The Processing of Highly Porous Ceramics by Analogy with Quasi-Regular Eutectic Structures

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Highly porous ceramics are being processed by the directional solidification of ice through colloids. On freeze drying the ice sublimes leaving unidirectional pore channels in the ceramics. Preliminary studies have lead to the hypothesis that the pore morphologies can be understood using an analogy with quasi-regular directional solidification of eutectic microstructures. Quantitative in situ experiments are being conducted to directly observe the morphology of the moving solidification interface and the relationship between the interfacial velocity and the spacing of the ice crystals. This will allow us to examine the applicability of eutectic solidification theory to colloids and explore the range of pore structures that could be processed. At the same time a "power-down" solidification apparatus is being built to control the temperature gradient across larger bulk samples during freezing. This will enable quantitative relationships to be determined between the pore structure and processing variables such as temperature gradient, the volume fraction of solids in the colloid and the sintering temperature.The work should result in a new class of high porosity ceramics suitable for a range of applications such as ceramic filters for environmental protection and ceramic bioreactors for tissue engineering and organ regeneration. Graduate and undergraduate students will learn the materials science of ceramics processing and develop an appreciation of the requirements for these applications of highly porous ceramics.