Fluorine-free super-hydrophobic micro-nano structure SiO2 / TiN anti-icing and photothermal de-icing coating

Abstract

The present application relates to ice-repellent and photothermal de-icing coating, in particular to a fluorine-free super-hydrophobic micro-nano structure SiO2 / TiN ice-repellent and photothermal de-icing coating.The present application successfully develops a fluorine-free photothermal super-hydrophobic SiO2 / TiN coating through simple polymerization and spraying technology.After a series of durability tests such as etching and abrasion test in harsh environment, the obtained coating can still maintain good super-hydrophobicity due to excellent mechanical stability and chemical stability.In addition, the coating also shows good anti-icing ability and excellent photothermal effect, and the coating can still maintain super-hydrophobicity after 500 icing / thawing cycles, and has good self-cleaning effect and corrosion resistance.Good ice-repellent and de-icing ability is mainly due to the super-hydrophobic surface generated by micro-nano hierarchical structure and low surface energy chemical modification and the photothermal effect of TiN nanoparticles.Benefiting from strong mechanical and chemical stability, this study provides a promising ice-repellent / de-icing coating for large-scale practical application.

Description

Technical Field

[0001] This invention relates to anti-icing and photothermal de-icing coatings, and particularly to a fluorine-free superhydrophobic micro / nano structure SiO2 / TiN anti-icing and photothermal de-icing coating. Background Technology

[0002] Icing in nature causes significant problems in our daily lives. For example, driving on icy roads increases the risk of car accidents. Icing on aircraft wings can reduce flight speed and even lead to serious crashes. Icing on power lines can easily cause electrical short circuits. These icing phenomena not only increase energy consumption but also pose a threat to personal safety. Traditional strategies for solving these problems mainly include mechanical vibration, chemical anti-icing agents, and electrothermal de-icing. These methods are not only inefficient and costly but also harmful to the environment. Therefore, considerable effort has been invested in developing new anti-icing / de-icing technologies to inhibit ice accumulation while removing surface ice.

[0003] Superhydrophobic surfaces offer an effective way to delay freezing time. This is based on the presence of an air layer within the surface texture, which significantly reduces the contact area between water droplets and the solid substrate. Fabricating superhydrophobic coatings from photothermal materials can effectively convert solar energy into heat and promote ice removal without additional energy input. For example, a technique for preparing black superhydrophobic surfaces on carbon steel by combining multi-pulse laser ablation and hexadecyltrimethoxysilane chemical modification has been developed. Compared to bare carbon steel substrates, the resulting coating with a water contact angle (WCA) of 156° exhibits a longer freezing time and three times the de-icing force. A fully water-based superhydrophobic coating was constructed using carbon nanotubes, polydopamine, and silver particles as photothermal materials, and then mixed with a fluorinated polyacrylic acid emulsion. Under xenon lamp irradiation, the ice melting time of the coating was reduced by 982 seconds compared to the original surface. Although various anti-icing and de-icing strategies have been proposed in recent years, the poor durability, limited functionality, use of fluorinated materials, and complex preparation techniques of photothermal superhydrophobic coatings severely hinder their practical application under harsh conditions. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a fluorine-free superhydrophobic micro / nano structure SiO2 / TiN anti-icing and photothermal de-icing coating.

[0005] This invention is achieved through the following technical solution:

[0006] A fluorine-free, superhydrophobic micro / nanostructured SiO2 / TiN anti-icing and photothermal de-icing coating, wherein the coating is prepared by the following method:

[0007] Step 1: Under magnetic stirring, TiN nanospheres and SiO2 microspheres were dispersed in a mixture of 3-(isobutenoyloxy)propyltrimethoxysilane KH-570, ethanol and H2O, and the pH was adjusted to 4.0-5.0 with acetic acid to obtain a mixture.

[0008] Step 2: The mixture obtained in Step 1 is reacted at 60°C for 2.0 hours with stirring. The above solution is purified by centrifugation and washed with ethanol.

[0009] Step 3: The product obtained in Step 2 is dispersed in ethanol, and then mixed with octadecyl methacrylate (SMA) and 2,2'-azobisisobutyronitrile (AIBN). The polymerization process is carried out at 60°C with stirring for 2.0 h to obtain modified particles.

[0010] Step 4: Photothermal superhydrophobic coatings were prepared by using modified particles in different proportions and E-51-based adhesives through a two-step spraying technique.

[0011] Furthermore, in step one, the mass of TiN nanospheres is 3.0 g, the mass of SiO2 microspheres is 2.0 g, the volume of 3-(isobutenoyloxy)propyltrimethoxysilane KH-570 is 5.0 mL, the volume of ethanol is 22.0 mL, and the volume of H2O is 2.0 mL.

