Effects of oil on gelcasting of oil-in-water Si3N4 suspensions

Porous Si 3 N 4 ceramics were fabricated through gelcasting followed by pressureless sinter at 1690 °C. Oil-in-water (O/W) Si 3 N 4 suspensions were prepared by mixing paraffin O/W emulsion and Si 3 N 4 suspensions, sodium alginate was used as gelling agent. The casted suspensions were quickly gelled by spraying calcium chloride aqueous solution onto the surface, thus oil was enwrapped into the green bodies. The porous Si 3 N 4 ceramics had spherical-shaped pores both with and without adding O/W emulsion. As changing the O/W emulsion content in the suspension, porous Si 3 N 4 ceramics with high open porosity of 60.1–63.9% and flexural strength of 44.5–34.6 MPa were obtained.