Comparison of anti-corrosion properties of polyurethane based composite coatings with low infrared emissivity

Four polyurethane resins, pure polyurethane (PU), epoxy modified polyurethane (EPU), fluorinated polyurethane (FPU) and epoxy modified fluorinated polyurethane (EFPU), with similar polyurethane backbone structure but different grafting group were used as organic adhesive for preparing low infrared emissivity coatings with an extremely low emissivity near 0.10 at 8-14 μm, respectively. By using these four resins, the effect of different resin matrics on the corrosion protection of the low infrared emissivity coatings was investigated in detail by using neutral salt spray test, SEM and FTIR. It was found that the emissivity of the coatings with different resin matrics changes significantly in corrosion media. And the results indicated that the coating using EFPU as organic adhesive exhibited excellent corrosion resistance property which was mainly attributed to the presence of epoxy group and atomic fluorine in binder simultaneously.     

The epoxy-siloxane/Al composite coatings with low infrared emissivity for high temperature applications

Low infrared emissivity coatings with good thermal resistance were prepared by using epoxy-siloxane and aluminum as adhesive and pigment, respectively. The influence of chemical composition, surface texture, roughness and thickness on the infrared emissivity was systematically investigated. The detailed results of experimental investigation indicate that the cured composite coatings could possess low emissivity value. Due to reducing infrared absorption and forming uniform and compact char construction, the infrared emissivity decreases obviously. Both the surface roughness and thickness have a critical value, respectively. Too large roughness or thickness would not contribute to the decrease of the emissivity. Moreover, the composite coatings were tested for thermal stability in air to explore the effect of high-temperature environment on the emissivity. The results indicate that the composite coatings, still possessing low emissivity after the test, exhibit favorable thermal ageing and thermal shock resistance.     

Low infrared emissivity of polyurethane/Cu composite coatings

Polyurethane/Cu composite coatings with low infrared emissivity near to 0.10 at the wavelength of 8-14 μm were prepared by a simple and convenient process. The influences of the content of Cu powder, surface roughness, coating thickness and temperature on infrared emissivity of the coatings were systematically investigated. The results indicated that the emissivity decreases significantly with increasing content of Cu powder and coating thickness. The coatings with smooth surface exhibit lower emissivity values than those with rough coatings. Moreover, we found the relationship between the emissivity of coatings and temperature presents a “U” type, and the emissivity reaches to the minimum at about 380 K. The mechanisms of low emissivity were proposed by optical theories, which are found to be in a good agreement with the experimental results.     

目标表面发射率对红外热像仪测温精度的影响

介绍了红外热像仪测温原理,分析了影响红外热像仪测温精度的因素,计算了不同表面发射率下红外热像仪的测温误差曲线。理论分析表明,目标表面发射率越高,红外热像仪测温精度越高。实验改变表面发射率的设置,计算了不同表面发射率对应的总辐射亮度,得到TP8型长波红外热像仪能够精确测温时,目标表面发射率必须大于0.5的结果。最后,对表面发射率分别为0.96、0.93和0.3的3种材料进行实际测温,结果表明,材料表面发射率较高时,红外热像仪具有较好的测温精度。     

目标表面发射率对红外热像仪测温精度的影响

介绍了红外热像仪测温原理,分析了影响红外热像仪测温精度的因素,计算了不同表面发射率下红外热像仪的测温误差曲线。理论分析表明,目标表面发射率越高,红外热像仪测温精度越高。实验改变表面发射率的设置,计算了不同表面发射率对应的总辐射亮度,得到TP8型长波红外热像仪能够精确测温时,目标表面发射率必须大于0.5的结果。最后,对表面发射率分别为0.96、0.93和0.3的3种材料进行实际测温,结果表明,材料表面发射率较高时,红外热像仪具有较好的测温精度。     

Microstructure and infrared emissivity property of coating containing TiO2 formed on titanium alloy by microarc oxidation

Ceramic coatings containing TiO₂ were formed on Ti6Al2Zr1Mo1V alloy surface by microarc oxidation (MAO) method. The microstructure, phase and chemical composition of the coatings were analyzed by SEM, XRD and EDS techniques. The coating mainly consists of rutile TiO₂ and a small amount of anatase TiO₂. The infrared emissivity values of coated and uncoated titanium samples when exposed to 700 °C were tested. It was found that the coating exhibits a higher infrared emissivity value (about 0.9) in the wavelength range of 8–14 μm than that of the uncoated titanium alloy, although which shows a slight increase from 0.1 to 0.3 with increasing exposure time at 700 °C. The relatively high infrared emissivity value of the MAO coating is possibly attributed to the photon emission from the as formed TiO₂ phase.     

