The high H2 storage capacity, the reversibility and the low cost make magnesium hydride a promising material for hydrogen storage at the solid state. The stability of these materials under H2 cycling has been tested in this paper. Moreover, the morphological modifications of MgH 2 particles during hydrogen cycling have been studied. In particular, it is discussed how experimental parameters such as the temperature and the nature of the catalyst could affect the morphological changes occurring after cycling for MgH2 powder ball milled with Fe or Nb2O 5. The cycled sample, presents the formation of hollow particles constituted by MgO shell and the absence of the catalyst in most of the particles has been observed. Ball milled MgH2 with and without catalyst has been prepared and different thermal treatments have been performed in a Sievert's type apparatus. Scanning electron microscope has been used for the observation of the powders. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.