WO2021141109A1

WO2021141109A1 - Super-water-repellent surface member, metal copper surface member, and method for manufacturing same

Info

Publication number: WO2021141109A1
Application number: PCT/JP2021/000464
Authority: WO
Inventors: 浩樹幅▲ざき▼; 春宇朱; 涼太山本; 瑞傑朱
Original assignee: 国立大学法人北海道大学
Priority date: 2020-01-09
Filing date: 2021-01-08
Publication date: 2021-07-15
Also published as: JPWO2021141109A1

Abstract

The present invention pertains to: a super-water-repellent surface member that includes, on a substrate surface, a metal copper nanowire layer and an organic matter coating layer in this order, the organic matter coating layer being fixed to the metal copper nanowire layer via an affinity group for metal copper; a metal copper surface member having a metal copper nanowire layer on the substrate surface; and a method for manufacturing the metal copper surface member and the super-water-repellent surface member. The present invention can provide a novel technology with which, on a surface of a member having a copper base or a copper surface, a water film can be prevented from forming and water drops generated from condensed water can be autonomously removed.

Description

Superhydrophobic surface members, metallic copper surface members and their manufacturing methods

The present invention relates to a superhydrophobic surface member, a metallic copper surface member, and a method for producing the same.
Cross-reference to related applications This application claims the priority of Japanese Patent Application No. 2020-2362 filed on January 9, 2020, the entire description of which is incorporated herein by reference in particular.

Copper has high thermal conductivity and is widely used in condensers and heat exchangers. However, when a water film is formed on the copper surface due to dew condensation or the like, the thermal conductivity is lowered and the efficiency of heat exchange is greatly lowered. In order to further improve the efficiency of heat exchange, it is necessary to suppress the formation of this water film. It is desired to continuously remove the water that has aggregated on the copper surface, and it has been reported that the thermal efficiency is improved 5 to 7 times by aggregating the water in the form of water droplets and dropping it by gravity [Non-Patent Documents]. 1]. However, further improvement is desired.

As a method of converting a water film into water droplets and easily dropping the water film, the use of a superhydrophobic surface can be considered. As a method for obtaining a super-water-repellent copper surface _{, formation of Cu (OH) 2} or CuO nanowire surface by anodic oxidation in an aqueous NaOH solution of copper and organic coating on the nanowire surface are known [Non-Patent Document 2]. _{Further, it is known that a Cu (OH) 2} nanowire layer or a CuO nanowire layer is formed on a copper surface in a mixed aqueous solution of NaOH and (NH ₄ ) 2S ₂ O ₈ and an organic coating is applied to the nanowire layer [Non-Patent Documents]. 3] However, in these configurations, although the superwater repellency was exhibited, the water aggregated on the copper surface was not sufficiently removed.

Non-Patent Document 1: J. W. Rose, Proc. Inst. Mech. Eng. , Part A: J.M. Power Eng. 216, 115 (2002)
Non-Patent Document 2: W. Jiang, J.M. He, F. Xiao, S.M. Yuan, H.M. Lu, B. Liang, Industrial & Engineering Chemistry Research 54 (27) (2015) 6874-6883.
Non-Patent Document 3: J. Mol. Feng, Z. Qin, S.M. Yao, Langmuir, 28 (2012) 6067-6075
The entire description of Non-Patent Documents 1 to 3 is incorporated herein by reference in particular.

An object of the present invention is to provide a new technique capable of suppressing the formation of a water film on the surface of a metal copper base material or a member having a metal copper surface and autonomously removing water droplets generated from agglomerated water.

_{The present inventors obtained a metallic copper surface member obtained by reducing a Cu (OH) 2} nanowire layer produced on the surface of a copper plate to form a metallic copper nanowire layer, and further provided a predetermined organic coating layer on the metallic copper surface member. We have succeeded in providing a super-water-repellent surface member in which the formation of a water film on the surface is suppressed and the water droplets generated from the aggregated water generated on the surface can be easily removed autonomously.

The present invention is as follows.
[1]
A superhydrophobic surface member having a metallic copper nanowire layer and an organic material coating layer on the surface of the base material in this order.
The superhydrophobic surface member, wherein the organic coating layer is immobilized on the metallic copper nanowire layer via an affinity group for metallic copper.
[2]
The superhydrophobic surface member according to [1], wherein the nanowire of the metal copper nanowire layer has a diameter in the range of 1 to 500 nm observed in a surface SEM image.
[3]
The superhydrophobic surface member according to [1] or [2], wherein the surface density obtained by the surface SEM image of the metallic copper nanowire layer is 10 to 90%.
[4]
The superhydrophobic surface member according to any one of [1] to [3], wherein the thickness of the metallic copper nanowire layer is in the range of 1 to 20 μm.
[5]
The superhydrophobic surface member according to any one of [1] to [4], wherein the superhydrophobic surface of the superhydrophobic surface member has a forward contact angle and a receding contact angle of 150 ° or more, respectively.
[6]
The superhydrophobic surface member according to any one of [1] to [5], wherein the superhydrophobic surface of the superhydrophobic surface member is a smooth surface or a surface having regular or irregular irregularities.
[7]
A metallic copper surface member having a metallic copper nanowire layer on the surface of a base material.
[8]
The metal copper surface member according to [7], wherein the nanowire of the metal copper nanowire layer has a diameter in the range of 1 to 500 nm observed in a surface SEM image.
[9]
The metallic copper surface member according to [7] or [8], wherein the surface density obtained by the surface SEM image of the metallic copper nanowire layer is 10 to 90%.
[10]
A step of forming a layer of copper hydroxide nanowires on the surface of a metallic copper base material or a base material having a metallic copper surface, a step of reducing a layer of copper hydroxide nanowires to form a metallic copper nanowire layer, and a metallic copper nanowire layer. A method for producing a super-water-repellent surface member, which comprises a step of forming an organic coating on the surface of the surface to obtain a super-water-repellent surface member.
[11]
The step of forming the layer of the copper hydroxide nanowire is (A) a step of immersing in an alkaline aqueous solution containing an oxidizing agent to form a layer of copper hydroxide nanowire on the surface, or (B) in an alkaline aqueous solution. The production method according to [10], which is a step of forming a layer of copper hydroxide nanowires on the surface by anodic oxidation with.
[12]
The production method according to [11], wherein the oxidizing agent is ammonium peroxodisulfate.
[13]
The production method according to any one of [10] to [12], wherein the formation of the organic material coating is carried out by coating the surface of the metallic copper nanowire layer with an organic compound having an affinity group for metallic copper.
[14]
A step of forming a layer of copper hydroxide nanowires on the surface of a metallic copper base material or a base material having a metallic copper surface, reducing the layer of copper hydroxide nanowires to form a metallic copper nanowire layer to obtain a metallic copper surface member. A method for manufacturing a metallic copper surface member, including a step.
[15]
The step of forming the layer of the copper hydroxide nanowire is (A) a step of immersing in an alkaline aqueous solution containing an oxidizing agent to form a layer of copper hydroxide nanowire on the surface, or (B) in an alkaline aqueous solution. The production method according to [14], which is a step of forming a layer of copper hydroxide nanowires on the surface by anodic oxidation with.
[16]
The production method according to [15], wherein the oxidizing agent is ammonium peroxodisulfate.
[17]
The production method according to any one of [11] to [16], wherein the alkaline aqueous solution is an alkali metal hydroxide aqueous solution.
[18]
The production method according to any one of [10] to [17], wherein the reduction of the copper hydroxide nanowire layer is hydrogen reduction.

