Formation mechanism and control of a large-scale lamellar structure in freeze-cast Al2O3 ceramics under dual temperature gradients

Abstract

We prepared a large-scale aligned structure in Al2O3 porous ceramics by a simple and novel bidirectional freeze-casting technique. This technique uses a side metal plate to achieve cold-surface cooling from the bottom to generate dual temperature gradients to control the nucleation and growth of ice crystals. By recording the slurry temperature in situ, we obtained various temperature gradients for the samples prepared by this technique using 3 mm thick copper, aluminium and stainless-steel plates as the cold surfaces. The architectures of the scaffolds produced under these freezing conditions were investigated to determine the effect of the temperature gradients on the morphology of the microstructure. Finally, a model was proposed to account for the temperature gradient regulatory mechanism of the transition from a dendritic structure to a parallel structure.