中文摘要：

在CVD增密前对预制体炭纤维进行表面硝酸氧化处理,研究不同浓度硝酸、不同氧化处理时间对炭纤维表面结构状态的影响,以及最终对CVD热解炭微观结构的作用及机理。研究结果表明：对炭纤维表面用质量分数为66%浓硝酸处理时,炭纤维表面形成沿纤维轴向的沟槽;随着处理时间的延长,沟槽先加深后减弱,经40 min处理后炭纤维表面刻蚀沟槽最均匀;预制体经不同硝酸质量分数（66%,33%和22%）处理40 min后进行CVD沉积得到C/C复合材料,其中经33%硝酸处理的样品中所沉积的热解炭微观有序度最高,且近炭纤维表面处热解炭有序度最高,由内至外有序度逐渐降低;在优化处理条件下,纤维表面氧化刻蚀均匀,表面所形成的含氧官能团（羰基和羧基）有效诱导了CVD过程中热解炭在纤维表面的有序沉积。

英文摘要：

Nitric acid oxidation was performed on carbon fibers before CVD.The effects of nitric acid oxidation on carbon fibers and the microstructure of pyrocarbon were studied.The results show that the grooves on fiber surface deepen first and then weaken with the increase of oxidation time during the oxidation by 66% nitric acid.The surface etch of carbon fibers treated for 40 min is uniform.The performs treated by nitric acid（66%,33%,22%） for 40 min are dandified by CVD.The microstructure of pyrocarbon in composite treated by 33% nitric acid is the best.The microstructure order degree of pyrocarbon decreases from the inside to the outside.The proper oxidation and etch on the fiber surface bring about certain oxygen functional groups such as carbonyl and carboxyl,which induce the ordered deposition of pyrocarbon during CVD.