Methods for studies of hydrogen–sorption properties of metal hydrides as well as of the electronic structure and surface chemical state of ТіН1.88, AlH3 and MgH2 have been elaborated; X-ray emission Ti L and Mg K spectra in the hydrides were derived using an X-ray soft-wave spectrometer-monochromator. Correlation between thermal stability of hydrides of the AB2 intermetallic compounds and the ionic component of their metal-hydrogen bonds has been established. Electronic structure of nonstoichiometric hydride-forming Zr3V3Ox (x = 0.5 and 1.0) and Ti4Fe2Ox (x = 0.25, 0.5 and 1.0) compounds have been studied and the dependence of the core-level binding energies of constituent atoms upon content of oxygen atoms Ti4Fe2Ox has been investigated.
Influence of Ti alloying on hydrogen-sorption properties and decomposition temperature of MgH2 in mechanical alloy Mg +(5 and 10 %wt.Ti) derived in hydrogen medium at pressure 1.2 МPа has been studied. Application of reactive milling allowed decreasing up to 130 oC the temperature of the beginning of MgH2 decomposition in hydrogen medium at Р = 0.1 MPa. The dependence of thermal stability of the hydride phase upon its dispersion degree has been established. It has been shown that, high-energy milling TiH1.9 powder leads to decreasing the enthalpy of hydride formation from 248 kJ/mole Н2 to 172 kJ/mole Н2. The presence of Ti speeds the dispersion process and benefits decreasing quantity of oxygen-containing groups presented on the sample surface. These groups blockade catalyst centers and prevent dissociative Н2 chemosorption. Isobars of thermodesorption in the region of the γ- and β-phases of the Ті – Н system at pressures higher than atmospheric (1.0, 2.5, 3.15 and 4.5 atm) in a reactor have been derived for the first time.
Influence of mechanical dispersion upon thermal stability of magnesium dihydride synthesized either by direct hydriding from gaseous phase or by mechanical alloying has been investigated. The hydride powder undergone to high-energy 20 min influence reveals significant redistribution of hydrogen on the places of its stable being in the lattice of disperse hydride and decreasing thermal stability of the hydride. Dependence of thermal decomposition of the hydride phase upon time of its exposure to air has been established. It has been shown a significant role of the surface in decrease of decomposition temperature of MgH2 (the decrease is caused by hydride dispersion). Such a surface is more stable with respect to catalyst poisoning and it provides increasing thermal stability at long exposure to air.
The process of direct hydriding a titanium rod in a metal capillary after thermal activation at low temperature-low pressure conditions has been investigated. New approach for direct hydriding a Ti rod in the mention conditions has been developed.
Keywords: X-ray absorption spectroscopy, thermodesorption spectroscopy, hydrogen sorption, metal-hydrogen bonds, thermal stability