Electrical, thermal, and mechanical properties of porous SiC-nitride composites

Abstract The effects of nitride (AlN, BN, TiN) addition on the electrical, thermal, and mechanical properties of porous SiC-nitride composites were investigated within a porosity range of 40–74%. The electrical conductivity was predominantly controlled by chemistry rather than porosity, whereas the thermal conductivity was more susceptible to changes in porosity. These results suggest that the electrical conductivity of porous SiC ceramics can be tuned independently from the thermal conductivity by nitride addition. At constant thermal conductivity (∼5 Wm-1  K-1), the electrical conductivity of the baseline specimen (6.3 × 10-3 Ω-1 cm-1) could be: (1) increased by an order of magnitude (8.3 × 10-2 Ω-1 cm-1) by adding AlN and (2) decreased by an order of magnitude (7.0 × 10-4 Ω-1 cm-1) by adding BN. Typical electrical conductivity and thermal conductivity values of the porous SiC-10 vol% TiN composite were 5.3 × 10-1 Ω-1 cm-1 and ∼14.0 Wm-1  K-1, respectively, at 51% porosity.