Optically active helical polyurethane@attapulgite composites: Effect of optical purity of S-1,1′-binaphthyl-2,2′-diol on infrared emissivity

Helical polyurethane@attapulgite (HPU@ATT) composites were prepared after the surface modification of the rod-like attapulgite (ATT). HPU@ATT composites based on S-1,1′-binaphthyl-2,2′-diol (S-BINOL) with different optical purity (O.P.) were characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The results indicate that the helical polyurethane has been successfully grafted onto the surfaces of the modified ATT without destroying the original crystalline structure of ATT. The rod-like nanoparticles were confirmed by transmission electron microscopy (TEM). Infrared emissivity values of HPU@ATT composites have been investigated, and the results indicate that the optical purity of monomer plays a very important role in the infrared emissivity for HPU@ATT owing to the effect of helical conformation and interchain hydrogen bonds. Along with the increased optical purity of S-BINOL, the infrared emissivity of HPU@ATT is reduced evidently. Infrared emissivity value of HPU@ATT based on S-BINOL with 100% optical purity is the lowest one (0.431).     

IRS400型材料发射率测试装置的研制

为了准确评估红外材料和涂层的隐身性能,研制了一套IRS400型材料发射率测试装置,主要用于温度范围（50～400）℃,光谱范围（3～5）m和（8～12）m的固体不透明材料和涂层定向发射率测量。给出IRS400型材料发射率测试装置的技术指标,阐述其工作原理,IRS400的光学系统采用全反射式设计,探测器选用钽酸锂热释电探测器,采用50 ℃～1 000 ℃黑体辐射源标准装置对黑体发射率B（1,2）进行标定。通过解决标定和环境温度补偿等关键技术,确保发射率测量不确定度小于2%(k=2)。     

Influence of remaining C on hardness and emissivity of SiC/SiO2 nanocomposite coating

SiC/SiO₂ nanocomposite coating was deposited by electron beam-physical vapor deposition (EB-PVD) through depositing SiC target on pre-oxidized 316 stainless steel (SS) substrate. High melting point component C remained and covered on the surface of ingot after evaporation. When SiC ingot was reused, remaining C had an effect on the composition, hardness and emissivity of SiC/SiO₂ nanocomposite coating. The composition of ingot and coating was studied by X-ray photoelectron spectroscopy (XPS). The influence of remaining C on hardness and spectral normal emissivity of SiC/SiO₂ nanocomposite coating was investigated by nanoindentation and Fourier transform infrared spectrum (FTIR), respectively. The results show that remaining C has a large effect on hardness and a minor effect on spectral normal emissivity of SiC/SiO₂ nanocomposite coating.     

Spectral emissivity of type E235B low carbon structural steel with different roughnesses

A self-built experimental apparatus was employed to study the spectral emissivity of type E235B low carbon structural steel in the wavelength range 2–15 μm at different temperatures by energy comparison method. The surface roughness and topography of the steel E235B were determined by a roughness tester and a scanning electron microscopy, respectively. And then, the spectral emissivity of steel E235B with six different roughnesses was measured before and after oxidation. The measurement results showed that the spectral emissivity increased with the increasing temperature and surface roughness before oxidation. The effect of roughness on the spectral emissivity is different at different wavelength and temperature ranges. However, the oscillatory behavior of the spectral emissivity was observed after oxidation. To explore the possible reasons for emissivity variation, the changes of surface roughness and optical roughness were investigated after oxidation. It is found that both the surface roughness and optical roughness increased after oxidation. Although the optical roughness can be used as one of the parameters to evaluate the effect of surface roughness on the spectral emissivity, it is insufficient to describe the effect of surface morphology on the spectral emissivity.     

Modeling emissivity of low-emissivity coating containing horizontally oriented metallic flake particles

The scattering and absorption cross sections of horizontally oriented metallic flake particles are estimated by extended geometric optics that includes diffraction and edge effects. Emissivity of the coating containing those particles is calculated using Kubelka–Munk theory. The dependence of emissivity of the coating on the radius, thickness, content of metallic flake particles and coating thickness is discussed. Finally, theoretical results are compared with the experimental measurements with Al/acrylic resin coating system and the results show that simulation values are in good agreement with experimental ones.     

