High-temperature mechanical properties of NextelTM 610 fiber reinforced silica matrix composites

Novel Nextel™ 610 fiber reinforced silica (N610f/SiO2) composites were fabricated via sol-gel process at a sintering temperature range of 800-1200 °C. The sintering-temperature dependent microstructures and mechanical properties of the N610f/SiO2 composites were investigated comprehensively by X-ray diffraction, nanoindentation, three-point bending etc. The results suggested a thermally stable Nextel™ 610 fiber whose properties were barely degraded after the harsh sol-gel process. A phase transition in the silica matrix was observed at a critical sintering temperature of 1200 °C, which led to a significant increase in the Young's modulus and hardness. Due to the weak fiber/matrix interfacial interaction, the 800 °C and 1000 °C fabricated N610f/SiO2 composites exhibited quasi-ductile fracture behaviors. Specially, the latter possessed the highest flexural strength of ≈ 164.5 MPa among current SiO2-matrix composites reinforced by fibers. The higher sintering-temperature at 1200 °C intensified the SiO2 matrix, but strengthened the interface, thus resulting in a brittle fracture behavior of the N610f/SiO2 composite. Finally, the mechanical properties of this novel composite presented good thermal stability at high temperatures up to 1000 °C.