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Mullite Diffusion Barriers for SiC-C/C Composites Produced by Pulsed Laser Deposition

Published online by Cambridge University Press:  10 February 2011

H. Fritze ,
A. Schnittker ,
T. Witke ,
C. Rüscher ,
S. Weber ,
S. Scherrer ,
B. Schultric  and
G. Borchardt
H. Fritze
Affiliation:
Institut für Allgemeine Metallurgie, Technische Universität Clausthal, Robert-Koch-Straße 42, D-38678 Clausthal-Zellerfeld, Germany, [email protected]
A. Schnittker
Affiliation:
Institut für Allgemeine Metallurgie, Technische Universität Clausthal, Robert-Koch-Straße 42, D-38678 Clausthal-Zellerfeld, Germany, [email protected]
T. Witke
Affiliation:
Fraunhofer-Institut für Werkstoffphysik und Schichttechnologie, Winterbergstraße 28, D-01277 Dresden, Germany
C. Rüscher
Affiliation:
Institut für Mineralogie, Universität Hannover, Welfengarten 1, D-30167 Hannover, Germany
S. Weber
Affiliation:
Laboratoire de Métallurgie Physique et Sciences des Matériaux, Ecole des Mines de Nancy, Parc de Saurupt, F-54042 Nancy Cedex, France
S. Scherrer
Affiliation:
Laboratoire de Métallurgie Physique et Sciences des Matériaux, Ecole des Mines de Nancy, Parc de Saurupt, F-54042 Nancy Cedex, France
B. Schultric
Affiliation:
Fraunhofer-Institut für Werkstoffphysik und Schichttechnologie, Winterbergstraße 28, D-01277 Dresden, Germany
G. Borchardt
Affiliation:
Institut für Allgemeine Metallurgie, Technische Universität Clausthal, Robert-Koch-Straße 42, D-38678 Clausthal-Zellerfeld, Germany, [email protected]
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Abstract

Pulsed Laser Deposition (PLD) allows the ablation of nonconductive and high melting point target materials and the preparation of films with complex composition. High energy impact leads to melting and evaporation of the target material in a single step. In case of mullite ablation, the flux of the metal components is stoichiometric. Under reduced pressure the oxygen content in the layers decreases. However, after a short oxidation treatment, the formation of mullite in the coating is completed, as confirmed by IR spectroscopy and XRD investigations. For a commercial Si-SiC precoated C/C material, the effectiveness of additional PLD mullite layers as outer oxidation protection is tested in the temperature range 773 K < T < 1873 K. Mullite coatings with a thickness of 2.5 pm improve the oxidation behaviour significantly. Because of SiO2 formation at the mullite-SiC interface, all samples exhibited a mass increase upon oxidation. For oxidation durations of three days, only amorphous SiO2 is formed at the mullite-SiC interface. The inward diffusion of oxygen across the outer mullite-containing layer controls the kinetics of the reaction, as was deduced from 18O diffusivity measurements in PLD mullite layers. At temperatures close to the eutectic temperature (1860 K), mullite can seal defects. The calculated oxidation rates resulting from the diffusion parameters in SiO2 and mullite are close to the thermogravimetric data.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 555: Symposium OO – Properties and Processing of Vapor-Deposited Coatings , 1998 , 79
Copyright
Copyright © Materials Research Society 1999

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