Repressing high-temperature radiative heat transfer in thermal barrier coatings

Photon diffusion in thermal barrier coatings (TBCs) significantly deteriorates the overall performance of gas turbines operating at high temperatures. This study presents the strategy of high-temperature photon suppression, based on a ceramic composite consisting of the second component with a smaller refractive index and controlled particle size. Using the Mie theory, it is theoretically demonstrated that controlling the second component particle size closer/equal to the infrared radiation wavelength region (1-5 mu m) could reduce photon diffusion. Ceramic composites comprised of 8 wt.% yttria-stabilized zirconia (8YSZ, matrix) and corundum (second component) with different particle sizes were prepared. The total and the photon thermal conductivity of the 8YSZ/corundum composites are lower than pure 8YSZ by similar to 48.9% and similar to 96.4% at 1200 degrees C, respectively. With the addition of corundum into 8YSZ, the thermal radiation transport of 8YSZ is significantly suppressed due to the photon scattering produced by the lower refractive index and proper particle size of the corundum. Besides, the fracture toughness and hardness of composites increased by similar to 20% and similar to 13%, respectively, compared to the 8YSZ. Composite with the corundum particles size of 1 mu m displays the lowest values of total and photon thermal conductivity at high temperature.