Chemische Reaktionen in Gasentladungen. II. Über die Bildung von Halogenosiloxanen bei der Reaktion von SiX₄ (X = Cl, Br) mit Sauerstoff

Abstract

Die Reaktion von SiX4 mit O2 wurde in einer Niederdruckgasentladung sowie, thermisch aktiviert, bei 1000°C bis 1100°C untersucht. Diese Umsetzung ist bei der industriellen Fertigung von Lichtleitfasern von Bedeutung. Es wurde die Bildung einer Vielzahl von Halogenosiloxanen (kettenförmige, cyclische, oligocyclische) nachgewiesen. Der Anteil sauerstoffreicher Verbindungen steigt mit steigender Temperatur. Die Produktverteilung bei der Reaktion in einer Gasentladung unterscheidet sich wesentlich von der bei thermischer Aktivierung. Eine Abschätzung der thermodynamischen Stabilitäten der Halogenosiloxane wird gegeben. Sie läßt erwarten, daß diese Verbindungen metastabil sind bezüglich des Zerfalls in SiX4 und SiO2.

BAC-MP4 Predictions of Thermochemistry for Gas-Phase Compounds in the Si−H−O−Cl System

“…Consequently, efforts to develop models capable of predicting silica formation rates must include chemical reactions at an elementary level. The high temperatures used indicate that a large number of silicon-containing species may be involved, including silicon oxyhalides and compounds containing multiple silicon atoms. − In contrast with silane oxidation/combustion, which has been extensively studied, very little is known about the thermochemistry and kinetics of species involved in SiCl 4 oxidation. Thermodynamic data (heats of formation, entropies, and heat capacities) for silicon oxyhalides are almost totally unavailable; in the Si−O−Cl system of monomeric silicon compounds, only two oxychloride species have been characterized: ClSiO , and Cl 2 SiO. − Reaction rates relevant to SiCl 4 oxidation in the literature largely concern either qualitative observations or global reaction rates. ,− Several investigations of the pyrolysis of chlorinated silanes have recently appeared, − however, and reaction rates of SiCl 2 and SiCl 3 with molecular oxygen have been reported.…”

Identification and Characterization of Monomeric, Volatile SiCl3NH2 as Product of the Reaction between SiCl4 and NH3: An Important Intermediate on the Way to Silicon Nitride?

“…From the reaction of silicon tetrachloride with oxygen, it is known that the highly reactive species SiOCl 2 is involved in the primary step of the reaction 7. Another example for a reactive intermediate is trichlorosilanol SiCl 3 OH, which was monitored in the reaction of SiCl 4 and H 2 O 8. Another reaction that is reasonably closely related to the reaction of SiCl 4 with NH 3 is the ammonolysis of BCl 3 .…”

Reaction Mechanism of Chlorosiloxane Ring Formation from SiCl4 and O2

“…The reaction of SiCl 4 with O 2 is of great technological importance for the chemical vapor deposition (CVD) of solid SiO 2 films used in the microelectronics industry and synthesis of the ceramic powders. − The basic reaction occurs when the mixture of O 2 with SiCl 4 , in a tube of about 30 cm length, is heated above 1000 °C. , However, in the temperature range of 800−1000 °C, the resulting product consists of a multitude of chlorosiloxanes of the general formula Si x O y Cl z . , These chlorosiloxanes have a variety of shapes and sizes ranging from chains and rings to oligocyclic and polycyclic shapes. A large number of chlorosiloxanes were identified by mass spectrometry. − These chlorosiloxanes are intermediate compounds formed in the course of the reaction because of the partial replacement of Cl atoms in SiCl 4 by oxygen atoms.…”