Corrosion behaviors of porous reaction-bonded silicon carbide ceramics incorporated with CaO

Reaction-bonded SiC (RBSC) porous ceramics were fabricated at 1450 °C in air by incorporating CaO using ZrO2 as sintering aids, activated carbon as pore-forming agent, and mullite fibers as reinforcing agent. The effects of CaO content on the properties of the porous RBSC ceramics were studied. Corrosion behaviors of the prepared RBSC porous ceramics in different environments were also investigated. The optimal open porosity, bending strength, average pore size and gas permeability of the ceramics with 0.5% CaO were 40%, 22.5 MPa, 42.9 µm, and 2100 m3/m2 h kPa, respectively. A well-developed neck reaction-bonded by calcium zirconium silicate (Ca3ZrSi2O9) was identified. The porous RBSC ceramics exhibited excellent corrosion resistance in acid and basic solutions. The anti-oxidation temperature of the porous RBSC ceramics could reach 1200 °C in air. The RBSC ceramics maintained the bending strength of 17.5 MPa after 60 cold-hot cycles in air (0-800 °C). The porous RBSC ceramics also exhibited relatively good corrosion resistance in molten salts (NaCl, Na2SO4 and CaCl2). Melten NaOH can aggravate the reaction by breaking the SiO2 layers on the SiC surface. Overall, these findings offer significant insights into expanding the applications porous RBSC ceramics incorporated with CaO.