Suppression of processing defects in large-scale anode of planar solid oxide fuel cell via multi-layer roll calendering
In spite of various advantages of solid oxide fuel cells (SOFCs) over various types of fuel cells, SOFCs are yet far from commercial applicability due to their high manufacturing costs. The challenges mainly stem from the ceramic processing defects, particularly for large-scale SOFCs, thereby resulting in high cost in quality control step. Here we present a simple and cost-effective roll calendering process for a lamination of NiO – yttria-stabilized zirconia (YSZ) composite anode tapes with size of 13 × 13 cm2, which can effectively suppress the defect generation and reduce the residual stress inhomogeneity compared to a conventional uniaxial press. The condition of roll calendering for the successful lamination is optimized based on the analyses of interfacial structure, relative density, and elongation length of the laminated tape against number of roll calendering cycles. X-ray diffraction residual stress and microstructure analyses are carried out for the laminated green anode bodies via the roll calendering and the uniaxial press, respectively. After sintering of each sample, the effect of microstructural feature on electrical property is also examined. The roll calendering process not only suppress the processing defects owing to the shearing, but also induce the evenly-distributed residual stresses with lower magnitude owing to the uniformly-applied pressure during lamination even for large-size sample. In addition, the processing defects are reduced by roll calendering, thereby exhibiting the superior electrical conductivity in practical operating condition.