Studies on processing of layered oxide-bonded porous sic ceramic filter materials

摘要

Oxide-bonded porous SiC ceramic filter supports were prepared using SiC powder (d(50) = 212 mu m), Al2O3, and clay as bond forming additives and graphite as pore former following reaction bonding of powder compacts at 1400 degrees C in air. Reaction bonding characteristics, phase composition, porosity, pore size, mechanical strength, and microstructure of porous SiC ceramic supports were investigated. Mullite bond phase formation kinetics was studied following the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model using non-isothermal differential thermal analysis (DTA) data. Compared to porous SiC ceramic filter supports having no needle-like mullite bond phase, materials processed by the mullite bonding technique exhibited higher average strength (22.1%) and elastic modulus (5.4%) at a similar porosity level of similar to 38%, with upper and lower bounds of their strength, modulus, and porosity being 39.1 MPa, 40.2 GPa, and 36.3% and 34.2 MPa, 31.3 GPa, and 33.0%, respectively. Spray coating method was applied for preparation of oxidation-bonded SiC filtration layer having thickness of similar to 150 mu m and pore size of similar to 5-20 mu m over the porous SiC support compacts using aqueous slurry made of fine SiC powder (d(50) = 15 mu m) followed by sintering. The layered ceramics thus prepared are potential materials for gas filter applications.