Colloidal silica films on glass produced by withdrawal from colloidal baths are of value as antireflection coatings. The effect of particle size on the refractive index and density of these films was determined, and the optimum particle diameter for maximum transmittance of solar radiation through glass was estimated at 45 nm. Mixed colloidal carbon and silica films produced by the same means were also studied. These films are useful as solar selective absorbing coatings when deposited on copper. The optical constants of the mixed colloidal films were determined and the results compared with the predictions of the Maxwell Garnett theory. The effect on the thermal efficiency of solar absorbing coatings of a variation in the carbon-to-silica weight ratio was determined.
© 1988 Optical Society of America
R. M. Vegners, David R. McKenzie, and R. J. Hunter, "Optical properties of colloidal carbon and colloidal silica films," Appl. Opt. 27, 3351-3355 (1988)