Research About Preparation Of Anti-oxidation Coating By Sol-gel Method For Carbon-carbon Composites

C/C composites are carbon matrix composite materials with carbon fiber as reinforcing phase.They have a series of excellent properties such as high strength,high modulus,low density,friction resistance,ablation resistance and many other excellent properties.However,the results show that the C/C composites begin to oxidize when the temperature exceeds 370?;When the temperature exceeds 500?,the oxidation rate will accelerate,the poor oxidation resistance under aerobic and high temperature conditions seriously limits the application of C/C composites.Among the numerous methods for improving and improving the oxidation resistance of C/C composites,the coating method is currently recognized as the most effective antioxidant means.The sol-gel method has the advantages of simple operation,low cost and large area for preparing the coating.The sol-gel method is widely used for preparing the anti-oxidation coating.In this paper,ZrO2 coating,ZrO2-SiO2 coating and ZrO2-SiO2-SiC coating were prepared by sol-gel method.The effects of sol-gel,The structure and properties of the anti-oxidation coating were tested and characterized by SEM,XRD,FT-IR,DSC-TG and so on.In contrast to the sol-gel method,the sol-gel and pack cementation method were used to prepare the corresponding anti-oxidation coating of ZrO2-SiO2-SiC,the.differences in performance of the anti-oxidation coatings prepared by different methods are compared.It was found that the concenttation of the sol had a great influence on the SiC coating prepared by the sol-gel method.The obtained coating had a thickness of about 100 nm and covered the surface of the C/C composites uniformly.The initial oxidation temperature of the C/C composites increased about 180?,but the surface defects such as micropores and cracks.Therefore,ZrO2-SiO2-SiC composite coating was prepared on the basis of SiC coating.The coating was more uniform and compact and the mass loss rate of C/C composites was 9.3%after being oxidized at 1000? for 60min.The ZrO2-SiO2-SiC composite coating prepared by two-step sol-gel and pack cementation process was oxidized in air at 1000? for 360min,the mass loss rate was 20%,showing excellent oxidation resistance.