工艺参数对CVI-TaC沉积速率的影响

Influences of process parameters on deposition rate of CVI-TaC

利用TaCl5-Ar-C3H6-H2反应体系,采用化学气相渗透(CVI)法在炭毡中沉积TaC,并研究了CVI工艺参数如气体流速、滞留时间、沉积温度、沉积压力和H2的加入等对碳化钽在炭毡中沉积速率(用炭毡质量分数的增加来表示)的影响。研究表明:CVI-TaC受表面反应控制的最大气体流速为40 cm/s,最小滞留时间为1.2 s;沉积速率与沉积温度之间的关系不符合Arrhenius方程,沉积速率随沉积温度的升高先增加后减小,在950℃时达到最大值;在1 000℃时,CVI过程受孔隙扩散所控制;沉积速率随沉积压力的升高以及H2的加入而急剧增加。

TaC was deposited by chemical vapor infiltration（CVI） method with TaCl5-Ar-C3 H6-H2 system in carbon fiber felt. The influences of CVI process parameters, such as gas velocity, residence time, deposition temperature, deposition pressure and the addition of H2, on the deposition rate（expressed by the mass fraction increment of the sample） of TaC were studied. The results show that CVI-TaC process is controlled by surface reaction, the maximum gas velocity is 40 cm/s and the minimum residence time is 1.2 s. The relationship between the deposition rate and the preform temperature do not accord with Arrhenius formula. The deposition rate increases firstly with the increase of temperature, reaches the maximum value at 950℃. At 1 000 ℃, the CVI process is controlled by pore diffusion. The deposition rate increases obviously with the increase of deposition pressure and the addition of H2.