SUPPORTED DENSE CERAMIC MEMBRANES FOR OXYGEN SEPARATION
This project addresses the need for reliable fabrication methods of supported thin/thick dense ceramic membranes for oxygen separation. Some ceramic materials that possess mixed conductivity (electronic and ionic) at high temperature have the potential to permeate oxygen with perfect selectivity, making them very attractive for oxygen separation and membrane reactor applications. In order to maximize permeation rates at the lowest possible temperatures, it is desirable to minimize diffusional limitations within the ceramic by reducing the thickness of the ceramic membrane, preferably to thicknesses of 10 {micro}m or thinner. It has proven to be very challenging to reliably fabricate dense, defect-free ceramic membrane layers of such thickness. In this project we are investigating the use of ultrafine SrCo{sub 0.5}FeO{sub x} (SCFO) powders produced by aerosol pyrolysis to fabricate such supported membranes. SrCo{sub 0.5}FeO{sub x} is a ceramic composition that has been shown to have desirable oxygen permeability, as well as good chemical stability in the reducing environments that are encountered in some important applications. Our approach is to use a doctor blade procedure to deposit pastes prepared from the aerosol-derived SCFO powders onto porous SCFO supports. We have previously shown that membrane layers deposited from the aerosol powders can be sintered to high density without densification of the underlying support. However, these membrane layers contained large-scale cracks and open areas, making them unacceptable for membrane purposes. In the past year, we have refined the paste formulations based on guidance from the ceramic tape casting literature. We have identified a multicomponent organic formulation utilizing castor oil as dispersant in a solvent of mineral spirits and isopropanol. Other additives were polyvinylbutyral as binder and dibutylphthalate as plasticizer. The nonaqueous formulation has superior wetting properties with the powder, and presumably evolves less tensile stress during drying. Membrane layers have been first made from the commercial SCFO powder to accelerate evaluation of the new formulations, since the aerosol power synthesis process is time consuming. We found that, with appropriate levels of the dispersant, we could increase the powder loading in pastes made from the commercial SCFO powder up to 43 wt%. This, combined with the attributes of the other additives, has allowed us to prepare sintered supported membranes with no evidence of cracking. However, the membranes prepared from the relatively coarse commercial powder did not sinter to the high density level (at 1100 C in N{sub 2}) that we had observed with the aerosol-derived powder. This is the current status of the project. The future efforts will be focused toward evaluation of the new paste formulation with aerosol-derived SCFO powder. We anticipate that some adjustments, particularly to the dispersant levels, will be needed for the high specific area aerosol powders.
- Research Organization:
- University of New Mexico (US)
- Sponsoring Organization:
- (US)
- DOE Contract Number:
- FG26-98FT40120
- OSTI ID:
- 823189
- Resource Relation:
- Other Information: PBD: 1 Mar 2003
- Country of Publication:
- United States
- Language:
- English
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