The dependence of the hydrogen desorption temperature of MgH sub(2) on its structural and morphological characteristics

In this study the effects of mechanical milling on the structural and morphological characteristics of MgH sub(2) were investigated and it was found a strong correlation with the hydrogen desorption temperature of MgH sub(2). The MgH sub(2) powder was mechanically milled for a duration ranging from 0.5 to 20 h. X-ray diffraction (XRD), scanning electron microscope (SEM), and optical microscope (OM) techniques were used to investigate the effects of the mechanical milling process on the structural and morphological characteristics of the powder. The hydrogen desorption temperatures of MgH sub(2) were measured using a differential scanning calorimeter (DSC). It was found that after 2 h of mechanical milling, the hydrogen desorption temperature of MgH sub(2) had decreased from 421.0 to 363.0 degree C, and simultaneously, the smallest particle sizes and the highest specific surface areas were obtained. Prolonging the mechanical milling time over 2 h resulted in an increase in the particle size and a corresponding decrease in the specific surface area of the powders. The prolonged milling also increased the hydrogen desorption temperature of MgH sub(2). These observations indicate that a minimum hydrogen desorption temperature of MgH sub(2) can be obtained, and that this temperature is dependent on the particle size and the specific surface area of the powder.