Microstructure and microscopic deposition mechanism of twist-shaped carbon nanocoils based on the observation of helical nanoparticles on the growth tips

Carbon nanocoils possessing a twisting form were prepared from an Fe-based alloy (SUS410) catalyst, the crystallographic properties of the catalyst surface, which was present on the growth tip, were examined, and a novel growth mechanism of the nanocoils is presented. Single-helix twisted carbon nanocoils with a coil diameter of 300-400 nm were obtained at 700-800 degrees C with a yield of 60% and a purity of nearly 100%. The catalyst structure observed on the growth tip was a Fe5C2 (monoclinic) or Fe7C3 (orthorhombic) single crystal, in which some of the Fe atoms were substituted by Cr. Carbon nanoparticles with a helical structure were observed on the surface of catalyst particle. It is considered that the carbon nanoparticles are a helical carbon supply source. That is, the catalyst particle supplies microscopic carbon nanoparticles by helical deposition patterns on the catalyst surface to form macroscopic helical patterns of carbon nanocoils. (c) 2004 Elsevier Ltd. All rights reserved.