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Thermal barrier coating and new materials

Abstract:

Thermal barrier coating limits heat transfer and protect again oxidation and corrosion in chemically aggressive environment at high temperature. Nowadays, thermal barrier coating are made of three layers. The first layer is the layer with the lowest thermal conductivity. The second layer protects the substrate again oxidation and corrosion at high temperature. The last layer provides adherence. The main idea is to replace the Yttria-stabilized zirconia layer, often used, by a layer of a new material. Three lines of research have been identified: 1) Development of material with a thermal conductivity (k) lower than the thermal conductivity shown by Yttria-stabilized zirconia (k ∼ 1 W/mK), 2) The development of nanostructured materials with disordered structure and of individual nanocapas a few nanometers thick that reduce the thermal conductivity and 3) The study of the thermal conductivity at temperatures near the melting temperature in amorphous materials. At the former case, the focus is on the effect of rare earth atoms that can introduce a significant anharmonic effect. In this way, zirconates of rare earth such us Gd2Zr2O7 and Sm2Zr2O 7 have lead to interesting results. In the second case At, if the grain size is very small, the behavior of the thermal conductivity is similar to that of amorphous materials and nano layers of W and Al2O 3 with high density at the interface. In the third and the last case, the different physical processes that occur in the amorphous material may be relevant in understanding the minimum value of thermal conductivity of solid crystalline dielectrics recorded at very high temperatures. This observation suggests the possibility of using amorphous materials in the development of Thermal barrier coating.