Effects of CaCO3 and ZrO2 on microstructure and properties of silicon-bonded SiC porous ceramics

Abstract

The present study aims to determine the effects of calcium carbonate (CaCO3) and zirconium dioxide (ZrO2) on the microstructure and properties of silicon-bonded silicon carbide (SBSC) porous ceramics. The SBSC porous ceramics were prepared by adding CaCO3 and ZrO2 as composite additives in an argon atmosphere. Then, the impact of CaCO3 and ZrO2 on the properties and microstructure of SBSC porous ceramics was investigated. The results revealed that a proper amount of CaCO3 and ZrO2 can be effective for improving porous structures and increasing bending strength. Calcium zirconium silicate (Ca3ZrSi2O9) was identified to have a well-grown neck connection phase, which is the result of the reaction of CaO, ZrO2 and impurity SiO2. Simultaneously, the disappearance of the impurities of silicon dioxide (SiO2) facilitated the combination of fused silicon (Si) and silicon carbide (SiC) grains, thereby creating pores in the original location of the Si and optimizing the micropore structure. In conclusion, SBSC materials with 6 wt% ZrO2 and 4 wt% CaCO3 sintered at 1450 °C have the best apparent porosity (38.86%), bending strength (68.7 MPa), mean pore size (7.45 μm), and gas permeability (98.5 m3/m2·h1·kPa1).