THE EFFECT OF NITROGEN-CONTENT ON THE SINTERING BEHAVIOR AND PROPERTIES OF SIALON PREPARED FROM KAOLIN

The sintering of powders with variable nitrogen content prepared from the carbothermal reduction and nitridation of kaolin has been studied. With increasing nitrogen uptake in the starting powder, the refractor iness and the fusion point increase. The coefficient of linear thermal expansion decreases linearly with the nitrogen content of the sintere d product. The product with 80% theoretical nitrogen has good oxidatio n resistance. The oxidation rate is parabolic, and the product contain s mullite, cristobalite, and a glass. The X-sialon phase oxidises pref erentially to -sialon.