白铜热氧化过程中光谱发射率特性研究

随着科技的发展,工业领域对白铜产品质量的要求日益提升;利用辐射测温技术对白铜在冶炼和加工时的温度进行精确测量,是决定产品质量的重要手段,因此研究白铜的光谱发射率特性就显得尤为重要。基于傅里叶红外光谱仪搭建的光谱发射率测量装置,测量了白铜在四个温度点（673,773,873和973 K）,波长范围2～22 μm内的光谱发射率,分别研究了波长、温度、加热时间和氧化对白铜光谱发射率的影响。研究发现,在氮气环境下白铜的光谱发射率随温度的升高而增加,随波长的增加而减少。当白铜暴露在空气环境中,随着温度的升高,其光谱发射率迅速增加。673 K时,白铜表面生成一层细微的氧化物颗粒,阻止白铜进一步氧化,这些氧化物颗粒的光谱发射率大于白铜基底,所以此温度下短波处的光谱发射率略微增加。773 K时,白铜表面氧化物的主要成分是Cu₂O,在实验过程中也观察到白铜表面逐渐变红的现象,这也是白铜在773 K温度下其光谱发射率迅速增加的原因。873 K时,白铜表面氧化物的种类和含量明显增多,氧化膜的厚度满足干涉效应条件,在白铜的光谱发射率曲线中可以明显地观察到干涉极值的演变,随着加热时间的增加,干涉极值逐渐向长波移动。随着温度的升高,白铜的抗氧化能力下降。973 K时,白铜表面的氧化程度最深,在XRD图中氧化物的峰值也最大,因此氧化1 h后由于干涉效应产生的干涉极值数最多。综上所述,波长、温度和氧化对白铜的光谱发射率有重要的影响,在运用辐射测温技术测量白铜温度时应充分考虑上述因素的影响。该研究丰富了白铜的光谱发射率数据,为辐射测温提供了真实可靠的数据支撑。     

Ti-6Al-4V合金方向光谱发射率特性研究

利用傅里叶红外光谱仪在温度范围为573～953 K、波长范围为3～20μm下测量Ti-6Al-4V合金在0°～84°下的方向光谱发射率,并系统研究了方向变化对其光谱发射率的影响。实验结果表明,在波长小于10.3μm的短波处,Ti-6Al-4V合金发射率在0°～84°下随角度变化呈现出类似绝缘体的特性,而在大于10.3μm的长波处,其变化呈现出类似金属的特性。该合金的光谱发射率在573～773 K范围内随温度的升高而增大,并且在0°～70°与80°～84°内随波长变化趋势相反。当Ti-6Al-4V合金氧化后,其发射率在60°时达到最大值且非金属特性在长波处随氧化时间增加越来越明显。由此可见,在不同测量角度下,温度、波长和氧化程度等因素对Ti-6Al-4V发射率的影响很大,该研究可以丰富Ti-6Al-4V合金的方向光谱发射率数据库,为辐射测温技术提供数据支持。     

温度和加热时间对大气环境中纯铁光谱发射率的影响

纯铁的光谱发射率受温度的影响很大,尤其是在大气环境中,由于温度升高加剧了表面的氧化,导致其光谱发射率发生了“无规律”变化。基于基尔霍夫定理,利用研制的反射法光谱发射率测量装置对纯铁1.55μm波长的光谱发射率进行了系统的研究,探讨了温度、加热时间等因素对纯铁光谱发射率的影响。研究结果表明：纯铁的光谱发射率随着温度的升高而增大,并且在一定的温度下出现了峰值和谷值,通过分析有氧化层时金属的发射率模型,解释了这种现象的发生。恒温长时间测量结果表明,在不同的温度下,加热时间对光谱发射率的影响不同。研究结果将进一步丰富纯铁的光谱发射率数据,并为其光谱发射率在大气环境中的应用提供了实验依据。     

300～1123K铜红外光谱发射率特性研究

基于基尔霍夫定律,利用砷化镓(GaAs)半导体激光器作为标准光源研制了一种能够准确实时测量不透明物体光谱发射率的反射式测量装置。利用该装置在300~1 123K之间对黄铜和紫铜两种样品在波长1.55μm处的光谱发射率进行了系统的研究,探讨了温度、氧化、加热时间等因素对两种铜样品光谱发射率的影响。实验结果表明:黄铜和紫铜的光谱发射率均随温度的升高而增大,并且紫铜的光谱发射率始终大于黄铜的光谱发射率,两种样品随温度的光谱发射率曲线均出现了峰值和谷值。通过分析有氧化膜时金属表面的反射模型,得到了金属表面氧化膜厚度的计算公式,并利用该公式估算了紫铜发射率出现峰值和谷值时氧化膜的厚度。恒温长时间测量结果表明:光谱发射率随加热时间出现小幅增大,2h后,由于样品表面氧化达到一定程度,氧化速率开始变缓,样品表面的光谱发射率也随之开始趋于稳定。样品在较高温度处的光谱发射率数值始终大于较低温度处的发射率数值。该研究进一步丰富了铜的光谱发射率数据,并为其光谱发射率的应用提供了实验依据。     

