Study On Perdurable Solar Selective Absorbing Coatings

In recent years, the research and application in the industry of solar spectrum selective absorbing coatings have been given more and more attention. This thesis summarized their basic types, absorption mechanisms,preparation methods,introduced the research work and new results at home and abroad.Then perdurable coatings were prepared using solution growth technique,which is simple ,cheap and less pollution.Firstly, model was selected to calculate the porous coatings by comparing the modified uniformity monolayer with heterogeneous film.Even modified with Maxwell-Garnet theory and Bruggeman theory ,the uniformity monolayer was not suit to the actual porous coating .While the model of heterogeneous film fit the the actual porous coating well.Using the the later model ,the optical performance of PbS/Al,PbS/Cu and PbS/Ni coatings were calculated .The PbS/Cu and PbS/Al coatings were better than PbS/Ni coating.Then the optical performance of molybdenum black coating was calculated with uniformity film model for its compact fabric. The optical performance of CuO/Cu was calculated consider the effect of Cu2O ,and pure CuO coating was better than the impure coating.Secondly, three kinds of coatings were prepared using solution growth technique.The coating of lead sulphide was prepared by dissociating thiourea in an alkaline solution containing lead acetate on the base material of copper . The molybdenum black coating was prepared by deoxidizing (NH4)6Mo7O24 in the solution containing NH4Cl on the base material of aluminium and aluminium alloy .And the pure coating of cuprum oxide by oxidating copper with hypochlorous sodium in the alkaline solution. The optimized condition was studied considering reaction temperature , reaction time , pH of the solution , concentration of reactant and pretreatment of the base material. The coatings were analyzed by XPS, SEM, UV-visible-near infrared light spectrophotometer and Fourier transform infrared light spectrograph. The difference in solar absorptivity between the calculated and measured values of these coatings was small.Finally, an additional TiO2 film was deposited on three coatings ,and the performance,such as absorptivity, temperature-fast acid-resistant, abrasion resistance,heat insulation and self-cleanness , were compared between the original coatings and the compound coatings.The results showed that compound coatings basicly reached our criterion and was superior to the original coatings.