WO2021087982A1

WO2021087982A1 - Super-hydrophobic material, preparation method therefor and application thereof

Info

Publication number: WO2021087982A1
Application number: PCT/CN2019/116701
Authority: WO
Inventors: 潘锋; 吴忠振; 刘亮亮; 李舜宁
Original assignee: 北京大学深圳研究生院
Priority date: 2019-11-08
Filing date: 2019-11-08
Publication date: 2021-05-14
Also published as: CN114787427A; CN114787427B

Abstract

A super-hydrophobic material, a preparation method therefor and an application thereof. A hydrophobic surface of the super-hydrophobic material is composed of a positive surface energy material, a negative surface energy material and micro-nano voids. The super-hydrophobic material has a super-hydrophobic performance by means of introducing the negative surface energy material and a micro-nano void design on the hydrophobic surface without using low-surface-energy organic substances. Moreover, since no organic substances are used, the super-hydrophobic material has good temperature and weather resistance, and excellent wear and corrosion resistance.

Description

Super-hydrophobic material and its preparation method and application

Technical field

This application relates to the field of superhydrophobic materials, in particular to a superhydrophobic material and its preparation method and application.

Background technique

The lotus leaves in nature show the phenomenon that water droplets are not sticky. This super-hydrophobic phenomenon has aroused extensive research interest of scientists. According to the wettability model theory, a material with a contact angle of water droplets on a solid surface greater than 150° is defined as a superhydrophobic material. Since superhydrophobic materials involve the wettability of the material surface, they currently have good application prospects in the fields of interface science, such as anti-icing, anti-fogging, anti-scaling, anti-corrosion, and drag reduction in water.

In recent years, most of the preparation methods of superhydrophobic materials are mainly to construct micro-nano structures on the surface of the materials and then modify them with organic low-surface substances, or directly construct micro-nano structures with hydrophobic organic substances as substrates. These methods all involve the use of organic substances with low surface energy, and the organic substances have poor stability such as temperature resistance and weather resistance, and are easy to volatilize at high temperatures, thereby affecting the service life of superhydrophobic materials.

Inorganic oxide materials have excellent mechanical properties and corrosion resistance, and are often used in various fields of human life and industry. However, oxides often exhibit large surface energy. The current preparation of superhydrophobic oxide coatings is to obtain nano-oxides and then modify them with organic substances with low surface energy. This method still inevitably introduces organic substances.

Therefore, how to effectively improve the temperature resistance and weather resistance of superhydrophobic materials is the focus and difficulty of the current research on superhydrophobic materials.

Summary of the invention

The purpose of this application is to provide a new superhydrophobic material and its preparation method and application.

This application adopts the following technical solutions:

On the one hand, this application discloses a superhydrophobic material, the hydrophobic surface of the superhydrophobic material is composed of a positive surface energy material, a negative surface energy material and micro-nano voids.

Among them, the negative surface energy material is embedded in the positive surface energy material, and the micro-nano voids have zero surface energy. The superhydrophobic material of the present application, on the one hand, by introducing negative surface energy materials on the surface, the hydrophobic surface has better hydrophobic performance; the lower the surface energy of the negative surface energy material, the better the hydrophobicity. On the other hand, this application introduces micro-nano voids on the hydrophobic surface to reduce the contact area between water droplets and the hydrophobic surface. Through the above two points of design, this application forms a special hydrophobic surface with positive surface energy, negative surface energy and zero surface energy structure, so that the material of this application has superhydrophobic properties. In one implementation of this application, the superhydrophobic material The contact angle can reach 152° or even higher, while the sliding angle to water is less than 3°.

It should also be noted that the hydrophobic surface of the superhydrophobic material of the present application is formed by positive surface energy, negative surface energy and zero surface energy. In theory, it is not necessary to use any organic substances; for example, a realization of this application In the method, the hydrophobic surface is completely formed by inorganic metal oxides; therefore, the superhydrophobic material of the present application has excellent mechanical properties and good temperature resistance, weather resistance, wear resistance and corrosion resistance, which solves the existing problems based on organic substances. The super-hydrophobic material is not resistant to temperature, weathering, and abrasion.

