Developing a heating procedure to optimise hydrogen permeance through Pd-Ag membranes of thickness less than 2.2 μm

The Pd-Ag films, with a total thickness of < 2.2 mum. were deposited by electroless plating on the inside of alpha -alumina membranes from SCT. The H-2 permeances through separated Pd-Ag layers were poor and heating conditions were investigated to improve the H-2 permeances through the metal films. The heating temperature, heating time and heating environment all had a significant effect on the H-2 permeance and the H-2 to N-2 selectivity of the Pd-Ag films. The films were oxidised at 310 degreesC for 1 h after heat treatment in Ar at 550 degreesC, and then reduced in H2. This additional surface modification step more than doubled the H-2 permeance through the film and only created a moderate amount of membrane defects as indicated by the increase in the N-2 permeance. After the heating process, the membranes were characterised from 250 to 410 degreesC using both a sweep gas and a positive pressure difference. (C) 2002 Elsevier Science B.V. All rights reserved.