A super-hydrophobic film and a method for preparing the same

Abstract

The present application relates to the technical field of super-hydrophobic film, in particular to a super-hydrophobic film and a preparation method thereof, wherein the super-hydrophobic film comprises, from top to bottom, a SiOCH film, a grass-like alumina layer and a substrate; the grass-like alumina layer has a nano-scale grass-bush structure; when the thickness of the SiOCH film is 150-250 nm or 250-350 nm, the SiOCH film is deposited on the top of the grass-bush structure of the grass-like alumina layer, and the bottom gap between adjacent grass-bush structures is not filled with the SiOCH film; when the thickness of the SiOCH film is 350-450 nm or 450-550 nm, the SiOCH film is deposited on the top of the grass-bush structure of grass-like alumina layer and gradually fills the bottom gap between adjacent grass-bush structures. The super-hydrophobic film of the present application effectively suppresses light scattering by using the grass-bush structure of the nano-scale grass-like alumina layer, and the SiOCH film fixes the grass-like alumina layer while realizing the regulation of water contact angle by controlling the thickness of the SiOCH film.

Description

Technical Field

[0001] This invention relates to the field of superhydrophobic film technology, and in particular to a superhydrophobic film and its preparation method. Background Technology

[0002] Currently, existing superhydrophobic film fabrication processes mainly include sol-gel method, electrospinning method, etching method, physical vapor deposition method, and chemical vapor deposition method. Among them, the sol-gel method is simple and inexpensive, but the prepared films have poor uniformity, uncontrollable porosity, and weak adhesion to the substrate, making them prone to detachment and cracking, resulting in a short service life. The electrospinning method can prepare porous rough structures, but the process stability is poor, making it difficult to achieve large-scale preparation, and the films have poor mechanical properties. The etching method can accurately construct micro-nano structures, but it suffers from insufficient etching uniformity, easy damage to the substrate, poor process repeatability, and extremely high requirements for equipment and operational precision. The films prepared by the traditional physical vapor deposition method have good density, but it is difficult to construct multi-level micro-nano rough structures adapted to superhydrophobic properties, and the hydrophobic effect is limited.

[0003] Chemical vapor deposition (CVD) has become the mainstream technology for the industrial fabrication of superhydrophobic films due to its advantages such as good film deposition uniformity, high bonding strength, scalability, and strong process controllability. Currently, most CVD-based superhydrophobic film fabrication technologies directly deposit low surface energy coatings on flat substrates, lacking precise construction of the substrate's micro / nano rough structures. This results in insufficient surface roughness of the prepared films, poor superhydrophobic stability, and a tendency to lose hydrophobic properties after long-term use due to coating wear and structural collapse. Some existing technologies treat the substrate with a single roughening process, resulting in a simple, poorly hierarchical rough structure. After deposition, the low surface energy coating easily fills the gaps in the rough structure, destroying the air trapping structure and significantly reducing the superhydrophobic effect, failing to balance film structural stability and hydrophobic properties. Summary of the Invention

[0004] The purpose of this invention is to provide a superhydrophobic film and its preparation method. By controlling the thickness of the SiOCH film through chemical vapor deposition, the size of the water contact angle can be controlled, thereby achieving continuous, precise and repeatable hydrophobicity of the superhydrophobic film.

[0005] To achieve the above objectives, the present invention provides a method for preparing a superhydrophobic membrane, comprising the following steps: S1. After cleaning and drying the substrate, an aluminum oxide film is atomically deposited on the cleaned substrate to obtain a substrate with an aluminum oxide film. S2. Immerse the substrate with the aluminum oxide film obtained in S1 in hot water to obtain a substrate with a grass-like aluminum oxide layer. S3. Chemical vapor deposition is performed on the substrate with the grass-like alumina layer in S2, and hexamethyldisiloxane is introduced to obtain a superhydrophobic film.

[0006] Preferably, in S1, the temperature for atomic layer deposition is 80-200℃.

[0007] Preferably, in S1, the thickness of the alumina film in the substrate having the alumina film is 5-35 nm.

[0008] Preferably, in S2, the temperature of the hot water is 75-95℃, and the soaking time in the hot water is 5-30 minutes.

[0009] Preferably, in S3, the deposition rate of hexamethyldisiloxane is 70-100 nm / min.

[0010] A superhydrophobic membrane was prepared using the method described above.

[0011] Preferably, the superhydrophobic membrane consists of a SiOCH thin film, a grass-like alumina layer, and a substrate, from top to bottom.

[0012] Preferably, the thickness of the SiOCH thin film is one of 150-250nm, 250-350nm, 350-450nm and 450-550nm.

[0013] Preferably, the grass-like alumina layer has a nanoscale grass-like structure. When the SiOCH film thickness is 150-250 nm or 250-350 nm, the SiOCH film is deposited on top of the grass-like structure of the grass-like alumina layer, and the bottom gaps between adjacent grass-like structures are not completely filled by the SiOCH film.