Preferably, the negative surface energy material is a material that can interact with water and undergo interface reconstruction to form a new negative surface energy interface.

It should be noted that the negative surface energy materials in this application are actually a class of materials, which can interact with water when in contact with water, resulting in interface reconstruction, forming a new interface with negative surface energy; It is through this kind of materials, combined with the micro-nano gap design of the present application, that the super-hydrophobic properties of the present application are realized.

Preferably, the negative surface energy material is a metal oxide, and the metal oxide has a specific crystal phase structure, wherein the specific crystal phase structure can interact with water and undergo interface reconstruction to form a new negative surface energy interface.

Preferably, the metal oxide is an oxide of at least one of aluminum, copper, zinc, titanium, zirconium, magnesium, iron, and rare earth elements.

Preferably, the metal oxide is θ-phase alumina.

It should be noted that the research in this application has discovered that the θ-phase alumina, which has a specific crystal phase structure, can interact when it comes into contact with water, resulting in interface restructuring, forming a new negative surface energy interface, and achieving super-hydrophobicity. performance. It can be understood that theta-phase alumina is only a typical negative surface energy material in one implementation of this application, and it is not excluded that other metal elements can also have similar functions as theta-phase alumina under a specific crystal phase structure, such as copper oxide and oxidation. Zinc, titanium oxide, zirconium oxide, magnesium oxide, iron oxide, and rare earth element oxides.

Preferably, the structural formula of the metal oxide is M _x O _y , where M is one of aluminum, copper, zinc, titanium, zirconium, magnesium, iron and rare earth elements, O is oxygen, and x and y satisfy the chemical formula of the structural formula. Stoichiometric ratio, and the chemical potential of the elements M and O satisfies formula 2,

Formula 2:

When the metal oxide is in contact with water and interacts to reconstruct the interface to form a new interface, the element H is introduced, and the surface energy calculation formula of the new interface formed by its reconstruction is Equation 3.

Formula 3:

In formulas 2 and 3, γ is the surface energy, E _surf is the total energy of the material when the surface contains a specific crystal phase structure, A is the area of the surface, _NM and μ _M are respectively the total of the element M in the metal oxide atoms and chemical potential, N _O _O [mu], respectively, and a metal oxide of the element O and the total number of atoms in chemical potential, N _H and _H [mu] metal oxide element are H and the total number of atoms in chemical _potential, E stio To assume that there is no H element on the surface, the total number of atoms of M is the same as the actual surface, and the surface composition meets the stoichiometric ratio of M _x O _y , the total energy of the system, n is the total number of atoms of M in the system divided by x,

It is the total energy of the bulk material per unit of chemical formula M _x O _y _{, and E w/oH} is the total energy of the system assuming that there is no H element on the surface and the total number of atoms of M and O is the same as the actual surface. among them,

When it is low enough, a superhydrophobic material with negative surface energy can be obtained.

It should be noted that the traditionally defined surface energy is the additional energy required by the material to form the surface. When the material forms the surface, its chemical bonds will be broken, which will increase the energy of the system, so the calculated surface energy must be positive, otherwise the material will vaporize. However, the traditional definition of surface energy is defined in an ideal situation, that is, the formed surface is in a vacuum and is not affected by the environment. But in actual situations, the surface will react with the environment, the system energy will be reduced, and the additional energy required to form the surface will also decrease. Therefore, this application adopts the following more rigorous definition of surface energy:

Formula 1:

In a formula, γ is the surface energy, E _surf containing a total surface energy of the material, A for the area of the surface, N _i [mu] _i, respectively, and the material of element i and the total number of atoms in chemical potential. Taking the binary metal oxide M _x O _y as an example, the chemical potentials of the elements M and O satisfy the following equation:

Formula 2:

In formula 2,

It is the total energy per unit chemical formula M _x O _{y body material.} When _{the third element is introduced on the surface of M x} O _y , such as hydrogen is introduced, the calculation formula for its surface energy is:

Formula 3:

In three-, N _M and [mu] _M, respectively, as the material of the element M of the total number of atoms and chemical potential, N _O and [mu] _O respectively material element O in the total number of atoms and chemical potential, N _H and μ _H are materials The total atomic number and chemical potential of element H, _Estio is the total energy of the system assuming that there is no H element on the surface, the total atomic number of M is the same as the actual surface, and the surface composition meets the stoichiometric ratio M _x O _{y, n is the system} Divide the total number of atoms in M by x. Under this definition,

