Stabilization of Highly Concentrated Alumina Suspensions by Different Dispersants

Abstract

Slip casting is a widely used colloidal technique for consolidation of ceramic powders from a suspension. The colloidal approach ensures homogeneous microstructure of a green body, thereby reducing post-sintering machining and production costs. The process consists of several steps. The first step is to mix the ceramic powder with a liquid, usually water, where the stabilization of the new obtained suspension with different dispersants follows. When an optimum dispersion of particles is achieved, resulting in low slip viscosity, ceramic slurry can finally be poured into a porous mould, usually a gypsum one. The influence of different dispersants on rheological properties of highly concentrated alumina (Al 2 O 3) suspensions was investigated. The used dispersants were: ammonium polymethacrylate water solution (Darvan C-N), 4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt (Tiron) and citric acid. The amount of dispersants was varied from 0.1-1.25 wt. % in order to determine the optimum. Rheological properties of the prepared suspensions were determined by measuring the apparent viscosity at different shear rates. The obtained optimal amount was 0.75 wt. % for Darvan, 0.1 wt. % for Tiron and 0.3 wt. % for citric acid. The obtained results show that the most effective dispersant is 4,5-dihydroxy-1,3benzenedisulfonic acid disodium salt, given that only 0.1 wt. % was required to stabilize the 70 wt. % Al 2 O 3 suspension.

Hardness and Indentation Fracture Toughness of Slip Cast Alumina and Alumina-Zirconia Ceramics

“…The influence of additives (different dispersants) on the ceramic suspension stability has been extensively researched [13][14][15][16][17][18][19]. Some of the dispersants which have been used as stabilizing agents for preparation of stable aqueous alumina suspension include ammonium polymethacrylate ("Darvan C") [19][20][21], 4,5dihydroxy-1,3-benzenedisulfonic acid disodium salt ("Tiron") [21][22][23], triammonium salt of aurintricarboxylic acid ("Aluminon") [21], (Darvan C-N) [23], sodium pyrophosphate, diammonium hydrogen citrate [24], citric acid [23], ammonium polyacrylate ("Seruna D-305") [25], carbonic acid salt ("Dolapix CE 64") [20,26,27], polycarbonic acid salt ("Dolapix PC 33") and carbonic acid ester ("Dolapix ET 85") [27].…”

A Review of Microwave-Assisted Sintering Technique

“…To achieve the above mentioned properties, it is necessary to produce green bodies with adequate homogeneity. One of the most common techniques for the consolidation of ceramic powder is slip casting, where an aqueous ceramic suspension is poured into a porous mould which withdraws water from the suspension, thus producing a green body ready for sintering [6]. If proper procedures of powder preparation and consolidation are adopted, successful fabrication remains dependent on the sintering process variables.…”

Methods Used for the Compaction and Molding of Ceramic Matrix Composites Reinforced with Carbon Nanotubes

“…The casting from aqueous slips is widely used for manufacturing thin-walled hollow and solid green bodies from either construction or technical ceramics [124][125][126][127][128][129][130][131]. For making solid green bodies, Processes 2020, 8, 1004 20 of 37 additional doses of the slip are added to the mold several times.…”