Radiant emissivity of tungsten in the infrared region of the spectrum

The spectral radiant emissivity of tungsten ribbon ranging from 1 to 5. 1μ thick was measured in the temperature range from 1244–2441K. It was shown that the radiant emissivity of tungsten in the infrared region does not obey the Hagen-Rubens relation.     

低温红外辐射源研究

随着空间红外探测、卫星遥感等技术的飞速发展,低温红外辐射源的需求日益迫切。研制了一种基于液体循环控温原理的低温红外辐射源。辐射源的工作温度范围为-60℃～50 ℃,控温精度达到0.01 ℃,有效发射率优于0.999 7。首先阐述了低温红外辐射源的设计原理,介绍了辐射源腔形设计,使用基于蒙特卡罗算法的软件STEEP3计算了辐射腔的有效发射率;接着对辐射腔内部温度特性进行了研究,实验结果表明低温红外辐射源辐射腔温度均匀性优于0.02 ℃,腔底温度稳定性优于0.05 ℃/h;最后通过与镓熔点黑体比较得到低温红外辐射源在29.76 ℃时的光谱发射率,与仿真计算结果一致。     

双波长高精度红外测温仪

利用双波长红外测温方法,通过黑体红外辐射曲线中双波长等比吸收的原理消除了由于辐射环境中水蒸气等外界吸收原因造成的单波长红外测温仪中的测量误差,实现更稳定的高精度红外测温.该方法绕开了传统红外测温方法中"辐射率修正困难"的问题.同时利用此红外测温仪器改进了金属钨电子逸出功测量实验.     

基于激光旋转加热的非导电材料高温光谱发射率测试方法与装置

光谱发射率是表征材料热物理性能的重要参数。对于非导电材料的高温光谱发射率测试,一般采用高温加热炉加热或辐射加热的方式来进行发射率测试,存在的问题是采用高温石墨炉加热时,样品可能会与高温石墨发生化学反应,从而破坏材料原有物性;采用辐射加热,一般是单向静止加热,会存在样品温场梯度非均匀分布的问题。基于激光旋转加热和样品/黑体整体一体化设计,提出了一种“样品动中测”的非导电材料高温光谱发射率测试新方法,建立了相应的测量模型,突破了传统的 “样品静中测”的局限,样品与参考黑体共形一体化设计,采用微区域光谱辐射成像方法,同时测量参考黑体和样品的光谱辐射能量与温度。建立了激光旋转加热状态下的热传导方程,对典型样品材料的温度分布进行了仿真计算,结果表明旋转样品温场分布较为均匀,分析了温场分布与红外光谱发射率测量误差间的关系,给出了适用于本测试方法的材料的热导率下限值。基于该方法,搭建了相应的测量装置,对典型材料碳化硅在1 000 K时的光谱发射率进行了测试,在4 μm处对各个典型高温温度点的光谱发射率进行了测试,得到了碳化硅材料在红外波段的光谱发射率波长变化和温度变化规律特性。与国外的测量结果进行了比对,结果较为一致,验证了激光旋转加热光谱发射率测试方法的可行性。采用此方法,不破坏样品本身的理化特性,样品加热升温速度快,测量温度范围上限高,有效减小了激光静止单向加热带来的温度不均匀性,可同时测量出样品和参考黑体的光谱辐射亮度及温度,无需另外再设计标准高温黑体,解决了现有非导电材料高温光谱发射率测试中非均匀加热和辐射能量同步比对测量的问题,可应用于多种非导电材料高温光谱发射率的测试。     

Integral radiant emissivity of tungsten in the 1200–2800°K temperature range

Data on the spectral radiant emissivity of tungsten are used to compute the integral radiant emissivity of this element in the 1200–2800°K temperature range.The authors are grateful to G. P. Konyukhov and the Ural-2 programming staff for carrying out the computations.     

