Full-substrate compatible iron oxide-based super-amphiphobic coating as well as preparation method and application thereof

Abstract

The invention discloses a full-substrate compatible iron oxide-based super-amphiphobic coating as well as a preparation method and application thereof, and the preparation method of the coating comprises the following steps: adding ammonia water into a ferric nitrate solution to react to obtain a precursor solution, adding a fluorine-containing surface treating agent into the precursor solution, uniformly dispersing, and reacting to obtain the super-amphiphobic coating. The coating is coated on the surface of a substrate, and a super-amphiphobic coating is formed on the surface of the substrate after curing; the coating can be coated on the surface of any one of a cotton fabric, rubber, plastic, glass, metal and ceramic. According to the invention, integrated construction of a coating structure and functions can be realized only through one step, construction of a stable micro-nano coarse structure and endowing of extremely low surface energy are synchronously completed, and the integrated structure ensures dense and stable arrangement of fluorine-containing functional groups; therefore, the excellent super-amphiphobic performance that the water contact angle and the edible oil contact angle are both larger than 150 degrees is achieved.

Description

Technical Field

[0001] This invention belongs to the field of superhydrophobic and oleophobic materials technology, specifically relating to a fully substrate compatible iron oxide-based superhydrophobic and oleophobic coating, its preparation method, and its application. Background Technology

[0002] Superhydrophobic (water contact angle > 150°) and superoleophobic (oil contact angle > 140°) surfaces (collectively referred to as "superhydrophobic and superoleophobic" surfaces) have broad application prospects in fields such as anti-icing, anti-fouling, self-cleaning, and corrosion resistance. Constructing such surfaces typically requires two elements: suitable micro-nano rough structures and extremely low surface energy.

[0003] Existing technologies for preparing superhydrophobic coatings based on metal oxides typically employ a two-step method: first, oxide nanoparticles (such as α-Fe₂O₃) are synthesized through high-temperature calcination (usually >500℃) or commercially available oxide nanoparticles are used directly; subsequently, low-surface-energy modification is performed through post-processing. This method has significant limitations: 1) High energy consumption and complex process: The high-temperature calcination step consumes a lot of energy, and the subsequent modification process makes it difficult to ensure the uniformity and binding strength of the modifier. 2) Performance limitations: Many hydrocarbon chain-based modifiers are unable to achieve the extremely low surface energy required for superoleophobicity, which limits the dual-repellent properties of the coating. 3) Poor universality: The obtained powder material faces challenges in terms of dispersibility and adhesion to various substrates, and it is difficult to achieve large-area, uniform preparation of the entire substrate through simple coating processes (such as spraying).

[0004] Therefore, developing a technology that enables simultaneous low-temperature, one-step synthesis and surface functionalization of oxides, and directly produces a sprayable, all-substrate compatible superhydrophobic coating solution, has become the key to overcoming existing bottlenecks. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of the invention, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a fully substrate-compatible iron oxide-based superhydrophobic coating.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: including, Ammonia water is added to ferric nitrate solution to react and obtain a precursor solution. A fluorine-containing surface treatment agent is added to the precursor solution, dispersed evenly, and then reacted to obtain a superhydrophobic coating. The mass ratio of ferric nitrate to ammonia is 1:2 to 2.5.

[0009] As a preferred embodiment of the preparation method described in this invention, the fluorinated surface treatment agent includes one of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and 1H,1H,2H,2H-perfluorodecylthiol.

[0010] In a preferred embodiment of the preparation method described in this invention, the amount of the fluorine-containing surface treatment agent added is 5-20 wt% compared to that of ferric nitrate.

[0011] In a preferred embodiment of the preparation method described in this invention, the fluorine-containing surface treatment agent is added to the precursor solution and dispersed evenly before reaction, wherein the reaction temperature is 50~80℃ and the reaction time is 6~12h.

[0012] In a preferred embodiment of the preparation method described in this invention, the dispersion time is 20-25 min.

[0013] In a preferred embodiment of the preparation method described in this invention, the precursor solution is obtained by adding ammonia water to the ferric nitrate solution and reacting, wherein the concentration of ferric nitrate is 20~80g / L.

[0014] In a preferred embodiment of the preparation method described in this invention, the reaction temperature is 20~28℃ and the reaction time is 30~50min.

[0015] Another objective of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a fully substrate-compatible iron oxide-based superhydrophobic coating.

