摘要
TiC, ZrC and TaC modified layers were in-situ prepared on graphite matrix by chemical vapor infiltration method with metal salts as the activator. Taking the TiC modified layer as an example, through thermodynamic calculation and experiment, the thermal decomposition process of raw materials(Ti/K_(2)TiF_(6)) was analyzed, the formation mechanism of TiC was determined, and the distribution of TiC modified layer was modulated. The results show that activator K_(2)TiF_(6)has higher decomposition temperature than NH4Cl, which is conducive to improving the utilization rate of raw materials in the gas infiltration process. Increasing the content of Ti powder can increase the concentration of reaction gas and contribute to the formation of TiC modified layer. When the molar ratio of Ti to K_(2)TiF_(6)is 3:1, the surface thickness and infiltration depth of Ti C are 5.42 and 136.24 μm, respectively. Increasing the reaction temperature can improve the rate of in-situ reaction and the thickness of TiC surface layer. When the experimental temperature rises to 1600 °C, the TiC surface layer thickness increases to 20.27 μm.
以金属盐为活性剂,采用化学气相渗透法在石墨基体表面原位制备TiC、ZrC和TaC改性层。以TiC改性层为例,通过热力学计算与实验,分析原料(Ti/K_(2)TiF_(6))的热分解过程,确定TiC的形成机理,并对TiC改性层的分布进行调制。结果表明,活性剂K_(2)TiF_(6)比NH4Cl具有更高的分解温度,有利于提高气体渗入过程中原料的使用率。增加Ti粉含量能提高反应气体的浓度,有助于TiC改性层的形成。当Ti与K_(2)TiF_(6)的摩尔比为3:1时,TiC表面层厚度和渗入深度为分别为5.42和136.24μm。升高反应温度能提高原位反应速率,有助于TiC表面层厚度的增加;当实验温度升高至1600℃时,TiC表面层厚度增加至20.27μm。
基金
financially supported by the National Natural Science Foundation of China(No.11705281)。
