Microstructure, mechanical properties and thermal shock resistance of zirconium diboride containing silicon carbide ceramic toughened by carbon black

Abstract

ZrB 2–20 vol.%SiC ultrahigh temperature ceramic containing 5 vol.% carbon black of nanometer size (ZSC) was prepared by hot-pressing at 1900 °C. The effect of carbon black addition on the microstructure and mechanical properties was investigated. Compared to the ZrB 2–SiC ceramics, the fracture toughness was significantly improved whereas flexural strength and hardness of the ZSC ceramic were slightly degraded. The fracture toughness as high as 6.6 ± 0.5 MPa m 1/2 was much higher than that of monolithic ZrB 2 (2.3–3.5 MPa m 1/2) and ZrB 2–SiC ceramics (4.0–4.5 MPa m 1/2). The toughening mechanisms were the crack deflection, bridging and branching. Furthermore, the effect of carbon black addition on the thermal shock resistance was systematically investigated and discussed.