Preparation method of durability self-reinforced transparent super-hydrophobic coating based on steel slag

Abstract

The invention discloses a preparation method of a durability self-reinforced transparent super-hydrophobic coating based on steel slag. The method comprises the following steps: firstly, co-dispersing steel slag micro powder and a one-dimensional / two-dimensional nano material (such as hydroxylated multi-walled carbon nanotubes, cellulose nanofibers and the like) in an alcohol solvent to form a suspension, and carrying out spraying and high-temperature heat treatment to construct a micro-nano rough porous substrate; then, a solution obtained after hydrolytic condensation of perfluoroalkyl silane is sprayed to the surface of a substrate, and hydrophobic modification is achieved after drying and curing. The coating with the micro-nano hierarchical structure is successfully prepared through the synergistic effect of the micro-nano structure of the steel slag and the low-surface-energy substance in combination with the optimized spraying and heat treatment process. The static water contact angle of the coating is gt; the angle is 150 degrees, and the sliding angle is 1t; the visible light transmittance is gt at 10 degrees; and moreover, the coating shows excellent mechanical wear resistance, environmental stability, self-cleaning property and anti-icing function. The method is simple in process and low in cost, realizes high value-added utilization of the industrial waste steel slag, and has wide application prospects in the fields of building glass, traffic equipment, solar panels and the like.

Description

Technical Field

[0001] This invention relates to a method for preparing a durable, self-reinforcing, transparent, superhydrophobic coating based on steel slag, and more particularly to a technique for constructing a transparent superhydrophobic surface using industrial waste steel slag and carbon nanotubes, belonging to the interdisciplinary field of green functional material development and surface engineering technology. Background Technology

[0002] Transparent superhydrophobic coatings, possessing extremely high water contact angles (>150°) and extremely low water slip angles (<10°), have attracted widespread attention in recent years due to their unique wettability control capabilities, demonstrating significant application value in fields such as self-cleaning glass, anti-icing optical devices, anti-icing surfaces, and photovoltaic module protection. It is generally believed that the preparation of transparent superhydrophobic coatings requires simultaneously meeting two core conditions: first, reducing the surface free energy of the solid through modification with low surface energy materials; and second, constructing micro- to nano-scale rough structures to trap air and form an air cushion layer. For steel slag-based coatings, the porous microparticles and irregular surface morphology inherent in them naturally provide micro- to nano-rough structures, offering a structural basis for constructing transparent superhydrophobic surfaces.

[0003] Various methods exist for preparing transparent superhydrophobic coatings, but traditional techniques often involve organic solvents. Chinese invention patent CN116924698A embeds a thin layer of hydrophobic silica on the surface of a polyurethane layer, while controlling the curing temperature to 120–180°C, resulting in high transmittance of the polyurethane. Chinese invention patent CN105541119B uses a sol-gel method to form a micro / nano binary rough structure on the coating surface, achieving a transparent coating; however, the use of organic solvents such as methanol limits its industrial-scale application. Although these methods achieve high hydrophobicity, their stability and transparency are poor, making it difficult to meet the requirements for long-term use.

[0004] To address this, researchers have developed a highly stable transparent superhydrophobic coating preparation technology. Chinese invention patent CN110078387A designed a three-layer structure, combined with modified polysiloxane, and prepared a highly transparent superhydrophobic coating through a dip-coating process; Chinese invention patent CN119735971A utilized the reaction between the amino group of the hydrolyzed silane coupling agent and the carboxyl group of the chain fatty acid to graft the chain alkyl group onto the surface of silica particles, obtaining a superhydrophobic coating that maintains high transparency. However, these technologies still have limitations: (1) large fluctuations in raw material composition lead to unstable performance and affect the uniformity of the coating; (2) it is difficult to balance light transmittance and superhydrophobicity. High light transmittance coatings (>90%) often have reduced hydrophobicity (contact angle <150°) due to insufficient roughness, while high hydrophobic coatings have light transmittance below 85% due to enhanced scattering; (3) there is a lack of stability assessment under extreme conditions. Existing studies only test the contact angle at room temperature and do not involve the performance maintenance capability in outdoor and frictional environments, which limits its practical application in industrial scenarios.

