Synthesis of carbon nanotubes on carbon fibers by modified chemical vapor deposition
2013
Hu, Zhi-hui | Dong, Shao-ming | Hu, Jian-bao | Wang, Zhen | Lu, Bo | Yang, Jin-shan | Li, Qing-gang | Wu, Bin | Gao, Le | Zhang, Xiang-yu
Carbon nanotubes (CNTs) were synthesized on carbon fibers by a modified thermal chemical vapor deposition (CVD) method. The fibers were first treated at a temperature of 973K and then treated by a mixture of sulfur acid and nitric acid with a volume ratio of 1:3 to improve the dispersion of catalyst precursor (Fe (NO₃)₃·9H₂O) on the surface before impregnation with a catalyst solution. The carbon fibers then underwent simultaneous catalyst reduction and CNT growth to decrease the contact time between the transition metal and the carbon fiber surface, and a uniform and thick CNT forest could be obtained with no significant decrease of the mechanical strength of the carbon fibers compared with those produced by traditional thermal CVD. An in-depth analysis shows that the process parameters have a great influence on the CNT growth rate, such as the type of solvent, concentration of Fe (NO₃)₃·9H₂O, the ratio of H₂ to C₂H₂, and the growth time. It was revealed that a better CNT forest could be obtained when the catalyst solvent is ethanol, the Fe concentration is 100mM, the ratio of H₂/C₂H₂ is 4/1, the temperature is 1023K and the growth time is 30min.
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