Nb-Pd-Ti BCC thin films for hydrogen separation

Abstract

An investigation was carried out into Nb-Pd-Ti ternary system to determine possible body-centered cubic (b.c.c.) membranes that can be used for hydrogen separation. A library of thin films was produced covering the greater portion of Nb-Pd-Ti ternary diagram using a combinatorial approach. The library was screened both structurally and in terms of a reactivity index defined as the ratio of the resistivity measured in the films under hydrogen and argon. The study showed that a substantial portion of compositional field stretching from Nb to Ti yield thin films with b.c.c. structure. The evaluation based on the reactivity index showed a narrow region close to Nb corner as possible compositions for separation membranes. The b.c.c. field was also screened with regard to the lattice volume so as to identify regions of acceptable hydrogen solubility. The superposition of two maps; one reactivity index and the other lattice volume yield a field 32 < Nb <41, 27 < Pd <44, 20 < Ti <38 as possible compositions for separation membranes. (C) 2018 Elsevier B.V. All rights reserved.