PREPARATION OF STABLE ETHYL SILICATE EMUL SIONS AND APPLICATION TO A REFRACTORY BINDER

Stable emulsions of ethyl silicate (ES) were prepared for the use of b inders in refractory processing. The rheological characteristics and h ardening mechanisms of alumina slurries produced by the use of a new b inder system consisting of ES emulsions and water glass were investiga ted together with the properties of the ES emulsions, The highly dispe rsed alumina slurries were obtained by the modification of alumina sur face to be negatively charged prior to mixing the alumina particles wi th the binder system in which ES droplets are charged negatively, The alumina slurries having the rheological behavior of rheopexy were foun d to be advantageous in fluidity and durability for the casting proces s. Moreover, the slurries east in a metallic mold were hardened sponta neously by heating up to a certain temperature at which ES emulsions b reak down, because the gelification proceeds according to the alkali-c atalized hydrolysis of ES, Both the resulting green bodies and alumina cores fired at 1000 degrees C proved to have a strength satisfactory in handling and casting, respectively..