Processing, microstructure and mechanical properties of porous silicon nitride by a slip casting method using petroleum coke as pore former

In this study, porous Si3N4 ceramics were obtained by a slip casting method which would be easier applied in industry. The most stable and dispersing aqueous suspension was obtained from a solid slurry content of 56.2%, a carboxymethyl cellulose concentration of 0.3% as the adhesive and 0.05% glycerol as the defoamer. Petroleum coke was used as pore-former, and at the same time, it was helpful for the stability of the suspension. The burning-out of the petroleum coke seemed to be an economical way for increasing the porosity of porous Si3N4. After sintering at 1,800 degrees C for 2 h, samples with a pore size about 10 mu m, porosities of 45-60%, and flexural strength of 52.0-112.1 MPa were obtained.