Feedstock diffusion and decomposition in the root growth of aligned carbon nanotube (CNT) arrays is discussed. A non-dimensional modulus is proposed to differentiate catalyst-poisoning controlled growth deceleration from one which is diffusion controlled. It is found that, at current stage, aligned multi-walled carbon nanotube (MWNT) arrays are usually free of feedstock diffusion resistance. However, for single-walled carbon nanotube (SWNT) arrays, since the inter-tube distance is much smaller than the mean free path of carbon source (ethanol here), high diffusion resistance is significantly limiting the growth rate. The method presented here is also able to predict the critical lengths in different chemical vapor deposition (CVD) processes from which CNT arrays begin to meet this diffusion limit, as well as the possible solutions to this diffusion caused growth deceleration. The diffusion of carbon source inside of an array becomes more important when we found ethanol undergoes severe thermal decomposition at the reaction temperature. This means, in a typical alochol CVD, hydrocarbons and radicals decomposed from ethanol may collide and react with the outer walls of SWNTs before reaching catalyst particles. We found when flow rate is low and ethanol is thoroughly decomposed, the produced SWNTs contain more soot structures than the SWNTs obtained at higher ethanol flow rate. Understanding the mass transport and reaction inside a SWNT array is helpful to synthesize longer and cleaner SWNTs.
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ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer
December 18–21, 2009
Shanghai, China
Conference Sponsors:
- Nanotechnology Institute
ISBN:
978-0-7918-4390-1
PROCEEDINGS PAPER
Feedstock Diffusion and Decomposition in Aligned Carbon Nanotube Arrays
Rong Xiang,
Rong Xiang
The University of Tokyo, Tokyo, Japan
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Erik Einarsson,
Erik Einarsson
The University of Tokyo, Tokyo, Japan
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Junichiro Shiomi,
Junichiro Shiomi
The University of Tokyo, Tokyo, Japan
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Shigeo Maruyama
Shigeo Maruyama
The University of Tokyo, Tokyo, Japan
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Rong Xiang
The University of Tokyo, Tokyo, Japan
Erik Einarsson
The University of Tokyo, Tokyo, Japan
Junichiro Shiomi
The University of Tokyo, Tokyo, Japan
Shigeo Maruyama
The University of Tokyo, Tokyo, Japan
Paper No:
MNHMT2009-18479, pp. 231-234; 4 pages
Published Online:
October 26, 2010
Citation
Xiang, R, Einarsson, E, Shiomi, J, & Maruyama, S. "Feedstock Diffusion and Decomposition in Aligned Carbon Nanotube Arrays." Proceedings of the ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer. ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer, Volume 2. Shanghai, China. December 18–21, 2009. pp. 231-234. ASME. https://doi.org/10.1115/MNHMT2009-18479
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