Construction Of Multi-level Structured Super-hydrophobic Surfaces And Their Anti-icing Performance

The formation and accumulation of ice can easily cause serious damage to equipment such as power lines,aircraft engines and wind turbines.Therefore,the study of surfaces with anti-icing properties and easy de-icing is of great importance in life.Therefore,some scholars have investigated the surface structure of lotus leaves and designed superhydrophobic anti-icing surfaces with the ability to retard the formation of ice nuclei or reduce the adhesion strength of ice.The superhydrophobic surface is considered as an ideal anti-icing surface because of its high contact angle and low rolling angle as well as the presence of surface air layer.The high contact angle reduces the heat transfer between the droplet and the surface in low-temperature environments;the low rolling angle reduces droplet adhesion on the surface and ensures a bounce effect just after the droplet touches the surface;and the presence of a surface air layer slows down further heat transfer between the droplet and the surface.However,conventional superhydrophobic surfaces have two serious drawbacks:(i)the superhydrophobic surface loses its anti-icing performance after a certain number of icing/de-icing cycles;(ii)the wear of the surface can contribute to the loss of anti-icing performance.To address these two problems,different methods are used to construct superhydrophobic anti-icing surfaces with excellent performance.Firstly,a superhydrophobic surface with both anti-icing and de-icing properties is prepared by implanting elastomeric microspheres into the surface using the spraying method;secondly,a wear-resistant superhydrophobic surface is developed using electrostatic powder spraying equipment.The specific research results and innovations are as follows.(1)PDMS microspheres with a size of about 4 um were firstly prepared by emulsion polymerization,and then the microspheres and modified silica nanoparticles were homogeneously mixed in ethanol solution,and finally the microspheres and silica were implanted into the surface of semi-cured fluorocarbon resin by spraying to construct a new dual structure instead of the traditional rigid particle surface.The establishment of multi-stage structure of the surface reduces the direct contact area between droplets and rigid particles,and the smooth PDMS microspheres can effectively reduce the adhesion of droplets.Therefore the surface has better hydrophobicity,high contact angle(CA=171°),low rolling angle(SA=0°)and excellent anti-icing/de-icing performance.Since the droplets are in full contact with the flexible microspheres,the freezing of the droplets will cause compression of the microspheres under low temperature conditions,and the deformation generated by the microspheres will create a reverse repulsive force on the ice,making it possible for the ice to slide off the surface with a small external force(1.53kpa).The PDMS microspheres have excellent adiabatic properties and exhibit excellent static anti-icing performance even at-20°C,delaying the freezing of water droplets for up to 416 s.In addition,the superhydrophobicity and low ice adhesion properties are not lost even after the surface wears out,and the related mechanism is demonstrated.(2)The modified nano-silica and PVDF powder are uniformly mixed by solution blending method and dried to obtain PVDF/Si O2 particles.They were uniformly sprayed onto the steel sheet surface by electrostatic spraying equipment and cured at high temperature to form a continuous superhydrophobic surface.The effect of different modifications of silica on the adhesion,hydrophobicity and anti-icing properties of the coating was explored.The experimental results show that the superhydrophobic surface assembled based on the double-modified silica has a high contact angle(CA=156°)and a low roll angle(SA<15°),while the surface exhibits excellent anti-icing performance at-20 ° C,delays freezing of droplets for up to 223 s,and demonstrates a good dynamic anti-icing performance at-10°C.In addition,the adhesion(6Mpa)and abrasion resistance of the surface coating are improved exponentially.The surface lost only 25 mg after 600 rubbing tests under 500 g of load,and the600 wear tests did not weaken the surface hydrophobicity.These excellent properties are attributed to the micro and nano structure of the surface,the low surface energy and the special modification method of silica.(3)The kinetics of both surfaces were simulated separately by means of simulations.The simulation results proved that:(i)some physical effect between microspheres and ice does exist to make the ice adhesion force decrease.(ii)The intermolecular interaction between the double-modified silica and PVDF is stronger,which obviously improves the wear resistance and adhesion of the coating,but the double-modified silica and nano water droplets also show a tendency of electrostatic adsorption,so the static anti-icing performance and hydrophobicity also change slightly.