Preparation and properties of dense ZrB 2 composite reinforced by elongated SiC and Al 3 BC 3 grains

Dense ZrB 2 ‐SiC‐Al 3 BC 3 ultra‐high temperature ceramic composite was fabricated by hot pressing sintering at 1900°C for 1 hour under a pressure of 20 MPa using Zirconium diboride (ZrB 2 ) as the raw material and a powder mixture of SiC, B 4 C, Al, and carbon as the sintering additive. Al and B 4 C underwent in situ reaction with carbon powder to produce Al 3 BC 3 , which promoted the densification of ZrB 2 ceramic. SiC grains were found to be elongated during sintering. The ZrB 2 ‐SiC‐Al 3 BC 3 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 ZrB 2 ‐SiC‐Al 3 BC 3 composite was studied in air at 1500°C for 1 hour. A continuous layer of oxides consisting of a mixture of SiO 2 , Al 2 SiO 5 , and Al 2 O 3 was formed on the surface of the ZrB 2 ‐SiC‐Al 3 BC 3 composite. This layer of oxides efficiently prevented oxygen from diffusing into the specimens during oxidation, which improved the oxidation resistance of the ZrB 2 ceramics.