Study On Anti-Icing Characteristics And Mechanism Of Robust Superhydrophobic Coating

Ice formation/icing is a common natural phenomenon,which will affect the normal operation of relevant equipment,and even cause huge personnel and economic losses.Solving or alleviating the icing phenomenon on the material surface is of great significance to reduce the occurrence of such problems.It is one of the urgent problems to be solved in the field of refrigeration equipment and aerospace represented by aircraft.Superhydrophobic surfaces are considered to be the most promising form of icing resistance due to their excellent anti-icing properties,but these materials are fall into a"bottleneck period"due to its fragile surface structure.In this paper,we mainly explored the controllable preparation technology of micro/nano composite structure surface of superhydrophobic coating.We focused on its wear resistance strengthening mechanism,icing delay characteristics dominated by hydrophobicity and ice-phobic mechanism dominated by rough structure.The icing behavior of static water,condensate and impact water on the coating surface were analyzed and its long-term anti icing mechanism was explored.The long-term anti-icing performance of the emerging hydrophobic lubrication coating is studied and prospected.From the practical point of view,a breakthrough in the anti-icing/de-icing problem is realized,which has important development and application prospects.The main research results are as follows,（1）A robust superhydrophobic composite coating material with multilevel roughness and ultra-low surface energy was successfully prepared by a two-step method via FEVE/PU composite resin and micro-silicon powder as adhesive and modified nano-Si O₂ coating as functional top-coating.The strengthening mechanism under the synergistic action of cross-linked composite resin gives the superhydrophobic composite coating good mechanical,chemical and thermal stability.This synergy mainly includes the increase of coating roughness,the embedding of low surface energy nanoparticles and the enhancement of mechanical properties of primer.The superhydrophobic composite coating was prepared by using FEVE/PU blend resin with 10%silicon powder addtion as the primer and spraying top paint after curing at room temperature for 5 h.The sand/dust impact test shows that compared with the coating with FEVE/EVA primer,the coating with FEVE/PU primer with higher strength can resist sand blowing impact for 540 min.（2）In this paper,the freezing process of static water,condensate water and impinged water on the surface of ordinary hydrophobic coating and superhydrophobic coating are compared and analyzed.The growth mechanism of ice crystals in condensate water is deeply studied.And the anti-icing characteristics under high-speed airflow shear condition are studied.For static water,the delayed freezing time on the superhydrophobic coating surface is significantly longer than that on the ordinary hydrophobic surface under the action of"air cushion".And the superhydrophobic coating has better ice repellency.In the case of condensate water,the priority nucleation point of the ordinary hydrophobic surface is located at the edge of the condensed ice,while the superhydrophobic coating surface is located at the top of the condensed ice.The ice crystals grow upward and the ice layer is loose in the superhydrophobic surface.For the impact water,the amount of icing on the surface of the superhydrophobic sample is significantly less than that of the ordinary hydrophobic sample.Under the condition of high-speed airflow shear,the superhydrophobic coating shows excellent effect in delaying icing on both the rod and plate samples.（3）Using MoS₂/WS₂ as solid lubricant,PDMS as binder and modified Si O₂ as filler,a fluorine-free superhydrophobic surface with integrated underside was prepared by one-step spraying method.Layered MoS₂ and WS₂ with high crystallinity are intrinsically hydrophobic.With the increase of the contents of MoS₂ and WS₂,the surface roughness and hydrophobicity of the coating increases first and then decreases,and reached the maximum when the ratio of Si O₂ to sulfide was 4:1.The excellent superhydrophobicity of Cassie state gives the coating excellent icing delay effect,but the ice repellency of the coating is poor under the pinning action of ice layer.According to the analysis of friction behavior,with the increase of MoS₂ and WS₂content,the friction coefficient of the coating decreases gradually.And MoS₂ and WS₂ show excellent friction reduction performance,which is the fundamental reason for the high wear resistance of the coating.（4）A superamphiphobic composite coating with high stability was prepared by two-step technology of electrostatic powder spraying and solution spraying.The addition of Si O₂nanoparticles reduced the fluidity of the primer,induced the formation of multi-level rough structure with large roughness,the network cross-linking structure formed between the resin and Si O₂ particles and the embedding of surface modified Si O₂ particles,which endowed the coating excellent wear resistance under the synergistic effect.Under a 1000 g load,the coating remained superamphiphobicity after Taber wear for 1000 cycle or abrasive paper grinding for100 m or sand erosion for 450 min.The ice adhesion strength and icing delay time of the coating are positively correlated with the change of surface roughness.The excellent hydrophobicity makes the water droplets maintain a large contact angle during the icing process on the coating surface.In addition,the coating also has great anti-fouling,self-cleaning,electrochemical corrosion resistance.（5）By coating silicone oil in the porous structure of modified hydrophobic and oleophilic powder and embedding it in the crosslinked long chain of polymer resin,the long-term interface lubricated coating with"dense-porous-dense"longitudinal structure was successfully prepared.Due to the adsorption of silicone oil by the porous structure of modified particles and the unique longitudinal structure of the coating,the release rate of silicone oil can be inhibited.After being placed for 18 months,ice adhesion strength is less than 20 k Pa due to the silicone oil composition still plays a role in isolating the coating and ice.With the addition of silicone oil,the coating can form a self-lubricating interface and enhance the wear resistance.The study of long-term interface lubricated coatings will provide a reference for the comparative application of coatings,and also provide a research basis for the development of a new generation of coatings.