Preparation and interface modification of Si3N4f/SiO2 composites

In order to modify the interface, SiON coating was introduced on the surface of silicon nitride fiber by perhydropolysilazane conversion method. Si3N4f/SiO2 and Si3N4f/SiONc/SiO2 composites were prepared by sol-gel method to explore the influence of SiON coating on the mechanical properties of composites. The results show that with the protection of SiON coating, Si3N4 fiber enjoys a strength increase of up to 24.1% and Si3N4f/SiONc/SiO2 composites have a tensile strength of 170.5 MPa and a modulus of 26.9 GPa, respectively. After 1000 degrees C annealing in air for 1 h, Si3N4f/SiONc/SiO2 composites retain 65.0% of their original strength and show a better toughness than Si3N4f/SiO2 composites. The improvement of mechanical properties is attributing to the healing effect of SiON coating as well as its intermediate coefficient of thermal expansion between Si3N4 fiber and SiO2 matrix. (C) 2019 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.