Permeability and Nanoparticle Filtration Assessment of Cordierite-Bonded Porous SiC Ceramics

Cordierite bonded porous SiC ceramics having pore fractions (epsilon) between 0.33 and 0.72 and pore sizes of 6-50 mu m, flexural strength of 5-54 MPa, and elastic modulus of 6-42 GPa were prepared by oxide bonding at 1350 degrees C in air compacts of SiC, Al2O3 and MgO powders with petroleum coke (PC) as the sacrificial pore former. To test the applicability of the porous ceramics in the fluid flow field, air permeation behavior was studied with fluid superficial velocity from 0.083 to 0.90 m s(-1) and at 26-750 degrees C. The Darcian, k(1), and the non-Darcian, k(2), permeability coefficients were evaluated by fitting Forchheimer's equation to the experimental results. The temperature dependence of the permeability coefficients was explained from structural changes occurring during test conditions. The collection efficiency of filter ceramics (epsilon = 0.62-0.68) operating on removal of nanosized aerosol particles with sizes varying from 7 to 300 nm was determined by counting particles before and after filtration at a fluid superficial velocity of 0.1 m s(-1). Experimental results showed variation of collection efficiency from 96.7 to 99.9%. The size-selective fractional collection efficiency at different porosity levels was derived by using the well-known single-collector efficiency model considering some boundary conditions, and the model data were validated with experimental results. The test results were used for examination of the applicability of the filter ceramics in nanoparticle filtration processes.