CN114535026B

CN114535026B - High-robustness lotus leaf structure-imitated super-hydrophobic coating and preparation method and application thereof

Info

Publication number: CN114535026B
Application number: CN202210049774.8A
Authority: CN
Inventors: 吴楠; 孟芸芸; 邢素丽; 尹昌平; 江华阳
Original assignee: National University of Defense Technology
Current assignee: National University of Defense Technology
Priority date: 2022-01-17
Filing date: 2022-01-17
Publication date: 2023-05-30
Anticipated expiration: 2042-01-17
Also published as: CN114535026A

Abstract

The invention discloses a super-hydrophobic coating with a lotus leaf-like structure and high robustness, a preparation method and application thereof. The high-voltage static in the spraying process atomizes the liquid drops into charged fog drops with the particle size of 20-100nm, and the charged fog drops are assembled and stacked under the action of high-voltage electric field force to form the compact high-robustness superhydrophobic coating. The prepared coating has excellent superhydrophobicity and air layer stability, still keeps good superhydrophobicity under the effects of ultrasonic and high static water pressure, and can be applied to the fields of waterproofing, antifouling, corrosion prevention, biomembrane adhesion prevention and the like of marine equipment such as ships, submarines, drilling platforms and the like.

Description

High-robustness lotus leaf structure-imitated super-hydrophobic coating and preparation method and application thereof

Technical Field

The invention relates to the technical field of preparation of super-hydrophobic coatings, in particular to a super-hydrophobic coating with a lotus leaf-like structure and high robustness, and a preparation method and application thereof.

Background

It is well known that superhydrophobic materials require the construction of their low surface energy and micro-nano secondary roughness structures. The superhydrophobic surface always has pores of different dimensions that form an air cushion of the interface when in contact with water, thereby "lifting" up the droplets to form a superhydrophobic state. The superhydrophobic microstructures prepared by some simple and portable methods such as air spraying, dip coating, brush coating and the like tend to have larger pores, and the raised structures are poor in firmness and compactness, which is one of the main reasons for poor durability of the superhydrophobic materials.

In the existing preparation method of the super-hydrophobic material, air spraying is widely applied due to simple process. The air spraying is to suck the slurry by negative pressure generated by the ejection of compressed air from a nozzle, then to mix the slurry with the compressed air sufficiently, and then to blow out the slurry from the nozzle to form a spray to be sprayed onto the surface of the object to be coated, thereby forming a coating film. The air atomization effect of air spraying is insufficient, the fog drop particles are larger, the obtained super-hydrophobic microstructure is not fine and compact enough, and the mechanical durability and the air layer stability are insufficient. It is a great challenge how to obtain a fine, dense, strong micro-nano secondary structure by adjusting the deposited droplet parameters.

Disclosure of Invention

The invention provides a super-hydrophobic coating with a lotus leaf-like structure and high robustness, and a preparation method and application thereof, which are used for overcoming the defects of insufficient fineness of a super-hydrophobic microstructure, insufficient air layer stability and the like in the prior art.

In order to achieve the aim, the invention provides a preparation method of a lotus leaf structure imitated super-hydrophobic coating with high robustness, which comprises the following steps:

s1: dispersing the nano particles in a fluorosilane solution, regulating the pH to 4-6 by using an acidic aqueous solution, heating and stirring to obtain hydrophobic nano particles;

s2: weighing resin and the hydrophobic nano particles according to the mass ratio of 1:0.15-1, dispersing the resin and the hydrophobic nano particles in an organic solvent, adding an auxiliary agent, and stirring and uniformly mixing to obtain a mixed solution;

s3: and (3) taking the mixed solution as a raw material, forming a coating layer on the base material by utilizing electrostatic spraying, and heating and curing to obtain the super-hydrophobic coating.

In order to achieve the above purpose, the invention also provides a super-hydrophobic coating with a lotus leaf-like structure and high robustness, which is prepared by the preparation method; the surface of the super-hydrophobic coating is provided with conical micron-sized protrusions, and the surface of the conical micron-sized protrusions is provided with a nanoscale coarse structure; the contact angle between the nanoscale coarse structure and water is 150-170 degrees.

