素坯密度对气相渗硅制备C/C-SiC复合材料结构与性能的影响  

Effects of Preform Density on Structure and Property of C/C-SiC Composites Fabricated by Gaseous Silicon Infiltration

作　　者：曹宇[1] 刘荣军[1] 曹英斌[1] 龙宪海[1] 严春雷[1] 张长瑞[1] 

机构地区：[1]国防科学技术大学航天科学与工程学院,长沙410073

出　　处：《材料工程》2016年第7期19-25,共7页Journal of Materials Engineering

基　　金：国防科学技术大学科研计划资助项目(JC14-01-04)

摘　　要：三维针刺碳毡经化学气相渗透(Chemical Vapor Infiltration,CVI)增密制备C/C素坯,通过气相渗硅(Gaseous Silicon Infiltration,GSI)制备C/C-SiC复合材料。研究素坯密度与CVI C层厚度及素坯孔隙率的变化规律,并分析素坯密度对C/C-SiC复合材料力学性能、热学性能的影响。结果表明:随着素坯密度增大,CVI C层变厚,孔隙率减小;C/C-SiC复合材料中残C量随之增大,残余Si量随之减小,SiC先保持较高含量(体积分数约40%),随后迅速降低,C/C-SiC复合材料密度逐渐减小,力学性能先增大后减小,而热导率及热膨胀系数降低至平稳。当素坯密度为1.085g/cm3时,复合材料力学性能最好,弯曲强度可达308.31MPa,断裂韧度为11.36MPa·m1/2。研究发现:素坯孔隙率较大时,渗硅通道足够,残余硅多,且CVI C层较薄,纤维硅蚀严重,C/C-SiC复合材料力学性能低;素坯孔隙率较小时,渗硅通道很快阻塞,Si和SiC含量少,而闭孔大且多,C/C-SiC复合材料力学性能也不高。The 3-D needled C/C preforms with different densities deposited by chemical vapor infiltration（CVI）method were used to fabricate C/C-SiC composites by gaseous silicon infiltration（GSI）.The porosity and CVI C thickness of the preforms were studied,and the effects of preform density on the mechanical and thermal properties of C/C-SiC composites were analyzed.The results show that with the increase of preform density,the preform porosity decreases and the CVI C thickness increases from several hundred nanometers to several microns.For the C/C-SiC composites,as the preform density increases,the residual C content increases while the density and residual Si content decreases.The SiC content first keeps at a high level of about 40%（volume fraction）,which then quickly reduces.Meanwhile,the mechanical properties increase to the highest values when the preform density is 1.085g/cm3,with the flexure strength up to 308.31 MP and fracture toughness up to 11.36MPa·m1/2,which then decrease as the preform density further increases.The thermal conductivity and CTE of the composites,however,decrease with the increase of preform density.It is found that when the preform porosity is too high,sufficient infiltration channels lead to more residual Si,and thinner CVI C thickness results in the severe corrosion of the reinforcing fibers by Si and lower mechanical properties.When the preform porosity is relatively low,the contents of Si and SiC quickly reduce since the infiltration channels are rapidly blocked,resulting in the formation of large closed pores and not high mechanical properties.

关 键 词：C/C素坯 气相渗硅 C/C-SIC CVI C 力学性能 

分 类 号：TB332[一般工业技术—材料科学与工程]