Modulation of the cutoff wavelength in the spectra for solar selective absorbing coating based on high-entropy films

This paper demonstrates an intrinsic modulation of the cutoff wavelength in the spectra for solar selective absorbing coating based on high-entropy films.The(NiCuCrFeSi)N((NCCFS)N)films were deposited by a magnetron sputtering system.Rutherford backscattering spectroscopy analysis confirms the uniform composition and good homogeneity of these high-entropy films.The real and imaginary parts of the permittivity for the(NCCFS)N material are calculated on the basis of the reflectance spectral fitting results.A redshift cutoff wavelength of the reflectance spectrum with increasing nitrogen gas flow rate exists because of the different levels of dispersion when changing nitrogen content.To realize significant solar absorption,the film surface was reconstituted to match its impedance with air by designing a pyramid nanostructure metasurface.Compared with the absorptance of the as-deposited films,the designed metasurface obtains a significant improvement in solar absorption with the absorptance increasing from 0.74 to 0.99.The metasurfaces also show low mid-infrared emissions with thermal emittance that can be as low as 0.06.These results demonstrate a new idea in the design of solar selective absorbing surface with controllable absorptance and low infrared emission for high-efficiency photo-thermal conversion.

Improvement of thermal stability of ZrSiON based solar selective absorbing coating

Solar selective absorbing coatings(SSACs)are required to have not only excellent optical property but also outstanding thermal stability for high temperature applications.The optical properties of Mo/ZrSiN/ZrSiON/SiO_(2) SSAC had been optimized successfully before.Herein,we are focusing on the evaluation and mechanism of thermal stability of this multilayer coating for its potential applications in concentrated solar power(CSP)systems.Fortunately,the coating exhibits excellent thermal stability after aging at 400℃ for 1500 h in vacuum.At aging temperature of 500℃ for 1000 h or 600℃ for 300 h in vacuum,the slight inter-diffusion between Mo layer and stainless steel(SS)substrate occurs.At higher aging temperature of 700℃ for 100 h in vacuum,the serious inter-diffusion between Mo layer and SS substrate leads to invalidation of the coating,which has been evidenced by Rutherford backscattering spectrometry(RBS)and X-ray diffraction(XRD)technologies.Additionally,this coating also has an outstanding thermal stability after aging at 400℃for 300 h in air.A heating-cooling cycling(HCC)treatment evidences the good thermal stability of this coating working in cold environment(60℃).The results reveal that this coating can be a promising candidate not only for CSP system in high temperatures but also for usage in cold environment.