Influence of Microstructure and Composition on Optical Properties of Plasma Sprayed Al/Al 2 O 3 Cermets

Normal hemispherical Spectral refleCtances of plasma sprayed Al2O3/Al cermets -Were Acquired from visible to infrared' wavelengths for several metal concentrations. Since optical respbriSe of these coatings is highly dependent on volumetric and/or surface light scattering, special attention was paid to characterization of the composition, microstructure, and surface roughness of suck coatings. The roles of volumetric and surface effects are highlighted by a comparison between the Spectral data measured on as sprayed coatings and on polished Coatings. As expected, reflectance rises with the metal addition, but in the transparent region of alumina, a noteworthy behavior is noticed for low aluminum concentrations. Indeed, the reflectance presents Strong composition dependence and remains lower than that of the pure alumina sample. The results show that the optical properties of cermets produced by plasma spraying are controllable and therefore open the door to applications in the areas of solar energy or adronanties.