Effect of milling intensity on the formation of LiMgN from the dehydrogenation of LiNH 2–MgH 2 (1:1) mixture

Abstract

Metal–N–H systems have recently attracted considerable attention as alternative hydrogen storage materials to traditional metal hydrides. In this work, the reactions of the mixture LiNH 2–MgH 2 (1:1) during different mechanical milling processes and the subsequent dehydrogenation reaction were investigated by using TGA, XRD and FT-IR in order to determine an optimal condition for the formation of pure LiMgN. High-energy milling (SPEX mill) and low-energy milling (rolling jar) techniques were used in this work. The results demonstrated that monolithic LiMgN can be produced using the low-energy ball milling technique. The hydrogenation properties of the as-prepared LiMgN were investigated by a Sieverts’ type instrument. In contrast, multiple reactions including the metathesis reaction between LiNH 2 and MgH 2 and release of H 2 and/or NH 3 took place during high-energy milling using the SPEX mill, which resulted in complicated and unexpected reactions during the subsequent dehydrogenation experiments. Consequently, the dehydrogenated products from the high-energy milled samples consisted of multi-phase mixtures.