Amorphous carbon assisted highly percentage synthesis of ultralong, well-aligned, and visible carbon nanotubes

In this study, we present a method to observe the location and the length of carbon nanotubes under an optical system instead of SEM. Firstly, the carbon nanotubes were synthesized by using mixed methane and ethylene carbon source in the chemical vapor deposition (CVD) as reported in W. Kim et al. (2002). Then, the carbon nanotubes were coated with amorphous carbon by blowing ethanol vapor into the furnace at 900 °C. The observations of SEM and TEM show that each carbon fiber consists of one carbon nanotube and a great deal of amorphous carbon. The diameters of the carbon fibers, around 500 nm, are so large that they can be easily observed and estimated from the optical images. For example, the longest length of carbon fiber observed in this experiment can exceed 2 cm. In addition, the most of the carbon fibers are well-aligned due to floating catalyst as presented in S. Huang et al. (2003). This method is useful as locating of suspended carbon nanotubes or manipulating nanotubes under the optical system.