Hydrogen sorption properties of V85Ni15. (1st February 2018) - Tosti, S.
Abstract: An alloy with nominal composition V85 Ni15 was prepared in a vacuum induction melting apparatus. The chemical analysis of the sample showed a V (Ni) content of 82.63 (15.68) at% and small contaminations by carbon and aluminum. XRD measurements confirmed that the bcc Ni-V solid solution phase is the main constituent of the sample. However, a minor impurity (approximately 6.5 wt%) due to the precipitation of the sigma NiV3-x phase is present in the sample. Hydrogen sorption measurements extending from 150 °C up to 400 °C in a wide pressure range (up to 90 bar) were performed. Upon hydrogenation below 250 °C, one observes the subsequent presence of an α phase and of two hydride phases with different values of dehydrogenation enthalpy: ΔHdehydr = 21 ± 1 kJ/mol for 0.15 ≤ H/M ≤ 0.30 and ΔHdehydr = 26 ± 2 kJ/mol for 0.53 ≤ H/M ≤ 0.59. Above 300 °C, there is no evidence of the formation of hydrides and only an α phase is present up to the maximum measured composition, with a hydrogenation enthalpy ΔHhydr = 10.0 ± 0.5 kJ/mol. Graphical abstract: Highlights: Alloy with V (Ni) content of 82.63 (15.68) at% and small contaminations by C and Al. bcc Ni-V solid solution phase plus ∼6.5 wt% of the sigma NiV3-x phase. Hydrogen sorption measurements between 150 and 400 °C up to 90 bar. Below 250 °C, one observes an α phase and two hydride phases. Above 300 °C, only an α phase is present.