Hydriding combustion synthesis of hydrogen storage alloys of Mg-Ni-Cu system

Hydriding combustion synthesis of Mg-Ni-Cu system hydrogen storage alloys from metal powder mixture was reported in this study. For studying this new process, the binary system of Mg2Cu was also synthesized at 753 and 798 K under hydrogen/argon atmosphere. The X-ray diffraction (XRD) patterns of the binary system alloy showed a good yield without any un-reacted Mg and Cu and lower synthesis temperature was preferred for avoiding evaporation loss of magnesium and for promoting the hydriding reaction. The XRD patterns of the ternary system alloys, Mg(2)Nio(0.75)Cu(0.25) and Mg2Ni0.5Cu0.5, showed the catalytic effect of nickel or copper on hydriding reaction because no intermediate products of Mg2Ni and Mg2Cu existed in final product. The hydriding curves of Mg2Ni0.75Cu0.25 showed the hydrogen storage capacity of 1.7 mass% at 473 K after 120 min, although the hydriding rate was not very high. The images of scanning electron microscopy (SEM) showed very interesting character of particle surface like scales of fish, which gave an evidence of eutectic reaction and disproportionation reaction in synthesizing the ternary alloy of Mg-Ni-Cu system. (C) 2002 Elsevier Science Ltd. All rights reserved.