PROTON-CONDUCTING DENSE CERAMIC MEMBRANES FOR HYDROGEN SEPARATION
Dense thin films of SrCe{sub 0.95}Tm{sub 0.05}O{sub 3-{delta}} (SCTm) with perovskite structure were prepared on porous alumina or SCTm substrates by the methods of (1) polymeric-gel casting and (2) dry-pressing. The polymeric-gel casting method includes preparation of mixed metal oxide gel and coating of the gel on a macroporous alumina support. Micrometer thick SCTm films of the perovskite structure can be obtained by the polymeric-gel casting method. However, the deposited films are not hermetic and it may require about 50 coatings in order to obtain gas-tight SCTm films by this method. Pd-Cu thin films were synthesized with elemental palladium and copper targets by the sequential R.F. sputter deposition on porous substrates. Pd-Cu alloy films could be formed after proper annealing. The deposited Pd-Cu films were gas-tight. This result demonstrated the feasibility of obtaining an ultrathin SCTm film by the sequential sputter deposition of Sr, Ce and Tm metals followed by proper annealing and oxidation. Such ultrathin SCTm membranes will offer sufficiently high hydrogen permeance for practical applications. Thin gas-tight SCTm membranes were synthesized on porous SCTm supports by the dry-pressing method. In this method, the green powder of SCTm was prepared by wet chemical method using metal nitrates as the precursors. Particle size of the powder was revealed to be a vital factor in determining the porosity and shrinkage of the sintered disks. Small particle size formed the dense film while large particle size produced porous substrates. The SCTm film thickness was varied from 1 mm to 0.15 mm by varying the amount of the target powder. A close match between the shrinkage of the substrate and the dense film led to the defect free-thin films. The selectivity of H{sub 2} over He with these films was infinite. The chemical environment on each side of the membrane influenced the H{sub 2} permeation flux as it had concurrent effects on the driving force and electronic/ionic conductivities. The H{sub 2} permeation rates were found to be inversely proportional to the thickness of the dense film indicating that bulk diffusion rather than surface reaction played a dominant role in H{sub 2} transport through these dense films within the studied thickness range (150 {micro}m - 1 mm).
- Research Organization:
- University of Cincinnati (US)
- Sponsoring Organization:
- (US)
- DOE Contract Number:
- FG26-00NT40818
- OSTI ID:
- 838557
- Resource Relation:
- Other Information: PBD: 1 Nov 2004
- Country of Publication:
- United States
- Language:
- English
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