Microstructural and morphological characterization were performed by XRD and SEM analysis, while the hydrogen desorption properties were investigated by DSC. The results show a strong correlation between the morphology and thermal stability of the composites. The complex desorption behavior (the existence of more than one desorption peak) was correlated with the dispersion of the metal additive particles that appear to play the main role in the desorption. The desorption temperature can be reduced by more than 100 degrees if Fe is added as additive. The activation energy for H2 desorption from the MgH2-Fe composite is 120 kJ/mol, implying that diffusion controls the dehydration process