In the superhydrophobic surface member of the present invention, since the nanowire layer is made of copper, which is a metal, the superhydrophobic surface has high thermal conductivity, and water film formation is suppressed on the superhydrophobic surface, and the surface is surfaced. It has the advantage that water droplets generated from coagulated water can be easily removed (excellent in drainage). Further, according to the present invention, since the superhydrophobic surface can be formed directly on the surface of the member by using the metallic copper surface member, the superhydrophobic surface member of the present invention can be easily manufactured. Further, according to the present invention, a method for producing the above-mentioned metallic copper surface member and a method for producing a superhydrophobic surface member are also provided.

FIG. 1-1 shows the appearance and surface morphology of the sample when the solution immersion time was changed from 3 minutes to 60 minutes in a mixed aqueous solution of _{NaOH and (NH 4} ) ₂ S ₂ O _8. FIG. 1-2 shows the results of measuring the film thickness by (a) an eddy current film thickness meter, (b) and (c) show cross-sectional SEM (secondary electron) images having different magnifications, and (d) and (E) shows cross-sectional BSE (backscattered electron) images having different magnifications. FIG. 1-3 shows the results of (a) XRD and (b) Raman spectra of the sample when the immersion time was changed in a mixed aqueous solution of NaOH and (NH ₄ ) ₂ S ₂ O _8. FIG. 1-4 shows an overview and surface morphology of the sample reduced in _{the Ar-10% H 2} mixed gas of the sample when the immersion time was changed in the mixed aqueous solution of NaOH and (NH ₄ ) ₂ S ₂ O _8. .. FIG. 1-5 shows the XRD results of the sample subjected to the same hydrogen reduction as in FIG. 1-4. FIG. 1-6 shows the surface morphology before and after lightly rubbing a sample immersed in a FAS solution with a sample immersed in a mixed aqueous solution of _{NaOH and (NH 4} ) ₂ S ₂ O _{8 for 10 minutes.} Show change. FIG. 1-7 shows the change in surface morphology before and after lightly rubbing the hydrogen-reduced sample in the PFDT solution for 1 hour with a finger. FIG. 2-1 shows a potential-time curve during constant current anodic oxidation. FIG. 2-2 shows (a) XRD pattern, (b) surface SEM, (c) cross-sectional SEM and (d) TEM of a sample anodic oxidized at 3 ^{mAcm-2 for 900 s.} FIG. 2-3 shows the appearance and SEM photograph of the sample oxidized with a constant current anode at ^{10 mAcm -2 at each time.} FIG. 2-4 shows a Raman spectrum of a sample anodic oxidized at a constant current of ^{10 mAcm-2 for each time.} FIG. 2-5 shows the appearance and SEM photograph of each sample after hydrogen reduction. Figure 2-6 shows the (a) 3mAcm ^-2 before and after hydrogen reduction of 900s anodized samples with XRD pattern (b) XRD patterns of samples anodized in 10mAcm ^-2. FIG. 2-7 shows the results of a dew condensation experiment after coating a sample anodic oxidized at 3 ^{mA cm-2 for 900 s.} FIG. 2-8 shows the results of a dew condensation experiment after coating a sample anodic oxidized at 10 ^{mAcm-2 for 120 s.} FIG. 2-9 shows the time variation of water on the hydroxide (top) and metallic copper nanowire (bottom) samples becoming ice.

<Superhydrophobic surface member and metallic copper surface member>
The super-water-repellent surface member of the present invention is a super-water-repellent surface member having a metallic copper nanowire layer and an organic material coating layer on the surface of the base material in this order, and the organic material coating layer is a metal via an affinity group for metallic copper. It is immobilized on a copper nanowire layer.

The present invention also includes a metallic copper surface member having a metallic copper nanowire layer on the surface of the base material, which is a precursor of the super-water-repellent surface member of the present invention.

The base material of the superhydrophobic surface member and the metallic copper surface member of the present invention is not particularly limited, and any member having a surface having excellent thermoconductivity and superhydrophobicity can be used as the base material. be able to. Examples of such a member include, but are not limited to, a condenser and a heat exchanger. The material of the base material is not particularly limited as long as the whole or the surface is made of metallic copper.

