Effect of SiC content on microstructure evolution of ZrB₂-ZrC-SiC ceramic in sol-gel process

To investigate the effect of SiC content on microstructure evolution of ZrB₂-ZrC-SiC ceramic in sol-gel process. ZrB₂-ZrC-SiC powders with different amounts of SiC were in-situ synthesized at 1500 °C through sol-gel method. Ceramization process and effect of SiC content on the microstructure evolution of the ceramic powders were investigated. During the ceramization process, carbon content plays an important role in tailoring the compositions of ZrB₂-ZrC-SiC ceramics by enhancing the growth of ZrC and SiC. ZrB₂-ZrC-SiC ceramic phases, fine ceramic particles and narrow particle size distribution can be obtained with the increasing of carbon content as a result of its space steric effect. Moreover, grain size of all the phases decreased gradually with the increase of SiC content. Additionally, the introduction of SiC restrained the growth of ZrB₂ but prompted the growth of ZrC. Particle size distribution was significantly narrowed and the average particle size of the powders was reduced from 610 to 200 nm when SiC content increased from about 7 wt% to 50 wt%. With the increasing of SiC content, the enhanced synergistic space steric and grain-boundary pinning effect of SiC and carbon contribute to the generation of uniform and fine ZrB₂, ZrC and SiC ceramic particles with an average size of 200 nm.