Processing and properties of silica-bonded porous nano-SiC ceramics with extremely low thermal conductivity

Silica-bonded porous nano-SiC ceramics with extremely low thermal conductivity were prepared by sintering nano-SiC powder-carbon black template compacts at 600-1200 degrees C for 2 h in air. The microstructure of the silica-bonded porous nano-SiC ceramics consisted of SiC core/silica shell particles, a silica bonding phase, and hierarchical (meso/macro) pores. The porosity and thermal conductivity of the silica-bonded porous nano-SiC ceramics can be controlled in the ranges of 8.5-70.2 % and 0.057-2.575 Wm(-1) K-1, respectively, by adjusting both, the sintering temperature and template content. Silica-bonded porous nano-SiC ceramics with extremely low thermal conductivity (0.057 Wm(-1) K-1) were developed at a very low processing temperature (600 degrees C). The typical porosity, average pore size, compressive strength, and specific compressive strength of the porous nanoSiC ceramics were similar to 70 %, 50 nm, 2.5 MPa, and 2.7 MPa.cm(3)/g, respectively. The silica-bonded porous nano-SiC ceramics were thermally stable up to 1000 degrees C in both air and argon atmospheres.