Nanotubes from methane flames

Entangled multi-walled carbon nanotubes with a diameter range of 20–60 nm were found to grow on a Ni–Cr wire in laminar co-flow methane-air diffusion flames. Nickel oxide particles were inside some of the nanotubes, suggesting that their particles, formed on the wire at the early stage of the synthesis, acted as catalyst. The carbon nanotubes can grow by a root-growth mechanism in a limited region inside the flame where oxygen plays an important role in the formation of nanotubes.