CN100463858C - Superhydrophobic layered double hydroxyl compound metal oxide film and preparation method thereof - Google Patents

Abstract

The invention relates to a super-hydrophobic layered double-hydroxy compound metal oxide film grown on a surface anodized aluminum substrate and a preparation method thereof. Using in-situ synthesis technology, the layered bishydroxy compound metal oxide film synthesized on the surface of the anodized aluminum sheet has a nano/micro composite structure, and there are micron-scale unevenness on the surface, and the surface of the long-chain fatty acid salt After surface hydrophobic treatment in the active agent solution, it has very superior hydrophobic performance, and the contact angle with water droplets reaches 150-170°. The surfactant solution used does not contain fluorine, has no toxic effect on human body and has no pollution to the environment. The process used in this method is simple, the raw materials are easy to obtain, the cost is low, and the repeatability is good. The prepared film has excellent superhydrophobic and self-cleaning properties. The superhydrophobic layered double hydroxyl composite metal oxide film is expected to be used in engineering materials. Dust-proof and anti-fog protective coating on metal surfaces.

Description

Superhydrophobic layered double hydroxyl compound metal oxide film and preparation method thereof

Technical field:

The invention belongs to the technical field of film materials, and in particular relates to a super-hydrophobic layered double-hydroxy compound metal oxide film grown on a surface anodized aluminum substrate and a preparation method thereof.

technical background:

Layered double hydroxyl compound metal oxides (also known as hydrotalcite-like, LDHs for short) are a kind of anionic layered structure functional materials, which are composed of parallel and positively charged laminates, and the layers are composed of balanced anions and water molecules. . The general formula of its chemical composition is: [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^x+ (A ^n- _x/n ) mH ₂ O, where M ²⁺ and M ³⁺ are respectively located in the laminate The divalent and trivalent metal ions on the surface, ^An- represents the interlayer anion. Due to its unique crystal structure and physical and chemical properties, this kind of material shows extremely broad application prospects in many fields such as ion exchange, adsorption, catalysis, polymer modification, optical materials, magnetic materials, and electrical materials.

In recent years, superhydrophobic surfaces have attracted widespread attention. The so-called super-hydrophobic surface generally refers to the surface with a contact angle with water droplets greater than 150°. It is generally believed that the composite structure combining micrometers and nanometers is the root cause of surface superhydrophobicity, and the resulting superhydrophobic surface has a larger contact angle. The superhydrophobic surface has properties such as waterproof, anti-pollution, anti-oxidation, enhanced biocompatibility, lubricity, and prevention of current conduction. In nature, super-hydrophobic phenomena also exist widely. For example, a super-hydrophobic film exists on the surface of a lotus leaf, which makes it easy for water droplets to roll down on its surface. The sludge and debris are taken away; the wings of butterflies and the feathers of birds also have similar super-hydrophobic structures. Superhydrophobic materials have extremely broad application prospects in industrial and agricultural production and people's daily life. For example: textiles, coatings, gene transfer, microfluidics, and loss-free liquid delivery.

Generally, superhydrophobic surfaces can be prepared by two methods. One is to build a rough structure on the surface of a hydrophobic material (contact angle greater than 90°), which is generally considered to have a micro-nano composite structure, the higher the roughness, the better. The other is to modify the rough surface with low surface energy substances (such as fluorosilane, long-chain fatty acid). At present, most literature reports use the former method to prepare superhydrophobic surfaces. For example: In the literature Angew.Chem.Int.Ed, 2003 (42): 1433 and Angew.Chem.Int.Ed, 2003 (43): 4338, Jiang Lei et al. build roughness on the surface of the hydrophobic polymer film The structure makes the surface of the film exhibit excellent superhydrophobicity. Other methods such as plasma polymerization or etching, microwave plasma-enhanced chemical vapor deposition, anodic oxidation, and template methods can also be classified as the first method. In order to effectively obtain a superhydrophobic surface, it is also necessary to modify the surface with low surface energy substances. Most of the currently used low surface energy substances are fluorine-containing compounds or organosilanes. For example, in the document J.Am.Chem.Soc, 2005(127): 15670, Liu et al. used C ₉ F ₂₀ and PDMSVT (poly(dimethylsiloxane)vinyl terminated) to modify the surface of aluminum and aluminum alloys to obtain a stable super Hydrophobic engineering materials. In the patent No. CN99810647.X, the applicant coated fluorocarbons on the surface-treated substrate to obtain a hydrophobic film with a contact angle greater than 120°.

