Effect of Ni content and its particle size on electrical resistivity and flexural strength of porous SiC ceramic sintered at low-temperature using clay additive

A low-temperature sintered porous SiC-based clay-Ni system with controlled electrical resistivity (2.54 x 1010 omega cm to 2 omega cm), and thermal conductivity (3.5 W/m. K to 12.6 W/m. K) was successfully designed. Clay (20 wt% kaolin) was used as a sintering additive in all the compositions. The electrical resistivity, and thermal conductivity was controlled by varying the Ni content (0-25 wt%) in the samples. The electrical resistivity was recorded as low as 2 omega cm with 25 wt% Ni that was sintered at 1400 degrees C in argon. The interface reaction between Ni and SiC formed conductive nickel silicide (Ni2Si), while the transformation of kaolin to mullite strengthened the mechanical properties. Submicron-sized Ni (0.3 mu m) was more effective than micron-sized Ni (3.5 mu m) in reducing the electrical resistivity, and increasing the thermal conductivity along with flexural strength. A comparative study of sintering temperatures showed that 1400 degrees C resulted in the lowest electrical resistivity (2 omega cm) and the highest thermal conductivity of 12.6 W/m. K with flexural strength of 54 MPa at 32% porosity in the SiC-kaolin-Ni system.