Flame-assisted chemical vapor deposition for continuous gas-phase synthesis of 1-nm-diameter single-wall carbon nanotubes

Flame synthesis enables the mass-production of carbon black and fullerene but not of carbon nanotubes (CNTs) due to the narrow window for producing CNTs while preventing tar generation. We report a flame-assisted chemical vapor deposition method, in which a premixed flame is used for the instantaneous generation of floating catalysts, the heating of the gas, and the growth of single-wall CNTs (SWCNTs) using a furnace at the downstream of the flame. This method yields high quality SWCNTs with a small average diameter of 0.96 nm, a small diameter deviation of 0.21 nm, and a high carbon purity of ∼90 wt%. Multiple parameters affect the SWCNT production significantly, which are investigated systematically and optimized carefully. The effects and possible mechanisms of the key parameters are discussed.