熔硅浸渗工艺快速制备C/SiC复合材料的非等温氧化行为

Non-isothermal oxidation behavior of C/SiC composites rapidly prepared by molten silicon infiltration technique

以针刺整体毡为预制体,采用化学气相沉积(CVD)增密制备C/C多孔体,用熔硅浸渗(MSI)工艺快速制备C/SiC复合材料,通过非等温热重分析研究材料低温下的氧化反应动力学和反应机理。结果表明:C/SiC材料的非等温氧化过程呈现自催化特征,氧化机理为随机成核,氧化动力学参数为l:g(A/min-1)=8.752,Ea=169.167 kJ/mol。MSI工艺中,纤维因硅化损伤产生的活性碳原子易先发生氧化,使C/SiC材料起始氧化温度仅为524℃,比C/C材料约低100℃,且氧化产生大量的裂纹和界面,使材料在氧化初期即具有大的氧化反应速率,C/C材料则出现氧化反应速率滞后现象。

C/SiC composites were rapidly prepared by the integrity felt which was densified by chemical vapor deposition （CVD） and subsequent molten silicon infiltration （MSI） technique. Non-isothermal TG analysis was used to study the oxidation kinetics and mechanism of the composites at lower temperatures. The results show that the non-isothermal oxidation process of C/SiC composites exhibits self-catalytic characteristics. The oxidation mechanism is random nucleation, and the kinetic parameters are lg A=9.703 min^-1 and Ea=182.009 kJ/mol. Active carbon atoms are produced by siliconization of fibers during MSI process and they encounter oxidation first. The initial oxidation temperature of C/SiC composites is 524 ℃ and about 100 ℃ lower than that of C/C composites. In addition, cracks and interfaces are produced by oxidation, which causes large oxidation rate at the initial oxidation stage, while oxidation rate is relatively postponed for C/C composites.