[0005] Currently, although some methods exist for preparing transparent superhydrophobic coatings, research reports on their application to hard substrates such as glass while simultaneously achieving high transparency, excellent superhydrophobicity, and good stability are relatively few, and many challenges remain in practical applications. For example, some studies have used electrodeposition technology to form micro-nano composite structures on metal substrates to achieve superhydrophobicity, but this method requires sophisticated equipment and is difficult to apply directly to non-conductive substrates such as glass. Chinese invention patent CN114409264B explores a new plasma-enhanced chemical vapor deposition technology, in which a glass substrate is immersed in a hydrofluoric acid solution for etching, and the prepared silicon carbide film is subjected to plasma treatment by introducing methane, carbon tetrafluoride, and oxygen as working gases to obtain transparent superhydrophobic glass. However, the complex preparation method and high cost remain limiting factors in the practical application of this patented technology, requiring further optimization of the formulation and process.

[0006] While the aforementioned methods each have their own advantages, significant shortcomings remain in achieving efficient, environmentally friendly, low-cost, and large-scale industrial production of transparent superhydrophobic glass coatings. In particular, how to improve the coating's weather resistance, abrasion resistance, and chemical stability while maintaining its superhydrophobic properties and transparency has become a current research hotspot and challenge.

[0007] Currently, there are no widely accepted successful cases or application reports regarding the preparation of superhydrophobic glass coatings with high transparency, excellent superhydrophobicity, good stability, and environmental adaptability using spraying processes, high-temperature treatment technologies, and widely available raw materials. Meanwhile, developing a technology that can easily and rapidly prepare stable superhydrophobic glass coatings under factory conditions is a pressing market need and a topic of significant application value. Summary of the Invention

[0008] In view of the shortcomings of existing transparent superhydrophobic coatings in terms of raw material cost, environmental friendliness, balance between light transmittance and hydrophobicity, and long-term durability, this invention aims to provide a method for preparing a durable self-reinforcing transparent superhydrophobic coating based on steel slag.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a durable, self-reinforcing, transparent, superhydrophobic coating based on steel slag includes the following steps: Construction of the porous substrate: Using an alcohol solvent (such as anhydrous ethanol) as the dispersion medium, a catalyst (such as ammonia) is added to co-disperse steel slag powder with one-dimensional or two-dimensional nanomaterials (such as hydroxylated multi-walled carbon nanotubes, cellulose nanofibers, etc.) to form a uniform suspension A. Subsequently, this suspension is coated onto a pre-cleaned substrate (such as glass) using a spraying process, followed by high-temperature heat treatment at 400-1000℃ to form a porous substrate with a micro-nano hierarchical rough structure. During this process, the steel slag and nanomaterials form a stable composite structure at high temperature, providing a key structural basis for the superhydrophobic properties.

[0010] 2. Surface hydrophobication modification: A low surface energy material (perfluoroalkylsilane, such as perfluorodecyltrimethoxysilane) is mixed with an alcohol solvent and a catalyst (such as ammonia and deionized water) to carry out a hydrolysis-condensation reaction, thus preparing solution B. Solution B is uniformly coated onto the surface of the porous substrate prepared above using a spraying process, and finally dried and cured at 60-160℃, so that the perfluoroalkylsilane is chemically bonded to the micro-nano rough structure, thereby achieving superhydrophobicity of the surface.

[0011] Compared with the prior art, the present invention has the following significant advantages: 1. Resource utilization and low cost: It innovatively uses industrial waste steel slag as one of the main raw materials, realizing high value-added utilization of solid waste, significantly reducing raw material costs, and conforming to the concept of green and sustainable development.

[0012] 2. Excellent and balanced performance: An ideal micro-nano hierarchical rough structure was constructed by synergistic enhancement of the micro-nano structure of steel slag and one-dimensional / two-dimensional nanomaterials; combined with the low surface energy modification of perfluoroalkylsilane, a coating with high transparency (visible light transmittance >90%) and superhydrophobicity (static water contact angle >150°, sliding angle <10°) was successfully prepared, effectively solving the technical problem of difficulty in achieving both transmittance and hydrophobicity.

[0013] 3. Self-enhancing durability: The coating exhibits excellent mechanical wear resistance, environmental stability, and chemical stability. After outdoor exposure testing, it maintains high hydrophobicity and transparency; friction tests show that its wear resistance is significantly better than the control sample without added steel slag. Especially after high-temperature carbonization treatment in a CO2 environment, the coating's stability is further "self-enhanced," demonstrating a longer service life.