Infrared technique for simultaneous determination of temperature and emissivity

This paper presents, in the context of materials dynamic behaviour study, a method for simultaneous measurement of the temperature and emissivity of a solid’s surface, by the use of infrared radiation. In contrast to existing methods, this method has no need for a pre-measurement of the surface emissivity. The emissivity and the temperature are measured simultaneously, by detecting the variations of emitted radiation and infrared radiation reflecting on the surface, at two different spectral zones. In this way, the accuracy of the measured temperature is greatly improved in cases were the surface optical properties vary during the measurement. Several experiments were carried out in order to complete the theoretical foundation of the method and to outline its accuracy and some of its limitations. There are various industrial applications of this method, for example the control of the temperature of the mechanical parts during work machining. One of them may be the measurement of the temperature of a sample during mechanical testing. An application of the method is proposed, that is easy to employ with non-sophisticated infrared and optical components. The results confirm the accuracy of the proposed method with an order of 3% of precision for temperature determination.     

Non-contact charge temperature measurement on industrial continuous furnaces and steel charge emissivity analysis

Continuous furnaces are commonly used for steel billet reheating before a rolling operation. It is necessary to perform a number of measurements to set-up and operate the optimization system of the furnaces correctly. A charge temperature measurement using infrared detectors can be one of the usable measurement techniques. This non-contact measurement method is based on the detection of infrared radiation emitted from a measured surface. The radiation intensity depends on the surface temperature and emissivity, which is one of the most important parameters for infrared measurements. Advantages of the non-contact temperature measurement, as well as some problems regarding the surface emissivity, are presented. The direct steel billet temperature measurement procedure using infra-red detectors, emissivity determination procedures, and example results are introduced. It is shown that steel emissivity can vary from approx. 0.17 to 0.8, depending on the surface state, scale formation, and wavelength interval. These problems are critical for the charge temperature measurement using the infra-red detectors, and are discussed in this paper.     

Infrared particle detection for battery electrode foils

Failures of electrochemical cells caused by internal shorts still are an important issue to be faced by the cell manufacturers and their customers. A major cause for internal shorts are contaminated electrode foils. These contaminations have to be detected securely via a non-destructive inspection technique integrated into the electrode manufacturing process. While optical detection already is state of the art, infrared detection of particles finds a new field of application in the battery electrode manufacturing process. This work presents two approaches focusing on electrode inspection by electromagnetic radiation (visible and infrared). Copper foils with a carbon based coating were intentionally contaminated by slivers of aluminum and copper as well as by abraded coating particles. Optical excitation by a flash and a luminescent lamp was applied at different angles in order to detect the reflected visible radiation. A laser impulse was used to heat up the specimen for infrared inspection. Both approaches resulted in setups providing a high contrast between contaminations and the coated electrode foil. It is shown that infrared detection offers a higher security thanks to its reliance on absorbance and emissivity instead of reflectivity as it is used for optical detection. Infrared Detection offers a potential since it is hardly influenced by the particle’s shape and orientation and the electrode’s waviness.     

Preparation of a novel infrared low-emissive coating from the Cu powder modified by the polyethylene wax

Cu powder was coated with polyethylene wax via the flux-capping method in hope to avoid the oxidation of it, so the increment of the infrared emissivity of the coating can be greatly reduced. The prepared product was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The infrared emissivity of the prepared material was measured by Infrared Emissometer. The influence parameters that will affect the emissivity of the coating were systematically investigated, such as the content of coated Cu powder, coating fineness, coating thickness and aging process. The results indicated that the infrared emissivity value of the coating was reduced after Cu powder was coated with polyethylene wax. The polyethylene wax/Cu composites presented a homogenous sheet structure when the content of Cu powder increased to 30 wt.%, and it has a lower emissivity. The infrared emissivity of the coating increases rapidly as thickness increases and becomes steady above thickness of 70 μm. The composite coating exhibits lower emissivity value and excellent physical properties at coated Cu content of 20 wt.%. The emissivity of the coating that was prepared from the modification of the Cu powder was decreased with the decrement of the grinding fineness and increased with the aging time. The emissivity of the coating that was prepared from the modification of the Cu powder is always lower than that of the coating that only composed of the Cu powder with the increment of the aging time. Therefore, it can be concluded that the anti-oxidation of Cu powder is greatly improved after it was modified by polyethylene wax, which results in a novel coating with long-run low emissivity.     

