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

• Published in: Materials chemistry and physics Vol. 258; p. 123957
• Main Authors: Arastoo, E., Movahedi, B., Yousefian, Z., Milani, M.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15-01-2021; Elsevier BV
• Subjects: Alumina; Aluminum oxide; Casting; Dispersants; Loose powder sintering; Nanocomposites; Optical properties; Sintering; Slip casting; Wet milling; Slip casting; Nanocomposites; Sintering; Optical properties
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2020.123957

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.
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•Amorphous phase as a shell led to the sintering-aid action, which is reducing the sintering temperature.•Slip-casting and pressureless sintering result in obtaining high green and final density.•A pore free structure which is transparent in IR wavelength range.•Alumina/amorphous alumina nanocomposite powder fabricating transparent ceramics.