Multi-wall carbon nanotubes were synthesized by dc carbon arc discharge method in various ambient gasessuch as He, H2, N2, O2, C2H2, and C02, and at different pressures (3-100 kPa). The appearance of the nanotubesand nanoparticles on the cathode surface varied with respect to these experimental parameters. The remarkableconditions, in which considerable amount of nanotubes prepared with the fewest nanoparticles, were obtained inboth H2 and O2 ambient at 25 kPa and 100 A.