目标表面发射率对红外辐射偏振特性的影响分析

偏振探测不仅可以获得目标的光谱、强度、偏振态以及空间几何形状等参数,还可以获得更丰富的目标信息,有利于改善对目标的探测和识别能力。红外辐射偏振成像是近年来发展起来的一种新的红外探测技术,主要通过目标与场景的红外辐射偏振特性差异进行目标探测与识别。但由于红外辐射偏振信息在传输过程中,其偏振态会受到传输介质的影响,而通常基于实验分析总结目标红外偏振特性的方法难以对偏振传输过程中的影响因素进行估计,也不能定量描述各相关参数对于红外偏振信息的影响。通过微面元理论的双向反射分布函数模型,建立了基于偏振双向反射分布函数的红外辐射偏振传输方程, 推导分析了目标表面发射率对红外辐射偏振度的影响,结果表明：目标表面发射率对目标红外偏振度影响可以忽略;在理论分析基础上,有针对性的开展红外光谱偏振探测试验,试验数据分析与理论推导结论吻合。这表明：材料表面发射率的变化不影响目标表面的红外辐射偏振度。该研究成果有利于提高红外伪装探测的目标识别效率,可为进一步提高红外偏振成像系统的伪装目标探测提供新的途径和方法,如在伪装目标探测识别中,通过探测其表面的红外辐射偏振特性的改变实现伪装目标识别探测。     

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.     

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。     

温度对AZO薄膜红外辐射性能的影响

随着全球资源的减少和环境的恶化,节能减排已成为人们关注的焦点,具有保温隔热功能的低辐射玻璃成为研究的热点。提高玻璃保温隔热性能最有效的方法就是在其表面涂覆低辐射率层。原材料丰富、导电性能好、可见光透过率高等优势使得Al掺杂ZnO (AZO)薄膜成为最具潜力的低辐射率层。系统研究了温度对AZO薄膜红外辐射性能的影响,分析了变化机理。首先研究了在一定的温度下持续一段时间后,AZO薄膜的红外比辐射率的变化情况。然后研究了在变温环境中红外比辐射率的变化情况。采用直流磁控溅射法在室温下玻璃基片上沉积500 nm厚的AZO薄膜,将薄膜放到马弗炉中进行热处理,在100～400 ℃空气气氛下保温1 h,随炉冷却。采用X射线衍射仪对AZO薄膜进行物相分析,采用扫描电子显微镜观察薄膜表面形貌变化。利用四探针测试法测量AZO薄膜的电阻率,采用红外比辐射率测试仪测试薄膜红外比辐射率, 可见分光光度计测量可见光谱。测试的结果表明,薄膜热处理前后均为六角纤锌矿结构,(002)择优取向。300 ℃及以下热处理1 h后,(002)衍射峰增强,半高宽变窄,晶粒尺寸长大。随着热处理温度的升高,薄膜的电阻率先减小后增大,200 ℃热处理后的薄膜具有最小的电阻率(0.9×10-3 Ω·cm)。热处理温度升高,晶粒长大使得薄膜电阻率降低。热处理温度过高,薄膜会从空气中吸收氧,电阻率下降。薄膜的红外比辐射率变化趋势和电阻率的一致,在200 ℃热处理后获得最小值(0.48)。自由电子对红外光子有较强的反射作用,当电阻率低,自由电子浓度高的时候,更多的红外光子被反射,红外辐射作用弱,红外比辐射率小。薄膜的可见光透过率随着热处理温度的升高先减小后增大,200 ℃热处理后的薄膜的可见光透过率最小,但仍高达82%。这种变化是由于自由电子浓度变化引起的,自由电子对可见光有很强的反射作用。选取未热处理和200 ℃热处理后的样品进行变温红外比辐射率的测量,将样品放在可加热的样品台上,位置固定,在室温到350 ℃的升温和降温过程中每隔25 ℃测量一次红外比辐射率,结果表明,在室温到350 ℃的温度范围内,AZO薄膜的红外比辐射率在升温过程中随着温度的上升而增大,在降温过程中减小,经过整个升、降温过程后,薄膜的红外比辐射率增大。     

