Study on expansion characteristics of Al–Al2O3 composite seals for intermediate‐temperature solid oxide fuel cell

Al2O3‐based composite seal with 10 wt% Al powder addition (A10) possesses excellent plastic and mechanical performance under wide temperature range of solid oxide fuel cell. The thickening phenomenon of A10 seal between 250°C–400°C and 600°C–750°C is caused by the thermal expansion of organic additives and the volume expansion when solid–liquid Al react with oxygen to form Al2O3. The thickness change rate reaches the maximum which is about 5% at 300°C and is about 4.46% at 650°C. The Gibbs free energy for reaction between Al and Al2O3 in the temperature range of 523–1 023 K is all less than 0, which is proved by the fact that A10 exhibits excellent self‐expansion and thermodynamic properties in the solid oxide fuel cell operating temperature. In current study, the thickness of 10 wt% Al particles added to Al2O3 casting tape with the temperature, compressive pressure and holding time increased. The process of oxidation of Al powder to Al2O3 mainly occurs between 600°C and 800°C. The Gibbs free energy are all less than 0 in the temperature range of 523–1 023 K, which is proved that these reactions can occur thermodynamically. A10 compressive seal showed excellent self‐expansion and thermodynamic properties in the SOFC operating temperature.