Preparation And Property Of Al/CuCoMnO_x-M/SiO₂ Composite Coatings

In recent years,due to energy crisis,solar energy,as an inexhaustible and clean energy,is widely utilized in the world.Photo-thermal conversion technology is one of the most important ways for human to use solar energy.As a key component of concentrating solar power（CSP）systems,the property of solar selective absorption Coatings（SSACs）will directly affect the efficiency of efficiency of energy conversion.It is a trend for application to prepare the films with excellent optical properties,high thermal stability,good weather resistance and can largely industrial production simultaneously.Multi-layer film system was designed to improve selective absorption properties,insisting of the selectively solar-absorbing and anti-reflection（infrared transparent）layers.CuCoMnO_x powders were synthesized by Co₂O₃,CuO and MnO₂ via solid reaction method.The effects of reaction time and temperature on micro-structure,chemical components and optical performance of the composite powder were explored.Powders reacting at 1300℃for two hours,mainly composed of CuCoMnO_x with tetrahedral and octahedral shapes,showing a high absorptance of 0.916 in the wavelength range of 0.3².5μm and a low emittance of 0.404 in the range of 2.5²5μm.Using synthetic CuCoMnO_x powders and M（Al,Cu or Mo）as pigments and silicone resin as a binder,a single solar selective absorbing coating（CuCoMnO_x-M）was prepared via paint coating method on the surface of stainless steel.The influences of different solid content（10⁶0%）,M（Al、Cu、Mo）content（0.5².5%）,milling time and thickness on the optical properties of composite coatings were discussed,exploring coating with the best optical property as the absorption layer.The results show that the coating with a solid content of 40%,adding with 1%Al,milling 18 hours,a thickness of 1.93μm,has the best performance ofα=0.921,ε=0.366.SiO₂ anti-reflection layer was prepared by sol-gel method and Al reflection layer was prepared by paint method on or under the absorption layer,respectively.Surface and cross-section morphologies,optical properties,thermal stability and weather resistance of multilayer composite coatings were tested,and the results show that the optical properties of the coating have been greatly improved,the absorptance is 0.924,and the emittance is 0.344.Meanwhile,there are no cracks or spallings of the composite coatings after 100 times thermal shock and annealing for 100 h under the temperature of 500℃.And the coating showed good environmental resistance after 500 h condensation test,with the PC<0.05.It is considered that the prepared coating has good absorption performance,high temperature stability,advantages of low cost and convenient construction,which are beneficial to the utilization and development of solar energy.