KR101141619B1 - Method of manufacturing superhydrophobic material and superhydrophobic material manufactured by the method - Google Patents

Abstract

The present invention relates to a method for producing a material having a superhydrophobic surface and to a superhydrophobic material produced thereby, and more particularly, to a method for producing a material having a superhydrophobic surface by an electrochemical method.

Method for producing a material having a superhydrophobic surface according to the present invention comprises the steps of preparing a substrate for the surface treatment; Forming a metal layer on the surface of the substrate by an electrochemical method; Oxidizing the metal layer by an anodizing process to form a metal oxide layer having a nanostructure; And forming a hydrophobic organic monolayer on the surface of the metal oxide layer of the nanostructure.

According to the present invention, a material having a superhydrophobic surface can be manufactured by using an electrochemical method, so that the material can be used for a large area, and there is no need to use expensive equipment or materials, thereby reducing the production cost.

Description

METHOD OF MANUFACTURING SUPERHYDROPHOBIC MATERIAL AND SUPERHYDROPHOBIC MATERIAL MANUFACTURED BY THE METHOD}

The present invention relates to a method for producing a material having a superhydrophobic surface and to a superhydrophobic material produced thereby, and more particularly, to a method for producing a material having a superhydrophobic surface by an electrochemical method.

Hydrophobicity refers to the properties of objects that have no affinity for water. Hydrophobicity is related to the surface tension, an internal force generated by the imbalance of molecular forces when two different materials form contact surfaces with each other. If the force acting between the water and the surface of the object is stronger than the cohesion between the water molecules, the water molecules are strongly attracted to the surface of the object to wet the surface of the object, and in the opposite case, the water does not wet the surface of the object.

This hydrophobicity can be confirmed by measuring the contact angle (θ) between the surface and water measured on the surface of the object, and is said to have superhydrophobicity when the contact angle between the object surface and water exceeds 150 °.

An object having a superhydrophobic surface can effectively prevent surface aggregation of other materials including water due to low surface energy, and has an effect of preventing foreign substances such as human fingerprints and foreign substances such as dust from adhering to the surface. 10 is a diagram showing the self-cleaning effect of the superhydrophobic surface.

Therefore, an object having a superhydrophobic surface can be widely applied to exterior materials of electronic products in which contamination of organic matter is a problem, and building materials where humidity or foreign matter contamination prevention is essential. In particular, if stainless steel having excellent anticorrosive properties, including chromium, has a superhydrophobic surface, the utilization value of exterior materials and building materials of consumer electronics such as refrigerators, mobile phones, and televisions will be greatly increased.

Superhydrophobic objects can be observed in nature, and the lotus leaf is a typical material. 11 is a view showing a lotus leaf having a superhydrophobicity, and through a small photograph of the enlarged surface, it can be confirmed that the superhydrophobicity is affected by the chemical properties and the geometrical characteristics of the surface.

Conventionally, the method used to impart superhydrophobicity to the surface of an object, especially the surface of stainless steel, is typically coated with a fluorine-based hydrophobic material such as titanium or Teflon.

The method of forming titanium or titanium oxide on the double surface has a disadvantage in that the contact angle with water is less than 150 ° and the hydrophobic property is weak, and the manufacturing cost increases due to the vacuum deposition method.

Coating of fluorine-based hydrophobic materials such as Teflon is excellent in superhydrophobic properties, but also due to the vacuum deposition method, the manufacturing cost is very high for large area. In order to solve this problem, a method of coating the surface of an object under normal pressure and the like have been studied, but the problem of manufacturing cost remains in that fluorine-based hydrophobic material itself is an expensive material.

Therefore, it is urgent to develop a technology that gives superhydrophobicity to the surface of a large area at a low price.

The present invention has been invented to solve the above problems, and an object thereof is to provide a method for producing a material having a superhydrophobic surface without using expensive equipment and materials, and a superhydrophobic material produced accordingly.

