High temperature broadband reflectors
IntroductionThe heat radiation contribution to the total heat transfer in gas turbine becomes significant at high temperature. The issue is raised by the transparency of some ceramics used in the thermal barrier coating (TBC) in the infra-red (IR) region. Especially for the widely used TBC material: yittria-stabilized zirconia (YSZ), is fairly transparent in the wavelength region of 1-6mm, which corresponds to the region of maximum blackbody emission for operating temperature of present gas turbine engines [1]. Thus, the combination of high IR radiation and low absorption suggests that the radiation at high temperature may compete with the solid conduction for the heat transport across the coating. The recent progress in photonic crystals (PhCs) allows for the efficient controls of electromagnetic waves. PhCs are structures where the periodicity in dielectric prevents electromagnetic wave from propagation through the structure due to Bragg reflection. If the PhCs combine with the low thermal conductivity ceramic materials, the resulting high temperature photonic crystals could be attractive and promising for control of total heat transport at temperature > 1000°C. Thus the concept of 3D PhCs for high temperature heat radiation reflector is proposed. The application can also be extended to the spectral filter for thermo-photovoltaic (TPV). GoalsThe high temperature photonic crystal research in the institute for Optical and Electronic Materials is concentrated on designing a broadband IR radiation reflector that can operate in high temperature environment. The goal is to realize such a high temperature photonic structure with following properties:
References1. Shklover, V., Braginsky, L., Witz, G., Mishrikey, M. & Hafner, C. High-Temperature Photonic Structures. Thermal Barrier Coatings, Infrared Sources and Other Applications, J. Comput. Theor. Nanos. 5, 862–893, (2008). Publikationen
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