A method for producing a hydrophobic coating using a rare earth salt solution thermal spray

Abstract

The application discloses a method for preparing a hydrophobic coating by using a rare earth salt liquid material thermal spraying, and belongs to the technical field of coating preparation. The method comprises the following steps: (1) pre-treating a substrate surface, wherein the pre-treatment comprises cleaning and roughening, and a to-be-sprayed sample is obtained; (2) adding a rare earth salt into a solvent to prepare a rare earth salt liquid material; and (3) spraying the rare earth salt liquid material on the to-be-sprayed sample by using a thermal spraying technology, so that a rare earth oxide is generated on the surface of the to-be-sprayed sample, and a hydrophobic coating is prepared. The rare earth salt is a lanthanide rare earth salt. In step (1), a step of preparing a coating on the substrate surface after the pre-treatment by using the thermal spraying technology can be further included. The method is simple and efficient, is suitable for various substrate materials, can be prepared in a large area, and the prepared hydrophobic coating is well combined with the substrate and has excellent hydrophobic / super-hydrophobic performance.

Description

Technical Field

[0001] This invention relates to the field of coating preparation technology, and specifically to a method for preparing a hydrophobic coating using rare earth salt solution thermal spraying. Background Technology

[0002] Hydrophobicity refers to a surface contact angle with water greater than 90°, while superhydrophobicity refers to a surface contact angle with water greater than 150° and a roll-off angle less than 10°. Due to their unique wetting properties, hydrophobic / superhydrophobic coatings exhibit low surface free energy and good anti-adhesion properties, making them promising for applications in self-cleaning materials, microfluidic devices, and fluid drag reduction.

[0003] The wettability of a solid surface depends primarily on its surface morphology and chemical properties. Generally, coatings with rough structures and low surface energy tend to be hydrophobic / superhydrophobic. Although various surface treatment techniques exist to achieve hydrophobic / superhydrophobic modification, the processes involved are complex, making large-scale preparation difficult and hindering mass production.

[0004] Thermal spraying technology is an additive manufacturing method that uses a heat source to heat the coating material to a molten or semi-molten state and then sprays it onto a pre-treated substrate surface at a certain speed to form a coating. Thermal spraying technologies mainly include arc spraying, flame spraying, and plasma spraying. Thermal spraying technology can generally be applied on-site, is highly adaptable, offers flexible processes, is simple to operate, and is not limited by workpiece size or site conditions.

[0005] For example, Chinese patent document CN105478322A discloses a method for preparing hydrophobic coatings using liquid thermal spraying. This invention uses a suspension containing soluble polytetrafluoroethylene particles as the liquid material for flame spraying, and the resulting coating has a hydrophobic angle of over 140°. Another example is Chinese patent document CN104480423A, which discloses a method for preparing superhydrophobic coatings using supersonic arc spraying. This method uses supersonic arc spraying technology to prepare a coating on the substrate surface, and then sprays a low surface energy material onto the coating surface. The low surface energy material is one or more of fluororesin, fluorocarbon resin, fluorosilane, and polyurethane. The modified coating obtained by this invention has a hydrophobic angle of over 150°. However, the hydrophobic / superhydrophobic coatings prepared by the above methods are all organic material coatings. Under certain operating conditions, organic coatings are prone to water absorption and swelling, aging, etc., leading to coating failure.

[0006] Chinese patent document CN114213881A discloses a method for preparing a superhydrophobic anticorrosive coating. This invention adds a superhydrophobic coating to the substrate on the basis of a strontium phosphate anticorrosive coating by using a strontium phosphate chemical conversion coating and a superhydrophobic coating with appropriate formulation and proportion. The superhydrophobic coating includes hydrophobic nano silica powder, polyurethane, fluorinated resin and adhesion promoter. Although the superhydrophobic coating in this invention is an organic-inorganic material coating, this method is only applicable to magnesium alloy substrates, and the amount of organic materials such as polyurethane added in the superhydrophobic coating is still relatively large.

[0007] Therefore, it is necessary to develop hydrophobic / superhydrophobic coatings based on inorganic materials to broaden the application scenarios of hydrophobic / superhydrophobic coatings and overcome the failure problems caused by water absorption, swelling, and aging of organic coatings. Summary of the Invention

[0008] This invention provides a method for preparing hydrophobic coatings using rare earth salt solution thermal spraying. The steps are simple and efficient, applicable to a variety of substrate materials, and can be prepared over a large area. The resulting hydrophobic coating has good adhesion to the substrate and exhibits excellent hydrophobic / superhydrophobic properties.

