Production of α/β sialon ceramics from silicon powder

SiAlON ceramics are the preferred materials in advanced technology applications with their superior mechanical and thermal properties. Although they are at the forefront with their superior features, their low usage rates and very high production costs. The aim of this doctoral thesis is to produce α/β-SiAlON ceramics by direct nitriding, which is the most economical synthesis method, without losing their properties. During the production process, the nitriding processes of the pellets prepared with metallic Si powder and different oxide additions (Yb, Y/Sm and Ce) were carried out with the reaction bonding technique in an atmosphere-controlled tube furnace. The particle size distribution of the silicon powder used in the studies and the Si/Si3N4 addition ratio in the mixture, the effect of nitriding temperature and residence time were examined separately for each additional oxide system used. After nitriding processes, characterization studies were carried out in the bodies and microstructure changes were examined. As a result of the studies, it has been determined that it is possible to produce SiAlON ceramics using metallic silicon powder (at sufficiently fast nitriding conditions). It has been determined that the most effective parameter in the production process is the type of additional oxide used in the mixtures, while the Si/Si3N4 powder ratio and section thickness used in the mixture are other effective parameters. It was determined that the nitriding regime (temperature and waiting time) for each oxide system used in the compositions was determined to be variable and process parameters should be established according to the additional oxide type.