Fabrication of SiC reticulated porous ceramics with dense struts by in-situ generation of SiC

Abstract

SiC reticulated porous ceramics have been widely utilized as filters in the smelting industry. To address the problem of hollow ceramic struts and improve the strength and thermal shock resistance of SiC reticulated porous ceramics, a one-step coating process was carried out using slurries with SiC, metallic Si and various carbon sources (carbon spheres, carbon black, and flake graphite). The effect of the carbon sources on the rheological behavior of the coating slurries was investigated, as well as the relationship between the rheological behavior of the slurries and the structure of the green bodies. The hollow struts and flaws resulting from the combustion of polymer templates were then filled with SiC whiskers formed by the reaction between Si and carbon sources during heating. Among the carbon sources, the carbon spheres significantly stimulated the growth of the SiC whiskers, which filled the voids and flaws. After heating at 1550 °C, the SiC reticulated porous ceramics prepared with Si and carbon spheres reached a porosity of 80%, compressive strength of 1.85 MPa, and residual compressive strength rate of 81%. In industrial tests, the fabricated SiC reticulated porous ceramics were used as filters to effectively remove inclusions in molten copper. Importantly, the structure of the SiC filters remained intact after use.