Processing and Mechanical Properties of Macroporous Silicon Carbide Ceramics Fabricated by Carbothermal Reduction

Abstract

Porous silicon carbide ceramics were prepared from a carbon-filled polysiloxane by carbothermal reduction. The fabrication process involved three step: (i) the pyrolysis of polysiloxane at 1100^oC, which leads to the conversion of polysiloxane to silicon oxycarbide (SiOC); (ii) the carbothermal reduction of SiOC and C mixture at 1450^oC, which converts the mixture to a SiC ceramic; and (iii) liquid phase sintering of the SiC using Al₂O₃-Y₂O₃ as a sintering additive at various temperatures.
By controlling the template content and sintering temperature, it was possible to adjust the porosity in a range of 39% to 88%. The flexural and compressive strengths of porous SiC ceramics with ~40% porosity were ~100 MPa and ~290 MPa, respectively.