Abstract:The oxidation behavior of electroconductive TiN/O′-Sialon ceramics prepared using high titania slag as main starting material was studied at 1 200−1 300 °C in air. The isothermal and non-isothermal oxidation processes were investigated by DTA−TG. Phase compositions and morphologies of the oxidized products were analyzed by XRD, SEM and EDS. The results indicate that the oxidation of TiN and O′-Sialon occurs at about 500 °C and 1 050 °C, respectively. After oxidation at 1 200−1 300 °C, a protective scale that consists of Fe₂MgTi₃O₁₀, SiO₂ and TiO₂ is formed on the surface of the materials, which effectively prevents the oxidation process. The formation of a protective scale is relative to TiN content and apparent porosity of the samples, the amount of SiO₂ and amorphous phase in the oxidation product. At the initial oxidation stage, the oxidation kinetics of the materials follows perfectly the linear law with the apparent activation energy of 1.574×10⁵ J/mol, and at the late-mid stage, the oxidation of the samples obeys the parabolic law with the apparent activation energy of 2.693×10⁵ J/mol. With the increase of TiN content, mass gain of the materials increases significantly.

Key words: TiN/O′-Sialon; high titania slag; electroconductive ceramics; oxidation behavior