[0014] Preferably, when the SiOCH film thickness is 350-450nm or 450-550nm, the SiOCH film is deposited on top of the grass-like structure of the grass-like alumina layer and gradually fills the gap at the bottom of the adjacent grass-like structure.

[0015] Therefore, the present invention employs the above-mentioned superhydrophobic film and its preparation method, and its beneficial effects are as follows: 1. The superhydrophobic film prepared by this invention utilizes the grass-like structure of the nanoscale grass-like alumina layer, whose size is much smaller than the wavelength of visible light (380-780nm), effectively suppressing light scattering. At the same time, the grass-like structure, as a gradient refractive index layer, actually reduces reflectivity. While the SiOCH film fixes the grass-like alumina layer, the water contact angle can be controlled by controlling the thickness of the SiOCH film. 2. The preparation method provided by the present invention controls the thickness of the SiOCH film through chemical vapor deposition, thereby controlling the size of the water contact angle, realizing continuous, precise and repeatable hydrophobicity, and the obtained superhydrophobic film can withstand the double 85 test (85°C, 85% relative humidity) for up to 2000 hours.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 This is a SEM image of the superhydrophobic membrane in Embodiment 1 of the present invention; Figure 2 This is a SEM image of the superhydrophobic membrane in Embodiment 2 of the present invention; Figure 3 This is a SEM image of the superhydrophobic membrane in Embodiment 3 of the present invention; Figure 4 This is a SEM image of the superhydrophobic membrane in Embodiment 4 of the present invention; Figure 5 These are light transmittance diagrams of the superhydrophobic films in Examples 1-4 of this invention; Figure 6 These are water contact angle diagrams of the superhydrophobic membranes in Examples 1-4 of this invention; Figure 7 This is a stability test diagram of the superhydrophobic membrane in Embodiment 1 of the present invention. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0019] This invention provides a method for preparing a superhydrophobic membrane, comprising the following steps: S1. After cleaning and drying the substrate, an aluminum oxide film is atomically deposited on the cleaned substrate to obtain a substrate with an aluminum oxide film. A dense Al2O3 film is grown layer by layer on the substrate using the self-limiting surface reaction of atomic layer deposition (ALD).

[0020] S2. The substrate with the alumina film obtained in S1 is immersed in hot water to obtain a substrate with a grass-like alumina layer GLA. The hydrothermally dense Al2O3 film undergoes a hydration phase transition in hot water, transforming into boehmite (γ-AlOOH) with a layered or needle-like whisker structure. Due to the preferential growth of alumina along specific crystal planes and the expansion of its volume during the hydrothermal process, sharp, nanoscale sheet-like or grass-like structures are protruded, thereby increasing the hydrophobicity.

[0021] S3. Chemical vapor deposition is performed on the substrate with the grass-like alumina layer in S2, and hexamethyldisiloxane is introduced to obtain a superhydrophobic film. The SiOCH film deposition thickness is controlled by chemical vapor deposition to precisely cover the top or bottom gaps of the GLA. A thin SiOCH film retains high roughness, while a thick SiOCH film fills the gaps.

[0022] In some embodiments of the present invention, in S1, the atomic layer deposition temperature is 80-200°C. This allows for the deposition of Al2O3 with moderate density and an appropriate amount of hydroxyl groups, ensuring structural strength while facilitating the penetration of water molecules into the crystal lattice during subsequent boiling.

[0023] In some embodiments of the present invention, in S1, the thickness of the alumina film in the substrate having the alumina film is 5-35 nm. A GLA with a thickness less than 5 nm is too short and sparse to produce sufficient roughness to amplify the hydrophobic effect, while a GLA with a thickness greater than 35 nm is too tall and dense, and the subsequent 450-550 nm SiOCH film cannot completely level it, and excessive thickness will cause a significant decrease in transmittance due to light scattering.

[0024] In some embodiments of the present invention, in step S2, the temperature of the hot water is 75-95°C, and the immersion time in the hot water is 5-30 minutes. A flat bottom substrate is retained to facilitate light transmission, while a sharp top is used to achieve a high water contact angle. The hot water erodes inward from the surface of the Al2O3 film, completely transforming the surface layer into GLA, while the portion adhering to the substrate remains a dense Al2O3 film.

[0025] In some embodiments of the present invention, in S3, the deposition rate of hexamethyldisiloxane is 70-100 nm / min.

[0026] A superhydrophobic membrane was prepared using the method described above.

[0027] In some embodiments of the present invention, the superhydrophobic film consists of, from top to bottom, a SiOCH thin film, a grass-like alumina layer, and a substrate.

