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Effects of thermal activation on hydrogen permeation properties of thin, self-supported Pd/Ag membranes

2009; Elsevier BV; Volume: 68; Issue: 3 Linguagem: Inglês

10.1016/j.seppur.2009.06.015

1873-3794

Wakshum Mekonnen Tucho, Hilde J. Venvik, Marit Stange, John C. Walmsley, Randi Holmestad, Rune Bredesen,

Ammonia Synthesis and Nitrogen Reduction

The effects of thermal treatments in air and in N2/Ar atmospheres on H2 permeation of self-supported 5 and 10 μm Pd/23 wt% Ag membranes prepared by magnetron sputtering are investigated. After hydrogen flux stabilization at 300 °C, the membranes were annealed in air at 300 °C or in N2/Ar at 300/400/450 °C for 4 days and then tested for hydrogen permeation at 300 °C. Air treatment generally induced improved permeation for all thicknesses. For the treatments in N2/Ar, permeability generally depends on the heat treatment temperatures and on the thickness of the membranes. In particular, hydrogen permeation was improved for treatment temperature of 450 °C, but reduced for 400 °C and below. An average permeability of 2.61 ± 0.4 mol/(m s Pa0.5) for permeation measurements at 300 °C before heat treatment and an apparent activation energy of ∼7 kJ/mol obtained in the range of 300–450 °C for N2/Ar treated membranes are comparable to some of the values in the literature. Substantial permeance difference was observed for the measurements in the temperature range, 300–450 °C between the membranes heat treated in air at 300 °C and in N2/Ar at 450 °C. The measured permeance between 300 and 450 °C for the 10-μm membranes heat treated in air at 300 °C remains practically unchanged, i.e. Ea ≈ 0.