A novel transparent ceramics from a slip-cast and vacuum sintered alumina/amorphous alumina nanocomposite powder

Abstract

This study aimed to obtain high-density green pieces from α-alumina/amorphous alumina core-shell nanocomposite powder. This nanocomposite was initially obtained in the form of a pellet with high-green density using the slip-casting process. Then, it was sintered by a pressureless sintering method under vacuum conditions. The effects of slurry parameters, such as dispersant content, solid loading, and agglomeration for viscosity and green density, are investigated for optimizing the slip-casting conditions. The green sample with a density of 63% was obtained by using α-alumina/amorphous alumina core-shell nanocomposite powder after 13 h of wet milling and casting at 70% solid loading, 5 wt% Dolapix, and pH = 10.5. The sintered sample showed a relative density of 99.5% and a transmission of 72% in the IR region at 1300 °C under a vacuum condition. The application of the amorphous phase in the initial powder, as a shell, led to the sintering-aid of this phase and decreased sintering temperature. The slip-casting method also resulted in high-green density and consequently high-final density using pressureless sintering. © 2020 Elsevier B.V.