In order to achieve the above purpose, the invention also provides an application of the super-hydrophobic coating with the lotus leaf-like structure with high robustness, and the super-hydrophobic coating prepared by the preparation method or the super-hydrophobic coating is applied to underwater drag reduction, pollution prevention, corrosion prevention and biomembrane adhesion prevention.

Compared with the prior art, the invention has the beneficial effects that:

1. according to the preparation method of the high-robustness lotus leaf-like structure superhydrophobic coating, the coating is prepared through electrostatic spraying of the mixed liquid of resin and particles, fine spraying can be spontaneously deposited and assembled into pyramid-shaped conical micron-sized protrusions through regulation and control of electrostatic force and assembly, the surfaces of the conical micron-sized protrusions are provided with nano-sized coarse structures, and the nano-sized coarse structures and the fine spraying and the pyramid-shaped micron-sized protrusions form the micro-nano secondary coarse structures necessary for superhydrophobic. Because the micro-nano structure prepared by the traditional method for preparing the super-hydrophobic fabric by electrostatic spinning or preparing the super-hydrophobic coating by air spraying is difficult to accurately regulate and control, the invention adopts high-voltage electrostatic spraying as a preparation means, not only can atomize liquid drops to 20-100nm scale, but also can generate assembled stacking under the regulation and control of an electric field in the spray flight deposition process, and finally form a fine micro-structure, and the whole process is efficient and rapid, and the high-durability super-hydrophobic surface with the length of about 10cm multiplied by 10cm can be prepared only about 10 min. The preparation method provided by the invention is simple and feasible, requires shorter time and is suitable for large-area industrial production.

2. The preparation method provided by the invention adopts a high-voltage electrostatic spraying technology, the high-voltage static makes the resin slurry atomized into charged fog drops, and the agglomerated hydrophobic nano particles are wrapped in the charged fog drops. In the process of flying the charged fog drops to the receiving plate in a high-voltage electric field, the solvent is continuously evaporated, and the interior of the fog drops is split into smaller fog drops (20-100 nm) under the action of the repulsive force of the electric field. These droplets are continuously torn into tiny droplets, and finally are deposited and stacked on a receiving plate to form pyramid-shaped conical protrusions. The surface of the bulges is provided with nano bulges formed by stacking atomized liquid drops, and a compact coating with good interface bonding is formed after solidification. The hydrophobic nanoparticles serve as micro-nano hierarchical structures required for constructing superhydrophobic and can enhance the resin.

3. According to the preparation method provided by the invention, resin with good bonding performance is selected, so that on one hand, nano hydrophobic nano particles can be firmly bonded together to form stable high-strength microprotrusions; on the other hand, the coating and the substrate can be firmly bonded together, so that the coating has good adhesion, and the mechanical property and mechanical strength of the whole coating can be improved.

4. The nano particles required by the super-hydrophobic coating prepared by the invention can be adjusted according to functional requirements, for example, iron oxide can be used for endowing the coating with photo-thermal effect, and zinc oxide or titanium oxide can be used for endowing the coating with photo-catalytic property. The functional characteristics of the particles are compounded with the superhydrophobic property, so that the application of the high-durability superhydrophobic material prepared by the invention can be further widened.

5. The super-hydrophobic coating with the high-robustness lotus-leaf-like structure has the characteristics of high robustness and high compactness, so that the super-hydrophobic coating has good air layer stability, and an air layer is kept from being pierced when the super-hydrophobic coating interacts with high-pressure water. The method has important significance for underwater drag reduction, corrosion prevention, biomembrane adhesion prevention and other applications.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.

FIG. 1 SEM photograph of the coating prepared in example 1;

FIG. 2 is a photograph of a contact angle test of the coating prepared in example 1;

FIG. 3 is a graph of the contact angle and rolling angle of the coating prepared in example 1 as a function of the number of tape sticks;

FIG. 4 is a plot of contact angle and roll angle of the coating prepared in example 1 over time;

FIG. 5 is a contact angle test photograph of the coating prepared in example 1 after 30 minutes of ultrasound;

FIG. 6 is a photograph of a superhydrophobic display of the coating prepared in example 1 after withstanding a hydrostatic pressure of 300 m;

FIG. 7 SEM photograph of the coating prepared in example 2;

fig. 8 SEM photograph of the coating prepared in comparative example 1;

FIG. 9 is a photograph of the surface being fully wetted after the coating prepared in comparative example 1 has been subjected to a water depth pressure of 300 m;

FIG. 10 is a graph showing the effect of atomized particles obtained in comparative example 2;

fig. 11 SEM photograph of the coating prepared in comparative example 3;

fig. 12 SEM photograph of the coating prepared in comparative example 6.