[0016] Another objective of this invention is to overcome the shortcomings of the prior art and provide an application of a substrate-compatible iron oxide-based superhydrophobic coating in the preparation of a substrate-compatible iron oxide-based superhydrophobic coating.

[0017] To solve the above-mentioned technical problems, the present invention provides the following technical solution: including, A superhydrophobic coating based on iron oxide that is compatible with all substrates is applied to the substrate surface and cured to form a superhydrophobic coating on the substrate surface. The coating method includes one of spraying, brushing, and dipping.

[0018] As a preferred embodiment of the application described in this invention, the coating is applied to the surface of a substrate, wherein the substrate comprises one or more of cotton fabric, rubber, plastic, glass, metal, and ceramic.

[0019] Beneficial effects of this invention: (1) Compared with the traditional two-step preparation process, the present invention can achieve the integrated construction of coating structure and function in only one step. The fluorine-containing modifier is covalently grafted in situ onto the surface of the self-generated iron oxide nanocrystals, simultaneously completing the construction of a stable micro-nano rough structure and the imparting of extremely low surface energy. This integrated structure ensures the dense and stable arrangement of fluorine-containing functional groups, thereby achieving excellent superhydrophobic properties with both water contact angle and edible oil contact angle greater than 150°.

[0020] (2) Meanwhile, compared with the traditional method where the nanoparticles and modifiers are mainly physically bonded, the bonding is weak and the stability is poor, and the adhesive is easy to cover or submerge the micro-nano structure during the film formation process, which damages the surface roughness, and its own high surface energy significantly weakens the overall hydrophobic performance of the coating, resulting in a serious lack of oleophobic effect (the contact angle is usually much lower than 150°), the nanoparticles generated in situ in this invention can form a bond with a variety of substrates through physical anchoring and interfacial chemical action, and can meet the adhesion stability requirements of most application scenarios without relying on additional adhesives.

[0021] (3) This invention overcomes the contradiction that traditional coatings generally face in that it is difficult to balance "adhesion" and "superhydrophobicity". Especially on low surface energy substrates such as rubber and plastic, the adhesive introduced to achieve adhesion will further deteriorate its superhydrophobic and superhydrophobic properties, greatly breaking the limitations of traditional methods. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The X-ray diffraction pattern of the coating in Example 1 of this invention is shown.

[0024] Figure 2 The infrared spectrum of the coating in Example 1 of this invention is shown.

[0025] Figure 3 This is a contact angle diagram of the coating prepared by spraying method in Example 2 of the present invention with water (W) and edible oil (O).

[0026] Figure 4This is a contact angle diagram of the coating prepared by spraying method in Example 4 of the present invention with water (W) and edible oil (O).

[0027] Figure 5 This is a comparison diagram of the contact angles of the coatings prepared on the surfaces of flexible and rigid substrates in Embodiment 5 of the present invention with water (W) and edible oil (O).

[0028] Figure 6 This is a SEM image of the coating obtained in Example 5 of the present invention.

[0029] Figure 7 This is a comparison diagram of the salt deposition behavior on the surface of a glass slide coated with a superhydrophobic coating and the surface of a bare glass slide without coating in Embodiment 7 of the present invention. Detailed Implementation

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0031] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0032] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0033] The ammonia water used in this invention has a mass fraction of 25-28%.

[0034] Example 1 This invention provides a method for preparing a fully substrate-compatible iron oxide-based superhydrophobic coating, specifically: 1 g of ferric nitrate (Fe(NO)3•9H2O) was dissolved in 50 mL of anhydrous ethanol to obtain a ferric nitrate solution with a concentration of 20 g / L. Ammonia was added to adjust the pH of the solution to 9.4, and the reaction was carried out at 25 °C for 30 min to obtain a ferric hydroxide precursor solution. The mass ratio of ammonia to ferric nitrate was 1:2.3. 0.15 g of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FDTS) was added to the precursor solution and ultrasonically dispersed for 20 min. The solution was then reacted at 60 °C for 8 h to obtain α-Fe2O3-based superhydrophobic coating.

[0035] The X-ray diffraction pattern of the coating in Example 1 was tested, and the results are as follows: Figure 1 As shown.