连铸坯表面发射率的测量研究

铸坯表面发射率是影响铸坯表面温度测量的一项重要的物理参数。利用辐射能比较测量发射率的方法,研制了一套高温铸坯发射率测量装置,其主要由加热系统、角度旋转系统、温度检测系统、真空控制系统以及背景辐射屏蔽系统等5部分组成。利用该装置测量了GCr15钢在不同角度、不同温度及不同氧化程度下的表面发射率。研究表明:角度增加对发射率的影响具有先增大后减小的变化规律;发射率会随着氧化程度的加深而变大,并且发射率极值点所对应的角度逐渐减小;随着温度的增加,发射率会随之增大,但是当温度超过1000℃后,其对发射率的影响较小。当温度为1000℃以上时,深度氧化的GCr15钢发射率的最大不确定度为0.0205。     

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。     

A3铁、304钢和201钢光谱发射率

随着科学技术日新月异的发展,红外测量技术在遥感、辐射测温、红外隐身、农业、医疗等领域都展现出了重要的应用前景。在花样众多的辐射测量中,材料的发射率是重要的参数之一。为满足材料发射率数据的需求,根据一套自主研制的光谱发射率测量装置对A3铁、304钢以及201钢在不同温度下的光谱发射率进行了精确的测量,并对影响发射率的几个因素做了深入的探究。结果显示：这三种钢材的发射率随温度升高而变大,同等温度下A3铁的发射率要高于304钢和201钢,且材料中的铬含量会降低材料的发射率值。采用XRD分析了三种材料表面氧化后的成分,并探讨了表面成分变化对发射率的影响。结果表明：A3铁氧化后生成不稳定的四氧化三铁Fe₃O₄和氧化亚铁FeO,各种成分的相互转变会导致光谱发射率发生较大的变化,而304钢和201钢表面氧化后主要生成氧化铬,因而光谱发射率也相对比较稳定。另外使用辐射光叠加原理和Christiansen效应成功解释了三种材料的发射率在大约10 μm处出现极大值的现象。该研究极大地丰富了三种材料的光谱发射率数据,为辐射测量技术在三种材料中的应用提供了强有力的数据支撑。     

热辐射体真实温度的测试研究

在辐射测温中，普遍存在一个问题，被测温度物体表面发射率影响很大，而物体的发射率很难确测量，这是因为发射率不仅与材料有关，而且还与波长，温度，表面状态（表面粗糙度，氧化程度等）有关，本文叙述一种利用多波长辐射法测量实际物体真实温度的方法，该方法利用最小二乘法原理拟合出实际热辐射体的光谱发射率曲线，从而使测量目标的真实温度成为可能。     

快速压缩作用下橄榄石的结构稳定性

结合不同的温度效应,研究了快速压缩过程对橄榄石结构稳定性的影响。分别在293、373、473、573、673、773 K下将橄榄石快速加压至3 GPa,在873、973、1073、1173 K下烧结橄榄石样品2 h后再在室温下快速加压至3 GPa。采用同步辐射X射线衍射、拉曼光谱、红外吸收光谱以及扫描电镜等技术分析了回收样品的结构和微观形貌。结果表明,上述过程中橄榄石结构均稳定,未发生由压力和温度导致的相变。橄榄石回收样品的微观形貌发生变化,晶粒细化。由于回收样品中存在残余应力以及晶粒细化,橄榄石的822 cm^–1和854 cm^–1拉曼特征峰出现了展宽和偏移。     

光谱发射率测试方法的不确定度分析

光谱发射率是材料重要的热物性参数之一,具有重要而广泛的应用需求。基于调制辐射源加热的光谱发射率测试方法能够实现材料高温光谱发射率和温度的同时测量,克服了传统测试对高温样品温度准确测量的依赖性。为研究和提高基于调制辐射源的光谱发射率测试方法的适用性,论文开展了测量反问题的数值模拟验证分析,研究分析了样品表面光谱发射率范围、温度范围和测量噪音等条件对光谱发射率测量不确定度的影响,并对光谱发射率反问题求解的数值不确定度与理论不确定度进行了定量评估。     

Investigation of the effects of Ni-based alloy K465 on the normal spectral emissivity during oxidation