It is the traditional surface energy, which represents the energy required to break the chemical bond, and is always positive. E _w/oH is the total energy of the system assuming that there is no H element on the surface and the total number of atoms of M and O is the same as the actual surface. Under this definition,

Represents the bond breaking energy compensated when a new MO bond is formed on the surface. However, since new bond breaks will be introduced at this time, this item and

The addition is still positive. Last item

It represents the energy released by the formation of OH bonds on the surface. Because the original broken bonds are eliminated, this item is always negative. When this item is low enough, the surface energy of the system will be negative. It can be seen that, from a thermodynamic point of view, the surface energy of the material can be changed to a negative value by introducing new components or groups, that is, when the superhydrophobic material of the present application interacts with water, the interface is reconstructed. Due to the introduction of hydrogen, a new reconstructed interface with negative surface energy is formed.

For example, for theta-phase alumina, its (10-2) surface will cause an OH bond in the water molecule to break after adsorbing water molecules, so that the surface will adsorb one OH and one H. As this process proceeds spontaneously, new formation The OH bond and Al-O bond compensated for the original broken bond, so that the energy of the system decreased, and the surface energy of the new surface formed was negative.

It should be noted that in this application, positive surface energy materials are generally normal. One of the key points of this application is to improve hydrophobicity through negative surface energy materials. The higher the proportion of negative surface energy materials, the stronger the hydrophobicity; however, many At that time, negative surface energy materials cannot exist independently or have poor stability, such as θ-phase alumina; therefore, the superhydrophobic material in this application is composed of positive surface energy materials, negative surface energy materials and micro-nano voids. Among them, the positive surface energy material can stabilize the negative surface energy material, so that the superhydrophobic material has better stability and better mechanical properties. Therefore, the specific surface energy of the positive surface energy material and the negative surface energy material or the ratio of the two can be determined according to specific usage requirements. As for how to control the acquisition of positive surface energy materials and negative surface energy materials, take the specific crystal phase structure of metal oxides as an example. In one implementation of the present application, the electrolyte and micro-arc in the micro-arc oxidation method can be adjusted. The oxidation temperature and the pulse power processing parameters of the micro-arc oxidation realize the preparation of different crystal phase structures, thereby obtaining the negative surface energy material of the present application.

Preferably, the size of the micro-nano voids is 0.1-10 μm.

It should be noted that the size of the micro-nano gap can also be adjusted and controlled by the electrolyte in the micro-arc oxidation, the temperature of the micro-arc oxidation, and the pulse power processing parameters of the micro-arc oxidation in an implementation of this application. . The function of micro-nano voids is to reduce the contact surface with water, thereby improving the hydrophobic performance; it can be understood that the micro-nano voids cannot be too large or too small, too large voids will not have a hydrophobic effect, and too small voids will affect the hydrophobic performance. Improve the effect.

The other side of the application discloses the use of the superhydrophobic material of the present application in the preparation of self-cleaning materials, anti-icing or anti-icing and snow covering materials, anti-fingerprint materials, anti-fog materials, anti-scaling materials, anti-corrosion materials or water drag reducing materials application.

It should be noted that, because the superhydrophobic material of the present application has good hydrophobicity, it can be used to prepare various materials, assemblies or equipment that require hydrophobic properties, such as self-cleaning materials, anti-icing or anti-icing snow covering materials. , Anti-fingerprint materials, anti-fog materials, anti-scaling materials, anti-corrosion materials or water drag reducing materials, etc.; and, the super-hydrophobic material of the present application has the properties of temperature resistance, weather resistance, corrosion resistance, etc., compared with the existing organic-based materials The superhydrophobic material of the present application can be used in a wider range of applications, such as being used in some environments that require high temperature or weather resistance or corrosion resistance, which will not be described here.

Another aspect of the application discloses the preparation method of the superhydrophobic material of the present application, which includes forming a negative surface energy material embedded in a positive surface energy material on a hydrophobic surface by means of instantaneous high pressure.

