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Chad J. Unrau
Washington University in Saint Louis
Advisor: Richard L. Axelbaum
Abstract
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.
Chad Unrau is from Goessel, KS, and is a Doctoral degree candidate in the Department of Energy, Environmental, and Chemical Engineering at Washington University in Saint Louis. Chad's primary field of study involves the investigation of the combustion process.
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