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Thermal decomposition of poly(methylsilsesquecarbodiimide) to amorphous Si-C-N-ceramics

Gabriel, Andreas O. and Riedel, R. and Dreßler, W. and Reichert, S. and Gervais, C. and Maquet, J. and Babonneau, F. (1999):
Thermal decomposition of poly(methylsilsesquecarbodiimide) to amorphous Si-C-N-ceramics.
In: Chemistry of materials, 11 (2), ACS, pp. 412-420, [Article]

Abstract

This paper is based on the recent discovery that the thermal decomposition of poly(methylsilsesquicarbodiimide), [CH3Si(NCN)1.5]n, leads to amorphous silicon carbonitride (SiCN) ceramics. In the present study the polymer-to-ceramic transformation is characterized using analytical and spectroscopic methods. In particular, the structural transition from the molecular precursor to the final amorphous SiCN ceramic was studied by solid-state NMR spectroscopy. The coordination of the silicon atoms changes from CH3−Si(−NCN−)3 in the polysilylcarbodiimide precursor at room temperature to Si(−N<)4 in the X-ray amorphous reaction product formed at 1200 °C. This result implies the formation of amorphous silicon nitride (Si3N4). The remaining weight fraction is analyzed to be elemental carbon. According to bulk chemical analysis, the poly(methylsilsesquicarbodiimide)-derived SiCN is comprised of a mixture of 1 mol amorphous Si3N4 with 3 mol amorphous carbon. The molar ratio Si3N4/C = 1/3 is suitable for the formation of stoichiometric silicon carbide, which is expected thermodynamically at temperatures exceeding 1440 °C in 0.1 MPa N2. The pyrolysis behavior of the poly(silylcarbodiimide) and the formation of silicon carbonitride ceramics are compared to those of poly(silazanes).

Item Type: Article
Erschienen: 1999
Creators: Gabriel, Andreas O. and Riedel, R. and Dreßler, W. and Reichert, S. and Gervais, C. and Maquet, J. and Babonneau, F.
Title: Thermal decomposition of poly(methylsilsesquecarbodiimide) to amorphous Si-C-N-ceramics
Language: English
Abstract:

This paper is based on the recent discovery that the thermal decomposition of poly(methylsilsesquicarbodiimide), [CH3Si(NCN)1.5]n, leads to amorphous silicon carbonitride (SiCN) ceramics. In the present study the polymer-to-ceramic transformation is characterized using analytical and spectroscopic methods. In particular, the structural transition from the molecular precursor to the final amorphous SiCN ceramic was studied by solid-state NMR spectroscopy. The coordination of the silicon atoms changes from CH3−Si(−NCN−)3 in the polysilylcarbodiimide precursor at room temperature to Si(−N<)4 in the X-ray amorphous reaction product formed at 1200 °C. This result implies the formation of amorphous silicon nitride (Si3N4). The remaining weight fraction is analyzed to be elemental carbon. According to bulk chemical analysis, the poly(methylsilsesquicarbodiimide)-derived SiCN is comprised of a mixture of 1 mol amorphous Si3N4 with 3 mol amorphous carbon. The molar ratio Si3N4/C = 1/3 is suitable for the formation of stoichiometric silicon carbide, which is expected thermodynamically at temperatures exceeding 1440 °C in 0.1 MPa N2. The pyrolysis behavior of the poly(silylcarbodiimide) and the formation of silicon carbonitride ceramics are compared to those of poly(silazanes).

Journal or Publication Title: Chemistry of materials
Volume: 11
Number: 2
Publisher: ACS
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Dispersive Solids
Date Deposited: 19 Nov 2008 16:23
Funders: The authors gratefully acknowledge the Deutsche Forschungsgemeinschaft (DFG), Bonn, Germany, the Fonds der Chemischen Industrie, Frankfurt, Germany for financial support, as well as the Deutsche Akademische Austauschdienst (Bonn, Germany), and the Ministe`re des Affaires Etrange`res (Paris, France) through the Procope collaborative exchange program. CM980747C
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