Research On Preparation And Performance Of Nitride Light Absorbing Coatings

Light-absorbing coatings are widely used in solar light-to-heat conversion,stray light suppression,heat detectors and other fields.Traditional light-absorbing coating materials mainly include carbon black,carbon nano-tubes,black chromium,black nickel,etc.Although these materials have a certain light absorption capacity,they have disadvantages such as fragile structure,or susceptibility to the use of the environment,or easy to pollute the environment during the preparation process.An excellent light-absorbing coating should have the characteristics of strong film-base bonding,stable physical and chemical properties,environmentally friendly,large-area preparation,and good absorption performance in a wide spectral range.TiAlN is a kind of ternary ceramic material,which is a kind of insoluble transition metal nitride.It has excellent physical and chemical properties,high melting point and hardness,stable at high temperature and corrosion resistance.TiAlN is also a potential spectral absorption material.In this paper,TiAlN is selected as the basic film material and is deposited by reactive magnetron sputtering technology.The light absorption performance of the film is improved through the synergy of the film deposition process and the surface microstructure of the film.Firstly,adjusting the deposition process parameters to optimize the light absorption performance of the single-layer TiAlN film,so that the absorption rate in the 200-2500nm band reaches the highest.Then the optimized single-layer TiAlN film is loaded by two different wet etching techniques to form a NiCr alloy film with a"light trap"microstructure on the surface to form a double-layer film system to further improve the absorption rate of the TiAlN film.Finally,the stability of the double-layer film system under high-temperature air atmosphere was evaluated through annealing experiments.The main research results obtained are as follows:1.The XRD test results of TiAlN thin film prepared by magnetron sputtering method show that the thin film is crystallized with(200)crystal plane preferentially.Changes in the nitrogen/argon flow ratio,sputtering pressure and substrate temperature will affect the surface morphology of the TiAlN film,while changes in the surface morphology of the film will affect its spectral absorption performance.Generally speaking,TiAlN film with a rough surface has better absorption properties than the smooth one.When the Ti target power is 200W,the Al target power is 200W,the sputtering pressure is 1.1Pa,and the substrate temperature is 200°C,the absorption rate of the TiAlN film in the 200-2500nm band is the best.This is demonstrated by the fact that when the incident light wavelength band is 200-750nm,the reflectivity is limited to less than 12%,with the lowest reflectivity reaching 7.5%;in most parts of the 750nm-2500nm band,the maximum reflectivity of TiAlN films is less than 25%.2.The NiCr alloy with certain light absorption properties is selected as the surface microstructure layer of TiAlN film.The NiCr layer was etched by two different methods:cerium ammonium nitrate chemical free corrosion method and hydrofluoric acid dealloying corrosion method.The results show that after corrosion by the acidic solution of cerium ammonium nitrate,the microscopic morphology of the sample changes,no longer uniform and dense,and the phenomenon of"blackening"appears macroscopically.As the corrosion time increases,the"blackening"is more obvious,that means,higher absorption rate.Dealloying the(NiCr)₆₅Ti₃₅ precursor film with hydrofluoric acid as an etching solution will form a porous structure with a continuous network structure,which increases the number of incident light reflection and absorption,thereby reducing the reflectivity.3.The spectral absorption performance of the TiAlN/NiCr double-layer absorption film system has been studied.The absorption performance of the"TN-HF"film system at low temperatures is slightly better than that of the"TN-Ce"film system,but"TN-HF"film fails after annealing at 300?/2h,while"TN-Ce"film can not only withstand annealing at 500?/2h,but also has better absorption performance as the annealing temperature rises.