Experimental Study Of Anti-icing Property On Superhydrophobic Surfaces With Different Microscopic Structure

The problem of icing on the power line can lead a great danger to the power grid,which causes disaster and huge economic loss.The traditional de-icing methods include artificial ice removal,mechanical deicing,chemical deicing and heating.et.These traditional methods of removing ice are generally inefficient,environmentally unfriendly and wasting energy.The superhydrophobic surfaces exist excellent self-cleaning effect according to its special structure,leading to delay the formation of ice,thus attracting the interest of researchers.Although the water can be inhibited on the superhydrophobic surfaces with multiple structure compared with slippery hydrophilic and hydrophobic surfaces,few studies focus on anti-icing property of superhydrophobic surface with different microscopic structure.In this article,femtosecond laser,electroplating and chemical deposition are used to prepare micro,nano and micro-nano structure superhydrophobic surfaces respectly.These surfaces are characterized by morphology and wettability.Freezing and impacting experiments are executed on these surfaces.The results are as follows:(1)Preparation and characterization of superhydrophobic surfaces with different microscopic structure.PTFE surfaces are prepared by the femtosecond laser.Micro structure with different pillar height are acquired by changing laser power.The electrochemical workstations are used to electroplate the copper substrate to get nano structure superhydrophobic surfaces that exhibit different tilt angle and air cushion size by adapting time and current density.The micro-nano structure superhydrophobic surfaces are made by using chemical deposition method.The concentration of solution will control particle size.SEM and TEM are employed to observe the morphology of these surfaces.Surface wettability is measured by contact angle measurement device.The contact angles of all surfaces were between 150°and 155°,with the rolling angle less than 3°.The results show that the superhydrophobic surfaces with different microscopic structure are successfully prepared(2)Study on the freezing behavior of sessile droplet on superhydrophobic surfaces with different microscopic.A CCD camera is used to visualize the icing process of sessile droplet to record the icing delay time,icing time and ice layer height of droplet deposited on the superhydrophobic surfaces with micro,nano and micro-nano structures under different degrees of supercooling.The contact angle of melted droplet on the surface is also measured.The size of the sesslie droplets are 13?l.The experimental results show that the freezing is delayed at-10°C on the micro-structure surface.The icing delay time decreases with the decrease of the micro-pillar height.The contact angle decreases significantly and the droplets will not roll off easily after the droplet melting.When the degree of supercooling of the surface is lower than-15°C,the droplets rapidly freeze on the surface without icing delay.The icing time of droplet at different micro-pillar heights is slightly different under the same wall temperature.The lower the wall temperature is,the shorter the icing time experience.As to superhydrophobic surfaces with nano structures,it can be found that icing delays occur on each wall lying at-5°C;freezing delay occured at-10°C on the surface prepared under a current density of2mA/cm~2 for 500s.The droplets remain in the Cassie state after melting.For micro-nano structure superhydrophobic surfaces,the icing time of the three surfaces is approximately the same at-10°C.The longer icing delay time means larger microparticles size.The droplets will be collapsed during the icing delay,and the droplets do not roll off easily after thawing.(3)Visual experimental study of droplets impacting superhydrophobic wall surfaces with different microstructuresThe high-speed camera is used to visualize the impact of droplets on the super-hydrophobic surfaces.The influence of impacting velocity and degrees of supercooling on droplet spreading coefficient is studied.The experimental results show that the droplet spreading coefficient increases with the increase of impacting velocity.The“pinning droplet”is more likely to appear on the surface with the greater degree of undercooling under the same impacting velocity.The difference in microscopic structure mainly represents the difference in the size of“air cushion”of the surface.It can be found that when the size of“air cushion”is larger,the droplets are less prone to“pinning”under the same impacting velocity and undercooling conditions of the surface.