Preparation Of Multifunctional Superhydrophobic Coating By Sol-gel Method

Superhydrophobic phenomenon can be seen everywhere in the nature.Among them,the surface of lotus leaf is the most famous owing to its outstanding water repellence,which is also known as the "lotus effect".It is well known that the superhydrophobic property of a material is the synergy of surface roughness and low surface energy.Over the past decade,mimicking surface function of a lotus leaf has led to the development of a number of artificial super hydrophobic coatings.In spite of the fact that the superhydrophobic surface is of great value in practical applications,there are several key problems in the research and application of super hydrophobic surface:(1)The preparation technology of low cost,easy operation and suitable for massive production of superhydrophobic surface has not been solved yet;(2)Durability,wear resistance and mechanical strength of self-cleaning superhydrophobic surface are still facing great challenges;(3)Uni-functional superhydrophobic coating has been unable to meet the demand.Multi-functional superhydrophobic coatings such as transparent,conductive surface,as well as intelligent sensing surface,etc.,are going to attract people's attention,Sol-gel strategy is recognized as a practical way to thin film formation on various substrates.The advantages include simple and effective process,no requirement of dedicated instrument,low energy consumption and scalable production allow sol-gel strategy a.promising candidate of preparation of superhydrophobic surfaces.In this thesis,a method for preparing multifunctional super hydrophobic coating via sol-gel technique has been studied.The contents and results are described as follows:(1)Preparation and property modulation of conductive,superhydrophobic coatings.Stable graphene/silane sol solution was prepared based on the intermolecular interactions between the hydroxyl groups of the HNO3-activated graphene and the silanol groups of the silane sol.Once spray deposited on glass substrates,the superhydrophobicity was obtained.Moreover,the superhydrophobicity of the conductive coatings was enhanced by introducing nanoparticles into the coating solution,the contact angle(CA)of the coating was increased to 159.4°,and the rolling angle(RA)was reduced to 3°.At the same time,the coating had good conductivity,proven by light emitting diode when the coating was connected into a power circuit.With the help of fluorinated sol,therefore,superhydrophobic coating has been realized.(2)Preparation and property modulation of superhydrophobic coatings for various harsh conditions.Superhydrophobic coatings were prepared by spraying the modified nanoparticle suspensions prepared by sol-gel method.The superhydrophobic coatings with high CA of 159° and low SA around 3° can clean the surface by rolling water droplets off with dirt particles,and have moderate optical transparency.Moreover,the superhydrophobic coatings have shown long-term stability even at freezing or high temperature and different pH.On the other hand,the coatings also exhibit good stability under sunlight exposure.Furthermore,the superhydrophobic coating remained intact and functional after scratched with a sharp blade for several times.Therefore,the low-cost,large-area and long-term stable superhydrophobic coatings with self-cleaning property may be practical for various applications.