High-Temperature Thermal Energy Transport and Conversion using Photonic Nanostructures and Metamaterials

High-temperature thermal energy transport, conversion, and management is fundamentally important for a multitude of energy processes, such as thermochemical, solar-thermal, thermophotovoltaic, thermal energy storage, and industrial heating, etc. Heat transfer physics at high temperature is also markedly different from its counterpart at room- and low- temperatures, including stronger phonon-phonon scattering leading to lower phonon thermal conductivity and the more prominent or even dominant role of radiation heat transfer. On the other hand, high temperature poses tremendous challenges on materials, especially on their thermal and chemical stability. Here we present two recent examples from our studies on photonic thermal energy transport and conversion at high temperature. First, we experimentally probed the more prominent role of surface phonon polariton (SPhP) in polar dielectric (e.g., SiO₂) nanostructures and studied their contribution to thermal radiation and conduction from room to high temperature. We show that the geometry of the polar dielectric nanostructures can be manipulated to engineer the SPhP-mediated thermal radiation and conduction. In particular, we observe photon-like heat conduction contributed by SPhP in SiO₂ nanoribbons. Second, we developed high-temperature selective emitters based on metamaterials. While metamaterial emitters have been widely explored, they are often not stable at high temperature due to the presence of nanoscale interfaces. We use novel material and structural designs to attain high temperature stability. These selective emitters could be used to more efficiently converting optical and electrical energy into thermal energy within a desirable spectrum that are useful for systems such as thermophotovoltaic and infrared heating.