Aqueous Gelcasting of Fused Silica Using Colloidal Silica Binder

An aqueous-based gelcasting of fused silica ceramics by using colloidal silica binder was developed. Fused silica slurries having different volume percentage of solid loading from 63 to 74vol% in colloidal silica were made and the rheological properties were evaluated. It was found that the slurry with 73vol% of solid loading with viscosity 0.70Pa.s is suitable for this gelcasting system. The influence of solid loading on physical and mechanical properties of gelcast green and sintered bodies has been studied. The fabricated green body by using colloidal silica binder exhibited a flexural strength of 9MPa and 88% of theoretical density with 2.2% of drying shrinkage while the sintered sample exhibited flexural strength of 60MPa and 95% of theoretical density with 4.3% of sintering shrinkage. It was observed that, the nano silica particles from the colloidal silica binder is filling the interstitial positions in the consolidated fused silica green body and enhancing physical and mechanical properties.