C／C复合材料的显微结构及其与工艺、性能的关系

对化学气相渗透（CVI）C／C复合材料在偏振光下的显微结构（偏光显微结构）类型、结构的形貌特征及对应炭的基本物理性能、材料的制备工艺参数－结构－性能之间的关系进行了综述。C／C复合材料具有三种基本偏光显微结构，即RL、SL和ISO。这三种基本偏光结构的炭对应于不同的形貌特征，可从消光十字形、旋光性、光学反射性、生长特征、表面织构、择优取向性和环形裂纹等特征将其分辨出来。工艺参数对沉积炭偏光显微结构的影响没有一成不变的规律可循，影响因素除了温度、压力、气体成分、气体流速外，还与炉子的几何尺寸及试样的堆积尺寸有关，对不同的CVI体系，都应当摸索出一套适合其运行的最佳工艺参数。C／C复合材料的偏光显微结构与材料的性能有着密切的联系，不同的结构下，材料的物理性能、力学性能和热性能都表现出明显的差异。通过归纳与分析，获得了对C／C复合材料偏光显微结构全面、系统的认识，明确了它在C／C复合材料研究中的重要性，为制备具有单一、均匀偏光显微结构及所需性能的C／C复合材料指明了方向。

THE RELATIONSHIP AMONG MICROSTRUCTURES,PROCESSING PARAMETERS AND PROPERTIES FOR CARBON-CARBON COMPOSITES

Various kinds of microstructures under polarized light for carbon carbon composites made by Chemical Vapor Infiltration (CVI) were discussed, with its appearance features and the basic physical properties of the corresponding matrix pyrolytic carbon, the relationship between processing parameters, microstructures and material properties were summarized. There are three kinds of basic microstructures under polarized light illumination on C/C composite, i.e. RL, SL and ISO. Due to the different optical morphological characteristics, the carbons with these kinds of basic microstructures can be distinguished by its characteristics of extinction crosses, optical activity and reflectivity, growth features, surface texture, preferred orientation and circumferential cracks etc. There are no invariable regularities to follow with the effect of processing parameters on microstructures of deposited carbons under polarized light illumination during the CVI process, it is not only influenced by temperature, pressure, gas composition and flow rate, but also affected by geometric sizes of furnaces and packing sizes of specimens. A set of optimal processing parameters must be explored for different CVI deposition systems, which matches them well respectively. The properties of C/C composites are considerably decided by its microstructures under polarized light illumination, such as physical, mechanical and thermal properties. All these are the most important basic knowledge to fabrication of a carbon carbon composite, which has certain type of homogeneous polarized microstructure and the properties that are expected.