石墨化处理对碳纳米管结构的影响

Effect of Graphitizing Treatment on Structure of Carbon Nanotubes

以苯为碳源、二茂铁为催化剂在竖式炉中用流动法制备出外径为40～80nm,内径20～40nm,长度50～500μm的碳纳米管;并在1800,2500,2800,2900℃温度下分别对其进行高温石墨化处理.X射线衍射(XRD)分析结果显示,随着温度的增加,碳纳米管的微晶层间距减小,片层结构趋向规整,同时石墨微晶沿a轴和c轴长大,有效改善了碳纳米管的微观结构.碳纳米管里层的乱层结构石墨化所需能量由热能提供,整个过程包括非碳原子的排除、多核芳环平面组织结构化、微晶重排、微晶合并与长大;外层的无定型碳主要靠铁的催化作用实现石墨化.

The carbon nanotubes were synthesized from catalytic decomposition of benzene using floating transition method with ferrocene as catalyst. The carbon nanotubes are straight with diameter 40-80 nm, internal diameter 20-40 nm and length 50-500 μm. The XRD patterns of carbon nanotubes which were graphitizing-treated at 1800°C, 2500°C, 2800°C, 2900°C show that interlamellar spacing of microcrystallites of carbon nanotubes decreases with the increasing of temperature. At the same time, graphite microcrystallines grow up along crystal axes. It was demonstrated the structure of carbon nanotubes become regular and orderly with graphitizing treatment. Graphitizing mechanism of carbon nanotubes was discussed. Except for the rearrangement of microcrystallites, the particles of iron in nanotubes as catalyst also promote the graphitization of amorphous carbon of outer layer of carbon nanotubes.