Controllable Preparation And Performance Analysis Of High-Entropy Alloy(MoNbHfZrTi) Based High-Temperature Solar Absorbing Coating

Based on the excellent properties of high entropy alloy coating,such as high strength,high hardness,good thermal stability at high temperature,good corrosion resistance,this paper takes the lead in the international research on the preparation of high entropy alloy based solar energy absorption coating and its structure-activity relationship.In the atmosphere of nitrogen and oxygen,the high entropy alloy?MoNbHfZrTi?target was sputtered by magnetron sputtering,and the high entropy alloy coating was deposited on the stainless steel substrate.The thin films of MoNbHfZrTiN and MoNbHfZrTiON were obtained,which had good spectral selectivity,high temperature thermal stability and corrosion resistance.This is the first time in the world to introduce the concept of high entropy alloy into the high temperature solar energy absorbing coating,and the results of the preparation of good performance coating enrich the types of solar energy absorbing coating.In this paper,multilayer solar absorbing coatings are prepared by optical simulation combined with magnetron sputtering.This paper provides a new idea for the preparation of solar absorbing coatings.The main research results are as follows1.In order to further investigate the absorptivity and emissivity,single Al was prepared by DC magnetron sputtering with different deposition parameters.The Al coating deposited with low Ar flow rate and high target power has a low emittance??<0.05?,on the other hand,when fabricated with Ar flow rate of 50 sccm and target power of 300 W,the coating mainly possesses a high absorptance??>0.75?.To further study the mechanism,the optical constants of those Al films deposited with different deposition parameters are investigated.The Al films possessing stronger metallicity have higher extinction coefficient and lower thermal emittance.The surface topography of different thickness films is characterized by scanning electron microscope?SEM?,which clearly indicate the surface roughness is increased with the enhanced thickness.Based on the calculated optical constants,CODE software is employed to optimize a novel SS/Al/AlN coating,the coating prepared by magnetron sputtering system is consistent with the simulated one.2.High-entropy alloys films with the composition of MoNbHfZrTiN and MoNbHfZrTiON are fabricated by a reactive RF magnetron sputtering,which have a good solar spectral selectivity and are used for solar thermal absorption coatings.By changing the flow rate of Ar/N₂/O₂,the metallic content of each layer of the coatings can be controlled,which forms the MoNbHfZrTiN layer with high metallic content and the MoNbHfZrTiON layer with low metallic content.By tailoring the deposition parameters,a novel Al/MoNbHfZrTiN/MoNbHfZrTiON/SiO₂ coating has been successfully deposited on SS substrate for the purpose of shifting the absorption edge to higher wavelength.The coating exhibits a high absorptance of 0.935 and a low emittance of 0.09.The colors and optical properties of layer-added coatings are studied,and the color coordinates are drawn in the chromaticity diagram.By controlling the thickness of MoNbHfZrTiON and SiO₂ layer,the colored Al/MoNbHfZrTiN/MoNbHfZrTiON/SiO₂ coatings are fabricated.3.The present work is a continuation of our earlier work in which high entropy alloy MoNbHfZrTi is used as a raw material to prepare solar absorber coating.In this work,we have further investigated a novel Al/MoNbHfZrTiN/MoNbHfZrTiON/SiO₂multilayer color solar selective absorbing coating,including structure,optical properties,thermal stability and corrosion performance.The results of TEM and XRD indicate that the Al film has nanocrystalline nature and MoNbHfZrTiN,MoNbHfZrTiON and SiO₂are amorphous structure.The results of the mapping make sure the thickness of each layer and distribution of elements.The simulation of optical constants?n and k values?are carried out by CODE software,the results of which indicate that the n and k values decrease from substrate to surface.Neutral salt spray test is preformed to measure the ability of anti-corrosion,which indicates the coating has a good optical performance in3.5 wt%NaCl solution for 24 h.