Synthesis of Highly Crystalline Multiwalled Carbon Nanotubes by Thermal Chemical Vapor Deposition Using Buffer Gases

Multiwalled carbon nanotubes were formed on Fe–Ni–Co alloy-coated glass substrates by infrared-radiation-heated thermal chemical vapor deposition using CO and H₂ gases at temperatures as low as 480–580°C. Growth of the carbon nanotubes was strongly affected by Ar or N₂ gas introduced during the heat-up stage prior to the growth, which markedly increased the growth rate of carbon nanotubes by an order of magnitude and yielded the carbon nanotubes with better crystallinity and less amount of carbonaceous impurity particles, in comparison with those grown at the same condition but heated in vacuum to the growth temperature. It is proposed that gas-phase energy transfer enhances the synthesis of highly crystalline carbon nanotubes while suppressing the formation of carbonaceous impurity particles.