[0036] from Figure 1 The diffraction peaks of the coating are sharp and have high intensity, indicating good crystallinity. The diffraction peaks of both α-Fe₂O₃ and FeOOH crystals are present in the spectrum. During the reaction, Fe… 3+ First with 3OH - Amorphous Fe(OH)3 precipitate is formed. In a low-temperature alkaline environment at 60℃, the precursor transforms into FeOOH crystals through a dissolution-reprecipitation mechanism. Simultaneously, in the reaction microenvironment composed of ethanol solvent and modifier, some of the amorphous precursor directly dehydrates and crystallizes to form α-Fe2O3 via a non-classical crystallization pathway. Therefore, FeOOH and α-Fe2O3 coexist in the product, which is a characteristic phenomenon of this one-step low-temperature preparation method, demonstrating the feasibility of simultaneously achieving precursor transformation and surface functionalization under mild conditions.

[0037] The infrared spectrum of the coating in Example 1 was tested, and the results are as follows: Figure 2 As shown.

[0038] Figure 2 Middle, 479cm -1 The broad, weak peak at 670 cm⁻¹ belongs to the bending vibration or lattice vibration of the Fe-O bond; -1 and 705cm -1 The double peak at 1048 cm⁻¹ originates from the stretching vibration of the Fe-O bond, corresponding to the lattice vibration modes of α-Fe₂O₃ or FeOOH. -1 The absorption peak at 1151 cm⁻¹ is attributed to the stretching vibration of the Si-OC bond, originating from the incompletely hydrolyzed methoxy groups in the modifier FDTS; while the absorption peak at 1151 cm⁻¹ is attributed to the stretching vibration of the Si-OC bond. -1 With 823cm -1 The absorption peaks at 1206 cm⁻¹ are attributed to the asymmetric and symmetric stretching vibrations of the Si-O-Si bonds, respectively, indicating that hydrolytic condensation has occurred between FDTS molecules, forming a cross-linked structure. -1 and 1390cm -1 The absorption peaks at these locations are attributed to the asymmetric and symmetric stretching vibrations of the CF bond, respectively. These characteristic peaks collectively demonstrate that the fluorosilane modifier FDTS has been successfully introduced into the coating system.

[0039] in addition, Figure 2 3000-3600cm -1 The broad absorption range is attributed to the structural hydroxyl groups in FeOOH and the OH stretching vibrations that may adsorb water. At 970 cm⁻¹ -1A weak, broad peak was observed nearby, possibly corresponding to the vibration of the Si-O-Fe bond, indicating that a covalent bond was formed between FDTS and α-Fe₂O₃, enhancing the binding stability between the modifier and the nanoparticles. Furthermore, at 1761 cm⁻¹... -1 and 2397cm -1 The sharp peaks observed nearby can be attributed to the stretching vibrations of C=O and carboxylic acid OH, respectively, and are presumed to originate from trace oxidation byproducts of the solvent during the reaction. These impurities do not affect the main structure and superhydrophobic properties of the coating.

[0040] Example 2 In this embodiment, the coating obtained in Example 1 is applied to the surface of a rubber substrate to prepare an iron oxide-based superhydrophobic coating. Specifically: The α-Fe2O3-based superhydrophobic coating prepared in Example 1 was sprayed onto the surface of a rubber substrate using a spray gun at a pressure of 0.3 MPa and a spraying distance of 25 cm. The spraying was repeated 12 times and dried at 60°C for 1 hour to form the α-Fe2O3@FDTS superhydrophobic coating.

[0041] Example 3 This embodiment provides a method for preparing a fully substrate-compatible iron oxide-based superhydrophobic coating, specifically as follows: 2g of ferric nitrate (Fe(NO)3•9H2O) was dissolved in 50mL of anhydrous ethanol to obtain a ferric nitrate solution with a concentration of 40g / L. Ammonia was added to adjust the pH of the solution to 9.7. The reaction was carried out at 25℃ for 30min to obtain a ferric hydroxide precursor solution. The mass ratio of ammonia to ferric nitrate was 1:2.3. 0.2 g of 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) was added to the precursor solution and ultrasonically treated for 20 min. The solution was then reacted at 60 °C for 8 h to obtain α-Fe2O3-based superhydrophobic coating.

[0042] Example 4 In this embodiment, the coating obtained in Example 3 is applied to the surface of a rubber substrate to prepare an iron oxide-based superhydrophobic coating. Specifically: The α-Fe2O3-based superhydrophobic coating prepared in Example 3 was sprayed onto the surface of a rubber substrate using a spray gun at a pressure of 0.3 MPa and a spraying distance of 25 cm. The spraying was repeated 12 times and dried at 60°C for 1 hour to form the α-Fe2O3@PFDTES superhydrophobic coating.

