耦合物理场CVI制备炭/炭复合材料及其机理

用液化石油气作碳源、炭毡作增强体,在坯体中埋置导电层诱导产生温度场和电磁场梯度,在自行设计的多元耦合物理场CVI炉中制备C/C复合材料,用偏光显微镜观察热解炭的显微结构,用XRD表征了材料的石墨化度和微晶尺寸等结构参数,所有样品均为一次性沉积所得,其增密曲线是采用把坯体密度与在线电阻进行拟合所得.研究了沉积温度、碳源气体分压对增密速度和材料结构的影响;并对物理场的耦合机理和热解炭的沉积机理作了探讨.研究表明,多元耦合物理场CVI工艺增密速度快,沉积20h,试样的密度达到1.71g/cm³;除了能获得中等织构的光滑层(SL)和带状结构的热解炭,还可获得高织构的粗糙层结构(RL)热解炭,在2300℃、2h热处理后,其石墨化度达到77%以上.

Preparation of C/C Composites by CVI with Multi-factor Coupling Physical Fields and Deposition Mechanism

in the felt forming the grads of temperature and electromagnetism, C/C composites were fabricated by chemical vapor infiltration (CVI) with multi-factor coupling physical fields. The textures of pyrolytic carbon were observed by a polarization microscope(PLM), and the graphitization degree and minicrystal size of the C/C composites were analized by XRD. All samples were fabricated at one cycle. The densities of the matrix were measured by on-line coupling with resistance.At last,the mechanism of multi-factor coupling physical fields and deposition of carbon was discussed. The results show that, with multi-factor coupling physical fields, the rate of deposition of pyrolytic carbon can be improved greatly, and when deposited for 20h, C/C composites with densities of more than 1.7g/cm³ will be obtained. Through optimizing the infiltration conditions, some microstructures of pyrolytic carbon can be obtained ,range from rough laminar,smooth laminar, and banded structure. The graphitization degree of the rough laminar can be over 77% after heat treatment at 2300℃ for 2h.