Processing and properties of porous SiC ceramics prepared by yttrium aluminum garnet infiltration

Oxide bonded porous SiC ceramics were synthesized by infiltrating a liquid precursor of yttrium aluminum garnet into porous powder compact of SiC followed by sintering at 1300‐1500°C in air. Infiltration rate was estimated using weight gain by the liquid precursor sol into porous SiC powder compact as a function of time and was explained by Darcy's and Ficks's laws. The effects of SiC particle sizes and sintering temperatures on the formation of bonding phases, microstructure, SiC oxidation degree, flexural strength, porosity, and pore size distribution of porous SiC ceramics were studied. Various crystalline oxide phases were detected by XRD analysis. Depending on the starting SiC powder sizes and sintering temperatures, the porosity of the final ceramics varied nearly in the range of ~29‐41 vol. % with the variation of average pore diameter between ~5 and 30 μm. Flexural strength varied from 41 to 8 MPa depending on porosity. The effect of corrosion on oxide bond phases was investigated in strong acidic and basic medium at 90°C. The ceramics showed better corrosion resistance in acidic medium compared to basic medium. In basic medium, significant reduction in flexural strength (~42%) was arisen.