Compliant Glass Composite Sealants for SOFC Stacks

Solid oxide fuel cells (SOFCs) require robust, hermetic seals that can prevent both fuel leakage and direct mixing of fuel and air- The seal materials should be electrical insulators and should be chemically and mechanically stable in high temperature reactive environments (e-g-, moist reducing and/or oxidizing conditions)- The seals should exhibit no deleterious interfacial reactions with other cell components, should be created at a low enough temperature to avoid damaging cell components (not higher than 900ºC for some materials), and should not migrate or flow from the designated sealing region because of any applied load during cell operation- In addition, the seals should be able to withstand numerous thermal cycles between the operational temperature (e-g-, 700-900ºC) and room temperature- Recent research has focused on “compliant (or viscous)” glasses that remain stable over time in the SOFC stack operating environment- These materials are able to accommodate relative motion between the surfaces being sealed without the development of permanent leaks, and to “reseal” cracks created from thermal stresses through viscous flow- The compliant glasses (including MO-SCI G73, G102, etc-) considered for the viscous sealing application have broadly desirable thermo-mechanical properties and thermo-chemical characteristics, but their relatively low CTE (coefficient of thermal expansion) values below the glass transition temperature are still a concern- We propose to develop composite materials combining the compliant, crystallization- resistant glasses developed by MO-SCI with higher expansion, chemically-compatible filler materials to create a ‘compliant composite sealant’ with greater CTE-