先驱体转化法制备SiCO陶瓷粉体的氧化性能

以先驱体转化法制备的SiCO陶瓷粉体为原材料，采用热重法研究了粉体在干燥空气中的氧化性能。采用液态聚碳硅烷裂解制备的SiCO 陶瓷粉体平均粒径为7μm，氧化处理温度分别为：900℃、950℃、1000℃、1050℃，氧化时间均为4 h。结果表明：液态聚碳硅烷裂解制备的SiC_{1. 12}O_{0. 12}陶瓷粉体在1173～1373 K、干燥空气中，氧化增重表现为典型的2阶段变化规律：900℃ 下的前80 min至1050℃下的前20 min时间内，材料氧化表现为快速增重趋势；随后较长的氧化时间里，材料内部气孔的氧化由于封孔而停止，氧化反应主要由扩散控制，样品增重不太明显。经计算SiCO陶瓷粉体的氧化活化能为121 kJ/mol，并在此基础上推导了热重法与厚度测量法获得的2种氧化速率常数的转变公式。

Oxidation behavior of polymer derived SiCO ceramic powders

SiC1. 12O0. 12 ceramic powders were obtained by pyrolyzing the high-branched polycarbosilane (HBPCS). The oxidation behavior of the powders in the dried air was investigated by the thermal gravimetric method. The mean particle size of the HBPCS derived SiCO ceramic powders was about 7μm. The samples were oxidized at temperatures of 900℃，950℃，1000℃ and 1050℃ for 4 h. The results show that the mass change during the oxidation process exhibits two distinguished stages. At the first stage (from 80 min at 900℃ to 20 min at 1050℃)，the mass is rapidly increased with the oxidation time. However，the mass of the powders changes little at the second stage due to the pore sealing. The molecular oxygen diffusion is the controlling process for oxidation at this stage. The activation energy of this material oxidized at 1173～1373 K is about 121 kJ/mol. The relationship between parabolic rate constants obtained by the thermal gravimetric method and oxide thickness change is deduced.