A novel: In situ synthesis of SiBCN-Zr composites prepared by a sol-gel process and spark plasma sintering

In the work reported here, SiBCN amorphous powders were first prepared by a mechanical alloying technique, employing cubic silicon, graphite and hexagonal boron nitride powders as raw materials. Zirconia was then introduced via sol-gel methods. The resulting powder composite was then consolidated via SPS sintering. The SPS sintering sample was evaluated using XRD, SEM and TEM. XRD reveals a chemical transformation wherein amorphous BN(C) and ZrO₂ form the primary ZrC and ZrB₂ phases after SPS processing along with SiC and BN(C). Thereafter ZrC reacts with BN(C) completely to form ZrB₂. The reaction starts at the temperature of 1500 °C and is complete at the temperature of 1900 °C. The fracture toughness of the sintered composites reaches 4.9 ± 0.2 MPa m^1/2 due to the presence of the laminated structure of the BN(C) phase.