Abstract
The gelcasting method is usually employed to fabricate relatively dense ceramics. In this work, however, porous Al2O3 ceramics with submicron-sized pores were fabricated using the water-based gelcasting method by keeping the Al2O3 content at low levels. By controlling the water content in the ceramic slurries and the sintering temperature of the green samples, the volume fractions and the size characteristics of the pores in the porous Al2O3 can be readily obtained. For the porous Al2O3 ceramics prepared with 30 vol.% Al2O3 content in the slurries, their open porosities were from 38.3% to 47.2%, while their median pore sizes varied from 299.8 nm to 371.9 nm. When there was more Al2O3 content in the slurries (40 vol.% Al2O3), the porous Al2O3 ceramics had open porosities from 37.0% to 46.5%, and median pore sizes from 355.4 nm to 363.1 nm. It was found that a higher sintering temperature and Al2O3 content in the slurries increased the mechanical strength of the porous Al2O3 ceramics.
Highlights
Porous materials are being developed and employed in different fields [1,2,3,4,5,6,7,8,9,10,11,12,13,14]
Ice crystals usually grow into dendrites, which make the pore surfaces rough, and the porous ceramics often exhibit anisotropic properties
For the porous Al2O3 ceramics prepared with Al2O3 content at 30 vol.% in the slurries, their flexural
Summary
Porous materials (including ceramic, metallic and polymeric types) are being developed and employed in different fields [1,2,3,4,5,6,7,8,9,10,11,12,13,14]. During the freeze-drying process, these ice crystals are directly vaporized by vacuum sublimation and leave pores inside the ceramic green body. One of the advantages of the gelcasting method is that ceramics with complicated shapes can be readily fabricated [28,29] In this method, high solid content in the ceramic slurries, or low water content, is usually needed to obtain. The purpose of this work, is to prepare porous of freezing the water in the ceramic slurries into ice crystals, as in the freeze casting method [16], it is ceramics, rather than dense ceramics. Into ice crystals, in thethat freeze casting of porous ceramics submicron pores gelcasting has in scarcely been reported method [16], itwith is evaporated during theusing dryingthe stage, and poresmethod are retained the green body.
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