In order to achieve the above object, a method of producing a material having a superhydrophobic surface according to the present invention comprises the steps of preparing a substrate for surface treatment; Forming a metal layer on the surface of the substrate by an electrochemical method; Oxidizing the metal layer by an anodizing process to form a metal oxide layer having a nanostructure; And forming a hydrophobic organic monolayer on the surface of the metal oxide layer of the nanostructure.

When the nanostructure of the microstructure is formed on the surface of the hydrophobic material, as shown in the right figure of FIG. 9, the contact angle of the hydrophobicity is shown with respect to the nanoscale plane, but as shown in the left figure, Shows a superhydrophobic contact angle.

When the anodic oxidation process is performed on the metal layer formed on the surface of the substrate, spherical metal particles formed on the surface of the substrate grow in a certain direction to form metal oxide nanowires. A metal oxide layer having a fine structure of is formed.

In order to realize superhydrophobicity through the microstructure of the nano-unit, it is preferable to further include the step of forming the micro-united irregularities on the surface of the substrate prior to the step of forming the metal layer on the surface of the substrate, the micro-united irregularities Forming method may be one of a belt polishing process, a semiconductor etching process, a hot embossing process and an imprinting process.

When the metal layer is formed on the entire surface of the substrate in the step of forming the metal layer on the surface of the substrate, problems such as peeling of the metal layer may occur. Therefore, it is preferable to form the metal layer only less than 70% of the surface of the substrate. In this case, the electrochemical method of forming the metal layer on the surface of the substrate may be an electroplating method.

In addition, the substrate may be a variety of materials, but may be steel, and stainless steel is particularly preferable.

Furthermore, the metal material used to form the metal layer may be copper. In this case, the base material on which the copper metal layer is formed may be 0.05 in an oxygen-free KOH electrolyte solution having a concentration of 0.5 to 5 M or an electrolyte solution containing KOH and KCl at a concentration of 0.5 to 5 M. Anodizing for 50 to 2000 seconds at a current density of ~ 5 mA / cm 2 is preferred to form a nanostructured metal oxide layer.

It is preferable to use a thiol or a silane-based compound as a material of the organic monomer layer formed on the metal oxide layer surface. Herein, as the silane-based compound, an R-Si- (OR) _3- based compound, an R-Si-Cl _3- based compound, or a mixture thereof may be used. A representative example of the R-Si- (OR) _3- based compound may include n. Octadecyltrimethoxysilane, n-octadecyltriethoxysilane, n-octyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane and the like, and R-Si-Cl Representative examples of the class ₃ compounds include n-octadecyltrichlorosilane, n-octatrichlorosilane, n-propyltrichlorosilane, and the like.

And the superhydrophobic material according to the present invention, the base material of various materials; A nanostructure metal oxide layer formed on the surface of the substrate by an electrochemical method and oxidized by an anodization method; And a hydrophobic organic monomolecular layer formed on the surface of the metal oxide layer, wherein the contact angle with respect to water is 150 ° or more.

At this time, the metal oxide layer preferably covers less than 70% of the surface of the substrate, and the metal oxide layer is preferably copper oxide.

And the substrate may be steel, in particular stainless steel is preferred.

In addition, it is preferable to use a thiol or a silane-based compound as a material of the organic monomer layer formed on the surface of the metal oxide layer. Herein, as the silane-based compound, an R-Si- (OR) _3- based compound, an R-Si-Cl _3- based compound, or a mixture thereof may be used. A representative example of the R-Si- (OR) _3- based compound may include n. Octadecyltrimethoxysilane, n-octadecyltriethoxysilane, n-octyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, and the like, and R-Si-Cl ₃ Representative examples of the class compounds include n-octadecyltrichlorosilane, n-octatrichlorosilane, n-propyltrichlorosilane, and the like.

According to the present invention, a material having a superhydrophobic surface is manufactured using an electrochemical method, so that it can be used for a large area material, and there is no need to use expensive equipment or materials, thereby reducing the production cost.

The present invention will now be described in detail with reference to the accompanying drawings. The thickness or size of the membrane in the drawings is exaggerated for clarity.

