V-Cr-Cu dual-phase alloy membranes for hydrogen separation: An excellent combination of ductility, hydrogen permeability and embrittlement resistance

Abstract

V-Cr-Cu alloys consisting of bcc-(V) and fcc-(Cu) are developed as a new type of hydrogen permeable metal membranes based on the idea of distributing functions on the different phases. The bcc-(V) is mainly responsible for hydrogen permeation, and the fcc-(Cu) imparts improvement in ductility. The addition of Cr in as-cast (V100−xCrx)70Cu30 (x=0…10at%) alloys reduces the hydrogen solubility and thus improves the hydrogen embrittlement resistance, but decreases the hydrogen diffusivity and permeability. As-cast (V95Cr5)70Cu30 exhibits an excellent combination of ductility, hydrogen permeability and embrittlement resistance. After cold rolled to a thin foil of ~100µm in thickness and subsequent annealing, this alloy membrane shows a pronounced high hydrogen permeation flux, particularly ~34 cc H2 cm−2min−1 at a hydrogen pressure difference of 0.7MPa at 673K. This corresponds to a permeability of ~3.98×10−8mol H2 m−1s−1Pa−0.5. This work demonstrates that the dual-phase structure in V-Cr-Cu alloys ensures a feasible route for a large scale fabrication of thin membranes by cold rolling that features high hydrogen permeation proprieties.