[0014] 4. Simple process and easy to promote: The preparation method mainly adopts spraying and heat treatment. The process is simple, has low equipment requirements, and does not require a complex vacuum or etching environment. It is very suitable for large-scale industrial production and application on complex shaped substrates. It has broad application prospects in fields such as architectural glass, solar panels, and transportation equipment. Attached Figure Description

[0015] Figure 1 Scanning electron microscope (SEM) image of the SS@POS1 coating.

[0016] Figure 2 (a) SEM images of SS@POS1, (b) SS@POS2, (c) SS@POS3, (d) SS@POS4 and (e) Comparative Example 1 SS@POS0.

[0017] Figure 3 (a) XPS and (b) C 1s spectra of the SS@POS1 coating.

[0018] Figure 4 Light transmittance of transparent superhydrophobic coatings with different contents of hydroxylated multi-walled carbon nanotubes.

[0019] Figure 5 (a) Comparison of the cleanliness of SS@POS1 coated glass before and after 40 days of outdoor placement; (b) Comparison of the cleanliness of ordinary glass before and after 40 days of outdoor placement.

[0020] Figure 6 Static water contact angle and sliding angle data and corresponding images of transparent superhydrophobic coatings with different hydroxylated multi-walled carbon nanotube (CNT) contents.

[0021] Figure 7 (a) is an image of water, tea and coffee droplets on the SS@POS1 coating; (b) is a specular reflection phenomenon of the SS@POS1 coating when placed in water; (c) and (d) are schematic diagrams of the self-cleaning process of the SS@POS1 coating.

[0022] Figure 8 The contact angle changes and corresponding photographs of superhydrophobic coatings with carbon fixation times of 0h, 2h, 4h and 8h after friction.

[0023] Figure 9 (a) Light transmittance of the coating before outdoor exposure test, (b) Light transmittance of the coating after 120 days of outdoor exposure test.

[0024] Figure 10 (a) Freezing process of water droplets (15µL) on ordinary glass and (b) on SS@POS1 coated glass (-15℃). (c) Freezing process of water mist on ordinary glass (-15℃) and (d) after freezing. (e) Freezing process of water mist on SS@POS1 coated glass (-15℃) and (f) after freezing. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0026] Example 1 1. Preparation of Suspension A: Accurately weigh 0.5 g of steel slag powder with a particle size of 5-75 μm and 0.09 g of hydroxylated multi-walled carbon nanotubes (diameter > 50 nm, length 0.5-2 μm), and place them in 50 mL of anhydrous ethanol. At room temperature (25±2℃), first stir with a magnetic stirrer at 500 rpm for 15 minutes, then sonicate for 5 minutes to obtain a uniformly dispersed suspension A.

[0027] 2. Construction of the porous substrate: The above suspension A was loaded into a commercial spray gun (nozzle diameter 0.5 mm) and sprayed at a uniform rate onto the surface of a pre-cleaned and dried glass slide (76 mm × 26 mm) under an air pressure of 0.2 MPa. The sprayed sample (labeled SS / CNT) was transferred to a tube furnace and heated to 600°C at a rate of 5°C / min under an air atmosphere, and held at that temperature for 1 hour. Subsequently, it was cooled to room temperature with the furnace to obtain a porous substrate with a micro-nano rough structure.

[0028] 3. Preparation of Solution B: Measure 48 mL of anhydrous ethanol into a beaker, add 0.15 mL of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (PFDS) and 0.4 mL of 25-28% ammonia solution, then add 1 mL of deionized water. Stir continuously with a magnetic stirrer at room temperature for 150 minutes, followed by sonication for 5 minutes to obtain the hydrolyzed and condensed solution B.

[0029] 4. Hydrophobic Modification and Curing: Using the spray gun described above, approximately 1 mL of solution B was uniformly sprayed onto the porous substrate surface obtained in step 2 at a pressure of 0.35 MPa (approximately 50 psi). The sample was then transferred to a forced-air drying oven and cured at 140°C for 30 minutes. After natural cooling, a durable, self-reinforcing, transparent superhydrophobic coating based on steel slag, designated SS@POS1, was obtained.

[0030] Example 2 Replace the hydroxylated multi-walled carbon nanotubes in Example 1 with 0.03 g, and prepare suspension A in the same manner.

[0031] Following the same procedure as in step 2 of Example 1, the sample was heat-treated at 600°C to obtain a sample labeled SS / CNT2.

[0032] The rest is the same as step 3 in Example 1.

