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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