Rodlike carbon nitride-polydimethylsiloxane composite coating as well as preparation method and application thereof

Abstract

The invention discloses a rodlike carbon nitride-polydimethylsiloxane composite coating and a preparation method and application thereof.The rodlike carbon nitride-polydimethylsiloxane composite coating is prepared by mixing rodlike carbon nitride filler, polydimethylsiloxane and a curing agent, and even doping of the rodlike carbon nitride filler can effectively improve the crosslinking density of the composite coating; the adhesive force and the tensile strength of the coating are enhanced; when the composite coating is applied to the surface of a matrix, a multifunctional nano coating with mechanical reinforcement, long-acting corrosion prevention and microbial antifouling characteristics can be formed, the impedance arc radius is kept at 5.17 * 10 < 9 > omega.cm < 2 > after the composite coating is soaked for 60 days, and the composite coating shows excellent bacteriostasis and sterilization performance on chlorella and escherichia coli; the excellent biological pollution prevention characteristic is shown.

Description

Technical Field

[0001] This invention relates to a composite coating, particularly to a rod-shaped carbon nitride-polydimethylsiloxane composite coating, and also to the preparation method and application of the above-mentioned composite coating. Background Technology

[0002] Globally, metal corrosion, as a persistent and pervasive form of material degradation, causes approximately $2.5 trillion in economic losses annually, accounting for 3-4% of total annual output. This poses a serious threat to the safety and reliability of industrial facilities and has long limited energy consumption and resource utilization efficiency. Traditional corrosion protection technologies, represented by chromate coatings, offer relatively durable protection, but their potent carcinogenicity and inherent environmental toxicity severely restrict their application under the dual requirements of modern green manufacturing and sustainable development. Therefore, against the backdrop of escalating energy shortages and increasing environmental pollution, developing efficient, environmentally friendly, and sustainable metal protection technologies has become an urgent priority in the field of corrosion protection. Photocatalytic cathodic protection technology, as an innovative strategy for metal protection using clean solar energy, utilizes the band structure of semiconductor materials to generate and transport photogenerated electrons to the metal substrate under irradiation, thereby inducing cathodic polarization on the metal surface and inhibiting anodic dissolution reactions. The core challenge in this system lies in selecting semiconductor materials with suitable bandgap structures and excellent charge mobility, which can utilize their photogenerated carrier transport behavior to provide a stable and continuous electron supply to the metal substrate. Incorporating these materials as functional fillers into the coating matrix not only significantly enhances the barrier and shielding effectiveness of the coating, but also further improves the active protection performance of the coating in corrosive environments by generating electrons through cathode injection of light.

[0003] Carbon nitride (g-C3N4) is widely considered an ideal candidate for photocatalytic cathodic protection due to its non-toxicity, non-metallic properties, ease of preparation, excellent chemical stability, and suitable band gap. Its two-dimensional layered structure generates a "maze effect," effectively delaying the diffusion of corrosive media within the coating. Simultaneously, the migration of photogenerated carriers on the metal surface further enhances the cathodic polarization effect, thus synergistically achieving physical barrier protection and chemical shielding. However, bulk g-C3N4 still faces inherent limitations, such as low specific surface area, high charge recombination rate, and limited active sites, severely restricting its practical application performance in complex corrosion systems. Existing technologies employ methods such as controlling the morphology and structure of g-C3N4 to overcome these limitations, including ultrathin nanosheets, porous g-C3N4, and quantum dot doping. However, ultrathin nanosheets are prone to interlayer recombination and agglomeration due to their structural characteristics, resulting in a reduction in actual specific surface area and active sites, and limited enhancement of the overall mechanical properties of the coating. The layered stacking structure is susceptible to severe agglomeration during spontaneous stacking, obscuring numerous edge and defect active sites. The internal interlayer spacing often exhibits a random and uncontrollable disordered arrangement. This structural heterogeneity inevitably provides local channels for the penetration of corrosive ions, significantly weakening the expected barrier effect. Quantum dots, on the other hand, are extremely small in size, making dispersion control difficult, and cannot enhance the physical barrier effect. Porous g-C3N4 achieves a high exposed specific surface area at the expense of material mechanical strength; its excessive pores become rapid channels for corrosive media penetration, preventing more stable and durable corrosion protection. Therefore, there is an urgent need to develop new composite coatings to overcome the technical problems of the existing technologies. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a low-cost, long-lasting, corrosion-resistant, antibacterial, and antifouling rod-shaped carbon nitride-polydimethylsiloxane composite coating; the second purpose is to provide a method for preparing the above-mentioned composite coating; and the third purpose is to provide applications of the above-mentioned composite coating.

[0005] Technical solution: The rod-shaped carbon nitride-polydimethylsiloxane composite coating of the present invention comprises rod-shaped carbon nitride filler, polydimethylsiloxane and curing agent mixed together; the mass ratio of the rod-shaped carbon nitride filler, polydimethylsiloxane and curing agent is 0.019~0.021:10:0.98~1.02.