Due to the increasingly serious damage to the environment of various fluorine compounds, the use of such compounds is currently banned in countries all over the world, so researchers are actively looking for substitutes for fluoride compounds, and the research on super-hydrophobic interface materials is no exception. The layered double hydroxyl composite metal oxide film prepared by us has a micron-scale uneven rough surface, and has excellent hydrophobic properties after surface hydrophobic treatment in an inexpensive long-chain fatty acid salt surfactant solution. The long-chain carboxylic acid surfactant used does not contain fluorine, has no toxic effect on the human body and has no pollution to the environment.

Invention content:

The purpose of the present invention is to provide a super-hydrophobic layered double hydroxyl compound metal oxide film; another purpose is to provide a preparation method for the super-hydrophobic layered double hydroxyl compound metal oxide film.

The superhydrophobic layered double hydroxyl compound metal oxide film provided by the invention is an LDHs film grown on an aluminum substrate after the surface is anodized, and the general chemical formula of the film layer LDHs is:

[M ²⁺ _1-x Al ³⁺ _x (OH) ₂ ] ^x+ (Y ^m- ) _x/m yH ₂ O,

Where M ²⁺ represents any one of divalent metal ions Mg ²⁺ , Co ²⁺ , Ni ²⁺ , Ca ²⁺ , Cu ²⁺ , Fe ²⁺ , Mn ²⁺ , preferably Ni ²⁺ , Co ²⁺ or Mg ²⁺ ; 0.2≤x≤0.4, 0≤y≤2; m is the valence of Y, and Y ^m- represents interlayer anions CO ₃ ^2- , NO ₃ ^- , SO ₄ ^2- , Cl ^- , F ^- or Br ^- ;

The LDHs film has a nano/micro composite structure, and there are micron-scale unevenness on the surface; the LDHs film has superhydrophobic properties after being treated with a water-soluble long-chain fatty acid salt surfactant solution, and its contact angle with a water droplet is within 150～170°;

The chemical formula of the water-soluble long-chain fatty acid salt surfactant is C _n-1 H _2n-1 COO ^- M ⁺ , wherein n=12-22; M ⁺ represents monovalent metal ions K ⁺ , Na ⁺ . A preferred water-soluble long-chain fatty acid salt is one of C ₁₁ H ₂₁ COONa, C ₁₁ H ₂₁ COOK, C ₁₆ H ₃₁ COONa, C ₁₆ H ₃₁ COOK, C ₁₈ H ₃₅ COONa or C ₁₈ H ₃₅ COOK, more Good ones are C ₁₁ H ₂₁ COONa or C ₁₁ H ₂₁ COOK.

The present invention adopts the in-situ synthesis technology to prepare a layered bishydroxy compound metal oxide film on the surface of an anodized aluminum sheet. The LDHs film has a nano/micro composite structure, and there are micron-level unevenness on the surface. The surface of the film is hydrophobically treated with a long-chain fatty acid salt surfactant solution. After the hydrophobic treatment, the surface of the film still maintains this nano/micro composite structure, and a layer is formed between the surface layer of the nano/micro composite structure and the water droplets. Air film, the contact angle with water droplets is as high as 170°, and the sewage splashed on the surface will automatically roll off without leaving any traces, which can achieve the purpose of self-cleaning.

The specific preparation method is as follows:

A. Clean the aluminum sheet with a purity greater than 80% and a thickness of 0.01-1mm with ethanol ultrasonic cleaning for 5-10 minutes, then ultrasonic cleaning with water for 5-10 minutes to remove surface oil, and then use it as an anode on the anodizing device, use lead plate or stainless steel The plate is used as the cathode, the electrolyte is 0.5-3.0mol/L sulfuric acid solution, the oxidation current is 1-5A, the aluminum sheet is anodized for 30-100min and then taken out, and the electrolyte is washed away with deionized water to obtain anodized aluminum sheet for later use ;

