Synthesis, structural characterization and hydrogenation behaviour of the new hydrogen storage composite alloy La₂Mg₁₇-x wt% LaNi₅

Abstract

Alloys with the general formula La₂Mg₁₇-xwt % LaNi₅ (x=10, 20, 30 and 40) have been synthesized and the hydrogen storage capacity of these new composite materials investigated. The materials were activated at temperatures of ∼ 360 °C under a hydrogen pressure of ∼ 33 kg cm⁻². Optimum storage capacity of 5.24% in terms of pressure and composition was observed for La₂Mg₁₇-10 wt% LaNi₅ at ∼ 400°C. This is one of the very highest hydrogen storage capacities known so far. The hydriding rate of La₂Mg₁₇ in the presence of LaNi₅ is about 3–4 times that of La₂Mg₁₇ alone. In order to elucidate the role of LaNi₅ in accelerating the hydrogen desorption rate of La₂Mg₁₇, the structural and microstructural characteristics of the composite material were carried out employing the XRD, SEM and EDAX techniques. The hydriding rate and hydrogen storage capacity are closely related to the microstructure and the types of phase present in the alloys.