PNNL

Abstract

This work details development of a discrete element model (DEM) to study the integrity of the bonded interfaces between the cathode and contact paste materials in a solid oxide fuel cell (SOFC) and the effect of different interface roughness values on the integrity of the dissimilar material joint. The fracture behavior of the bonded interface is explicitly modeled using a DEM method, where the two types of materials are modeled by densely packed spherical particles with finite size. The effect of roughness on interface toughness for different sintering temperatures was examined. A parametric study using the DEM model with different particle configurations also was performed to evaluate the sensitivity and variability of the predicted results at different sintering temperatures. The varied parameters included the elastic and shear modulus of the contact paste and interfacial roughness between the cathode and contact paste. The model demonstrates that the roughened interface can provide more ultimate mechanical strength compared with the smooth interface. Interfacial toughness increases with interfacial roughness and sintering temperatures. In addition, the contact paste with higher stiffness properties can be beneficial in terms of delaying the onset of the initial interfacial damage at rough interfaces. The effect of different relative strengths between the paste and interface on fracture toughness also was explored. It was found that, in general, toughness decreases with increasing strength ratio between the interface and paste.