Degradation behavior of SiO2f /Al2O3-SiO2 composites: Anti-oxidation behavior and high-temperature flexural strength

2.5-Dimensional SiO(2 )fiber-reinforced Al2O3-SiO2 (SiO2f/Al2O3-SiO2) composites were prepared by the sol-gel method, using diphasic SiO(2 )sol as the precursor into which Al(2)O(3 )powders were added. Their antioxidative behaviors and flexural strengths at high temperature were tested and compared. In an oxidation atmosphere, the composites showed high oxidation resistance, with a flexural strength retention ratio of over 90.00% at 1200 degrees C. After oxidation at 1500 degrees C, the mass retention ratio and flexural strength were 97.49% and 65.0 MPa respectively. The oxidation resistance of SiO2f /Al2O3-SiO(2 )composites was higher than that of SiO2f/SiO(2 )composites. After high-temperature test, the flexural strength retention ratios of SiO (2f)/SiO (2 )and SiO2f/Al2O3-SiO2 composites were 86.18% and 94.80% respectively, and the latter had a flexural strength of 134.9 MPa. SiO2f/Al2O3-SiO(2 )composites worked better than SiO2f/SiO(2 )composites did in the flexural strength test at 1200 degrees C. The mechanical performance degradation and mass variations of the composites during tests were closely associated with their microstructural evolutions.