Study On Selective Absorption And Thermal Stability Properties Of CuCoMnO_x Coating Prepared By Sol-gel Method

Solar thermal power generation technology is known as its wide application.With the research on solar absorber coatings,various techniques and methods are developed,especially on the solar coating applied in high temperature environment which owns better thermal stability and higher optical properties.With taking consideration of the coating preparation cost and processing technology,solar selective absorber was prepared by sol-gel method and applied at high temperature.CuCoMnO_x was prepared by sol-gel method,the doping amount of Co,pH value of sol,PEG200 content and heat treatment temperature,oxide particle structure and microstructure have been studied as the influence factors.The multilayer CuCoMn-oxide absorbing layer deposited on substrate by dip-coating method is studied by the substrate surface roughness,coating thickness and optical properties of the absorption layer.Some results could be obtained:a)With a PH value of 3.5 and a heating temperature of 550?,the integrated spinel structure have been observed in the prepared CuCoMn-oxide with a grain size ranged from 300 to 500 nm;b)Under the same heating temperature and processing condition,after 15 min activation on substrate,well adhesion property was found in the three layer absorber coating with a thickness of 200 nm,the ratio of absorptance and emissivity is 0.903/0.148;c)After adding 3at.%PEG200,the oxide particles dispersed more and the size increases,the absorptance of the coating increased to 0.936,respectively.The CuCoMnOx-SiO₂ coating was prepared by the same method,the composition and micro-structure of the two oxides were investigated.The multilayer CuCoMnOx/CuCoMnOx-SiO₂/SiO₂ composite coating deposited on Co-WC thermal spray absorber coating by spin-coating method.The effect of surface treatment on the surface roughness of the absorber and the overlaying of each layer of oxide coating on the porosity,surface morphology and optical properties was analyzed.The results show that the SiO₂ particles independent distribution in the CuCoMn-oxide surface with a spinel structure in the amorphous state;With a surface roughness of 1.12?m and a contact angle of 76.6°,the good flatness and wettability Co-WC absorber coating surface have been achieved;With the overlay of each layer of oxide coating,the porosity of the coating surface decreases gradually and become more smooth.CuCoMn-oxide filled the larger pores in the Co-WC absorber layer as the first sealing layer,using an anti-reflection layer of SiO₂ enhanced the performance of the transmittance and the absorption of the coating.CuCoMnO_x-SiO₂ was used as an intermediate layer,not only play a role as a second sealing layer,but also fill the excess pores,make the coating surface more smooth,and at the same time it functions as the transition layer to connect the sealing layer and the anti-reflection layer,slow the elements diffusion in the coating at high temperature and has the effect of a functional anti-reflection layer.The prepared multilayer composite coating reaches a solar absorptance of 0.915 and a thermal emittance of 0.290.The two kinds of coatings were tested by thermal stability at 500?,respectively,after the thermal cycling of 10 times for 50 h,the surface of the coatings was not peeled off and cracks,the attenuation of optical properties correspond to the standard.