Thermodynamics and kinetics of methyltrichlorosilane decomposition
Silicon carbide (SiC) deposition for oxidation- and corrosion-resistant coatings typically uses methyltrichlorosilane (MTS) as a starting reactant. Little is known about the temperature and pressure dependence of the unimolecular decomposition of MTS. In this work, transition-state and unimolecular reaction theory are used to estimate the reaction rates for three MTS decomposition pathways: (1) MTS [yields] SiCl[sub 3] + CH[sub 3], (2) MTS [yields] CH[sub 2]SiCl[sub 3] + H, and (3) MTS [yields] C1[sub 2]Si=CH[sub 2] + HCl. The high-pressure rate constants for these reactions are in the ratio 0.865:0.118:0.017 at 1500 K (typical SiC deposition temperature), indicating that organosilicon compounds comprise approximately 14% of the products. The rate of Reaction (1), which is the dominant decomposition pathway, after correction to 1 atm pressure, is a factor of 4 lower than the only reported rate for MTS decomposition, indicating that additional experimental data are required to confidently assign the rate constant. The pressure dependence of Reaction (1) shows that reducing the pressure from 1 atm to 25 torr (currently under study for low-temperature SiC chemical vapor deposition) results in a ten-fold reduction in MTS decomposition rate.
- Research Organization:
- Sandia National Labs., Livermore, CA (United States)
- Sponsoring Organization:
- DOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 6712740
- Report Number(s):
- SAND-93-8464; CONF-930571--6; ON: DE93006975
- Country of Publication:
- United States
- Language:
- English
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360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
CARBIDES
CARBON COMPOUNDS
CHEMICAL COATING
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMICAL VAPOR DEPOSITION
DECOMPOSITION
DEPOSITION
HYDRIDES
HYDROGEN COMPOUNDS
KINETICS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC SILICON COMPOUNDS
REACTION KINETICS
SILANES
SILICON CARBIDES
SILICON COMPOUNDS
SURFACE COATING