For example, in one implementation of the present application, a micro-arc oxidation method is specifically used to form the negative surface energy material.

It should be noted that the micro-arc oxidation method is only one way in which the superhydrophobic material can be effectively prepared in one implementation of the present application, and it is not excluded that other one-step or multi-step methods can also be used to prepare the superhydrophobic material in the present application. In an implementation manner of the present application, the temperature of the electrolyte in the micro-arc oxidation method is controlled at 20°C-50°C, the power source is a pulse power source, and the pulse power source processing parameters are, in constant current mode, the current density is 3-10A/dm ² , Processing time 1-30min, frequency 50-3000Hz; or in constant voltage mode, voltage 300-500V, processing time 1-30min, frequency 50-3000Hz. In a further improvement, the electrolyte includes a final concentration of 5-40 g/L phosphate, 1-10 g/L fluoride, and 1-15 g/L ammonium salt, and the solvent is water. Wherein, the phosphate is selected from at least one of sodium hexametaphosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium polyphosphate, trisodium phosphate and sodium pyrophosphate; fluoride is selected from sodium fluoride, potassium fluoride At least one of ammonium fluoride; the ammonium salt is selected from at least one of ferric ammonium oxalate, ammonium oxalate, ammonium chloride, ammonium nitrate, ammonium sulfate, and ammonium carbonate. The pH of the electrolyte is 5-8, and the ionic conductivity of the electrolyte is 5-60mS/cm.

The beneficial effects of this application are:

The super-hydrophobic material of the present application has super-hydrophobic properties without using low-surface-energy organic substances by introducing negative surface energy materials and micro-nano void designs on the hydrophobic surface; and, since no organic substances are used, the present application The superhydrophobic material has good temperature and weather resistance, as well as excellent wear and corrosion resistance.

Description of the drawings

Figure 1 is a cross-sectional SEM image of an inorganic superhydrophobic material prepared in an embodiment;

Figure 2 is a TEM image of the inorganic superhydrophobic material prepared in the embodiment;

Figure 3 is a partial enlarged TEM image of the area ① selected in the TEM image shown in Figure 2;

Figure 4 is a partial enlarged TEM image of the area ② selected in the TEM image shown in Figure 2;

Figure 5 is a diagram of the contact angle of the inorganic superhydrophobic material prepared in the embodiment to water;

Fig. 6 is a graph of corrosion resistance data of inorganic superhydrophobic materials prepared in an embodiment;

Fig. 7 is a data chart of weather resistance of inorganic superhydrophobic materials prepared in Examples.

Detailed ways

Studies have found that the super-hydrophobic properties or super-hydrophobic phenomena of lotus leaves are fundamentally caused by the micro-nano structure on the solid surface and low-surface-energy substances or negative-surface-energy materials. The inventor of the present application discovered during the research process that some metal oxides or their surfaces with specific crystal orientations adsorb -OH groups or other modified groups, the surface energy is greatly reduced, and even negative surface energy, such as theta phase alumina After the adsorption of -OH groups, it exhibits a special negative surface energy. Therefore, this application proposes to modify micro-nano-structured high-surface-energy inorganic oxides or positive-surface-energy materials with low-surface-energy or negative-surface-energy materials through such surface-energy functionalization, which can be used in non-organic materials. Under the circumstances, the preparation of inorganic superhydrophobic materials with high stability is achieved.

Based on the above recognition, this application creatively proposes a new superhydrophobic material, that is, the hydrophobic surface is composed of positive surface energy materials, negative surface energy materials and micro-nano voids.

The super-hydrophobic material of the present application does not need to use organic substances. Therefore, it has temperature resistance, weather resistance, abrasion resistance and corrosion resistance. It is not only resistant to aging, long life, and good mechanical properties, but also can be better used for high temperature or strong corrosion. environment of.

The application will be further described in detail below through specific embodiments and drawings. The following examples only further illustrate the application, and should not be construed as limiting the application.

Example

In this example, an aluminum sheet made of pure aluminum material is used as a substrate, and an aluminum oxide hydrophobic surface is prepared on the surface of the aluminum sheet by a micro-arc oxidation method, thereby obtaining the superhydrophobic material of the present application. Among them, the size of the aluminum sheet is 25×50×2mm ³ .

