Optical Properties Of Coatings Research Articles

Effect of (Fe0.8Cr0.2)2O3 pigment on the optical properties of ZnO–B2O3–SiO2 glass-based coatings for double-glass photovoltaic modules

Solving technical issues of light pollution, thermal protection, color aesthetics, and weathering resistance for the coating layer used in double-glass photovoltaic modules of a solar panel, new coating materials were produced using ZnO–B2O3–SiO2 glass frit and (Fe0.8Cr0.2)2O3 pigment. In this work, the crystal structure, the microstructure, the distribution of Fe and Cr elements, the diffusion of element Fe, the adhesion and the optical properties of the coatings have been characterized. The surface roughness of the coatings has a more significant alteration when the (Fe0.8Cr0.2)2O3 content is greater than 49 wt%. For the coating doped with 46 wt% (Fe0.8Cr0.2)2O3, the amount of Fe diffused into the glassy phase gradually increases from 0.17 wt% to 0.54 wt% as the heat-treatment temperature increased from 650 °C to 720 °C. The effects of (Fe0.8Cr0.2)2O3 pigment content and heat-treatment temperature on the optical properties of coatings were explained mainly from the coatings surface roughness, Fe-redox induced pore formation, Fe-diffusion, and formation of large defects surfaced for the coatings.

Effect of Blending of Shellac, Carbonyl Iron Powder, and Carbonyl Iron Powder/Carbon Nanotube Microcapsules on the Properties of Coatings

Nine sets of orthogonal experimental samples were prepared by examining four factors: shellac microcapsules, carbonyl iron powder (CIP) microcapsules, CIP/ carbon nanotube (CNT) microcapsules, and primer coating thickness. By testing the morphology and performance of the coating and using the fracture elongation of the coating as an orthogonal experimental analysis, the maximum factor affecting the fracture elongation of shellac, CIP, and CIP/CNT microcapsule coatings was determined. The first two factors that had a significant impact on the fracture elongation of the coating were the content of CIP/CNT microcapsules and shellac microcapsules. In order to further optimize the coating performance, important factor experiments were conducted, using the content of CIP/CNT microcapsules and shellac microcapsules as variables. It was found that the coating had the best performance when the content of CIP/CNT microcapsules was 7.0% and the content of shellac microcapsules was 4.0%. The optical properties of coatings with added shellac, CIP, and CIP/CNT microcapsules were tested, and the color difference and glossiness of the coatings showed little change. The mechanical properties of coatings with added shellac, CIP, and CIP/CNT microcapsules were tested. The blending of the three types of microcapsules enhanced the toughness of the coating to a certain extent, and suppressed the generation of micro-cracks, demonstrating a good self-healing effect. The electromagnetic-absorption performance of coatings with added shellac, CIP, and CIP/CNT microcapsules was tested. The blending of shellac, CIP, and CIP/CNT microcapsules exhibited two effective bands of electromagnetic absorption and a good absorption performance at a relatively wide frequency range. The combination of shellac, CIP, and CIP/CNT microcapsules endows the fiberboard surface with self-healing and electromagnetic-absorption functions, while maintaining the original performance of the water-based coating. The results can be used for application of surface coatings on wooden materials with dual functions of self-healing and electromagnetic absorption.

Effect of Three Kinds of Aloe Emodin Microcapsules Prepared by SDBS, OP-10 and TWEEN-80 Emulsifiers on Antibacterial, Optical and Mechanical Properties of Water-Based Coating for MDF

