WO2008151495A1 - Super-hydrophobic double-layered-hydroxides thin film and the method for making the same - Google Patents

Abstract

A super-hydrophobic double-layered-hydroxides thin film formed on an anodized Al substrate and the method for making the same are disclosed. The making method involves an in-situ technology, wherein, the double-layered-hydroxides thin film formed on an anodized Al sheet has a nano/micro composite structure and its surface roughness is 250-860 nm. After a hydrophobic treatment carried out in a solution containing surfactant which is substantially a long-chain aliphatic salt, the film has superior hydrophobic property, and the contact angle with water can be up to 150-170°. The surfactant used is free of fluorine, and it neither poison the human-being nor pollute the environment. The present method uses a simple process and easy- obtainable material, and it needs lower cost and has good reproducibility. The film obtained has super-hydrophobic and self-cleaning performance. The super-hydrophobic double-layered-hydroxides thin film has the prosperity to be used into the engineering materials as a coating to protect the metal surface from dust and fog etc.

Description

 Superhydrophobic layered bishydroxy composite metal oxide film and preparation method thereof

 The invention belongs to the technical field of thin film materials, and particularly relates to a superhydrophobic layered bishydroxy composite metal oxide film grown on an anodized aluminum substrate and a preparation method thereof. technical background:

· m¾0， 其中 M²⁺、 M³⁺分别是位于层板上的二价、 三价金属离子， Aⁿ_代表层间阴离 子。 这类材料由于其独特的晶体结构和物化特性使其在离子交换、 吸附、 催 化、 高分子改性、 光学材料、 磁学材料、 电学材料等许多领域展现出极为广 阔的应用前景。 Layered bishydroxy composite metal oxides (also known as hydrotalcites, LDHs) are a class of anionic layered functional materials consisting of parallel and positively charged layers composed of balanced anions and water molecules. . Its chemical composition is:

· m3⁄40, where M ²⁺ and M ³⁺ are respectively divalent and trivalent metal ions on the laminate, and A ⁿ _ represents an interlayer anion. Due to its unique crystal structure and physicochemical properties, these materials have shown great 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. By superhydrophobic surface is generally meant a surface having a contact angle with water droplets greater than 150°. It is generally believed that the composite structure in which micro and nano are combined is the root cause of superhydrophobic surface, and thus the superhydrophobic surface has a large contact angle. The superhydrophobic surface is also water resistant, anti-pollution, anti-oxidant, biocompatible, lubricious and resistant to current conduction. In nature, superhydrophobicity is also widespread. For example, the lotus leaf has a superhydrophobic film on its surface, so that the water droplets are easy to roll on its surface, and the water droplets can roll off while still on the surface of the lotus leaf. Sludge debris and other things are taken away; butterfly wings and bird feathers also have similar superhydrophobic 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 lossless liquid transport.

1433 和 Angew.Chem.Int.Ed,2 03 (43):4338中， 江雷等人在疏水性的高分子材料薄膜 表面构建粗糙结构使得薄膜表面显示出优异的超疏水性能。其它方法如离子 体聚合或刻蚀、 微波等离子体增强化学气相沉积、 阳极氧化以及模板法也都 可以归属为第一种方法。 为了有效得到超疏水表面， 用低表面能物质对表面 进行修饰也是非常有必要的。当前所采用的低表面能物质多是含氟化合物或 有机硅垸。 如文献 ^77.0^/77.>¾^,2005(127): 15670中， Liu等人采用 C₉F₂₀和 PDMSVT ( oly(dimethylsiloxane)vinyl terminated )对铝和铝合金表面进行修 饰得到了性能稳定的超疏水工程材料。 专利号为 CN99810647.X的专利中， 申请人将氟代烃涂敷在表面处理后的底材上得到了接触角大于 120°的疏水 性薄膜。 In general, superhydrophobic surfaces can be prepared by two methods. One is in a hydrophobic material The antennae are larger than 90°. When a rough structure is formed on the surface and it is generally considered to have a micron and nano composite structure, the higher the roughness, the better. The other is to modify the rough surface with low surface energy materials such as fluorosilicone and long chain fatty acids. Most of the literature reports currently use the former method to prepare superhydrophobic surfaces. For example: in the literature

