Modeling of solid oxide fuel cell sintering stress and deformation

In this study, an atomistically informed constitutive term representing microscopic scaled contraction is correlated and implemented to elucidate macroscopic sintering deformation induced by thermal stress in co-sintered anode-support half-cell of solid oxide fuel cell (SOFC). Molecular dynamics (MD) method is developed for a selected domain of porous anode and dense electrolyte layer from the half-cell, aiming to understand the microscopical contraction mechanisms during the sintering process and relation with particle aggregation/neck growth. It is found that both thermal effect and driving force of attraction between the neighboring atoms at high temperatures play a significant role to result in domain volume change. When sintered porous morphology is formed, positions and structures of the particles are stabilized, the sintering contraction becomes slower. This microscopic volume change is quantified along the length direction and further correlated as an intrinsic strain term representing macroscopic contraction property, which is also incorporated with thermal strain and elastic strain. A macroscopic half-cell model is developed and applied for co-sintering of SOFC thick anode and thin electrolyte layer, aiming to analyze dynamic deformation phenomenon experimentally observed during heating, insulation and cooling (the so-called temperature-increasing, -insulation and -decreasing, respectively) stages. It is revealed that, during the initial heating stage, a pronounced thermal expansion effect is observed. As into the insulation stage, the contraction characteristics become prominent. Further during the cooling stage, cell deformation stabilizes. This trans-scale modeling approach provides valuable insights for optimizing deformation and stress concentration during the co-sintering process of SOFC cell.