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 beta-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. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.