The nanowires of the metallic copper nanowire layer provided on the surface of the base material are made of metallic copper, and the metallic copper nanowire layer is a layer in which a plurality of nanowires are irregularly present with voids in the vertical and horizontal directions. Since the entire surface or the surface of the base material is made of metallic copper, the vicinity of the substrate surface of the metallic copper nanowire layer is in close contact with the surface of the metallic copper substrate and can be recognized as being integrated in appearance. The thickness of the nanowires in the metallic copper nanowire layer varies slightly depending on the location even with a single nanowire, but the diameter observed in the surface SEM image is, for example, in the range of 5 to 500 nm, preferably in the range of 20 to 250 nm. It is more preferably in the range of 50 to 200 nm. Within this range, excellent superhydrophobicity and drainage can be exhibited by providing a predetermined organic coating layer on the layer. In the present specification, these wire shapes are referred to as nanowires because all or most of the nanowires have diameters in the nanoorder range. The thickness of the metallic copper nanowire layer is not particularly limited, but may be, for example, in the range of 1 to 20 μm, or in the range of 1 to 10 μm.

The vicinity of the substrate surface of the metallic copper nanowire layer is in close contact with the copper substrate surface and is apparently integrated, making the bonding of the metallic copper nanowire layer to the substrate surface stronger and the strength of the super-water-repellent surface. Can be improved. The surface density of the metallic copper nanowire layer is, for example, 10 to 90%, preferably 30 to 60%, as the surface density obtained from the surface SEM image. Here, the surface density is obtained as follows. Using image analysis software such as ImageJ, the contrast of the surface SEM image was binarized between the part with nanowires and the void part, and the area ratio where nanowires exist was determined as the surface density.

The organic coating layer is immobilized on the metallic copper nanowire layer via an affinity group for metallic copper. The affinity group for metallic copper may be a functional group that chemically bonds and / or physically adsorbs to copper, and examples thereof include a thiol group, a disulfide group, a silane group, and a nitrile group. A thiol group is particularly preferable as the affinity group for metallic copper. As the site other than the affinity group of the organic coating layer, water-repellent groups such as a long-chain alkyl group, a fluorine-containing organic group, and an aromatic group can be mentioned in consideration of water repellency. Organic substances for coating organic substances will be described in detail in the description of the production method.

The superhydrophobic surface of the superhydrophobic surface member of the present invention can have a forward contact angle and a receding contact angle of, for example, 150 ° or more, respectively. Further, the superhydrophobic surface member of the present invention not only has a superhydrophobic surface, but also has excellent drainage from the superhydrophobic surface. The drainage property can be evaluated by, for example, cooling the surface of the sample inclined at 10 to 45 ° to cause dew condensation, and observing the formation of water droplets and the run-off.

In the superhydrophobic surface member, since the surface of the base material is smooth, the superhydrophobic surface can also be a smooth surface, and the surface of the base material has regular or irregular irregularities. The superhydrophobic surface can also be a surface with regular or irregular irregularities. Regular or irregular unevenness is not particularly limited in the depth and frequency of the unevenness. The same applies to the metallic copper surface member, and the smooth surface of the base material allows the surface of the metallic copper to be a smooth surface, and the surface of the base material has regular or irregular irregularities. The metallic copper surface can also be a surface having regular or irregular irregularities. Regular or irregular unevenness is not particularly limited in the depth and frequency of the unevenness.

<Manufacturing method of metallic copper surface member and superhydrophobic surface member>
The present invention includes a method for producing a metallic copper surface member and a superhydrophobic surface member, and the metal copper surface member and the superhydrophobic surface member of the present invention can be produced by this method. The method for producing a super-water-repellent surface member of the present invention is a step of forming a layer of copper hydroxide nanowires on the surface of a metallic copper base material or a base material having a metallic copper surface, and reducing the layer of copper hydroxide nanowires to metal. It includes a step of forming a copper nanowire layer and a step of forming an organic coating on the surface of the metallic copper nanowire layer to obtain a super-water-repellent surface member.

The step of forming the layer of the copper hydroxide nanowire is, for example, (A) a step of immersing in an alkaline aqueous solution containing an oxidizing agent to form a layer of the copper hydroxide nanowire on the surface (immersion method step). Alternatively, (B) is a step (anodoxidation method step) of forming a layer of copper hydroxide nanowires on the surface by anodic oxidation in an alkaline aqueous solution.

The method of going through the dipping method is a step (A1) of immersing a metallic copper base material or a base material having a metallic copper surface in an alkaline aqueous solution containing an oxidizing agent to form a layer of copper hydroxide nanowires on the surface. The method for producing a super-water-repellent surface member of the present invention includes the step (A2) of reducing a layer of copper hydroxide nanowires to form a metallic copper nanowire layer to obtain a metallic copper surface member. In addition to (A2), the step (A3) of forming an organic material coating on the surface of the metallic copper nanowire layer of the metallic copper surface member to obtain a super-water-repellent surface member is included. The oxidizing agent may be a compound capable of oxidizing the surface of metallic copper in an alkaline aqueous solution to form a layer of copper hydroxide nanowires on the surface, and examples thereof include ammonium peroxodisulfate, hydrogen peroxide, and hypochlorite. However, ammonium peroxodisulfate is preferable because the formation of the copper hydroxide nanowire layer is easy and reliable.

The method of going through the anodic oxidation method is a step of anodic oxidation of a metallic copper base material or a base material having a metallic copper surface in an alkaline aqueous solution to form a layer of copper hydroxide nanowires on the surface (B1), copper hydroxide. The method for producing a super-water-repellent surface member of the present invention includes the step (B2) of reducing a layer of nanowires to form a metallic copper nanowire layer to obtain a metallic copper surface member, and the method for producing a super-water-repellent surface member of the present invention includes the above steps (B1) and (B2). In addition, the step (B3) of forming an organic material coating on the surface of the metallic copper nanowire layer of the metallic copper surface member to obtain a super-water-repellent surface member is included.

Process (A1)
A base material made of metallic copper or a base material having a surface made of metallic copper is immersed in an alkaline aqueous solution containing an oxidizing agent such as ammonium peroxodisulfate to form a layer of copper hydroxide nanowires on the surface. It is already known that a layer of copper hydroxide nanowires is formed on the surface of a metallic copper base material or a base material having a metallic copper surface by immersing it in an alkaline aqueous solution containing ammonium peroxodisulfate. It is described in 3.