1433 and Angew. Chem. Int. Ed, 2 03 (43): 4338, Jiang Lei et al. constructed a rough structure on the surface of a hydrophobic polymer material film to make the surface of the film exhibit excellent superhydrophobic properties. Other methods such as ion polymerization or etching, microwave plasma enhanced chemical vapor deposition, anodization, and templating can also be assigned to the first method. In order to effectively obtain a superhydrophobic surface, it is also necessary to modify the surface with a low surface energy substance. The low surface energy materials currently used are mostly fluorine-containing compounds or silicone germanium. As in the literature ^77.0^/77.>3⁄4^, 2005(127): 15670, Liu et al. used C ₉ F ₂₀ and PDMSVT ( oly(dimethylsiloxane) vinyl terminated ) to modify the surface of aluminum and aluminum alloy to obtain stable performance. Superhydrophobic engineering materials. In the patent No. CN99810647.X, the applicant applied a fluorohydrocarbon to a surface treated substrate to obtain a hydrophobic film having a contact angle of more than 120°.

 Due to the increasingly serious environmental damage caused by various fluorine compounds, the use of such compounds is banned in countries all over the world, so researchers are actively looking for alternatives to fluoride, and research on superhydrophobic interface materials is no exception. Summary of the invention:

 SUMMARY OF THE INVENTION An object of the present invention is to provide a superhydrophobic layered bishydroxy composite metal oxide film; another object is to provide a method for preparing the superhydrophobic layered bishydroxy composite metal oxide film.

 The superhydrophobic layered bishydroxy composite metal oxide film provided by the invention is an LDHs film grown on an anodized aluminum substrate, and the chemical formula of the LDHs film is:

[M ²⁺ Al ³⁺ _x (OH) ₂ r(C0 ₃ ² -) _x/ j3⁄40,

Wherein M ²⁺ represents a divalent metal ion, and may be, for example, Mg ²⁺ , Co ²⁺ , M ²⁺ , Ca ²⁺ , Cu ²⁺ , Any one of Fe ²⁺ and Mn ²⁺ , wherein Ni ²⁺ , Co ²⁺ or Mg ²⁺ is preferred; wherein Al ³⁺ is formed in situ from A1 on the aluminum substrate; 0.2 x 0.4, 0^^2;

 The LDHs film has a nano/micro composite structure and a surface roughness of 250 nm to 860 nm; the contact angle of the superhydrophobic LDHs film with water droplets is 150 to 170°.

 The LDHs film has a nano/micro composite structure and is formed on the surface of the substrate.

In the LDHs film layer, the hydrotalcite hexagonal flaky crystal grains are vertically grown on the surface of the substrate, and the thickness of the hexagonal flaky crystal grains is in the nanometer scale range (60 to 80 nm), and the hexagonal flaky crystal grains are respectively The length of the sides is in the micron range (0.5 to 1.5 μπι).

 The LDHs film has a superhydrophobic property after being treated with a water-soluble long-chain fatty acid salt (chemical formula: CwH^COCTM^ wherein n=12~22; M÷ represents a monovalent metal ion K+ and/or Na+). Thereby obtaining the superhydrophobic LDHs film.

 The specific steps of the preparation method of the superhydrophobic layered bishydroxy composite metal oxide film provided by the present invention are as follows:

 A. The aluminum substrate with a purity greater than 80% and a thickness of 0.01~1mm is first ultrasonically cleaned with ethanol for 5~10min, then ultrasonically cleaned with water for 5~10min to remove surface oil, then used as an anode on the anodizing device, with lead plate or The stainless steel plate is used as the cathode, the electrolyte is 0.5~3.0 mol/L sulfuric acid solution, the oxidation current is 1~5A, the aluminum piece is anodized for 30~100min, and then taken out, and the electrolyte is washed away with deionized water to obtain anodized aluminum base. Slice spare

B. Dissolving ammonium nitrate and soluble divalent inorganic salt M ²⁺ Y in deionized water at a molar ratio of 3 to 30, controlling the concentration of M ²⁺ metal ions to 0.01 to 0.5 mol/L, and adjusting the pH value with ammonia water to 4.5. ~

10, obtaining a reaction solution;

 C. The surface anodized aluminum substrate is suspended in the reaction solution, and reacted at 25 to 180 ° C for 0.5 to 96 hours. The aluminum substrate is taken out, rinsed with an ethanol solution, and dried at room temperature to obtain a layered layer. Dihydroxy complex metal oxide (LDHs) film;

D. Suspending the prepared layered bishydroxy-complex metal oxide (LDHs) film in 0.001~ 0.5 mol/L of the surfactant solution is reacted at 25 to 100 ° C for 0.5 to 20 hours, and the long-chain fatty acid salt is combined with the hydroxyl group of the hydrotalcite to form a covalent bond, and the film is taken out and rinsed with ethanol at room temperature. Drying gives a layered bishydroxy-complex metal oxide (LDHs) film having superhydrophobic properties.

