1：Experimental Design and Method Selection:

The study involved measuring the spectral emissivity of nickel and nickel oxide using a high-accuracy radiometer in controlled atmospheres (argon and air). The modified blacksur method was employed to avoid spurious reflections, and the radiometer was calibrated with a high-temperature blackbody and high-emissivity coating. Temperature was measured using thermocouples for Ni and the Christiansen wavelength method for NiO.

2：Sample Selection and Data Sources:

A high-purity (

3：999%) nickel sputtering target with a diameter of 50 mm and thickness of 2 mm was used. It was mechanically polished to achieve a specular surface with low roughness (Ra = 03 μm, Rq = 04 μm). The oxidized sample was characterized by X-ray diffraction, optical microscopy, and scanning electron microscopy. List of Experimental Equipment and Materials:

Equipment included a mechanical profilometer (Mitutoyo SJ201), X-ray diffractometer (X'Pert-Pro), optical microscope (Leica DM RXA), scanning electron microscope (FEG JEOL JSM-7000F), high-accuracy HAIRL radiometer, integrating sphere (Bruker A 562-G with Infragold coating), K-type thermocouples, and materials such as high-purity nickel, alumina powder for polishing, and argon gas.

4：Experimental Procedures and Operational Workflow:

The sample was polished and measured in argon from 200 to 800°C to establish baseline emissivity. It was then oxidized isothermally at 730°C in air for 33 days, with emissivity measured dynamically. After oxidation, the NiO layer was characterized, and emissivity of NiO was measured from below its Néel temperature to 850°C in argon. Data were collected and analyzed for spectral and total normal emissivity.

5：Data Analysis Methods:

Spectral emissivity data were integrated numerically with Planck function weighting to obtain total normal emissivity. Uncertainties were estimated, and results were compared with literature data. X-ray diffraction and microscopy were used for material characterization.