Microstructure and Hydrogen Desorption in Nanostructured MgH2-Fe

Mg-based nanostructured hydrides have been synthesized by ball milling using two alternative approaches. The first is based on the reactive milling of Mg powders in H2 atmosphere, while the second on the milling of commercial MgH2 powders under inert atmosphere in both cases 10wt% Fe was added to the powder mixture, with the aim of introducing a catalyst agent. The microstructural characterization was carried out by X-ray diffraction, and both scanning and transmission electron microscopy. Hydrogen desorption behavior was evaluated by differential scanning calorimetry. Almost full hydrogenation of pure Mg powders can be achieved by reactive milling. Catalyst addition strongly accelerates the hydride formation . Both reactive milling of Mg powders and inert gas milling of MgH2 induce a nanosized microstructure with similar H-desorption behavior The role of Fe becomes particularly evident in H-desorption. In fact a temperature decrease of about 100°C was found in samples having the same crystallite size and similar powder morphology.