Microstructure and hydrogen absorption-desorption properties of Mg-TiFe0.92Mn0.08 composites prepared by wet mechanical milling

The microstructure and hydrogen absorption-desorption properties of the Mg-50 wt.% TiFe0.92Mn0.08 composites prepared by wet mechanical milling of Mg and TiFe0.92Mn0.08 powders in n-hexane were evaluated. With increasing milling time and/or rotation speed, the average particle and crystallite sizes of Mg and TiFe0.92Mn0.08 reduced and the TiFe0.92Mn0.08 phase was uniformly distributed in the Mg matrix. After activation, all composites absorbed hydrogen at 25 degreesC, and the hydrogen absorption-desorption properties were improved with increasing the degree of dispersion of the TiFe0.92Mn0.08 phase in the as-milled composite. A composite milled at 600 rpm for 80 h absorbed hydrogen of nearly 3.5 wt.% at 25 degreesC and started to desorb hydrogen around 300degreesC under hydrogen pressure of 0.1 MPa. These good hydrogen absorption-desorption properties are due to the high degree of dispersion of TiFe0.92Mn0.08 phase, the introduction of micro-cracks and the formation of TiFe0.92-xMn0.08 and alpha-Fe phases. We also found that the formation of TiFe0.92-xMn0.08 and alpha-Fe phases affects the thermodynamic stability of the resultant hydride. (C) 2003 Elsevier B.V. All rights reserved.