In the step B, M ²⁺ is any one of Mg ²⁺ , Co ²⁺ , Ni ²⁺ , Ca ²⁺ , Cu ²⁺ , Fe ²⁺ and Mn ²⁺ , preferably Ni ²⁺ , Co ²⁺ or Mg ²⁺ _; Y is any one of C0 ₃ ² —, N0 ₃ _, S0 ₄ ² _, Cl_, F and Br—, preferably C0 ₃ ² —, N0 ₃ — or Cl— _The preferred pH range of the reaction solution is 5.5 to 8.5. The concentration of the ammonia water in the step B may be 0.1 to 5% by weight, preferably 0.5 to 3 Torr. The preferred reaction condition is to carry out the reaction at 50 to 150 ° C for 3 to 60 hours, and the preferred reaction conditions are 50~: Reaction at 130 ° C for 5 to 20 hours.

The surfactant solution described in the step D is a water-soluble long-chain fatty acid salt having a chemical formula of C^HnCOO-M^ wherein n=12~22; M÷ represents a monovalent metal ion K+ and/or Na+ _; preferably sodium or potassium laurate (C„H ₂₃ COONa or CuifeCOOK sodium or potassium salt (C ₁₅ H ₃₁ COONa or C ₁₅ H ₃₁ COOK ), sodium or potassium stearate Salt (C ₁₇ H ₃₅ COONa or C ₁₇ H ₃₅ COOK); the most preferred is sodium laurate or potassium salt.

 Step D The preferred reaction conditions are a reaction at 25 to 80 ° C for 0.5 to 10 hours, and a more preferred reaction condition is a reaction at 30 to 50 ° C for 2 to 5 hours.

The invention has the beneficial effects that: the invention adopts an in-situ synthesis technique to prepare a layered bishydroxy composite metal oxide film on an aluminum sheet having anodized surface, and the layered bishydroxy composite metal oxide film obtained has the obtained layer. Nano/micro composite structure with a surface roughness of 250 nm to 860 nm. The surface of the film after surface hydrophobic treatment in a long-chain fatty acid surfactant solution still maintains this nano/micro composite structure, at nano/ A gas film is formed between the surface layer of the micro-composite structure and the water droplets, and the contact angle with the water droplets is as high as 170°, and the sewage splashes onto the surface to automatically roll off without leaving any traces, thereby achieving the purpose of self-cleaning. The surfactant solution used is not fluorine-containing, and is not available to the human body. Any toxic effect and no pollution to the environment. The method is simple, the raw materials are easy to obtain, the cost is low, and the repeatability is good. The obtained film has excellent superhydrophobicity and self-cleaning performance, and the superhydrophobic layered bishydroxy composite metal oxide film is expected to be used as a metal in engineering materials. The surface is protected against dust and fog. BRIEF DESCRIPTION OF THE DRAWINGS:

 1 is a SEM photograph of the surface of the surface anodized aluminum sheet obtained in Example A, Step A; FIG. 2 is a surface SEM photograph of the LDHs film sample obtained in Example 1, Step C; FIG. 3 is a first embodiment. SEM photograph of the superhydrophobic LDHs film sample obtained by D; Fig. 4 is an optical photograph of the surface of the superhydrophobic LDHs film sample prepared by the water droplets in Example 1; Fig. 5 is the object of the water droplet on the surface of the superhydrophobic LDHs film sample prepared in Example 1. photo. detailed description:

The present invention will be further described below in conjunction with the embodiments:

Example 1

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

B. Dissolve 1 mol of Ni(N0 ₃ ) ₂ · 63⁄40 and 6 mol of N3⁄4N0 ₃ in deionized water in a 10 L Erlenmeyer flask with a nickel ion concentration of 0.1 mol/L and adjust with 1% dilute ammonia water. The pH of the solution was 7.5.

C. Suspend the surface anodized aluminum substrate in the solution of B. After sealing the container, react at a constant temperature of 45 °C for 36 hours. After the reaction is completed, remove the aluminum substrate and rinse with deionized water. It is clean, rinsed with ethanol, and air-dried at room temperature to obtain a LDHs film.

