Hydrogen storage properties of Mg-based composites prepared by reaction ballmilling

Abstract

The effect of amount of AB2 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 withTi0.1Zr0.9Mn0.9V0.1Fe0.5Ni0.5 andcharacterized by powder x-ray diffractograms and scanning electron microscopy. Pressure–compositionabsorption isotherms of these composites have been obtained in the pressure range 0.1–30 bar at300 °C using the pressure reduction technique. Maximum storage capacity of around 4.8 wt% at300 °C has beenachieved in Mg + 5 wt% Ti0.1Zr0.9Mn0.9V0.1Fe0.5Ni0.5. The dependence of hydrogen absorption plateau pressure on the unit cell volumeof Mg phase in these composite materials is discussed. Thermal desorption ofhydrogen has been studied using differential scanning calorimetry. Hydrogenabsorption/desorption kinetics of these composites have been performed at300 °C, andfor Mg + 25 wt% Ti0.1Zr0.9Mn0.9V0.1Fe0.5Ni0.5 kinetics of absorption have been performed in the temperature range250–325 °C. The absorption kinetics data have been analysed using rate equations to understand themechanism of the hydriding reaction process and to obtain the activation energy.