Journal of Nanoparticle Research

, Volume 12, Issue 6, pp 2125–2133 | Cite as

Single-walled carbon nanotube formation on iron oxide catalysts in diffusion flames

  • Chad J. Unrau
  • Richard L. AxelbaumEmail author
  • Phil Fraundorf
Research Paper


Single-walled carbon nanotubes (SWCNTs) are shown to grow rapidly on iron oxide catalysts on the fuel side of an inverse ethylene diffusion flame. The pathway of carbon in the flame is controlled by the flame structure, leading to formation of SWCNTs free of polycyclic aromatic hydrocarbons (PAH) or soot. By using a combination of oxygen-enrichment and fuel dilution, fuel oxidation is favored over pyrolysis, PAH growth, and subsequent soot formation. The inverse configuration of the flame prevents burnout of the SWCNTs while providing a long carbon-rich region for nanotube formation. Furthermore, flame structure is used to control oxidation of the catalyst particles. Iron sub-oxide catalysts are highly active toward SWCNT formation while Fe and Fe2O3 catalysts are less active. This can be understood by considering the effects of particle oxidation on the dissociative adsorption of gas-phase hydrocarbons. The optimum catalyst particle composition and flame conditions were determined in near real-time using a scanning mobility particle sizer (SMPS) to measure the catalyst and SWCNT size distributions. In addition, SMPS results were combined with flame velocity measurement to measure SWCNT growth rates. SWCNTs were found to grow at rates of over 100 μm/s.


Single-wall carbon nanotubes Diffusion flames Differential mobility analyzer Iron oxide catalyst Oxy-fuel combustion 



The authors thank Xiaofeng Zhang for his efforts in collecting TEM data and Dr. John Gleaves for his helpful discussions. This research was funded by the Center for Materials Innovation at Washington University and NASA.


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Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  • Chad J. Unrau
    • 1
    • 2
  • Richard L. Axelbaum
    • 1
    Email author
  • Phil Fraundorf
    • 3
  1. 1.Department of Energy, Environmental and Chemical Engineering/Center for Materials InnovationWashington University in St. LouisSt. LouisUSA
  2. 2.Cabot CorporationPampaUSA
  3. 3.Department of Physics & Astronomy/Center for Molecular ElectronicsUniversity of Missouri-St. LouisSt. LouisUSA

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