High-temperature solar absorption coating is the core material of solar thermal power generation, and also plays an important role in heavy oil extraction, seawater desalination, regional heating in winter, and coping with haze. High-temperature solar absorbing coatings should have high absorptivity, low emissivity, and good thermal stability. However, the lack of key technologies and core materials for solar thermal power generation has severely restricted the development of related industries. In recent years, metal-dielectric composite coatings with a high degree of concern are prone to metal oxidation, diffusion, and the like due to high temperature conditions, which ultimately leads to degradation of optical properties of coatings. How to overcome the above disadvantages and prepare solar absorbing coatings with excellent performance has been a challenge in the field of new materials and energy research.
Ultra-high temperature ceramics (TiC, WC, HfC, ZrC and TiN) have high melting point, high hardness, high thermal conductivity, good oxidation resistance and thermal shock resistance, moderate thermal expansion coefficient and potential spectral selectivity. In recent years, Liu Gang, Ph.D., a researcher at the Gansu Provincial Key Laboratory of Clay Minerals Application (Environmental Material and Eco-Chemical Research and Development Center), Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, pioneered the ultra-high temperature ceramic-based high-temperature solar spectrum selective absorption coating in the world. Study on Controllable Preparation and Structure-activity Relationship of Layers. In cooperation with Wolfgang Theiss, a professor at Aachen University of Technology in Germany, the optical constants of stainless steel, ultra-high temperature ceramics, optical glass, and alumina were obtained through optical software simulation. Based on this, various ultra-high temperature ceramics were successfully simulated and designed. Base solar absorption coating. According to the results of optical simulation, SS/TiC/Al2O3, SS/TiC-Y/Al2O3, and SS/TiC-ZrC/Al2O3 were prepared at a deposition temperature of 300oC using a magnetron sputtering technique using stainless steel (SS) as a substrate. SS/TiC-WC/Al2O3, SS/Al2O3(L)-WC/Al2O3(H)-WC/Al2O3, and SS/TiN/Al2O3 series of high temperature solar absorbing coatings. The absorption rate of this type of solar absorption coating is greater than 0.92, the emissivity is less than 0.12, and it has good thermal stability (greater than 600oC), corrosion resistance, and thermal shock resistance. Part of the coating has good long-term thermal stability under a vacuum of 800oC. It is one of the best solar energy absorbing coatings reported at present.
Researchers used modern analytical characterization techniques to study in depth the structure-activity relationship of such coatings and elucidated the mechanism of optical performance degradation at high temperatures: Raman spectroscopy of transition metal carbide solar absorbing coatings with increasing heat treatment temperatures The ID/IG ratio gradually increased, that is, the sp2C content gradually increased, which led to the intensification of the graphitization process on the coating surface, and ultimately led to the degradation of the optical properties of the coating. In order to suppress the increase of sp2C content in the process of high-temperature fitting, the researchers prepared the SS/TiC-ZrC/Al2O3 absorbing coating using the dual target co-sputtering technique. The composite ceramic coating has high absorptivity (greater than 0.92), low emissivity (0.11), and high long-term thermal stability (700oC). In addition, the researchers introduced a trace of rare earth cerium in the membrane system design, and finally produced a super-high-temperature ceramic solar absorbing coating with a microporous structure through high-temperature (800oC, 5h) vacuum heat treatment, and the absorption rate was greater than 0.90. The emissivity is less than 0.11, and it has good long-term thermal stability under high temperature conditions of 800oC, which has opened up a new method of preparation of microporous super-high temperature ceramics. At the same time, the researchers also prepared a purple high-temperature solar absorbing coating (SS/TiC-WC/Al2O3), and carried out a study of its chromaticity, drawing a chromaticity diagram.
The research work provides a simple and universal new method for the preparation of high-temperature solar absorbing coatings. It has enriched and developed the theory of high-temperature solar absorbing coating film systems, revealed the structure-activity relationship of the coatings, and elucidated the optical attenuation at high temperatures. The mechanism greatly expands the application of ultra-high temperature ceramics in solar thermal power generation and lays a theoretical foundation for the controllable preparation of such high temperature solar absorbing coatings. It also has important application value in the research field of medium and low temperature solar absorbing coatings. . Related research results were published in the journals Solar Energy Materials & Solar Cells, RSC Advances, Optical Materials, Surface Engineering, Journal of Materials Engineering and Performance. At the same time, it has applied for a national patent, application number 9, 201610418136.3, 201610418437.6, 201610418415.X, 201610424296.9, 201510983832.4, 201510983817.X.
This series of research work has received long-term support from the National Natural Science Foundation of China Youth Fund (51402315), the Chinese Academy of Sciences Solar Energy Action Plan, and the Chinese Academy of Sciences repair and purchase special projects.
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