[0006] The rod-shaped carbon nitride is a g-C3N4 rod-shaped structure with a layered arrangement, and an overall length of about 50~100 μm. The interior exhibits a dense layered stacked structure. The sample is synthesized directly by a two-step method of hydrothermal treatment followed by calcination. First, melamine and water are subjected to a hydrothermal reaction, with a mass ratio of water to melamine of 15:1~1.02. Then, the washed and dried hydrothermal precursor is placed in a muffle furnace for high-temperature calcination at a heating rate of 1~3℃ / min, a holding temperature of 520~550℃, and a holding time of 1.5~3h.

[0007] The rod-shaped carbon nitride filler has a complete rod-shaped form, and the composite coating uses polydimethylsiloxane as the polymer matrix, with the rod-shaped carbon nitride filler uniformly dispersed in the polymer matrix.

[0008] The method for preparing the above-mentioned rod-shaped carbon nitride-polydimethylsiloxane composite coating includes the following steps:

[0009] (1) Dissolve melamine in deionized water and stir;

[0010] (2) The obtained solution was placed in a reaction vessel for hydrothermal treatment to obtain a rod-shaped precursor;

[0011] (3) The precursor was washed and dried several times and then calcined in a muffle furnace to obtain rod-shaped carbon nitride filler.

[0012] (4) Disperse the rod-shaped carbon nitride filler into polydimethylsiloxane and curing agent, and stir to obtain rod-shaped carbon nitride-polydimethylsiloxane composite coating.

[0013] In step (1), the stirring time is 25-35 minutes, the stirring temperature is room temperature, and the stirring speed is 600-800 r / min.

[0014] In step (2), the hydrothermal treatment has a heat preservation temperature of 180~200 ℃ and a heat preservation time of 11~13h.

[0015] In step (3), the calcination process involves a heating rate of 1~3℃ / min, a holding temperature of 520~550℃, and a holding time of 1.5~3h.

[0016] In step (4), the mass ratio of the rod-shaped carbon nitride filler, polydimethylsiloxane and curing agent is 0.019~0.021: 9.25~10.75: 0.95~1.05. The mixture is stirred evenly for 10~30 min. The curing agent is Dow Corning 184 curing agent.

[0017] The aforementioned rod-shaped carbon nitride-polydimethylsiloxane composite coating can be used in anti-corrosion, antibacterial, and antifouling coatings.

[0018] The specific application involves applying rod-shaped carbon nitride-polydimethylsiloxane composite coating to the surface of a carbon steel substrate using a spin coater to form a composite coating with a thickness of 30-80 μm. The coating process specifically involves first applying the coating at a low speed (300-600 r / min) for 1-2 minutes, followed by a high-speed spin coat for 3-5 minutes (1200-1500 r / min).

[0019] Invention Principle: The rod-shaped carbon nitride-polydimethylsiloxane composite coating of the present invention uses rod-shaped carbon nitride obtained by thermal polymerization of melamine and water as raw materials to obtain a composite filler with a rod-shaped structure. Through a two-step simplified synthesis process, g-C3N4 is innovatively designed into a rod-shaped structure with a layered arrangement, which naturally realizes the self-assembly and integration of ultra-thin sheets. Subsequently, the rod-shaped g-C3N4 (RCN) is mixed with the polydimethylsiloxane (PDMS) matrix to finally form a multifunctional nanocomposite coating (RCN / PDMS) that has mechanical reinforcement, long-term corrosion resistance and protection against microbial contamination.

[0020] Specifically, compared to morphology modification strategies that solely pursue ultra-high specific surface area, extreme charge separation, or abundant pores, this study designs a rod-shaped g-C3N4 nanostructure with oriented nanosheets, aiming to achieve a dual innovation of "structural integration and functional synergy." By controlling the ordered distribution of the lamellar spaces within the rod-shaped structure, interlayer aggregation is suppressed, and the rod-shaped carbon nitride and PDMS polymer matrix achieve a tight mechanical interlock, thus providing a larger specific contact surface. Simultaneously, the increased number of contact sites significantly enhances the mechanical interlock and adhesion between the coating and the metal substrate. The highly internally stacked rod-shaped structure provides a superior physical barrier for metal protection, blocking corrosive media from passing through tortuous paths and enhancing mechanical stability. More importantly, the highly exposed active edges and defects provide enhanced surface activity and chemical protection, adsorbing corrosion factors and promoting interfacial stability. Meanwhile, RCN exhibits stronger carrier excitation characteristics under light conditions, generating more photogenerated electrons and cathode injection, thereby achieving cathodic polarization protection of the metal substrate. The synergistic effect of these two combined provides strong support for durable protection against metal corrosion. In addition, the RCN / PDMS composite coating can also generate active ROS, and its strong redox properties under light conditions can directly and efficiently inhibit microbial activity, thereby achieving antifouling performance against bacteria and algae.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0022] (1) The composite coating of the present invention has excellent corrosion resistance. The coating formed on the surface of a carbon steel substrate has an EIS impedance radius of 5.17 × 10⁻⁶ after immersion for 60 days. 9 Ω·cm2 Compared to other coatings, its impedance arc radius is increased by two orders of magnitude; and after a 60-day corrosion immersion test, no corrosion spots appeared on the coating surface, demonstrating its long-lasting and stable corrosion resistance.