The base material made of metallic copper or the base material having a metallic copper surface is the same as the description in the above-mentioned metallic copper surface member and superhydrophobic surface member. The concentration of the oxidizing agent in the aqueous solution can be appropriately determined in consideration of the type of the oxidizing agent, the thickness of the copper hydroxide nanowire layer to be produced, and the like. Concentration when the oxidizing agent is ammonium peroxodisulfate is not particularly limited, for ^example, in the range of 0.01molL ^-1 ~ 1.0molL -1, preferably of 0.05molL ^{^-1} ~ 0.8molL ^-1 The range. The alkaline compound in the alkaline aqueous solution is not particularly limited, and is, for example, a hydroxide (for example, lithium hydroxide, sodium hydroxide, potassium hydroxide, etc.) and a strong alkali-weak acid salt compound (for example, potassium carbonate, etc.). There can be. Alkaline compounds in the aqueous solution concentration is not particularly limited, for ^example, in the range of 0.1molL ^-1 ~ 6.0molL -1, preferably in the range of 1.0molL ^{^-1} ~ 5.0molL ^-1. The immersion temperature can be, for example, in the range of 0 to 25 ° C., and the immersion time can be, for example, in the range of 1 minute to 180 minutes, depending on the concentration and temperature of ammonium peroxodisulfate in the aqueous solution. However, these numerical ranges are examples, and implementation is possible even outside this range. By immersing in this aqueous solution, copper hydroxide nanowires grow on the surface of the base material over time, and after a lapse of a predetermined time, a layer of copper hydroxide nanowires having a predetermined thickness is formed.

Process (B1)
A metal copper base material or a base material having a metal copper surface is anodized in an aqueous alkali metal hydroxide solution to form a layer of copper hydroxide nanowires on the surface. This method is known and can be carried out as appropriate with reference to, for example, the methods described in the following documents.
(A) Nano Letters 13 (3) (2018) 289-291
(B) Phys. Chem. B 109 (48) (2005) 22863-22842
(C) Industrial & Engineering Chemistry Research 54 (27) (2015) 6874-6883

The base material made of metallic copper or the base material having a metallic copper surface is the same as the description in the above-mentioned metallic copper surface member and superhydrophobic surface member. The alkaline compound in the alkaline aqueous solution is not particularly limited, and is, for example, a hydroxide (for example, lithium hydroxide, sodium hydroxide, potassium hydroxide, etc.) and a strong alkali-weak acid salt compound (for example, potassium carbonate, etc.). There can be. Alkaline compounds in the aqueous solution concentration is not particularly limited, for ^example, in the range of 0.1molL ^-1 ~ 6.0molL -1, preferably in the range of 1.0molL ^{^-1} ~ 5.0molL ^-1. The current density, temperature, and electrolysis time, which are the conditions for anodic oxidation, can be appropriately selected according to the thickness of the layer of the copper hydroxide nanowires to be formed, the shape and density of the copper hydroxide nanowires, and the like. The current density is, for example, in ^{the range of 0.1 to 20 mAcm-2} , the temperature is, for example, in the range of 0 to 50 ° C., and the electrolysis time is, for example, in the range of 1 minute to 180 minutes, depending on the current density and temperature. be able to. However, these numerical ranges are examples, and implementation is possible even outside this range. Due to this anodic oxidation, copper hydroxide nanowires grow on the surface of the substrate over time, and after a lapse of a predetermined time, a layer of copper hydroxide nanowires having a predetermined thickness is formed.

Steps (A2) and (B2)
The layer of copper hydroxide nanowires produced in step (A1) or (B1) is reduced to form a metallic copper nanowire layer. The reduction can be, for example, hydrogen reduction. Specifically, it can be carried out by placing the material to be reduced in a hydrogen atmosphere at a temperature in the range of 200 to 600 ° C. Even if the layer of the copper hydroxide nanowire is heated at the above temperature in the absence of a reducing gas such as hydrogen gas under normal pressure or reduced pressure, the reduction of copper hydroxide does not substantially occur, and the metal copper nanowire layer is formed. Virtually not formed. The hydrogen atmosphere may be 100% hydrogen gas, but for example, 1 to 99% hydrogen gas and the balance may be an inert gas such as argon or nitrogen. By varying the hydrogen gas concentration, the reduction rate of the copper hydroxide nanowire layer can be controlled in consideration of the heating temperature. By forming the metal copper nanowire layer at an appropriate reduction rate, a metal copper nanowire layer having excellent strength can be obtained. The hydrogen reduction may be either hydrogen circulation or a hydrogen atmosphere (batch). The reduction time can be appropriately determined in consideration of the temperature and the degree of reduction of the copper hydroxide nanowire layer, and is, for example, in the range of 10 minutes to 10 hours. By reducing the layer of copper hydroxide nanowires formed on the surface of the base material by the dipping method step or the anodic oxidation method step, a metal copper nanowire layer in which the vicinity of the substrate surface of the metal copper nanowire layer is in close contact with the base material surface is formed. A metallic copper surface member can be obtained. Further, the metallic copper nanowire layer is in close contact with the copper surface of the metallic copper base material or the base material having the metallic copper surface, and can be seen as being integrated in appearance.

Steps (A3) and (B3)
An organic coating is formed on the surface of the metallic copper nanowire layer of the metallic copper surface member obtained in the step (A2) and the step (B2) to obtain a superhydrophobic surface member. The organic coating is formed by coating the surface of the metallic copper nanowire layer with an organic compound having an affinity group for metallic copper. Examples of the organic compound having an affinity group for metallic copper include a thiol group, a disulfide group, a silane group, a nitrile group and the like as an affinity group for metallic copper, and a thiol group as an affinity group for metallic copper. Organic compounds having the above are particularly preferable. As the site other than the affinity group, a water-repellent group such as a long-chain alkyl group, a fluorine-containing organic group, or an aromatic group can be mentioned in consideration of water repellency.

