Effect of metal particles in cermets on spectral selectivity

Abstract

Most cermet-based coatings achieve their solar selectivities by the tandem interference effect, which has been widely studied. This study focused on the spectral selectivity achieved by the scattering effect of metal particles in cermet-based coatings. Previous research proved that reasonable solar selectivities can be obtained for cermets in the regime of particles with a radius of the order of 100 nm, but their solar absorptance is low (<90%). In our research, the effect of metal particles on the spectral selectivity of cermets was studied by the Mie theory and Monte Carlo simulation for Cr, Ni, and W particles with radii of 10 nm, 50 nm, 100 nm, and 200 nm, which were embedded in Al2O3 and occupied 5% of the volume fraction. It was found that by arranging different particles in different layers, a very high solar absorptance (95.6%) could be achieved. Since their thermal emittance (∼25% at 600 °C) was higher than that of normal coatings, these coatings are recommended to be used in solar absorbers that have a high concentration factor. Finally, the dependent scattering effect was qualitatively considered by the coupled-dipole approach. With a metal volume fraction of 5%, it was found that the effect of dependent scattering was small and should not change the conclusions made based on independent scattering.

Effect of dependent scattering on light absorption in highly scattering random media

“…However, when particle density continues to increase or µ s is comparable with or much larger than µ a , a careful consideration of dependent scattering effect on total absorption is necessary because the interparticle interference of scattering waves may lead to a redistribution in particle absorption. This issue is becoming important as the recent growing interests in nanofluids, as well as other nanoparticle-based solar absorbers, which usually utilize plasmonic resonances of metallic particles to enhance solar absorption [28][29][30][31][32][33], finding their applications in concentrating solar power and direct-steam generation. In this situation, the scattering coefficient might be comparable with the absorption coefficient for plasmonic particles with diameter approaching 100nm.…”

The dependent scattering effect on radiative properties of micro/nanoscale discrete disordered media

“…However, when particle density continues to increase or κ s is comparable with or much larger than κ a , a careful consideration of DSE on total absorption is necessary because the interparticle interference of scattered waves may lead to a redistribution in particle absorption. This issue is becoming important as the recent growing interests in nanofluids, as well as other nanoparticle-based solar absorbers, which usually utilize plasmonic resonances of metallic particles to enhance solar absorption [46,[334][335][336][337][338] and find their applications in concentrating solar power, like direct-steam generation, photocatalysis, solar thermochemistry and solar desalination applications [339,340]. In some researches on the structural coloration based on disordered photonic structures, predictions based on ISA interpreted the experimental results poorly, partly due to the extremely-high absorption predicted by ISA for densely packed nanostructures.…”

Зависимости Оптических Свойств Металлических Наночастиц, Размещенных В Различных Средах, От Их Температуры

“…В последнее время были предложены наноструктурированные твердотельные поглотители с поглощающими НЧ и прозрачной твердой матрицей для эффективного поглощения солнечной энергии, для применения в высокотемпературных технологиях, в качестве эмиттеров света для последующего переизлучения тепловой энергии и т. д. [20,21]. Под действием интенсивного оптического (солнечного) излучения на наноструктурированные твердые поглотители энергия излучения поглощается НЧ и после этого передается окружению за счет теплопроводности.…”

“…Оптические свойства наноструктурированных твердотельных абсорберов при их нагреве до температур порядка тысяч кельвинов непрерывным оптическим (солнечным) излучением меняются с температурой [20,21]. При использовании поглощающих НЧ в матрице солнечного абсорбера под действием солнечного излучения нагреваются до одинаковых температур и НЧ, и матрица.…”

“…4 представлены зависимости факторов эффективности поглощения K abs излучения в диапазоне длин волн λ = 300−3000 nm однородными сферическими вольфрамовыми НЧ с радиусами r 0 = 50, 100, 150 nm, размещенными в окиси алюминия Al 2 O 3 , при температурах НЧ и окиси T 0 = T м = 300, 2300 K. Нормированная интенсивность солнечного излучения I sn также представлена на рисунке. Отметим, что исследование оптических свойств вольфрамовых НЧ, разме-щенных в окиси алюминия, при начальной температуре проведено в [21]. Оптические постоянные вольфрама и окиси алюминия взяты из [19,23].…”