Dependence of infrared radiation on microstructure of polymer derived ceramic coating on steel

High infrared emissivity ceramic coatings were prepared on 304 steel by pyrolyzing reactions with poly(hydridomethylsiloxane) (PHMS) and Al/Cr₂O₃ based mixing powders. The effects of pyrolysis temperature, testing temperature and surface roughness on infrared radiation of polymer derived ceramic coating were systematically investigated. The results indicated that the coating pyrolyzed at 800 °C exhibited a slightly higher infrared emissivity value than that of the coating pyrolyzed at 600 °C, which was attributed to the enhancing photon emission caused by the complete conversion of Al to Al₂O₃ and PHMS pyrolysis into SiO₂, together with the introduction of Cr₂O₃ based mixing powders. The emissivity value in 3–8 μm waveband of the coating was lower about 0.03 at 600 °C compared with 800 °C testing temperature, while the emissivity value was almost the same in 8–20 μm waveband. The high surface roughness of the coating led to a slightly increasing emissivity due to the enhancing infrared absorbance.     

Influence of electrolyte temperature on properties and infrared emissivity of MAO ceramic coating on 6061 aluminum alloy

6061 aluminum alloy was treated by MAO at various temperatures of the alkali silicate electrolyte using pulsed bipolar current mode for ten minutes. The surface microstructures and properties were studied using SEM, EDX, and XRD. The infrared emissivities of the MAO ceramic coatings were measured at the 70 °C using FTIR spectrometer. The electrolyte temperature strongly affected all the surface properties. The MAO alumina ceramics prepared in cold electrolytes have volcano-like and accumulated particles microstructures, while those prepared in hot electrolytes were: rougher, thinner and contained grainy spherical hollow bulgy microstructures with more pore density and more sillimanite and cristobalite phases which enhanced the IR emissivity. Also, the increment of sillimanite and cristobalite phases moved the apparent peaks toward longer wavelengths, and broadened the opaque region of the IR spectra. As a result, the increment of electrolyte temperature from 12.3 °C to 90.5 °C increased the average of LWIR emissivity from 80.4% to 94.4%, respectively, for the MAO ceramic coatings.     

Surface temperature and emissivity from NOAA images

Summary A procedure to determine the surface temperature from images taken by AVHRR (advanced very high resolution radiometer) on board NOAA11 satellite is described in this paper. The importance of the emissivity parameter to estimate the surface temperature and the possibility to compute both temperature and emissivity maps from the two thermal infrared channels of the AVHRR is shown. Due to the relevance of its scientific content, this paper has been given priority by the Journal Direction.     

地表发射率的机载傅里叶变换红外光谱反演方法研究

介绍了利用机载傅里叶变换红外(FTIR)光谱仪测量地球、大气辐射的实验过程,并对由光谱仪测得的辐射与地表光谱发射率、大气透过率等参数的关系进行了深入的分析,给出了理论表达式。提出了一种基于梯度搜索的优化方法,即由机载FTIR光谱仪测得的辐亮度光谱反演得到方差最小的光谱发射率最优解。反演结果表明,在中红外波段,沙地平均光谱发射率为0.70,裸土地表平均光谱发射率为0.95。     

Acrylic coatings exhibiting improved hardness, solvent resistance and glossiness by using silica nano-composites

To prepare nano-composite emulsion acrylic resins with improved surface hardness and solvent resistance, nano-silica particles were treated with surfactants. The monomers of methyl methacrylate/butylacrylate were co-polymerized on the surface of dispersed silica particles. Several emulsions with different silica contents and copolymer mole fractions were prepared. Finally the emulsions were modified to water-based acrylic coatings and improved properties such as surface hardness, solvent resistance and glossiness were determined. The study of coatings was directed to find the improved resin by optimum surface properties. Size distribution and morphology of latexes were characterized by Fourier transform infrared spectroscopy, dynamic light scattering, transmission electron microscopy and scanning electron microscopy. The glass transition temperature of nano-composites was measured and discussed its relation with silica contents, monomer mole fractions and improved properties of coatings. The optimum pendulum hardness of coatings was on 0.46 methyl methacrylate mole fraction and 120 g silica content. An increase in pendulum hardness of nano-composites with the addition of modified silica was observed. DLS and TEM studies indicate that silica particles were dispersed homogenously through the polymer matrix.