THERMAL-SHOCK BEHAVIOR OF ADVANCED CERAMIC/COMPOSITE HOT-GAS FILTERS

摘要

The thermal shock/fatigue behavior of monolithic and composite hot-gas candle filters obtained from various manufacturers was evaluated. The composite filters were made of both oxide and nonoxide materials; the monolithic filters were made only of nonoxide materials.During single-cycle thermal shock tests, composite filters show little or no strength degradation when quenched from temperatures between 900 and 1000 deg C. At higher quenching temperatures, slow strength degradation was observed. Regular monolithic SiC filters showed no strength degradation when quenched from temperatures up to approx =700-900 deg C, whereas at higher quenching temperatures, the strength decreased at a relatively sharper rate. On the other hand, recrystallized monolithic SiC filters showed higher initial strength and retained this strength to higher quenching temperatures when compared with regular SiC filters. This finding may be related to the difference in the strength of grain boundary phases in the two filters. For thermal cycles between room temperature and 800-1000 deg C, composite filters show little (18-24 percent) strength degradation up to three cycles, beyond which the strength remains unchanged. Similar behavior, with an initial strength drop of 15-28 percent, was observed for monolithic filter specimens that were thermally cycled between room temperature and 800 deg C.