Synthesis of high quality single-walled carbon nanotubes with purity enhancement and diameter control by liquid precursor Ar–H2 plasma spraying

Abstract

• A new plasma process is proposed for the synthesis of SWCNTs at a large-scale. • High-quality SWCNTs were produced due to the high temperature of the plasma. • Hydrogen plasma contributes to the purity enhancement by selective etching of amorphous carbon. • The in situ diameter control is demonstrated by adjusting the sulfur content in the feedstock. As usage of carbon nanotubes continues to increase in both scientific research and practical applications, there has been a growing interest in the large-scale synthesis of those materials with high quality and high purity. Here we report a new plasma process developed for the large-scale synthesis of high quality single-walled carbon nanotubes (SWCNTs). An induction thermal plasma with a liquid precursor spraying technique was employed for an effective synthesis of SWCNTs from a mixture of toluene and ferrocene. It has been successfully demonstrated in this new process that high quality SWCNTs can be synthesized continuously with a reasonably high-purity, the structural quality of the materials produced being comparable to those of SWCNTs produced from the laser vaporization process. The high temperature of the plasma, over 4000 K, seems to be responsible for the production of high quality SWCNTs and the rapid treatment of a large amount of feedstock, whereas the hydrogen plasma contributes to the purity enhancement by selective etching of amorphous carbon. It is also found that the diameter distribution of SWCNTs can be controlled effectively by varying the sulfur content in the feedstock mixture, which is very promising for many advanced applications of SWCNTs such as SWCNT-based electronics.