Sintering Temperature and Interphase Effects on Mechanical Properties of an Oxide Fiber-Reinforced Al2O3-SiO2 Composite Fabricated by Sol–Gel Method

Three-dimensional Nextel™ 440 fiber-reinforced Al2O3-SiO2 matrix (N440/Al2O3-SiO2) composites were fabricated by sol–gel method with sintering temperature from 1100 °C to 1400 °C. The interface engineering of the composites was carried out by employing PyC and FC interphase. The microstructure and mechanical properties of the composites were investigated. Results showed that the sintering temperature had remarkable effects on the mechanical properties of the composites. The average flexural strength of the composite without interphase decreased as the temperature increased, with fracture behaviour changing from ductile to brittle, and the highest flexural strength of 90.0 MPa was obtained for the composite fabricated at 1100 °C. However, the flexural strength of the composite with PyC interphase increased initially and then decreased, with fracture behaviour remaining ductile, and the highest flexural strength of 116.3 MPa was obtained for the composite fabricated at 1300 °C. Moreover, PyC and FC interphase could effectively weaken the interfacial bond strength and efficiently promote load transfer, thus improving the strength. For the composite fabricated at 1300 °C, the average flexural strength significantly increased after introducing the optimised PyC and FC interphase.