Measurement of normal spectral emissivity of materials at high temperature

In order to meet the high-precision measurement requirements of spectral emissivity of high-temperature material coating, including stealthy materials, thermal protection materials, heat insulating coat and so on, the measuring methods for normal spectral emissivity of materials at 1 273 K~3 100 K was explored. A measurement model of normal spectral emissivity of materials was established based on the emissivity definition. On this basis, the measurement facility of normal spectral emissivity of materials was built, and the wavelength range was 0.7 μm to 12 μm. In order to overcome the technical difficulties associated with cavity effect when the sample was heated with high precision in the measuring device, a sample heating furnace with a movable graphite crucible was developed, and the good experimental results were obtained. The normal spectral emissivity of two samples (SiC and low emissivity coating) was measured by this facility. The results show that the normal spectral emissivity of two samples reduces with the increase of wavelengths and rises with the increase of temperature. Finally, the measurement uncertainty of normal spectral emissivity of materials at high temperature was analyzed, and the relative expanded uncertainty is 3.6%.