Processing of microcellular silicon carbide ceramics with a duplex pore structure

A novel processing route for producing microcellular SiC ceramics with a duplex pore structure has been developed using a polysiloxane, carbon black, SiC, Al2O3, Y2O3, and two kinds of pore former (expandable microspheres and PMMA spheres). The duplex pore structure consists of large pores derived from the expandable microspheres and small windows in the strut area that were replicated from the PMMA spheres. The presence of these small windows in the strut area improved the permeability of the porous ceramics. The gas permeability coefficients of porous SiC ceramics were 0.13 × 1012 m2 for the porous SiC without PMMA spheres, 0.47 × 1012 m2 for the porous SiC with 10 wt% PMMA spheres, and 0.82 × 1012 m2 for the porous SiC with 20 wt% PMMA.