Influence of process on the structure and properties of C/SiC composites

Carbon felt reinforced SiC ceramic matrix composites was used as lightweight mirror substrate for its macroscopical isotropy characteristic. The combined process of chemical vapor infiltration and precursor infiltration pyrolysis (CVI-PIP) was introduced to prepare C/SiC ceramic matrix composites and the profile and surface morphology of C/SiC composites were observed by SEM. The strength and elastic modulus of C/SiC composites prepared by different process were measured. The result shows that the densification efficiency of CVI process is higher than that of PIP process during the forepart of densification process; Compared with the C/SiC composites prepared by PIP process entirely, the densification rate and degree of C/SiC composites are improved largely by CVI-PIP process and the residual porosity of C/SiC composites decreased from 18.86% to 5.45% Correspondingly, the strength and elastic modulus of the C/SiC composites are improved obviously, from 66.43 MPa and 38.43GPa to 112.16 MPa and 68.49 GPa respectively; The combination property between the C/SiC composites and chemical vapor deposition(CVD) SiC coating was also increasing by CVI-PIP process.