B. Dissolve ammonium nitrate and soluble divalent inorganic salt M ²⁺ Y ^m- _2/m in deionized water at a molar ratio of 3 to 30, and control the concentration of M ²⁺ metal ions at 0.01 to 0.5 mol/L, and use 1 % dilute ammonia water to adjust the pH value of the reaction solution to 4.5 to 10 to obtain the reaction solution;

C. Suspend the anodized aluminum substrate in the reaction solution, react at 25-180°C for 0.5-96 hours, take out the aluminum substrate, rinse with ethanol solution, and dry at room temperature to obtain a layered bismuth Hydroxyl complex metal oxide (LDHs) thin film;

D. Suspend the prepared layered double hydroxy compound metal oxide (LDHs) film in a 0.001-0.5mol/L surfactant solution, react at 25-100°C for 0.5-20 hours, long-chain fatty acids The salt combines with the hydroxyl groups on the surface of the hydrotalcite to form a covalent bond. After the film is taken out, it is rinsed with ethanol and dried at room temperature to obtain a layered double-hydroxy compound metal oxide (LDHs) film with superhydrophobic properties.

M ²⁺ in step B is any one of Mg ²⁺ , Co ²⁺ , Ni ²⁺ , Ca ²⁺ , Cu ²⁺ , Fe ²⁺ , Mn ²⁺ , preferably Ni ²⁺ , Co ^{2 +} or Mg ²⁺ , Y ^m- is any one of CO ₃ ^2- , NO ₃ ^- , SO ₄ ^2- , Cl ^- , F ^- , Br ^- , preferably CO ₃ ^2- , NO ₃ ^- or Cl ^- ; the preferred pH range of the reaction solution is 5.5-8.5.

The preferred reaction condition of step C is to react at 50-150°C for 3-60 hours, and the better reaction condition is to react at 50-130°C for 5-20 hours.

The surfactant solution described in step D is a water-soluble long-chain fatty acid salt satisfying the following conditions, and its chemical formula is C _n-1 H _2n-1 COO ^- M ⁺ , wherein n=12-22; M ⁺ represents monovalent Metal ion K ⁺ , Na ⁺ ; preferably sodium or potassium laurate (C ₁₁ H ₂₁ COONa or C ₁₁ H ₂₁ COOK), sodium or potassium palmitate (C ₁₆ H ₃₁ COONa or C ₁₆ H ₃₁ COOK), sodium or potassium stearate (C ₁₈ H ₃₅ COONa or C ₁₈ H ₃₅ COOK)); most preferred is sodium or potassium laurate.

The preferable reaction condition of step D is to react at 25-80°C for 0.5-10 hours, and the more preferable reaction condition is to react at 30-50°C for 2-5 hours.

The surface morphology of the super-hydrophobic film was observed by a Japanese HITACHI S-3500N scanning electron microscope (SEM) (all SEM samples were sprayed with gold for clearer photos). Fig. 1 is the SEM photo of the surface of the aluminum sheet after surface anodization obtained in step A of embodiment 1, and Fig. 2 is the SEM photo of the surface of the LDHs film sample prepared in step C of embodiment 1. It can be clearly seen from Figure 2 that there is a layer of hexagonal flakes on the surface of anodized aluminum, that is, the formed LDHs film layer, and the hexagonal flake grains of hydrotalcite grow vertically on the surface of the substrate, and the hexagonal vertices are The nanoscale range, while the hexagonal sides are in the micron range, this nano/micro composite structure leads to a high degree of roughness in the film, and the hexagonal sheets in the film layer are interlaced to form a bird's nest special shape of the shape. The thickness of the LDHs layer is about 1.5 μm. Fig. 3 is the SEM photograph of the superhydrophobic LDHs film sample prepared in step D of embodiment 1. Comparing Figure 2 and Figure 3, it can be found that the morphology of the film after hydrophobization treatment has basically no change compared with that before treatment, and still maintains the bird's nest shape.

The contact angle between the obtained superhydrophobic LDHs films and water droplets was measured by DSA100 drop shape analysis system from KRüSS GmbH, Germany. The same film sample surface was measured five times and the average value was taken as the final contact angle measurement. Fig. 4 is the optical photo of water droplet on the superhydrophobic LDHs film sample surface that embodiment 1 prepares. Fig. 5 is the physical photo of the superhydrophobic LDHs film sample prepared by water droplets in step D of embodiment 1.

