Processing, microstructures and mechanical properties of aqueous gelcasted and solid-state-sintered porous SiC ceramics

Porous solid-state-sintered SiC ceramics with controllable structures and excellent mechanical performances were prepared by aqueous gelcasting, combined with direct protein foaming technique. Dispersion of SiC and carbon black powders in water, the rheological behavior of steady SiC-B4C-C slurries, and solidification process of foamed suspensions were systematically investigated. Porosities as well as the microstructures of sintered bulks were tailored by varying the solid content of slurries and amount of foaming agent. The relationship between the compressive strength (41–151 MPa) and porosity (49–68%), and the fracture behaviors were discussed. For improving the connectivity, grain grading was adopted and its effects were revealed.