Microstructural evolution of multi-walled carbon nanotubes in the presence of mixture of silicon and silica powders at high temperatures
- 作者：Yawei Li ; Ming Luo ; luoming19850302@126.com ; Shengli Jin ; Shaobai Sang ; Lei Zhao
- 关键词：SiC ; MWCNTs ; Evolution ; SiO2 coating ; Oxidation resistance
- 刊名：Ceramics International
- 出版年：2012
- 期刊代码：13_02728842
- 类别：ms
- 出版时间：July, 2012
- 卷：38
- 期：5
- 页码：4105-4110
- 文件大小：1423 K
摘要
Microstructural evolution of multi-walled carbon nanotubes (MWCNTs) in the presence of mixture of silicon and silica powders in a coke bed is studied in the temperature range of 1000-1500 掳C by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and thermogravimetry-differential scanning calorimetry (TG-DSC). The results showed that a thin amorphous SiO2 coating was formed on the surface of MWCNTs at the temperature below 1300 掳C. With the increase of the treated temperature, the coating became thicker, 3-7 nm in thickness at 1400 掳C and a maximum of 10 nm at 1500 掳C. Meanwhile, SiC nanowires and SiC nanocrystals around Ni catalyst at the tip of MWCNTs were formed at 1400 掳C and 1500 掳C, which were related to the vapor-vapor (V-V) and vapor-liquid-solid (V-L-S) reactions between SiO (g) and CO (g) or C (s), respectively. The oxidation resistance of all the treated MWCNTs was better than that of as-received ones. The oxidation peak temperature reached 804.2 掳C for the treated MWCNTs, much higher than 652.2 掳C for as-received ones.