(203d) Hydrogen Storage Properties of the Mg-Ti-H System Prepared by High-Energy-High-Pressure Reactive Milling

For hydrogen storage and fuel cell applications, magnesium-based alloys are among the most promising materials due to their high hydrogen content. In the present work, we investigated the hydrogen release/uptake properties of the Mg-Ti-H system. Samples were made from mixtures of MgH2 and TiH2 in molar ratios of 7 : 1 and 4 : 1 using a DP-HEHPM (Dual Planetary-High Energy High Pressure Mill) under 2000 psi hydrogen pressure. Thermogravimetric analysis (TGA) showed that a large amount of hydrogen (5.91 and 4.82 wt. %, respectively, for the above two samples) was released between 126 and 313°C while temperature was increased at a heating rate of 5°C/min under an argon flow. The temperature at which hydrogen release starts, 126°C, is much lower than that for MgH2 alone, which is 381°C. By fitting the rate curves at various heating rates, the activation energy of dehydrogenation was obtained to be 71 kJ/mol, which is much smaller than that of as-received MgH2 (153 kJ/mol) or high energy high pressure milled MgH2 (96 kJ/mol). In addition, over short dehydrogenation and rehydrogenation cycles, the hydrogen capacity and the starting hydrogen release temperature remained largely unchanged.