 D. The above LDHs film was suspended in 0.05 mol/L sodium laurate (Cui^COONa) aqueous solution at 25 °C for 5 hours, and the film was taken out, rinsed with ethanol, and dried at room temperature. A hydrophobic LDHs film.

 The surface morphology of the superhydrophobic film was observed by a Japanese HITACHI S-3500N scanning electron microscope (SEM) (all SEM samples were sprayed with gold for clearer photos). BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a SEM photograph of the surface of an aluminum sheet after surface anodization obtained in Example 1, and Figure 2 is a SEM photograph of a surface of a sample of LDHs prepared in Example 1 and Example C. It can be clearly seen from Fig. 2 that a hexagonal sheet-like substance exists on the surface of the anodized aluminum, that is, a thin film layer of LDHs is formed, and the hexagonal flaky crystal grains of the hydrotalcite are vertically grown on the surface of the substrate, and hexagonal plate crystals are formed. The thickness of the particles is in the nanometer scale range (60~80 nm), and the length of each side of the hexagonal flake grains is in the micrometer range.

(0.5~1 μπι), this nano/micro composite structure leads to a high degree of roughness of the film, and the hexagonal piece and the piece in the film layer are interlaced to form a bird's nest-like special shape. The LDHs thin film layer has a thickness of about 1.5 μm. Figure 3 is a SEM photograph of a superhydrophobic LDHs film sample prepared in Example 1, Step D. Comparing Fig. 2 and Fig. 3, it can be found that the morphology of the hydrophobized film is substantially unchanged from that before the treatment, and the bird's nest morphology is maintained.

 The contact angle of the resulting superhydrophobic LDHs film with water droplets was measured using a DSA100 drop profile analysis system from KRiiSS GmbH, Germany. The surface of the same film sample was measured five times and the average value was taken as the final contact angle measurement. The contact angle of the water droplets on the surface of the resulting superhydrophobic LDHs film was measured to be 165 ± 3 °. Figure 4 is an optical photograph of the surface of a superhydrophobic LDHs film sample prepared by water droplets in Example 1. Fig. 5 is a physical photograph of a superhydrophobic LDHs film sample prepared by water droplets in Example 1.

The surface roughness of the LDHs film samples obtained by the step C was 477.34 nm using a Digital Nanoscope III atomic force microscope (AFM) from Veeco, USA. Example 2:

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

B. Dissolve 2 mol of Ni(N0 ₃ ) ₂ · 63⁄40 and 12 mol of N3⁄4N0 ₃ in deionized water in a 10 L Erlenmeyer flask with a nickel ion concentration of 0.2 mol/L and adjust the solution with 1% by weight of dilute ammonia water. The pH is 8.5.

 C. Suspend the surface anodized aluminum substrate in a solution, seal the container, and react at a constant temperature of 75 ° C for 24 hours. After the reaction is completed, remove the aluminum substrate, rinse it with deionized water, and then use ethanol. Rinse and dry at room temperature to obtain a LDHs film. The surface roughness of the LDHs film sample was measured to be 351.36 nm.

D. The above LDHs film was suspended in a 0.005 mol/L sodium stearate (C ₁₇ H ₃₅ COONa) aqueous solution at 80 ° C for 10 hours, and the film was taken out and rinsed with ethanol at room temperature. Dry to obtain a superhydrophobic LDHs film. The contact angle of the water droplets on the surface of the superhydrophobic LDHs film was 153 ± 3°. Example 3:

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

B. Dissolve 0.5 Co(NO ₃ ) ₂ · 63⁄40 and 6 mol N3⁄4N0 ₃ in a 10L Erlenmeyer flask In the ionic water, the concentration of cobalt ions was 0.05 mol/liter, and the pH of the solution was adjusted to 6.5 with 1% diluted aqueous ammonia.

 C. Suspending the surface anodized aluminum substrate in a solution, sealing the container, and reacting at a constant temperature of 45 ° C for 21 hours. After the reaction is completed, the aluminum substrate is taken out, rinsed with deionized water, and then ethanol. Rinse and dry at room temperature to obtain a LDHs film. The surface roughness of the LDHs film sample was measured to be 592.47 nm.

