Free-standing and aligned carbon nanotubes and synthesis thereof

Abstract

One or more highly-oriented, multi-walled carbon nanotubes are grown on an outer surface of a substrate initially disposed with a catalyst film or catalyst nano-dot by plasma enhanced hot filament chemical vapor deposition of a carbon source gas and a catalyst gas at temperatures between 300° C. and 3000° C. The carbon nanotubes range from 4 to 500 nm in diameter and 0.1 to 50 μm in length depending on growth conditions. Carbon nanotube density can exceed 10nanotubes/mm. Acetylene is used as the carbon source gas, and ammonia is used as the catalyst gas. Plasma intensity, carbon source gas to catalyst gas ratio and their flow rates, catalyst film thickness, and temperature of chemical vapor deposition affect the lengths, diameters, density, and uniformity of the carbon nanotubes. The carbon nanotubes of the present invention are useful in electrochemical applications as well as in electron emission, structural composite, material storage, and microelectrode applications.