Preparation And Application Of Special Wettability Surface By Regional Selective Growth Method

Frosting and icing is a widespread phenomenon in nature and industrial field.This not only brings economic losses,but also endangers people's lives.In order to ensure the normal operation of the system,it is necessary to defrost and deice regularly.Compared with the traditional methods,It is an ideal method to change the surface wettability to suppress the adhesion of frost and ice,and to promote defrosting.Because this method does not need additional equipment and energy consumption.Firstly,this paper studies the principle of surface wettability.Then the nucleation phase change model of liquid droplet is established based on the analysis of the influence of wettability and microstructure on the formation process of frosting and icing.The simulation results show that the phase change solidification time increases with the increase of contact angle.At the same time,it is found that the solidification time is 118 seconds,121.6 seconds and 140.6 seconds when the ratio of pitch to width in the composite structure is 0.5,1,2,respectively.The larger the ratio,the more storage air,the more the phase change is delayed.In order to prepare such a superhydrophobic surface of a composite structure capable of storing a large amount of air,firstly,the hole-array micron structure is prepared by laser etching method,and then the zinc oxide nanostructure is prepared by hydrothermal synthesis method on stainless steel substrate.The optimal reaction condition is found: 0.025 mol/L hexamethylenetetramine,0.05 mol/L mixed solution of zinc nitrate hexahydrate and 0.75 g of PEI,60 ml.The reagent is heated for 8 hours at 88 degrees Celsius.In the end,an experimental method to realize micro-nano composite structure by selective growth of zinc oxide regions is explored,which the optimum contact angle reaches 172.5 degrees,and the rolling angle is only 1.7 degrees.The process of freezing and frosting on the surface of different steel samples is also compared.The frozen time of water on the superhydrophobic surface of the composite structure is delayed by 94 seconds compared with the untreated surface due to its large contact angle and the large amount of air stored in the structure.Under the low temperature of-21 degrees Celsius and humidity of 35%,the frost crystal appearance time of the superhydrophobic stainless steel surface prepared by this subject is delayed by 24 days compared with the untreated surface.In particularly humid environments with a humidity of 75%,it is still delayed by 39 hours,and the distribution of the former frost is even rarer at the same time.In addition,during the melting of the frost layer,the superhydrophobic surface has a low adhesion to the melted ice water mixture,and the frost layer shrinks to a spherical shape.Finally,the droplets will fall off from the surface under the external force.