 D. The above LDHs film was suspended in a 0.025 mol/L potassium laurate (Cui^COOK) aqueous solution at 40 °C for 5 hours, and the film was taken out, rinsed with ethanol, and dried at room temperature. A hydrophobic LDHs film. The contact angle of the water droplets on the superhydrophobic LDHs film surface was measured to be 167 ± 3 °. Example 4:

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

B. In a 10 L Erlenmeyer flask, dissolve 1 mol of Co(N0 ₃ ) ₂ · 63⁄40 and 12 mol of N3⁄4N0 ₃ in deionized water, the concentration of cobalt ion is 0.1 mol/L, and adjust the solution with 1 wt% of dilute ammonia water. The pH is 6.8.

 C. Suspending the surface anodized aluminum substrate in a solution, sealing the container, and reacting at a constant temperature of 90 ° C for 28 hours. After the reaction is completed, the aluminum substrate is taken out, rinsed with deionized water, and then ethanol. Rinse and dry at room temperature to obtain a LDHs film. The surface roughness of the LDHs film sample was measured to be 362.48 nm.

D. Suspend the above LDHs film in 0.0025mol/L potassium stearate (C ₁₇ H ₃₅ COOK) water The self-assembly reaction was carried out at 70 ° C for 2 hours in the solution, the film was taken out, rinsed with ethanol, and dried at room temperature to obtain a superhydrophobic LDHs film. The contact angle of the water droplets on the surface of the superhydrophobic LDHs film was measured to be 154 ± 3 °. Example 5:

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

B. Dissolve 0.8 mol of Co(N0 ₃ ) ₂ ·63⁄40 and 5 mol of N3⁄4N0 ₃ in deionized water in a 10 L Erlenmeyer flask with a cobalt ion concentration of 0.08 mol/L and adjust with 1% dilute ammonia water. The pH of the solution was 5.0.

 C. Suspend the surface anodized aluminum substrate in a solution, seal the container, and react at a constant temperature of 60 °C for 16 hours. After the reaction is completed, remove the aluminum substrate, rinse with deionized water, and use ethanol. Rinse and dry at room temperature to obtain a LDHs film. The surface roughness of the LDHs film sample was measured to be 416.72 nm.

D. The above LDHs film was suspended in 0.02 mol/L sodium oleate (C ₁₅ H ₃₁ COONa) and self-assembled in an aqueous solution at 45 ° C for 8 hours, then rinsed with ethanol and dried at room temperature to obtain superhydrophobic. LDHs film. The contact angle of the water droplets on the surface of the superhydrophobic LDHs film was measured to be 158 ° ±3. . Example 6

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

B. Dissolve 1 mol of Co(N0 ₃ ) ₂ ·63⁄40 and 6 mol of N3⁄4N0 ₃ in deionized water in a 10 L Erlenmeyer flask with a cobalt ion concentration of 0.1 mol/L and adjust the solution with 1% dilute ammonia water. The pH is 8.2.

 C. Suspend the surface anodized aluminum substrate in a solution, seal the container, and react at a constant temperature of 80 °C for 17 hours. After the reaction is completed, remove the aluminum substrate, rinse it with deionized water, and then use ethanol. Rinse and dry at room temperature to obtain a LDHs film. The surface roughness of the LDHs film sample was measured to be 317.43 nm.

D. The above LDHs film was suspended in O.lmol/L potassium oleate (C ₁₅ H ₃₁ COOK) aqueous solution at 60 ° C for 5 hours, then rinsed with ethanol and dried at room temperature. A hydrophobic LDHs film. The contact angle of the water droplets on the surface of the superhydrophobic LDHs film was measured to be 151 ° ± 2 °.

Claims

Claim A superhydrophobic layered bishydroxy composite metal oxide film which is a layered bishydroxy composite metal oxide film grown on an anodized aluminum substrate, the layered bishydroxy composite metal oxide film The chemical formula is: [M ²⁺ Al ³⁺ _x (OH) ₂ r(C0 ₃ ² -) _x/ j3⁄40, Wherein M ²⁺ represents any one of divalent metal ions Mg ²⁺ , Co ²⁺ , Ni ²⁺ , Ca ²⁺ , Cu ²⁺ , Fe ²⁺ and Mn ²⁺ ; 0.2 x 0.4,

