Insights into Numerical Modeling Macro-Porosity in Ceramics

Porous ceramic materials are used for several applications, like filtration, catalysis, thermal insulation, gas adsorption, etc. Different structures can be purposely generated into the solid, regardless of the shape of pores, the size distribution, hierarchical organization, depending on the final use of the material. For instance, a catalyst should have high superficial area with open porosity easily accessible from the outside, thus superimposition of micro and macro porosities would result very effective. Wet based techniques such as direct and indirect foaming, e.g. freeze casting [1], allow to produce globular or lamellar unidirectional porosity whose amount, size and distribution are dependent on the process conditions [2, 3]. The presence of porosity affects the average properties of the material, because of the intrinsic heterogeneous morphology. For example, unidirectional porous ceramics have been shown to have higher permeability and higher mechanical properties compared to conventional globular porous ceramics. The computation of material properties can be pursued on the basis of a mathematical model, based on the constitutive equations of the material and the modeled morphology. The paper reports on some preliminary efforts into modeling the generation of porous ceramics based on a lattice simulation already adopted in other fields [4]. The model predicts the growth of the porosity along the time when a foaming agent is purposely added to the slurry. The simulated structures are used as input for computation of some average properties of the simulated device (e.g. gas permeability).