| The aluminum oxide film layer colored by nickel has a high solar energy absorption rate and a low solar energy emissivity.It has a broad prospect in the field of solar selective absorption coatings and has been widely used.In order to optimize the light absorption ability of the aluminum oxide film colored by nickel under sunlight,aluminum foil was selected as the research object.First,the aluminum foil is anodized with different electrical parameters in a phosphoric acid solution,and then electrolytically colored in a nickel sulfate solution to obtain black films with different chromaticities.Through scanning electron microscope(SEM),X-ray diffractometer(XRD),electrochemical workstation,spectrophotometer and Fourier transform infrared spectrometer;the film formation mechanism of anodic oxidation and the characterization of various properties were analyzed.The main researches are as follows:(1)Phosphoric acid is selected as the electrolyte.Through the observation of microscopic morphology and the verification of corrosion experiment under constant pressure mode,we found that with the prolongation of the reaction time,the inward growth of the film under the action of dissolution will cause micropores.The number increases,and the pore size increases to a certain extent.Under constant time conditions,with the increase of the anodizing voltage,the reaction current also increases,the reaction speed is accelerated,and the growth rate of the anodized film is also accelerated.At the same time,the dissolution rate of the barrier layer is accelerated,so that the film and the surface The micropores continue to grow,the pores deepen and the pore size expands,resulting in thinning of the pore wall.(2)Through the reflectance curve measured by the infrared spectrometer,it is calculated that the aluminum foil surface obtained at a voltage of 20 V and an oxidation time of 20 min has the highest absorptivity of about 0.78 and the lowest emissivity of about 0.14.The seawater distillation experiment results also show that it has a higher distillation efficiency,about 135 g?L-1h-1.(3)Compared with the untreated aluminum foil substrate,the structure of the aluminum oxide film colored by Ni has better corrosion resistance than the aluminum oxide film obtained by anodizing.This can prolong the service life of the film structure under open environmental conditions.After the corrosion test,the absorption rate of the film is not much different,and the emissivity of the film after corrosion is significantly increased.This is due to the increase in the roughness of the film surface through the corrosion test in the corrosion test.After heat treatment,the absorptivity and emissivity of the film are not much different,indicating that the coating structure is relatively stable in terms of thermal stability.(4)The thermal degradation of Ni colored alumina coating was studied through optical property modeling.The initial film consists of a Ni colored alumina film near the substrate.The outermost layer is porous alumina film,which shows that the outer surface is rough.After several hours of heat treatment at 350?,the solar absorptivity of the alumina coating decreased significantly(from 0.78 to 0.64).It was found that the solar absorptivity of the nickel-tinted alumina coating was very sensitive to thermal exposure,and the absorptivity decreased to a certain extent under different treatment temperatures.At the same time,with the extension of processing time,the emissivity also showed a downward trend. |
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