ZrB2-based ultrahigh-temperature ceramic with various SiC particle size: Microstructure, thermodynamical behavior, and mechanical properties

This study investigated the influences of WC and HfB2 additives along with SiC reinforcement (with various particle sizes) on densification, microstructure, and mechanical properties of ZrB2-SiC composites. The results showed that WC and HfB2 addition formed a solid solution of (Zr,W,Hf)B-2 with a core-shell structure, whereas the remaining WC transformed into WB. Moreover, nano-sized SiC caused a much better impact on densification compared to micro-sized SiC. A small fraction of localized phases like ZrC, HfB, and (Hf,Zr)C in the form of solid solution were also formed. The maximum room temperature flexural strength and the fracture toughness of the sample containing 150 nm SiC and 8.9 wt.% WB were measured to be 682 +/- 17 MPa and 6.5 +/- .3 MPa m(1/2), respectively