Hydrogen storage properties of Mg-based composites prepared by reaction ball milling

The effect of amount of AB(2) alloy on the hydrogen storage properties of Mg-based composites is investigated. Mg + x wt% Ti0.1Zr0.9Mn0.9V0.1Fe0.5Ni0.5 (x = 5, 15, 25, 30, 35, 40, 50, 60 and 75) composites have been prepared by reaction ball milling Mg with Ti0.1Zr0.9Mn0.9V0.1Fe0.5Ni0.5 and characterized by powder x-ray diffractograms and scanning electron microscopy. Pressure composition absorption isotherms of these composites have been obtained in the pressure range 0.1-30 bar at 300 degrees C using the pressure reduction technique. Maximum storage capacity of around 4.8 wt% at 300 degrees C has been achieved in Mg + 5 wt% Ti0.1Zr0.9Mn0.9V0.1Fe0.5Ni0.5. The dependence of hydrogen absorption plateau pressure on the unit cell volume of Mg phase in these composite materials is discussed. Thermal desorption of hydrogen has been studied using differential scanning calorimetry. Hydrogen absorption/desorption kinetics of these composites have been performed at 300 degrees C, and for Mg + 25 wt% Ti0.1Zr0.9Mn0.9V0.1Fe0.5Ni0.5 kinetics of absorption have been performed in the temperature range 250-325 degrees C. The absorption kinetics data have been analysed using rate equations to understand the mechanism of the hydriding reaction process and to obtain the activation energy.