[0009] The specific technical solution adopted is as follows:

[0010] A method for preparing a hydrophobic coating using rare earth salt solution thermal spraying includes the following steps:

[0011] (1) The substrate surface is pretreated, including cleaning and roughening, to obtain the sample to be sprayed;

[0012] (2) Add rare earth salts to the solvent to prepare rare earth salt solution;

[0013] (3) A rare earth salt solution is sprayed onto the sample to be sprayed by thermal spraying technology to generate rare earth oxides on the surface of the sample and prepare a hydrophobic coating.

[0014] The rare earth salts mentioned are lanthanide rare earth salts.

[0015] This invention employs lanthanide rare earth salts and a specific liquid thermal spraying technology, which transforms the lanthanide rare earth salts through a series of thermo-physical and thermo-chemical transformations, ultimately forming nano-lanthanide rare earth oxides that adhere to the surface of the sample to be sprayed. The lanthanide rare earth oxides have a special electronic structure that can improve the hydrophobic properties of the sample surface.

[0016] The matrix includes metallic materials, ceramic materials, or metal-ceramic composite materials. The method of the present invention has a wide range of applications and can be applied to a variety of matrices.

[0017] Roughening the substrate surface can enhance the adhesion between the substrate and the coating.

[0018] The method of the present invention can not only directly modify the surface of the substrate to be hydrophobic, but also modify the surface of the coating to be hydrophobic; specifically, step (1) also includes the step of preparing the coating on the pretreated substrate surface using thermal spraying technology to obtain the sample to be sprayed.

[0019] Preferably, the thermal spraying technology in step (1) is electric arc spraying, and the spraying parameters are: current 50-200A, voltage 15-100V, compressed air pressure 0.1-1.5MPa, spraying distance 5-50cm, and electric arc gun moving speed 10-50mm / s.

[0020] Preferably, the raw material used in the thermal spraying technology in step (1) is metal wire, including aluminum wire, copper wire, zinc wire, tin wire, iron wire or nickel wire.

[0021] In step (2), the solvent is water and / or an organic solvent, preferably an aqueous ethanol solution.

[0022] In step (2), the rare earth salts include lanthanum salt (La), cerium salt (Ce), praseodymium salt (Pr), neodymium salt (Nd), promethium salt (Pm), samarium salt (Sm), europium salt (Eu), gadolinium salt (Gd), terbium salt (Tb), dysprosium salt (Dy), holmium salt (Ho), erbium salt (Er), thulium salt (Tm), or ytterbium salt (Yb); preferably lanthanum salt, cerium salt, or ytterbium salt.

[0023] In the rare earth salt solution, the concentration of rare earth metal ions is 0.1–2 M, preferably 0.5–1.5 M. If the concentration of rare earth metal ions is too low, the deposition rate of rare earth oxide thin layers will be slow; if it is too high, the oxide thin layer will be too thick, the degree of nano-sizing will be low, the coating quality will be reduced, and the hydrophobic properties will be decreased.

[0024] Preferably, in step (3), the thermal spraying technology is liquid flame spraying or plasma liquid spraying; the liquid flame spraying parameters are further preferably: the combustion gas is oxygen, and the pressure is 0.2-1.0 MPa; the combustion gas is acetylene, and the pressure is 0.05-0.4 MPa; the auxiliary gas is compressed air, and the pressure is 0.3-6.0 MPa; the spraying distance is 10-300 mm; the plasma liquid spraying parameters are further preferably: the working gas is argon and helium, the current is 100-700 A, the voltage is 30-100 V, the spraying distance is 50-150 mm, and the spray gun moving speed is 400-800 mm / s.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] (1) This invention uses lanthanide rare earth salts and specific liquid thermal spraying technology to generate nano rare earth oxides to improve the hydrophobicity of the substrate or coating surface. The process is simple, efficient, low-cost, and widely applicable, suitable for on-site construction and large-scale production.

[0027] (2) The hydrophobic coating prepared by the method of the present invention has good bonding performance with the substrate material, and can increase the contact angle of the sample to be sprayed to more than 135°. It has good self-cleaning properties and has broad application prospects in the field of coating preparation. Compared with the technology of hydrophobic / superhydrophobic modification by using polymer materials as low surface energy modifiers, the hydrophobic coating of the present invention will not have problems such as water absorption and swelling or aging, and has excellent durability and long-lasting effect. Attached Figure Description

[0028] Figure 1 The images show a comparison of SEM images of the pretreated substrate surface and the surface after thermal spraying of rare earth salt solution in Example 1.

[0029] Figure 2 The image shows the XRD characterization results of the substrate after thermal spraying with rare earth salt solution in Example 1.

