Probing high temperature thermal emissive properties of energy materials and coatings with emission spectroscopy augmented by in situ reflection

Abstract A robust non-contact methodology for the in situ determination of both the temperature and the spectral emissivity of a surface spot is presented. It is applicable to all materials exhibiting an opacity region. Tests performed on different materials demonstrated the high level of accuracy of the method when it is applied to the temperature measurement of smooth surfaces. The accuracy is reduced when probing rough surfaces, but it was shown that the relative uncertainty for temperature was still better than one percent for materials whose roughness characteristic size is less than the wavelength used to perform the temperature determination. Analytical formulas to derive upper limits of the combined standard uncertainties are presented. For rough surfaces, the association with a microfacet model describing the light scattering by the sample surface provides a method to evaluate the optimum spectral range for the determination of the temperature.