Preparation And Properties Of Porous High Absorbing Coatings

With the development of science and technology,there is an urgent requirement to make the satellite positioning and imaging more accurate due to the process in space science detection,military reconnaissance mapping and civil navigation remote sensing.However,the stray light in optical system affects the detection of low light imaging systems such as star sensors and space cameras,resulting in a decrease in star positioning and imaging accuracy.In this paper,we focus on the reduction of the stray light in optical system with fabricating the high absorption coating.As for the traditional high-absorption coating,it combines carbon black used as a light absorber and silicone resin as a binder to create a more dense absorption coating structure.Unfortunately,there is a refractive index mutation between the structure and air leading to the formation of a high surface reflection in the coating-air interface.To solve this challenge,we have several strategies.The introduction of low density silica such as silica microsphere,fumed silica,silica aerogels to the coating will change the internal structure.To cite some examples,the coating porosity is increased and the original refractive index is reduced.In a word,this method would reduce the coating-air interface refractive index difference and the light coating reflectivity on the surface.Furthermore,it improves the coating absorption of stray light.Especially,the sun absorption ratio reached 0.978 via the introduction of silica aerogels.Afterwards,the coating porosity was increased by improving the absorbent structure.Herein,the carbon hollow microspheres replaced the carbon black as the light absorber and the absorbent coating was prepared by crosslinking with silicone resin.The carbon hollow microspheres containing,the thickness and the particle size are three key factors for the solar absorption ratio of the coating.Interestingly,the coating porosity can be further effectively adjusted through introducing carbon hollow microspheres.Specifically,the solar absorption ratio of the absorbing coating is increased to 0.985.In this paper,we used carbon nanotubes which the refractive index of is close to air to replace carbon black.The fibrous carbon nanotubes can be used as the backbone of the silicone crosslinking.In this way,we can overcome the complicated preparation process of carbon hollow microspheres,the instability of the coating thickness and we can also reduce the experimental cost.The carbon nanotubes and carbon black in the light absorption capacity are equivalent.Thus we introduce polystyrene microspheres which can be removed by organic solvent to adjust the absorption coating porosity.According to the amounts of polystyrene microspheres,diameter and the addition of carbon nanotubes,we can fabricate the carbon nanotubes/porous silicone resin superabsorbent coating with a solar absorption ratio of 0.985.