1 is a process diagram showing an embodiment of a method for producing a material having a superhydrophobic surface according to the present invention, Figures 2a to 2d is a view showing an overview according to the process of FIG.

First, the substrate 10 for surface treatment is prepared as shown in FIG. 2A. In this embodiment, a stainless steel having anticorrosive properties by adding chromium was used as a substrate. Stainless steels have various products depending on the last surface treatment process in the steel sheet manufacturing process, commercially available stainless steels were used.

3A and 3B are optical micrographs of two kinds of stainless steel surfaces used in this example. Figure 3a is the surface of the No.2B product of commercially available stainless steel, Figure 3b shows the surface of stainless steel 304 No.4 polished commercially available stainless steel 304 product with an abrasive belt of 150 to 180 particle size. In both pictures, we can see that both products have dozens of microscopic stripes. The surface irregularities of the micro units facilitate the adhesion of the metal particles when the metal layer is formed by the electrochemical method, and also advantageously work to form the nanostructure metal oxide layer by the anodization method. In particular, in the case of the stainless steel shown in Figure 3b it can be seen that by forming artificially irregular micro-units on the surface of the stainless steel, a wide and deep string pattern is formed.

4A to 4D illustrate the results of forming irregularities in micro units on the surface of the substrate by an artificial method in addition to the above-described method of using the polishing belt. FIG. 4A is a view showing a cross section in which micro irregularities are formed through a lithography process or an etching process commonly used in a semiconductor, and FIG. 4C is a SEM photograph of the surface of a stainless steel having irregularities formed through such a semiconductor process. 4B is a view showing a cross section in which micro irregularities are formed by using an imprinting or hot embossing process, and FIG. 4D is a SEM photograph of the surface of a stainless steel having irregularities formed through an imprinting or hot embossing process. An imprinting or hot embossing process is a method of forming a micro-sized shape on an organic material by coating a photosensitive organic material on a substrate and pressing it strongly with a mold.

Next, as shown in FIG. 2B, the metal layer 20 is formed on the surface of the stainless steel substrate 10 having the unevenness of micro units formed on the surface thereof by an electrochemical method. A representative electrochemical method of forming the metal layer 20 is electroplating. Electroplating can deposit a variety of metals on the surface, and is a low cost and fast method even in large areas. In the present invention, a known plating technique may be used as it is, and in this embodiment, copper is used as the metal material. However, when the metal layer 20 covers the entire surface of the substrate 10, problems such as loss of the texture of the substrate 10 and peeling of the metal layer 20 may occur. Accordingly, the metal layer 20 was formed to cover a portion of the surface of the substrate 10, that is, less than 70% of the substrate surface area. This plating area can be easily adjusted by controlling the plating time and the current density.

FIG. 5 is an electron micrograph of the surface of the stainless steel substrate 10 having the copper metal layer 20 formed by plating. Substrate 10 was used by belt polishing stainless steel 304 No. 4 having a surface area of 3 ~ 10 ㎠, and washed in acetone-ethanol-water for 5 minutes under ultrasonic vibration conditions before plating, and then dried on a 70 ℃ hot plate It was. The copper plating solution was prepared by dissolving 150 g copper sulfate, 120 mg copper chloride and 60 ml sulfuric acid in a 1 liter aqueous solution. A 3 mm diameter copper rod used as a copper ion source was also immersed in a hydrochloric acid aqueous solution for about a few minutes to remove foreign substances on the surface. As a result of plating for 100 seconds at a current density of 5 mA / cm 2 under agitation conditions of room temperature, it can be seen that copper particles were deposited along the stripe direction formed by belt polishing. As a result of various experiments, it was confirmed that the plating should be performed for 50 to 600 seconds at a current density of 1 to 10㎃ / ㎠ in order to plate the desired copper particles.

