Structural destabilisation of MgH sub(2 obtained by heavy ion irradiation)

MgH sub(2 powder samples have been irradiated with 120 keV Ar) super(+)8 ions with different ion fluencies ranging from 10 super(12 to 10) super(1)6 ions/cm super(2. Irradiation effects are estimated by SRIM calculations, and investigated experimentally using Raman spectroscopy and X-ray diffraction (XRD) analysis. The observed changes of structure and vibrational spectra are elaborated, their consequences on hydrogen bonding in MgH) sub(2) discussed, and influence on H-desorption properties investigated by Temperature Programmed Desorption (TPD) and Differential Scanning Calorimetry (DSC) techniques. It has been established that near-surface defects have a predominant influence on decreasing the H-desorption temperature. Variations of Raman, TPD and DSC spectra with irradiation conditions suggest that there are several mechanisms of dehydriding, and that they depend on defect concentration, interaction and ordering.