Processing of porous silicon carbide ceramics from carbon-filled polysiloxane by extrusion and carbothermal reduction

Porous silicon carbide (SiC) ceramics with porosities ranging from 60% to 83% were fabricated from extruded blends of carbon-filled polysiloxane using expandable microspheres as sacrificial templates. The fabrication process involved the following steps: (i) extrusion and in situ foaming of a mixture of polysiloxane, carbon black (used as a carbon source), Al2O3-Y2O3 (used as a sintering additive), expandable microspheres (used as sacrificial templates), and SiC (an optional inert filler); (ii) cross linking the polysiloxane in the extruded blends; (iii) transforming the polysiloxane by pyrolysis into silicon oxycarbide; and (iv) fabricating porous SiC ceramics by carbothermal reduction and subsequent sintering.