Shock-tube study of the decomposition of tetramethylsilane using gas chromatography and high-repetition-rate time-of-flight mass spectrometry

Abstract

The decomposition of tetramethylsilane was studied in shock-tube experiments in a temperature range of 1270–1580 K and pressures ranging from 1.5 to 2.3 bar behind reflected shock waves combining gas chromatography/mass spectrometry (GC/MS) and high-repetition-rate time-of-flight mass spectrometry (HRR-TOF-MS). The main observed products were methane (CH₄), ethylene (C₂H₄), ethane (C₂H₆), and acetylene (C₂H₂). In addition, the formation of a solid deposit was observed, which was identified to consist of silicon- and carbon-containing nanoparticles. A kinetics sub-mechanism with 13 silicon species and 20 silicon-containing reactions was developed. It was combined with the USC_MechII mechanism for hydrocarbons, which was able to simulate the experimental observations. The main decomposition channel of TMS is the Si–C bond scission forming methyl (CH₃) and trimethylsilyl radicals (Si(CH₃)₃). The rate constant for TMS decomposition is represented by the Arrhenius expression k_total[TMS → products] = 5.9 × 10¹² exp(−267 kJ mol⁻¹/RT) s⁻¹.