多壁碳纳米管表面涂层的形成及其抗氧化性

Surface Coating Formation on the Multi-walled Carbon Nanotubes and Its Oxidation Resistance

摘要:

研究以单质硅粉(Si)、金属铝粉和硅粉的混合物(Al+Si)作为2种不同硅源时，在埋碳床中经1000～1500 ℃处理后多壁碳纳米管(multi-walled carbon nanotubes, MWCNTs)表面涂层的形成及其抗氧化性能的变化。采用X射线衍射仪、高分辨透射电镜及能谱仪和热重-差示扫描量热仪对处理前后的样品进行表征。结果表明：以Si为硅源时，MWCNTs经小于1400 ℃处理后表面生成了SiC涂层，1500 ℃处理后大部分MWCNTs蚀变成实心的SiC纳米线；与Si相比，以Al+Si为硅源时相同温度处理后MWCNTs表面涂层的厚度增加，且1500 ℃处理后MWCNTs并未发生结构蚀变。与原MWCNTs相比，处理后的MWCNTs抗氧化性能提高，且随着涂层厚度的增加而不断提高。非等温动力学进一步表明，原MWCNTs的氧化活化能为157.69 kJ/mol，以Si为硅源时1400 ℃处理后为202.39 kJ/mol，而Al+Si为硅源时达到230.70 kJ/mol

Abstract:

Coating formation on multi-walled carbon nanotubes (MWCNTs) treated in a coke bed in the temperature range of 1000~1500 °C using silicon powder (Si) and the mixture of aluminum and silicon powders (Al+Si) as the silicon sources and its oxidation resistance were investigated by means of X-ray diffraction, high resolution transmission electron microscopy equipped with energy dispersive X-ray spectroscopy and thermogravimetric analysis-differential scanning calorimetry. Results show that using Si as a silicon source, SiC coating forms on the surface of MWCNTs after treated below 1400 °C. At 1500 °C, most of MWCNTs have transformed into solid SiC nanowires. Using Al+Si as a silicon source, the thickness of the coating increases at the same treated temperature compared with Si source. In addition, transformation of MWCNTs is prevented after treated at 1500 °C. The oxidation resistance of the treated MWCNTs improves compared with the as-received ones, and it gets better with increasing the thickness of the coating. Non-isothermal kinetics shows that oxidation activation energy of the as-received MWCNTs is 157.69 kJ/mol, while they are 202.39 kJ/mol and 230.70 kJ/mol after MWCNTs treated at 1400 °C using Si and Al+Si as the silicon sources, respectively