| Recently,superhydrophobic surfaces have been widely used in the fields of drag reduction,self-cleaning,anti-corrosion,oil-water separation,anti-freezing and anti-reflection transparent coatings due to their special wetting properties.However,the current preparation methods have problems such as complicated mold manufacturing,harsh experimental conditions,limited substrate,inability to mass-produce and high cost.In order to solve the above problems,this paper proposes a new method to prepare a superhydrophobic surface with a uniform distribution of micro-nano rough structures by electrostatic spraying.Simulation and experimental verification of electrostatic spraying droplet breakup are carried out,and the preparation of superhydrophobic surface by electrostatic spraying technology is explored.The main research contents include the following points:(1)The wettability theory of superhydrophobic surfaces and the related theory of electrostatic spraying were studied and analyzed.The surface wettability,contact angle and four typical three phase contact models of solid,liquid and gas were introduced.Three stages of jet development in electrostatic spraying were expounded,and three ways of droplet charging in electrostatic spraying were compared.The force analysis of droplet and the theory of droplet breakup under electric field were studied,and the critical charge of droplet breakup with or without airflow disturbance was calculated respectively.(2)The multiphysics coupling simulation model of electrostatic spray droplet breakup was established by COMSOL Multiphysics.The Kelvin-Helmholtz droplet breakup model was coupled with the electrostatic field model and laminar flow model to simulate the droplet breakup phenomenon of electrostatic spraying.The electrostatic field distribution characteristics and electrostatic spraying characteristics were investigated under the pin-ring electrode configuration.The droplet breakup characteristics and droplet distribution uniformity were better when the electrostatic voltage was less than-9 k V and the pin-ring distance was less than 12 mm,and the droplet charge characteristics were better when the pin-ring distance was 4 mm.(3)The experimental device of electrostatic spraying was set up and the simulation results were verified by experiments.The advantages of pin-ring electrode compared with pin-plate electrode were analyzed,the difference between contact charge and induction charge was compared,the configuration mode of electrode was determined,and the key components were selected.The influence of electrode configuration parameters on droplet distribution uniformity and charge characteristics in electrostatic spray was explored.The simulation results showed the same variation trend as the experiment,which could well predict the experimental results.Finally,the optimal electrode configuration parameters were obtained as follows: electrostatic voltage-6～-7 k V,pin-ring distance 4 mm,ring electrode diameter 30 mm.(4)The superhydrophobic surface of silica coating was prepared,and the effects of different process parameters on the superhydrophobic effect and surface morphology were investigated by experiments.The process of electrostatic spraying deposition of superhydrophobic surface was introduced,and the principle of low surface energy modification was described.The surface morphology of the samples was observed by field emission scanning electron microscope,and the hydrophobicity of the samples was evaluated based on the superhydrophobic surface wettability theory.The contact Angle of the sample to water was measured by a contact angle measuring instrument.The results show that the superhydrophobic surface with good hydrophobicity can be obtained under certain experimental parameters. |
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