Preparation And Thermal Control Properties Of Black MAO Coatings On MB15 Mg Alloy In The System Containing Cu Salt

Magnesium alloys, which are regarded as “21st century green engineering metal structure materials” and “light materials”, have been widely used in aerospace field. In order to improve the thermal protection of magnesium in aerospace field,thermal control coatings were prepared by MAO. In my report, the color, thickness, roughness, phase composition, and microstructure of the coatings were measured. Furthermore, the relationship between thermal control properties and structure was analyzed.High absorbance and high emissivity thermal control coatings were prepared in solutions containging Na2 Si O3 and phosphate. The main composition of the coatings obtained in Na2 Si O3 solution were Mg O and Mg2 Si O4. In phosphate solution, when the power frequency was high, the main composition was Mg O, while the main composition were Mg O and Mg3(PO4)2 under the condition of low power frequency. With the increasing of the concentration of Cu SO4, there was no change in thickness and roughness, while the color became deeper, which lead to the increase of the solar absorbance and the emissivity. Following the variation of the concentration of Na2 Si O3 and phosphate, the color turned lighter. In addition, the solar absorbance declined and the emissivity remained unchanged. As the increasing of current density and reaction time, the color became deeper and the thickness and roughness rised, which resulted in the rise of the solar absorbance and the emissivity. By containing Fe2+ 、Co2+ 、Ni2+ ions, the thickness and roughness of the coatings increased, which resulted in the rise of the solar absorbance and the emissivity as well. In short, the thermal control properties of the coatings achieved in phosphate solution was better than that of the coatings achieved in Na2 Si O3 solution.High absorbance and low emissivity thermal control coatings were prepared in Na Al O2 solution. Some micro-pores were integrated, with the increasing of Na Al O2. The main composition was Mg Al2O4. The color turned lighter, and the thickness and roughness declined, following the increasing of the concentration of Na Al O2 and power frequency. Nevertheless, the color became deeper and the thickness and roughness of the coatings rised with the increaseing of the concentration of Cu SO4 and reaction time. The current density had effct on the color. The process conditions made the most impact on thermal control properties. The solar absorbance and emissivity of the coatings increased, following various concentrations of Cu SO4, power frequency, current density and reaction time. However, as the increasing of the concentrations of Na Al O2, the solar absorbance and the emissivity declined.