Modelling of thermal conductivity of porous materials: application to thick thermal barrier coatings

Modelling of thermal conductivity of two and three phase composite materials is used to determine the thermal conductivity of thick porous zirconia based thermal barrier coatings for use in high temperature applications. These coatings, depending on the deposition technique and process parameters exhibit different degrees of porosity. The porosity of the coating has an affect on thermal properties in completely different ways depending on the morphology and the orientation of the pores dispersed within a continuous matrix. In this work air plasma sprayed coatings have been considered. The experimental results were successfully compared to the modelled thermal conductivities. In the model the effects of porosity were taken into account considering the shape, orientation and volumetric percentage of pores. Image analysis and mercury porosimetry was used in experimental porosity determination.