Research On The Measuring Device Of Material Polarized Spectral Emissivity

Spectral emissivity is an important thermophysical parameter,which characterizes the ability of real material surface to emit electromagnetic radiation.The higher the spectral emissivity of the material,the stronger the external radiation capacity of the material.This parameter is necessary for many industrial and technical applications related to heat flow,heating efficiency,radiometric thermometry,etc.With the rapid development of infrared technology in recent years,the need for accurate spectral emissivity measurement is becoming more and more urgent.Generally speaking,emissivity can be divided into the following categories: hemispheric spectral emissivity,hemispheric total emissivity,directional spectral emissivity,directional total emissivity and polarized emissivity,etc.Most of the emissivity measuring equipment is to measure the normal spectral emissivity of the material surface.There are few reports about the measuring device of polarized spectral emissivity.Polarized spectral emissivity is defined as the ratio of S or P polarized radiation to blackbody radiation at the same temperature,wavelength and direction of polarization.Compared with the unpolarized spectral emissivity,the polarized spectral emissivity of materials can exhibit some special properties.Combining the special property of polarization emissivity with radiation temperature measurement method,a new measurement method of radiation temperature measurement can be explored,so as to improve the measurement precision and stronger adaptability of radiation temperature measurement technology.At the same time,the law between the normal spectral emissivity and polarized spectral emissivity of materials can be further explored,which is conducive to a more comprehensive understanding and grasp of the nature and law of the infrared radiation of materials.In order to meet the needs of more experiments,it is urgent to develop a set of measurement equipment to measure the emissivity of polarized spectral emissivity.Therefore,with the support of the National Natural Science Foundation of China and the Youth Foundation of China,this paper established a set of experimental equipment that can measure the polarized spectral emissivity at different temperatures and angles in a controlled environment.The main work of this paper is as follows:1.In this paper,an experimental setup for polarized spectral emissivity measurements in a controlled environment is built based on the energy contrast method.The measurement system includes an atmosphere controlled sample heating system,a blackbody system,a polarized optical system and a signal detection system.The sample heating system with controllable atmosphere and the blackbody are the radiation sources of the measurement system.The polarized optical system consists of an optical filter,a polarization beamsplitting cube,an optical chopper,a fiber probe and a Y-fiber optical transmission system.The signal detection system includes indium gallium arsenic detector and lock-in amplifier.2.This paper details the design of an atmosphere-controlled sample chamber with three flow-controlled inlet valves that protect the sample for polarization spectroscopy emissivity measurements in vacuum,oxidizing,and reducing atmospheres.The heater can be rotated independently by the rotary table attached below and the angle modulation can be controlled within 0.1°.3.Several important aspects of the polarization spectroscopy emissivity measurement device,including sample heater temperature uniformity and blackbody temperature uniformity,were tested and calibrated to ensure that the measurement device can accurately measure the sample surface and blackbody axial temperatures and stabilize the sample surface and blackbody temperatures within a range of 0.1K.Simulations and calculations of hemispherical cavity radiation were performed,showing that a constant temperature,high emissivity hemispherical cavity has a small effect on sample spectral emissivity measurements.When the sample surface temperature is above 1000 K,the radiation from the hemispherical cavity to the sample surface is negligible.4.To verify the reliability of the measurement device,the polarized spectral emissivity of a single-sided polished silicon wafer at 1500 nm was first measured,and the measurement results were in good agreement with the simulation results.The polarized and directional spectral emissivity of pure iron were measured under vacuum and oxidation conditions.The results show that oxidation can increase the polarized and directional spectral emissivity of pure iron obviously,and the results are in good agreement with the foreign data.In addition,the polarized spectral emissivity of silicon carbide,corundum,coating and other materials were also measured,which proved that the reliability and stability of the experimental equipment is good.The uncertainty of the measurement device was evaluated and the combined uncertainty of the polarized spectral emissivity did not exceed 1.92% in the considered spectral range.