Production of the SiC/C Functionary-Gradient Material by the Chemical Vapor Infiltration Method and its Process Modeling

为了缩短SiC/C梯度功能材料（FGM）的制备时间，防止FGM表面剥落，采用化学气相渗透法（CVI）制备了纤维增强的FGM。1，1，2-三氯乙烷和二甲基二氯硅烷分别用于形成碳和碳化硅。用X射线显微分析仪测量了硅原子在功能梯度材料中的分布。建立了CVI法制备功能梯度材料的数学模型。使用在独立实验中确定的碳和碳化硅沉积的反应速率方程进行模拟。实验和计算结果之间的比较表明，生长速率大大降低时，碳和碳化硅共沉积，并在功能梯度材料中的碳化硅的成分是低于通过数值模拟估计。因此，通过使用窄管热CVD反应器进行碳和碳化硅的共沉积的动力学分析。发现当碳同时沉积时，碳化硅的生长受到阻碍。当将加热器安装在反应室内时，碳沉积在加热器上，这降低了加热效率并且不允许稳定操作。因此，设计并建造了一种在真空室外部具有加热单元的新反应器。使用新的反应器，我们继续进行FGM生产实验。

The objective of this work is to shorten the production time of the SiC/C functionary-gradient material (FGM) and to prevent the surface peeling by producing the FGM by the chemical vapor infiltration (CVI) method.The fiber-reinforced FGM was produced using the specially designed reactor. 1,1,2-Trichloroethane and dimethyldichlorosilane were used to form carbon and silicon carbide, respectively. Distribution of silicon atom in the obtained FGM was measured by the X-ray micro-analyzer. The mathematical models were proposed to numerically simulate the FGM production by the CVI method. Simulations were carried out using the reaction rate equations of carbon and silicon carbide deposition that were determined in the independent experiments. Comparison between the experimental and calculated results indicated that the growth rate was greatly reduced when carbon and silicon carbide were co-deposited, and that the composition of silicon carbide in the FGM was lower than that estimated by the numerical simulation. Hence, kinetic analysis of the co-deposition of carbon and silicon carbide is carried out by use of the narrow-tube thermal CVD reactor. It was found that the growth of silicon carbide was hindered when carbon was deposited simultaneously.When the heaters were installed inside the reaction chamber, carbon was deposited on the heaters, which reduced heating efficiency and did not allow stable operation. Hence, a new reactor which has the heater unit outside the vacuum chamber was designed and constructed. Using the new reactor, we continue to carry out the FGM production experiments.