To investigate an impact of microcapsules on water-based coatings for a medium density fiberboard (MDF), three types of aloe emodin microcapsules prepared at a 3.0% concentration of SDBS, OP-10 and TWEEN-80 emulsifiers were added to the water-based coatings and applied on a MDF surface. Then, three sets of coatings were tested. Antibacterial properties of three groups of coatings on MDF surface increased with the addition of aloe emodin microcapsule content, and antibacterial properties of the water-based coating against Escherichia coli in the three groups were slightly superior to that of Staphylococcus aureus. The water-based coatings on the MDF surface with SDBS as the emulsifier showed the highest antibacterial rates of 74.1% and 66.0% against Escherichia coli and Staphylococcus aureus, respectively. The antibacterial rates of 70.0% and 62.8% were achieved for the OP-10 emulsifier group, and 67.0% and 61.9% for the TWEEN-80 emulsifier group, respectively. The aloe emodin microcapsules prepared at a 3.0% concentration of SDBS, OP-10 and TWEEN-80 emulsifiers inhibit bacterial growth and improve the mechanical and optical properties of coatings. It supplies technical references for the utilization of aloe emodin microcapsules to the antibacterial coating on the surface of wooden furniture.

Influence of metallo-dielectric optical properties on thermal resistance and solar heat gain coefficient of multi-pane glazing systems in hot and cold climates

ABSTRACT The design of efficient windows and building facades in relation to their energy-saving potentials can be developed through an advanced computational modeling analysis, and thus an effective basis of comparison of the thermal performance of glazing systems can be realized. This study simulates the behavior of window systems that integrate partitioning radiant shades, where the latter are situated between typical glass panes comprising an insulated glazing unit. The partitioning shades comprise of spectrally selective metallo-dielectric coatings that modulate optical transmittance in the visible, infrared and mid-infrared regions. Wide variety of window configurations are studied, and the results are analyzed based on the system performance criteria of thermal resistance (R-value and U-value) and solar heat gain coefficient. The comparative performance assessment of single, double, triple and quadruple ‘pane’ glazing systems in relation to internal and external environmental conditions is presented. The effects of different parameters such as fill gas, inter-pane distance, pane thickness and optical properties of coatings on thermal behavior of the fenestration system are presented. Optimal design parameters for cold and hot climates are proposed; and the results show that it is possible to reduce up to 90% heat loss in winter for the most effective configuration.

Investigation of Polystyrene-Based Microspheres from Different Copolymers and Their Structural Color Coatings on Wood Surface

Six kinds of polystyrene (PSt)-based colloidal microspheres were synthesized by adding acrylic acid (AA), methyl methacrylate (MMA), and butyl acrylate (BA) as comonomers in styrene emulsion polymerization. The structurally colored coatings on a wood surface were self-assembled by thermally assisted gravity deposition of these microspheres. Chemical compositions and structures of microspheres and morphological characteristics of microspheres and structural color coatings, as well as optical properties of coatings and their generated structural colors, were studied. Pure PSt microspheres had a smooth surface and uniform structure, while microspheres of copolymers had core–shell morphologies and a rough surface. Only poly(styrene-acrylic acid) (P(St-AA)) microspheres had good monodispersity and the resulting coating had a well-ordered photonic crystal structure. However, other kinds of microspheres could form short ranges of ordered amorphous photonic crystal structures and they displayed structural colors. Both the reflectivity of coatings to visible light and structural colors varied with microsphere size and self-assembly temperature.

Comparison of the effect of non-metal and rare-earth element doping on structural and optical properties of CuO/TiO2 one-dimensional photonic crystals

The photonic crystal materials are new generation advanced materials with various application areas. One-dimensional (1-D) photonic crystals are one kind of that can be produced easily. High quality structural colored surfaces could be obtained by high dielectric contrast between stocked layers such as CuO and TiO2. In this study, five-layered CuO/TiO2 multilayers prepared by the sol-gel method grown on borosilicate glass substrates by spin coating. Nitrogen and Cerium ions were doped into the TiO2 structure. X-Ray Diffractometer (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscope (SEM), Photoluminescence Spectroscopy (PL), UV-Vis Spectrophotometer (UV–Vis) and Optic Microscope (OM) devices were used to characterize the effects of these non-metal and rare earth dopants on the phase, structural and optical properties of coatings. Violet, indigo, green, yellow and red structural colors were obtained from photonic crystal coatings consist of monoclinic tenorite and anatase layers. It was found that the size of the anatase crystal decreased with the doping of both N and Ce elements. Also, both dopants have positive effects on improving surface morphologies. The lower crystalline size, the better surface morphology, and the more vivid structural color properties were obtained by Ce doping while a higher degree of redshift obtained by the N doping.