[0043] The contact angles of the coatings prepared by the spraying method in Examples 2 and 4 to water (W) and edible oil (O) were tested, and the results are as follows: Figures 3-4 As shown.

[0044] Figure 3The contact angle of the coating prepared by spraying in Example 2 with water (W) and edible oil (O) is shown. Figure 4 The image shows the contact angles of the coatings prepared by spraying in Example 4 with water (W) and edible oil (O). It can be clearly seen that the contact angles of both coatings prepared with water and oil are greater than 150°, indicating that both exhibit excellent superhydrophobic properties.

[0045] Example 5 In this embodiment, the coating obtained in Example 3 is used to prepare iron oxide-based superhydrophobic coatings by dip-coating onto the surfaces of rubber, cotton fabric, paper, sponge, glass, aluminum plate, ceramic, and plastic plate, respectively. Specifically: Rubber, cotton fabric, glass, and aluminum sheet were respectively immersed in the coating prepared in Example 3, pulled up and drained, and then dried at 120°C. The coating and curing were repeated 5 times to form α-Fe2O3@PFDTES superhydrophobic coatings on different flexible and rigid substrates.

[0046] In Example 5, the contact angles of water (W) and edible oil (O) on different substrate surfaces after forming α-Fe2O3@PFDTES superhydrophobic coatings were measured. The results are as follows: Figure 5 As shown.

[0047] from Figure 5 As can be seen from (a) to (d), the contact angle of the coating with water on both flexible and rigid substrate surfaces reached 154 to 157°, and the contact angle with oil was also greater than 150°. This indicates that the present invention can form a coating with excellent superhydrophobic properties on all substrate surfaces.

[0048] Further observation of the microstructure of the α-Fe2O3@PFDTES superhydrophobic coating in Example 5, such as... Figure 6 As shown, α-Fe2O3 consists of spherical particles with a size of 20~40nm, which stack up to form a rough structure ranging from hundreds of nanometers to micrometers. This structure provides the necessary micro-nano roughness basis for the superhydrophobic properties.

[0049] Example 6 This embodiment provides a method for preparing a fully substrate-compatible iron oxide-based superhydrophobic coating, specifically as follows: 4g of ferric nitrate (Fe(NO)3•9H2O) was dissolved in 50mL of anhydrous ethanol to obtain a ferric nitrate solution with a concentration of 80g / L. Ammonia was added to adjust the pH of the solution to 9.9. The solution was reacted at 25℃ for 30min to obtain a ferric hydroxide precursor solution. The mass ratio of ammonia to ferric nitrate was 1:2.3. 0.2 g of 1H,1H,2H,2H-perfluorodecyl mercaptan was added to the precursor solution, and after ultrasonic treatment for 20 min, it was reacted at 60 °C for 8 h to obtain α-Fe2O3-based superhydrophobic coating.

[0050] Example 7 In this embodiment, the coating obtained in Example 6 is applied to the surface of a glass slide substrate to prepare an iron oxide-based superhydrophobic coating. Specifically: The coating prepared in Example 6 was brushed onto the surface of a glass slide substrate and then heated at 120°C for 5 minutes. The coating and curing were repeated 3 times to form an α-Fe2O3@1H,1H,2H,2H-perfluorodecylthiol superhydrophobic coating on the surface of the glass slide.

[0051] Simultaneously, the salt deposition behavior of sodium chloride solution on the surface of a glass slide coated with a superhydrophobic coating in Example 7 and on the surface of an uncoated bare glass slide was tested, and the results are as follows: Figure 7 As shown.

[0052] contrast Figure 7 It is evident that the salt solution spreads on the uncoated substrate surface and forms tightly bound circular salt spots after drying; while on the coated surface, the droplets are in a contracted state, and the salt crystallization area is distributed in a ring after drying. There are obvious gaps between the salt particles and the substrate, and the contact area is small, indicating that the coating has a significant salt deposition inhibition effect and salt spray corrosion prevention potential.

[0053] Comparative Example 1 The difference between this comparative example and Example 1 is that the mass ratio of ferric nitrate to ammonia was adjusted to 2:1, and the pH was 7. The rest of the preparation methods were the same as in Example 1, and the coating of this comparative example was obtained.

