Oxidation behaviour of laminated BN/ZrB2–SiC ceramics

Laminated BN/ZrB2-SiC ceramics were successfully fabricated by tape casting and hot-pressing. The oxidation behaviour of the ceramics at 1300, 1500 and 1600 degrees C in air was investigated. The results indicated their flexural strength and fracture toughness reached up to 583 +/- 27 MPa and 16.1 +/- 0.4 MPa m(1/2), respectively, after oxidation at 1300 degrees C for 0.5 h. These values were higher than those obtained at room temperature (381 +/- 31 MPa and 11.8 +/- 0.5 MPa m(1/2)). The improved mechanical properties could be attributed to the slight oxidation and healing effect to the defects of the SiO2 glassy layer produced during oxidation. At 1600 degrees C, the mechanical properties decreased constantly, which was attributed to the substantive oxidation and formation of a thick, porous ZrO2 layer under the thin, dense SiO2 layer.