[0012] Furthermore, in step three, the volume of ethanol is 20.0 mL, the volume of octadecyl methacrylate (SMA) is 3.0 mL, and the mass of 2,2'-azobisisobutyronitrile (AIBN) is 0.05 g.

[0013] Furthermore, in step four, the photothermal superhydrophobic coating is prepared as follows: First, the modified particles, ethanol, and E-51-based adhesive are mixed and stirred for 5 minutes to form a homogeneous solution; then, the above solution is sprayed onto a glass substrate and cured at 80°C for 3.0 minutes. Next, a homogeneous mixture of 0.066g of E-51-based adhesive and 3.0mL of modified particles is sprayed onto the coating surface a second time and cured at 120°C for 6.0 hours.

[0014] Furthermore, the modified particles amounted to 0.9 mL, the ethanol to 2.1 mL, and the E-51-based binder to 0.972 g.

[0015] Furthermore, the modified particles have a particle content of 15.1 wt% and a m SiO2 / m TiN It has a ratio of 3 / 2, making it the best in terms of superhydrophobicity.

[0016] Compared with the prior art, the advantages of the present invention are as follows:

[0017] (1) A fluorine-free photothermal superhydrophobic SiO2 / TiN coating was successfully developed using a simple polymerization and spraying technique. After a series of durability tests, including etching and wear tests under harsh environments, the coating maintained its excellent superhydrophobicity due to its superior mechanical and chemical stability. Furthermore, the coating exhibited good anti-icing ability and excellent photothermal effect, extending the water droplet freezing time by 3.6 times compared to ordinary sunlight irradiation conditions, while simultaneously raising the surface temperature to 133.8℃ on exposed substrates. The coating maintained its superhydrophobicity after 500 freezing / thawing cycles, while also demonstrating good self-cleaning and corrosion resistance. The excellent anti-icing and de-icing capabilities are mainly attributed to the superhydrophobic surface generated by the micro / nano hierarchical structure and low surface energy chemical modification, as well as the photothermal effect of the TiN nanoparticles. Thanks to its strong mechanical and chemical stability, this research provides a promising anti-icing / de-icing coating for large-scale practical applications.

[0018] (2) This invention effectively integrates passive de-icing and active anti-icing capabilities into a fluorine-free photothermal superhydrophobic coating through a simple polymerization and two-step spraying process. The SiO2 / TiN mixture exhibits a distinct micro / nano structure and excellent superhydrophobic properties. Under simulated sunlight irradiation conditions, the coated aluminum plate achieves over 90% solar absorption and generates a significant temperature rise of 105.5°C within 5 minutes. Furthermore, the synthesized superhydrophobic coating demonstrates excellent resistance to tape peeling, Taber abrasion, solution immersion, and freezing / thawing cycle tests. Self-cleaning and corrosion resistance further contribute to its long-term outdoor application. Attached Figure Description

[0019] The invention will now be further described with reference to the accompanying drawings.

[0020] Figure 1 A schematic diagram of the preparation process of the superhydrophobic photothermal SiO2 / TiN coating;

[0021] Figure 2 XPS spectra and high-resolution C1s spectra of raw particles, alkylated particles and modified particles; (a) XPS spectra of raw particles, alkylated particles and modified particles; (b) High-resolution C1s spectra of raw particles, alkylated particles and modified particles.

[0022] Figure 3 High-resolution N1s, Si 2p, Ti 2p and O1s spectra of the modified particles;

[0023] Figure 4 SEM images at different magnifications and corresponding Si and Ti elemental mapping images, the cross-sectional SEM images of the obtained superhydrophobic coating and the corresponding Ti elemental mapping images;

[0024] Figure 5WCA and WRA histograms and m values ​​of water droplets with particle contents of 3.4%, 9.7%, 15.1%, and 20.0% respectively. SiO2 / m TiN WCA and WRA of water droplets at 1 / 1, 6 / 5, 3 / 2, 2 / 1 and 3 / 1 respectively;

[0025] Figure 6 Superhydrophobicity of the coating; (a) WCA and WRA of various liquids, including HCl solution (pH=1.0), NaOH solution (pH=14.0), NaCl solution (0.1M), milk, tea and coffee on the coating surface; (b) High-speed camera capture of the bouncing process of water droplets on the coating surface.

[0026] Figure 7-15 The freezing process of water droplets on bare and coated aluminum plates at ℃;

[0027] Figure 8 Curves showing the change in force over time required to remove a 1cm×1cm×1cm ice block from the surfaces of Al sheets and SiO2 / TiN coatings, respectively.

