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This paper presents an acoustic emission (AE) method for detecting the mechanical damage in anode-supported cells (ASCs). Start/stop cycle tests (between RT and 800°C) were carried out using single cells. After 2 cycle start/stop cycles, no damage was induced in the cells and their electrical performances were maintained without degradation. The experimental results indicated that the AE technique employed in this study allowed us to distinguish the damages in the cells from the cracking in the glass seals. In addition to this result, the mechanical damages during redox treatments were evaluated using the AE technique. The electrochemical evaluation performed concurrently with the redox treatments demonstrated the validity and significance of AE monitoring for detecting mechanical damages in SOFCs.

The effects of through‐thickness pinholes in an electrolyte on re‐oxidation and mechanical damage of anode‐supported solid oxide fuel cells are discussed in this paper. Pinholes with a dimension greater than approximately 10 μm were detected by dye penetrant inspection using half‐cells fabricated through a co‐sintering method. In single cells with such pinholes, the leakage of oxygen occurred through the through‐thickness pinholes under open‐circuit voltage (OCV) conditions when the fuel supply was discontinued. The oxygen leakage caused the oxidation of Ni in the anode, forming semicircular re‐oxidized regions on the electrolyte side of the anode substrate. The oxygen permeation fluxes in the electrolyte, which were deduced from the measured reduction in OCV during the operation of fuel shut‐off, are shown to correlate well with the time elapsed from the shut‐off of the fuel gas supply to the onset of mechanical damage monitored by acoustic emissions. The correlation indicates that the oxidation rate of the anode substrate is accelerated due to the presence of pinholes in the electrolyte, which can result in mechanical damages.

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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.