Poisoning effect of oxygen on hydrogenation performance of a Zr-V-Ni Laves phase alloy

摘要

Zr-based Laves phase alloys have been considered as suitable getter materials for hydrogen isotopes recovery, storage and delivery and received considerable attention during past decades. This work focuses on hydrogenation performance of a pseudo-binary Zr-V-Ni Laves phase alloy with the composition of Zr(V0.95Ni0.05)(2) after pre-exposure in different contents of O-2. It is found that introduced pure oxygen can be rapidly absorbed by the fully activated Zr(V(0.95)Ni(0.052)n alloy within 40 s. All of the experimental samples pre-exposed in oxygen consist dominant C15 type ZrV2 Laves phase and minor Zr3V3O oxides. With the further increase the oxygen pressure to 4.0 kPa in specimen chamber, Bragg peaks of Zr2V, V-rich BCC solid solution phase and ZrO2 phase, including baddeleyite (alpha-ZrO2) with monoclinic structure and a small amount of tazheranite (gamma-ZrO2) with cubic structure are observed in addition to the dominant ZrV2 and minor Zr3V3O phases. Meanwhile, it can be seen that the lattice parameter of cubic C15 type ZrV2 calculated from Rietveld refinement increases from 7.402 to 7.432 angstrom with the increase of O-2 content and the corresponding unit cell volume increases 0.86 vol.% as the O-2 pressure from 1.0 to 4.0 kPa, which indicates more oxygen atoms have been dissolved into the lattice of ZrV2. All of the oxygen poisoned Zr(V0.95Ni0.05)(2) alloys can absorb hydrogen and the capacity decreases from 3.39 to 2.22 H A(-1) with the increase of oxygen pressure from 1.0 to 4.0 kPa, comparing with the maximum hydrogen storage capacity (4.34 H A(-1)) of the fully activated fresh alloy. The existence of oxygen is found to decrease both capacity and kinetics of Zr(V0.95Ni0.05)(2) by forming passivation layer oxides which block the dissociation of H-2 molecule on the surface. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.