Study on the Preparation of SiC Coating by Chemical Vapor Phase and the Mechanical Properties of Ceramic Matrix Composites

Abstract

In view of the oxidization-prone feature of C/C composites at high temperature, the effect of SiC ceramic coating on the structure and performance of the composites and the oxidation resistance of new nano-carbon particles/ silicon carbide ceramics are explored. The results show that the chemical vapor phase method applied in preparing SiC coated C/C composites can produce good coatings, which is large in coating thickness, uniform in distribution and good in combination with the matrix. The average bending strength of the SiC coated material is 40.4% higher than that of the original material, and the average maximum fracture displacement is increased by 9.26%. The vapor permeation and the enhanced interaction between SiC particles during the preparation of the SiC coating lead to the improvement of strength of the coated samples. After the coating, the fracture mode of the original material does not change fundamentally with the phenomena including interlayer debonding and fiber removal still occurring at the time of fracture, showing good damage resistance and pseudoplastic fracture characteristics. The oxidation process of the new Cp/SiC composite ceramics at 400-700°C is mainly controlled by C-O2 reaction, where the apparent porosity of Cp/SiC increases and the bending strength decreases. At 700-1100 °C, the SiC on the surface of the material is oxidized into SiO2 protective film with the apparent porosity decreased and the bending strength increased. The content of nano-carbon is the key factor affecting the strength and the complexity of oxidation of Cp/SiC composite ceramics. The SiC composite ceramics with 15% of nano-carbon has excellent oxidation resistance.