EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

In this study, dense ZrB2-SiC composites were fabricated using Field Assisted Sintering Technology (FAST). The composites containing 25 vol% SiC particles were prepared by in situ reaction of ZrSi2, B4C and carbon black powders, which is a method to densify ZrB2-based composites at low temperatures. Furthermore, rare-earth (RE) oxides were used to improve the mechanical properties of ZrB2-SiC composites. The microstructures of the ZrB2 based composites were characterized by X-Ray Diffraction and Scanning Electron Microscopy. Both the room temperature (hardness, strength, fracture toughness) and high temperature (ablation resistance) properties were investigated. The results showed that homogeneous microstructure and nearly fully dense ZrB2-25vol.%SiC composites with a relative density above 99% were obtained after sintering at the temperature of 1600°C under the pressure of 70 MPa for 10 min. During sintering, the additives were completely transformed into ZrB2 and SiC particles, which were homogeneously distributed in the ZrB2 matrix. The RE-based additives were also unifomrly distributed at the grain boundaries of ZrB2. The mechanical properties of ZrB2-SiC composite, such as hardness, strength and fracture toughness, were slightly improved by the addition of RE oxides. Most importantly, the ablation resistance of ZrB2-based materials was significantly improved by the addition of RE oxides, and further improved with their increasing amounts.