The organic compounds having an affinity group for metallic copper are illustrated below, but the intention is not limited to these. n-dodecanethiol, n-dodecaneselenol, dododecil disulfide, dododecil disulfidee, decane-phosphate, decane-phosphate. Decanoic acid, stearic acid, 1H, 1H, 2H, 2H-perfluorodecanethiol (1H, 1H, 2H, 2H-perfluorodecanethiol), decyltriethoxysilane, 1H 2H, 2H-perfluorodecyltriethoxysilane (1H, 1H, 2H, 2H-Perfuodecil-triethoxysilane), decaneisocyanide.

The superhydrophobic surface of the superhydrophobic surface member having an organic coating has a forward contact angle and a receding contact angle of 150 ° or more, respectively, and has excellent drainage from the superhydrophobic surface. Since the organic coating is also formed on the inner surface of the metallic copper nanowire layer, it is presumed that, for example, water droplets generated by dew condensation inside the metallic copper nanowire layer are easily extruded to the super-water-repellent surface. To. Since the nanowire layer on the surface of the super-water-repellent surface member of the present invention is metallic copper, the surface has high thermal conductivity, the surface is super-water-repellent, and the drainage of water droplets generated by dew condensation is also excellent. , Very useful for condensers and heat exchangers.

Hereinafter, the present invention will be described in more detail based on examples. However, the examples are examples of the present invention, and the present invention is not intended to be limited to the examples.

Characterization (1) SEM image An SEM image was obtained by operating with an acceleration voltage of 1 kV using an SEM (Micro Star Technologies Inc.).
(2) Cross-section observation The cross-section of the sample was prepared by an ultramicrotome (Power Tome X, RMC, UK) using a diamond knife.
(3) The phase of the sample was identified using an X-ray diffractometer (XRD) (RINT-2200, Rigaku, Japan) using Cu Kα rays.
(4) Structural characterization of the sample by Raman spectroscopy was performed using a Raman spectroscope (XploRa, HORIBA, Ltd., Japan). The wavelength of the irradiated laser was 532 nm, and the grating was 2400 grmm ^-1 .
(5) Static water contact angle and dynamic water contact angle The still water contact angle and dynamic water contact angle on the surface of the test piece were measured using a contact angle meter (DM-CE1 optical, Kyowa, Japan) using FAMAS software. The static water contact angle was measured using 4 μL of water droplets, and the dynamic water contact angle was determined by the expansion contraction method. The contact angles were measured at four points on each test piece, and the average value and standard deviation were calculated. Hysteresis was determined as the difference between the hydrostatic contact angle and the running water contact angle.
(6) Observation behavior of water vapor condensation The test piece was cooled on a Perche cooling plate at 0 ° C. in a constant temperature and humidity chamber having a temperature of 25 ° C. and a relative humidity of 60%, and the condensation behavior of water vapor was observed. The surface was imaged using a digital camera (Togh TG-5, Olympus, Japan).

Example 1
(1) Preparation of Copper Hydroxide Nanowires by Immersion in Solution Figures 1-1 (a) to (h) show 2.5 moldm ^-3 NaOH and 0.1 moldm ^-3 (NH ₄ ) ₂ S _{2 at a temperature of 4 to 5 ° C.} in a mixed aqueous solution of O ₈ an overview and surface morphology of the sample when the solution immersion time was changed from 3 minutes to 60 minutes. It was confirmed that a nanowire film was formed on the surface, and the color of the sample surface became deep blue by lengthening the immersion time. The results of measuring the film thickness using an eddy current film thickness meter are shown in FIG. 1-2 (a). From FIG. 1-2 (a), it was confirmed that the thickness of the film was increased by increasing the immersion time. When the immersion time is 10 minutes, the thickness of the film is about 1 to 2 μm from FIG. 1-2 (a), the cross-sectional SEM images of FIGS. 1-2 (b) and (d), and (c) and (e). ) Was about 1 to 2 μm from the cross-sectional observation of the sample shown in the BSE image.

Samples shown in FIGS. 1-3 (a) and (b) when the immersion time was changed in a mixed aqueous solution ^{of 2.5 moldm -3} NaOH and 0.1 moldm ^-3 (NH ₄ ) ₂ S ₂ O _{8 at a temperature of 4 to 5 ° C.} The results of the XRD and Raman spectra of the above are shown. From the XRD of FIG. 1-3 (a), the _{peak attributed to Cu (OH) 2} was confirmed, but the peak was not detected in the case where the immersion time was short. It is considered that this is because the amount of nanowires produced is small. A peak of copper hydroxide was also detected from Raman in FIG. 1-3 (b), and copper hydroxide nanowires were formed by solution immersion, and growth of the nanowire layer was confirmed by extending the immersion time.

(2) Formation of metallic copper nanowires by hydrogen reduction As shown in FIGS. 1-4 (a) to (h), 2.5 moldm ^-3 NaOH and 0.1 moldm ^-3 (NH ₄ ) ₂ S ₂ O _{8 at a temperature of 4 to 5 ° C.} mixed sample through the Ar-10% H ₂ gas mixture was subjected to solution immersion in an aqueous solution of an overview and surface morphology of 1 hour reduced samples at 300 ° C.. From Fig. 1-4, it was confirmed that the nanowire morphology was maintained even after hydrogen reduction, and the shape of the nanowire changed, but due to volume change and stress when hydroxide was converted to copper by hydrogen reduction. Is. The surface density obtained by observing the surface of metallic copper nanowires with SEM differs depending on the production conditions. For example, in the sample when the immersion method is 5 minutes, about 32% of the surface is covered with nanowires ((Fig. 1-4). b) See the SEM image in (f)). On the other hand, the surface density of the sample when the immersion method is 60 minutes is about 37% (see the SEM images of (d) and (h) of FIGS. 1-4).