The beneficial effects of the present invention are: the prepared layered double hydroxyl compound metal oxide film has a nano/micro composite structure, and there are micron-level uneven undulations on the surface, and the surface is carried out in a long-chain fatty acid salt surfactant solution. After hydrophobic treatment, it has very superior hydrophobic performance, and the contact angle with water droplets is as high as 170°. The surfactant solution used does not contain fluorine, has no toxic effect on the human body and has no pollution to the environment. The process used in this method is simple, the raw materials are easily obtained, the cost is low, and the reproducibility is good. The prepared film has excellent superhydrophobic and self-cleaning properties. The superhydrophobic layered double hydroxyl composite metal oxide film is expected to be used as a Dust-proof and anti-fog protective coating on the surface is used.

Description of drawings

Fig. 1 is the SEM photograph of the aluminum flake surface after the surface anodic oxidation of embodiment 1 step A gained;

Fig. 2 is the surface SEM photograph of the LDHs film sample that embodiment 1 step C obtains;

Fig. 3 is the SEM photograph of the superhydrophobic LDHs thin film sample that embodiment 1 step D obtains.

Fig. 4 is the optical photo of water droplet on the superhydrophobic LDHs film sample surface that embodiment 1 prepares.

Fig. 5 is the physical photograph of the superhydrophobic LDHs film sample that water droplet is prepared in embodiment 1.

Detailed ways:

Below in conjunction with embodiment the present invention will be further described:

Example 1:

A. The aluminum sheet with a thickness of 0.1mm (purity is 99.5%) is ultrasonically cleaned with ethanol for 5 minutes, then ultrasonically cleaned with water for 5 minutes to remove surface oil, and then anodized on an anodizing device for 50 minutes, the aluminum sheet is taken out, and cleaned with deionized water Rinse off the electrolyte to obtain anodized aluminum sheets for use. The anodizing device uses a lead plate or a stainless steel plate as the cathode, the electrolyte is a 1.0mol/L sulfuric acid solution, and the oxidation current is 2A.

B. In a 1L Erlenmeyer flask, dissolve 1mol Ni(NO ₃ ) ₂ ·6H ₂ O and 6mol NH ₄ NO ₃ in deionized water, and adjust the pH of the solution to 7.5 with 1% dilute ammonia water.

C. Suspend the anodized aluminum substrate in the solution, seal the container, and react at a constant temperature of 45°C for 36 hours. After the reaction, take out the aluminum substrate, rinse it with deionized water, and then rinse it with ethanol , and dried at room temperature to obtain LDHs film.

D. Suspend the above-mentioned LDHs film in 0.05mol/L sodium laurate (C ₁₁ H ₂₁ COONa) aqueous solution at 25°C for a monolayer self-assembly reaction for 5 hours, take out the film, rinse it with ethanol, and dry it at room temperature to obtain Superhydrophobic LDHs film.

The SEM photo of the surface of the obtained aluminum sheet after anodic oxidation is shown in FIG. 1 , and the SEM photo of the LDHs thin film is shown in FIG. 2 . The SEM photograph of the superhydrophobic LDHs film sample is shown in Figure 3. The optical photograph of water droplets on the surface of the superhydrophobic LDHs film sample is shown in Figure 4. The physical picture of water droplets on the surface of the film is shown in Figure 5. The measured contact angle of water droplets on the surface of the film is 165±3°.

Example 2:

A. The aluminum sheet with a thickness of 0.1mm (purity is 99.5%) is ultrasonically cleaned with ethanol for 5 minutes, then ultrasonically cleaned with water for 5 minutes to remove surface oil, and then anodized on an anodizing device for 50 minutes, the aluminum sheet is taken out, and cleaned with deionized water Rinse off the electrolyte to obtain anodized aluminum sheets for use. The anodizing device uses a lead plate or a stainless steel plate as the cathode, the electrolyte is a 1.0mol/L sulfuric acid solution, and the oxidation current is 2A.

B. In a 1L Erlenmeyer flask, dissolve 2mol Ni(NO ₃ ) ₂ ·6H ₂ O and 12mol NH ₄ NO ₃ in deionized water, and adjust the pH of the solution to 8.5 with 1% dilute ammonia water.

