1997 Volume 105 Issue 1217 Pages 73-78
Stable emulsions of ethyl silicate (ES) were prepared for the use of binders in refractory processing. The rheological characteristics and hardening mechanisms of alumina slurries produced by the use of a new binder system consisting of ES emulsions and water glass were investigated together with the properties of the ES emulsions. The highly dispersed alumina slurries were obtained by the modification of alumina surface to be negatively charged prior to mixing the alumina particles with the binder system in which ES droplets are charged negatively. The alumina slurries having the rheological behavior of rheopexy were found to be advantageous in fluidity and durability for the casting process. Moreover, the slurries cast in a metallic mold were hardened spontaneously by heating up to a certain temperature at which ES emulsions break down, because the gelification proceeds according to the alkali-catalized hydrolysis of ES. Both the resulting green bodies and alumina cores fired at 1000°C proved to have a strength satisfactory in handling and casting, respectively.
