Article ID Journal Published Year Pages File Type
1476375 Journal of the European Ceramic Society 2010 10 Pages PDF
Abstract

The effect of the Ar or N2 sintering atmosphere on the oxidation behaviour of pressureless liquid-phase-sintered (PLPS) α-SiC was studied. PLPS α-SiC specimens processed under Ar or N2 atmospheres were isothermally oxidized at 1100–1450 °C in air for up to 500 h, and their oxidation kinetics, activation energy, and rate-controlling mechanisms were compared. It was found that, regardless of the sintering atmosphere, the oxidation is passive due to the formation of oxide scales. In addition, below 1350 °C the oxidation is protective, with a kinetics that follows initially the arctan-rate law and then the parabolic-rate law. However, from 1350 °C onwards the oxidation becomes only semi-protective, with a kinetics that obeys the arctan-rate law briefly and then the paralinear-rate law. Furthermore, the activation energies and rate-controlling mechanisms are similar for the arctan and paralinear oxidations, but different for the parabolic oxidation. It was also observed that the N2-processed material oxidizes more slowly than the Ar-processed material below 1200 °C due to a greater crystallization of its oxide scale, whereas above 1200 °C the Ar-processed material is more oxidation-resistant due to greater viscosity of its oxide liquid. Implications concerning the optimization of the processing route of PLPS SiC for high-temperature applications in air are discussed.

Related Topics
Physical Sciences and Engineering Materials Science Ceramics and Composites
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