Objective To obtain the infrared radiation characteristics of the high-emissivity blackbody coating in wide temperature range, the spectral emissivity of two blackbody coatings which are applicable in various temperature scenarios were measured based on two devices. The temperature measurement range of JSC-3 coating spans from room temperature to 1 000 ℃, while the temperature measurement range of GR coating extends from room temperature to 150 ℃. The relationship between the spectral emissivity and the temperature of the JSC-3 and GR coating was shown respectively, and the investigation delved into variations in directional spectral emissivity across different angles. Experimental findings indicated that the spectral emissivity of JSC-3 and GR coatings at 8-14 μm exceeds 0.96 and 0.97, respectively. The spectral emissivity of the two coatings remains stable in the wide temperature region, and the variation is separately less than 0.01 and 0.003. Both coatings demonstrate excellent directional spectral emissivity consistency within 0°-30°, exhibiting minimal variations of less than 0.005. Finally, the spectral emissivity of JSC-3 and GR coatings in the range of 3 μm to 14 μm at room temperature was measured by integrating sphere reflectance method, which successfully obtained comprehensive spectral emissivity data coverage across a wide temperature range and broad wavelength band for two coatings.

Methods Based on the different emissivity measuring devices, the spectral emissivity characteristics of two blackbody coatings in wide temperature region were studied (Fig.1-2). The variation of the spectral emissivity of the coating with temperature and angle was discussed, and the difference of the spectral emissivity at various temperature and angles of two blackbody coatings was shown concretely.

Results and Discussions The spectral emissivity of JSC-3 and GR coating is respectively better than 0.96 and 0.97 (Fig.5, Fig.8), The variation of the spectral emissivity of two coatings is separately less than 0.01 and 0.005. There is a slight decrease within 0.005 in directional spectral emissivity for both JSC-3 and GR coatings as angle increases within 30° (Fig.6, Fig.9), and the maximum reduction of JSC-3 is 0.05 in the range of 0°-60° (Fig.6). The spectral emissivity of the GR coating exhibits a higher sensitivity to angle variations at elevated temperatures (Fig.9). The continuous spectral emissivity data of the two coatings in the range of 3 μm to 14 μm were obtained using the integrating sphere reflection method at room temperature, enabling broad coverage of their spectral emissivity data across a wide temperature range.

Conclusions Two blackbody coatings have excellent spectral emissivity performance at the operating temperature, and the average spectral emissivity of JSC-3 and GR coatings at 8-14 μm is better than 0.96 and 0.97, respectively (Fig.5, Fig.8). The difference of average spectral emissivity of JSC-3 from room temperature to1000 ℃ is less than 0.01, while the difference of GR from room temperature to 150 ℃ is less than 0.003. The temperature stability exhibited by all of them was commendable. When the angles are ranging from 0° to 30°, there is a slight decrease within 0.005 in directional spectral emissivity for both JSC-3 and GR coatings as angle increases, the spectral emissivity in the direction of 30° remains consistent. The continuous spectral emissivity data of the two coatings were acquired at room temperature in range of 3-14 μm measured by integrating sphere reflectance method, and the spectral emissivity data coverage of the two coatings is achieved across a wide temperature range and a broad spectrum. The experimental results provide robust evidence supporting the simulation and design of blackbodies across various temperature ranges and spectral bands.