Study On Preparation And Properties Of AZO/MgO-Y₂O₃ Conductive Thermal Control Coatings On MB8 Magnesium Alloy Surface

With high thermal conductivity and good high temperature strength,MB8light Weight magnesium alloy is often used in some core components of spacecraft.It is particularly critical to prepare thermal control coatings With high charge conductivity on the surface of MB8 magnesium alloy to overcome solar radiation and the charge-discharge effect caused by high-energy plasma in space environment.In this thesis,the thermal control coating Was prepared on MB8 magnesium alloy substrate by micro-arc oxidation and magnetron sputtering technology,and then AZO conductive film Was deposited on this basis.In addition,the direct influence of process parameters on the structure and properties of the conductive thermal control coating Was further discussed in the thesis.Firstly,the thermal control coating Was prepared on the surface of MB8 material by adapting micro-arc oxidation technology,and the content of each component in the electrolyte system of trisodium phosphate-sodium metaaluminate Was optimized by orthogonal experiments.The results sho W that When the concentration of trisodium phosphate is 20 g/L,sodium metaaluminate is 15 g/L and potassium hydroxide is 6 g/L,a coating With the best thermal control performance Will be formed on the surface of MB8,and its absorption and radiation ratio is 0.485;in addition,the influence of duty cycle,po Wer frequency and current density on coating properties Was also discussed in the thesis.The experimental results present that When the duty cycle is 10%-40%-10%,the po Wer frequency is 700 Hz and the current density is 7 A/dm²,the radiation absorption ratio of the coating is 0.448,and the performance is the best;The unique 4f layer structure of rare earth element yttrium makes its absorption efficiency of external energy lo W,Which provides theoretical basis for it to become a film-forming component of thermal control coating.Therefore,in order to further reduce the absorption rate and improve the emissivity,yttrium nitrate Was added to the trisodium phosphate-sodium metaaluminate electrolyte system to prepare MgO-Y₂O₃ thermal control coating.The experimental results prove that the addition of yttrium nitrate obviously improves the temperature control performance of the coating,and the absorption-radiation ratio of the coating is 0.420.The gro Wth mechanism of MgO-Y₂O₃thermal control coating Was then discussed in this thesis.In order to improve the charge conduction ability of MgO-Y₂O₃thermal control coating,AZO thin films With high charge conduction ability Were further deposited on the surface of MgO-Y₂O₃thermal control coating by magnetron sputtering technology.The effects of Ar pressure,sputtering po Wer, substrate temperature and deposition time on the surface morphology and properties of AZO/MgO-Y₂O₃ coating Were also discussed in the thesis.When the sputtering po Wer is 300 W,the substrate temperature is 200℃,the Ar pressure is 0.4 Pa,and the deposition time is 120 min,the coating has the best conductivity.At this time,the square resistance is 21Ω/sq,but the absorption-radiation ratio of the coating decreases by 0.049.When the deposition time is 30 min,the square resistance of the coating is 980Ω/sq,but the radiation absorption ratio of the coating decreases by only0.005.Therefore,AZO/MgO-Y₂O₃coatings With different properties can be prepared according to the needs by preparing different deposition periods.