In the electrolyte for micro-arc oxidation in this example, sodium hexametaphosphate is used for phosphate, sodium fluoride is used for fluoride, and ferric ammonium oxalate is used for ammonium salt. The electrolyte preparation method is as follows: Weigh sodium hexametaphosphate, sodium fluoride and oxalic acid Ferric ammonium, add it to distilled water and stir to dissolve it. So that the final concentration of sodium hexametaphosphate is 10g/L, the final concentration of sodium fluoride is 2g/L, and the final concentration of ferric ammonium oxalate is 4g/L. The electrolyte of this example is obtained.

The micro-arc oxidation method in this example includes:

1) Pretreatment: Grind the aluminum sheet, use sandpaper to remove the surface and corner burrs of the aluminum sheet, remove surface foreign matter, and reduce the roughness of the aluminum sheet; then use the organic solvent 20mL acetone and 50mL ethanol to ultrasonically clean the aluminum sheet in turn For 10 minutes, remove the surface organic contaminants. After that, it is forbidden to directly touch the sample surface with hands to avoid re-contamination; finally, the organic residues on the surface are washed off with deionized water and air-dried.

2) Micro-arc oxidation: immerse the sample in the electrolyte prepared in this example, use 20KW high voltage pulse power, constant current mode, current density 5A/dm ² , frequency 200Hz, and reaction time 8min. The reaction temperature is controlled within 50°C by a cooling system.

3) Post-treatment: the prepared film is washed with deionized water and air-dried naturally to obtain the superhydrophobic material of this example.

The superhydrophobic material of this example was observed by scanning electron microscope, and the result is shown in Figure 1. The results in Figure 1 show that a micro-nano structured aluminum oxide hydrophobic surface is formed on the surface of the aluminum sheet.

A transmission electron microscope was used to observe the superhydrophobic material of this example. The result is shown in Figure 2. In Figure 2, two regions are selected, namely the ① region and the ② region, for further magnification observation; among them, the observation result of the region ① is shown in the figure As shown in Fig. 3, the observation result of ② area is shown in Fig. 4. The results in Figs. 2 to 4 show that the nano alumina of this example contains θ-phase alumina (abbreviated as θ-Al ₂ O ₃ ).

For θ-Al ₂ O ₃ , the 10-2 surface will cause an OH bond in the water molecule to break after adsorbing water molecules, so that the surface will adsorb an OH and an H. This process proceeds spontaneously, and the newly formed OH bond and The Al-O bond compensates for the original broken bond, thereby reducing the energy of the system; through first-principles calculation and simulation, using density functional theory and generalized gradient approximation, the corresponding model is constructed, and E _surf ,

And E _H2O , and, μ _H and μ _O satisfy 2 μ _H + μ _O = E _H2O , taking into formula three, it can be found that the superhydrophobic material of this example has a negative surface energy on its surface.

Formula 3:

A contact angle tester was used to test the hydrophobic contact angle of the superhydrophobic material of this example. The test temperature was room temperature and the water droplet volume was 2 μL. The test result is shown in Fig. 5. The test results show that the superhydrophobic material prepared by micro-arc oxidation in this example has a hydrophobic contact angle of 152° and a sliding angle to water less than 3°, indicating that the superhydrophobic material of this example has good hydrophobicity.

In this example, the aluminum sheet, the superhydrophobic material prepared in this example, and the conventional aluminum sheet with aluminum oxide coating were used for corrosion resistance tests. The corrosion resistance of the three materials under different current densities and voltages was tested. The results As shown in Figure 6. The results in Figure 6 show that the superhydrophobic material prepared in this example has better corrosion resistance.

In addition, in this example, the prepared superhydrophobic material was directly exposed to outdoor air, placed for 360 days, and its hydrophobic contact angle was measured every 30 days. The results are shown in FIG. 7. The results in Fig. 7 show that the hydrophobic contact angle of the superhydrophobic material of this example is exposed to room temperature for 360 days, and its hydrophobic contact angle always remains unchanged, indicating that the superhydrophobic material of this example has good weather resistance.

