Enhanced insulation temperature and the reduced thermal conductivity of nanostructured ceramic coating systems

The theoretical model on the size-dependent thermal conductivity of the nanograins and the composites, based on the phonon confinement and the boundary scattering effects, was developed to predict the 68% reduced thermal conductivity of the nanostructured ceramic coatings made of grains of 40-100 nm compared with the conventional ceramic coatings with micron-scale grains. In order to validate the model, the nanostructured zirconia layers and the corresponding conventional layers were sprayed on the same alloy matrixes, and the insulation temperatures were measured at different temperatures up to 1273 K. It was found that insulation temperature of the nanostructured ceramic systems enhanced about 200 K at most compared with that of the conventional ones. And the average enhancement of the insulation effect is in agreement with the theoretical prediction. The nanostructured ceramic coated systems provide the extending application in thermal barrier engineering, thermoelectric devices and other related applications.