C/ C 复合材料CVD 过程中气相反应分析

以整体毡为预制体,丙烷为碳源,以沉积温度和气体滞留时间为考察变量,采用CVD 法制备了 C/ C 复合材料,并用偏光显微镜分析了热解碳结构,用气相色谱仪分析了尾气成分,并采用商用COMSOL 软件 分析了1 250 K 以上成碳过程的中间气相产物和气相反应路径。结果表明:试样上下表面热解碳均为光滑层 结构,高温下主要中间产物有H2、C2H2、C2H4、CH4,其中大分子结构、H2、C2H2 浓度,随着温度的升高而增大, C2H4 浓度随着温度的升高迅速减小,CH4 浓度略有减小;具有较低C—H 结合能而容易形成稳定的自由基的 大分子浓度随滞留时间延长而先增加后下降,具有高不饱和结构的大分子随滞留时间的延长浓度变化不大;热 解碳形成的复杂过程中C2H4 具有重要的作用。

Analysis on Gaseous Reaction of CVD Process During Preparation of

C/ C composites were prepared by chemical vapor deposition. During the process integral felt and propane were used as perform and carbon source separately. Emphases were focused on temperature and residual time. The microstructure was observed by polarizing microscope, and the exhausts were detected by gas chromatograph. A commercial software COMSOL was used to study the intermediate gases and reaction path. Results indicated that the as-prepared pyrocarbon was characterized by smooth laminar structure. H2,C2H2,C2H4,CH4 were majority of the intermediate gases during deposition. Macro-molecule and H2 are increased by increasing of the temperature. C2H4 is quickly decreased by increasing of the temperature. Macro-molecules with low C-H bended energy are easy to form free radicals and the contents would first increase then decrease with increase of residual time. Contents of macro-molecules with unsaturated structures changed slowly. C2H4 played an important role during the whole deposition process.