石墨化处理对不同高织构含量C/C复合材料微结构的影响

Effect of heat treatment on the microstructure of C /C composites with different high textured pyrolytic carbon contents

采用化学气相沉积工艺制备出炭毡增强炭/炭(C/C)复合材料和3K炭布叠层增强C/C复合材料,并对材料进行2500℃高温石墨化处理。利用X射线衍射仪;偏光显微镜及拉曼光谱仪对所制材料进行表征。结果表明,炭毡C/C复合材料基体是单一的高织构(HT)热解炭,3K炭布叠层C/C复合材料的基体是带状组织,从纤维表面向外依次为各向同性热解炭、HT和中织构(MT)热解炭,其中HT含量低于50%;沉积态和热处理后,两种C/C复合材料都具有相似的石墨化度,且热处理后的石墨化度超过80%,但Lc值差异明显,炭纤维、MT和HT热解炭的La值均升高,其中HT热解炭升幅明显大于炭纤维和MT热解炭。HT热解炭的含量是导致这两种C/C复合材料具有相似石墨化度而Lc值却显著差异的原因。

C/C composites reinforced using carbon felt and 3 K carbon cloth laminated preforms were prepared by chemical vapor infiltration and samples taken from them were subsequently subjected to heat treatment at 2500℃. The microstructures of the C/C composites were characterized by X-ray diffraction, polarized light microscopy and Raman spectroscopy. Results showed that the matrix of composites reinforced with carbon felt contained only high textured （ HT） pyrolytic carbon, while those reinforced with the 3 K carbon cloth had a banded texture composed of isotropic, HT and medium textured （ MT） pyrolytic carbon when moving from fibers to matrix, and the content of HT pyrolytic carbon was less than 50%. Regardless of the preform, both the as-prepared and heat-treated composites had a similar degree of graphitization. The Lc value of the carbon felt-reinforced composites was higher than their counterparts both for the as-prepared and heat-treated samples. The La values of the carbon fibers, MT and HT pyrolytic carbon increased after the heat treatment, and the La value of the HT pyrolytic carbon had a much larger increase than that of the others.