  The formation of regular patterns is a common feature of many solidification
processes involving cast materials. We describe here how regular patterns can
be obtained in porous alumina by controlling the freezing of ceramic slurries
followed by subsequent ice sublimation and sintering, leading to multilayered
porous alumina structures with homogeneous and well-defined architecture. We
discuss the relationships between the experimental results, the physics of ice
and the interaction between inert particles and the solidification front during
directional freezing. The anisotropic interface kinetics of ice leads to
numerous specific morphologies features in the structure. The structures
obtained here could have numerous applications including ceramic filters,
biomaterials, and could be the basis for dense multilayered composites after
infiltration with a selected second phase.
