Change in microstructures and physical properties of ZrB₂-SiC ceramics hot-pressed with a variety of SiC sources

ZrB₂-SiC ceramics were fabricated by hot pressing with a variety of SiC sources in order to examine the effect of the SiC size on the microstructures and physical properties, such as hardness and thermal conductivities, of ZrB₂-SiC composite ceramics. Three different ZrB₂-SiC ceramics, ZPS (ZrB₂-20 vol% polycarbosilane), ZFS (ZrB₂-20 vol% fine-grained SiC), and ZNS (ZrB₂-20 vol% nano-sized SiC), were prepared for this study. PCS is effectively transformed into β-SiC after hot pressing. By using PCS as a precursor for SiC, ZrB₂ particles are surrounded by fine particles of SiC, which results in the grain-growth inhibition of ZrB₂. The effects of the SiC size on the microstructures and the physical properties of ZrB₂-SiC ceramics were also investigated. ZrB₂-SiC ceramics were produced by using various SiC sources in order to investigate the grain-growth inhibition and the mechanical/thermal properties of ZrB₂-SiC. The sizes of ZrB₂ or SiC particles in the sintered bodies highly depend on the initial size of SiC. ZrB₂-SiC ceramics with smaller SiC show enhanced mechanical properties, consistently with the Hall-Petch relation. The thermal conductivities of ZrB₂-SiC ceramics with nano-SiC or PCS-derived SiC are higher than that of ceramics with conventional SiC, which can be explained by the percolation theory.