Influence of Short-Chain Carboxylic Acids on the Mechanical Properties and Structure of Coagulated Alumina Suspensions

Three different short-chained carboxylic acids, formic, acetic, and propionic acid, were compared as additives to increase the green strength of wet particle networks produced with the direct coagulation casting process, which allows the internal coagulation of a suspension. Small acid additions do not alter the favorable low viscosity of the stabilized slurry, and yet increase the compressive strength of wet coagulated bodies. The strengthening effect increases with increasing chain length of the carboxylic acid. The maximum effect was observed upon addition of propionic acid (0.3 wt% to alumina), which resulted in a sixfold increase in compressive strength of wet coagulated bodies compared with that without propionic acid.