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

高多孔陶瓷是通过冰通过胶体的定向凝固来加工的。在冷冻干燥过程中，冰升华，在陶瓷中留下单向孔道。初步的研究表明，孔隙形态可以用共晶组织的准规则定向凝固来理解。为了直接观察移动凝固界面的形貌以及界面速度与冰晶间距的关系，进行了定量的原位实验。这将使我们能够检验共晶凝固理论对胶体的适用性，并探索可加工的孔结构范围。同时，一个“断电”固化装置正在建造中，以控制在冷冻过程中较大体积样品的温度梯度。这将使孔结构和加工变量（如温度梯度、胶体中固体的体积分数和烧结温度）之间的定量关系得以确定。这项工作将导致一种新型的高孔隙率陶瓷，适用于一系列应用，如用于环境保护的陶瓷过滤器和用于组织工程和器官再生的陶瓷生物反应器。研究生和本科生将学习陶瓷加工的材料科学，并培养对这些高多孔陶瓷应用要求的欣赏。

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.