Coatings Based on Al2Au Intermetallic Compound: Structure and Optical Properties

The methods of X-ray diffraction analysis and transmission electron microscopy were used to study the structure of coatings based on the Al2Au intermetallic compound. It has been shown that after the deposition, the coating is in an amorphous state. The annealing of the coating at 500°C for 15 min results in initial stages of crystallization. In the annealed coating, signs of a retained amorphous structure and grains of the Al2Au intermetallic compound with a size of 30–100 nm are observed. In addition, a small amount of the intermetallic phase AlAu is fixed in the coating after annealing. Optical characteristics of the annealed sample have been measured; a comparison with literature data on the structure and optical properties of coatings obtained by different methods was performed.

Features of degradation and recovery of the optical properties of coatings based on ZnO powder modified with nanoparticles after irradiation

ABSTRACTThe effect of electron irradiation with energy of 30 keV and fluence up to 7 × 1016 cm−2 on diffuse reflection spectra in situ of coatings based on ZnO powders unmodified and modified with zirconium dioxide and aluminum oxide nanopowders was investigated. The higher radiation stability of coatings based on modified pigments in comparison to unmodified pigments has been established. A significant recovery of the reflection spectra of irradiated coatings after exposure to residual vacuum and air was shown.

The Influence of Technological Regimes of Synthesizing a Solar Furnace on the Phase Composition of TiO2-CuO Cermets and the Optical Properties of Coatings on Their Basis

We present the results of studying the effect of technological synthesis regimes of a solar furnace using the method of a partial metal reduction of one of the oxides on the phase formation of cermet composite materials of the TiO2-CuO system. It has been established that the phase composition of the synthesized cermet composite materials depends on the carbon concentration, melting temperature and cooling rate. The dependence of the spectral-optical properties of selectively absorbing coatings on the production technology and properties of synthesized composite materials has been presented. It has been found that the coatings fabricated by melting in air with overheating at a melt cooling rate of about 105–106°C/s have the highest values of the integral absorption coefficient, α s = 91.0–94.5%.

Fabrication and characterization of multiscale, fractal textured solar selective coatings

Photothermal conversion efficiency depends significantly on the selectivity of the thermal receiver surface through which a heat transfer fluid flows in a concentrated solar power system. This paper presents studies on novel multiscale, fractal textured solar selective coatings for solar thermal applications. The fractal surfaces are fabricated integrally on the substrate material using electrodeposition. The coatings are described in terms of fractal parameters that are uniquely determined from surface measurements, and the optical properties of the coatings are experimentally characterized in detail in terms of the fractal parameters. The effects of heat treatment on the optical properties of coatings over a range of fractal parameters are also described. The study is presented considering coatings on copper to demonstrate that fractal texturing of the surface provides a nearly three-fold performance improvement compared to coatings with no texturing or heat treatment. The findings equally apply to other materials used in higher temperature solar thermal applications.

Experimental studies on a combined near infrared (NIR) curing system with a convective oven

Abstract Near-infrared (NIR) curing recently became viable for the rapid curing of coating layers in several industries that require much faster line speeds to both increase production and reduce the system size, thereby saving on the overall curing cost. Previous works have revealed how NIR penetrates and efficiently heats the coating layer on top of a steel substrate. Despite these great efforts, the industry still requires more experimental evidence, data collection and system optimization to replace conventional hot air dryers with NIR dryers in the near future. Hence, we aim to develop a highly efficient NIR heating module, investigate its basic performance and suggest its optimized operation for the coil coating industry. First, we design and develop a NIR dryer integrated with a heating module, conveyor and waste heat recirculation loop. Second, we investigate the dynamic temperature response of the targeted steel substrate for various optical properties of coatings, such as absorption, reflectance and transmittance. Third, the curing performance is also observed in the NIR dryer for different coatings and operating conditions. We then discuss why NIR heating alone cannot meet the successful curing of a coating on substrates in terms of surface adhesion and resistance testing. Finally, we suggest a robust and stable operation method that combines NIR and convective oven heating, which allows for successfully cured outputs.