[0054] Comparative Example 2 The difference between this comparative example and Example 1 is that the mass ratio of ferric nitrate to ammonia was adjusted to 1.5:1, and the pH was 8.5. The rest of the preparation methods were the same as in Example 1, and the coating of this comparative example was obtained.

[0055] Comparative Example 3 The difference between this comparative example and Example 1 is that the mass ratio of ferric nitrate to ammonia was adjusted to 1:9, and the pH was 10.5. The rest of the preparation method was the same as in Example 1, and the coating of this comparative example was obtained.

[0056] Comparative Example 4 This comparative example uses the coatings obtained from Comparative Examples 1-3 to spray onto the surface of a rubber substrate to prepare an iron oxide-based coating, specifically: The α-Fe2O3-based coatings prepared in Comparative Examples 1-3 were sprayed onto the surface of a rubber substrate using a spray gun at a pressure of 0.3 MPa and a spraying distance of 25 cm. The spraying was repeated 12 times and dried at 60°C for 1 hour to form the α-Fe2O3-based coating.

[0057] The contact angles of the superhydrophobic coatings formed by different coatings in Comparative Example 4 with water (W) and edible oil (O) were tested, and the results are shown in Table 1.

[0058] Table 1. Effect of ammonia dosage on the dihydrophobic properties of the coating.

[0059] As can be seen from Table 1, the reaction system of Comparative Example 1 is close to neutral, and OH... - The concentration is too low to allow Fe to... 3+ Sufficient hydrolysis and precipitation of iron hydroxide precursors make it difficult for subsequent products such as iron oxide to form a continuous, dense, and multi-layered composite microstructure. Due to the imperfect micro-nano rough structure and insufficient roughness, the coating exhibits a low contact angle (water contact angle ≈ 140°, oil contact angle ≈ 103°).

[0060] In the preparation process of Comparative Example 2, the mass ratio of ferric nitrate to ammonia was still too high, and the OH- concentration was too low, failing to meet the conditions for forming the most ideal precursor morphology and dispersion. The aggregation degree and morphology of the precursor particles were not as uniform as under the optimal pH, resulting in deficiencies in the uniformity or layer richness of the micro-nano structures formed by subsequent conversion. The final water contact angle was 153°, and the edible oil contact angle was 142°, both lower than those in Example 1.

[0061] In Comparative Example 3, the excessive ammonia content and high OH- concentration caused excessive aggregation of precursors, resulting in coarse particles and uneven coating surface and poor particle adhesion. Furthermore, the alkaline environment promotes the condensation reaction between fluoride molecules, altering their molecular conformation and arrangement. High concentrations of OH- can even attack CF bonds, leading to irreversible hydrolysis and weakening the hydrophobicity (water contact angle 146°, edible oil contact angle 124°).

[0062] Comparative Example 5 The difference between this comparative example and Example 1 is that only 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FDTS) was changed to perfluorooctyltrichlorosilane. The rest of the preparation method is the same as in Example 1, and the coating of this comparative example is obtained.

[0063] Comparative Example 6 The difference between this comparative example and Example 1 is that the amount of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FDTS) was adjusted to 0.03g, that is, the amount of FDTS added compared to ferric nitrate was 3wt%. The rest of the preparation method was the same as in Example 1, and the coating of this comparative example was obtained.

[0064] Comparative Example 7 The difference between this comparative example and Example 1 is that the amount of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FDTS) was adjusted to 0.35g, that is, the amount of FDTS added compared to ferric nitrate was 35wt%. The rest of the preparation method was the same as in Example 1, and the coating of this comparative example was obtained.

[0065] Comparative Example 8 This comparative example uses the coatings obtained from Comparative Examples 5-7 to spray onto the surface of a rubber substrate to prepare an iron oxide-based coating, specifically: The α-Fe2O3-based coatings prepared in Comparative Examples 5-7 were sprayed onto the surface of a rubber substrate using a spray gun. The spray gun pressure was 0.3 MPa, the spraying distance was 25 cm, and the spraying was repeated 12 times. The coating was then dried at 60°C for 1 hour to form the α-Fe2O3-based coating.

[0066] The contact angles of the super-amphihydrophobic coatings formed by different coatings in Comparative Example 8 with water (W) and edible oil (O) were tested, and the results are shown in Table 2.