[0033] Solution B was sprayed onto the SS / CNT2 substrate and cured at 140°C for 30 minutes to obtain the coating number SS@POS2.

[0034] Example 3 Replace the hydroxylated multi-walled carbon nanotubes in Example 1 with 0.06 g, and prepare suspension A in the same manner.

[0035] Following the same procedure as in step 2 of Example 1, the sample was heat-treated at 600°C to obtain a sample labeled SS / CNT3.

[0036] The rest is the same as step 3 in Example 1.

[0037] Solution B was sprayed onto the SS / CNT3 substrate and cured at 140°C for 30 minutes to obtain the coating number SS@POS3.

[0038] Example 4 Replace the hydroxylated multi-walled carbon nanotubes in Example 1 with 0.12 g, and prepare suspension A in the same manner.

[0039] Following the same procedure as in step 2 of Example 1, the sample was heat-treated at 600°C to obtain a sample labeled SS / CNT4.

[0040] The rest is the same as step 3 in Example 1.

[0041] Solution B was sprayed onto the SS / CNT4 substrate and cured at 140°C for 30 minutes to obtain coating number SS@POS3.

[0042] Comparative Example 1 Replace the hydroxylated multi-walled carbon nanotubes in Example 1 with 0 g, and prepare suspension A in the same manner.

[0043] Following the same procedure as in step 2 of Example 1, the sample was heat-treated at 600°C to obtain a sample labeled SS / CNT0.

[0044] The rest is the same as step 3 in Example 1.

[0045] Solution B was sprayed onto the SS / CNT2 substrate and cured at 140°C for 30 minutes to obtain the coating number SS@POS0.

[0046] Structural characterization and performance evaluation The coated samples prepared above were subjected to the following tests to characterize their structure and properties: 1. Surface morphology and structural characterization: The surface morphology of SS@POS1, SS@POS2, SS@POS3, SS@POS4, and the comparative example SS@POS0 was observed using scanning electron microscopy (SEM). Figure 1-2 As shown, the addition of an appropriate amount of hydroxylated multi-walled carbon nanotubes can significantly enhance the micro-nano hierarchical rough structure of the coating, forming a porous network, which is beneficial for air trapping and the stability of the Cassie-Baxter state. When the carbon nanotube content is too high, the structure tends to be dense, which is not conducive to maintaining the superhydrophobic properties.

[0047] X-ray photoelectron spectroscopy (XPS): Surface chemical composition was analyzed using XPS. XPS measurement spectra ( Figure 3 a) The presence of F 1s (688.1 eV), O 1s (531.7 eV), C 1s (291.0 eV), and Si 2p (102.3 eV) peaks was confirmed, and the fluorine content was very high at 51.26%, indicating that the perfluoroalkylsilane had been successfully grafted onto the surface of the steel slag particles. High-resolution C1s spectrum ( Figure 3 b) Three characteristic peaks are present: 292.8 eV (-CF3), 290.5 eV (-CF2) and 284.2 eV (CC), which are consistent with the chemical structure of the perfluoroalkyl long chain with the main peak of -CF2.

[0048] 2. Optical performance testing: UV-Vis spectrophotometer: Tests the transmittance of the coating in the wavelength range of 400-800 nm. Results are as follows... Figure 4 As shown, the coating of Example 1 (SS@POS1) has a transmittance of over 90% at 550 nm, and the coatings of each example maintain high transparency throughout the visible light spectrum.

[0049] 3. Wetting performance test: Static water contact angle and sliding angle: Using a contact angle meter, a 5 μL drop of deionized water was placed on the coating surface, and the static water contact angle was measured; the sliding angle when the 5 μL water droplet began to roll was also measured. Results are as follows: Figure 6 As shown, the coating of Example 1 (SS@POS1) exhibits a static water contact angle greater than 150° and a sliding angle less than 10°, demonstrating excellent superhydrophobic properties. In contrast, Comparative Example 1, lacking low surface energy modification, has a contact angle of only about 138°.

[0050] 4. Durability and stability testing: Environmental durability: SS@POS1 coated samples were fixed to the exterior wall of a building along with ordinary glass plates and subjected to a 40-day outdoor exposure test. Figure 5 As shown, after 40 days, ordinary glass surfaces showed obvious dust and stains, while the SS@POS1 coated surface remained clean. Its water contact angle was still greater than 140°, and the decrease in light transmittance was less than 5%.

