Aqueous gelcasting of ceria ceramics using water-soluble epoxide
Résumé
Gelcasting is a novel shaping process based on in-situ polymerization of ceramic suspension for forming a green body. This paper deals with the polymerization of ethylene glycol diglycidyl ether (EGDGE, epoxide) and diprolenetriamine (DPTA) for gelcasting of ceria (CeO2) ceramics. The formulation of aqueous suspensions was first investigated to determine the influence of EGDGE and DPTA addition on particles dispersion mechanisms. From rheological and zeta potential measurements, it appears that the optimum of dispersant content was not modified and that strong negative electrical charge is maintained at particles surface with the presence of dispersant and gelling agent. Then, polymerization reaction kinetics was studied. Under the various studied conditions, this kinetics strictly obeys to Arrhenius law and calculated activation energy appears to be in the range 48-68 kJ.mol-1 depending on solid-loading of suspensions. The more concentrated is the suspension, the lower is the activation energy. These results confirm that CeO2 powder can act as catalyzer. Finally, it was demonstrated the feasibility to manufacture dense ceria ceramics with complex shape. This non-toxic gelling system has thus great potential use for the fabrication of complexly shaped dense CeO2 ceramics with highly homogeneous microstructure.