Comparative study of the leak characteristics of two ceramic/glass composite seals for solid oxide fuel cells

Abstract

Solid oxide fuel cells (SOFCs) have the potential to play a significant role in a future clean energy economy. However, SOFCs still face major obstacles before they can be commercialized, with efficient sealing being among the most prominent. The present research focuses on the comparative study of microstructure, crystal phase evolution, and leak rates, for two ceramic/glass seals used in an SOFC. The leak test apparatus is a controlled facility designed to incorporate different mechanical loading, stack configurations, and thermal cycles. Simultaneous leak testing with an acoustic emission (AE) sensor was also used to identify any micro-damage in seals. A two-level factorial design was applied to the first sealing composition to identify the main and the interactive factors for leak rates. MINITAB® was also used to determine a linear regression-based leak rate model. The second seal formulation employed a more stable glass which led to reduced leak rates. Additional factors in a two-level factorial design were investigated for the second seal formulation. Based on multiple experiments with different stack components, it was determined that the number of interfaces is most critical for leak rate, showing that even in the presence of thermal cycling, leakage is an interfacial dominated phenomenon.