Preparation of a dense/porous biLayered ceramic by applying an electric field during freeze casting

Dense/porous bilayered ceramics were fabricated by introducing an electric field into the freeze-casting process. A unidirectional solidification was performed by placing an aqueous ceramic on refrigerating equipment, at a constant cooling rate of 6°C/min. When the bottom temperature of the slurry was reduced to 0°C, an electric field along the vertical direction was applied until the freezing process was completed. After drying and sintering of the green part, an as-prepared ceramic with dense/porous bilayered architectures was obtained. It was shown that the thickness of the dense layer in the sample could be controlled by tuning the electric field intensity from 51 to 155 μm as the electric field increased from 15 to 90 V. On the other hand, all samples exhibited almost an identical lamellae thickness and interlayer distance in the porous region, as large as ∼14 and ∼24 μm, respectively.