孔结构对热解酚醛树脂制备碳纳米管的影响

Effect of Pore Structure on Preparation of Carbon Nanotubes via Pyrolysis of Phenolic Resin

以不同的酚醛树脂为原料经催化热解法制备碳纳米管时结果差异较大,为阐明存在的问题及原因,以酚醛树脂为碳源、硝酸铁为催化剂前驱体,通过催化酚醛树脂裂解的方法制备碳纳米管,研究了酚醛树脂中孔结构对合成碳纳米管的影响。采用X射线衍射、扫描电子显微镜和透射电子显微镜对酚醛树脂热解产物的物相组成及显微结构进行了分析。结果表明:1)碳纳米管仅生长在固化后酚醛树脂的大气孔(50~1 000μm)中,其直径约为40~100纳米,长度可达几百微米,其它位置基本无碳纳米管的生成;2)较大的气孔(50~1 000μm)可为碳纳米管的生长提供相对充足的碳源和生长空间,继而有利于碳纳米管的生成;3)较小的气孔(30μm以下)由于难以满足该条件而基本无碳纳米管的生成。碳纳米管的产率与酚醛树脂固化后形成气孔的大小有关,采用固化后能形成较大孔径的酚醛树脂为碳源可以提高碳纳米管的产率。

To clarify the yield change of carbon nanotubes （CNTs） prepared by a phenolic resin catalytic pyrolysis method, CNTs were synthesized via catalytic pyrolysis with two different kinds of phenolic resins and ferric nitrate as a catalyst precursor in Ar atomosphere at 1 000℃ for 3 h. The effect of pore structure on the formation of CNTs was investigated. The phase and microstructure of the final products were characterized by X-ray diffraction, field emission-scanning electron microscopy and transmission electron microscopy. The results indicate that CNTs with 40-100 nm in diameter and several hundred micronmeters in length are only prepared in the pores with the size of 50-1 000μm formed during the curing process rather than other sites. Compared to the small pores without CNTs formation, large pores can offer sufficient carbon source and space for CNTs growth due to the appearance of CNTs only in large pores of pyrolyzed phenolic resin. The yield of CNTs depends on the pore size in the cured phenolic resin. The yield of CNTs can be improved when phenolic resin with large pores is used in the cured precursor as a carbon source.