[0028] In some embodiments of the present invention, the thickness of the SiOCH thin film is one of 150-250nm, 250-350nm, 350-450nm, and 450-550nm.

[0029] When the thickness of the SiOCH film is 150-250 nm, the SiOCH film only covers the top of the grass-like structure of GLA, and there is no SiOCH film in the bottom gap between adjacent grass-like structures.

[0030] When the thickness of the SiOCH film is 250-350nm, the SiOCH film covers the top of the grass-like structure of GLA and the top of the grass-like structure becomes thicker. There is part of the SiOCH film in the bottom gap between adjacent grass-like structures, but there are still gaps in the bottom gap between adjacent grass-like structures.

[0031] When the thickness of the SiOCH film is 350-450 nm, the SiOCH film covers the top of the grass-like structure of GLA, and the top of the grass-like structure becomes thicker and rounder, while the gap at the bottom of the adjacent grass-like structure is completely filled by the SiOCH film.

[0032] When the thickness of the SiOCH film is 450-550 nm, the SiOCH film completely covers the grass-like structure of GLA, and the resulting hydrophobic film surface is smooth.

[0033] In some embodiments of the present invention, the grass-like alumina layer has a nanoscale grass-like structure. When the SiOCH film thickness is 150-250 nm or 250-350 nm, the SiOCH film is deposited on top of the grass-like structure of the grass-like alumina layer, and the bottom gaps between adjacent grass-like structures are not completely filled by the SiOCH film.

[0034] In some embodiments of the present invention, when the SiOCH film thickness is 350-450 nm or 450-550 nm, the SiOCH film is deposited on top of the grass-like structure of the grass-like alumina layer and gradually fills the gap at the bottom of the adjacent grass-like structure completely.

[0035] Example 1 The superhydrophobic film consists of a SiOCH thin film, a grass-like alumina layer, and a glass substrate from top to bottom. The SiOCH thin film is 200 nm thick and is deposited on the top of the grass-like alumina layer, without filling the gaps at the bottom of adjacent grass-like layers. Figure 1 As shown.

[0036] S1. After cleaning and drying the substrate, an aluminum oxide thin film is atomically deposited on the cleaned substrate at 120°C to obtain a substrate with an aluminum oxide thin film. The thickness of the aluminum oxide thin film in the substrate with the aluminum oxide thin film is 10 nm.

[0037] S2. Immerse the substrate with the alumina film obtained in S1 in hot water at 85°C for 5 minutes to obtain a substrate with a grass-like alumina layer.

[0038] S3. Chemical vapor deposition is performed on the substrate with the grass-like alumina layer in S2. Hexamethyldisiloxane is introduced, and the deposition rate of hexamethyldisiloxane is 86 nm / min to obtain a superhydrophobic film.

[0039] Example 2 The superhydrophobic film consists of a SiOCH thin film, a grass-like alumina layer, and a glass substrate, arranged from top to bottom. The SiOCH thin film is 300 nm thick and covers the top of the grass-like structure of the GLA, with the top of the grass-like structure becoming thicker. Partial SiOCH film is present in the gaps at the bottom of the grass-like structure of the GLA, but gaps still exist between the bottoms of adjacent grass-like structures. Figure 2 As shown.

[0040] S1. After cleaning and drying the substrate, an aluminum oxide thin film is atomically deposited on the cleaned substrate at 120°C to obtain a substrate with an aluminum oxide thin film. The thickness of the aluminum oxide thin film in the substrate with the aluminum oxide thin film is 10 nm.

[0041] S2. Immerse the substrate with the alumina film obtained in S1 in hot water at 85°C for 5 minutes to obtain a substrate with a grass-like alumina layer.

[0042] S3. Chemical vapor deposition is performed on the substrate with the grass-like alumina layer in S2. Hexamethyldisiloxane is introduced, and the deposition rate of hexamethyldisiloxane is 86 nm / min to obtain a superhydrophobic film.

[0043] Example 3 The superhydrophobic film consists of, from top to bottom, a SiOCH thin film, a grass-like alumina layer, and a glass substrate. The SiOCH thin film is 400 nm thick and covers the top of the grass-like structure of the GLA, with the top of the grass-like structure becoming thicker and rounded. The gaps between the bottoms of adjacent grass-like structures are filled by the SiOCH thin film. Figure 3 As shown.

[0044] S1. After cleaning and drying the substrate, an aluminum oxide thin film is atomically deposited on the cleaned substrate at 120°C to obtain a substrate with an aluminum oxide thin film. The thickness of the aluminum oxide thin film in the substrate with the aluminum oxide thin film is 10 nm.

[0045] S2. Immerse the substrate with the alumina film obtained in S1 in hot water at 85°C for 5 minutes to obtain a substrate with a grass-like alumina layer.

