Gas-phase synthesis of single-walled carbon nanotubes on catalysts producing high yield

Composite catalysts are employed for high yield gas-phase synthesis of single-walled carbon nanotubes (SWCNTs) Specifically, silicon is investigated as an additive to iron catalysts for synthesis of SWCNTs in inverse diffusion flames While silicon is often used as a substrate in supported-catalyst processes to promote nanotube growth, this study demonstrates that it can also be beneficial for gas-phase nanotube synthesis in diffusion flames An oxy-fuel ethylene inverse diffusion flame is employed to provide a soot-free, carbon-rich environment for nanotube growth iron and silicon precursors are added to the fuel stream for nucleation of iron/silicon/oxygen catalyst particles, with the amount of particle oxidation determined by the amount of oxygen-enrichment and fuel dilution at a given temperature Under optimum conditions, nearly 90% of the catalyst particles produce single-walled carbon nanotubes as compared to less than 10% when the catalyst consists of only iron and oxygen The effect of silicon addition is investigated through variation of the iron/silicon ratio and measurement of nanotube growth rates Silicon is shown to primarily affect SWCNT inception with minimal influence on growth rate (C) 2009 Elsevier Ltd All rights reserved