The mechanical properties of tubular solid oxide fuel cells

The mechanical strength of solid oxide fuel cell (SOFC) components is one of the key issues for determining their performance and reliability. A minimum strength is required for the handling of these components in manufacturing, namely in relation to the application of the electrode or electrolyte coatings, the application of the current collection metals and the construction of the stack. Small tubular SOFCs have been found to have excellent thermal shock properties and low-cost of fabrication through traditional extrusion techniques. The mechanical integrity of the small, thin walled, tubular ceramics could be tested using traditional 3 or 4-point bending techniques, however these techniques are liable to cause failure by crushing the tube wall. Thus, a more reliable method for realizing the strength of small thin walled tubes is to pressurize the inside volume and obtain the strength value at which the tube bursts under the internal pressure. A custom burst-test instrument was constructed to obtain the average strength value of differing types of small ceramic tubes. The mechanical properties of 8 mol% yttria-stabilized zirconia (8YSZ) and NiO-YSZ tubes were investigated and are discussed. An average burst strength of 97 ± 28 MPa was observed for 8YSZ electrolyte tubes and 72 ± 23 MPa and 70 ± 16 MPa for as-sintered and reduced anode support tubes, respectively.