纳米碳颗粒／碳化硅陶瓷基复合材料的氧化行为

Oxidation Behavior of Carbon Nanoparticles/Silicon Carbide Composite Ceramics

以微米硅（Si）和纳米碳黑（Cp）粉体为主要原料，采用经机械化学法合成的碳化硅（SiC）和15％和25％的纳米碳颗粒与碳化硅（Cp-SiC）的复合粉体，并经无压烧结得到了Cp/SiC陶瓷基复合材料，分析了在不同温度条件下Cp／SiC烧结体的氧化行为。结果表明：当温度小于700℃时，Cp/SiC复合陶瓷在空气中的氧化受C—O2反应控制，致使其为均匀氧化；700℃时，氧化后的复合材料显气孔率最大，弯曲强度达极小值；大于700℃，氧化过程受02的气相扩散控制，呈非均匀氧化；700-900℃之间，02通过微裂纹的扩散控制着Cp／SiC的氧化过程；900～1100℃之间，02通过SiC缺陷的扩散控制着Cp/SiC的氧化过程，并在1000℃时的最初的2h内，复合材料弯曲强度增大，且达NT极大值。同时表明，纳米碳含量是影响复合材料强度及氧化行为的关键因素，添加纳米碳质量分数为15％的Cp／SiC复合陶瓷可以作为一种抗氧化性能优良的玻璃夹具材料。

The oxidation behavior of three pressureless-sintered silicon carbide （SIC）, 15%Cp/SiC and 25%Cp/SiC composites, which were prepared with carbon nanoparticles （Cp） and silicon micron-sized particles by a mechanochemical method, at various tempera- tures was investigated. The results show that the oxidation of Cp/SiC ceramics in air is controlled via C＋O2 reaction at 〈 700 ℃, the bending strength of samples decreases to a minimum value at 700 ℃; the oxidation is controlled by 02 diffusion through mi- cro-cracks unequally in the range of 700-900 ℃; the oxidation of Cp/SiC is controlled by 02 diffusion through the structural defects of matrix in the range of 900-1 100 ℃. The bending strength of composites reaches to a maximum value during initial 2 h at 1 000 ℃ due to the formation of SiO2 layer and the healing defects of matrix. It is also indicated that the addition of Cp in the composite has an effect on the bending strength and the oxidation behavior of the composite. The ceramic composite with the Cp addition of 15% （in mass） can be used as a promising anti-oxidation glass-holder material.