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

本研究的目的是为了缩短SiC/C功能梯度材料（FGM）的生产时间，并通过化学蒸汽渗透（CVI）法生产FGM，防止其表面剥落。采用特殊设计的反应器制备纤维增强FGM。用1,1,2-三氯乙烷和二甲基二氯硅烷分别生成碳和碳化硅。用x射线显微分析仪测定了所得FGM中硅原子的分布。提出了用CVI法数值模拟FGM生产过程的数学模型。利用独立实验中确定的碳化硅和碳沉积的反应速率方程进行了模拟。实验结果与计算结果的对比表明，碳与碳化硅共沉积大大降低了生长速度，且碳化硅在FGM中的组成低于数值模拟估算。因此，利用窄管热CVD反应器对碳与碳化硅共沉积过程进行了动力学分析。同时沉积碳会阻碍碳化硅的生长。当加热器安装在反应室内时，碳沉积在加热器上，降低了加热效率，不允许稳定运行。为此，设计并建造了一种真空室外加温装置的新型反应器。利用新反应器，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.