SPECTRAL-DIRECTIONAL EMITTANCE OF OXIDIZED COPPER

The surface emittance of fully oxidized copper is experimentally deter mined as functions of wavelength between 2-10 mu m, the direction betw een the normal and grazing angles, and the temperature between 400-700 degrees C, Clean copper surfaces, heated and exposed to air, begin to oxidize immediately, After a sufficient heating time, the oxide layer becomes thick enough that the radiative surface properties are those of copper oxide, independent of the properties of the underlying coppe r, The experimental apparatus measures emitted flux over discrete band s of wavelength and solid angles centered about a direction, and is ca librated with a radiating cavity (hohlraum). Emittance results are pre sented in both spectral and polar form, and also integrated to obtain the spectral-hemispherical emittance of fully oxidized copper By assum ing copper oxide to be a dielectric, the real part of the index of ref raction is reduced from emittance data, This index is found to decreas e with wavelength and temperature, This technique of spectral-directio nal emittance determination by direct emission measurement, together w ith index of diffraction identification (if found to fit Fresnel or ot her relations), should prove useful for other engineering materials as well as copper oxide.