C/C多孔体对C/C-SiC复合材料微观结构和弯曲性能的影响

以4种纤维含量相同(32%,体积分数,下同),用化学气相渗透(chemical vapor infiltration,CVI)法制备了4种密度的碳纤维增强碳(carbon fiber reinforced carbon,C/C)多孔体,基体炭含量约20%～50%.利用液相渗硅法(liquid silicon infiltration,LSI)制备了C/C-SiC复合材料,研究了C/C多孔体对所制备的C/C-SiC复合材料微观结构和弯曲性能的影响.结果表明:不同密度的C/C多孔体反应渗硅后,复合材料的物相组成均为SiC,C及单质Si;随着C/C多孔体中基体炭含量的增加,C/C-SiC复合材料中SiC含量逐渐减少而热解炭含量逐渐增加.C/C-SiC复合材料弯曲强度随着材料中残留热解炭含量增加而逐渐增加,热解炭含量为约42%的C/C多孔体所制备的C/C-SiC复合材料的弯曲强度最大,达到320 MPa.

EFFECT OF C/C POROUS PREFORM ON THE MICROSTRUCTURE AND FLEXURAL STRENGTH OF C/C-SiC COMPOSITES

Carbon fiber reinforced silicon carbide matrix (C/C-SiC) composites were prepared by liquid silicon infiltration (LSI) process, using four kinds of quasi-three dimensional C/C preforms with the same fiber volume faction (32%) but different pyrocarbon content (from ～20% to ～50%, in volume) filled by chemical vapor infiltration. The microstructure and flexural strength of C/C-SiC composites have been investigated. XRD analysis results show the composites are composed of three phases of β-SiC, C and Si. With the increase of the pyrocarbon content in the C/C preforms, the content of formed silicon carbide in the C/C-SiC composites decreases but the residual pyrocarbon increases. Flexural test was performed to assess the role of the matrix in the C/C-SiC compo- sites. The results demonstrate that the flexural strength of the composite increases gradually as the increase of the content of residual pyrocarbon. The bending strength of the C/C-SiC composite produced of the C/C preform with pyrocarbon content of ～42% is the highest of 320 MPa.