[0028] Figure 9 Absorption and reflectance spectra of bare glass, glass coated only with SiO2 coating, and raw glass with SiO2 / TiN coating;

[0029] Figure 10 Photothermal effect of coating; (a) Temperature change of bare aluminum plate and SiO2 / TiN coated aluminum plate under xenon lamp irradiation for 5 min; (b) Temperature change curves of bare glass and coated glass under xenon lamp irradiation for 6 min; (c) Temperature difference between coated glass and bare glass with different TiN mass ratios under xenon lamp irradiation for 5 min.

[0030] Figure 11 Actual de-icing experiment of exposed glass and coated glass at 0℃ in Jinan;

[0031] Figure 12 WCA of water droplets after the coating was immersed in different liquids for different times;

[0032] Figure 13 Changes in WCA and WRA of water droplets on the coating surface under different Taber wear test cycles under a 250g load;

[0033] Figure 14 Adhesion tests of coatings; (a) Comparison of optical photographs after tape peel test of top coating (left) and double coating (right); (b) Adhesion of coatings to various substrates;

[0034] Figure 15 Changes in WCA and WRA of water droplets on the coating surface during icing / de-icing cycles;

[0035] Figure 16 The self-cleaning performance of pollutants was tested using sand to simulate their properties.

[0036] Figure 17 The anti-corrosion effect of the coating; (a) Surface morphology changes of coated copper plate and bare copper plate during 300 hours of salt spray corrosion; (b) Tafel polarization curves of bare copper plate and coated copper plate before and after corrosion at different times;

[0037] Figure 18 EIS of coated copper plates and bare copper plates before and after corrosion at different times. Detailed Implementation

[0038] The present invention will be further described below with reference to embodiments.

[0039] Example 1

[0040] Experimental materials and instruments

[0041] Table 1 Main Raw Materials and Reagents

[0042]

[0043]

[0044] Table 2 Main Experimental Instruments and Equipment

[0045]

[0046] Example 2

[0047] Experimental preparation method

[0048] TiN nanospheres (3.0 g) and SiO2 microspheres (2.0 g) were dispersed under magnetic stirring in a mixture of 3-(isobutyryloxy)propyltrimethoxysilane (KH-570) (5.0 mL), 22.0 mL ethanol, and 2.0 mL H2O, and the pH was adjusted to 4.0–5.0 with acetic acid. The mixture was reacted at 60 °C for 2.0 h with stirring. The above solution was purified by centrifugation and washed with ethanol. Then, the product was dispersed in 20.0 mL ethanol and mixed with 3.0 mL octadecyl methacrylate (SMA) and 0.05 g 2,2'-azobisisobutyronitrile (AIBN). The polymerization process was carried out at 60 °C with stirring for 2.0 h to obtain modified particles.

[0049] A photothermal superhydrophobic coating was prepared using a two-step spraying technique with modified particles and E-51-based adhesive in different proportions. First, 0.9 mL of modified particles, 2.1 mL of ethanol, and 0.972 g of E-51-based adhesive were mixed and stirred for 5 minutes to form a homogeneous solution. This solution was then sprayed onto a glass substrate (25 cm × 75 cm) and cured at 80 °C for 3.0 min. Next, a homogeneous mixture of 0.066 g of E-51-based adhesive and 3.0 mL of modified particles was sprayed onto the coating surface a second time and cured at 120 °C for 6.0 h.

[0050] Example 3

[0051] Testing and Characterization

[0052] Surface morphology and elemental distribution were characterized using a heliocentric emission scanning electron microscope (FE-SEM) Regulus 8220 equipped with an energy-dispersive spectroscopy (EDS) instrument. X-ray photoelectron spectroscopy (XPS) measurements were performed on a Thermo Fisher Scientific EscaLab Xi+ spectrometer using Al Kα X-rays as the light source. Fourier transform infrared (FTIR) spectra were collected on a Nicolet IS20 spectrometer (Thermo Fisher Scientific Inc., Waltham, Massachusetts, USA), ranging from 4000 to 4000 cm⁻¹. -1 Light absorption and reflectance spectra were collected on an Agilent Cary 7000 UV-Vis-NIR spectrophotometer.

[0053] Ice adhesion strength test

[0054] The adhesion strength of ice was analyzed by measuring the shear strength required to remove ice from the coating using a force gauge. Initially, water was placed in a 2.0cm × 2.0cm × 2.0cm mold and frozen into ice cubes. The ice cubes were then placed on the coating surface and placed in a freezer at -15°C for 12 hours.

