High temperature, spectral-directional emittance of high purity nickel oxidized in air

Spectral-directional emittance measurements for 99.99% nickel, thermally oxidized in air, were performed at temperatures of 673, 773, and 873 K using an apparatus comprised of a Fourier transform infrared (FTIR) spectrometer, a blackbody radiating cavity (hohlraum), and a sample holder which allows directional measurements. The data cover the spectral range between 2 and 20 lm, and the directional range from a surface normal to 72 polar angle. The Ni sample had a nominal surface roughness of 4.1 lm and was heated for 1 h at the measurement temperatures prior to emission measurements. X-ray diffraction and EDS analyses were performed in order to characterize the sample surface. It was found that the normal emittance of oxidized nickel increases with temperature for the temperature range considered. Directional emittance shows slightly departure from pure metal behavior.