Processing highly porous SiC ceramics using poly(ether-co-octene) and hollow microsphere templates

Excerpt

Ceramic components with high porosity, high strength, and good permeability are especially required for hot-gas and molten metal filters, catalyst supports, preforms for making metal matrix composites, gas burner media, and light-weight structural parts [1‐8]. Silicon carbide (SiC) has been considered a candidate material for hot-gas filters due to its unique combination of such properties as high thermal conductivity, superior mechanical features, high thermal shock capacity, and corrosion resistance [9‐13]. Highly porous (porosity ≥ 80%) SiC ceramics are prepared using the following processing methods: (1) immersion of the polyurethane (PU) foams in a ceramic slurry, and drying, burning out the PU, and then sintering [1, 5, 14]; (2) freezing of gel containing SiC powders [4] or freezing the polycarbosilane/camphene solution [15]; (3) gel-casting of SiC powder mixtures using agar as the gelling agent [16]; and (4) pyrolysis of a cross-linked body consisting of a polycarbosilane precursor and polymer microbead templates [17], or pyrolysis and carbothermal reduction of a cross-linked body consisting of a polysiloxane precursor, polymer microbead templates, phenol resin, and optional sintering additives [18]. …