Spectral selectivity of composite enamel coatings on 321 stainless steel

Composite porcelain-enamel coatings consisting of spinell-type transition-metal-oxide pigments embedded in a borosilicate-glass matrix were deposited on 321 stainless steel using screen-printing techniques and characterized using total reflectance over the spectral range of 200 nm to 25 mu m. The composite coatings exhibited moderate spectral selectivity and excellent thermal stability at 450 degrees C. Solar absorptance (alpha) ranged from 0.82 to 0.90 and calculated thermal emittance at 500 degrees C (epsilon) ranged from 0.46 to 0.79. Both depended on coating thickness and pigment volume concentrations. As an example, the highest solar selectivity was measured in a 0.9 mu m coating with alpha and epsilon (500 degrees C) being 0.82 and 0.46, respectively. (C) 2009 Elsevier B.V. All rights reserved.