Hydrogen Desorption Properties of Nanocrystalline MgH2-10 wt.% ZrB2 Composite Prepared by Mechanical Alloying

Abstract

Storage of hydrogen is one of the key challenges in developing hydrogen economy. Magnesium hydride (MgH₂) is an attractive candidate for solid-state hydrogen storage for on-board applications. In this study, <br /> 10 wt.% ZrB₂ was co-milled with magnesium hydride at different milling times to produce nanocrystalline composite powder. The effect of milling time and additive on the hydrogen desorption properties of obtained powder was evaluated by thermal analyzer method and compared with pure MgH₂. The phase constituents of powder particles were characterized by X-ray diffractometry method. The grain size and lattice strain of β-MgH₂ phase were estimated from the broadening of XRD peaks using Williamson–Hall method. The size and morphological changes of powder particles upon mechanical alloying were studied by scanning electron microscopy. XRD analysis showed that the mechanically activated magnesium hydride consisted of β-MgH₂, γ-MgH₂ and small amount of MgO. It is shown that the addition of ZrB₂ to magnesium hydride yields a finer particle size. The thermal analyses results showed that the addition of ZrB₂ particle to magnesium hydride and mechanical alloying for 30 h reduced the dehydrogenation temperature of magnesium hydride from 319 °C to 308 °C. This can be attributed to the particle size reduction of magnesium hydride.