Dependence of hydrogen storage characteristics of Mg-TiFe0.92Mn0.08 composite on amount of TiFe0.92Mn0.08

We investigated the hydrogen storage characteristics of Mg-x wt.%TiFe0.92Mn0.08 (x = 20, 35, and 50) composites prepared by wet mechanical milling. TiFe0.92-xMn0.08 and alpha-Fe phases were formed in these composites by the decomposition of TiFe0.92Mn0.08 after activation. The kinetics of the hydrogen absorption at low temperature was improved by increasing the amount of TiFe0.92Mn0.08. These improvements appear to be attributable to the TiFe0.92-xMn0.08 phase, which plays an important role as a pathway for the diffusion of hydrogen into the Mg matrix. In contrast, the hydrogen desorption temperature decreased as the amount of alpha-Fe originating from TiFe0.92Mn0.08 increased. The Mg-50 wt.%TiFe0.92Mn0.08 composite started to desorb hydrogen at the same temperature as Mg-50 wt.%Fe composite prepared under the same milling conditions although the former had much better hydrogen absorption characteristics than the latter at low temperature. We consider that the presence of alpha-Fe probably contributes to the improvement in the hydrogen desorption characteristics. (c) 2005 Elsevier B.V. All rights reserved.