Modified two-temperature calibration method for emissivity measurements at high temperatures

Abstract

In this study, an experimental apparatus for normal spectral emissivity measurements in the temperature range from 673 to 1473 K and spectral range from 2 to 25 μm was constructed. To eliminate disturbances caused by the drift of the background radiation and the zero-point deviation of the FTIR spectrometer at high temperatures, an improved algorithm based on the modified two-temperature calibration method for enhancing the measurement accuracy of emissivity was proposed. The spectral response function was computed with the modified two-temperature calibration method. The excellent linearity of detector and the good stability of the spectral response function were verified. The necessity of the compensation offset for the drift of the background radiation and the zero-point deviation of the FTIR spectrometer were systematically analyzed. The potential reference material (silicon carbide) was used to validate the reliability of the emissivity results obtained by the experimental apparatus. The excellent agreements with the literature data around the Christiansen point demonstrate that the improved algorithm can provide reliable emissivity measurements. The calculated combined uncertainty of the spectral emissivity for the silicon carbide sample at 1473 K is estimated to be less than 2.6% except for the spectral bands of atmospheric absorption.