预制体类型及孔隙结构对化学气相渗透TaC的影响  

Influence of preforms and pore structures on chemical vapor infiltration of TaC

作　　者：陈招科[1] 熊翔[1] 李国栋[1] 

机构地区：[1]中南大学粉末冶金国家重点实验室,长沙410083

出　　处：《中国有色金属学报》2010年第9期1759-1765,共7页The Chinese Journal of Nonferrous Metals

基　　金：国家自然科学基金委员会创新研究群体科学基金资助项目(50721003);国家自然科学基金资助项目(50872154)

摘　　要：在分析和计算机准三维（2.5D）针刺整体炭毡、低密度炭毡孔隙结构的基础上,研究不同温度和压力下反应气体在上述预制体孔隙中的扩散行为、TaC的沉积速率及渗透深度。结果表明：在800～1000℃和60～400Pa时,TaCl5气体在低密度炭毡中的有效扩散系数大于其在准三维针刺毡中的有效扩散系数。在800～950℃时,TaC在准三维针刺整体炭毡中的沉积速率大于其在低密度炭毡的沉积速率,但在950～1000℃则刚好相反;在800℃和不同压力下,TaC在准三维针刺整体炭毡中的沉积速率均大于其在低密度炭毡中的沉积速率;TaC在低密度炭毡的沉积过程受表面反应控制和孔隙扩散控制的转变温度为950℃,而在准三维针刺整体毡中的转变温度则为900℃。在800℃和200Pa时,TaC在不同预制体中的渗透深度均为100%,随着沉积温度的升高以及压力的升高（400Pa）和降低（60Pa）,TaC在准三维针刺炭毡中的渗透深度显著降低,且明显小于同条件下其在低密度炭毡中的渗透深度。The effects of deposition temperature and pressure on the diffusion behavior of TaCl5 vapor in the perform pores,and the deposition rats,infiltration depths of TaC in the performs were researched on the basis of theoretical analyses of the pore structures of 2.5D needle-punctured felts,low-density carbon felts.The results show that at 800-1 000 ℃ and 60-400 Pa,the effective diffusion coefficient of TaCl5 vapor in low-density felt is larger than that in 2.5D needle-punctured felt;at 800-950 ℃,the deposition rate of TaC in 2.5D needle-punctured perform is larger than that in the low-density perform,but it is opposite at 950-1 000 ℃.At 800 ℃ and 60-400 Pa,the deposition rate of TaC in 2.5D needle-punctured felt is larger than that in low-density felt.The change temperatures controlled by surface reactive kinetics and diffusion kinetics of pore in TaC-CVI process are 950 ℃ in low-density felts and 900 ℃ in 2.5D needle-punctured felts,respectively;at 800 ℃ and 200 Pa,the infiltration depths of TaC in 2.5D needle-punctured felts and low-density felts are all 100%,but decrease obviously with increasing temperature and variation of pressure.In addition,the infiltration depth of TaC in 2.5D needle-punctured felts is less than that in low-density felts.

关 键 词：TAC 化学气相渗透 孔隙结构 扩散 渗透深度 

分 类 号：TB332[一般工业技术—材料科学与工程]