The upper right corner illustration in fig. 1 and 8 is a corresponding partial enlarged view.

The achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In addition, the technical solutions of the embodiments of the present invention may be combined with each other, but it is necessary to be based on the fact that those skilled in the art can implement the technical solutions, and when the technical solutions are contradictory or cannot be implemented, the combination of the technical solutions should be considered as not existing, and not falling within the scope of protection claimed by the present invention.

The drugs/reagents used are all commercially available without specific description.

The invention provides a preparation method of a lotus leaf structure imitated super-hydrophobic coating with high robustness, which comprises the following steps:

s1: dispersing nano particles in a fluorosilane solution, adjusting the pH to 4-6 by using an acidic aqueous solution to hydrolyze the fluorosilane, and heating and stirring to fully react the fluorosilane with the nano particles to obtain the hydrophobic nano particles.

Step S1 is the hydrophobic modification of the nanoparticles.

Preferably, the nanoparticle has a particle size of 4 to 500nm in order to construct a micro-nano hierarchical structure. Too small particles are too costly and too large to disperse into droplets with dimensions smaller than air-sprayed droplets, failing to obtain the desired structure.

Preferably, the nanoparticle is at least one of aluminum oxide, ferric oxide, zinc oxide, cerium oxide, titanium dioxide, and silicon dioxide. The particles can be subjected to hydrophobic modification, play a role in constructing a super-hydrophobic microstructure, and can be selected according to functional requirements.

Preferably, the concentration of fluorosilane in the fluorosilane solution is 1%. The solvent of the fluorosilane solution is an alcohol organic solvent, preferably ethanol. The fluorosilane is one of heptadecafluorodecyl trimethoxysilane, tridedecafluorooctyl triethoxysilane, (3, 3-trifluoropropyl) triethoxysilane and (3, 3-trifluoropropyl) methyldimethoxy silane; the mass ratio of the nano particles to the fluorosilane is 1:0.1-2.

Preferably, the concentration of the acidic aqueous solution is 30-70%; the acid in the acidic aqueous solution is one of hydrochloric acid, acetic acid, nitric acid and sulfuric acid.

Preferably, the temperature of the heating and stirring is 50-70 ℃ and the time is 1-3 h. So that the hydrophobic modification is sufficiently performed.

S2: weighing resin and the hydrophobic nano particles according to the mass ratio of 1:0.15-1, dispersing the resin and the hydrophobic nano particles in an organic solvent, adding an auxiliary agent, and stirring and uniformly mixing to obtain a mixed solution.

The resin is selected from a wide range of soluble thermosetting resins or thermosetting resins, such as epoxy resins, polyurethane resins, polyacrylic resins, phenolic resins, and polystyrene resins.

The choice of organic solvent requires that it dissolves the resin and has good dispersion of the hydrophobic nanoparticles. Preferably one of ethyl acetate, acetone, butanone and N, N-Dimethylformamide (DMF).

The auxiliary agent comprises a curing agent or other functional auxiliary agents, and in order to obtain a coating which can meet the practical application working conditions in industrial application, other auxiliary agents can be added to realize environmental resistance, functionality, safety and the like which are possibly needed.

Preferably, the mass ratio of the hydrophobic nano particles to the organic solvent is 1:30-80, so as to facilitate uniform dispersion of the hydrophobic nano particles.

Preferably, the parameters of the electrostatic spray are: the inner diameter of the needle head is 0.1-0.5 mm; the propulsion speed is 0.01-6 mm/h; the voltage difference between the two ends is 8-20 kV; the distance between the receiving base material and the spray head is 5-40 cm; the ambient humidity is 20-70%; the ambient temperature is 20-80 ℃; the spraying time is 5-60 min. The coating prepared under proper conditions has better mechanical property and hydrophobic property.

