To assess the mechanical reliability and durability of solid oxide fuel cells (SOFCs), a suitable creep test method needs to be developed. The objective of this study is to examine the potential of small punch (SP) method as a simple creep testing method for SOFCs. In this study, the creep properties of Ni-YSZ composites were evaluated at temperatures of 800-900˚C, and at stresses of 47.3 to 89.8 MPa under 1% hydrogen environment. The obtained creep curves by the SP method showed three stages: initial transition creep, secondary creep, and tertiary stages. The central displacement versus time data obtained by the SP method was found to be characterized by a power law relationship. Even though quantitative comparisons need to be made with conventional methods, the above result suggests the usefulness of the SP methods for characterizing the creep properties in constituent materials of SOFCs.

This paper discusses the relationship between the elongation and compression behavior and microstructural changes under redox cycles of porous Ni(O)–YSZ cermets for solid oxide fuel cells (SOFC). Mechanical damage in SOFC and SOEC is one of the most important degradation factors governing the electrical performance of cells. Therefore, it is necessary to know the mechanical properties of each component material, such as elastic and deformation properties, in the operating environment. Particularly, of the Ni(O)–YSZ cermets which currently makes up 90% of the volume of the cell, with present mainstream anode supported SOFC and SOEC. Therefore, understanding the properties of the Ni(O)–YSZ cermets plays an important role in ensuring the performance of the entire SOFC and SOEC. In this study, the microstructural changes of Ni(O)–YSZ cermet by reduction, re-oxidation and re-reduction were observed in detail using microstructural observations and systematically compared with the dimensional change behavior. For the dimensional change behavior, a simple model considering the initial porosity and Ni content is proposed, which successfully predicts the dimensional change due to re-oxidation. Furthermore, Ni(O)–YSZ cermets with high Ni content show large initial dimensional changes, but the dimensional reversibility improves with increase of the number of redox cycles.

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