As-received and ball milled/catalyzed samples of NaAlH 4 and LiAlH 4 were heated in an environmental scanning electron microscope (ESEM). Morphological changes during heating and hydrogen desorption were recorded in real time. Both as-received materials underwent dramatic morphological and destructive structural changes upon heating, whereas the ball milled/catalyzed samples showed a benign outgassing with little morphological change. These observations help explain why milled/catalyzed samples of metal hydrides perform better as reversible hydrogen storage materials than their uncatalyzed bretheren. Real time videos of the morphological changes observed during heating can be viewed online at the McGrady group website: http://www.unb.ca/fredericton/science/chem/smcgrady/group/shanebeattie/InsituESEM-alanates.html .
