Thermal stability of as-received LiAlH4 and milled LiAlH4 has been investigated. The thermal decomposition mechanism of as-received LiAlH4 depends on the temperature-time history. Apparent activation energies and enthalpies of the reactions have been obtained. During milling treatment, the high temperature and pressures locally induced by shocks lead to LiAlH4 mechanically decomposition. The decomposition temperatures of LiAlH4 and Li3AlH6 are both reduced by similar to 60 degrees C due to particle size reduction produced by mechanical milling. Besides, the activation energy of the decomposition reaction of LiAlH4 decreases as compared to as-received LiAlH4. Moreover, a layer of oxide (similar to 5 nm) at the surface of the milled alanate Li3AlH6 is observed. This layer could have a drastic influence on decomposition H-kinetics. (C) 2007 Elsevier Ltd. All rights reserved.