[0067] Table 2. Effect of Fluorine-Containing Surface Treatment Agents on the Amphoteric Properties of Coatings

[0068] As can be seen from Comparative Example 5 in Table 2, perfluorooctyltrichlorosilane with a shorter carbon chain does not reduce surface energy sufficiently, thus failing to achieve superoleophobicity. Furthermore, the hydrolysis byproducts of the chlorine group affect the stability of the coating, resulting in a decrease in its adhesion.

[0069] Comparative Examples 6 and 7 show that when the concentration of the fluorinated surface treatment agent is below 5 wt%, the surface modification is insufficient, the fluorinated functional groups are not fully covered, the surface energy of the coating is high, and the contact angle is low. However, when the concentration of the fluorinated surface treatment agent is above 20 wt%, the fluoride molecules self-aggregate and fill the micro-nano grooves, resulting in a decrease in roughness, loss of the structural basis of the supporting air cushion, and a reduction in the contact angle.

[0070] Comparative Example 9 The difference between this comparative example and Example 1 is that the reaction temperature was adjusted from 60°C to 40°C, while the rest of the preparation method was the same as in Example 1, resulting in the coating of this comparative example.

[0071] Comparative Example 10 The difference between this comparative example and Example 1 is that the reaction temperature was adjusted from 60°C to 90°C, while the rest of the preparation method was the same as in Example 1, resulting in the coating of this comparative example.

[0072] Comparative Example 11 This comparative example uses the coatings obtained in Comparative Examples 9-10 to spray onto the surface of a rubber substrate to prepare an iron oxide-based coating, specifically: The α-Fe2O3-based coating prepared in Comparative Examples 9-10 was sprayed onto the surface of a rubber substrate using a spray gun at a pressure of 0.3 MPa and a spraying distance of 25 cm. The spraying was repeated 12 times and then dried at 60°C for 1 hour to form the α-Fe2O3-based coating.

[0073] The contact angles of the super-amphihydrophobic coatings formed by different coatings in Comparative Example 11 with water (W) and edible oil (O) were tested, and the results are shown in Table 3.

[0074] Table 3 Effect of reaction temperature on the dihydrophobic properties of the coating

[0075] As shown in Table 3, within the raw material ratio range of this invention, improper selection of the reaction temperature will also prevent the preparation of the superhydrophobic coating. When the reaction temperature is below 50℃ (Comparative Example 9), the reaction rate is slow, the conversion of the ferric hydroxide precursor is incomplete, and the crystallinity of α-Fe2O3 nanocrystals is low, resulting in an underdeveloped micro / nano structure and a low contact angle in the coating. When the reaction temperature is above 80℃ (Comparative Example 10), ethanol and water evaporate rapidly, disrupting the equilibrium of the reaction system, causing a rapid increase in system viscosity, excessive particle aggregation and morphological instability, and introducing safety risks. Due to the excessive viscosity of the coating, it is difficult to spray, and the coating cannot be obtained.

[0076] Comparative Example 12 The difference between this comparative example and Example 1 is that the concentration of ferric nitrate was adjusted to 10 g / L, while the rest of the preparation method was the same as in Example 1, resulting in the coating of this comparative example.

[0077] Comparative Example 13 The difference between this comparative example and Example 1 is that the concentration of ferric nitrate was adjusted to 90 g / L, while the rest of the preparation method was the same as in Example 1, resulting in the coating of this comparative example.

[0078] Comparative Example 14 This comparative example uses the coatings obtained in Comparative Examples 12-13 to spray onto the surface of a rubber substrate to prepare an iron oxide-based coating, specifically: The α-Fe2O3-based coating prepared in Comparative Examples 12-13 was sprayed onto the surface of a rubber substrate using a spray gun. The spray gun pressure was 0.3 MPa, the spraying distance was 25 cm, and the spraying was repeated 12 times. The coating was then dried at 60°C for 1 hour to form the α-Fe2O3-based coating.

[0079] The contact angles of the super-amphihydrophobic coatings formed by different coatings in Comparative Example 14 with water (W) and edible oil (O) were tested, and the results are shown in Table 4.

[0080] Table 4 Effect of ferric nitrate concentration on the dihydrophobic properties of the coating

[0081] Table 4 shows that when the ferric nitrate concentration is as low as 10 g / L, the amount of α-Fe₂O₃ nanoparticles generated is small, the coating is too thin, and the micro / nano structure is discontinuous, resulting in a low contact angle and making it impossible to obtain a superhydrophobic coating. Conversely, when the ferric nitrate concentration is higher than 80 g / L, the precursor suspension has high viscosity, leading to uneven coating, a thick coating that is prone to cracking, poor adhesion, and cracking on the glass substrate, resulting in a low contact angle and also preventing the preparation of a superhydrophobic coating.

