Densification, microstructure and mechanical properties of ZrB2-SiCw ceramic composites

ZrB2-SiCw composites were prepared through hot-pressing at a low temperature of 1800 degrees C, and Al2O3 Plus Y2O3 were added as sintering aids. Analysis revealed that additives may react with impurities (i.e. surface oxygen impurities and residual metallic impurities) to form a transient liquid phase, thus promote the sintering and densification of ZrB2-SiCw composites. The content of additives was found to have a significant influence on the sinterability, microstructure and mechanical properties of ZrB2-SiCw composites. ZrB2-SiCw composite prepared with a small amount of additives (3 vol.%) provided the optimal combination of microstructure (relative density of 98.3%) and excellent properties, including flexural strength of 783 MPa and fracture toughness of 6.7 MPa m(1/2). With further addition of additives, SiC whiskers were inclined to gather together and be enveloped by excessive liquids to form core-rim-like structures, which lead to little decrease in mechanical properties. (C) 2009 Elsevier Ltd. All rights reserved.