CVI热解炭微观结构的参数控制研究

Research on Parameter of Preparation of Pyrocarbon with Chemical Vapor Infiltration

化学气相渗透(CVI)制备炭/炭复合材料涉及气体扩散和气相沉积2个过程,其工艺控制决定炭纤维坯体的增密速度、热解炭的结构和炭/炭材料的性能。工艺过程的控制主要有4类参数:第一参数包括沉积温度、系统压力、碳源浓度、碳源分压等,第二参数包括均相反应、异相反应和滞留时间等,第三参数为As/VR,也就是沉积基体的表面面积与炉内气体的自由体积之比,以及目前以计算机模拟为主要手段的"第四参数"的研究。在固体表面沉积热解炭的科学研究已经持续了几十年,但至今为止还没有形成一种完善的表面沉积机理,分析了CVI工艺参数发展的趋势,说明了对热解炭微观结构形成机理的认识是一个不断深入的过程。

Carbon/carbon composites are usually manufactured by chemical vapor infiltration（CVI） process consisting of the gas diffusion and deposition kinetics. Processes control is very important to affect the microstructure of pyrocarbon and the densification rate of carboneous performance. The types of progress parameter in preparation of pyrocarbon with chemical vapor infiltration are reviewed briefly. Four phases of development are recommended. The first parameter includes deposition temperature, furnace pressure, hydrocarbon gas concentration and hydrocarbon gas partial pressure, etc. The second parameter includes homogeneous reaction, heterogeneous reaction and residence time, etc. The third parameter is As/VR, which is the ratio of surface area of deposition substrate to free volume of reaction gas in the furnace and ＇the fourth parameter＇ which is being studied by numerical simulations of CVI processes. Carbon deposition from the gas phase on solid substrate has been an object of scientific research for several decades. The trend of development of progress parameter is analyzed. It shows that understanding the deposition mechanism of py rolytic carbon is a long course.