thermal emittance
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Author(s):  
Yoshiaki Nishijima ◽  
Shinya Morimoto ◽  
Armandas Balcytis ◽  
Tomoki Hashizume ◽  
Ryosuke Matsubara ◽  
...  

We demonstrate extraordinarily spectrally selective narrowband mid-infrared radiation absorbance and thermal emittance with resonant peak FWHM < 124nm at λ = 5.73 μm, corresponding to a Q-factor of ~ 92.3....


Coatings ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 17
Author(s):  
Jinxin Gu ◽  
Xin Zhao ◽  
Feifei Ren ◽  
Hang Wei ◽  
Shuhui Liang ◽  
...  

A metal layer with high reflectance is widely used as the bottom mirror of smart radiation devices. Reduced solar absorption and enhanced emittance tunability are required for smart radiation devices applied in aerospace. Thus, reducing the absorption in the metal is also necessary. Here, Al films have been prepared by direct current magnetron sputtering on the fused silica substrate. The structure, morphology, and optical properties of the films have been analyzed at various deposition temperatures and deposition times. The spectrum absorption tends to increase with the increase of surface roughness due to the agglomeration and size increase of Al particles, which has been further demonstrated by the simulated results. The optimized Al film exhibits small solar absorption of 0.14 and low emittance of 0.02, which benefits the application for smart radiation devices and solar reflectors.


2021 ◽  
Vol 1 (2) ◽  
pp. 007-020
Author(s):  
Gardey Merino María Celeste ◽  
Rodriguez Ibarra Mariana Estela ◽  
Lascalea Gustavo Enrique ◽  
Vázquez Patricia Graciela

This aim of this research is to produce Co3O4 oxide by means of one-step solution novel combustion methods using aspatic acid (C4H7NO4); lysine (C6H14N2O2); tris (hydroximethyl) aminomethane (NH2C (CH2OH)3) and ethylene diamine tetra-acetic acid (C10H16N2O8) as fuels. The pigments were characterized using X-ray diffraction, scanning and transmission electron microscopy, infrared spectroscopy with Fourier transform and UV-VIS-IR Spectrophotometry. The paint based on alkyd resin was made from pigments obtained (Co3O4 oxide). In order to make a comparison of the thermal emittance of the paint, two different formulations were prepared and these coating are named "absorbent paint coating": one that included 1% by weight of aluminum in metallic powder and another, with 1% of copper in metallic powder, respectively. The solar absorbance for the Co3O4 powders, plus quartz cuvette, gave a value of 0.9 in all cases. An extraordinary value of absorption on the coatings between 95 and 96% was noted. These results suggested that the synthesis of combustion in solution makes it possible to obtain a Co3O4 absorbent pigment with different fuels. These syntheses have a low environmental impact because they are one-step processes. All use low amounts of reactive ash obtained at a calcination of about 500 °C. These results suggest the possibility of utilizing this oxide in absorbent solar paints.


2021 ◽  
Vol 903 ◽  
pp. 125-132
Author(s):  
T.R. Mohan Kumar ◽  
P.V. Srihari ◽  
Sahas ◽  
M.S. Krupashankara

Higher solar absorptance and lower thermal emittance are the key factors for solar collectors. The use of thin films that are having mechanically resistant coatings are common practice in industries. The primary motivation of carrying this research work is to lower thermal emittance and maximize solar absorptance on SS304 substrate material. W-Al2O3 composite coatings are developed using magnetron sputtering process by considering the process parameters. The experimental plan is achieved based on Taguchi L9 orthogonal under various levels for deposition parameters. The tungsten and alumina thin films deposited using a co-sputtering were characterized using 410 - solar instrument for measuring solar absorptance and ET 100 Emissometer for measuring thermal emittance. The optimization for process parameters on thermal emittance and absorptance were carried out. It was found that for deposition parameters of DC power 750W, RF power 1050W and Argon gas flow rate of 250 sccm, absorptance of 0.758 with thermal emittance of 0.061 is observed with deposition was carried out on SS304 substrates.


2021 ◽  
Vol 143 (4) ◽  
Author(s):  
Giovanni Tanda ◽  
Mario Misale

Abstract In many areas of engineering, radiation heat transfer plays an important role and it is of great importance the knowledge of the thermal radiative properties of the surfaces involved. Radiation properties of solid materials are highly dependent on surface characteristics, e.g., surface roughness, surface damage, oxide layers, and deposited thin films, and cannot be assumed as those of pure materials, typically referred to optically smooth surfaces (OS). An experimental investigation of the thermal emittance of some metals (nickel, titanium, silver, and stainless steel) is presented. Experiments were conducted by using a radiometric apparatus able to measure the total normal emittance under different temperature and pressure conditions. The aim of this paper was to identify the separate roles of surface microgeometry alterations (surface roughness), surface damage, and surface coatings (i.e., presence of either thin films deposited onto a smooth surface or oxide layers formed on both smooth and rough surfaces) by undertaking carefully selected sets of experiments covering a relatively large temperature range.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tong Wang ◽  
Yi Wu ◽  
Lan Shi ◽  
Xinhua Hu ◽  
Min Chen ◽  
...  

AbstractAll-day passive radiative cooling has recently attracted tremendous interest by reflecting sunlight and radiating heat to the ultracold outer space. While some progress has been made, it still remains big challenge in fabricating highly efficient and low-cost radiative coolers for all-day and all-climates. Herein, we report a hierarchically structured polymethyl methacrylate (PMMA) film with a micropore array combined with random nanopores for highly efficient day- and nighttime passive radiative cooling. This hierarchically porous array PMMA film exhibits sufficiently high solar reflectance (0.95) and superior longwave infrared thermal emittance (0.98) and realizes subambient cooling of ~8.2 °C during the night and ~6.0 °C to ~8.9 °C during midday with an average cooling power of ~85 W/m2 under solar intensity of ~900 W/m2, and promisingly ~5.5 °C even under solar intensity of ~930 W/m2 and relative humidity of ~64% in hot and moist climate. The micropores and nanopores in the polymer film play crucial roles in enhancing the solar reflectance and thermal emittance.


2021 ◽  
Vol 6 ◽  
pp. 3
Author(s):  
Carlos David Hernández-Pérez ◽  
Enrique Barrera-Calva ◽  
Federico González ◽  
Victor Rentería Tapia

Today, even though exist a Titanium Nitride Oxide, TiNOX, a very good commercial solar absorber, the efforts to develop new and better solar absorbers like TiNOX are continuing in several laboratories all over the world. In this article, we used the ultrasonic spray pyrolysis technique to prepare manganese, Mn, Mn-doped α-Fe2O3 dark thin films deposited on titanium substrates. The results of an analysis of the solar absorptance and thermal emittance of these films are also presented here; the optical properties depend of the proportions of Mn and iron, Fe, in the spray solution and of the deposit temperature. The best solar absorptance (0.94) and thermal emittance (0.07) values of the films prepared at 600 °C for iron and manganese ion with concentrations of 0.0015 and 0.0035 mol/l, respectively, are comparable with the optical properties of the Titanium Nitride oxide, TiNOX, a very common commercial solar absorber used as an efficient coating for flat plate solar collectors industry.


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