Hydrogen absorption/desorption performance of MgAl alloys synthesized by reactive mechanical milling and hydrogen pulverization

This paper presents a method to fabricate nanoscale alloy powders for hydrogen storage using reactive mechanical milling combined with hydrogen pulverization. The method reduced particle agglomeration and the problem of oxidation associated with reactive mechanical milling. Mg and Mg10Al powders were first ball-milled and then pulverized by hydrogenation at 350 °C for 5 cycles. Hydrogen absorption measurements were carried out by pressure-composition-temperature and thermo-gravimetric analyses. The microstructure of the powders was characterized by scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. After pulverization by hydrogenation, the surface area of pure Mg increased greatly from 0.61 m2/g (as-milled) to 6.16 m2/g and the crystalline size decreased. In addition, the amount of MgO decreased when the milled Mg alloys were pulverized. The pulverized Mg exhibited a higher hydrogen storage capacity (3.36 wt%) than the ball-milled Mg (0.14 wt%) at 350 °C. The addition of Al decreased the dehydrogenation temperature in comparison to pure Mg.