C. Suspend the anodized aluminum substrate in the solution, seal the container, and react at a constant temperature of 75°C for 24 hours. After the reaction is completed, take out the aluminum substrate, rinse it with deionized water, and then rinse it with ethanol , and dried at room temperature to obtain LDHs film.

D. Suspend the above LDHs film in 0.005 mol/L sodium stearate (C ₁₈ H ₃₅ COONa) aqueous solution at 80°C for 10 hours of monolayer self-assembly reaction, take out the film, rinse with ethanol, and dry at room temperature A superhydrophobic LDHs film was obtained. The measured contact angle of water droplets on the surface of the film is 153±3°.

Example 3:

A. The aluminum sheet with a thickness of 0.1mm (purity is 99.5%) is ultrasonically cleaned with ethanol for 5 minutes, then ultrasonically cleaned with water for 5 minutes to remove surface oil, and then anodized on an anodizing device for 50 minutes, the aluminum sheet is taken out, and cleaned with deionized water Rinse off the electrolyte to obtain anodized aluminum sheets for use. The anodizing device uses a lead plate or a stainless steel plate as the cathode, the electrolyte is a 1.0mol/L sulfuric acid solution, and the oxidation current is 2A.

B. In a 1L Erlenmeyer flask, dissolve 0.5Co(NO ₃ ) ₂ ·6H ₂ O and 6mol NH ₄ NO ₃ in deionized water, and adjust the pH of the solution to 6.5 with 1% dilute ammonia water.

C. Suspend the anodized aluminum substrate in the solution, seal the container, and react at a constant temperature of 45°C for 21 hours. After the reaction, take out the aluminum substrate, rinse it with deionized water, and then rinse it with ethanol , and dried at room temperature to obtain LDHs film.

D. Suspend the above-mentioned LDHs film in 0.025mol/L potassium laurate (C ₁₁ H ₂₁ COOK) aqueous solution at 40°C for a monolayer self-assembly reaction for 5 hours, take out the film, rinse it with ethanol, and dry it at room temperature to obtain Superhydrophobic LDHs film. The contact angle of water droplets on the film surface is 167±3°.

Example 4:

A. The aluminum sheet with a thickness of 0.5mm (purity is 80%) is ultrasonically cleaned with ethanol for 10 minutes, then ultrasonically cleaned with water for 5 minutes to remove surface oil, and then anodized on an anodizing device for 100 minutes, the aluminum sheet is taken out, and deionized water is used to clean the aluminum sheet. Rinse off the electrolyte to obtain anodized aluminum sheets for use. The anodizing device uses a lead plate or a stainless steel plate as the cathode, the electrolyte is 2.0mol/L sulfuric acid solution, and the oxidation current is 2A.

B. In a 1L Erlenmeyer flask, dissolve 1mol Co(NO ₃ ) ₂ ·6H ₂ O and 12mol NH ₄ NO ₃ in deionized water, and adjust the pH of the solution to 6.8 with 1% dilute ammonia water.

C. Suspend the anodized aluminum substrate in the solution, seal the container, and react at a constant temperature of 90°C for 28 hours. After the reaction, take out the aluminum substrate, rinse it with deionized water, and then rinse it with ethanol , and dried at room temperature to obtain LDHs film.

D. Suspend the above LDHs film in 0.0025mol/L potassium stearate (C ₁₈ H ₃₅ COOK) aqueous solution and carry out self-assembly reaction at 70°C for 2 hours, take out the film, rinse with ethanol, and dry at room temperature to obtain super Hydrophobic LDHs film. The measured contact angle of water droplets on the surface of the film is 154±3°.

Example 5:

A. The aluminum sheet with a thickness of 0.5mm (purity is 80%) is ultrasonically cleaned with ethanol for 10 minutes, then ultrasonically cleaned with water for 5 minutes to remove surface oil, and then anodized on an anodizing device for 100 minutes, the aluminum sheet is taken out, and deionized water is used to clean the aluminum sheet. Rinse off the electrolyte to obtain anodized aluminum sheets for use. The anodizing device uses a lead plate or a stainless steel plate as the cathode, the electrolyte is a 1.5mol/L sulfuric acid solution, and the oxidation current is 2A.

