Normal spectral emissivity characteristics of roughened cobalt and improved emissivity model based on Agababov roughness function

Abstract

The normal spectral emissivity of 16 cobalt samples were measured under an argon protection environment. The influence of surface roughness (16 different roughnesses), temperature (473–973 K), and wavelength (3–20 μm) on the normal emissivity was investigated. The normal spectral emissivity of cobalt increased with the increase of surface roughness, which was particularly evident at shorter wavelengths. The normal spectral emissivity of cobalt increased with an increase in temperature below 11.5 μm, but decreased above 11.5 μm. With increased wavelength, the normal spectral emissivity decreased monotonically and then overlapped at 19 μm. On the basis of the Agababov roughness function, the height and length of contour units were replaced by the average deviation of the contour and the unimodal average spacing. The normal spectral emissivity of samples was calculated using the normal spectral emissivity of a relatively smooth sample as a reference value. However, there was a significant difference between the calculation results and experimental values. Based on this, an improved model was proposed for the cobalt roughness function. Using this model, it is possible to deduce the normal spectral emissivity of cobalt samples with different roughnesses.