Calculation of the effective thermal conductivity of powders formed by spherical particles in a gaseous atmosphere

We describe a method for calculating the effective thermal conductivity of powders formed by spherical particles with a size exceeding 1$\mu$m in a gaseous atmosphere in wide ranges of temperatures and pressures. We take into account the structural factor of the powder medium, adsorption of gas on the surface of solid spheres, the temperature dependences of the thermal conductivities of the powder components, and the formation of melt necks between the spheres after the attainment of the melting point. In the case of complete melting of the spheres, we propose a model for thermal conductivity of the melt with gas inclusions. The results of calculation of the effective thermal conductivity are in good agreement with experimental data.