[0082] In summary, this invention provides a substrate-compatible iron oxide-based superhydrophobic coating, its preparation method, and its applications. This preparation method abandons traditional coating methods that rely on external binders, instead pursuing a structure-function integration of the coating itself. It integrates the preparation of iron oxide nanocrystals and surface functionalization in a single step through a one-step in-situ synthesis strategy: simultaneously with the generation of iron oxide nanoparticles, a fluorine-containing modifier is directly grafted via covalent bonds, forming a stable "inorganic core-organic shell" structure. This in-situ functionalization design utilizes perfluorodecyltrimethoxysilane to participate in the reaction during the synthesis of iron oxide nanocrystals, directly grafting it onto the surface of α-Fe₂O₃ nanoparticles via covalent bonding (such as forming Si-O-Fe bonds). This ensures the dense, stable, and uniform arrangement of the fluorine-containing long chains, thereby more effectively reducing the surface energy of the coating and imparting excellent micro / nano roughness. Furthermore, the in-situ generated nanoparticles can form effective physical anchoring and chemical interactions with the substrate. This invention achieves true "superhydrophobic and superoleophobic" properties by using in-situ covalent bonding, which makes the contact angle of the coating with water and edible oil both greater than 150°.

[0083] This invention overcomes the problems of uneven bonding between nanoparticles and fluorine-containing reagents in traditional two-step methods, and the need for additional adhesives to enhance coating adhesion, which limits coating stability and durability. Traditional methods require selecting adhesives for different substrates to enhance adhesion, but the coating solution obtained by this invention requires no additional adhesive and can be directly applied to various substrates such as cotton fabrics, rubber, glass, and metals through spraying, brushing, etc., exhibiting excellent versatility and adhesion. This solves the bottleneck of difficult coating of traditional powder materials.

[0084] Meanwhile, this invention simultaneously completes the crystallization and surface modification of iron oxide nanocrystals at a low temperature of 60℃, eliminating the need for high-temperature calcination and post-treatment steps, thus significantly reducing energy consumption and process complexity.

[0085] Furthermore, the coating of this invention exhibits significant effects in areas such as anti-icing and anti-salt spray corrosion, indicating that this invention not only possesses basic hydrophobic and oleophobic properties but also has multifunctionality.

[0086] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. 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 be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a fully substrate-compatible iron oxide-based superhydrophobic coating, characterized in that: include, Ammonia water is added to ferric nitrate solution to react and obtain a precursor solution. A fluorine-containing surface treatment agent is added to the precursor solution, dispersed evenly, and then reacted to obtain a superhydrophobic coating. The mass ratio of ferric nitrate to ammonia is 1:2 to 2.

5.

2. The preparation method according to claim 1, characterized in that: The fluorinated surface treatment agent includes one of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and 1H,1H,2H,2H-perfluorodecylthiol.

3. The preparation method according to claim 2, characterized in that: The amount of the fluorine-containing surface treatment agent added is 5~20wt% compared to that of ferric nitrate.

4. The preparation method according to claim 1, characterized in that: The process involves adding a fluorinated surface treatment agent to the precursor solution, dispersing it evenly, and then reacting it. The reaction temperature is 50-80℃, and the reaction time is 6-12 hours.

5. The preparation method according to claim 4, characterized in that: The dispersion time is 20-25 minutes.

6. The preparation method according to claim 1, characterized in that: The precursor solution is obtained by adding ammonia to ferric nitrate solution and reacting the solution, wherein the concentration of ferric nitrate is 20~80g / L.

7. The preparation method according to claim 6, characterized in that: The reaction temperature is 20~28℃, and the reaction time is 30~50min.

8. The coating prepared by any one of the preparation methods described in claims 1 to 7.

9. The application of the coating as described in claim 8 in the preparation of a fully substrate-compatible iron oxide-based superhydrophobic coating, characterized in that: include, The coating described in claim 8 is applied to the surface of a substrate and cured to form a superhydrophobic coating on the surface of the substrate. The coating method includes one of spraying, brushing, and dipping.

10. The application as described in claim 9, characterized in that: The coating is applied to the surface of a substrate, wherein the substrate includes one or more of cotton fabric, rubber, plastic, glass, metal, and ceramic.

Images