Preparation and properties of dense ZrB2 composite reinforced by elongated SiC and Al3BC3 grains

Dense ZrB2-SiC-Al3BC3 ultra-high temperature ceramic composite was fabricated by hot pressing sintering at 1900 degrees C for 1 hour under a pressure of 20 MPa using Zirconium diboride (ZrB2) as the raw material and a powder mixture of SiC, B4C, Al, and carbon as the sintering additive. Al and B4C underwent in situ reaction with carbon powder to produce Al3BC3, which promoted the densification of ZrB2 ceramic. SiC grains were found to be elongated during sintering. The ZrB2-SiC-Al3BC3 composite exhibited excellent mechanical properties, such as high flexural strength of 589 +/- 147 MPa and fracture toughness of 7.81 +/- 1.09 MPa m(1/2). Oxidation behavior of the ZrB2-SiC-Al3BC3 composite was studied in air at 1500 degrees C for 1 hour. A continuous layer of oxides consisting of a mixture of SiO2, Al2SiO5, and Al2O3 was formed on the surface of the ZrB2-SiC-Al3BC3 composite. This layer of oxides efficiently prevented oxygen from diffusing into the specimens during oxidation, which improved the oxidation resistance of the ZrB2 ceramics.