Developing and preparing interfacial coatings for high tensile strength silicon nitride fiber reinforced silica matrix composites

A three-dimensional silicon nitride fiber fabric with Pyrolytic carbon (PyC) interlayer reinforced silica matrix composites (Si3N4f/PyC/SiO2) were prepared by sol-gel method, and the mechanical properties of the composites were investigated. The tensile strength of Si3N4f/PyC/SiO2 composites at room temperature exceeded 73.8 MPa, and the tensile strengths at 1200 degrees C and 1400 degrees C were 60.9 MPa and 58.2 MPa, respectively. Compared with Si3N4f/SiO2 composites without PyC coating, the strength of Si3N4f/PyC/SiO2 composites improved significantly, particularly at high temperature. The experimental results show that PyC interlayer could protect silicon nitride fibers from high temperature interfacial reaction between fibers and matrix. Meanwhile, considerable fiber pull-out was observed throughout the fracture surface of Si3N4f/PyC/SiO2 composites indicating that the interface bonding was weak, which resulted in the high mechanical strength of Si(3)N(4)f/PyC/SiO2 composites.