Directional spectral emissivity measurement approach in a broad-spectrum at low temperatures: Device and methodology study.

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]