[0055] Anti-icing performance test

[0056] Static anti-icing performance was evaluated by measuring water droplet freezing time at an ambient humidity of 30±2%. First, bare and coated aluminum plates were placed on pre-prepared ice blocks at -15°C to simulate a cold environment. Then, 50 μL of water was dropped onto the coated surface, and the crystallization process was studied using a digital microscope. The time it took for the water droplet to transform from the liquid phase to the solid phase was defined as the freezing time.

[0057] Dynamic anti-icing tests were conducted in a high and low temperature / humidity test chamber under ambient humidity conditions of 30±2%. Initially, bare and coated aluminum sheets were placed at a 5° tilt angle, and 1 mL of water droplets formed on the surface. Subsequently, the chamber was cooled from 0°C for every 10°C decrease until the temperature reached -70°C, and held for 30 minutes to ensure that the water droplets completely transformed into ice. The ice at each temperature was weighed for comparison.

[0058] Photothermal de-icing performance test

[0059] Under simulated sunlight exposure at an ambient temperature of 25±2℃ and relative humidity of 30±2%, the photothermal de-icing performance was evaluated by measuring the time it took for ice blocks to slide off the surface, placed 14cm directly above the substrate. (1.0kW / m²) 2 The simulated sunlight intensity was generated by a xenon lamp (PLS-SXE300 / 300UV). Infrared imaging thermometers were used to assess surface temperature changes.

[0060] Mechanical durability test

[0061] The abrasion resistance of the coating was evaluated using a Taber abrasion tester under a 250g load. The sample was first sprayed onto a 10cm diameter glass substrate and then fixed on a rotating platform. The rotation speed was set to 79 rpm / min. WCA and WRA were recorded after every 20 cycles.

[0062] The surface adhesion of the coating to various substrates was measured using an XH-M adhesion tester. Furthermore, the adhesion was further measured using a tape test according to ASTM D3359. Prior to this, samples were vertically cut into 1mm pieces using a cross-cut adhesion tester. 2 100 squares were made, then compressed with 3M tape under a 2kg load, and then peeled off to observe the peeling.

[0063] For the tape peel test, apply 3M tape to the coated surface and press firmly with your thumb. Then, roll a 750-gram weight over the surface to ensure good contact with the coating, and then peel off the tape from one end. Repeat the above process, recording the corresponding WCA and WRA after every 50 cycles, and replacing the tape after every 10 cycles.

[0064] Chemical stability, self-cleaning and corrosion resistance tests

[0065] The coated glass plates were immersed in HCl solution (pH=1), NaOH solution (pH=14), NaCl solution (0.1M), and various organic solvents (e.g., DMF, THF, DMSO, acetone). Every six days, the samples were removed, cleaned, and dried to measure WCA and WRA.

[0066] To examine the self-cleaning properties of the samples, sand was used to simulate contaminants. A glass substrate (25mm × 75mm) was tilted in the petri dish and covered with sand in a random pattern.

[0067] The corrosion resistance of the coating was evaluated using a copper accelerated acetic acid spray test (CASS) in a salt spray chamber. Acetic acid was added to a 5 wt% NaCl solution to adjust the pH of the corrosion solution to 2-3, and anhydrous CuCl2 was used to coat the Cu coating. 2+ Adjust the concentration to 0.26 g / L. -1 The temperature and humidity inside the chamber were set to 35°C and 95%, respectively, while the spray rate was maintained at 1.5 mL / h. -1 cm -2 .

[0068] Electrochemical tests were performed on an electrochemical analyzer (CHI 660E, Shanghai Chenhua) using a standard three-electrode system, including a platinum sheet as the counter electrode, a saturated calomel electrode (SCE) as the reference electrode, and a coated aluminum sheet (6cm × 6cm) as the working electrode. Electrochemical impedance spectroscopy (EIS) was performed in 5.0 wt% NaCl solution at a frequency of 0.1 Hz to 10 Hz. 6 The open-circuit potential in the Hz range was measured with an amplitude of 20 mV. The Tafel curve was measured in a 5.0 wt% NaCl solution at a scan rate of 10 mV / s.

[0069] Example 4

[0070] Coating preparation process

[0071] Figure 1The synthesis process of the superhydrophobic photothermal coating is demonstrated. First, SiO2 microspheres and TiN nanoparticles were chemically modified using KH-570 via a hydrolysis-condensation reaction. The hydrolysis products of KH-570 in an acidic medium react with the hydroxyl groups on the surface of SiO2 microspheres and TiN nanoparticles to form alkylated particles. Subsequently, using AIBN as an initiator, the superhydrophobic alkyl groups of SMA were branched to the particle surface via a double-bond polymerization reaction. Surface roughness and low surface energy are two key factors for superhydrophobicity; generally, larger surface roughness and lower surface energy are beneficial for obtaining higher superhydrophobicity. By combining micron-sized and nano-sized particles, suitable roughness can be obtained, thereby creating a superhydrophobic surface. In this work, SiO2 microspheres and TiN nanoparticles can form a hierarchical rough structure to provide surface roughness, and the chemical modification of SMA can reduce the particle surface energy. During the synthesis of E-51-based adhesive, the amino group of KH-550 can react with the epoxy group of E-51 through the ring-opening reaction between E-51 and KH-550, thereby enhancing the adhesion between the E-51 layer and the modified particles. Subsequently, coatings of modified particles and E-51-based adhesive in different proportions are sequentially sprayed onto a glass substrate, with the upper and lower layers consisting mainly of modified particles and E-51-based adhesive, respectively.

