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On-line version ISSN 1980-5373
IZHEVSKYI, V.A.; GENOVA, L.A.; BRESSIANI, A.H.A. and BRESSIANI, J.C.. Liquid phase sintered SiC. Processing and transformation controlled microstructure tailoring. Mat. Res. [online]. 2000, vol.3, n.4, pp.131-138. ISSN 1980-5373. http://dx.doi.org/10.1590/S1516-14392000000400007.
Microstructure development and phase formation processes during sintering of silicon carbide based materials with AlN-Y2O3, AlN-Yb2O3, and AlN-La2O3 sintering additives were investigated. Densification of the materials occurred by liquid-phase sintering mechanism. Proportion of a- and b-SiC powders in the initial mixtures was a variable parameter, while the molar ratio of AlN/RE2O3, and the total amount of additives (10 vol. %) were kept constant. Shrinkage behavior during sintering in interrelation with the starting composition of the material and the sintering atmosphere was investigated by high temperature dilatometry. Kinetics of b-SiC to a-SiC phase transformation during post-sintering heat treatment at temperatures 1900-1950 °C was studied, the degree of phase transformation being determined by quantitative x-ray analysis using internal standard technique. Evolution of microstructure resulting from b-SiC to a-SiC transformation was followed up by scanning electron microscopy on polished and chemically etched samples. Transformation-controlled grain growth mechanism similar to the one observed for silicon nitride based ceramics was established. Possibility of in-situ platelet reinforced dense SiC-based ceramics fabrication with improved mechanical properties by means of sintering was shown.
Keywords : silicon carbide; ceramics; sintering; phase formation; microstructure; phase transformation; in-situ reinforcement.