[0030] Figure 3 The results show the hydrophobic properties of the substrate surface (A) and the surface (B) after thermal spraying of rare earth salt solution in Example 1.

[0031] Figure 4 This is a cross-sectional SEM image of the coating on the substrate surface in Example 4.

[0032] Figure 5 The image shows the XRD characterization results of the substrate in Example 4 after arc aluminum spraying and rare earth salt liquid thermal spraying.

[0033] Figure 6 The results are the hydrophobicity test results of the surface after thermal spraying of rare earth salt solution in Example 4. Detailed Implementation

[0034] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0035] Unless otherwise specified in the following examples and comparative examples, all techniques or conditions described in the literature in this field, or in accordance with the product instructions, shall be performed. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels or prepared using existing techniques.

[0036] Example 1

[0037] (1) Select a 2cm×2cm 316L stainless steel sheet as the base material;

[0038] (2) The substrate surface was cleaned with acetone and deionized water in sequence; then the substrate surface was roughened by sandblasting with 120-mesh brown corundum sand. The process parameters were: air pressure 0.5MPa, sandblasting time 30s, to obtain the sample to be sprayed.

[0039] (3) Mix 500g of deionized water with 500g of anhydrous ethanol, then add a certain amount of Ce(NO3)3·6H2O to prepare Ce 3+ Rare earth salt solution with a content of 1M;

[0040] (4) The rare earth salt solution prepared in step (3) is sprayed onto the sample to be sprayed using plasma liquid spraying technology. The parameters of plasma liquid spraying are: working gas is argon and helium (argon is used as powder feeding gas and helium is used as auxiliary gas), current is 100A, voltage is 30V, spraying distance is 7cm, and spray gun moving speed is 500mm / s; rare earth oxides are generated on the surface of the sample to be sprayed, and a hydrophobic coating is prepared.

[0041] Characterization of the surface after thermal spraying of rare earth salt solution revealed that a nano-CeO2 thin layer adhered to the substrate surface. Figure 1 XRD results also confirmed the presence of nano-CeO2. Figure 2 The average grain size of CeO2 was calculated to be 29 nm. Compared with the stainless steel substrate, the contact angle of the stainless steel substrate with attached nano-CeO2 increased from the original 80° to 137°, exhibiting excellent hydrophobicity. Figure 3 (A and B in the text).

[0042] Example 2

[0043] (1) Select a 2cm×2cm 1060 aluminum sheet as the substrate;

[0044] (2) The substrate surface was cleaned with acetone and deionized water in sequence; then the substrate surface was roughened by sandblasting with 60-mesh brown corundum sand. The process parameters were: air pressure 0.5MPa, sandblasting time 30s, to obtain the sample to be sprayed.

[0045] (3) Mix 500g of deionized water with 500g of anhydrous ethanol, then add a certain amount of Ce(NO3)3·6H2O to prepare Ce 3+ Rare earth salt solution with a content of 1.25M;

[0046] (4) The rare earth salt liquid material prepared in step (3) is sprayed onto the sample to be sprayed by liquid flame spraying technology. The parameters of liquid flame spraying are: the combustion gas is oxygen and the pressure is 0.5MPa; the combustion gas is acetylene and the pressure is 0.1MPa; the auxiliary gas is compressed air and the pressure is 0.4MPa; the spraying distance is 10cm; rare earth oxides are generated on the surface of the sample to be sprayed, and a hydrophobic coating is prepared.

[0047] Compared to the aluminum substrate, the contact angle of the aluminum substrate with attached nano CeO2 increased from the original 92° to 139°, exhibiting excellent hydrophobicity.

[0048] Example 3

[0049] (1) Select a 2cm×2cm 304 stainless steel sheet as the base material;

[0050] (2) The substrate surface was cleaned with acetone and deionized water in sequence; then the substrate surface was roughened by sandblasting with 120-mesh brown corundum sand. The process parameters were: air pressure 0.5MPa, sandblasting time 30s, to obtain the sample to be sprayed.

[0051] (3) Mix 500g of deionized water with 500g of anhydrous ethanol, then add a certain amount of Yb(NO3)3·5H2O to prepare Yb 3+ Rare earth salt solution with a content of 1M;

[0052] (4) The rare earth salt solution obtained in step (3) is sprayed onto the sample to be sprayed using plasma liquid spraying technology. The parameters of plasma liquid spraying are: argon and helium are used as working gases (argon is used as powder feeding gas and helium is used as auxiliary gas), current is 700A, voltage is 60V, spraying distance is 7cm, and spray gun moving speed is 500mm / s; rare earth oxides are generated on the surface of the sample to be sprayed, and a hydrophobic coating is prepared.

