ZrB2-SiCw ceramic composites synthesized by in situ reaction and spark plasma sintering

SiC whisker reinforced ZrB2-SiCw composites were prepared by sol-gel method and spark plasma sintering (SPS) with designed composition of 10-30 vol% SiCw. The ZrB2-SiCw composite powder was synthesized by sol-gel method using zirconium diboride, tetraethoxysilane (TEOS), and activated carbon as starting materials, then densified by SPS at 1700 degrees C under a pressure of 40 MPa for 5 minutes. The phase compositions and microstructures of ZrB2-SiCw composites were investigated by X-ray diffraction and scanning electron microscope, respectively. The relative density of ZrB2-SiCw composites increased from 83% to 98.5% with increasing SiCw contents from 10 vol% to 30vol% after sintering at 1700 degrees C without additional sintering additives. Meanwhile, the fracture toughness and flexural strength of as-obtained composites exhibited a similar trend as relative density. ZrB2-30vol% SiCw composite showed the highest fracture toughness of 6.1 MPam(1/2) and flexural strength of 350 MPa, which were attributed to the formation of SiC whisker.