Effect of heating rate on the shrinkage and microstructure of liquid phase sintered SiC ceramics

This paper describes a study of shrinkage behavior in the liquid phase sintering of silicon carbide, SiC, using eutectic mixtures of Al2O3 + Dy2O3 and Al2O3+Yb2O3 as liquid-forming additives. A volume fraction 10% of these mixtures was added to the SiC and homogenized in an attrition mill. Sintering was performed in a horizontal dilatometer at 1800 degrees C for 60 min, applying heating rates of 10, 20 and 30 degrees C/min. The results indicate that these heating rates affected neither shrinkage nor microstructure, from the standpoint of the complete sintering cycle. However, significant differences occurred during the non isothermal sintering stage, leading to very different shrinkage results as a function of the heating rate. Higher heating rates produced lower shrinkage, and the work of final shrinkage occurred during the isothermal stage. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved. (AU)