High-temperature mechanical properties of a glass sealant for solid oxide fuel cell

The high-temperature mechanical properties of a newly developed silicate-based glass sealant, designated as GC-9, have been studied for use in planar solid oxide fuel cell (pSOFC). Four-point bending tests were conducted at room temperature, 550 degrees C, 600 degrees C. 650 degrees C, 700 degrees C and 750 degrees C to investigate the variation of flexural strength, elastic modulus, and stress relaxation with temperature for the given glass sealant. Weibull statistic analysis was applied to describe the fracture strength data. The results indicated that the flexural strength was increased with temperature when the testing temperature was below the glass transition temperature (T-g, 668 degrees C). This was presumably caused by a crack healing effect taking place at high temperatures for glasses. However, with a further increase of temperature to a level higher than Tg, significant stress relaxation was observed to cause extremely large deformation without breaking the specimen. When the controlled displacement rate was increased by an order of magnitude, the stress relaxation effect at 750 degrees C became less effective. However, the mechanical stiffness of the given glass was significantly reduced at a temperature higher than T-g. (C) 2008 Elsevier B.V. All rights reserved.