Synthesis of carbon nanotubes on carbon fibers by modified chemical vapor deposition

Abstract

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 973 K 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 100 mM, the ratio of H2/C2H2 is 4/1, the temperature is 1023 K and the growth time is 30 min. [New Carbon Materials 2012;27(5):352–61]