Low pressure synthesis of single-walled carbon nanotubes by arc discharge

High yield of single-walled carbon nanotubes (SWCNTs) has been synthesized by do arc discharge under low pressure of helium gas with a small amount of a mixture of nickel and iron powders. The highest yield of carbon nanotubes (CNTs) was obtained at low pressure of 100 Torr with 5 wt.% of metal mixture, in good contrast with the previous works. In addition, we introduced sulfur promoter to improve the yield, which gave rise to again the highest yield at low gas pressure. This was attributed to the higher arching temperature at lower gas pressure, facilitating an efficient formation of CNTs. (C) 2002 Elsevier Science B.V. All rights reserved.