[0046] S3. Chemical vapor deposition is performed on the substrate with the grass-like alumina layer in S2. Hexamethyldisiloxane is introduced, and the deposition rate of hexamethyldisiloxane is 86 nm / min to obtain a superhydrophobic film.

[0047] Example 4 The superhydrophobic film consists of a SiOCH thin film, a grass-like alumina layer, and a glass substrate from top to bottom. The SiOCH thin film is 500 nm thick and covers the grass-like structure of the GLA. The resulting hydrophobic film has a smooth surface. Figure 4 As shown.

[0048] S1. After cleaning and drying the substrate, an aluminum oxide thin film is atomically deposited on the cleaned substrate at 120°C to obtain a substrate with an aluminum oxide thin film. The thickness of the aluminum oxide thin film in the substrate with the aluminum oxide thin film is 10 nm.

[0049] S2. Immerse the substrate with the alumina film obtained in S1 in hot water at 85°C for 5 minutes to obtain a substrate with a grass-like alumina layer.

[0050] S3. Chemical vapor deposition is performed on the substrate with the grass-like alumina layer in S2. Hexamethyldisiloxane is introduced, and the deposition rate of hexamethyldisiloxane is 86 nm / min to obtain a superhydrophobic film.

[0051] Performance testing The transmittance of the superhydrophobic films obtained in Examples 1-4 was tested, and the results are as follows: Figure 5 As shown, the superhydrophobic film structure not only does not lose light, but also plays an anti-reflective (AR) role. This is because the nano-grass structure forms a continuous gradient refractive index layer, effectively suppressing the reflection of visible light from the glass surface.

[0052] The water contact angle of the superhydrophobic films obtained in Examples 1-4 was tested, and the results are as follows: Figure 6 As shown, it can be seen that the water contact angle gradually decreases as the thickness of the SiOCH film increases.

[0053] The long-term environmental stability test of the superhydrophobic film obtained in Example 1 was conducted at an ambient temperature of 85°C and a relative humidity of 85%RH. The results are as follows: Figure 7 As shown, after 1000 hours, the water contact angle (WCA) decreased from 142.3° to 141.0°.

[0054] Therefore, the present invention adopts the above-mentioned superhydrophobic film and its preparation method, utilizing the grass-like structure of the nanoscale grass-like alumina layer, whose size is much smaller than the wavelength of visible light (380-780nm), effectively suppressing light scattering. At the same time, the grass-like structure, as a gradient refractive index layer, actually reduces reflectivity. While the SiOCH film fixes the grass-like alumina layer, the water contact angle is regulated by controlling the thickness of the SiOCH film.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a superhydrophobic film, characterized in that: Includes the following steps: S1. After cleaning and drying the substrate, an aluminum oxide film is atomically deposited on the cleaned substrate to obtain a substrate with an aluminum oxide film. S2. Immerse the substrate with the aluminum oxide film obtained in S1 in hot water to obtain a substrate with a grass-like aluminum oxide layer. S3. Chemical vapor deposition is performed on the substrate with the grass-like alumina layer in S2, and hexamethyldisiloxane is introduced to obtain a superhydrophobic film.

2. The method for preparing a superhydrophobic film according to claim 1, characterized in that: In S1, the temperature for atomic layer deposition is 80-200℃.

3. The method for preparing a superhydrophobic film according to claim 1, characterized in that: In S1, the thickness of the alumina film in the substrate with the alumina film is 5-35 nm.

4. The method for preparing a superhydrophobic membrane according to claim 1, characterized in that: In S2, the temperature of the hot water is 75-95℃, and the soaking time in the hot water is 5-30 minutes.

5. The method for preparing a superhydrophobic film according to claim 1, characterized in that: In S3, the deposition rate of hexamethyldisiloxane is 70-100 nm / min.

6. A superhydrophobic membrane, characterized in that: It is prepared using the method described in any one of claims 1-5.

7. A superhydrophobic membrane according to claim 6, characterized in that: The superhydrophobic film consists of a SiOCH thin film, a grass-like alumina layer, and a substrate, from top to bottom.

8. The superhydrophobic membrane according to claim 7, characterized in that: The thickness range of SiOCH thin films is one of 150-250nm, 250-350nm, 350-450nm and 450-550nm.

9. A superhydrophobic membrane according to claim 8, characterized in that: The grass-like alumina layer has a nanoscale grass-like structure. When the SiOCH film thickness is 150-250nm or 250-350nm, the SiOCH film is deposited on top of the grass-like structure of the grass-like alumina layer, and the bottom gaps between adjacent grass-like structures are not completely filled by the SiOCH film.

10. A superhydrophobic membrane according to claim 8, characterized in that: When the SiOCH film thickness is 350-450nm or 450-550nm, the SiOCH film is deposited on top of the grass-like structure of the grass-like alumina layer and gradually fills the gap at the bottom of the adjacent grass-like structure.

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