The propelling speed is preferably 1-5 mm/h; the distance between the receiving substrate and the spray head is preferably 10-20 cm.

According to the preparation method of the super-hydrophobic coating with the lotus leaf-like structure with high robustness, the super-hydrophobic coating is prepared by spraying the mixed liquid of resin and particles through high-voltage static electricity, and the surface of the coating is provided with the lotus leaf-like firm conical micron-sized protrusions and the nanoscale coarse structures. The high-voltage static in the spraying process atomizes the liquid drops into charged fog drops with the particle size of 20-100nm, and the charged fog drops are assembled and stacked under the action of high-voltage electric field force to form the compact high-robustness superhydrophobic coating. The prepared coating has excellent superhydrophobicity and air layer stability, and still maintains good superhydrophobicity under the effects of ultrasonic action and high static water pressure. Can be applied to the fields of waterproofing, antifouling, corrosion prevention, biomembrane adhesion prevention and the like of marine equipment such as ships, submarines, drilling platforms and the like.

The invention also provides a high-robustness lotus leaf structure imitated super-hydrophobic coating, which is prepared by the preparation method; the surface of the super-hydrophobic coating is provided with conical micron-sized protrusions, and the surface of the conical micron-sized protrusions is provided with a nanoscale coarse structure; the contact angle between the super-hydrophobic coating and water is 150-170 degrees.

The invention also provides an application of the super-hydrophobic coating with the lotus leaf-like structure and high robustness, and the super-hydrophobic coating prepared by the preparation method or the super-hydrophobic coating is applied to underwater drag reduction, pollution prevention, corrosion prevention and biomembrane adhesion prevention.

Such as submarine of ocean, underwater drag reduction of ship, antifouling and anticorrosion, and biomembrane adhesion prevention.

Example 1

The embodiment provides a preparation method of a lotus leaf structure imitated super-hydrophobic coating with high robustness, which comprises the following steps:

s1: the E-51 epoxy resin is subjected to hydrophobic modification by a method described in patent CN 109836557A to obtain hydrophobic epoxy resin for standby.

1g of silica nanoparticles are dispersed in an ethanol solution of fluorosilane, 50% acetic acid aqueous solution is added to adjust the pH to 4-6, and the mixture is stirred for 2 hours at 60 ℃ to obtain hydrophobic silica particles.

S2: 2g of hydrophobic epoxy resin, 0.68g of D230 curing agent and 1g of hydrophobic silica particles were dispersed in 50g of ethyl acetate solution, and stirred sufficiently by a magnetic stirrer for 10 minutes to uniformly mix the components, to obtain a mixed solution.

S3: the mixed solution is placed in a 10mL injector, a needle head with the model of 22G is used by an electrostatic spinning device, the propulsion speed is set to be 0.2mm/h, the voltage is adjusted to 18kV, the solution is sprayed out in a mist form, and the surface of the aluminum foil receiving surface with the distance of 10cm is uniformly covered. Humidity was controlled at 40% and temperature at 25 ℃. After 10min, the aluminum foil is taken down, and the temperature is kept at 80 ℃ for 2h, and then kept at 100 ℃ for 1h, so that the super-hydrophobic coating with the high-robustness lotus-leaf-like structure, which has a firm, fine and compact micro-nano secondary coarse structure, is obtained, as shown in figure 1.

The super-hydrophobic coating prepared in this example was tested for wettability by using an OCAH 200 full-automatic microscopic droplet wettability meter from DataPhysics, USA, and water was selected as the test droplet, the droplet volume was 5. Mu.L, and the average was obtained five times. The superhydrophobic coating prepared in this example shows superhydrophobicity, the water contact angle reaches 158 °, and the rolling angle reaches 4 °, as shown in fig. 2.

