Gas-phase reaction in nanoaluminum combustion

Patrick Lynch, Giovanni Fiore, Herman Krier, Nick Glumac

Research output: Contribution to journalArticle

Abstract

The presence or absence of gas phase species during combustion of aluminum nanoparticles (n-Al) is a crucial observable in evaluating competing theories such as a diffusive oxidation mechanism and the melt dispersion mechanism. Absorption spectroscopy was used to probe the ground state of aluminum monoxide (AlO) and Al vapor in order to quantify the amount of Al and AlO present under conditions where these species were not observed in emission previously. Absorption measurements were made during combustion of nanoaluminum and micron-sized aluminum in a heterogeneous shock tube. AlO was detected in absorption at temperatures as low as 2000K in n-Al combustion, slightly below the limit seen in micro-Al combustion. Al vapor was detected during n-Al combustion at temperatures as low as 1500K, significantly lower than in micro-Al combustion, suggestive of a gas phase component. The detection limit for Al vapor was 1 × 1012cm-3. The gas phase component was much weaker than that seen in 10m Al combustion. A comparison with n-Al in an inert environment did not show Al vapor at temperatures below 2300K, even though the equilibrium concentration of Al from particles at that temperature were several orders of magnitude higher than the detection limit. This suggests a nearly pristine oxide coat that inhibits the production of Al vapor in appreciable quantities without reaction. These results are contrary to predictions of the melt dispersion mechanism, which should result in the generation of aluminum vapor from high-energy Al clusters produced from n-Al particles that spallate from mechanical stresses under rapid heating. This should further be independent of the bath gas.

Original languageEnglish (US)
Pages (from-to)842-857
Number of pages16
JournalCombustion science and technology
Volume182
Issue number7
DOIs
StatePublished - Jul 15 2010

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Keywords

  • AIO
  • Absorption spectroscopy
  • Aluminum monoxide
  • Diffusive oxidation
  • Heterogeneous shock tube
  • Melt dispersion mechanism
  • Shrinking core

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Physics and Astronomy(all)

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