Effects of eluted metal ions on the properties of ceramic slurry and slip-casted green bodies

Abstract

The characteristics of ceramics produced by wet forming are determined by the particle dispersion in the utilized slurry, obtained by mixing ceramic powder and a solvent. Evaluation and control of the particle dispersion is thus important. In the case of ceramic powder containing a sintering aid, metal ions may be eluted from the particles during preparation of the aqueous slurry. It remains unclear, however, how the metal ions affect the particle dispersion and the green body characteristics. Hence, in the present study, Mg2+ or Al3+ ions were added to common water-based alumina slurries, and their effects on the slurry and green body characteristics were investigated. It was found that the presence of about 10 mM of metal ions caused agglomeration of the slurry particles and decreased the green body packing fraction. The effects were particularly significant for small amounts of the added dispersant. When the dispersant dosage exceeded a certain level, the added metal ions produced no observable change in the slurry or green body characteristics. In addition, higher-valence metal ions were found to decrease the maximum green body packing fraction and increase the dispersant dosage required to reach the maximum packing fraction.

Keywords

• slurry
• slip casting
• metal ions
• particle dispersion state
• ceramic