Fabrication of lamellar porous alumina with regular structure via directional solidification with multiple cold sources

Abstract

Porous ceramics obtained with aqueous slurries by directional solidification have randomly distributed lamellar pore channels and thus have unstable mechanical properties. According to the anisotropic principle of ice crystal growth, the growth of lamellar ice crystals is regular when multiple cold sources are used, and porous ceramics with regular pore channels are then obtained after drying. Multiple cold sources are formed with a bottom cold plate and copper sides in rectangular molds. The copper sides are in contact with the bottom cold plate, thus forming the side cold source with temperature gradient distribution by heat transfer. The interaction between the side cold source and the bottom cold plate facilitates the regular distribution and continuous growth in parallel of ice crystals. The use of parallel copper sides of the mold results in porous ceramics with an axisymmetric pore structure and high aspect ratios of pore channel in porous alumina. The positive compressive strength of fabricated porous ceramics with an axisymmetric structure is similar with those of conventional directional solidification, but the lateral side direction compressive strength of fabricated porous ceramics with an axisymmetric structure is significantly increased.