Thermal Radiation Phenomena of Surfaces of Chromium and Palladium in a High-Temperature Environment

For the purpose of thermal engineering applications, thermal radiation phenomena of surfaces of chromium and palladium in a high-temperature air-oxidation process on the basis of simultaneous measurements of spectra of normal incidence hemispherical reflectance and normal emittance in the near-ultraviolet through infrared region are investigated. As the results of the spectral measurements, clear radiation interference is observed even in the spectra of the hemispherical reflectance of a rough-finished chromium surface in the oxidation process as well as in the spectra of the normal reflectance of a specular-finished surface. The relation between the chemical reactions of oxidation and reduction of a palladium surface in the 1000 K to 1100 K range and the radiation characteristics are analyzed based on the temperature hysteresis of radiation spectra and the reaction rates of oxidation and reduction. A switching function of radiation characteristics of palladium accompanied by the oxidation and reduction reactions is suggested to be applicable for engineering applications.