The surface of the superhydrophobic coating was adhered using VHB tape of model 3m 4951 according to standard ASTM D3359 and then peeled off in a 45 ° direction, and the contact angle and the rolling angle of the surface were measured every 50 cycles of test, and the test results are shown in fig. 3. As can be seen from fig. 3, the superhydrophobic coating prepared by the present invention can endure 1000 adhesion cycles while maintaining superhydrophobic performance. The fine spray obtained by the high-voltage electric field of the invention can accelerate the flight and deposition in the electric field, so that good fusion is generated between particles of the coating and between the particles and the substrate, gaps between coarse structures are filled up due to the action of electrostatic repulsion, and the high-robustness compact durable superhydrophobic coating is obtained.

The superhydrophobic coating prepared in this example was placed in an ultrasonic cell disperser (VOSHIN-1500R) at intervals of 4s and ultrasound for 2s. The roll angle and contact angle were measured after 5 minutes of continuous ultrasound. The test results are shown in fig. 4, and it can be seen from fig. 4 that the super-hydrophobic coating prepared in this example has a contact angle and a rolling angle of 151 ° and 8 ° respectively after ultrasonic treatment for 25 min. The superhydrophobic character was lost after 30min of ultrasound, and the contact angle and the roll angle were 149 ° (as shown in fig. 5) and 13.5 °, respectively.

The superhydrophobic coating prepared in this example was placed in an autoclave, water was added without coating, the coating was pressurized to 3MPa after sealing, and 1000kg/m was taken according to the pressure formula p=pgh (P deep water pressure; P is the density of water) ³ The method comprises the steps of carrying out a first treatment on the surface of the g is gravity acceleration, 10m/s is taken ² The method comprises the steps of carrying out a first treatment on the surface of the h is the water depth, and the combat submergence depth of a general submarine is taken to be 300m. ) This reaches a hydrostatic pressure of 300m depth and the coating remains superhydrophobic after removal, as shown in fig. 6. As can be seen from fig. 6, the superhydrophobic coating prepared in this example has a stable air layer due to its dense and fine micro-nano structure, and does not damage the superhydrophobic structure under high hydrostatic pressure. The stable air layer characteristic is used for drag reduction of water flow, corrosion resistance under water, biomembrane adhesion prevention and the likeThe field has important application.

Examples 2 to 7

The preparation process mainly comprises the regulation and control of the size of spray liquid drops and the evaporation rate of the organic solvent.

The preparation method of the lotus leaf-like structure superhydrophobic coating with high robustness is provided in the embodiment, the technological parameters and the contact angle of the prepared sample are shown in table 1, and other preparation processes are the same as in embodiment 1.

The process parameters have a significant impact on the droplet state and deposition process, wherein the voltage, humidity and concentration of hydrophobic particles have a significant impact on the deposition effect. As is evident from the comparison of examples 1 to 7, the voltage must reach a certain intensity in order to achieve a good atomization effect. It can be seen from examples 1 to 3 that the lower the voltage, the worse the atomizing effect, the larger the atomized droplets, resulting in deterioration of superhydrophobicity. Meanwhile, the evaporation rate of the organic solvent is affected by the environmental humidity of the spray, and it can be seen from examples 1, 4 and 5 that too high humidity causes slow evaporation of the organic solvent, which is unfavorable for forming a good coarse structure. The hydrophobic nanoparticles have a great influence on the formation of micro-nano hierarchical structures, and as can be seen from examples 1, 6 and 7, the greater the concentration of the hydrophobic nanoparticles, the greater the roughness of the structure, and the easier the formation of good superhydrophobicity. The electron microscope photographs of examples 1 and 2 are shown in fig. 1 and 7, respectively, and it can be seen from the figures that the present invention obtains an ideal lotus leaf like structure through a high voltage electrostatic process, which includes micrometer-scale protrusions, and the surface of the micrometer-scale protrusions can see a nanometer-scale coarse structure (shown in fig. 1) on which atomized mist droplets are deposited, but when the voltage of key conditions in the process of the present invention is reduced, the obtained coating particles are not tightly combined due to the deterioration of the atomization effect, the gaps between the particles are larger, and the coating layer without good atomization effect cannot obtain the high-robustness lotus leaf preventing structure (shown in fig. 7) mentioned in the present invention. In addition, the contact angle characterization is carried out on the super-hydrophobic coatings obtained by different parameters, and the super-hydrophobic coatings obtained by the examples 2, 4 and 7 are very loose and fragile due to the combination of particles, and the coating is found to fall off in a large area after 1-2 times of adhesive tape adhesion, so that the super-hydrophobic performance is lost.

