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The tungsten-copper alloy is commonly used for the electrical contact in high current vacuum switch, where precise temperature monitoring of the contact is crucial for ensuring stable operation of the switch by radiation thermometry. However, accurate emissivity data of this alloy is necessary when using radiation thermometry for temperature measurement. Thus, the directional spectral emissivity of tungsten-copper alloy is investigated within the temperature range of 400–700 ℃ under vacuum in this work. The hemispherical total emissivity is calculated by numerically integrating the directional spectral emissivity. Experimental results found this tungsten-copper alloy agrees with the theoretical prediction of the electromagnetic theory, that is, the emissivity increases with increasing temperature, and decreases with increasing wavelength. A convergence phenomenon of spectral emissivity occurs when the polar angle exceeds approximately 50°. This means that the normal wavelength dependence undergoes a shift at high polar angles, which is typical behavior of metallic emissivity. Additionally, the effects of thermal cycle, surface roughness, and chemical composition on emissivity are analyzed in detail. Surface stress relaxation process results in a significant decrease in emissivity. Emissivity increases as the surface roughness and tungsten composition of alloy increases. However, the effects of surface roughness and chemical composition on emissivity gradually disappear at long wavelengths and high polar angles. [ABSTRACT FROM AUTHOR]

A new apparatus simultaneously and rapidly measuring the sample radiation and the blackbody radiation by one detector without moving any experimental component is designed to measure the directional spectral emissivity of solid samples in a controlled environment. The effect of multiple reflections in the sample chamber on the measurement result is evaluated. The temperature distribution of the sample surface is measured by using a thermal imager. In order to validate the experimental apparatus, the directional spectral emissivity of silicon is measured in a nitrogen environment and that of iron is measured in vacuum, and the normal spectral emissivity of pure copper is measured during the oxidation process. Good agreement between the measured results and the reported data proves the reliability of the designed apparatus. The expanded uncertainty of the measurement system is estimated to be less than 5.3% when the emission angle is 86°. [ABSTRACT FROM AUTHOR]

Accurate spectral emissivity is indispensable for driving the development of radiative cooling and radiative thermal camouflage toward low temperatures. Nevertheless, the measurement of low-temperature spectral emissivity is difficult because the radiation signal at low temperatures is very weak, especially in the mid-and far-infrared wavebands. In order to improve the measurement capability of spectral emissivity at low temperatures, an experimental apparatus for accurately measuring the directional spectral emissivity of solid materials is developed, covering the spectral range from 5 to 100 μm and the temperature range from 213 to 423 K. In our experiment, the multi-temperature calibration method is used to exactly calibrate the background radiation signal in the mid-infrared waveband, and the radiation modulation method is used to extract the far-infrared target signal accurately. The reliability of experimental apparatus is evaluated by measuring the directional spectral emissivity of silicon carbide. [ABSTRACT FROM AUTHOR]

• Emissivity of Cu 2 (OH) 2 CO 3 in the thermal decomposition is studied. • The Cu 2 (OH) 2 CO 3 exists a critical state prior to its decomposition (453–493 K). • Microscopic discussion on the decomposition process of Cu 2 (OH) 2 CO 3 by surface emissivity. The spectral emissivity of basic copper carbonate (Cu 2 (OH) 2 CO 3) was measured by a Fourier Transform Infrared (FTIR) spectrometer in the wavelength range of 5–20 μm during the heating process, and the integral emissivity was calculated to study the effect of decomposition on emissivity. The surface composition of the samples was investigated by X-ray diffraction. Based on the spectral emissivity data and the measurement of X-ray diffraction, it can be concluded that Cu 2 (OH) 2 CO 3 starts breaking down at 513 K and exists a critical state at 453–493 K. This state would cause a drop in spectral emissivity value, and enhance the oscillation intensity of spectral emissivity in 5–8 μm and spectral absorption at 14.95 μm. Above 513 K, heating time and temperature have great influences on emissivity. The emissivity changes more obvious as the increasing temperature. The emissivity of Cu 2 (OH) 2 CO 3 gradually tends to be stable with heating time when the decomposition process is completed. [ABSTRACT FROM AUTHOR]

A new method was proposed to accurately predict the emissivity of rough surface polished by sandpaper. The complex rough surface was numerically reestablished based on the surface characteristic parameters extracted from the statistical data of 3D optical profiler measurement. Directional spectral emissivity of the established surface was simulated by the finite element method in the wavelength range of 2–20 µm and in the emission angle range of 0–80°. The influence of roughness on spectral emissivity was carefully studied. The calculated emissivity was compared to the data measured by a self-made emissivity measurement apparatus. The predicted results are in good agreement with the experimental data, which well proves the reliability of the proposed method. • A new method was proposed to accurately predict the directional spectral emissivity of sandpaper-polished rough surface. • The complex rough surface was reestablished based on the characteristic parameters extraction of optical profile. • The emissivity prediction is rigorous for taking the complex scattering, shadowing and diffraction effects into account. [ABSTRACT FROM AUTHOR]

