Preparation and interface modification of Si3N4f/SiO2 ceramic matrix composites

Abstract

Abstract In order to meet the overall performance of high temperature resistant and transmitted materials for electromagnetic windows of hypersonic aircraft. In this study, Si3N4f/SiO2 ceramic matrix composites were prepared by sol-gel process. After 5 process cycles, the materials were prepared with the best comprehensive performance, with a density of 1.79 g/cm3, a bending strength of 149 MPa, a tensile strength of 82.1 MPa, a dielectric constant of 3.52, and a tangent of the dielectric loss of 0.004. The effects of Al2O3 and LaPO4 interface coatings on the mechanical properties of composites were studied. At room temperature, the interface coating has little effect on the bending properties of the material, and the bending strength of the Al2O3 interface coating composite at 1200°C remains basically unchanged. Compared with the sample without interface coating, the strength retention rate is increased by about 16%. LaPO4 coating had no obvious influence on the bending property of the material at 1200°C.