COBALT OXIDE SELECTIVE COATINGS FOR ALL-GLASS EVACUATED COLLECTORS

Black cobalt deposits were formed on glass substrates for use in all g lass evacuated collectors. Glass was made conducting by depositing flu orine doped tin oxide films using spray pyrolysis. The reflectivity of this glass was further improved by electroplating a thin nickel layer (0.35 mum) on it. Cobalt oxide thin films were deposited on these nic kel coated conducting glass substrates using spray pyrolysis. The effe ct of cobalt acetate concentration in the precursor solution on the pe rformance of these multilayer coatings was studied. Solar absorptances as high as 0.93-0.94 and thermal emittances as low as 0.09 were obtai ned for films deposited with lower concentrations. For films deposited with higher concentrations the selectivity significantly reduces from approximately 33 to approximately 3.0. Structural analysis confirms t he presence of Co3O4.