High-quality single-walled carbon nanotubes
(SWNTs) have been produced by DC arc discharge in hydrogen ambience. By using Fe 1% catalyst a large amount of SWNTs are produced in pure
gas. Other transition metals of iron group and its combination are also used as catalyst for preparing SWNTs by adding 1%
Tri-metal catalyst, Fe(0.25%)-Ni(0.9%)-Co(0.9%), is found to be most effective for high yield of SWNTs. The SWNTs diameters are fairly thick ∼1.4–4 nm, and some double-walled carbon nanotubes also exist with them.