Table 1 process parameters and performance tables

Process parameters	Voltage (kV)	Humidity (%)	Resin particle ratio	Contact angle (°)
					Example 2	15	40	1:0.5	151.6
Example 3	12	40	1:0.5	132.3
					Example 4	18	60	1:0.5	152.2
Example 5	18	80	1:0.5	144.5
					Example 6	18	40	1:0.2	150.4
Example 7	18	40	1:0.15	134.3

Example 8

s1: the E-51 epoxy resin was hydrophobically modified by the method described in patent CN 109836557A for later use.

Dispersing 2g of ferroferric oxide nano particles in an ethanol solution of fluorosilane, adding a 70% acetic acid aqueous solution to adjust the pH to 4-6, and stirring for 1h at 70 ℃ to obtain hydrophobic ferric oxide particles.

S2: 2g of hydrophobic epoxy resin, 0.68g of D230 curing agent and 2g of hydrophobic iron oxide particles are dispersed in 100g of acetone solution, and the mixture is fully stirred for 30min by a magnetic stirrer to uniformly mix the components, so as to obtain a mixed solution.

S3: the mixed solution is placed in a 10mL injector, a needle head with the model of 22G is used by an electrostatic spinning device, the propulsion speed is set to be 0.01mm/h, the voltage is adjusted to 20kV, the solution is sprayed out in a mist form, and the surface of the aluminum foil is uniformly covered on the surface of the aluminum foil. The humidity was controlled at 70% and the temperature at 80 ℃. After 60min, the aluminum foil is taken down, heat preservation is carried out for 2h at 80 ℃, and then heat preservation is carried out for 1h at 100 ℃ to obtain the super-hydrophobic coating with high robustness and lotus leaf-like structure, which has a micro-nano secondary coarse structure with solid, fine and compact comparative hardness.

To demonstrate the advantage of the present invention in obtaining uniform and fine atomized droplets by a high voltage electric field, air-sprayed samples were prepared by the following process.

Firstly, spraying slurry is obtained according to the steps S1 and S2 of the embodiment 1; the slurry was then sprayed onto the substrate at a distance of 20cm using an air spraying device under a pressure of 0.5MPa, and other environmental conditions such as temperature, humidity, etc. were the same as in example 1. The resulting coating had a water contact angle of 156 ° and a roll angle of 4 °. The SEM photograph is shown in fig. 8, and it can be seen from fig. 8 that there are a large number of pores in the coating microstructure, and only loose bonding between particles. The coating was found to peel off by the tape adhesion test (test conditions identical to example 1) at 15 tape adhesion times. Ultrasonic testing in water (test conditions were the same as in example 1) found that after 5min of ultrasonic treatment, the coating was thoroughly immersed in water, lost in superhydrophobic properties, placed in an autoclave filled with water, pressurized to 3MPa, and after 1min of holding, taken out, the surface of the coating was completely wetted, as shown in fig. 9.

Comparative example 2

The experimental conditions of this comparative example were exactly the same as in example 1, and the spraying time was shortened to only 5s, at which time minute mist droplets were deposited on the substrate, and the SEM image thereof was as shown in fig. 10, and it was seen by a scanning electron microscope that the minimum size of mist droplets obtained in this comparative example was only about 20nm, which is the size of a single silica. At the same time, it was found that silica agglomerates with a size of about 100nm, silica agglomerates by resin adhesion. This comparative example can atomize droplets to about 20-100nm using the process of the present invention, which is difficult to achieve in other atomization processes.

