Fig. 1. The schematic of spectral emissivity measuring setup

Fig. 2. The spectral emissivity curves of copper-nickel alloy during oxidation process at different temperatures
(a): 673 K; (b): 773 K; (c): 873 K; (d): 973 K

Fig. 3. The effect of temperature on the spectral emissivity of copper-nickel alloy at different heating time
(a): Nitrogen environment; (b): 10 min; (c): 20 min; (d): 30 min; (e): 40 min; (f): 50 min; (g): 60 min

Fig. 4. Surface morphologies of copper-nickel alloy after oxidation for 60 min at different temperatures
(a): 673 K; (b): 773 K; (c): 873 K; (d): 973 K

Fig. 5. X-ray diffraction pattern of copper-nickel alloy after oxidation for 1 h at different temperatures
a: 673 K; b: 773 K; c: 873 K; d: 973 K

Fig. 6. The effect of heating time on the spectral emissivity of copper-nickel alloy at different temperatures
(a): 673 K; (b): 773 K; (c): 873 K; (d): 973 K

Fig. 7. Reflection and refraction model of substrate radiation at the air/oxidation film interface