Black cobalt selective coatings by spray pyrolysis for photothermal conversion of solar energy

A low cost technique of spray pyrolysis has been described for the growth of black cobalt selective surfaces on commercially available aluminum and galvanized iron substrates. Parameters of growth have been optimized by a comparative analysis of opto-thermal, structural and optical properties of these films. Optimized films on aluminum were 0.21 μm thick and had α = 0.92 and _100°C = 0.13, Films on galvanized iron substrates gave best results (α=0.91, _100°C=0.12) for film thickness 0.24 μm. Accelerated life test studies indicate that these films have good adhesion to the substrates and are stable up to 220°C.