Preparation And Properties Of SS-N Based Mid- And High-Temperature Solar Selective Absorbing Coating By CAIP

The solar selective absorbing coating is a key material for solar thermal utilization,but there are problems such as complicated process and high cost.In order to promote the application of this material,in this paper,cathodic arc ion plating（CAIP）was used to prepare SS-N based solar selective absorbing coatings,and the mechanism of selective absorption of this coating was studied.In this paper,single layer SS-N solar selective absorbing coating was prepared by CAIP at first.The selective absorption performance of the single layer SS-N coating was improved through the structural design or post-treatment of the coating.For the structural design,a layer of SS-O coating was deposited on the surface of the single layer SS-N coating.After that,the absorptance was increased from 0.519 to 0.796,and the absorption efficiency was increased from2.34 to 3.53.By post-treatment,the single layer SS-N coating was kept at 600℃in the atmosphere for 3 hours,and finally cooled with the furnace.Then,the surface was oxidized to form an oxide layer.After the annealing treatment,the optical properties promoted,and that of the best one increased from 2.50（α=0.483/ε=0.193）to 5.57（α=0.808/ε=0.145）,nearly 2.23 times.Through the micro-morphology,element composition and phase structure analysis of the single layer SS-N coating,the coating was uniform and dense,without obvious defects such as holes and cracks on the surface.And the surface of the coating was smooth with nitride composition scattered with large metal droplets.The phase of the coating was mainly Fe₃N.After depositing SS-O coating,the double layer coating was tightly bonded,showing a clear dividing margin.The morphology of the coating surface was similar to the single layer SS-N coating,which was composed of large particles of metal droplets and dielectric components.The phase of the coating changed,in addition to the Fe₃N phase,the Fe Cr₂O₄ phase came out.Single layer SS-N coating after high temperature oxidation treatment,a continuous network structure appeared on the surface of the coating,and the density of metal particles decreased.After elemental composition analysis,the appearance of the network structure was mainly due to the overflow of the N element in the coating,which made the surface of the coating appear microscopically uneven surface,increasing the absorptance of the coating.In addition,due to the reduction of large metal droplets,the surface roughness of the coating was reduced,and so did the emittance of the coating,which improved the optical selective absorption performance of the coating.After high temperature oxidation treatment,the phase composition of the coating was Fe₃N and Fe₃O₄,and the Fe₃O₄ phase was increased,mainly due to the full oxidation of the coating at high temperature.All in all,both the deposition process and the high temperature oxidation process can obtain a double-layer structure and obtain a solar coating with better performance.