The thickness of the metallic copper nanowire layer is about the same as the thickness of the copper hydroxide nanowire layer shown in FIGS. 1-2 (a), and the thickness of the metallic copper nanowire layer in FIGS. 1-4 (a) and 1-4 (e) is about. It is 0.5 μm, the thickness of the nanowire is in the range of about 50 to 250 nm, the thickness of the metal copper nanowire layer of (b) and (f) is about 1.5 μm, and the thickness of the nanowire is about. The thickness of the metal copper nanowire layer of (c) and (g) is in the range of 50 to 250 nm, the thickness of the nanowire is in the range of about 50 to 250 nm, and the thickness of the nanowire is in the range of about 50 to 250 nm. The thickness of the metallic copper nanowire layer was about 7 μm, and the thickness of the nanowire was in the range of about 50 to 250 nm.

Figure 1-5 shows the XRD results of the hydrogen-reduced sample. From FIG. 1-5, only the diffraction line of metallic copper was confirmed, and it is considered that copper hydroxide was converted to metallic copper.

(3) Wetting property of nanowire surface Table 1-1 shows that the solution was immersed in a mixed aqueous solution ^{of 2.5 moldm -3} NaOH and 0.1 moldm ^-3 (NH ₄ ) ₂ S ₂ O _{8 at a temperature of 4 to 5 ° C.} A constant temperature and humidity chamber with a temperature of 25 ° C and a relative humidity of 60%, with a forward contact angle, a receding contact angle, and a hysteresis of the sample immersed in a 2 vol% 1H, 1H, 2H, 2H-perfluorodecyltriesothylane (FAS) solution in ethanol for 2 hours. An overview of the sample obtained by cooling the test piece on a Perche cooling plate at 0 ° C. for 10 minutes to condense water vapor is shown. From Table 1-1, all the samples showed a contact angle with respect to water higher than 150 °, and the contact angle hysteresis showed a low value of about 2 °. Therefore, the copper hydroxide nanowires were coated with FAS to have a surface showing superhydrophobicity. In addition, from the state after water vapor condensation, there was little adhesion of water droplets under low temperature conditions, and the surface was such that the water droplets easily rolled off.

Table 1-2 shows the samples immersed in a mixed aqueous solution ^{of 2.5 moldm -3} NaOH and 0.1 moldm ^-3 (NH ₄ ) ₂ S ₂ O _{8 at} a temperature of 4 to 5 ° C. _{Ar-10% H 2} A sample reduced at 300 ° C. for 1 hour in a mixed gas was added to ethanol at 1 wt. 0 in a constant temperature and humidity chamber with a temperature of 25 ° C and a relative humidity of 60% with the forward contact angle, receding contact angle and hysteresis (CAH) of the sample immersed in the% 1H, 1H, 2H, 2H-percoolodecanetic (PFDT) solution for 1 hour An overview of the sample obtained by condensing water vapor by cooling the test piece for 10 minutes on a Perche cooling plate at ° C. is shown. From Table 1-2, all the samples showed a high contact angle of water exceeding 150 °, and the contact angle hysteresis showed a low value of about 2 °. Therefore, the reduced copper nanowires were coated with PFDT to obtain a surface showing superhydrophobicity. In addition, from the state after water vapor condensation, there was little adhesion of water droplets under low temperature conditions, and the surface was such that the water droplets easily rolled off.

(4) Evaluation of adhesion of nanowires Figures 1-6 (a) to (d) show a mixture ^{of 2.5 moldm -3} NaOH and 0.1 moldm ^-3 (NH ₄ ) ₂ S ₂ O _{8 at a temperature of 4 to 5 ° C.} Changes in surface morphology before and after lightly rubbing a sample soaked in an aqueous solution for 10 minutes with a finger against a sample soaked in a 2 vol% 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (FAS) solution in ethanol for 2 hours. 1-7 (a) to (d) show, the sample subjected to hydrogen reduction was immersed in a 1 wt% 1H, 1H, 2H, 2H-perfluorodecanethiol (PFDT) solution in ethanol for 1 hour. Shows the change in surface morphology before and after light rubbing with. From FIGS. 1-6 (c) and (d), it was confirmed that the copper hydroxide nanowire covered the surface while maintaining the nanowire morphology, although the nanowire was shortened after being lightly rubbed with a finger. Similarly, from FIGS. 1-7 (c) and 1-7 (d), it was confirmed that the metal copper nanowires were also shortened after being lightly rubbed with a finger, but covered the surface while maintaining the nanowire morphology.

Further, a sample obtained by immersing the sample in a mixed aqueous solution ^{of 2.5 moldm -3} NaOH and 0.1 moldm ^-3 (NH ₄ ) ₂ S ₂ O ₈ at a temperature of 4 to 5 ° C. for 10 minutes was placed in ethanol at 2 vol% 1H. A sample soaked in a 1H, 2H, 2H-perfluorodecyltrietothoxysylane (FAS) solution for 2 hours and a sample subjected to hydrogen reduction were immersed in a 1 wt% 1H, 1H, 2H, 2H-perfluorodecanethiol (PFDT) solution in ethanol for 1 hour. On the other hand, the test piece was placed on a Perche cooling plate at 0 ° C in a constant temperature and humidity chamber with a temperature of 25 ° C and a relative humidity of 60% with the forward contact angle, backward contact angle and hysteresis (CAH) of the sample before and after lightly rubbing with a finger. Table 1-3 shows an overview of the sample obtained by cooling the sample for 10 minutes and condensing the water vapor. From Table 1-3, the contact angle values of the copper hydroxide nanowires and the metallic copper nanowires after rubbing were smaller than those before rubbing, but the contact angle values still exceeded 150 ° on the superhydrophobic surface. .. In addition, although the number of condensed droplets was larger than that before rubbing, the droplets did not get wet and spread, and rolled easily when the sample was tilted.

Example 2
A copper plate having a thickness of 0.3 mm and a purity of 99.96% was washed with acetone and immersed in 18% hydrochloric acid for 10 minutes as a pretreatment. Then, anodic oxidation was carried out at 20 ° C. and 3M KOH at a current density of 10mAcm- ² or 3mAcm- ^{2 for a predetermined time.} This was followed by one hour hydrogen reduction at Ar-5% _{H 2} 300 ℃ gas.

