Abstract

A phenomenological model is proposed to show the dependence of the heat conductivity of a porous coating on the pore size using experimental data on ZrO₂ + 7% Y₂O₃ coatings. To obtain plasma-sprayed coatings with different structures, powders with different properties are used. The concept of critical pores size at a given porosity is proposed. This concept corresponds to the maximum pore size at which the heat conductivity depends not only on the total porosity but also on the pore size, which is especially important for materials with submicron and nanosized structural components. Since the free path of phonons dispersed on pores depends on the distance between them, the concept of critical distance between pores is proposed. This concept corresponds to the maximum distance over which the heat conductivity depends only on the integral porosity.