| Airborne aircraft radome is an important structural feature of the radar antenna system.However,airborne radar signal often appears shielding and the electrostatic discharge static electricity even ablation during operation of the aircraft and the radome is the non-metallic material which is poor infrared stealth performance.For these reasons,the surface of the airborne radome is usually coated with a protective coating to avoid affecting the performance and service life of the radome.Airborne radome protective coatings require good construction performance and adhesion,excellent resistance to environmental performance and mechanical properties,strengthening radome's antistatic ability and infrared stealth performance on the basis of ensuring wave-transparent performance.Low temperature carbonized fiber and doped oxide semiconductor as commonly used antistatic agent,which have good infrared stealth performance,are reasonable choice of radome coating filler.In this paper,low temperature carbonized fibers and Zinc Aluminium Oxide(ZAO)with suitable conductivity and infrared emissivity were prepared by adjusting the preparation process.And composite coating with elastic polyurethane resin was prepared.The ZAO with different morphologies was prepared by hydrothermal method.Experiments were carried out by using zinc nitrate and aluminum nitrate solution as reactants,sodium carbonate as mineralizer for hydrothermal reaction.We explored relationship between the morphology and structure of the product under different calcination temperature and different experimental parameters conditions,such as different reactant concentrations(0.01?0.1 mol/L aluminum nitrate),different doping ratios(99:1?93:7),different mineralizers(sodium carbonate and sodium hydroxide)and different sodium hydroxide dosage.It was found that the reactant concentration,the kind of mineralizer and the dosage of sodium hydroxide will affect the growth direction of ZAO crystal and cause the change of morphology.The amount of aluminum doping and calcination temperature will have an effect on the grain size of the product.At the same time,the effects of different preparation methods on the morphology of ZAO were compared.It was found that the ZAO crystals obtained by coprecipitation method were hexagonal conical.However,the crystal particle size and hardness were larger than hydrothermal synthesis method and were not suitable for preparing composite coatings.The composite coatings were prepared by ZAO prepared by hydrothermal synthesis,low temperature carbonized fiber and elastic polyurethane resin.The infrared stealth properties and antistatic properties of different formulations were discussed.Taking into account the infrared stealth performance,anti-static and transparent wave properties required by the radome,the filler are selected ZAO,with the molar ratio of zinc and aluminum 97:3,and the low temperature carbonized fiber,with carbonization temperature 700?.It was found that the infrared emissivity and surface resistivity of ZAO were decreased with increasing of filler content in the same packing.The main reason for the difference of the infrared stealth performance of different types of ZAO composite coating is from the difference of ZAO morphology.Wherein,the flake ZAO with highest degree of infrared wave emission has excellent infrared stealth performance.The anti-static coating,with the filler mass fraction about 15%,the composite coating came into the percolation transition area of electrical properties.The coating surface resistivity plummeted and began to conduct.At the same time,the composite mass prepared by CF/ZAO mixed filler was superior to CF composite coating under the same mass fraction.The reason is that the fiber,that formed an infinite conductive network,greatly increased the number of carriers in the polymer system,thus improving the conductivity of ZAO.The final hybrid filler composite coating has excellent antistatic performance. |
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