Effect of pre-processing treatment of initial powders on the main properties of the sintered ceramics in the system Si_3N_4-Al_2O_3-SiO_2-Y_2O_3. II. Structure and properties of sintered ceramics

摘要

The effect of surface composition modification of the high-purity α-Si_3N_4 powder by means of various physical and chemical treatment on the properties of the resulting sintered ceramics in the system Si_3N_4-Al_2O_3-SiO_2-Y_2O_3 was investigated. Flexural strength and oxidation resistance in the temperature range 20-1350°C were measured for the sintered materials. Correlations for these parameters as well as for the phase composition with the surface chemical composition of the initial silicon nitride powder, surface oxygen content in particular, were established. It was shown that even the slightest changes of the latter cause substantial alterations of intergranular phase composition. The highest properties, mostly the high temperature ones, were obtained after thermal oxidation treatment of the initial powders.