The organic coating was ^{carried out by immersing in a 5 mmol dm-3} toluene solution of stearic acid (SA) or a 1.0 wt% 1H, 1H, 2H, 2H-perfluorodecanethiol (PFDT) ethanol solution for 1 hour.

(1) Anode oxidation Figure 2-1 shows the voltage-time curve when anodic oxidation is performed with a constant current of ^{3 or 10 mAcm-2.} Anode oxidation proceeds at a substantially constant voltage at any current density, but then shows a rapid voltage rise. During anodic oxidation, the surface becomes a light blue surface peculiar to Cu (OH) ₂ , but if anodic oxidation is continued after the voltage rises, film peeling starts around the time indicated by the arrow. Therefore, in order to obtain an anodic oxide film having good adhesion, it is desirable to terminate electrolysis before the voltage rises.

The XRD pattern of the sample anodic oxidized at 3 mAcm- ^{2 for 900 s is shown in FIG. 2-2a.} In addition to the diffraction line of metallic Cu, the diffraction line of Cu (OH) ₂ can be seen, and it can be seen that the anodic oxide film is composed _{of Cu (OH) 2.} A surface SEM photograph of this sample is shown in FIG. 2-2b. Cu (OH) ₂ has a nanowire shape, which covers the entire copper surface. The thickness of the nanowires is about 100 nm, and it has a shape in which several nanowires are joined. Further, from the cross-sectional SEM observation result (Fig. 2-2c), the thickness of the nanowire layer is about 20 μm, and a part having a relatively dense structure can be seen in the part of the nanowire layer near the copper plate surface, and this part is a nanowire. It is considered to be the portion that became the base on which the layer was deposited. In the present invention, the base portion is also a part of the nanowire layer. The generated nanowire film was scratched with tweezers, peeled off from the substrate, dispersed in ethanol, placed on a Cu grid, and TEM-observed (Fig. 2-2d). It was confirmed that the nanowires were single crystals and that the nanowires grew parallel to the {010} plane.

When anodic oxidation is performed at a current density of 10 mAcm ^-2 , copper hydroxide nanowires (Fig. 2-3) cover the surface of the sample in 30 s to 120 s, and the surface color becomes blue as the oxidation time increases. Has become darker. On the other hand, in 10s of anodic oxidation, the surface is brown and nanoparticulate products are seen on the surface. When the anodic oxide film was identified by Raman spectroscopy (Fig. 2-4), the very thin film formed in 10s was Cu ₂ O, and this Cu ₂ O became a precursor of the nanowire layer, and then Cu ( It was clarified that a nanowire layer of OH) _{2 was formed.} It is presumed that the copper substrate was oxidized to _{Cu 2} O by anodic oxidation and ^{Cu 2+} was eluted, and then the eluted Cu ²⁺ was reprecipitated as Cu (OH) ₂ in the form of nanowires to form a nanowire layer.

(2) Hydrogen reduction After that, when the Cu (OH) ₂ nanowire sample is hydrogen-reduced at 300 ° C. for 1 hour _{, the reduction occurs while maintaining the shape of the Cu (OH) 2} nanowires, and the metallic copper nanowires are surfaced. Was covered (Fig. 2-5). The surface density obtained from the surface SEM observation of metallic copper nanowires differs depending on the fabrication conditions. ^{It is about 50% in the sample anodic oxidized at 3 mAcm -2} for 900 s (see the SEM image of 3/900 in FIG. 2-5). On the other hand, ^{at 10 mAcm-2} , the surface density of the 120 s anodic oxide sample remained at about 20% (see the SEM image of 10/120 in FIG. 2-5).

The XRD pattern before and after the reduction is shown in FIG. 2-6. In both cases, the peak of copper hydroxide that was before the reduction disappeared after the reduction. From this, it can be seen that the reduction is appropriately performed to obtain the metallic copper nanowire layer. Further, the hydroxide peaks of samples anodized in 10MAcm ^-2 from weaker than samples anodized in 3MAcm ^-2, metallic copper nanowires layer is seen thinner.

The samples before and after the reduction were coated with stearic acid (SA) or 1H, 1H, 2H, 2H-perfluorodecanethiol (PFDT), and the forward contact angle, receding contact angle and hysteresis (CAH) were measured. As a result, the samples in which the nanowire layer was precipitated on the surface showed superhydrophobicity with all contact angles exceeding 150 ° before and after reduction (Table 2).

In addition, when the current density was ^{anodic oxidized at 3 mAcm -2} for 900 s, there was no significant difference in the shape of the wire before reduction compared to the case of 10 mA cm ^-2 ^{, but after reduction, the surface density of the nanowire was 3 mA cm -2} . Was found to be large (see Figure 2-5 above).

(3) Condensation test A constant temperature constant at 20 ° C. and 60% humidity for a sample subjected to 900s anodic oxidation at ^{3mAcm-2 (3/900 sample in Fig. 2-5 and Table 2) and SA or PFDT coating.} A dew condensation test was carried out by placing a Perche element in a wet bath, placing a sample on it, and setting the temperature of the Perche stage to 0 ° C. At that time, the Perche stage was installed at an angle of about 20 °. The result (photograph) is shown in FIG. 2-7.

In the sample before hydrogen reduction, the SA-coated sample had fewer water droplets than the PFDT-coated sample. However, in the sample after hydrogen reduction, it can be seen that the PFDT-coated sample has far less adhesion of water droplets than the SA-coated sample, and the water droplets have fallen from the surface, and the drainage property is excellent. That is, it was found that the PFDT-coated sample, which is a member of the present invention, has a large effect of suppressing water film formation. This result shows that the effect of the coating on water repellency and drainage is different between the metal surface (after reduction) and the hydroxide surface (before reduction), and on the metal surface (after reduction), PFDT having an affinity group of thiol is used. It turns out to be valid.

