Preparation And Properties Of C/C-ZrC Composite Materials

In order to meet the requirements of thermal protection materials for the thermal structural components of the new generation of aircraft and to improve the oxidation resistance and ablation resistance of C/C composites,the C/C-ZrC composites were prepared by introducing ZrC ceramic components into the C/C composites matrix quickly and efficiently by reactive melting infiltration process based on C/C composites.By characterizing the properties of C/C composite body,the melt-infiltration effect of C/C body with different densities and different structures was studied.The influences of fine woven carbon fiber preforms,deposited carbon matrix and asphalt carbon matrix on the microstructure,mechanical properties,thermophysical properties and ablation properties of C/C-ZrC composites prepared by RMI method were discussed.The main research contents and results are as follows:Firstly,the influence of C/C composite fabric structure and process method on the pore structure of the blank body was studied.The pore structure and densification of C/C composite fabric were studied in detail,and the effect of preparation technology on the pore structure and distribution of the blank body was explored.It is found that the pores in the blank body can be divided into two types:millimeter scale pores and micron scale pores.The millimeter-scale pores are mainly affected by the type of carbon fiber preform used in the blank body,while the micron-scale pores are mainly affected by the type of carbon introduced into the matrix.The average pore size of the micron-scale pores in the asphalt carbon matrix is smaller.The millimeter scale pores determine the content of ZrC in C/C-ZrC composites.Micron scale pores determine the final porosity and average pore size of C/C-ZrC composites.Secondly,the influence of the characteristics of C/C composite body on the density,microstructure and ceramic phase content of C/C-ZrC composite was analyzed.It was found that after two rounds of asphalt impregnation and carbonization,the needle structure with a density of about 1.2 g·cm^-3 had the best penetration effect on C/C green body.After one round of asphalt impregnation and carbonization,the C/C body of fine woven puncture structure has the best penetration effect.The mass fraction of ZrC in the materials prepared with asphalt carbon matrix is higher.Finally,the relationship between the preparation process,microstructure,mechanical properties and ablation properties of C/C-ZrC composites was studied,and the factors affecting the material properties were analyzed.The results show that the C/C-ZrC composites prepared by needle-pruning structure have smaller deflection,higher bending modulus,lower fracture stress,and lower bending strength than the C/C-ZrC composites prepared by needle-pruning structure.The mechanical properties of C/C-ZrC composites prepared by introducing carbon matrix are better.The thermal expansion coefficient of C/C-ZrC composites increases with the increase of temperature and reaches a maximum of6.63×10-6·k^-1 at 1000?.The thermal diffusion coefficient decreases with the increase of ZrC content and decreases with the increase of temperature.The specific heat capacity decreased with the increase of ZrC content and increased with the increase of temperature.The thermal conductivity decreases with the increase of ZrC content and decreases with the increase of temperature.The thermal conductivity decreases from 39.67 W·m^-1·K^-1 at room temperature to 18.55 W·m^-1·K^-1at 1200?.The C/C-ZrC composites prepared by the needle-pruning structure show excellent ablation resistance,and the linear ablation rate of the C/C-ZrC composites prepared by the needle-pruning structure is lower.The ablation rate of C/C-ZrC composites with carbon matrix is lower and the ablation performance is better.The ablation performance of C/C-ZrC composites can be improved by properly increasing the ZrC mass fraction in the composites.