Thermal stability and hydrogen sorption properties of the mgh2 hydride derived by the reactive milling of the mg + 10 wt% ti mixture

Abstract

Thermal stability and hydrogen sorption properties of the MgH2 phase derived by the reactive milling of the Mg + 10 wt% Ti mixture was studied by the thermodesorption spectroscopy method during the first five cycles of hydrogen sorption-desorption. The addition of Ti decreases decomposition temperature of MgH2 by 115 K, if we conclude about decomposition temperature taking into account peaks of speed of a hydrogen release on the desorption spectra derived during the first cycle of heating-cooling in hydrogen atmosphere of the Mg + 10 wt% Ti mechanical alloy. During the second cycle of dehydriding-hydriding, the decomposition temperature of the MgH2 phase of the Mg + 10 wt% Ti composite decreases additionally by 35 K, and the temperature does not change for three following sorption-desorption cycles. It has been established the influence of the method of synthesis of the hydride phase MgH2 upon location sites of hydrogen in the phase, and, consequently, upon its decomposition temperature. The addition of titanium to magnesium increases the effect of the above influence and promotes increasing the process of dispersion of magnesium and the MgH2 hydride synthesized due to the reactive milling. Additionally, the addition of titanium promotes decreasing the quantity of oxygen-containing structures, catalytic poisons preventing dissociative hydrogen chemosorption, adsorbed on the surface of MgH2 particles.