The confinement of phonon propagation in TiAlN/Ag multilayer coatings with anomalously low heat conductivity

TiAlN/Ag multilayer coatings with a different number of bilayers and thicknesses of individual layers were fabricated by DC magnetron co-sputtering. Thermal conductivity was measured in dependence of Ag layer thickness. It was found anomalous low thermal conductivity of silver comparing to TiAlN and Ag bulk standards and TiAlN/TiN multilayers. The physical nature of such thermal barrier properties of the multilayer coatings was explained on the basis of reflection electron energy loss spectroscopy. The analysis shows that nanostructuring of the coating decreases the density of states and velocity of acoustic phonons propagation. At the same time, multiphonon channels of heat propagation degenerate. These results demonstrate that metal-dielectric interfaces in TiAlN/Ag coatings are insurmountable obstacles for acoustic phonons propagation

Structure and Behavior of Gasless Combustion Waves in Powders

<p>The method of simulation of the structure of powder mixture, which allows calculating the samples with a relative density from 15% up to practically close packing, is described. The 3D model of discrete combustion wave in powder mixture, which uses the actual structure of the sample, is considered. The parametric investigations of combustion of powder mixture in the wide range of relative density and particle ignition temperature are carried out. The model predicts the steady-state combustion, oscillating combustion, and extinction depending on the parameters of powder mixture. The results of the simulation are compared with experimental data.</p