Next, as shown in Figure 2c, by oxidizing the copper metal layer 20 using an anodizing process to form a metal oxide layer 30 of the nanostructure. When the anodizing process is performed on the metal layer 20, the metal particles grow in a predetermined direction to form metal oxide nanowires, and as the nanowires grow, many pores are formed in the metal oxide, thus completing the metal oxide layer ( 30) has a nanostructured microstructure. In order to form an appropriate microstructure of nanounits, electrochemical anodic oxidation should be performed under suitable electrolyte solution and current density conditions. In the case of copper particles, 0.5-5 M KOH electrolyte solution or 0.5-5 M It was confirmed that the anodizing process should be performed for 50 to 2000 seconds at a current density of 0.05 to 5 mA / cm 2 in an electrolyte solution containing KOH and KCl in various ratios.

6 is a SEM photograph of the surface of the metal oxide layer 30 in which the nanostructure is formed through an anodization process. Anodization was performed for 300 seconds at a current density of 1 mA / cm 2 in a 2 M KOH electrolyte solution, and the surface of the copper metal oxide layer 30 in which the nanowires and pores were formed was confirmed.

Finally, as shown in FIG. 2D, the hydrophobic organic monomer layer 40 is formed on the metal oxide layer 30 having the nanostructure. As the hydrophobic organic material, thiol or a silane compound may be used. Thiol-based compounds and silane-based compounds spontaneously form monomolecular layers simply by immersing a sample of metal oxides on the surface for a predetermined time. The reason for such spontaneous formation is that thiol (-SH) group in the case of thiol-based compound is assumed to form a strong covalent bond with the hydroxy (-OH) group present in a large amount on the metal oxide surface. Silane-based compounds are also known to have strong covalent bonds with hydroxy groups. In order to improve the hydrophobicity of thiol or silane based compounds, it is advantageous for the other end of the compound to have a hydrocarbon or fluorocarbon group with a generally linear structure. Thus, instead of octane thiol having 8 carbons, compounds such as dodecyloctane thiol having 18 carbons and the like will be advantageous. However, when the number of carbon is increased, there is a disadvantage that the solubility in the polar solvent is reduced to be carried out at a temperature of about 40 ℃. The thiol compound is generally used in ethanol so that the thiol compound is about 2 ~ 10mM. In order to form the organic monomolecular layer, it is known that a monomolecular film having good properties is formed by putting it in a solution prepared for a substrate for about 10 to 24 hours, but the process is too late when performed for 10 to 24 hours. In this experiment, when the copper metal oxide layer was formed, it was confirmed that superhydrophobicity appeared even after soaking in the octane thiol solution for about 5 minutes.

FIG. 7 is a photograph showing a spontaneous organic monomolecular layer 40 formed by immersing a sample in which a nanostructured copper metal oxide layer 30 is formed on a surface in an octane thiol solution for about 10 minutes, and FIG. 8 is a superhydrophobic characteristic of the sample. In order to check, the contact angle of the surface and the water droplets is measured. The measured contact angle is about 160 °, and it can be seen that the material prepared according to the present embodiment shows superhydrophobicity.

In the above, the present invention has been shown and described with respect to certain preferred embodiments. However, the present invention is not limited only to the above-described embodiment, and those skilled in the art to which the present invention pertains can make various changes without departing from the technical spirit of the present invention. Therefore, the scope of the present invention should not be limited to the specific embodiments, but should be construed as defined by the appended claims.

1 is a process diagram showing an embodiment of a method for producing a material having a superhydrophobic surface according to the present invention.

 2A-2D show an overview according to the process of FIG.

3A and 3B are optical micrographs of the stainless steel surface used in this example.

4A to 4D are diagrams showing the results of forming irregularities in micro units on the surface of a substrate by an artificial method.

5 is a surface electron micrograph of a stainless steel substrate on which a copper metal layer is formed.

6 is a SEM photograph of the surface of the metal oxide layer formed with nanostructures.

Figure 7 is a photograph showing the appearance of spontaneous organic monolayer.

8 is a photograph measuring the contact angle of the water droplets and the sample prepared according to the present embodiment.

9 shows superhydrophobicity according to surface microstructure.

10 shows the self-cleaning effect of a superhydrophobic surface.

