Investigation on Using Andalusite and Kaoline Precursors for X-Sialon Formation via SRN Process with presence of Y2O3

Sialon ceramics are widely used in industrial applications because of high corrosion and oxidation resistance and high temperature properties. On the other hand, due to high costs of processing and raw materials, these materials used for special applications. The oxidation resistance of sialons is higher than that of Si3N4. Comparison between sialons showed that the highest amount of oxygen is available in x phase, therefore the oxidation resistance of x phase is higher than the others. X-sialon exhibits excellent chemical stability in contact with iron-based alloys at 1200°C. In this research, andalusite, kaolin, elemental Si powder and α-alumina were used as raw materials and the effects of aluminosilicate sources on the SRN process for x-sialon formation, with and without Y2O3, were studied. In order to study x-sialon formation, the samples were analyzed by XRD in different temperature and the reaction sequence of samples of andalusite precursor determined by DSC results. Results showed that in spite of more nitridation of Si in kaolin precursor samples, Y2O3 restricted nitridation process in all samples. In overall view, andalusite is more suitable precursor for x silaon formation via SRN process in comparison with kaolin, and Y2O3 leads to facilitate formation of x sialon from reaction between mullite and Si3N4. α-alumina is not appropriate source to supply lack of Al in component and it remains especially in kaolin precursor samples.