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对SiO2-C-N2系统中的主要化学反应和SiC晶须在该系统中的合成条件进行了热力学分析,采用SiO2微粉为硅源,石墨、活性炭和碳黑为碳源,氧化硼为催化剂,分别在1500℃、1550℃和1600℃利用碳热还原法合成碳化硅晶须,通过X射线衍射、扫描电子显微镜和电子探针分析合成晶须的特征。结果表明:在氮气气氛下利用碳热还原反应合成SiC晶须的温度在1450℃以上,且随着温度的升高,SiC晶须的生成量增多,晶须直径变大;以炭黑和活性炭等较高活性的碳源代替石墨可以使反应速度加快,但合成的SiC晶须较粗甚至生成SiC颗粒;杂质含量较多会使得SiC晶须生成数量降低,同时晶须出现弯曲现象.
The main chemical reactions of SiO2-C-N2 system and the synthesis conditions of SiC whiskers in the system were analyzed. The SiO2 powder was used as silicon source, graphite, activated carbon and carbon black as carbon source and boron oxide as catalyst. The silicon carbide whiskers were synthesized by carbothermal reduction at 1500 ℃, 1550 ℃ and 1600 ℃, respectively. The characteristics of the synthesized whiskers were analyzed by X-ray diffraction, scanning electron microscopy and electron probe. The results show that the temperature of SiC whiskers synthesized by carbothermal reduction reaction is above 1450 ℃ in nitrogen atmosphere, and the formation of SiC whiskers increases with the increase of temperature, and the diameter of whiskers increases. The carbon black and activated carbon Replacing graphite with higher activity such as carbon could speed up the reaction, but the synthesized SiC whiskers were coarse and even formed SiC particles. The more the content of impurities would make the number of SiC whiskers decrease and the whisker appeared bending phenomenon.