High-Entropy Alloy Nitride AlMo_0.5NbTa_0.5TiZrN_x-Based High-Temperature Solar Absorber Coating: Structure, Optical Properties, and Thermal Stability

Abstract

Advanced solar thermal technologies, including solar thermal collectors, solar thermophotovoltaic systems, and concentrated solar power systems, depend heavily on solar selective absorber coatings (SSACs) for photothermal conversion. Efforts for the research work of SSACs focus not only on optical properties but also on their high-temperature applications over a wide temperature range. Here, an SSAC based on an AlMo 0.5 NbTa 0.5 TiZrN x highentropy alloy nitride ceramic is first designed and fabricated on a stainless steel (SS) substrate via the magnetron sputtering method. The multilayer AlMo 0.5 NbTa 0.5 TiZrN x -based solar absorber coatings show good optical properties with a high absorptance value of 0.932 and a low infrared emittance value of 0.063. For the thermal stability of this coating, the as-fabricated coatings are subjected to the annealing process in vacuum at different temperatures. It is interesting that the spectral selectivity deteriorates to 0.798/0.067 at 673 K for 2 h but increases to 0.855/0.08 at 973 K for 2 h. In addition, finite difference time domain (FDTD) calculations are employed to determine the evolution of the optical absorption contributing to intrinsic absorption. The obvious attenuation of the electric field was caused by the change in the optical constants of the bimetallic ceramic layer, as evidenced by systematic analysis.

High‐Entropy Photothermal Materials

“…For instance, nonequimolar HE nitrides such as AlMo 0.5 NbTa 0.5 TiZrN x and Al 0.4 Hf 0.6 NbTaTiZrN have also been utilized in the preparation of spectrally selective absorbers. [142,143] However, their thermal robustness is inferior compared to the equimolar counterparts. A contributing factor to this reduced thermal stability might be the oxidation of elements like Zr and Ta.…”

BiFeO3 perovskite-based all oxide ambient stable spectrally selective absorber coatings for solar thermal application

“…1,9,10 The optical properties, corrosion resistance, temperature stability, repeatability and reproducibility are the key components that determine the superior performance of any SSAC. [11][12][13][14][15][16][17] The excellent performance of SSACs can be achieved by coating material with good absorptance properties and depositing an antireecting coating, which reduces the reectance from the top surface.…”

Enhanced Interband Transition in FeCoNiAlTi High‐Entropy Alloy for Ultrafast Nonlinear Optical Applications

“…[9][10][11] Up to date, the optical properties of HEAs are demonstrated for the solar energy harvest in a large bandwidth of the solar spectra. [11][12][13][14] In these systems, the optical absorption ability was only performed with the wide sunlight with a relatively low intensity. Thus far, the development of applications in nonlinear optics with HEAs is still of great challenge.…”