• A correction method of equivalent temperature for the non-isothermal measurement area was proposed. • The measurement accuracy of directional spectral emissivity was significantly improved by surface equivalent temperature correction. • The relative uncertainty is systematically estimated to be less than 1.74% at the emission angle 80°. The increase of spectral emissivity measurement error at large emission zenith angle is mainly attributed to the surface temperature deviation. To improve the measurement accuracy, a correction method of equivalent temperature for the non-isothermal measurement area was proposed. An experimental apparatus was established to accurately measure the spectral emissivity in the angular range of 0°-80°. The spectral response function of FTIR spectrometer was calibrated with the multi-temperature method. The relative uncertainty in emissivity caused by the surface temperature deviation was analyzed. A high-purity silicon carbide sample was used to verify the reliability of emissivity measurement results. Results show that the maximum deviation between the corrected equivalent temperature and the set temperature would exceed 3 ℃ at 550 ℃. The excellent agreement between the results and the reported data illustrates the reliability of the emissivity measurement. The comparison of relative uncertainty proves that equivalent temperature correction for the non-isothermal measurement area is significant to improve the measurement accuracy of directional spectral emissivity. The relative emissivity uncertainty is estimated to be less than 1.74% at the emission zenith angle 80°. [ABSTRACT FROM AUTHOR]

The infrared normal spectral emissivity of an oxidized Ti–6Al–4V alloy has been measured during a thermal oxidation process. It gradually increased with oxidation time below 873 K, and strong oscillation was observed above 923 K. To explore the possible reasons for emissivity variation under different temperatures and oxidation time, the changes of surface composition and roughness were investigated before and after oxidation by X-ray diffraction (XRD) and roughness tester. The surface oxide film thickness has been estimated by using the theory of radiative effects of films and the actual value of thickness has been measured utilizing spectroscopic ellipsometry (SE) and scanning electron microscopy (SEM), respectively. The measurement results were in good agreement with the estimated values. It is found that the interference effect of oxide film could be responsible for the oscillatory behavior in spectral emissivity. The thickness values indicate that the oxide film growth follows parabolic law and that the growth rate increases rapidly above 923 K. [ABSTRACT FROM AUTHOR]

The infrared normal spectral emissivity of the oxidized molybdenum was measured during thermal oxidation process, and the integral emissivity was calculated from the data of spectral emissivity. It is found that the surface oxidation has a remarkable effect on the spectral emissivity of molybdenum, and the spectral emissivity curves become more fluctuant with the increase in oxidation time. The integral emissivity grows exponentially with the oxidation time at 773 K, remains almost constant at 823 K, and fluctuates at 873 and 923 K. The X-ray fluorescence spectrometer, the X-ray diffraction, and the scanning electron microscopy were employed to analyze the changes in surface composition and surface morphology. The results show that the most probable reason for the variation of integral emissivity is the change in surface roughness caused by the variation in the size and shape of oxide particle on specimen surface. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new experimental apparatus was established for DPSE measurement. • The accuracy was improved by eliminating the background radiation. • The relative uncertainty was systematically estimated to be less than 4.1%. A new directional polarized spectral emissivity measurement apparatus with the wavelength range of 4–20 μm was established to promote the development of thermal radiation transfer and polarization engineering. The measurement accuracy was improved by eliminating the background radiation with a high emissive thermostatic shutter and precisely determining the sample surface temperature. An accurate expression for directional polarized spectral emissivity was obtained taking into account the multiple reflection between the sample and the chamber. The linearity of spectral response was calibrated respectively in parallel and perpendicular polarized directions. The directional polarized spectral emissivity of a high-purity SiC sample was measured in a controlled environment to validate the capability of the apparatus. The excellent agreement between the measurement result and the literature data proved the reliability of the experiment apparatus and the measurement method. The measurement uncertainty was evaluated for each experiment, and the relative uncertainty was estimated to be less than 4.1%. [ABSTRACT FROM AUTHOR]