[0072] Structure and composition characterization of coatings

[0073] XPS spectroscopy was used to analyze the surface composition of the original particles, KH-570 alkylated particles, and KH-570 and SMA modified particles. All XPS spectra showed distinct C1s, O 1s, N 1s, Si 2p, and Ti 2p signals. Figure 2 a) After hydrolysis and polycondensation with KH-570, the surface O atom ratio increased from 36.7% to 42.1%. Simultaneously, due to the long alkyl groups in SMA, the C atom ratio increased significantly from 31.2% to 89.5%. Figure 2 b shows the high-resolution C1s spectra of the three samples. All C1s spectra were fitted to three peaks assigned to the -CC-, -CO-, and -C=O bonds. The -CC- bonds originated from the carbon chains or alkyl groups in KH-570 and SMA, while the -CO- and -C=O bonds originated from the ester groups in KH-570 and SMA. Compared to the original particles, the percentage of the -C=O peak in the alkylated particles was slightly increased, while the percentage of the -CC- peak further increased from 64.3% to 88.4% after grafting SMA. The surface chemical state of the modified particles was further analyzed by XPS. Figure 3The high-resolution N1s XPS spectrum was decomposed into two peaks associated with N-Ti bonds (397.0 eV) and N-Ti-O bonds (395.8 eV), respectively. The high-resolution Si 2p spectrum was associated with Si-O and Si-C bonds, respectively, indicating the presence of SiO2 microspheres and KH-570. The high-resolution Ti 2p XPS spectrum of the modified particles was divided into two doublets (Ti 2p...). 1 / 2 and Ti 2p 3 / 2 The peaks at 463.7 eV and 458.2 eV are attributed to Ti-O bonds, while the peaks at 462.0 eV and 456.7 eV are attributed to Ti-NO bonds, and the peaks at 460.4 eV and 455.2 eV are attributed to Ti-N bonds. Furthermore, O-Ti and O-Si bonds appear in the high-resolution O1s XPS spectrum. These results confirm the successful modification of TiN and SiO2 particles by KH-570 and SMA.

[0074] Figure 4 SEM images and elemental distribution images of the superhydrophobic coating are shown. The coating exhibits a rough texture with a hierarchical micro / nano structure. Abundant grains are formed due to the aggregation of TiN nanoparticles. Furthermore, numerous voids exist between the SiO2 microspheres and the TiN nanoscale aggregates, providing ample space for air trapping and thus endowing the coating with high superhydrophobicity. High-magnification SEM images reveal the presence of TiN nanoparticles on the surface of the SiO2 microspheres. This structure further improves surface roughness, resulting in superhydrophobicity. Elemental distribution images of Ti and Si confirm the presence of SiO2 and TiN particles. Cross-sectional SEM images clearly show the boundary between the two layers, with the upper layer being rougher and dominated by particle aggregates, while the flat lower layer is mainly composed of E-51-based binder. The Ti elemental distribution image shows that, due to the high TiN content, Ti is mainly concentrated in the top layer, creating a stark contrast with the lower layer.

[0075] Particle content and ratio optimization

[0076] The surface wettability of the coating was evaluated by measuring the water droplet wettability coefficient (WCA) and wettability coefficient (WRA). To investigate the effect of particle content on superhydrophobicity, WCA and WRA were measured at particle contents of 3.4 wt%, 9.7 wt%, 15.1 wt%, and 20.0 wt%. The results showed that WCA initially increased, reaching a maximum of 159.1° when the particle percentage was 15.1 wt%. Subsequently, WCA decreased with increasing particle mass ratio. Figure 5As shown, when the particle content is below 15.1 wt%, water droplets easily adhere and cannot roll off the surface. When the particle percentage is 3.4 wt%, the coating has a low WCA of 97°, indicating poor hydrophobicity due to low surface roughness. When the particle content is 15.1 wt%, the coating exhibits strong superhydrophobicity, with a maximum WCA of 159.1° and a minimum WRA of 1.2°. Then, different SiO2 to TiN particle mass ratios (m...) were explored. SiO2 / m TiN The coatings of WCA and WRA. When m SiO2 / m TiN When varying within the range of 1 / 1 to 3 / 1, all coatings exhibited strong hydrophobicity, with a WCA exceeding 140°. Wherein, m SiO2 / m TiN When the particle content is 3 / 2, the WCA reaches its maximum of 159.1° and the WRA is its minimum of 1.2°, while water droplets easily slide off the coating. When the mSiO2 / mTiN ratio is below or above 3 / 2, the WCA decreases while the WRA increases. These differences in the coating mainly stem from changes in the surface micro / nanoporous structure. The above results demonstrate that a particle content of 15.1 wt% and m... SiO2 / m TiN A ratio of 3 / 2 is the best choice for superhydrophobicity.

