New methods of ceramic processing based on colloidal processing are becoming increasingly important for advanced ceramic materials and in particular for complex shape components. Gel casting and Direct Coagulation Casting (DCC) represent the latest improvements in this area. These methods consist in consolidating a suspension with a high solid loading (>50% vol) in a non porous mould in order to obtain a green body with a very low shrinkage. The difference between the two techniques concerns the destabilisation mode. Our research team has chosen to develop the DCC process because it uses water as a solvent and the low content of organic additives in the suspension does not require a debinding stage. The main disadvantage is the low strength of green parts. A high state of oxides particle dispersion, in a pH range where no solubility of the particles occurs, was achieved by using an anionic electrolyte, Tiron, 4,5(HO)2C6H21,3(SO3Na)2. Its strong adsorption around the ZPC of the powder via the alcohol group creates a high repulsive potential between the particles via the SO3 - groups. As this anion complexes efficiently a lot of ions in water, it shows a high affinity for the surface of the linked oxides, for example, Al2O3, TiO2 and ZrO2. The coagulation of oxide/Tiron systems can be effective with the addition into the suspension of an aluminum salt, the Hydroxyaluminum diacetate, (CH3CO2)2AlOH, whose decomposition in water can be controlled with the temperature value. The releasing of aluminum ions induces the pH decrease, the increase of the ionic strength and the dispersant desorption which are beneficial to destabilize the suspension.

Keywords: dispersion, formulation, coagulation, suspensions, oxides