C/C-SiC composites were prepared by the combined process of chemical vapor infiltration (CVI) and gaseous silicon infiltration (GSI) using C/C green body with the density of 1 .0g/cm3 . Effect of CVI C/C-SiC intermediate composites' density on the phase composition ,microstructure and mechanical properties of CVI-GSI C/C-SiC composites was studied .The results show that as the CVI C/C-SiC intermediate composites' density increases ,the residual C content increases and residual Si content decreases in the CVI-GSI C/C-SiC composites ,the SiC content increases first and then decrea-ses ,and the density of CVI-GSI C/C-SiC composites increases first and then decreases;as the CVI C/C-SiC in termediate composites' density is increased from 1 .27g/cm3 to 1 .63g/cm3 ,the mechanical properties of CVI-GSI C/C-SiC composites increase at first ,which then decrease with the further in-creasing of CVI-C/C-SiC composites' density .Specifically ,when the CVI C/C-SiC composites density is 1 .42g/cm3 ,the prepared CVI-GSI C/C-SiC composites has the best mechanical properties ,with flexure strength ,flexure modulus and fracture toughness of 247 .50MPa ,25 .63GPa and 10 .08MPa · m1/2 , respectively .%采用密度为1.0g/cm3的C/C素坯,联合化学气相渗透(CVI)和气相渗硅(GSI)2种工艺制备C/C-SiC复合材料,研究CVI C/C-SiC复合材料中间体的密度对CVI-GSI C/C-SiC复合材料物相组成、微观结构及力学性能的影响.结果表明:随着CVI C/C-SiC复合材料中间体密度的增大,CVI-GSI C/C-SiC复合材料C含量增多,残余Si含量减少,SiC含量先增多后减少,CVI-GSI C/C-SiC复合材料的密度先增大后减小;随着CVI C/C-SiC复合材料中间体的密度由1.27g/cm3增加到1.63g/cm3时,得到的CVI-GSI C/C-SiC复合材料的力学性能先升高后降低.当CVI C/C-SiC复合材料密度为1.42g/cm3时,制得的CVI-GSI C/C-SiC复合材料力学性能最好,其弯曲强度为247.50M Pa,弯曲模量为25.63GPa,断裂韧度为10.08MPa·m1/2.
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