Synthesis of Zn(BH4)2 and Gas Absorption and Release Characteristics of Zn(BH4)2, Ni, or Ti-Added MgH2–Based Alloys

Abstract

A sample [named Zn(BH4)2(+NaCl)] was synthesized by milling ZnCl2 and NaBH4 at 400 rpm under argon gas for 2 h. And Zn(BH4)₂(+NaCl)+MgH₂ sample was prepared by milling MgH₂ in a planetary ball mill and mixing with the Zn(BH₄)₂(+NaCl) synthesized by milling for 4 h in a mortar with a pestle. Then the gas-release characteristics of the two samples were investrigated. Analyses of XRD patterns and FT-IR spectra, as well as TGA, DTA, and SEM observations, were also performed. After heating the samples to 400 ℃, the weight losses of Zn(BH4)2(+NaCl) and Zn(BH4)2(+NaCl)+MgH2 were 11.2 and 8.2 wt%, respectively, with respect to the sample weight. The DTA results for the two samples showed a decomposition peak for Zn(BH4)2 at about 61 ℃. The DTA result of Zn(BH4)2(+NaCl) + MgH2 showed a decomposition peak for MgH2 at about 374 ℃. A sample of Zn(BH4)2(+NaCl)+MgH2 to which Ni, and Ti were added, with a composition of 90 wt% MgH2-5 wt% Zn(BH4)2(+NaCl)-2.5 wt% Ni-2.5 wt% Ti, in which a large amount of MgH2 is contained in order to make a large quantity of hydrogen be absorbed and released reversibly, was also prepared. The experimental results showed that addition of Zn(BH4)2(+NaCl), Ni, or Ti increased the dehydriding rate of MgH2, while decreased its initial hydriding rate.