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Transcript
Decomposition of tetramethylsilane in laminar premixed low-pressure flames
Y. Karakaya(*), A. Ditmann, T. Kasper
Thermodynamics, University of Duisburg-Essen, Germany
Institute for Combustion and Gas Dynamics and Center for Nanointegration (CENIDE), University of
Duisburg-Essen, Germany
*
Corresponding author; email address: [email protected]
Synthesis in flame reactors is a reliable method to produce functional materials in a nanoscale size. Despite the intensive use of silicon based molecular precursors in the industry for
nano material production, there is little knowledge about the particle formation process [1].
Silicon based nanoparticles are of great interest for a wide field of applications, e.g. in energy
storage in batteries or lighting materials for photoluminescence. The properties of flamesynthesized nanoparticles strongly depend on the particle size, which is influenced by the
temperature of the synthesis and precursor concentration. The generation of nanoparticles in
flame reactors incorporates precursor decay and particle formation into the complex reaction
network of a flame. The network of chemical reactions of the precursor decomposition and
small species involved in particle growth interacts with the flame chemistry. The interaction
with flame radicals influences the precursor decay and the formation of the particle
precursors. Consequently, experimental studies on the decomposition of the silicon based
precursor to intermediate species and stable products and the inception of particles during
flame synthesis is of great interest to generate a fundamental understanding of the synthesis
process.
By means of Time-of-flight mass spectrometric in-situ measurements species can be
identified which occur in the gas phase synthesis of tetramethylsilane doped laminar lowpressure flames in large concentrations. This information is the first step in generating a
model of the chemical processes in flame synthesis. In a laminar flame the reaction sequence
can be described and modelled one-dimensionally, where changes of temperature and
concentrations occur only with the height above the burner. Using a quartz nozzle, a sample
from the flame at different heights above the burner is transferred to a mass spectrometer and
analysed. The reactions are quenched from 30 mbar in the burner chamber to 1x10-4 mbar in
the first stage and 1x10-7 mbar in the second stage. Due to the high sensitivity of the
experimental setup isotope patterns of the species can be determined and enable an accurate
identification of predominant decomposition species in a small to intermediate size range.
Preliminary results show that tetrametyhlsilane decomposes into a series of intermediates
(SiO, Si, etc.). These intermediates appear early in the decomposition process and react
subsequently to form silicon dioxide particles.
The experimental observations identify silicon mono oxide as a key intermediate in the gasphase synthesis of silica. Data sets including concentration profiles of neutral species and key
particle precursors in the gas-phase have been obtained in tetramethylsilane doped hydrogen
flames which can be used to validate kinetic reaction models for precursor decomposition and
small particle formation.
[1] N. G. Glumac, Formation and consumption of SiO in powder synthesis flames, Combustion and flame, 2001
[2] O.M. Feroughi, L. Deng, S. Kluge, T. Dreier, H. Wiggers, I. Wlokas, C. Schulz, Experimental and numerical
study of a HMDSO-seeded premixed laminar low-pressure flame for SiO2 nanoparticle synthesis, Proceedings
of the Combustion Institute, 2017