Optical Performance, Thermal Stability, and Failure Analysis of the WN_x-Si₃N₄ Multilayer Solar Selective Absorbing Coatings

Abstract

The development of high-temperature-tolerance solar selective absorbing coatings (SSACs) is beneficial to improve the conversion efficiency of concentrated solar power. In the present work, a TiN/Mo/WN x -Si 3 N 4 bilayer/SiO 2 cermet-based SSAC was developed, which was deposited on different substrates by magnetron sputtering. The designed WN x -Si 3 N 4 SSAC exhibits a high solar absorptivity of 0.952, accompanied by a relatively low emissivity of 0.059 at 25 °C and 0.134 deduced at 600 °C. Moreover, the WN x -Si 3 N 4 SSAC deposited on a stainless-steel (SS) substrate shows great thermal stability at 650 °C in vacuum. The solar absorptivity shows a slight decrease from 0.952 to 0.939 and the emissivity at 25 °C decreases from 0.059 to 0.045 after being annealed at 650 °C in vacuum. Furthermore, when being annealed at 700 °C in vacuum, the WN x -Si 3 N 4 SSAC deposited on the quartz glass substrate still keeps stable, but the coating on the SS substrate is dramatically destroyed. A comprehensive failure analysis was conducted utilizing FT-IR, SEM, Raman, and XPS characterizations. The degradation of the WN x -Si 3 N 4 SSAC deposited on the SS substrate at 700 °C is caused by the severe elemental diffusion between the absorbing layers and the antireflection layer. Moreover, the cracks induced by the thermal stress provide rapid channels for elemental diffusion.

Inorganic Multilayer Film with High Infrared Selective Emission Enhanced by SiNx for Daytime Radiative Cooling

“…The atmospheric transmittance under AM1.5 conditions is used as a relevant optical simulation parameter, , where the solar radiation spectrum is the normalized solar irradiance for AM1.5 according to ISO 9845-1:1992(E). The reflectivity and emissivity of the full-layer film can be derived from the reflectance spectrum, which can be given as R ( θ ) = ∫ 0.3 0.25em μ normalm 2.5 0.25em μ normalm R false( λ , θ false) I AM 1.5 false( λ false) d λ ∫ 0.3 0.25em μ normalm 2.5 0.25em μ normalm I AM 1.5 false( λ false) d λ ε ( θ ) = ∫ 8 0.25em μ normalm 13 0.25em μ normalm false( 1 − R ( λ ) false) I BB false( λ false) d λ ∫ 0.3 0.25em μ normalm 20 0.25em μ normalm I BB false( λ , T false) d λ where both reflectivity and emissivity are obtained by calculating the average of the TE (transverse electric) and TM (transverse magnetic) polarizations, − <...…”

“…The atmospheric transmittance under AM1.5 conditions is used as a relevant optical simulation parameter, , where the solar radiation spectrum is the normalized solar irradiance for AM1.5 according to ISO 9845-1:1992­(E). The reflectivity and emissivity of the full-layer film can be derived from the reflectance spectrum, which can be given as where both reflectivity and emissivity are obtained by calculating the average of the TE (transverse electric) and TM (transverse magnetic) polarizations, − for example, R = ( R TE + R TM )/2 and ε = (ε TE + ε TM )/2.…”

Thermal Stability and Weather Resistance of a Bionic Lotus Multiscale Micro–Nanostructure TiC/TiN–Ni/Mo Spectral Selective Absorber Based on Laser Cladding-Induced Melt Foaming

“…The technology of generating electricity for thermal energy shows great application prospects. , Selective absorption coating is the core material of solar collectors. The coating needs to have a high absorptivity (α) in the solar spectral range of 0.3–2.5 μm, a low thermal emissivity (ε) in the infrared region of 2.5–25 μm, and excellent optical stability and corrosion resistance at high temperatures. − The types of solar absorption coatings include intrinsic absorption coatings, optical interference coatings, dielectric-metal composite coatings, and optical trap coatings. − Recently, the optical interference coatings with multilayer cermet structures, such as Co-WC-Al 2 O 3 , TiC-Al 2 O 3 , WNi-Al 2 O 3 , and WTi-Al 2 O 3 , have become the research focus because of excellent optical properties. − However, the atomic diffusion between the layers of the traditional multilayer solar absorption coating destroys the multilayer structure at high temperatures, resulting in a significant reduction in the light interference absorption efficiency, making it less stable at high temperatures . In addition, due to the weather environment such as rain and snow, the corrosion resistance is crucial for the long-term application of the coating, which directly affects the service life of the coating …”

Synthesis and Characterization of Multilayered CrAlN/Al2O3 Tandem Coating Using HiPIMS for Solar Selective Applications at High Temperature

“…As a result, frequent maintenance and repair, typically every two years, are necessary to ensure its optimal performance. Hence, in recent years, there has been a significant research effort focused on creating novel SSCs that possess exceptional temperature stability in oxidizing atmospheres. − …”