Properties of optical coatings formed on silicate glass from silica sol with alumina sol additive

The addition of 0.1—0.5 mol.% of alumina sol causes the increase in hardness of single-layer optical coatings, produced on silicate glass from silica sol at gel setting temperatures of 60—80 °C, from F—H to 7H—9H. Small concentrations of the additive do not affect the light transmission of the coated glasses. Atomic force microscopy has shown the coating surface to be homogeneous, the surface roughness not exceeding 4.0 nm.

Defect-related properties of optical coatings

Abstract Defects in optical coatings are a major factor degrading their performance. Based on the nature of defects, we classified them into two categories: visible defects and non-visible defects. Visible defects result from the replication of substrate imperfections or particulates within the coatings by subsequent layers and can increase scattering loss, produce critical errors in extreme ultraviolet lithography, weaken mechanical and environmental stability, and reduce laser damage resistance. Non-visible defects mainly involve a decrease in laser damage resistance but typically have no influence on other properties of optical coatings. In the case of widely used HfO2/SiO2 dielectric coatings, metallic Hf nano-clusters, off-stoichiometric HfO2 nano-clusters, or areas of high-density electronic defects have been postulated as possible sources for non-visible defects. The emphasis of this review is devoted to discussing localized defect-driven laser-induced damage (LID) in optical coatings used for nanosecond-scale pulsed laser applications, but consideration is also given to other properties of optical coatings such as scattering, environmental stability, etc. The low densities and diverse properties of defects make the systematic study of LID initiating from localized defects time-consuming and very challenging. Experimental and theoretical studies of localized defect-driven LID using artificial defects whose properties can be well controlled are highlighted.

Surface control and cryogenic durability of transparent CNT coatings on dip-coated glass substrates

Transparent carbon nanotube (CNT) coatings were deposited on boro-silicate glass substrates by dip-coating. Ultraviolet–visible (UV) spectra, surface resistance measurement, and the wettability tests were used to investigate the optical transmittance and electrical properties of these CNT coatings. The changes in electrical and optical properties of these coatings were observed to be functions of the number of dip-coating cycles. The surface resistance of the CNT coated substrates decreased dramatically as the number of dip-coatings was increased, whereas the increases in the CNT layer thickness beyond that for the first dipping cycle had little effect on the transparent-properties. Static contact angle measurements proved to be an effective means for evaluating the surface morphology of CNT coatings. The interfacial durability of the CNT coatings on a glass substrate was much better than that of ITO coatings over the temperature range from −150°C to +150°C.

Effect of Fe3+ ions on the thermal and optical properties of the ceramic coating grown in-situ on AZ31 Mg Alloy

This research investigates the effect of Fe2(SO4)3 on the thermal and optical properties of the ceramic coatings formed on AZ31 Mg alloy. The different ceramic coatings were obtained by plasma electrolytic oxidation (PEO) in electrolytes that contain varied concentrations of Fe2(SO4)3. The microstructure, element distribution, composition as well as the thermal and optical properties of the coatings were studied with scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray Diffraction (XRD), UV–VIS–NIR spectrophotometer and infrared reflectometer. The results show that all of the coatings prepared were mainly composed with MgO, with trace-amount of Fe3O4 presents and Fe seems entered into the MgO crystal structure. With the increasing of the concentration of Fe2(SO4)3, the solar absorptance and infrared emittance increased initially but then remain stable. We found that at the concentrations 8 g L−1, the coating has the highest solar absorptance (0.94) and infrared emittance (0.83). Our results show that coatings formed with this method could be useful as a thermal control coating in a variety of applications, such as in the spacecraft.