The layered bishydroxy composite metal oxide film has a nano/micro composite structure and a surface roughness of 250 nm to 860 nm _; the superhydrophobic layered bishydroxy composite metal oxide film has a contact angle with water droplets of 150 to 170°. . The superhydrophobic layered bishydroxy composite metal oxide thin film according to claim 1, wherein M ²⁺ is Ni ²⁺ , Co ²⁺ or Mg ²⁺ . 3. The superhydrophobic layered bishydroxy composite metal oxide film according to claim 1, wherein Al3 ⁺ is formed in situ from A1 on the aluminum substrate. The superhydrophobic layered bishydroxy composite metal oxide film according to claim 1, wherein the layered bishydroxy composite metal oxide film is treated with a water-soluble long-chain fatty acid salt surfactant solution, The chemical formula of the water-soluble long-chain fatty acid salt is C^H^COCT^, where n = 12 to 22; M÷ represents a monovalent metal ion K+ and/or Na+. The superhydrophobic layered bishydroxy composite metal oxide film according to claim 4, wherein the water-soluble long-chain fatty acid salt is

dsH COONa C ₁₅ H ₃₁ COOK, Ci ₇ H ₃₅ COONa or C ₁₇ H ₃₅ COOK. The superhydrophobic layered bishydroxy composite metal oxide film according to claim 5, wherein the water-soluble long-chain fatty acid salt is

The method for preparing a superhydrophobic layered bishydroxy composite metal oxide film according to claim 1, comprising the following steps:  A. The aluminum sheet with a purity greater than 80% and a thickness of 0.01~1 mm is first ultrasonically cleaned with ethanol for 5 to 10 minutes, then ultrasonically cleaned with water for 5 to 10 minutes to remove surface oil, and then used as an anode on the anodizing device. The plate or stainless steel plate is used as the cathode, the electrolyte is 0.5~3.0 mol/L sulfuric acid solution, the oxidation current is 1~5A, the aluminum piece is anodized for 30~100 min, and then taken out, the electrolyte is rinsed off with deionized water to obtain the anode. Oxidized aluminum substrate for use; B. Dissolving ammonium nitrate and soluble divalent inorganic salt M ²⁺ Y in deionized water at a molar ratio of 3 to 30, controlling the concentration of M ²⁺ metal ions to 0.01 to 0.5 mol/L, and adjusting the pH value with ammonia water to 4.5. ~ 10, get the reaction solution, Divalent soluble inorganic salt in the Y M ²⁺ M ²⁺ is Mg ^2+, Co ^2+, any one of ^{Ni 2+, Ca 2+, Cu 2+} , Fe 2+ , and Mn ²⁺ is, Y is C0 Any of ₃ ² , N0 ₃ , S0 ₄ ² , CI, F—, and Br—; C. The surface anodized aluminum substrate is suspended in the reaction solution, and reacted at 25 to 180 ° C for 0.5 to 96 hours. The aluminum substrate is taken out, rinsed with ethanol, and dried at room temperature to obtain a layered double. a hydroxyl composite metal oxide film;  D. The prepared layered bishydroxy composite metal oxide film is suspended in a 0.001-0.5 mol/L water-soluble long-chain fatty acid salt surfactant solution, and reacted at 25 to 100 ° C for 0.5 to 20 hours. After taking out the film, rinsing with ethanol, and drying at room temperature, a layered bishydroxy composite metal oxide film having superhydrophobic properties is obtained. The water-soluble long-chain fatty acid salt described in the above step D has a chemical formula of C^H^COCT^, wherein n = 12 to 22, and M÷ represents a monovalent metal ion K+ and/or Na+. The method for preparing a superhydrophobic layered bishydroxy composite metal oxide film according to claim 7, wherein in the step B, M ²⁺ is Ni ²⁺ , Co ²⁺ or Mg ²⁺ _; Y is C0 ₃ ² —, N0 ₃ f CI ; The pH of the reaction solution ranges from 5.5 to 8.5. The method for preparing a superhydrophobic layered bishydroxy complex metal oxide film according to claim 1, wherein the reaction condition of the step C is at 50 to 150 ° C for 3 to 60 hours. The method for preparing a superhydrophobic layered bishydroxy composite metal oxide film according to claim 7, wherein the reaction condition of the step D is a reaction at 25 to 80 ° C for 0.5 to 10 hours; The long-chain fatty acid salt is CuH COONa C _n H ₂₃ COOK , C ₁₅ H ₃₁ COONa, C ₁₅ H ₃₁ COOK, C ₁₇ H ₃₅ COONa or C ₁₇ H ₃₅ COOK. The method for preparing a superhydrophobic layered bishydroxy composite metal oxide film according to claim 10, wherein the reaction condition of the step D is a reaction at 30 to 50 ° C for 2 to 5 hours; The chain fatty acid salt is CuH^COONa or C„H ₂₃ COOK.