| Under the background of the gradual reduction of a series of non-renewable energy sources such as petrochemicals,the existing world energy structure will undergo major changes.Solar energy will gradually replace existing conventional energy sources and become an indispensable and important energy source for human life and production.The research on solar thermal energy utilization has become a hot spot in the scientific community today.It has set off a new wave of scientific research around the world.The mainstream preparation method of solar high selective absorption coating?magnetron sputtering method?has many problems such as complicated process,high production cost,low efficiency and so on,which has been restricting large-scale application.Therefore,this paper proposes a new method to solve the above problems.Synthetic ideas and simple processes,but also to solve the heat resistance of the coating,the main research content and results are as follows:The first part,this chapter synthesized a blocked polyisocyanate crosslinker using isophorone diisocyanate?IPDI?,formic acid and a hydroxyl-terminated polyether modified silicone oil?THPDMS?as raw materials,?-caprolactam as blocking agent,dibutyl tin dilaurate As well as triethylamine as a catalyst,The successful synthesis of the cross-linking agent was verified and then crosslinked with the resin at high temperature.Through infrared magnetic characterization,the end-capped siloxane-containing polyisocyanate crosslinker was successfully synthesized,and the in-situ IR and DSC were combined to characterize the deblocking temperature of the blocked siloxane-containing polyisocyanate crosslinker at160-170°C.Its curing temperature with hydroxyl resin is 180°C.It was confirmed that the addition of THPDMS in the crosslinker will greatly increase the elongation at break and tensile strength of the film and improve the toughness and mechanical strength of the blank film by tensile characterization.Through thermal weight loss characterization,it was found that the blank film without THPDMS began to decompose at 250°C,and the thermal decomposition of the added THPDMS was all above 300°C,up to 350°C,which basically meets the requirements of medium and high temperature solar absorbing coatings.At the same time,the degree of graphitization of the residue after calcination of the film was analyzed by Raman spectroscopy and the surface morphology of the residue was observed by atomic force microscopy.It was further confirmed that the THPDMS content increased and the thermal stability of the film was strengthened.The second part uses Cu?NO3?2·3H2O,Cr?NO3?3·9H2O,MnCl2·4H2O as the main raw material,and NaOH as the precipitant to prepare black powder.Using a binder composed of a silica sol and a silicone resin,a coating film with a content of about 10%of a silica sol has the best comprehensive performance through various tests.Through thermogravimetric analysis,it was demonstrated that this coating meets the requirements for medium and high temperature coatings.When the amount of Cr?NO3?3·3H2O in the powder is larger,the absorptivity?s and the emissivity?T of the obtained coating are relatively low.When more Cu?NO3?2·3H2O powder is added,the absorption rate?s of the coating will decrease,but the emissivity?T will increase.From the powder SEM image,the convex structure and the pore structure on the surface of the powder act as a scattering effect on the light of a certain wavelength,which increases the number of times of light reflection,thereby increasing the absorption rate and preventing the surface from agglomerating,so thermal stability of the metal particles is greatly increased.The crystal form of the powder was analyzed by XRD,and the powder obtained in the experiment was a composite oxide CuCrMnOx.In the third part,FexCuyMnzO was prepared by sol-gel method,and CaCO3 combined with high-temperature calcination method was used to fabricate needle-like structure on functional powder.Using the above-mentioned silicone resin and silica sol,with a certain proportion of auxiliaries and functional powders,uniformly coated on an aluminum plate by high pressure spraying.XRD shows that the crystalline state of FexCuyMnzO is formed after powder calcining.The chemical structure of powder A is characterized by XPS characterization and energy spectrum.The chemical structure of powder A is approximately CuMn3FeO4.XPS also confirms that the elements of the powder coexist with chemical bonds.The UV3600 and TENSOR27 optical instruments were used to examine the UV-Vis-IR band absorption of the coating and the emissivity of the infrared and far-infrared bands,and the solar selective absorbing coating with high absorptivity in the UV-Vis-IR band and low emissivity in the far infrared band is obtained.The particle size analyzer was used to investigate the calcination time of the powder and the best reaction time was 8 h.The SEM was used to characterize the surface structure of the powder,and the effect of CaCO3 addition on the surface morphology of the powder was explored,thus affecting the emissivity of the coating.Using a silicon wafer as a substrate,a pyramid-like pyramid structure is etched on the surface.The SEM was used to characterize the surface morphology,and the AFM was used to analyze the etched morphology of the silicon wafer from a three-dimensional perspective.It was found that the etching time affected the surface density of the silicon wafer.The coating on the silicon wafer was characterized by a UV3600 optical instrument.The increase in the absorption rate of the coating was found,and the more dense the pyramid-like structure,the higher the absorption rate.The actual measurement shows that the coating has a high selectivity to absorb sunlight,and it is further confirmed that the highly selective absorption of solar energy is reflected in the high absorption in the UV-Vis-IR region and the low emission in the far-infrared region. |
PDF Full Text Request