Preparation and Characterization of X-O'Sialons Ceramics Produced by the Sintering

摘要

X-phase-O'-sialon ceramics were produced by simultaneous nitridation and sintering of corundum-silicon-clay mixture. The mixture of starting materials was concurrently milled in attritor in isopropanol. The influence of the time of milling on nitridation and sialons yield has been tested. It has been found that these parameters changed significantly the rate of nitridation, phase composition and homogenity of the resulted product. The final composition consisted mainly of X-sialon and O'-sialon; process parameters changed the ratio of the both phases. Mullite and Si_3N_4 were present as transient phases after the reaction at 1400 deg C. Hardness, fracture toughness and elastic properties of the ceramics were scattered and were influenced more by the resulted microstructure than phase composition. Ultrasonic pulse-echo measurement revealed concurrency of sintering and nitridation during heating up to 1400 deg C.