Proceedings of the Twelfth European Conference on Chemical Vapour Deposition
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J. Phys. IV France 10 (2000) Pr2-43-Pr2-48
DOI: 10.1051/jp4:2000206

In-situ FTIR spectroscopic monitoring of a CVD controlled Si-N-O fibre growth process

U. Vogt¹, A. Vital², W. Graehlert², M. Leparoux², H. Ewing^{1, 3}, A. Beil⁴, R. Daum⁴ and H. Hopfe<sup>2

1</sup>  Swiss Federal Laboratories for Materials Testing and Research, Section High Performance Ceramics, 8600 Dübendorf, Switzerland
²  Fraunhofer Institute of Material and Beam Technology, Winterbergstrasse 28, 01277 Dresden, Germany
³  University of Strathclyde, Department of Mechanical Engineering, Glasgow G1 1XN, U.K.
⁴  Bruker Saxonia Analytik GmbH, Permoserstrasse 15, 04318 Leipzig, Germany

Abstract
High strength and high temperature composite materials such as CMCs represent a very promising family of future materials. A high temperature CVD-process has been developed to produce a new type of high-performance amorphous silicon-oxynitride (Si-N-O) fibres. The fibres were grown on a Sic substrate at 1450°C exposing a stoichiometric precursor powder mixture of SiO₂ + SiC, doped with 10 wt% Ti powder to flowing NH₃.
To improve CVD process control an in-situ FTIR monitoring system is in development. For application of a FTIR based monitoring to the fibre growth process a specific optical adaptation has been designed onto the growth reactor. The optical set-up allows an almost simultaneous in-situ measurement of the transmission and emission of the hot gas atmosphere just above the precursor powder mixture. In addition to the decomposition of NH₃, different reaction products have been identified, such as CO, HCN and CH₄. Gaseous Si-O species could be detected which are responsible for the silicon transport in the gas phase from the solid SiO₂ precursor powder to the fibre growth position. The assessment of the SiO bands has been supported by additional experiments which promote the formation of gaseous SiO.

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