Since the superhydrophobic material of this example forms a hydrophobic surface of alumina with good hydrophobicity on the surface of the aluminum sheet, the θ-phase alumina with negative surface energy material in the alumina, the Al and O atoms in the surface layer are respectively replaced by the OH in the environment -And H- are completely covered, which eliminates the chemical environment difference between the surface and the body atoms, reduces the internal stress accumulated during the surface formation of alumina, reduces the surface energy that was originally positive to a negative value, and satisfies The superhydrophobic material requires low surface energy; and, due to the rough micro-nano structure of the hydrophobic surface of alumina, while meeting the characteristics of low surface energy and micro-nano structure, the superhydrophobic material of this example exhibits excellent superhydrophobic properties. The super-hydrophobic material of this example has a hydrophobic surface formed by aluminum oxide, which has the characteristics of temperature resistance, weather resistance, wear resistance and corrosion resistance; and the hydrophobic aluminum oxide layer formed directly on the surface of the aluminum sheet has a strong bonding force with the aluminum sheet , Excellent mechanical properties, not easy to age, and long service life.

The above content is a further detailed description of the application in conjunction with specific implementations, and it cannot be determined that the specific implementation of the application is limited to these descriptions. For those of ordinary skill in the technical field to which this application belongs, several simple deductions or substitutions can be made without departing from the concept of this application.

Claims

A super-hydrophobic material, characterized in that: the hydrophobic surface of the super-hydrophobic material is composed of positive surface energy materials, negative surface energy materials and micro-nano voids.
The superhydrophobic material according to claim 1, wherein the negative surface energy material is a material that can interact with water and undergo interface reconstruction to form a new negative surface energy interface.
The superhydrophobic material according to claim 1, wherein the negative surface energy material is a metal oxide, the metal oxide has a specific crystal phase structure, and the specific crystal phase structure can interact with water and pass through The interface is reconstructed to form a new negative surface energy interface.
The superhydrophobic material according to claim 3, wherein the metal oxide is an oxide of at least one of aluminum, copper, zinc, titanium, zirconium, magnesium, iron, and rare earth elements.
The superhydrophobic material according to claim 4, wherein the metal oxide is θ-phase alumina.
The superhydrophobic material according to any one of claims 3-5, characterized in that: the structural formula of the metal oxide is M x O y , where M is aluminum, copper, zinc, titanium, zirconium, magnesium, iron and rare earth One of the elements, O is oxygen, x and y meet the stoichiometric ratio of the structural formula, and the chemical potentials of the elements M and O meet the formula two,

Formula 2:

When the metal oxide is in contact with water and interacts to reconstruct the interface to form a new interface, the element H is introduced, and the surface energy calculation formula of the new interface formed by its reconstruction is Equation 3.

Formula 3:

In formulas 2 and 3, γ is the surface energy, E surf is the total energy of the material when the surface contains a specific crystal phase structure, A is the area of the surface, NM and μ M are respectively the total of the element M in the metal oxide atoms and chemical potential, N O O [mu], respectively, and a metal oxide of the element O and the total number of atoms in chemical potential, N H and H [mu] metal oxide element are H and the total number of atoms in chemical potential, E stio To assume that there is no H element on the surface, the total number of atoms of M is the same as the actual surface, and the surface composition meets the stoichiometric ratio of M x O y , the total energy of the system, n is the total number of atoms of M in the system divided by x,
It is the total energy of the bulk material per unit of chemical formula M x O y , and E w/oH is the total energy of the system assuming that there is no H element on the surface and the total number of atoms of M and O is the same as the actual surface.
The superhydrophobic material according to any one of claims 1-5, wherein the size of the micro-nano voids is 0.1-10 μm.
The superhydrophobic material according to any one of claims 1-7 is used in the preparation of self-cleaning materials, anti-icing or anti-icing and snow covering materials, anti-fingerprint materials, anti-fog materials, anti-scaling materials, anti-corrosion materials or water drag reducing materials In the application.
7. The method for preparing a superhydrophobic material according to any one of claims 1-7, characterized in that it comprises forming a negative surface energy material embedded in a positive surface energy material on a hydrophobic surface by means of instantaneous high pressure.
The preparation method according to claim 9, characterized in that it comprises forming a negative surface energy material by a micro-arc oxidation method.