Dehydriding and rehydriding properties of Mg(NH 2) 2–LiH systems

Abstract

The dehydriding and rehydriding properties of the mixtures of 3Mg(NH 2) 2 + nLiH ( n = 6, 8, and 12) were investigated by pressure–composition ( p– c) isotherm and X-ray diffraction (XRD) measurements in order to clarify the effects of the LiH ratio n on the properties. The amounts of the hydrogen desorbed from the mixtures with n = 6, 8, and 12 were 5.4, 5.1, and 4.5 mass%, respectively; this indicates that the amounts on a unit mass basis decrease with increasing n. However, the molar ratios of the desorbed hydrogen to the mixtures estimated from the amounts were almost equal, and also the features of the p– c isotherms were similar to each other. Moreover, the Li 2Mg(NH) 2 and LiH phases were observed in XRD profiles of all the mixtures after p– c isotherm measurements. These results suggest that the dehydriding reaction of the mixtures of 3Mg(NH 2) 2 + nLiH ( n = 6, 8, and 12) under hydrogen pressure is not dominantly affected by the value of n. On the other hand, the amounts of the ammonia desorbed from the mixtures detected by mass spectroscopy decreased with increasing n.