The Preparation And Research Of Spinel Solar Selective Absorption Coating

Solar selective absorption coating for use in middle-high temperature becomes a hot research topic in recent years. Conventional selective absorption materials can not satisfy the need for use in the solar energy heat utilization equipment at middle-high temperature due to poor weather resistance and thermal stability. However, owing to excellent heat resistance and oxidation resistance, Spinel structures are expected to be an ideal solar selective absorbing material for high temperature.In this paper, Co₃O₄ spinel coating was prepared by firstly electroplating a Co layer on the surface of Ferritic stainless steel, and secondly heat-treatment at 800? to oxidize Co into Co₃O₄; The effects of electroplating and heat-treatment conditions were studied by parallel experiments, and particularly, the influences of parameters such as pH value of plating solution, current density and temperature of electroplating on Co coating were schematically studied and the optimum process parameters were obtained, the durations for heat oxidation were also carefully studied; Meanwhile, the morphologies, structures and thermal stability of the obtained coatings were characterized by X-ray diffraction spectrum?XRD?, Scanning Electron Microscope?SEM?, Energy Dispersive Spectroscopy?EDS?, and absorptivity-reflectivity techniques.The main innovation of this paper is that a new method for preparing spinel structures was achieved by combining electroplating with heat-oxidation, and compared with spraying and magnetron sputtering etc., this method which does not require expensive equipment and harsh experimental conditions is very hopeful for mass production in industry.The results of this study are as follows:The optimum parameters for electrodepositing Co coating: the p H value of plating solution is 5.0, the cathode current density is 20 m A/cm2, the temperature is 20?;The Solar absorptance of Co₃O₄ spinel coating can reach as high as 0.892, and thermal emittance can achieve as low as 0.205 by controlling the thickness of the spinel coatings;No degradation was observed about the morphology and solar absorptance of Co₃O₄ spinel coating even though an heat oxidation duration as long as 100 hours was employed, indicating Co₃O₄ spinel coating has a very good thermal stability; Moreover, excellent thermal stability and weather resistance were also confirmed by thermal shock test.