Formation of silicon nitride bonded silicon carbide by aqueous gelcasting

Gelcasting is a very useful technique for producing ceramic green parts with complex shapes. Although it has been successfully applied to ceramic systems consisting of submicron size powders, there is little report on gelcasting of ceramics containing coarse particles. In this work, we report the study on gelcasting of silicon nitride bonded silicon carbide (SNBSC) refractory. It was found that density of SNBSC made by gelcasting is strongly dependent on the solids loading and the organic binder content in slurry. A high solids loading in the slurry is desirable for achieving high density of the materials after sintering. Less amount of monomer is required for gelcasting of this material compared to ultra-fine ceramic powders. Moreover, excessive amounts of monomer could lead to low density after polymer burnout or sintering and low strength for the final products after sintering.