Three different modification agents, gamma-Al(2)O(3), -Al(2)O(3), a and TiO(2) were used to modify Al particle surfaces. The effect of different modification agents on hydrogen-generation by the reaction of modified Al powder with water was investigated. It was found that different modification agents have different effect on the reaction dynamics of Al with water. The complete hydrogen-generation time of gamma-Al(2)O(3) modified Al powder is obviously shorter than that of gamma-Al(2)O(3) a and TiO(2) modified Al powders, because of their different induction time for the beginning of the reaction. Possible mechanism analyses indicated that the phase transformation and resultant weakening of Al particle surface layer during processing strongly depends on the nucleation energy barrier on modification oxide grains. As gamma-Al(2)O(3) has a low nucleation energy barrier, the phase transformation of Al particle surface layer is relatively complete so that gamma-Al(2)O(3) modified Al powder has a short induction and complete reaction time with water. This implies that the Al surface modification probably originates from the phase change of its surface layer. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.