25 November 1992 Study of the optical properties of nickel-pigmented anodized aluminum oxide on aluminum
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The optical selectivity of nickel pigmented anodized aluminum with different surface roughness of the aluminum substrate has been compared. The hemispherical emittance at 100 degree(s)C has been measured and normal emittance calculated from spectral reflectance for aluminum oxide films of different thickness, pigmented and unpigmented. The discrepancy between normal and hemispherical emittance was large especially for unpigmented aluminum oxide. One reason for this is found from non normal reflectance measurements in the infrared wavelength range. The absorption at the wavelengths of the optical longitudinal phonon of aluminum oxide is strong for oblique incidence and, therefore, enhances the thermal hemispherical emittance at this temperature. We, therefore, stress the importance of measuring the hemispherical emittance when characterizing a solar absorber surface of this material.
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Ewa Wackelgard, "Study of the optical properties of nickel-pigmented anodized aluminum oxide on aluminum", Proc. SPIE 1727, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XI: Selective Materials, Concentrators and Reflectors, Transparent Insulation and Superwindows, (25 November 1992); doi: 10.1117/12.130503; https://doi.org/10.1117/12.130503

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