Oxidation behavior of LPS-SiC ceramics sintered with AlN/Y2O3 as additive

Abstract In this work, the oxidation behavior of SiC ceramics sintered with additives based on AlN–Y 2 O 3 system was investigated. SiC ceramics doped with different AlN:Y 2 O 3 contents of 8.4:11.6 wt.% or 2.2:17.8 wt.% were sintered at 2080 °C for 1 h under nitrogen atmosphere, obtaining ceramics with relative density near to 96% in both compositions. Samples were oxidized at 1200 °C, 1300 °C or 1400 °C in air for up to 120 h. Oxidation was monitored by the weight gain of the samples as function of exposition time and temperature. A parabolic growth of the oxidation layer has been observed and the coefficient of the growth rate has been determined by relating the weight gain and the surface area. In oxidation testing performed at 1200 °C, samples containing lower Y 2 O 3 amounts showed greater oxidation resistance; however, by raising the temperature (to 1400 °C), the samples containing higher Y 2 O 3 amounts showed greater oxidation resistance. The oxidized layer characterized by X-ray diffraction presented SiO 2 and Y 2 Si 2 O 7 as crystalline phases. Furthermore, the activation energy for oxidation of 780 kJ/mol and 405 kJ/mol for AlN:Y 2 O 3 contents of 8.4:11.6 wt.% or 2.2:17.8 wt.%, respectively.