Effects of the particle size composition of sintering additives on pore characteristics, flexural strength, and gas permeability of liquid-phase-bonded macroporous sic

Macroporous SiC with unimodal pore-size distribution was fabricated using a liquid-phase bonding method with Al₂O₃– Y₂O₃–SiO₂ sintering additives at 1500 °C in Ar at for 1 h. The effects of the sintering additive particle size and content on the flexural strength, apparent porosity, gas permeability, and pore characteristics, such as average pore size and pore structure, were investigated. The pore size and porosity of the TA-SC specimens fabricated using relatively large sintering additive particles increased simultaneously, thus changing their pore structure. The pore structure of SA-SC mainly consisted of stacked cubic solid spheres, while the pore structure of TA-SC consisted of spherical pores with cubic stacking. The TA-SC specimens with higher porosity and larger pores exhibited higher flexural strengths than the SA-SC specimens. This can mainly be attributed to the difference in the pore structures of the SA-SC and TA-SC specimens, which directly affected the solid bonding area. The gas permeability of the SA-SC and TA-SC specimens varied from 2.5 × 10^–12 to 4.1 × 10^–12 m² depending on their porosity and pore size. The effect of the apparent porosity was more significant on the gas permeability than that on the average pore size, particularly for the porous SiC with the porosity of 33.5–39.7 vol% and the average pore size of 13.4–18.5 µm.