Hydrogenation behaviour of the new composite storage material Mg- x% FeTi

Abstract

Mg- x wt.% FeTi composite alloys have been successfully synthesized. The hydrogenation behaviour of these alloys has been extensively studied. The materials have been activated at 400 °C under a hydrogen pressure of approximately 30 kg cm −2 and their hydrogen storage capacities and kinetics have been evaluated. The new composite hydrogen storage material in contrast to the native ingredient FeTi, has been found to possess much higher storage capacity and exhibits favourable absorption-desorption kinetics. For Mg-40% FeTi, a storage capacity of ∼3–3.6 wt.% at room temperature (≈27 °C) has been found. This is the highest known capacity exhibited by any hydrogen storage material at ambient conditions. In order to unravel the hydrogenation behaviour of these materials, structural-microstructural characteristics, and chemical composition before and after hydrogenation through X-ray diffraction, scanning electron microscopy and energy-dispersive analysis of X-rays have been carried out. The ambient condition hydrogenation properties of these composite alloys have been found to be strongly correlated with the structural and microstructural characteristics. Based on the observed structural and microstructural characteristics, the details of hydrogenation behaviour have been outlined in terms of cracking of FeTi matrix on hydrogenation and provision of continued fresh surfaces for hydrogenation of FeTi-Mg, Mg-TiMg eutectic mixtures or FeTi-Mg complexes. The present composite alloy corresponds to a new hydrogen storage material with higher storage capacity (≈3–3.6 wt.%) and suitable kinetics (initial hydrogenation in 10 min, saturation hydrogenation in 40 min).