Strength degradation and failure limits of dense and porous ceramic membrane materials

• Published in: Journal of the European Ceramic Society 2013-11, Vol.33 (13-14), p.2689-2698
• Main Authors: Pećanac, G., Foghmoes, S., Lipińska-Chwałek, M., Baumann, S., Beck, T., Malzbender, J.
• Format: Article
• Language: English
• Subjects: Ceramics; Crack propagation; Degradation; Failure; Lifetime; Membranes; Oxy-fuel; Porous materials; Residual stress; Strength
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/j.jeurceramsoc.2013.04.018

Thin dense membrane layers, mechanically supported by porous substrates, are considered as the most efficient designs for oxygen supply units used in Oxy-fuel processes and membrane reactors. Based on the favorable permeation properties and chemical stability, several materials were suggested as promising membrane and substrate materials: Ba0.5Sr0.5Co0.8Fe0.2O3−δ, La0.6−xSr0.4Co0.2Fe0.8O3−δ (x=0, 0.02) and Ce0.9Gd0.1O1.95−δ. Although membranes operate at elevated temperatures, the ends of tubes in certain three-end concepts remain almost at room temperature. The current work concentrates on the failure potential of these membrane parts, where in a complex device also the highest residual stresses should arise due to differences in thermal expansion. In particular, sensitivity of the materials to subcritical crack growth was assessed since the long-term reliability of the component does not only depend on its initial strength, but also on strength degradation effects. The results were subsequently used as a basis for a strength–probability–time lifetime prediction.