[0077] Superhydrophobicity of the coating

[0078] Besides water droplets, droplets from HCl solution (pH=1.0), NaOH solution (pH=14.0), NaCl solution (0.1M), tea, coffee, and milk also exhibited near-perfect spherical shapes. Furthermore, all liquids remained superhydrophobic, with a WCA greater than 150° and a WRA less than 5°. Figure 6 a) indicates that the synthesized coating exhibits excellent repellency to various liquids. High-speed camera footage shows that water droplets can easily bounce off the coated glass surface. Figure 6 b).

[0079] Anti-icing performance of the coating

[0080] To evaluate the passive anti-icing performance of the coating, the icing process of a 50 μL water droplet on bare aluminum and coated aluminum sheets at -15℃ was studied using a digital magnifying glass. Figure 7As can be seen, when water droplets fall on bare aluminum sheets, they spread across the surface. Initially, the droplets are transparent, but ice grows upwards after condensation. As the droplets begin to freeze, the surface becomes opaque due to the difference in reflectivity between water and ice. For bare aluminum sheets, the droplets appear turbid after 20 seconds due to ice nucleation. Thereafter, solid and liquid phases coexist until the droplets are completely frozen after 47 seconds. In contrast, water droplets on coated aluminum sheets are nearly spherical. The coated aluminum sheets begin to freeze after 40 seconds and are not completely frozen until 170 seconds. As expected, the freezing time is effectively extended by 3.6 times, demonstrating the coating's excellent anti-icing ability. The relatively rapid freezing time on bare aluminum sheets is due to the direct freezing process from bottom to top at the solid-liquid interface. For coated aluminum sheets, the rough structure traps an air layer between the droplets and the surface, reducing the solid-liquid contact area and hindering heat transfer, thus delaying ice crystallization at the solid-liquid interface.

[0081] To determine the adhesion of the resulting coating, ice was pre-formed on an aluminum plate in a freezer at -15°C, and the adhesion strength of the ice was measured using a tensiometer at 5°C. Figure 8 The ice adhesion on the bare aluminum sheet reached 660 kPa, almost twice that of the coated aluminum sheet (355 kPa). For the coated aluminum sheet, the required force dropped to zero after 240 seconds, meaning the ice completely detached. In contrast, the ice on the bare aluminum sheet, due to its stronger adhesion, was more difficult to remove, requiring approximately 300 seconds to be completely removed. It is speculated that the air gap between the micro / nano structure and the water droplet significantly weakens the adhesion strength of the ice-solid interface.

[0082] De-icing performance of the coating

[0083] Photothermal conversion is crucial for de-icing performance. For example... Figure 4 As shown, compared to bare glass and glass coated only with SiO2 microspheres, the glass with a superhydrophobic coating exhibits up to 90% light absorption in the 300-2600 nm wavelength range. Similarly, due to the addition of TiN nanoparticles, the light reflectivity is significantly reduced to 5%. Figure 9 Therefore, the addition of TiN nanoparticles can significantly suppress light reflectivity and improve light absorption. The high light absorption of TiN nanoparticles is beneficial for improving photothermal conversion efficiency, enabling rapid heating and thus promoting de-icing. The photothermal effect of the synthesized coating was evaluated using an infrared imaging device by observing changes in surface temperature. Figure 10 a). It can be observed that under xenon lamp irradiation, the surface temperature of the coated aluminum plate can reach 133.8℃ within 5 minutes, while the bare aluminum plate can only rise to 70.0℃. Using glass as a substrate, the surface temperature can reach 118℃ within 6.0 minutes, while the bare glass can only reach 92℃. Figure 10b). The above phenomena confirm that the obtained coating has high photothermal conversion efficiency. To elucidate the key influencing factors of the photothermal effect, the temperature difference between coated glass and bare glass with different mass ratios of TiN nanoparticles was used ( Figure 10 c). As the TiN mass ratio increased from 0 to 33 wt%, the temperature rise of the glass substrate increased accordingly after 5.0 minutes, indicating that TiN plays a crucial role in maintaining surface temperature. Under xenon lamp irradiation, the coating rapidly heated up due to the photothermal effect of TiN. Ice adhesion decreased, and the ice layer at the ice-solid interface melted first, causing the ice to slide off. Over time, heat was transferred to the surrounding ice, melting the entire block.

