Mechanical property and microstructure evolutions of Cf/SiOC composites with increasing annealing temperature in reduced pressure environment

Three-dimensional (3D) carbon fiber reinforced silicon oxycarbide (Cf/SiOC) composites were fabricated through precursor impregnation and pyrolysis process using siloxane resin as precursor. These composites were further annealed at various temperatures to follow their mechanical properties and microstructure evolutions in reduced pressure environment. The decrease in strength of those composites could be attributed mainly to the decomposition of matrixes. When the annealing temperature increased from 1000 to 1250 °C, the mechanical properties of composites did not change too much, despite the matrixes underwent a redistribution of Si–O bonds and Si–C bonds. At temperature above 1300 °C, due to the weight loss and volume shrinkage of matrixes caused by carbothermal reduction, both the flexural strength and elastic modulus of Cf/SiOC composites decreased rapidly.