The electromagnetic cold crucible levitation heating technology has tremendous potential in the spectral emissivity measurement of molten metal for its high melting temperature and no contamination. In this work, we designed a dedicated cold crucible with a hemispherical bottom to establish the spectral emissivity measurement apparatus at high temperature. The effects of different numbers of segments, slit width, wall thickness and height-diameter ratio on the magnetic permeability of crucible were studied by the finite element method. The results indicate that increasing the number of crucible segments and the slit width can effectively improve the magnetic permeability of cold crucible, while increasing the wall thickness and the ratio of height to diameter will reduce its magnetic permeability. Based on the simulation result, the cold crucible with optimal parameters was made and used for studying the spectral emissivity of molten metal. The spectral emissivity of iron, cobalt and nickel was measured successively to prove the availability of cold crucible in emissivity measurement. The results agree well with the literature data, and the combined uncertainty of the molten iron is 2%. This work demonstrates that electromagnetic cold crucibles have a promising prospect in emissivity measurement of molten metal. [ABSTRACT FROM AUTHOR]

In the field of energy-intensive industrial processes, investigating the spectral emissivity of molten metals is crucial for improving energy utilization and efficiency. However, previous research efforts have not fully explored the measurement of melting emissivity. This study presents an effective method for measuring the spectral emissivity of molten metals. A new experimental apparatus was developed to measure the melting spectral emissivity within a range of 2–8 μm and temperatures ranging from 873 K to 2373 K. The sample was rapidly melted using a specially designed electromagnetic cold crucible, while its spectral radiance was detected using a Fourier transform infrared (FTIR) spectrometer. To enhance energy utilization rate, numerical simulation of the cold crucible improved induction heating performance. Additionally, calculating radiation within the cylindrical chamber enhanced measurement accuracy of emissivity. To validate the reliability of this apparatus, normal spectral emissivity measurements were conducted on liquid nickel. The results demonstrate that comprehensive uncertainty associated with liquid nickel's spectral emissivity does not exceed 1.82 %. Furthermore, verification based on the Drude-Roberts model confirms normal spectral emissivity values for liquid nickel as well. • Designed circular crucible and device for melting emissivity measurement. • Numerical model optimized nickel melting, enhancing energy efficiency. • Analyzed radiation cavity for improved emissivity accuracy. • First measurement of nickel's 2–8 μm emissivity, analyzing unique properties. • Device shows clear advantages in measurement uncertainty evaluation. [ABSTRACT FROM AUTHOR]

• A new experimental device for measuring the polarized spectral emissivity in a controlled environment is presented. • The effect of radiation of the spherical chamber is calculated and discussed in detail. • Polarized emissivities of silicon wafer, silicon carbide, and pure iron at 1.5 μm are measured. A new experimental apparatus is designed for polarized spectral emissivity measurements of solid material in a controlled environment such as vacuum, oxidization, reducing atmosphere, etc. The sample heater is placed inside a stainless steel chamber, which allows to heat the sample up to 1073 K. The sample heater can be rotated 180° with an electric rotating platform. The stainless steel chamber is equipped with three flow controllable intake valves to simulate different gas atmosphere. A polarization beam splitting cube is placed in front of the window, and the radiance emitted from the specimen surface is divided into P and S polarized radiance. The polarized radiance can be measured from 1200 to 1600 nm by an indium gallium arsenic detector. The effect of radiation of the spherical chamber is calculated and discussed in detail. In order to validate the capability of the apparatus, the polarized spectral emissivity of silicon wafer at 1.5 μm is measured firstly. The result shows an excellent fit with the simulation. Then, the pure iron and silicon carbide is measured respectively in an atmosphere and vacuum environment. The experimental results verify the functionality and repeatability of the apparatus. The uncertainty assessment shows that the relative combined uncertainty of polarized spectral emissivity is no more than 1.92% for the spectral range considered. [ABSTRACT FROM AUTHOR]

• The normal spectral emissivity of molten Fe-Ni alloys were measured in the wavelength range of 1000–1600 nm. • The effect of composition of the nickel was measured and discussed in detail. • Between 1400 nm and 1600 nm, the emissivities of same ingredient Fe-Ni alloy almost overlap. The spectral emissivity of molten Fe-Ni alloys is especially critical to analysis the performance and quality of alloy. The near-infrared normal spectral emissivity of molten Fe-Ni alloys was measured at 1000–1600 nm in the temperature range of 1690–1845 K by a self-built measurement apparatus using the electromagnetic heating technology. The measurement apparatus mainly consists of the electromagnetic heating furnace, blackbody, optical fiber spectrometer and colorimetric thermometer. The dependence of near-infrared normal spectral emissivity of Fe-Ni alloys (Ni, Fe10Ni90, Fe30Ni70, Fe50Ni50, Fe70Ni30, Fe90Ni10 and Fe) on wavelength, temperature and composition were systematically investigated. The results show that the emissivity of Fe70Ni30 is higher in the iron-rich area, while the emissivity of Fe30Ni70 is the lowest in the nickel-rich area. Comparison of the measured and simulated results show that the emissivity of molten Fe-Ni alloys is reliable. The emissivity of Fe-Ni alloys provides reliable data for the research of alloys properties. [ABSTRACT FROM AUTHOR]