Oxygen transport and stability of asymmetric SrFe(Al)O3−δ-SrAl2O4 composite membranes
- 作者：A.V. Kovalevsky ; V.V. Kharton ; F.M.M. Snijkers ; J.F.C. Cooymans ; J.J. Luyten ; F.M.B. Marques
- 关键词：Oxygen permeability ; Mixed ionic-electronic conductor ; Asymmetric ceramic membrane ; Ferrite-based composite ; Microstructural stability
- 刊名：Journal of Membrane Science
- 出版年：2007
- 期刊代码：55_03767388
- 类别：ch
- 出版时间：1 September 2007
- 卷：301
- 期：1-2
- 页码：238-244
- 文件大小：1006 K
摘要
In order to appraise a two-stage compaction procedure using pore-forming additives for the fabrication of asymmetric mixed-conducting membranes where the porous and dense layers are made of the same composition, the oxygen permeability of a series of (SrFeO3−δ)0.7(SrAl2O4)0.3 composite samples with varying architecture was studied at 1073–1223 K. The preparation route for the crack-free supported membranes included pressing of the starch-containing and pure dual-phase composite powders, sintering at 1623 K, and subsequent surface modification of the dense layers having the thickness of 0.12–0.15 mm. Analysis of the oxygen permeation fluxes show a significant limiting effect of oxygen diffusion through the support, where the porosity and average pore size are 20%and 2–4 μm, respectively. The overall level of oxygen transport, higher than that in the symmetric surface-activated membranes, was only achieved at 1173–1223 K for the porous layer thickness of 0.4 mm. Slow microstructural degradation due to the support sintering, evidenced by dilatometry, leads to a moderate decrease in the oxygen fluxes with time. At 1973 K, the corresponding changes were approximately 16%during 220 h. The results suggest that increased total porosity, preferential pore orientation perpendicular to the dense layer and incorporation of nano-sized catalyst particles into the pores are needed to increase the performance of asymmetric ferrite-based membranes.