Further, FIG. 2-8 shows the results of the same dew condensation test on the samples (10/120 samples in FIGS. 2-5 and Table 2) that were anodic oxidized at 10 ^{mAcm-2 for 120 s.} The SA coating before hydrogen reduction has more condensation than the sample anodic oxidized at 3 ^{mAcm-2 in FIG. 2-7 for 900 s.} The PFDT-coated sample after hydrogen reduction has ^{more dew condensation than the sample (3/900 sample) anodic-oxidized at 3 mAcm-2} in Fig. 2-7, but the amount of water droplets remaining on the surface is smaller than that of the SA-coated sample. You can see that. Considering that the surface density of the nanowires of the 3/900 sample was estimated to be about 50% and the surface density of the nanowires of the 10/120 sample was estimated to be about 20% from the surface SEM photograph of FIG. 2-5. It can be judged that the higher the surface density of the nanowires, the better the drainage property of the condensed water droplets.

(4) Thermal conductivity test Finally, a SA-coated sample (comparative example) before hydrogen reduction of a sample (3/900 sample) anodic-oxidized at 3 ^{mAcm -2} for 900 s and a sample (3/900 sample) anodic-oxidized at 3 ^{mA cm -2 for 900 s.} The rate of change of water to ice when water is placed on the super-water-repellent surface of the PFDT-coated sample (sample of the present invention) after hydrogen reduction of the / 900 sample) and the sample is cooled to -20 ° C on the Perche stage. evaluated. The results are shown in Fig. 2-9. On the surface of the superhydrophobic Cu (OH) ₂ nanowire of the comparative example, it took about 15 minutes for the water to turn into ice, whereas on the surface of the superhydrophobic Cu metal nanowire, which is the sample of the present invention, water took only 5 minutes. Frozen and turned into ice. It was confirmed that the sample of the present invention had significantly improved thermal conductivity as compared with the surface of _{superhydrophobic Cu (OH) 2 nanowires.}

Since the nanowire layer produced by the anodic oxidation method shown in Example 2 is accompanied by gas generation during the formation of copper hydroxide nanowires, defects such as cracks are likely to occur between the nanowire layer and the substrate depending on the anodic oxidation conditions, and the nanowires. It is presumed that the adhesion of the layer to the substrate may be relatively weaker than that of the nanowire layer produced by the dipping method shown in Example 1. On the other hand, the nanowire layer produced by the dipping method does not generate gas when forming the copper hydroxide nanowire layer, and therefore does not generate gas, which is a factor that deteriorates the adhesion between the nanowire layer and the substrate in the manufacturing process. There is a possibility that the adhesion between the nanowire layer and the substrate is superior to that of the nanowire layer produced by the anodic oxidation method.

The present invention is useful in the technical field related to members having a superhydrophobic surface.

Claims

A superhydrophobic surface member having a metallic copper nanowire layer and an organic material coating layer on the surface of the base material in this order.
The superhydrophobic surface member, wherein the organic coating layer is immobilized on the metallic copper nanowire layer via an affinity group for metallic copper.
The superhydrophobic surface member according to claim 1, wherein the nanowire of the metal copper nanowire layer has a diameter in the range of 1 to 500 nm observed in a surface SEM image.
The superhydrophobic surface member according to claim 1 or 2, wherein the surface density obtained by the surface SEM image of the metallic copper nanowire layer is 10 to 90%.
The superhydrophobic surface member according to any one of claims 1 to 3, wherein the thickness of the metallic copper nanowire layer is in the range of 1 to 20 μm.
The superhydrophobic surface member according to any one of claims 1 to 4, wherein the superhydrophobic surface of the superhydrophobic surface member has a forward contact angle and a receding contact angle of 150 ° or more, respectively.
The superhydrophobic surface member according to any one of claims 1 to 5, wherein the superhydrophobic surface of the superhydrophobic surface member is a smooth surface or a surface having regular or irregular irregularities.
A metallic copper surface member having a metallic copper nanowire layer on the surface of a base material.
The metal copper surface member according to claim 7, wherein the nanowire of the metal copper nanowire layer has a diameter in the range of 1 to 500 nm observed in a surface SEM image.
The metallic copper surface member according to claim 7 or 8, wherein the surface density obtained by the surface SEM image of the metallic copper nanowire layer is 10 to 90%.
A step of forming a layer of copper hydroxide nanowires on the surface of a metallic copper base material or a base material having a metallic copper surface, a step of reducing a layer of copper hydroxide nanowires to form a metallic copper nanowire layer, and a metallic copper nanowire layer. A method for producing a super-water-repellent surface member, which comprises a step of forming an organic coating on the surface of the surface to obtain a super-water-repellent surface member.
The step of forming the layer of copper hydroxide nanowire is (A) a step of immersing in an alkaline aqueous solution containing an oxidizing agent to form a layer of copper hydroxide nanowire on the surface, or (B) in an alkaline aqueous solution. The production method according to claim 10, which is a step of forming a layer of copper hydroxide nanowires on the surface by oxidizing with an alkali.
The production method according to claim 11, wherein the oxidizing agent is ammonium peroxodisulfate.
The production method according to any one of claims 10 to 12, wherein the formation of the organic material coating is carried out by coating the surface of the metallic copper nanowire layer with an organic compound having an affinity group for metallic copper.
A step of forming a layer of copper hydroxide nanowires on the surface of a metallic copper base material or a base material having a metallic copper surface, and reducing the layer of copper hydroxide nanowires to form a metallic copper nanowire layer to form a metallic copper surface member. A method for manufacturing a metallic copper surface member, which comprises a step of obtaining.
The step of forming the layer of copper hydroxide nanowire is (A) a step of immersing in an alkaline aqueous solution containing an oxidizing agent to form a layer of copper hydroxide nanowire on the surface, or (B) in an alkaline aqueous solution. The production method according to claim 14, which is a step of forming a layer of copper hydroxide nanowires on the surface by oxidizing with an alkali.
The production method according to claim 15, wherein the oxidizing agent is ammonium peroxodisulfate.
The production method according to any one of claims 11 to 16, wherein the alkaline aqueous solution is an alkali metal hydroxide aqueous solution.
The production method according to any one of claims 10 to 17, wherein the reduction of the copper hydroxide nanowire layer is hydrogen reduction.