Emissivity Measurement Device Based On Integrating Sphere And Emissivity Of Pure Copper In Thermal Oxidation Process

Emissivity is a basic parameter for characterizing the thermal physical properties of materials,which is a relative parameter.It is an important indicator to measure the ability of an object to emit thermal infrared electromagnetic waves.For researchers,the emissivity is studied mainly due to its applications in the technical and scientific temperature measurement by pyrometers;radiation heat transfer and estimation of optical constants;heating efficiency;photovoltaic applications,etc.In addition,it has important scientific research value and broad application prospects in aerospace,military,national defense and industrial and agricultural production.For example,it is necessary to know the emissivity data when considering the heat transfer of heat radiation,especially in high temperature and vacuum environments,and measuring the temperature of the target by a radiometer(pyrometer).Therefore,the emissivity is a keyMany factors have an effect on the spectral emissivity of material surface,such as the temperature of sample surface,the wavelengths measured,the direction and angle measured,the chemical composition and microstructure of the sample surface,as well as the roughness and oxidation of the material surface.The emissivity is not an intrinsic parameter of an object,which is a relatively unmeasurable physical quantity and changes with the external environment and the state of the object itself.With the continuous improvement of infrared radiation theory and the development of science and technology,researchers in various countries have carried out some deep research on emissivity,and proposed many methods and techniques for measuring emissivity.At the same time,they have developed various experiments and obtained a lot of emissivity data of various materials.In the near infrared and low temperature due to weak signal of surface radiation,it is poor for the accuracy to use the direct method to measure the spectral emissivity of a material,therefore,it is usually measured by indirect method(the reflection method).Firstly,the spectral reflectance of the sample is measured,according to the law of conservation of energy and Kirchhoff,the spectral emissivity of the material surface can be calculated at the same wavelength.In the far-infrared,the energy contrast method is usually used to measure the emissivity.With the support of the National Natural Science Foundation of China,using the existing measuring device of the laboratory,a new device was built to measure hemispherical emissivity in the near infrared.In addition,the spectral emissivity of pure copper was systematically studied using the existing energy contrast measuring device in the laboratory.The main research of this paper is as follows:1.In this paper,based on the integrating sphere and the reflection method measurement technology,the devices of measuring the hemispherical spectral emissivity of an object is designed.It is planned to measure the emissivity in the wavelength range of 0.9-1.7?m and the temperature at room temperature.The device consists of three parts: the radiation source,the integrating sphere and the signal acquisition system.The radiation source uses an EQ source,and the integrating sphere is used to collect the reflected radiation from the sample.The spectral spectrometer receives the signal from the integrating sphere,which is processed with a software system in the computer to obtain the data.2.The normal spectral emissivity of oxidized copper is measured in the wavelength range of 3–20?m at four temperatures(573K,673 K,773K,873K)and different heating times(10min,20 min,30min,40 min,50min,60min)during thermal oxidation.The influence of wavelength,temperature,and heating time on the normal spectral emissivity of pure copper during the oxidation process is analyzed.It was found that the spectral emissivity at 12?m,15?m,and 17?m remained constant for different heating times at 673 K.At the other three temperatures,the normal spectral emissivity demonstrated only a marginal increase with the increase of the heating time at the same wavelength.The oscillation of normal spectral emissivity of pure copper during oxidation was also found.At shorter wavelengths,the theory of radiation interference between the oxide layer and substrate is introduced to explain the spectral emissivity oscillation.In the long wavelength band,the lattice oscillation of the oxide film is used to explain the spectral emissivity oscillation.