Magnesium hydride prepared by ball milling: evolution of its properties during the first H2 absorption and desorption cycles

V. FUSTER; G. URRETAVIZCAYA; F. CASTRO

Cracovia, Polonia

Simposio; International Symposium on Metal-Hydrogen Systems, Fundamental and Applications; 2004

Universidad de Ciencia y Tecnología de Cracovia

In this work we analyze the evolution of the kinetic and microstructural properties of MgH2 submitted to a few hydriding and dehydriding cycles. The hydride was prepared by ball milling Mg powder under 5 bar of H2 at room temperature using a Uni-Ball-Mill II apparatus. The evolution was followed by kinetic measurements in a volumetric device, differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser granulometry. We observe that the hydrogen desorption from the as-milled sample when scanned in temperature (DSC) occurs at two different temperatures. After a few cycles the first desorption peak shifts towards higher temperatures. A related behaviour is observed in constant temperature absorption and desorption kinetic measurements. An explanation based on the degradation of the microstructural properties acquired during milling is proposed.