Compliant seals

The various options for sealing and joining the ceramic and metal components in pSOFCs can be broadly classified into one of three categories rigid bonded seals, compressive seals, and bonded compliant seals. As outiined in Table 11.2, rigid... 

Bonded compliant seals Sealant bonds to adjacent pSOFC components and plastically deforms at room temperature and above... 

Weil, K.S. and Koeppel, B.J. (2008) Thermal stress analysis of the planar SOFC bonded compliant seal design. Int.J. Hydrogen Energy, 33, 3976-3990. 

Jiang, T.L. and Chen, M.H. (2009) Thermal-stress analyses of an operating planar solid oxide fuel cell with the bonded compliant seal design. Int. J. Hydrogen Energy, 34, 8223-8234. 

Figure 22.15 Discharge of lithium-air aqueous cells with a protected anode employing a compliant seal at the following discharge rates (1) 1.0 mAcm (2) 0.5 mAcm and (3) 0.2 mAcm . The thickness of the...

Compliant seals are easier to design because there is a more controlled sealing environment, but they are more subject to seal loss due to physical and chemical changes. 

The joint region in compliant seals can be plastically deformed above room temperatures, which lessens the thermal stresses caused due to CTE mismatch. This category of sealants includes metallic components and hence is electrically conducting. In addition to this, the cell bowing and non-uniformities in the gas distribution are potential problems. Brazing and bonded compliant seals fall in this category and are discussed in Sects. 5.3.2.1 and 5.3.2.2. 

In bonded compliant seals, a thin stamped foil is bonded to both sealing surfaces as shown in Fig. 5.10. A number of high-temperature alloys can be potential candidates for the foil membrane if they satisfy the following criteria. 

F. 5.10 Foil-based bonded compliant seal (Weil 2006)... 

Durafoil (22-Cr/7-Al/0.1-La + Ce/Fe) is a commercially used bonded foil as it satisfies the above-mentioned properties. The bonded compliant seals are non-sliding and metal foils endow a higher degree of geometric deformation. Under modest thermomechanical loading, the foil is deformed and may return to its original shape when the load is removed. 

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