Kinetics of the Thermal Decomposition of Ethylsilane: Shock-Tube and Modeling Study

The
thermal decomposition of ethylsilane (H3SiC2H5, EtSiH3) is investigated behind reflected
shock waves and the gas composition is analyzed by gas chromatography/mass
spectrometry (GC/MS) and high-repetition-rate time-of-flight mass
spectrometry (HRR-TOF-MS) in a temperature range of 990–1330
K and pressure range of 1–2.5 bar. The unimolecular decomposition
of EtSiH3 is considered to be initiated via a molecular
elimination of H2 (H3SiC2H5 → H2 + HSiC2H5) followed
by reactions of cyclic silicon-containing species. The main observed
stable products were ethylene (C2H4) and silane
(SiH4). Measurements are performed with a large excess
of a silylene scavenger (C2H2) to suppress bimolecular
reactions caused by silylene (SiH2) and to extract unimolecular
rate constants. A kinetics mechanism accounting for the gas-phase
chemistry of EtSiH3 is developed, which consists of 24
Si-containing species, 31 reactions of Si-containing species, and
a set of new thermochemical data. The derived unimolecular rate constant
is represented by the Arrhenius expression kuni(T) = 1.96 × 1012 s–1 exp­(−205 kJ mol–1/RT). The experimental data is reproduced very well by simulations
based on the mechanism of this work and is in very good agreement
with literature values. It is shown that EtSiH3 is a promising
precursor for the synthesis of SiC nanoparticles.