B. In a 1L Erlenmeyer flask, dissolve 0.8mol Co(NO ₃ ) ₂ ·6H ₂ O and 5mol NH ₄ NO ₃ in deionized water, and adjust the pH of the solution to 5.0 with 1% dilute ammonia water.

C. Suspend the anodized aluminum substrate in the solution, seal the container, and react at a constant temperature at 60°C for 16 hours. After the reaction is completed, take out the aluminum substrate, rinse it with deionized water, and then rinse it with ethanol , and dried at room temperature to obtain LDHs film.

D. Suspend the above LDHs film in 0.02mol/L sodium palmitate (C ₁₆ H ₃₁ COONa) in an aqueous solution at 45°C for self-assembly reaction for 8 hours, rinse with ethanol, and dry at room temperature to obtain superhydrophobic LDHs film. The measured contact angle of water droplets on the surface of the film is 158°±3°.

Embodiment 6:

A. The aluminum sheet with a thickness of 0.5mm (purity is 80%) is ultrasonically cleaned with ethanol for 10 minutes, then ultrasonically cleaned with water for 5 minutes to remove surface oil, and then anodized on an anodizing device for 100 minutes, the aluminum sheet is taken out, and deionized water is used to clean the aluminum sheet. Rinse off the electrolyte to obtain anodized aluminum sheets for use. The anodizing device uses a lead plate or a stainless steel plate as the cathode, the electrolyte is a 1.5mol/L sulfuric acid solution, and the oxidation current is 2A.

B. In a 1L Erlenmeyer flask, dissolve 1mol Co(NO ₃ ) ₂ ·6H ₂ O and 6mol NH ₄ NO ₃ in deionized water, and adjust the pH of the solution to 8.2 with 1% dilute ammonia water.

C. Suspend the anodized aluminum substrate in the solution, seal the container, and react at a constant temperature of 80°C for 17 hours. After the reaction is completed, take out the aluminum substrate, rinse it with deionized water, and then rinse it with ethanol , and dried at room temperature to obtain LDHs film.

D. Suspend the above-mentioned LDHs film in 0.1mol/L potassium palmitate (C ₁₆ H ₃₁ COOK) aqueous solution at 60°C for 5 hours for self-assembly reaction, then rinse with ethanol, and dry at room temperature to obtain superhydrophobic LDHs film. The contact angle of water droplets on the surface of the film is 151°±2°.

Claims (8)

