Synthesis of single-walled carbon nanotubes in oxy-fuel inverse diffusion flames with online diagnostics

C. J. Unrau, R. L. Axelbaum, P. Biswas, P. Fraundorf

Research output: Contribution to journalConference articlepeer-review

33 Scopus citations


A novel technique for synthesis of single-walled carbon nanotubes (SWNTs) in diffusion flames is presented, as is a diagnostic tool that can provide online information about nanotube size, number density, and purity. An inverse diffusion flame with a high stoichiometric mixture fraction (Zst) is used to produce SWNTs with an average length of 1 μm. The high Zst flame allows nanotubes to be produced in a fuel-rich region that is void of soot and polycyclic aromatic hydrocarbons (PAH). In addition, by operating as an inverse diffusion flame the carbon nanotubes (CNTs) are not exposed to oxygen and thus, can be collected downstream. Consequently, this flame provides a potential approach to large-scale synthesis of pure SWNTs. In addition, a differential mobility analyzer (DMA) is employed as an online diagnostic tool. The DMA can distinguish between excess catalyst particles and CNTs due to the differences in their electrical mobilities. Thus, the presence of CNTs as well as their size, number density, and purity relative to excess catalyst particles can be identified from the size distribution of the aerosol sampled downstream of the flame. This tool allows for rapid identification of the effect of changing process variables on nanotube growth and thus, the production process can be quickly optimized.

Original languageEnglish (US)
Pages (from-to)1865-1872
Number of pages8
JournalProceedings of the Combustion Institute
Volume31 II
Issue number2
StatePublished - 2007
Externally publishedYes
Event31st International Symposium on Combustion - Heidelberg, Germany
Duration: Aug 5 2006Aug 11 2006


  • Differential mobility analyzer
  • Online diagnostics
  • Oxygen-enrichment
  • Single-walled carbon nanotubes
  • Stoichiometric mixture fraction

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Mechanical Engineering
  • Physical and Theoretical Chemistry


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