The influence of firing parameters on the formation of nitride phases in nitride bonded silicon carbides

Abstract

In this study the influence of parameters like heating rate and dwell time on the kinetics of the nitridation process and microstructural development of nitride bonded silicon carbides was investigated. A combination of in situ and ex situ methods was used with special focus on the spatial formation of nitride phases.The nitridation of SiC–Si green bodies was carried out at heating rates of 1, 3 and 5 K/min and different multi-stage firing profiles were used. All samples were analysed by Raman spectroscopy and SEM. It was observed that with higher heating rates the number of α-Si3N4 whiskers in the matrix was reduced. An effect that was achieved with the direct firing to a temperature above the silicon melting point at 1409 °C as well. However, high heating rates have the disadvantage of a higher amount of residual silicon in the matrix after cooling.