The normal spectral emissivity of Ni-based alloy K465 during oxidation is experimentally measured at 810, 914 and 998 °C for 12 h in air over the wavelength from 1.3 to 2.4 μm. The combined standard uncertainty of the normal spectral emissivity is less than 3%. The oscillations of the emissivity and the effects of oxidation temperature, heating time and wavelength on the emissivity are investigated. The oscillations of the emissivity are formed by the interference effect between the radiation from the surfaces of the substrate and the oxidation film. The oscillation extremums of the emissivity shift towards larger wavelengths as the oxidation process proceeds. The results show that the normal spectral emissivity increases as the temperature increases at the initial time. The normal spectral emissivity decreases as wavelength increases except for the occurrence of the oscillations of the emissivity. The normal spectral emissivity increases rapidly at the initial heating time, and the change of emissivity becomes slow when the oxidation tends to be saturated gradually. Besides, the emissivity fitting models versus heating time and wavelength are established, which fit the experimental results very well. The emissivity relative errors of the fitting models are less than 4%.     

Monitoring synchrotron X‐ray‐induced radiolysis effects on metal (Fe,W) ions in high‐temperature aqueous fluids

Radiolysis‐induced effects on aqueous tungsten ions are observed to form a precipitate within seconds upon exposure to a synchrotron X‐ray micro‐beam in a WO₃ + H₂O system at 873 K and 200 MPa. In situ Fe K‐edge energy‐dispersive X‐ray absorption spectroscopy (ED‐XAS) measurements were made on Fe(II)Cl₂ aqueous solutions to 773 K in order to study the kinetics of high‐temperature reactions of Fe²⁺ and Fe³⁺ ions with transient radiolysis species. The radiolytic reactions in a fluid sample within a hydrothermal diamond anvil cell result in oxidation of the Fe²⁺ ion at 573 K and reduction of Fe³⁺ at temperatures between 673 and 773 K and of the Fe²⁺ ion at 773 K. The edge‐energy drift evident in the ED‐XAS data directly reflects the kinetics of reactions resulting in oxidation and/or reduction of the Fe²⁺ and Fe³⁺ ions in the aqueous solutions at high temperatures. The oxidation and reduction trends are found to be highly consistent, making reliable determinations of reaction kinetics possible.     

Silver whiskers and epitaxial layers on tungsten tips as fem specimens; Their growth and behaviour on annealing and oxidation

In order to investigate whether field-emission microscopy (FEM) can be applied to the examination of adsorption on low-melting metals, a study has been made of the preparation and the stabilization of silver surfaces that are suitable as field electron emitters. Single silver whiskers, showing negligibly distorted FEM patterns, could be grown at 873 K by in-situ deposition of silver vapour onto the apex of thermally cleaned blunt tungsten tips. Single-crystal silver layers could be grown at 296 K by the same technique on field-evaporated sharp tungsten tips. The nucleation and growth of the layers take place more uniformly on these crystallographically perfect surfaces than on thermally cleaned tips. At elevated temperatures (673 K) considerable diffusion of silver from the apex of the tip to the shank was noticed when the latter had been thoroughly cleaned by previous heating. The occurrence of this effect was avoided by applying the field-evaporation step in the tip-preparation procedure after the tip had been strongly oxidized ; thus, the oxidized tungsten bordering the cleaned apex acts as a silver diffusion barrier. The silver surfaces obtained have a high degree of cleanliness. Adsorbed oxygen can easily be removed by heating to 673 K ; hardly any blunting results from this treatment. However, when a silver layer has been strongly oxidized, complete field desorption of silver reveals oxidation also of the tungsten at the tungsten-silver interface. Application of positive voltages to a crystalline silver layer on a tungsten tip at 77 K in ultra-high vacuum deforms the layer extensively before actual field evaporation of silver is achieved.     

Effect of annealing treatments on the microwave electromagnetic properties of amorphous FeCuNbSiB microwires

The amorphous FeCuNbSiB microwires are fabricated by using the melt extraction method and annealed separately at temperatures T = 573, 673, 723 and 773K for 1h. The effect of annealing treatment on the microwave electromagnetic properties of FeCuNbSiB wires/wax composites has been investigated for the first time. It is found that in a frequency range of 0.5--4.0GHz, the complex permittivity, permeability, magnetic and electric loss tangents of FeCuNbSiB wires/wax composites are strongly dependent on the annealing temperature and frequency. For T = 573, 723 and 773K, two resonance peaks are found at frequency f = 1.2 and 3.3GHz. However, for T = 673K, only one resonance peak occurs at f = 3.3GHz. The resonance peak at f = 1.2GHz is believed to be due to the stress-induced anisotropy, while the resonance peak at f = 3.3GHz is attributed to the random anisotropy.     