[0084] To simulate the photothermal de-icing effect of the coating, an actual de-icing experiment was conducted in Jinan, China, at an outdoor temperature of 0℃. Prior to the experiment, ice blocks measuring 2.0cm × 2.0cm × 2.0cm were prepared using a template. Four ice blocks were frozen onto the surfaces of both the coated and bare glass substrates. The melting state of the ice blocks was studied, and the melting time was recorded. Under solar irradiation, due to the excellent thermal conductivity of TiN nanoparticles, the ice at the ice-solid interface on the coated glass began to melt at 6.5 min, and significant sliding was observed at 6.67 min. Heat was transferred from the photothermal zone to the surrounding coating, resulting in complete melting. In contrast, the ice blocks did not detach from the bare glass until 10 min. Figure 11 ).

[0085] Coating stability

[0086] The chemical stability of superhydrophobic coatings plays a crucial role in practical applications. Therefore, the chemical stability of the obtained coatings in various harsh environments was tested. Figure 12 As shown, after immersion in strong acid / base solutions (e.g., HCl solution (pH=1.0), NaOH solution (pH=14.0)), organic solvents (e.g., DMF, acetone, THF, and DMSO), and NaCl solution (0.1M) for 30 days, the coating retains its superhydrophobicity at WCA exceeding 150°, indicating excellent chemical stability. This high chemical stability of the superhydrophobic coating is likely due to its good chemical inertness and structural stability.

[0087] Besides chemical stability, mechanical robustness also significantly impacts coating life. Abrasion resistance testing was conducted using a Taber abrasion tester under a 250g load. WCA and WRA were measured after every 20 cycles. Figure 13 As shown, after 180 wear cycles, the coating still maintains strong superhydrophobicity, with WCA above 150° and WRA below 10°. These tests demonstrate that the superhydrophobic coating possesses good mechanical strength.

[0088] To evaluate the adhesion and mechanical stability between the coating and the substrate, a tape peel test was conducted. In this test, the coating was vertically cut into 100 1 mm sections using a mesh cutter. 2 The cube was then compressed with 3M tape under a 2 kg load, and then peeled off to observe the peeling. Figure 5 Optical photographs of only the top and both coating layers after the tape peel test are shown. It can be seen that the top coating exhibits severe surface peeling due to weak adhesion, while no obvious structural damage was observed in the two coating layers. Furthermore, the adhesion of the coatings to various substrates (including copper plates, wood, aluminum plates, and glass) was measured using an adhesion tester. Figure 14 (a) This is crucial for expanding practical applications. In particular, the adhesion to glass substrates can reach 8.8 MPa ( Figure 14 (b) This means that the coating has a strong bond with the substrate.

[0089] This embodiment further tests the durability of the superhydrophobic coating through a freezing / thawing cycle. A water droplet (5 μL) freezing experiment was conducted in a freezer at -15°C for 30 minutes, followed by heating the coating with the frozen droplet in an oven at 120°C for 30 minutes to melt the droplet. This process is referred to as one freezing / thawing cycle. Figure 15 As shown, WCA and WRA were recorded every 50 cycles. Even after 500 freezing / thawing cycles, the coating still exhibited strong superhydrophobicity, with WCA at 163.5° and WRA at 3.7°, indicating that the coating has excellent anti-icing / de-icing performance.

[0090] Self-cleaning properties of the coating

[0091] Considering the practical applications of the coating, self-cleaning effect is a crucial characteristic for reducing contamination in superhydrophobic materials. Contaminants adhere much less to the coating surface, and water flow can easily remove them. In the testing process, sand was used to simulate contaminants. A glass substrate (25mm × 75mm) was tilted in a petri dish and covered with sand. Figure 16 As can be seen, when water droplets fall vertically onto the coating surface, the water can easily roll off the glass surface containing sand, indicating that the synthesized coating has significant self-cleaning properties.

