Desorption behaviours from metal-N-H systems synthesized by ball milling

Three metal amides LiNH2, NaNH2 and Mg(NH2)(2) were synthesized by ball milling the metal hydrides under gaseous ammonia NH3 at room temperature. The decomposition behaviours from these metal amides were investigated by thermal desorption mass spectroscopy and thermogravimetry analysis methods. The results showed that LiNH2 decomposed at T > 230 degrees C and was transformed into the imide Li2NH with emitting NH3, while Mg(NH2)(2), decomposed at T > 180 degrees C and was transformed into MgNH and finally into Mg3N2 with emitting NH3 within 500 degrees C. Then, a new metal-N-H system composed of Mg(NH2)(2) and LiH with a molar ratio of 3:8 was designed by ball milling treatment and examined the hydrogen storage properties. The results showed that this system could reversibly absorb/desorb a large amount of hydrogen (similar to 7 wt.%) at a moderate temperature and pressure, which was better than the system of LiNH2 and LiH for hydrigen storage. (c) 2005 Elsevier B.V. All rights reserved.