Articles written in Bulletin of Materials Science
Volume 37 Issue 1 February 2014 pp 77-82
Two kinds of novel materials, Mg–1.6 mol% Ni–0.4 mol% NiO–2 mol% MCl (MCl = NbCl5, CrCl3), along with Mg–1.6 mol% Ni–0.4 mol% NiO for comparison, were examined for their potential use in hydrogen storage applications, having been fabricated via cryomilling. The effects of NbCl5 and CrCl3 on hydrogen storage performance were investigated. A microstructure analysis showed that besides the main Mg and Ni phases, NiO and Mg2Ni phases were present in all samples. MgCl2 was only found in halide-doped samples and NbO was only found in NbCl5-doped samples after ball milling. The particle size decreased significantly after 7 h of cryomilling. MgH2, Mg2NiH4 and Mg2NiH0.3 were present in all the samples, while NbH2 was only observed in the NbCl5 -doped sample after absorption. The NbCl5-containing composite exhibited a low onset absorption temperature of 323 K, which was 10 K lower than that of the no-halide doped catalyst. It absorbed 5.32 wt% of hydrogen in 370 s at 623 K under 4 MPa hydrogen pressure and can absorb 90% of its full hydrogen capacity in 50 s. Having an onset desorption temperature of 483 K in vacuum, the NbCl5 -containing composite desorbed hydrogen faster than the no-halide doped sample. The hydriding–dehydriding kinetics performance of the CrCl3-doped sample did not improve, but it did exhibit a lower onset desorption temperature of 543 K under 0.1 MPa, which was 20 K lower than that of the no-halide doped sample. NbO, NiO and NbH2 played important roles in improving absorption and desorption performances.
Volume 37 Issue 4 June 2014 pp 837-842
LaNi4.7Al0.3 alloy was prepared by vacuum induction melting in high purity helium atmosphere, and the ingot was pulverized into 200–400 mesh powder after annealing. X-ray diffraction (XRD) and scanning electron microscopies (SEM) were utilized to study the alloy morphology and phase structure. X-ray photoelectron spectroscopy (XPS) was used for surface analysis. The poisoned alloy was tested at 30 °C in the mixture gas by thermogravimetric and differential thermal analyses (TG + DTA). The hydrogen storage properties were studied by the pressure–composition–temperature test. The activated sample was completely deactivated after only 3 hydriding/dehydriding cycles in hydrogen containing 300 ppm CO at 30 °C, but hydrogen storage capacity did not degrade when tested at 80 °C. Additionally, two different steps appeared in the absorption processes. Combined with XRD, XPS and TG + DTA results, an explanation for this phenomenon is given.
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