[0092] Corrosion resistance of coating

[0093] Cu was tested using a salt spray test chamber. 2+ Accelerated acetic acid spray testing was used to evaluate the corrosion resistance of the coating. The corrosion solution consisted of 5.0 wt% CuCl2 and 0.26 g L... -1A mixture of NaCl was used. After 300 hours, the exposed copper sheet was severely etched, and its surface structure was almost completely destroyed. For comparison, only a small amount of CuCl2 was deposited on the coated copper sheet. Figure 17 a) Thanks to the protection of the superhydrophobic coating, the copper sheet was well protected and suffered almost no damage. Figure 17 b shows the Tafel plots of bare copper and coated copper plates at different corrosion times. Corrosion potential (E) corr ) and corrosion current density (I corr The corrosion potential (E) can be determined by extrapolation. It is generally believed that a higher corrosion potential is associated with a lower corrosion probability, and a lower corrosion current density is associated with a slower corrosion rate. Clearly, as the exposure time to a corrosive environment increases, the E of bare copper and coated copper plates... corr and I corr Both decreased compared to pre-exposure levels. After 300 hours, the E of the bare copper plate... corr The voltage shifted negatively from -0.572V to -0.880V, while the E of the coated copper plate... corr The value is -0.162V. Therefore, the I of bare copper and coated copper plates... corr The decrease was 1.52 × 10⁻⁶. -4 A and 6.28×10 -8 A. I of superhydrophobic surfaces corr Approximately four orders of magnitude smaller. E corr The increase and I corr The reduction in corrosion resistance indicates that superhydrophobic coatings can effectively enhance the corrosion resistance of copper substrates. The excellent corrosion resistance of the synthetic coating mainly stems from the following factors. First, the air gaps trapped in the rough surface structure prevent the coating from being penetrated by corrosive solutions. Furthermore, the air gaps can repel corrosive ions into the coating through Laplace pressure. More importantly, the robust structure and compositional stability of the coating protect the copper substrate from corrosion.

[0094] In addition to the Tafel curves, the corrosion resistance of the coating was further analyzed using EIS. Figure 18 The evolution of Nyquist plots for bare copper and coated copper plates under different corrosion times is shown. Generally, the larger the radius of the semicircle, the better the corrosion resistance. After 300 hours of corrosion testing, the coated copper plate still exhibits the highest impedance value of 272.4 Ωcm. -2 Compared to bare copper sheet (0.25Ωcm) -2 The difference is two orders of magnitude higher, demonstrating its excellent corrosion resistance.

Claims

1. A fluorine-free, superhydrophobic micro / nanostructured SiO2 / TiN anti-icing and photothermal de-icing coating, characterized in that, The coating is prepared by the following method: Step 1: Under magnetic stirring, TiN nanospheres and SiO2 microspheres were dispersed in a mixture of 3-(isobutenoyloxy)propyltrimethoxysilane KH-570, ethanol and H2O, and the pH was adjusted to 4.0-5.0 with acetic acid to obtain a mixture. Step 2: The mixture obtained in Step 1 is reacted at 60°C for 2.0 hours with stirring. The above solution is purified by centrifugation and washed with ethanol. Step 3: The product obtained in Step 2 is dispersed in ethanol, and then mixed with octadecyl methacrylate (SMA) and 2,2'-azobisisobutyronitrile (AIBN). The polymerization process is carried out at 60°C with stirring for 2.0 h to obtain modified particles. Step 4: Photothermal superhydrophobic coatings were prepared by using modified particles in different proportions and E-51-based adhesives through a two-step spraying technique.

2. The coating according to claim 1, characterized in that, In step one, the mass of TiN nanospheres is 3.0 g, the mass of SiO2 microspheres is 2.0 g, the volume of 3-(isobutenoyloxy)propyltrimethoxysilane KH-570 is 5.0 mL, the volume of ethanol is 22.0 mL, and the volume of H2O is 2.0 mL.

3. The coating according to claim 1, characterized in that, In step three, the volume of ethanol is 20.0 mL, the volume of octadecyl methacrylate (SMA) is 3.0 mL, and the mass of 2,2'-azobisisobutyronitrile (AIBN) is 0.05 g.

4. The coating according to claim 1, characterized in that, In step four, the photothermal superhydrophobic coating is prepared as follows: First, the modified particles, ethanol, and E-51-based adhesive are mixed and stirred for 5 minutes to form a homogeneous solution; then, the above solution is sprayed onto a glass substrate and cured at 80°C for 3.0 minutes. Next, a homogeneous mixture of 0.066g of E-51-based adhesive and 3.0mL of modified particles is sprayed onto the coating surface a second time and cured at 120°C for 6.0 hours.

5. The coating according to claim 4, characterized in that, The modified particles were 0.9 mL, the ethanol was 2.1 mL, and the E-51-based binder was 0.972 g.

6. The coating according to claim 4, characterized in that, The modified particles have a particle content of 15.1 wt% and a particle size of m. SiO2 / m TiN It has a ratio of 3 / 2, making it the best in terms of superhydrophobicity.

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