Spectrally selective coating of nanoparticles (Co₃O₄:Cr₂O₃) incorporated in carbon to captivate solar energy

Abstract

Innovatory nanocomposite comprising nanomaterials Co 3 O 4 :Cr 2 O 3 and carbon (fuel ash) was designed to absorb solar energy. Different concentration ratios of Co 3 O 4 and Cr 2 O 3 nanoparticles were utilized as a dopant for fuel thin films synthesis via spin and casting methods on glass and aluminum substrates. The opticalproperties of the modified films demonstrated in the range of 250 to 1300 nm. The data were interpreted in terms of a phonon-assisted theory. Energy gap (E g ) of doped C was calculated with different concentration ratios of Co 3 O 4 :Cr 2 O 3 (0.5:2.5, 1:2, 1.5:1.5, 2:1, 2.5:0.5) wt%, and fixed concentration of C in 7wt%. The results showed E g of the doped samples in the range of 2.9 to 3.9 eV. In addition, the intensity of the solar radiation was measured. The absorptivity was in the range of 88 to 93.6%. The above results are comparable to those of semiconductors and have high absorptivity values when the nanocomposite was utilized on a flat plate collector as a coating to trap and absorb solar energy. K E Y W O R D S chromium oxide, cobalt oxide, emissivity and absorptivity, energy band gap, optical properties 1 | INTRODUCTIONGenerally, Iraq has 240 days of strong sunlight with energy of 5 kWh per square meter in a day. 1 Harvesting solar energy and utilizing it in domestic applications, such as heating the water or ventilation residential complexes, would be highly cost effective and environment friendly. Nanocomposite films are used for this purpose. The technology includes the use of the nanocomposite films as a coating on a flat plate collector to be spectrally selective surface. This surface has low emissivity and high absorptivity to solar energy to convert this solar light into heat. 1,2 Doping nanomaterials with carbon can cause a remarkable change to its optical properties. [3][4][5] Cobalt oxide (Co 3 O 4 ) is a prevalent factor having several oxidization states because of its unusual chemical and physical features. It is used in ceramics production as an additional factor to produce blue coloring glazes, photo-catalysis, 6-10 and absorbance energy storage. 5,11 Further, Co 3 O 4 does has significant electrical properties. When Co 3 O 4 is added to chromium oxide (Cr 2 O 3 ), a conductive network is created through the pores. 12-15 Among the oxides family, Co 3 O 4 is one of the multilateral oxide sided, it has properties similar to a p-type semiconductor, and the band gap ranges from 2.23 to 3.38 eV. 16,17 Co 3 O 4 has attracted exceptional attention in the domain of application technology for pigments and solar-selective surfaces. [18][19][20] The particle size of Co 3 O 4 for nano-or micro-size provides perfect performance for electrochemical of different ranges in electronic applications and solar energy coating. [21][22][23][24] Nanocrystalline thin films nickel-cobalt oxides (NiO-CoO) were deposited on steel and glass substrates to produce thin films of different concentrations by the chemical bath deposition (CBD) method. These thin films exhibited semiconductor feature...

Upper bound efficiency for thermal radiation energy conversion by using spectrally selective electrical, chemical and mechanical work extractors

“…In [11], it was shown that nanoparticles-pigmented black paints can be engineered to simultaneously achieve solar-selectivity and durability at 750 ºC. Spectrally selective surfaces based on carbon surfaces doped with (Co 3 O 4 -Cr 2 O 3 ) nanocomposite for high-temperature operation have been investigated in [12], and in [13], thermally resilient hafnium carbide was used to realize a spectral selective cut-off absorber operating at high temperatures. A multilayer solar selective absorber consisting of Cu/Al 2 O 3 /Cr/SiO 2 /Cr/SiO 2 has a solar absorptance of about 0.954 and a thermal emittance of 0.196 at the temperature of 773 K [14].…”

In Situ Oxidizing Commercial Alloy to Achieve Selective Solar Absorption with High-Temperature Stability

“…Various methods have been proposed to prepare solar selective absorbers (SSAs). One simple method is to coat a nanolayer on the substrate to achieve selective spectra, such as spin-coating, , dip-coating, , and spray-coating. , However, low adhesion between the coating and the substrate would limit its stability. Furthermore, physical vapor deposition , or laser sintering methods can be used to improve the high-temperature stability of SSAs.…”