Microstructure-based solid oxide fuel cell seal design using statistical mechanics

Abstract

Solid oxide fuel cells (SOFC) in a flat-plate configuration require a hermetic seal between the fuel and air sides of the electrodes, and this seal must withstand a variety of thermally-induced stresses over the lifetime of the cell. In this study, quantitative microstructure-property relationships are developed to predict optimum seal structures for mechanical properties and thermal expansion coefficient criteria. These relationships are used to create an inverse approach to characterizing the processing method from the desired microstructure. The main focus of the work concentrates on providing tools to enable macroscopic property predictions from the constituent properties using homogenization techniques based on the individual phase properties and microstructure morphology. The microstructure is represented by two-point correlation functions. Statistical continuum mechanics models were then employed and developed to predict the mechanical and thermal properties of the material. The models enable the prediction of elastic modulus and coefficient of thermal expansion of the multi-phase material. The inelastic mechanical behavior was also studied, indicating microstructure dependence. These models will aid in predicting the a proper seal microstructure (with desired elastic stiffness, coefficient of thermal expansion, and viscoelastic behaviors) based on a desired level of crystallization glass-ceramic materials.