[0051] High-temperature carbon fixation self-enhancing effect: The SS@POS1 coating was placed in a tube furnace under a carbon dioxide atmosphere at 200℃ for high-temperature carbon fixation for 0, 2, 4, and 8 hours respectively. A pressure of 163.3 Pa was applied to the coatings with different carbon fixation times, and linear reciprocating friction tests were conducted (20 cm per cycle). The water contact angle was measured after a certain number of friction cycles. Figure 8 As shown, the coating with carbon fixation for 8 hours exhibits superior wear resistance. After 10 friction cycles, its water contact angle (approximately 144°) is still significantly higher than that of the coating without carbon fixation after one friction cycle (approximately 107°), demonstrating that the carbon fixation treatment achieves a "self-reinforcing" effect on the coating.

[0052] Anti-icing performance: At -15°C, a 15µL water droplet completely freezes on a regular glass slide within 88 seconds; while the same volume droplet on the SS@POS1 coating takes 433 seconds. Figure 10 ab). SS@POS1 coated glass and ordinary glass were placed 10 cm below the nozzle of a modified humidifier spray hose and continuously sprayed at -15°C. Extensive icing consisting of fine ice particles appeared on the ordinary glass surface within 220 seconds, while droplets on the SS@POS1 coated surface did not completely freeze until approximately 420 seconds later. Figure 10 (cf), indicating that the coating has excellent delayed icing and anti-icing capabilities.

[0053] The above embodiments and test results demonstrate that this invention successfully prepared a coating that combines high transparency, excellent superhydrophobicity, outstanding mechanical durability, and environmental stability. By utilizing industrial steel slag, a low-cost, green, high-performance functional coating has been prepared, possessing enormous application potential.

Claims

1. A method for preparing a durable, self-reinforced, transparent, superhydrophobic coating based on steel slag, characterized in that, Includes the following steps: (1) Preparation of porous substrate: Using alcohol solvent as dispersion medium, a catalyst is added to co-disperse steel slag micro powder with one-dimensional or two-dimensional nanomaterials to form suspension A; Suspension A is coated onto a pre-cleaned substrate surface using a spraying process, followed by high-temperature heat treatment to form a porous substrate with a micro-nano rough structure. (2) Hydrophobic modification: The low surface energy material is mixed with alcohol solvent and catalyst to prepare solution B. Solution B is coated on the porous substrate surface obtained in step (1) by spraying process. After drying and curing, the transparent superhydrophobic coating is obtained.

2. The method according to claim 1, characterized in that: The one-dimensional or two-dimensional nanomaterials are selected from at least one of hydroxylated multi-walled carbon nanotubes, carboxylated multi-walled carbon nanotubes, cellulose nanofibers, and nano-silica linear structures.

3. The method according to claim 1, characterized in that: The low surface energy material is a perfluoroalkylsilane, selected from at least one of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, and tridecafluorooctyltriethoxysilane.

4. The method according to claim 1, characterized in that: The steel slag powder has a particle size of 1-100 μm and a mass concentration of 0.1-2.0 g / 50mL in suspension A; the one-dimensional or two-dimensional nanomaterial has a tube diameter of 5-100 nm and a length of 0.1-10 μm and a mass concentration of 0.01-0.5 g / 50mL in suspension A.

5. The method according to claim 1, characterized in that: The low surface energy substance has a volume fraction of 0.2-0.3% in solution B; the catalyst is ammonia water with a concentration of 25-28% and a volume fraction of 0.1-10% in solution B.

6. The method according to claim 1, characterized in that: The alcohol solvent is selected from at least one of methanol, ethanol, and isopropanol; the catalyst is selected from at least one of deionized water, ammonia, and hydrochloric acid.

7. The method according to claim 1, characterized in that: The high-temperature heat treatment is carried out in a tube furnace at a temperature of 400-1000℃ and a holding time of 0.5-10 hours; the drying and curing are carried out in a forced-air drying oven at a temperature of 60-160℃ and a time of 1-100 minutes.

8. The method according to claim 1, characterized in that: The coating has a static water contact angle greater than 150°, a sliding angle less than 10°, and a transmittance greater than 90% in the visible light band (400-800 nm).

9. A transparent superhydrophobic coating prepared by the method according to any one of claims 1-8, characterized in that: The coating has a micro-nano hierarchical structure and possesses self-cleaning, anti-icing, wear resistance, and environmental stability.

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