Comparative examples 3 to 8

When high-voltage electrostatic spraying is performed, the charging condition of mist drops greatly affects the atomization effect and the deposition morphology of the drops, and the spraying effect changes along with the increase of voltage. When the voltage is smaller, discontinuous large liquid drops are ejected firstly, and the Taylor cone formed at the needle head is ejected under the action of electric field force. When the voltage is increased to a certain extent, the large droplets become fine continuous jets. When the voltage continues to increase, the continuous jet forms discontinuous droplets, but at this time the droplets are larger and cannot form a good deposition effect. A stable spray can be obtained by continuing to increase the voltage. It can be seen that there is a critical voltage for forming a spray and that the solvents of different dielectric constants have different voltages for forming a good atomisation effect. Comparative examples 3 to 8 were prepared in the same manner as in example 1 by applying different voltages to different solvents as shown in Table 2. And observing atomization condition. It can be seen that the critical atomization voltages of acetone and DMF are 20kV and 24kV respectively. SEM photographs of comparative examples 3 and 6 are shown in fig. 11 and 12. As can be seen from comparison of fig. 9 and 10, the larger the dielectric constant of the solvent, the smaller the microstructure of the resulting coating, because the larger the dielectric constant of the solvent, the more the charge of the droplet, and the smaller the droplet size of the droplet split in the electric field.

Table 2 process parameters and performance tables

Process parameters	Solvent(s)	Voltage (kV)	Atomization condition
				Comparative example 3	Acetone (acetone)	20	Good atomization
Comparative example 4	Acetone (acetone)	18	Discontinuous jet
				Comparative example 5	Acetone (acetone)	15	Jet flow
Comparative example 6	DMF	24	Good atomization
				Comparative example 7	DMF	20	Discontinuous jet
Comparative example 8	DMF	16	Jet flow

The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the scope of the invention, and all equivalent structural changes made by the description of the present invention and the accompanying drawings or direct/indirect application in other related technical fields are included in the scope of the invention.

Claims

1. The preparation method of the lotus leaf structure imitated super-hydrophobic coating with high robustness is characterized by comprising the following steps of:

s1: dispersing the nano particles in a fluorosilane solution, regulating the pH to 4-6 by using an acidic aqueous solution, heating and stirring to obtain hydrophobic nano particles; the particle size of the nano particles is 4-500 nm; the nano particles are at least one of aluminum oxide, ferric oxide, zinc oxide, cerium oxide, titanium dioxide and silicon dioxide; the temperature of the heating and stirring is 50-70 ℃ and the time is 1-3 h; the concentration of fluorosilane in the fluorosilane solution is 1%; the solvent of the fluorosilane solution is an alcohol organic solvent; the fluorosilane is one of heptadecafluorodecyl trimethoxysilane, tridedecafluorooctyl triethoxysilane, (3, 3-trifluoropropyl) triethoxysilane and (3, 3-trifluoropropyl) methyldimethoxy silane; the mass ratio of the nano particles to the fluorosilane is 1:0.1-2;

s3: forming a coating layer on a substrate by using the mixed solution as a raw material through electrostatic spraying, and heating and curing to obtain a super-hydrophobic coating; the surface of the super-hydrophobic coating is provided with conical micron-sized protrusions, and the surface of the conical micron-sized protrusions is provided with a nanoscale coarse structure; the contact angle between the super-hydrophobic coating and water is 150-170 degrees;

the parameters of the electrostatic spraying are as follows: the inner diameter of the needle head is 0.1-0.5 mm; the propulsion speed is 0.01-6 mm/h; the voltage difference between the two ends is 8-40 kV; the distance between the receiving base material and the spray head is 5-40 cm; the ambient humidity is 20-70%; the ambient temperature is 20-80 ℃; the spraying time is 5-60 min.

2. The method according to claim 1, wherein in step S1, the acidic aqueous solution has a concentration of 30 to 70%; the acid in the acidic aqueous solution is one of hydrochloric acid, acetic acid, nitric acid and sulfuric acid.

3. The preparation method according to claim 1, wherein in the step S2, the mass ratio of the hydrophobic nanoparticle to the organic solvent is 1:30-80.

4. The lotus leaf structure imitated super-hydrophobic coating with high robustness is characterized by being prepared by the preparation method of any one of claims 1-3.

5. The application of the super-hydrophobic coating with the lotus leaf-like structure with high robustness is characterized in that the super-hydrophobic coating prepared by the preparation method of any one of claims 1 to 3 or the super-hydrophobic coating of claim 4 is applied to underwater drag reduction, pollution prevention, corrosion prevention and biomembrane adhesion prevention.