Abstract
The optimum dispersion and rheological properties of red clay-based ceramic suspension loaded with unary and binary starch were investigated in aqueous medium. The aqueous ceramic suspension was prepared consisting of red clay, quartz, feldspar, and distilled water. Using a polyelectrolyte dispersant (Darvan 821A), the ternary ceramic powder was initially optimized to give the smallest average particle size at 0.8 wt. (%) dispersant dosage as supported by sedimentation test. This resulted into an optimum high solid loading of 55 wt. (%). The addition of either unary or binary starches to the optimized ceramic slurry increased the viscosity but maintained an acceptable fluidity. The mechanism of such viscosity increase was found to be due to an adsorption of starch granules onto ceramic surfaces causing tolerable agglomeration. Correspondingly, the rheological evaluations showed that the flow behaviors of all starch-loaded ceramic slurries can be described using Herschel-Bulkley model. The parameters from this model indicated that all ceramic slurries loaded with starch are shear thinning that is required for direct casting process.
Highlights
The success in achieving the desired physical properties of different types of ceramic products relies on the critical application of the colloidal ceramic processing principle[1]
The rheological properties of red clay-based ceramic suspension loaded with different types of starches and their binary mixtures were investigated to produce high solid loading slurry suitable for direct casting
To obtain a well dispersed slurry, the particles in suspension are kept apart by a complete coverage of charged polymeric layer[9,19] introduced by the optimum concentration of adsorbed polyeletrolyte. This mechanism was systematically studied for ceramic slurry containing three different types of powders including red clay, quartz, and feldspar
Summary
The success in achieving the desired physical properties of different types of ceramic products relies on the critical application of the colloidal ceramic processing principle[1]. The net effect of these forces acting on particle surfaces determines the state of dispersion of the colloidal suspension wherein the repulsive forces is maximized to counteract the formation of attractive forces[3,4] that cause particle agglomeration This repulsive barrier can be achieved by electrostatic or steric stabilization mechanisms, which depends on the liquid medium and the composition of the powder. The colloidal processing is an important tool in achieving the stable suspension involving the dispersion of particles that influences the succeeding forming steps These fabrication steps include consolidation of dispersed particles by removing most of the aqueous medium, which is followed by further drying and burning out of organic additives. The present study deals with the optimization of dispersion characteristics of red clay-based powder mixtures loaded with starch in aqueous medium to produce a stable and high solid loading slurry. The rheological properties of red clay-based ceramic suspension loaded with different types of starches and their binary mixtures were investigated to produce high solid loading slurry suitable for direct casting
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