Optical properties of coatings of oxidized graphite and its intercalated compound with ammonium dodecahydro-closo-dodecaborate

The influence of light radiation with different wavelengths (546, 380, 365 nm) on the coatings of oxidized graphite and its intercalated compound with ammonium dodecahydro-(NH4)2B12H12 was studied. The transmission and absorption spectra of the coatings were measured before and after irradiation. It was shown that the optical density of the coatings increased because of carbon release (blackening), which was especially strong during UV irradiation. Under the same conditions (wavelength, power, time), the change in the optical density was much larger for the intercalated compound than for oxidized graphite. This can be explained by the presence of the B12H122− anion in the former.

Influence of the target composition on reactively sputtered titanium oxide films

Titanium dioxide thin films have many interesting properties and are used in various applications. High refractive index of titania makes it attractive for the glass coating industry, where it is used in low-emissivity and antireflective coatings. Magnetron sputtering is the most common deposition technique for large area coatings and a high deposition rate is therefore of obvious interest. It has been shown previously that high rate can be achieved using substoichiometric targets. This work deals with reactive magnetron sputtering of titanium oxide films from TiO x targets with different oxygen contents. The deposition rate and hysteresis behaviour are disclosed. Films were prepared at various oxygen flows and all films were deposited onto glass and silicon substrates with no external heating. The elemental compositions and structures of deposited films were evaluated by means of X-ray photoelectron spectroscopy, elastic recoil detection analysis and X-ray diffraction. All deposited films were X-ray amorphous. No significant effect of the target composition on the optical properties of coatings was observed. However, the residual atmosphere is shown to contribute to the oxidation of growing films.

Degradation model of the optical properties of the thermal control coatings

On the basis of experimental results，the degradation model of the optical properties of thermal control coatings due to space environment interaction are proposed. The optical properties of thermal control coatings prepared by complex refractive index materials are analyzed by using the concept of graded index，and the expressions of the changed optical properties of the coatings are given. Applications of the degradation model are also discussed.

Combined laser calorimetry and surface thermal lens technique for optical coating characterization

A combined laser calorimetry (LC) and surface thermal lens (STL) technique with a continuous-wave (cw) modulated excitation is developed for characterizing the absorption properties of optical coatings. LC and STL signals are simultaneously obtained with highly reflective coating samples irradiated at 1064 nm. With a modulated irradiation power of 2.6 W, the limits of absorptance detection for the LC and STL signals are approximately 1.2×10-6 and 0.5×10-6, respectively. The influences of different excitation parameters (modulation frequency, excitation-beam power and irradiation time) on the absorptance measurements are experimentally analyzed. The applicability of the combined LC and STL technique to the investigation of the laser-induced absorption changes of optical coatings in an absolute absorptance scale is demonstrated.

Electrical and optical properties of titanium nitride coatings prepared by atmospheric pressure chemical vapor deposition

Abstract In order to examine the possibility for TiN coatings to be low-E, TiN coatings were deposited on the glass substrates by atmospheric pressure chemical vapor deposition using titanium tetrachloride (TiCl 4 ) and ammonia (NH 3 ) as precursors. X-ray diffraction, sheet resistance measurement, optical transmittance spectroscopy and infrared reflectance spectroscopy were carried out to determine the relationships between the preparation parameters and the microstructure, electrical and optical properties of the coatings. The results showed that the concentration of crystals increased with increasing the substrate temperature and the flow of TiCl 4 , resulting in a decrease of the electrical resistivity. The optical transmittance of TiN thin films was strongly dependent on the gas flow and the substrate temperature. Under optimum conditions, continuous polycrystalline TiN coatings with FCC structure were obtained with an electrical conductivity around 34.5 Ω/□, an optical transmittance around 50% in the visible range, and an infrared reflectance higher than 50% above 3000 nm. This indicates that TiN coated glasses may be possible candidates for high IR reflectance windows.