11 is a view showing a magnified photograph of a lotus leaf having superhydrophobicity and its surface;

Description of the Related Art

10: base material 20: metal layer

30: metal oxide layer 40: hydrophobic organic monomer layer

Claims (20)

Preparing a substrate for surface treatment; Forming a metal layer on the surface of the substrate by an electrochemical method; Oxidizing the metal layer by an anodizing process to form a metal oxide layer having a nanostructure; And Method of producing a material having a super hydrophobic surface comprising the step of forming an organic monomer layer of a thiol or silane-based compound on the surface of the metal oxide layer of the nanostructure. The method of claim 1, Prior to forming the metal layer on the surface of the substrate, the method of producing a material having a superhydrophobic surface, characterized in that it further comprises the step of forming the irregularities of the micro unit on the surface of the substrate. 3. The method of claim 2, The method of forming the irregularities in micro units on the surface of the substrate is one of a belt polishing process, semiconductor etching process, hot embossing process and imprinting process, characterized in that the manufacturing method of the material having a super hydrophobic surface. The method according to any one of claims 1 to 3, In the step of forming a metal layer on the surface of the substrate, wherein the metal layer covers less than 70% of the surface of the substrate. The method according to any one of claims 1 to 3, A method of producing a material having a superhydrophobic surface, characterized in that the electrochemical method for forming a metal layer on the surface of the substrate is an electroplating method. The method according to any one of claims 1 to 3, A method for producing a material having a superhydrophobic surface, characterized in that the substrate is a stainless steel material. The method according to any one of claims 1 to 3, And a metal material for forming the metal layer is copper. The method of claim 7, Forming the metal oxide layer of the nanostructure is a positive electrode for 50 to 2000 seconds at a current density of 0.05 ~ 5 ~ / ㎠ in a 0.5 ~ 5M KOH electrolyte solution or 0.5 ~ 5M KOH and KCl electrolyte solution A method for producing a material having a superhydrophobic surface, characterized by performing an oxidation process. delete The method of claim 1, A method for producing a material having a superhydrophobic surface, wherein the silane-based compound used in the organic monolayer is an R-Si- (OR) _3- based compound R-Si-Cl ₃ -based compound or a mixture thereof. The method of claim 10, The R-Si- (OR) ₃ series compounds include n-octadecyltrimethoxysilane, n-octadecyltriethoxysilane, n-octyltriethoxysilane, n-propyltrimethoxysilane and n-propyltri A method for producing a material having a superhydrophobic surface, characterized in that one or a mixture thereof selected from the group consisting of ethoxysilanes. The method of claim 10, The R-Si-Cl ₃ series compound is superhydrophobic, characterized in that one or a mixture thereof selected from the group consisting of n-octadecyltrichlorosilane, n-octatrichlorosilane and n-propyltrichlorosilane. Method for producing a material having a surface. materials; A nanostructure metal oxide layer formed by oxidizing a metal layer coated on the surface of the substrate by an electrochemical method by an anodizing method; And A superhydrophobic material comprising an organic terminal layer of a thiol or silane compound formed on the surface of the metal oxide layer, the contact angle to water is 150 ° or more. The method of claim 13, And the metal oxide layer covers less than 70% of the surface of the substrate. The method of claim 13, The superhydrophobic material, characterized in that the substrate is stainless steel. The method of claim 13, Superhydrophobic material, characterized in that the metal oxide layer is a copper oxide. delete The method of claim 13, A superhydrophobic material, wherein the silane-based compound used in the organic monolayer is an R-Si- (OR) _3- based compound R-Si-Cl _3- based compound or a mixture thereof. The method of claim 18, The R-Si- (OR) ₃ series compounds include n-octadecyltrimethoxysilane, n-octadecyltriethoxysilane, n-octyltriethoxysilane, n-propyltrimethoxysilane and n-propyltri Superhydrophobic material, characterized in that one or a mixture thereof selected from the group consisting of ethoxysilane. The method of claim 18, The R-Si-Cl ₃ series compound is superhydrophobic, characterized in that one or a mixture thereof selected from the group consisting of n-octadecyltrichlorosilane, n-octatrichlorosilane and n-propyltrichlorosilane. material.

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