1. A super-hydrophobic layered double hydroxyl compound metal oxide film is a LDHs film grown on the surface through anodized aluminum flakes, wherein the LDHs film refers to a layered double hydroxyl compound metal oxide, the chemical composition of the film layer LDHs The general formula is: [M ²⁺ _1-x Al ³⁺ _x (OH) ₂ ] ^x+ (Y ^m- ) _x/m yH ₂ O, Where M ²⁺ represents any one of divalent metal ions Mg ²⁺ , Co ²⁺ , Ni ²⁺ , Ca ²⁺ , Cu ²⁺ , Fe ²⁺ , Mn ²⁺ ; m is the valence of Y, Y ^m- stands for interlayer anion CO ₃ ^2- , NO ₃ ^- , SO ₄ ^2- , Cl ^- , F ^- or Br ^- ; 0.2≤x≤0.4, 0≤y≤2; The LDHs film has a nano- and micro-composite structure, and there are micron-scale unevenness on the surface; the LDHs film is treated with a water-soluble long-chain fatty acid salt surfactant solution to have super-hydrophobic properties, and its contact angle with water droplets is in 150～170°; The chemical formula of the water-soluble long-chain fatty acid salt surfactant is C _n-1 H _2n-1 COO ^- M ⁺ , wherein n=12-22; M ⁺ represents monovalent metal ion K ⁺ or Na ⁺ . 2. A superhydrophobic layered double hydroxyl compound metal oxide film as claimed in claim 1, wherein said LDHs film has passed through C ₁₁ H ₂₁ COONa, C ₁₁ H ₂₁ COOK, C ₁₆ H ₃₁ COONa , C ₁₆ H ₃₁ COOK, C ₁₈ H ₃₅ COONa or C ₁₈ H ₃₅ COOK water-soluble long-chain fatty acid salt treatment; said M ²⁺ is Ni ²⁺ , Co ²⁺ or Mg ²⁺ ; Y ^m- is CO ₃ ^2- , NO ₃ ^- or Cl ^- . 3. A superhydrophobic layered double hydroxyl compound metal oxide film as claimed in claim 1, characterized in that the LDHs film has been treated with C ₁₁ H ₂₁ COONa or C ₁₁ H ₂₁ COOK. 4. a kind of preparation method of superhydrophobic layered double hydroxyl composite metal oxide film as claimed in claim 1, concrete steps are as follows: A. Clean the aluminum sheet with a purity greater than 80% and a thickness of 0.01-1mm with ethanol ultrasonic cleaning for 5-10 minutes, then ultrasonic cleaning with water for 5-10 minutes to remove surface oil, and then use it as an anode on the anodizing device, use lead plate or stainless steel The plate is used as the cathode, the electrolyte is 0.5-3.0mol/L sulfuric acid solution, the oxidation current is 1-5A, the aluminum sheet is anodized for 30-100min and then taken out, and the electrolyte is washed away with deionized water to obtain anodized aluminum sheet for later use ; B. Dissolve ammonium nitrate and soluble divalent inorganic salt M ²⁺ Y ^m- _2/m in deionized water at a molar ratio of 3 to 30, and control the concentration of M ²⁺ metal ions at 0.01 to 0.5 mol/L, and use 1 % dilute ammonia water to adjust the pH value of the reaction solution to 4.5 to 10 to obtain the reaction solution; M ²⁺ in soluble divalent inorganic salt M ²⁺ Y ^m- _2/m is any one of Mg ²⁺ , Co ²⁺ , Ni ²⁺ , Ca ²⁺ , Cu ²⁺ , Fe ²⁺ , Mn ²⁺ species, Y ^m- is any one of CO ₃ ^2- , NO ₃ ^- , SO ₄ ^2- , Cl ^- , F ^- , Br ^- ; C. Suspend the anodized aluminum sheet in the reaction solution, react at 25-180°C for 0.5-96 hours, take out the aluminum sheet, rinse it with ethanol solution, and dry it at room temperature to obtain a layered dihydroxy compound metal oxide film; D. Suspend the prepared layered double hydroxyl compound metal oxide film in the water-soluble long-chain fatty acid salt surfactant solution of 0.001～0.5mol/L, react at 25～100°C for 0.5～20 hours, The long-chain fatty acid salt combines with the hydroxyl group on the surface of the layered double hydroxyl composite metal oxide to form a covalent bond. After the film is taken out, it is rinsed with ethanol and dried at room temperature to obtain a layered double hydroxyl composite metal oxide film with superhydrophobic properties. ; The water-soluble long-chain fatty acid salt described in step D has a chemical formula of C _n-1 H _2n-1 COO ^- M ⁺ , wherein n=12-22; M ⁺ represents a monovalent metal ion K ⁺ or Na ⁺ . 5. The preparation method of the superhydrophobic layered double hydroxyl compound metal oxide film according to claim 4 is characterized in that: in step B, M ²⁺ is Ni ²⁺ , Co ²⁺ or Mg ²⁺ ; Y ^m- It is CO ₃ ^2- , NO ₃ ^- or Cl ^- ; the pH range of the reaction solution is 5.5-8.5; The reaction condition of step C is to react at 50-150° C. for 3-60 hours; The water-soluble long-chain fatty acid salt described in step D is sodium laurate, potassium laurate, sodium palmitate, potassium palmitate, sodium stearate or potassium stearate. 6. The preparation method of the superhydrophobic layered double hydroxyl compound metal oxide film according to claim 4, characterized in that: the reaction condition of step C is to react at 50～130°C for 5～20 hours; The water-soluble long-chain fatty acid salt described in step D is sodium laurate or potassium salt. 7. The method for preparing a superhydrophobic layered bishydroxy compound metal oxide film according to claim 4, characterized in that the reaction condition of step D is to react at 25-80° C. for 0.5-10 hours. 8. The method for preparing a superhydrophobic layered double hydroxyl compound metal oxide film according to claim 4, characterized in that the reaction condition of step D is to react at 30-50° C. for 2-5 hours.

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