Abstract
Magnesium-based alloys have been widely applied in multiple fields such as aerospace and medical devices,primarily due to their inherent characteristics such as light weight,high specific strength,excellent damping capacity,and superior machinability.In aerospace engineering,thermal control coatings serve as a commonly utilized passive thermal control technology in the thermal design of spacecraft.The selection of appropriate thermal control coatings enables certain components of the spacecraft to be maintained within the desired temperature range,which plays a crucial and irreplaceable role in ensuring the normal in-orbit operation of the spacecraft.Micro-arc oxidation(MAO)technology,also known as a plasma electrolytic oxidation technology,is capable of in-situ growing a ceramic film with strong bonding strength on the surface of magnesium alloys.While providing effective and reliable protection for magnesium-based alloys,this technology can also precisely regulate the thermal control performance of the coatings by adjusting experimental parameters,thereby keeping their temperature within a stable and suitable range.However,at present,magnesium-based alloy thermal control coatings still face several prominent and urgent issues,such as low thermal control efficiency,poor resistance to space radiation,inadequate corrosion resistance,and insufficient thermal shock resistance.Additionally,the environmental friendliness and energy efficiency of the electrolyte compositions used in the process require further enhancement and optimization.Focusing on improving the comprehensive performance of magnesium-based alloy thermal control coatings,this paper briefly introduces their thermal control mechanisms and provides a systematic review on the influence of thermal control performance from two key aspects:experimental parameters and chromatic properties.As a critical experimental parameter,reaction time exerts a significant impact on the thermal control performance of the oxide coating by altering surface structural characteristics such as the thickness,roughness,and the number of pores of the oxide coating.During the oxidation process,electrical parameters including duty cycle,power frequency,and current density significantly modify the surface morphology and microstructure of the coating by changing the energy supply conditions,thereby further regulating important properties such as absorptivity,emissivity,and resistance to ultraviolet radiation.Generally,as the number of protrusions and pores on the coating surface increases,the radiation area expands accordingly,leading to a consequent increase in radiant energy and thus a distinct rising trend in emissivity.Simultaneously,as the surface porous structures increase,the ability of the surface to trap sunlight is enhanced,resulting in a subsequent and noticeable increase in absorptivity.In addition,the composition and proportion of the electrolyte also influence the coating properties to a certain extent.In particular,the addition of different coloring salts into the electrolyte can effectively alter the chromatic values of the oxide coating.The incorporation of nano or micro particles can modify the surface structure of the coating,which in turn affects various properties such as absorptivity,emissivity,corrosion resistance,and thermal shock resistance.Typically,the closer the coating's color is to black,the higher its absorptivity tends to be.Research on the influence of these parameters on various properties of micro-arc oxidation coatings holds significant guiding significance for the development of micro-arc oxidation thermal control coatings with better comprehensive performance and wider application ranges in practical engineering.关键词
镁基合金/微弧氧化/热控涂层/吸收率/发射率Key words
Mg-based alloy/micro-arc oxidation/thermal control/absorptivity/emissivity
