A shock tube-laser flash photolysis study of the reaction carbonyl sulfide + sulfur .dblharw. carbon monoxide + sulfur dimer

Abstract

The reaction of S atoms with COS was studied behind reflected shock waves in the temperature range 1200 K 5 T 5 1670 K a t pressures between 0.6 and 2.0 bar. The S atoms were generated by UV laser flash photolysis of mixtures containing 50-200 ppm COS diluted in Ar and were monitored by atomic resonance absorption spectroscopy. From the decay of the S atom absorption signals the rate coefficient of the reaction COS + S + CO + S2 (R2), k2 = 6.0 X 1013 exp(4560 K/T) cm3 mol-' s-I, was determined by assuming first-order kinetics. In addition, quasi-stationary S atom profiles obtained during the high-temperature pyrolysis of 100 ppm COS in Ar were analyzed. Based on a simplified kinetic model, the given k2 value was verified to be valid for temperatures up to T = 2180 K.

High‐temperature kinetics of some Si‐ and Cl‐containing ceramic precursors

“…SiCl 4 and SiHCl 3 , which are liquid at normal conditions, were evaporated in separate evaporation vessels. A detailed description of the experimental procedure can be found elsewhere [3,4].…”

“…A mixture of 100 ppm SiCl 4 /Ar was heated up by the reflected shock (RS) to T = 1113 K and p = 1.8 bar. The sudden increase of absorption at t = 0 s to a constant value of 25% is due to the molecular absorption by SiCl 4 . This was also checked by additional low-temperature shock-tube experiments with SiCl 4 /Ar mixtures.…”

“…The thermal decomposition of SiHCl 3 was studied in a very similar way to that of SiCl 4 . At temperatures 1500 ≤ T ≤ 3300 K and pressures 0.8 ≤ p ≤ 4.0 bar Cl-and Si-atoms were simultaneously measured together with H-absorptions at the L ␣ -line in mixtures of 0.5-5.0 ppm SiHCl 3 /Ar.…”

“…Less than 1 ppm Si 2 H 6 and SiH 4 were used as well-known Siatom sources. At temperatures T > 1500 K, Si 2 H 6 decomposes within a few microseconds, forming SiH 4 and SiH 2 , which subsequently dissociates into Si and H 2 [21]. SiH 4 highly diluted in Ar is known to produce instantaneously Si atoms at temperatures T ≥ 2000 K [22,23].…”

“…Therefore, detailed information about thermodynamic and chemical reaction data are essential. For silanes such as SiH 4 or Si 2 H 6 some reaction data are available, but there exists a lack of data for chlorosilanes such as SiCl 4 or SiHCl 3 . Aim of this work is to review our recent experimental results of the thermal decomposition, of the photodissociation, and of some bimolecular reactions of Si-and Cl-containing precursor gas mixtures.…”