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Polysilazane-derived micro/nano Si3N4/SiC composites

Zemanova, M. and Lecomte, Emmanuel and Sajgalik, Pavol and Riedel, Ralf (2002):
Polysilazane-derived micro/nano Si3N4/SiC composites.
In: Journal of the European Ceramic Society, (16), 22. Elsevier, pp. 2963-2968, [Article]

Abstract

The pyrolised polysilazanes poly(hydridomethyl)silazane NCP 200 and poly(urea)silazane CERASET derived Si–C–N amorphous powders were used for preparation of micro/nano Si3N4/SiC composites by hot pressing. Y2O3–Al2O3 and Y2O3–Yb2O3 were used, as sintering aids. The resulting ceramic composites of all compositions were dense and polycrystalline with fine microstructure of average grain size <1 μm of both Si3N4 and SiC phases. The fine SiC nano-inclusions were identified within the Si3N4 micrograins. Phase composition of both composites consist of α, β modifications of Si3N4 and SiC. High weight loss was observed during the hot pressing cycle, 12 and 19 wt.% for NCP 200 and CERASET precursors, respectively. The fracture toughness of both nanocomposites (NCP 2000 and CERASET derived) was not different. Indentation method measured values are from 5 to 6 MPa m1/2, with respect to the sintering additive system. Fracture toughness is slightly sensitive to the SiC content of the nanocomposite. Hardness increases with the content of SiC in the nanocomposite. The highest hardness was achieved for pyrolysed CERASET precursor with 2 wt.% Y2O3 and 6 wt.% Yb2O3, HV ≅23 GPa. This is a consequence of the highest SiC content as well as the chemical composition of additives.

Item Type: Article
Erschienen: 2002
Creators: Zemanova, M. and Lecomte, Emmanuel and Sajgalik, Pavol and Riedel, Ralf
Title: Polysilazane-derived micro/nano Si3N4/SiC composites
Language: English
Abstract:

The pyrolised polysilazanes poly(hydridomethyl)silazane NCP 200 and poly(urea)silazane CERASET derived Si–C–N amorphous powders were used for preparation of micro/nano Si3N4/SiC composites by hot pressing. Y2O3–Al2O3 and Y2O3–Yb2O3 were used, as sintering aids. The resulting ceramic composites of all compositions were dense and polycrystalline with fine microstructure of average grain size <1 μm of both Si3N4 and SiC phases. The fine SiC nano-inclusions were identified within the Si3N4 micrograins. Phase composition of both composites consist of α, β modifications of Si3N4 and SiC. High weight loss was observed during the hot pressing cycle, 12 and 19 wt.% for NCP 200 and CERASET precursors, respectively. The fracture toughness of both nanocomposites (NCP 2000 and CERASET derived) was not different. Indentation method measured values are from 5 to 6 MPa m1/2, with respect to the sintering additive system. Fracture toughness is slightly sensitive to the SiC content of the nanocomposite. Hardness increases with the content of SiC in the nanocomposite. The highest hardness was achieved for pyrolysed CERASET precursor with 2 wt.% Y2O3 and 6 wt.% Yb2O3, HV ≅23 GPa. This is a consequence of the highest SiC content as well as the chemical composition of additives.

Journal or Publication Title: Journal of the European Ceramic Society
Journal volume: 22
Number: 16
Publisher: Elsevier
Uncontrolled Keywords: Precursors-organic, Si3N4/SiC, Composites, Microstructure-final, Hardness, Toughness, Phase development
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: 20 Nov 2008 08:19
License: [undefiniert]
Funders: Present work was partly supported by the DAAD, Bonn, Slovak–German R&D Program, project X292.11 and Slovak Grant Agency VEGA, under the project No. 2/5118/00.
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