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Crystallization of Polymer-Derived Silicon Carbonitride at 1873 K under Nitrogen Overpressure

Friess, Martin and Bill, Joachim and Golczewski, Jerzy and Zimmermann, André and Aldinger, Fritz and Riedel, Ralf and Raj, Rishi (2002):
Crystallization of Polymer-Derived Silicon Carbonitride at 1873 K under Nitrogen Overpressure.
In: Journal of the American Ceramic Society, Wiley, pp. 2587-2589, 85, (10), ISSN 0002-7820, [Online-Edition: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00503.x],
[Article]

Abstract

The chemical stability of an amorphous silicon carbonitride ceramic, having the composition 0.57SiC·0.43Si3N4·0.49C is studied as a function of nitrogen overpressure at 1873 K. The ceramic suffers a weight loss at pN2 < 3.5 bar (1 bar = 100 kPa), does not show a weight change from 3.5 to 11 bar, and gains weight above 11 bar. The structure of the ceramic changes with pressure: it is crystalline from 1 to 6 bar, amorphous at ∼10 bar, and is crystalline above ∼10 bar. The weight-loss transition, at 3.5 bar, is in excellent agreement with the prediction from thermodynamic analysis when the activities of carbon, SiC, and Si3N4 are set equal to those of the crystalline forms; this implies that the material crystallizes before decomposition. The amorphous to crystalline transition that occurs at ∼10 bar, and which is accompanied by weight gain, is likely to have taken place by a different mechanism. A nucleation and growth reaction with the atmospheric nitrogen is proposed as the likely mechanism. The supersaturation required to nucleate α-Si3N4 crystals is calculated to be 30 kJ/mol.

Item Type: Article
Erschienen: 2002
Creators: Friess, Martin and Bill, Joachim and Golczewski, Jerzy and Zimmermann, André and Aldinger, Fritz and Riedel, Ralf and Raj, Rishi
Title: Crystallization of Polymer-Derived Silicon Carbonitride at 1873 K under Nitrogen Overpressure
Language: English
Abstract:

The chemical stability of an amorphous silicon carbonitride ceramic, having the composition 0.57SiC·0.43Si3N4·0.49C is studied as a function of nitrogen overpressure at 1873 K. The ceramic suffers a weight loss at pN2 < 3.5 bar (1 bar = 100 kPa), does not show a weight change from 3.5 to 11 bar, and gains weight above 11 bar. The structure of the ceramic changes with pressure: it is crystalline from 1 to 6 bar, amorphous at ∼10 bar, and is crystalline above ∼10 bar. The weight-loss transition, at 3.5 bar, is in excellent agreement with the prediction from thermodynamic analysis when the activities of carbon, SiC, and Si3N4 are set equal to those of the crystalline forms; this implies that the material crystallizes before decomposition. The amorphous to crystalline transition that occurs at ∼10 bar, and which is accompanied by weight gain, is likely to have taken place by a different mechanism. A nucleation and growth reaction with the atmospheric nitrogen is proposed as the likely mechanism. The supersaturation required to nucleate α-Si3N4 crystals is calculated to be 30 kJ/mol.

Journal or Publication Title: Journal of the American Ceramic Society
Volume: 85
Number: 10
Publisher: Wiley
Uncontrolled Keywords: silicon carbonitride, polymers/polymerization, crystals/crystallization, nitrogen
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: 26 Apr 2012 09:07
Official URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00503.x
Identification Number: doi:10.1111/j.1151-2916.2002.tb00503.x
Funders: R. Raj was supported by the Alexander von Humboldt Foundation in Germany, and he expresses his thanks to the Max Planck Institut fur Metallforschung, PML, Stuttgart, Germany, for hosting his visit.
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