Effects of adding Si3N4 whiskers to ZrB2-SiC ceramics on microstructure, mechanical properties and oxidation resistance

ZrB2-SiC-Si3N4w ceramics (ZSN(w)) were prepared via the hot-pressing sintering method. The bending strength and fracture toughness of ZSN(w) at room temperature reached to 520 +/- 24 MPa and 5.2 +/- 0.16 MPa m(1/2), respectively. The enhancement in mechanical properties is attributed to the grain refinement and attenuation of grain boundary induced by the homogeneous distribution of Si3N4 whiskers. The oxidation resistance of ZSN(w) were conducted at 1500 degrees C in an air atmosphere. Remarkably, after 10 h of oxidation, ZSN(w) remained excellent strength and toughness reaching at 589 +/- 26 MPa and 4.8 +/- 0.12 MPa m(1/2), respectively. This oxidation resistance of ZSN(w) was mainly attributed to the gain refinement induced by Si3N4 whiskers, which effectively reduced the voids within the ceramic matrix. Therefore, this process promoted the densification and homogenization of the SiO2 protective barriers, accompanied with hindering the inward permeation of oxygen and the outward release of oxides.