Experimental study of the relationships between the spectral emissivity of brass and the temperature in the oxidizing environment

Effect of surface oxidization on the spectral emissivity of brass is studied over the temperature range from 800 to 1070 K at the wavelength of 1.5 μm. The temperature of brass surface is measured by averaging the two R-type platinum–rhodium thermocouples. The radiant energy emitted by the brass surface is received by an InGaAs photodiode detector. Two kinds of relationships between the spectral emissivity and the temperature are investigated in the oxidizing environment at the elevated temperature. One is the variation of spectral emissivity with the heating-duration time at the given temperature. The other is the variation of spectral emissivity with the temperature at the given heating-duration time. The interference effect of radiation coming from the brass surface and coming from the oxidization film is discussed when the oxidation film on the surface is grown. The resonant structures of spectral emissivity are observed during the whole heating period, in particular at the early stage of heating duration. The analytic formula of spectral emissivity versus the temperature is derived at the heating-duration time of 30, 60, 90, 120, 150, 180, 210, 240, 270 and 300 min, respectively. The conclusion is obtained that coefficients of analytic expressions between the spectral emissivity and the temperature are different from each other for the experimental results obtained at the different heating-duration time, though the polynomial functional form is suitable to fit all the measurements obtained in the present work.     

基于约束优化的多光谱辐射真温反演算法

多光谱辐射测温是通过测量待测物某点的多个光谱辐射强度信息,通过普朗克公式反演获得真实温度。但是,通过普朗克公式获得的多光谱辐射测温方程组,是欠定方程组,即N个方程,N+1个未知数(N个未知的光谱发射率ε_λi和1个待求真温T)。目前,多采用事先假设一组发射率模型(发射率-波长或发射率-温度模型),假设模型与实际情况如果相符,则反演结果能够满足要求,如果假设模型与实际情况不符,则反演结果误差很大。但是,发射率模型受温度、表面状态、波长等诸多因素影响,难以事先确定发射率模型。因此受未知光谱发射率的制约一直是多光谱辐射测温理论面临的主要障碍,能否在无需任何光谱发射率假设模型的情况下,实现真温和光谱发射率的直接反演一直是多光谱辐射测温理论研究的热点和难点。通过对参考温度模型的分析表明,多光谱辐射测温反演过程的实质是寻找一组光谱发射率,使得每个通道方程解得的真温都相同,如不相同则继续寻找合适的光谱发射率,直到每个通道解得的真温都相等。为此,提出将多光谱辐射测温参考温度模型的求解过程转换为约束优化问题,即在光谱发射率0≤ε_λi≤1的约束条件下,通过梯度投影算法不断寻找光谱发射率,带入多光谱辐射测温参考温度模型方程组后,计算温度反演值的方差,直到每个光谱通道方程获得的温度值应该近似相等,此时各个光谱通道的温度反演值方差最小,这样就把多光谱辐射真温和发射率的反演问题转换为约束优化问题。约束优化算法是解决这一类问题的主要方法,但为了满足Ax≥b的约束条件,将0≤ε_λi≤1分解为ε_λi≥0和-ε_λi≥-1的两个约束条件,从而满足了约束优化问题Ax≥b的约束条件。这样就可以通过约束优化算法在无需任何光谱发射率假设模型的条件下,直接求解真温和光谱发射率。实验采用六种不同光谱发射率分布模式(随波长递增、递减、凸波动、凹波动、“M”型波动、“W”型波动)的材料为研究对象,以验证新算法对不同材料光谱发射率分布反演的适应性,利用Matlab的minRosen函数,选择光谱发射率的初始值均为0.5(取中间值,提高计算效率)。针对六种不同光谱发射率模型的仿真结果表明,新算法无需任何有关发射率的先验知识,对不同发射率模型反演结果均表现较好,在真温1 800 K的情况下,绝对误差均小于20 K,相对误差均小于1.2%,新算法具有无需考虑任何光谱发射率先验知识、反演精度较高及适合于各种发射率模型等优点,进一步完善了多光谱辐射测温理论,在高温测量领域具有良好的应用前景。     

Surface photovoltage properties and photocatalytic activities of nanocrystalline CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> particles with porous superstructure fabricated by a modified chemical coprecipitation method

In this study, nanocrystalline CoFe₂O₄ particles with porous timber-like superstructure were synthesized by a modified chemical co-precipitation route with calcination temperatures of 573, 673, 773, 873, and 973 K, respectively. The structural properties of the samples were systematically investigated by X-ray powder diffraction, scanning electronic microscopy, energy-dispersive X-ray spectra, UV–Vis diffuse reflectance spectroscopy, and Fourier transform infrared spectroscopy techniques. The photo-induced charge separation in the samples was demonstrated by surface photovoltage (SPV) measurement. The photocatalytic performances of the CoFe₂O₄ samples were comparatively studied by the degradation of 4-chlorophenol under Xe lamp irradiation. The results indicated that the sample calcined at 673 K exhibited the highest photocatalytic efficiency among the five samples.