[0053] Compared to the stainless steel sheet substrate, the contact angle of the stainless steel substrate with attached nano-YbO2 increased from the original 83° to 149°, exhibiting excellent hydrophobicity.

[0054] Example 4

[0055] (1) Select a 2cm×2cm 316L stainless steel sheet as the base material;

[0056] (2) The substrate surface was cleaned with acetone and deionized water in sequence; then the substrate surface was roughened by sandblasting with 60-mesh brown corundum sand. The process parameters were: air pressure 0.5MPa, sandblasting time 30s, to obtain the pretreated substrate.

[0057] (3) The pretreated substrate was subjected to arc spraying. The spraying material was aluminum wire. The process parameters were: current 100A, voltage 25V, compressed air pressure 0.5MPa, spraying distance 15cm, and supersonic arc gun moving speed 20mm / s. An aluminum coating with a thickness of about 250μm was deposited on the surface of the pretreated substrate to prepare the sample to be sprayed.

[0058] (4) Mix 500g of deionized water with 500g of anhydrous ethanol, then add a certain amount of Ce(NO3)3·6H2O to prepare Ce. 3+ Rare earth salt solution with a content of 1M;

[0059] (5) Spray the rare earth salt liquid material obtained in step (4) onto the sample to be sprayed by plasma liquid material spraying technology. The parameters of plasma liquid material spraying are: argon and helium are used as working gas (argon is used as powder feeding gas and helium is used as auxiliary gas), current is 100A, voltage is 30V, spraying distance is 70mm, and spray gun moving speed is 500mm / s; rare earth oxides are generated on the surface of the sample to be sprayed, and a hydrophobic coating is prepared.

[0060] Cross-sectional SEM image of the coating on the stainless steel sheet substrate surface is shown below. Figure 4 As shown, a thin layer of nano-CeO2 cerium oxide was found to be attached to the surface of the aluminum coating; XRD results also confirmed the presence of nano-CeO2. Figure 5 The average grain size of CeO2 was calculated to be 81 nm; the contact angle of the aluminum coating with attached nano-CeO2 increased from 20° to 154°. Figure 6 It has superhydrophobic properties.

[0061] The embodiments described above provide a detailed explanation of the technical solutions of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a hydrophobic coating using rare earth salt solution thermal spraying, characterized in that, Includes the following steps: (1) The substrate surface is pretreated, including cleaning and roughening, to obtain the sample to be sprayed; (2) Add rare earth salts to the solvent to prepare rare earth salt solution; (3) A rare earth salt solution is sprayed onto the sample to be sprayed by thermal spraying technology to generate rare earth oxides on the surface of the sample and prepare a hydrophobic coating. In step (2), the solvent is an aqueous ethanol solution, and the rare earth salt is Ce(NO3)3·6H2O or Yb(NO3)3·5H2O; In rare earth salt solutions, the concentration of rare earth metal ions is 0.1–2 M; In step (3), the thermal spraying technology is liquid flame spraying or plasma liquid spraying; the parameters of liquid flame spraying are: the combustion gas is oxygen, the pressure is 0.2-1.0 MPa; the combustion gas is acetylene, the pressure is 0.05-0.4 MPa; the auxiliary gas is compressed air, the pressure is 0.3-6.0 MPa; the spraying distance is 10-300 mm; the parameters of plasma liquid spraying are: the working gas is argon and helium, the current is 100-700 A, the voltage is 30-100 V, the spraying distance is 50-150 mm, and the spray gun moving speed is 400-800 mm / s.

2. The method for preparing a hydrophobic coating using rare earth salt solution thermal spraying according to claim 1, characterized in that, The matrix includes metallic materials, ceramic materials, or metal-ceramic composite materials.

3. The method for preparing a hydrophobic coating using rare earth salt solution thermal spraying according to claim 1, characterized in that, Step (1) also includes the step of preparing a coating on the pretreated substrate surface using thermal spraying technology to obtain the sample to be sprayed.

4. The method for preparing a hydrophobic coating using rare earth salt solution thermal spraying according to claim 3, characterized in that, The thermal spraying technology for preparing the coating in step (1) is electric arc spraying. The spraying parameters are: current 50-200A, voltage 15-100V, compressed air pressure 0.1-1.5MPa, spraying distance 5-50cm, and arc gun moving speed 10-50mm / s.

5. The method for preparing a hydrophobic coating using rare earth salt solution thermal spraying according to claim 3, characterized in that, The thermal spraying technology in step (1) uses metal wires, including aluminum wires, copper wires, zinc wires, tin wires, iron wires, or nickel wires.

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