DISPERSION OF AQUEOUS Y2O3 NANO-SUSPENSION AND FABRICATION OF TRANSPARENT CERAMICS BY COLLOIDAL PROCESSING

Abstract

In the present study, transparent Y2O3 ceramics were successfully fabricated via colloidal processing, employing polyethylenimine (PEI) as an effective dispersant. The effect of PEI on nanosized Y2O3 suspensions was characterized by zeta-potential, adsorption behavior, rheological properties, and sedimentation test. The addition of PEI shifted the IEP of the Y2O3 powder towards a more alkaline pH range, and the adsorption of PEI on the Y2O3 surfaces gradually increased with the amount of PEI until reaching the saturation adsorption at 1.5 w/%. The PEI amount of 1.5 w/% was superior for the preparation of Y2O3 suspension as a result of a lower viscosity or sedimentation behavior. The viscosity of the suspension depended on the solids loading, increasing with the amount of powder. The optimal rheological behavior was achieved with 29 /% Y2O3 in the suspension, enabling the centrifugal slip casting of complex-shaped green bodies with a packing density of 43 %. Including an additional CIP treatment boosted the packing density of the green compacts, achieving above 50 %. Vacuum sintering the compacts at 1700 °C for 5 h yielded high-density ceramics exhibiting an in-line transmittance of approximately 73 % at a wavelength of 1100 nm.