Effects of the size distribution of SiC powders on the microstructures and properties of liquid phase bonded porous SiC with neck bonding phases of Y₄Al₂O₉, Y₃A₅O₁₂, Y₂Si₂O₇, and Al₂O₃

Abstract

Liquid phase bonded (LPB) porous SiC with neck bonding phases consisting of yttrium aluminate (Y₄Al₂O₉, Y₃Al₅O₁₂), yttrium silicate (Y₂Si₂O₇), and Al₂O₃ were fabricated using varying amounts of an Al₂O₃–Y₂O₃–SiO₂ bonding additive in Ar at 1500 °C for 1 h. LPB porous SiC ceramics exhibited unimodal pore-size distributions, porosities of 36.6–44.8 %, and pore sizes of 7.7–8.5 µm. The particle-size distribution of SiC powders was an important factor in determining the pore characteristics, including pore-size distribution, pore shape, porosity, and pore size, and the flexural strength as well as the gas permeability of LPB porous SiC ceramics. The porosity and pore size increased, and the pore-size distribution narrowed by using SiC powders with a narrow size distribution. The flexural strength of porous SiC varied in the range of 39.7–66.7 MPa and was mainly dependent on the porosity, pore shape, pore size, and solid boning area varied by the SiC particle-size distribution. A relatively high permeability (1.28–1.84 × 10⁻¹² m²) of LPB porous SiC was attained mainly due to the unimodal pore size distribution of pores with sizes of 7.7–8.5 µm.