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 degrees C and is complete at the temperature of 1900 degrees 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.