Characterization of diffusion flames for synthesis of single-walled carbon nanotubes
- Department of Energy, Environmental, Chemical Engineering/Center for Materials Innovation, Washington University, St. Louis, MO (United States)
- Innovative Scientific Solutions, Inc., Dayton, OH (United States)
Recent studies have shown that Fe/Si/O catalysts on the fuel side of an oxygen-enriched inverse diffusion flame produce micron-length single-walled carbon nanotubes at rapid rates (>100{mu}m/s). Despite the favorable catalyst/flame interaction for nanotube nucleation and growth, the catalyst lifetimes are only a few milliseconds. To increase catalyst lifetime and hence, carbon nanotube length, it is necessary to know how the local environment changes as the catalyst moves through the flame. A 2-D computational fluid dynamics model with detailed chemistry is employed to investigate the nature of the flame environment along various catalyst trajectories. The results indicate that temperature and species concentrations do not change significantly along individual catalyst trajectories, although not all trajectories experience the same environment due to the steep gradients in the radial direction. On the other hand, analysis of catalyst particle composition before and after nanotube growth shows that catalyst oxygen content decreases significantly during nanotube growth. This change in catalyst composition could affect the relative rates of carbon supply versus removal from the catalyst surface, such that carbon encapsulation and thus poisoning of the catalyst is favored after sufficient time. The results of this work indicate that catalyst deactivation, not a changing catalyst environment, is responsible for rapid encapsulation of the catalyst by amorphous carbon and thus, the short catalyst lifetimes observed in oxygen-enriched diffusion flames. (author)
- OSTI ID:
- 21337862
- Journal Information:
- Combustion and Flame, Vol. 157, Issue 9; Other Information: Elsevier Ltd. All rights reserved; ISSN 0010-2180
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBON
NANOTUBES
OXYGEN
CATALYSTS
FLAMES
COMBUSTION
DIFFUSION
IRON
LENGTH
LIFETIME
SILICON
COMPUTERIZED SIMULATION
FLUID MECHANICS
ENCAPSULATION
SYNTHESIS
CHEMICAL COMPOSITION
DEACTIVATION
NUCLEATION
PARTICLES
REMOVAL
SURFACES
TWO-DIMENSIONAL CALCULATIONS
Single-walled carbon nanotubes