Microscopic Studies of Oxidised Si3N4-based Ceramics

Scanning electron microscopy (SEM), energy- and wavelength-dispersive microanalysis (EDAX and WDS), light microscopy and X-ray diffraction (XRD) techniques were used to analyse the oxide scales formed on silicon nitride-based ceramics during oxidation in air at temperatures up to 1500°C. A group of hot-pressed Si3N4-based ceramics with 1-3 mass % Al2O3, 5-9 mass % Y2O3 and 0-50 mass % TiN was used for oxidation experiments. The effects of the content of sintering aids (Al2O3 and Y2O3) and the content and grain size of the particulate addition (TiN) on the composition, structure and protective properties of oxide layers were investigated.