engleski

Stabilization of high concentrated alumina suspensions by different dispersants

Slip casting is a widely used colloidal technique for the consolidation of ceramic powders from a suspension. The colloidal approach ensures homogeneous green body microstructure, therefore reducing post- sintering machining and production costs. The process itself consists of several steps. Firstly, dispersion of powder with controlled characteristics in a liquid, which is usually water, followed by stabilization of the new obtained suspension using different dispersants. When an optimum dispersion of particles is achieved and thus low slip viscosity, ceramic slurry can be poured in a porous mold, usually a gypsum one. The influence of different dispersants on rheological properties of highly concentrated alumina (Al2O3) suspensions was investigated. Used dispersants were Darvan C-N (an ammonium polymethacrylate water solution), 4, 5-dihydroxy-1, 3- benzenedisulfonic acid disodium salt and citric acid. The amount of dispersants was varied from 0.1-1.25 wt.% in order to determine the optimal one. Rheological properties of prepared suspensions were determined by measuring the apparent viscosity at different shear rates. The optimum amount for Darvan was 0.75 wt.%, 0.1 wt.% for 4, 5- dihydroxy-1, 3-benzenedisulfonic acid disodium salt, and 0.3 wt.% for citric acid. The obtained results show that the most effective dispersant is 4, 5-dihydroxy-1, 3- benzenedisulfonic acid disodium salt given that only 0.1 wt.% was needed to stabilize the 70 wt.% Al2O3 suspension.

Slip casting ; alumina ceramics

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