颜料含量对复合涂层红外发射率的作用机制研究

以聚氨酯(PU)为粘合剂,某片状金属粉为颜料,采用刮涂法制备了PU/片状金属复合涂层。对不同颜料含量条件下涂层的红外发射率进行了测试,并采用扫描电镜对涂层的微结构进行了观察。发射率测试结果表明,涂层发射率随金属粉含量增加呈“∪”型变化。微结构观察结果表明,PU/片状金属复合涂层由PU和片状金属粉交错堆叠而成,具有类似一维光子结构特征。基于涂层的微结构特征,对具有转折变化特征的4个金属粉含量点状态下涂层中一维光子结构的反射光谱进行了模拟计算,结果表明：PU/片状金属复合涂层的发射率随金属粉含量变化呈“∪”型变化关系特征主要是由涂层中一维光子结构的主反射峰中心波长随颜料含量增加所产生的蓝移现象引起的。     

瞬时多光谱辐射测温方法

采用光学多道分析仪测量了溴钨灯和氙闪光灯的辐射光谱,给出了一种辐射测温的数据处理方法,即在Planck灰体模型假定的基础上,进一步考虑发射率ε与波长的多项式依赖关系以及辐射本底对实验结果的影响,建立相应的多光谱测温数据处理方法,并用溴钨灯和氙闪光灯的实测光谱对其进行了验证.结果表明:对于连续光谱且发射率逼近黑体,可以假定发射率为常量,按Planck灰体模型处理;对于非连续光谱,当电流密度不高时,发射率与波长依赖关系较强,可以根据发射率与依赖波长的多项式关系并结合0＜ε＜1限定按Planck灰体模型处理.     

辐射器漫反射定向管表面热辐射方向性

为了得到辐射能的方向分布特性,利用蒙特卡罗法,研究了定向管内壁面为不等温灰体、其底部假想圆型辐射器为黑体时,管内壁发射率、管长与半径比、管内空气流速等参数的变化对管口表面当量定向发射率的影响,计算结果表明:管长与半径比增加,管口表面较大的当量定向发射率向小角度的天顶角方向移动,空气流速仅影响当量定向发射率数值大小。     

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).     

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。     

A thin radar-infrared stealth-compatible structure:Design,fabrication,and characterization

A thin radar-infrared stealth-compatible structure with reflectivity below -10 dB in the whole radar X wave band and infrared emissivity less than 0.3 in the infrared region of 8μm-14 μm is reported. The designed stealth-compatible structure consists of metallic frequency selective surface （MFSS）, resistive frequency selective surface （RFSS）, and metal backing from the top down, and it is only 2. l-mm thick. The MFSS is made up of some divided low infrared emissivity metal copper films, and the RFSS consists of a capacitive array of square resistive patches. They are placed close together, working as an admittance sheet because of a mutual influence between them, and the equivalent admittance sheet greatly reduces the thickness of the whole structure. The proposed stealth-compatible structure is verified both by simulations and by experimental results. These results indicate that our proposed stealth-compatible structure has potential applications in stealth fields.     

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.     

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.     

Ultrahigh infrared normal spectral emissivity of microstructured silicon coating Au film

We studied infrared normal spectral emissivity on quasi-periodic microstructured silicon, which was prepared by femtosecond laser irradiation in SF6 ambient gas, coated with 100 nm thick Au thin film. The observed emissivity is higher than any reported previously for a flat material with a thickness of less than 0.5 mm, at a temperature range of 200 °C to 400 °C. The emissivity over the measured wavelength region increases with temperature and the spike height. These results show the potential to be used as a flat blackbody source or for applications in infrared thermal sensor, detector, and stealth military technology.     

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.     

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.