Effect of Ceramic Filler Particles on the Sealing Capability of a SrO-based Glass Seal

Abstract

The nano-sized YSZ and nano-sized Al2O3 powders were added to a SrO-Al2O3-B2O3-SiO2 glass system to control the effective viscosity and glass retention. Added filler particles evidently improved glass retention. YSZ/glass composites hardly devitrified after heat treating at 800 degrees C for 100 hours but Al2O3/glass composites easily devitrified. The devitrified phase, SrAl2Si2O8, decreased the CTE of Al2O3/glass composite to 5.6x10(-6) /degrees C. Corrosion of Crofer22/APU was more severe due to contact with Al2O3/glass composite than with YSZ/glass composite. YSZ composite/glass showed the reliable sealing capability in long-term operation and repeated thermal cycles while the sealing of Al2O3/glass composite failed during thermal cycling. Such failure of Al2O3/glass composite was caused not only by the large thermal mismatch between Crofer22APU jig and sealing tape but also by intensifid corrosion of Crofer22APU.