[0023] (2) The mechanical properties of the composite coating of the present invention are significantly improved compared with the pure phase PDMS coating, including the adhesion and tensile strength (1.795 MPa).

[0024] (3) Comparing the anti-biofouling performance of PDMS, BCN / PDMS and RCN / PDMS coatings, RCN / PDMS coating showed 94.2% inhibition of Escherichia coli activity and 96.5% inhibition of Staphylococcus aureus activity, and its performance in inhibiting Chlorella activity was more outstanding. Attached Figure Description

[0025] Figure 1 The images show scanning electron microscope (SEM) and transmission electron microscope (TEM) images of Comparative Example 2 BCN and all Examples RCN-X (X=1, 2, 3). Figure a1 is the SEM image of BCN, Figures a2-a3 are the TEM images of BCN, Figure b1 is the SEM image of RCN-1, Figures b2-b3 are the TEM images of RCN-1, Figure c1 is the SEM image of RCN-2, Figures c2-c3 are the TEM images of RCN-2, Figure d1 is the SEM image of RCN-3, and Figures d2-d3 are the TEM images of RCN-3.

[0026] Figure 2 The Fourier transform infrared (FT-IR) spectra of Comparative Example 2 BCN and all Examples RCN-X (X=1, 2, 3) are shown.

[0027] Figure 3 The X-ray photoelectron spectroscopy (XPS) analysis of Comparative Example 2 BCN and Example 2 RCN-2 is shown in Figure a. The full spectrum comparison is shown in Figure a. Figures b, c and d are images of the C 1s, N 1s and O 1s regions, respectively.

[0028] Figure 4 Cross-sectional scanning electron microscope (SEM) images of the coatings of Comparative Example 1 PDMS, Comparative Example 2 BCN / PDMS and Example 2 RCN-2 / PDMS.

[0029] Figure 5 This is a comparison chart of adhesion test results for all embodiments and all comparative examples of coatings;

[0030] Figure 6Electrochemical corrosion protection performance of all examples and all comparative examples was characterized under 3.5 wt% sodium chloride solution conditions for different soaking times (1, 20, 40 and 60 days). Figures a, b, c and d are Nyquist plots, figures e, f, g and h are Bode plots, and figures i, j, k and l are phase angle plots.

[0031] Figure 7 Optical images of the coatings in all embodiments and all comparative examples after 72 hours of salt spray testing;

[0032] Figure 8 Scanning electron microscope (SEM) images and EDS mapping images of the corrosion surface morphology of the coatings of Comparative Example 1 PDMS, Comparative Example 2 BCN / PDMS, and Example 2 RCN-2 / PDMS.

[0033] Figure 9 Figures show the antibacterial and antifouling experimental analysis of the coatings of Comparative Example 1 (PDMS), Comparative Example 2 (BCN / PDMS), and Example 2 (RNC-2 / PDMS): Figure ac shows the comparison of the adhesion of Chlorella to the coating surface; Figure d1 shows the colony image of Escherichia coli after 72 hours of cultivation in the coating; Figure d2 shows the colony image of Staphylococcus aureus after 72 hours of cultivation in the coating.

[0034] Figure 10 Figure a shows the electron spin resonance (ESR) spectra of the BCN / PDMS coating in Comparative Example 2 and the RCN-2 / PDMS coating in Example 2. Figure a also shows the hydroxyl radicals (·OH) and superoxide radicals (·O2) of the BCN / PDMS coating. − The signal, Figure b shows the hydroxyl radicals (·OH) and superoxide radicals (·O2) of the RCN-2 / PDMS coating. − )Signal; Detailed Implementation

[0035] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0036] Example 1

[0037] (1) Preparation of rod-shaped carbon nitride composite RCN-1: 2 g of melamine was dispersed in 30 mL of deionized water and stirred at 600 r / min for 30 min. Then, it was placed in a 50 mL reaction vessel and stored at a heating temperature of 200 ℃ / min for 12 hours. The precipitate was washed several times with deionized water and then dried in a vacuum drying oven at 60 ℃. The obtained precursor material was placed in a 50 mL crucible and heated in a muffle furnace at a heating rate of 1 ℃ / min from room temperature to 550 ℃. Then, it was kept isothermally for 2 hours. The obtained sample was then collected for later use and labeled as RCN-1.

[0038] (2) Preparation of rod-shaped carbon nitride RCN-1-polydimethylsiloxane composite coating: Take 10g of polydimethylsiloxane and 1.0g of Dow Corning 184 curing agent, stir for 10~20min until completely uniform; then add 30mg of RCN-1, and continue stirring for 30min to obtain the composite coating;

[0039] The coating was applied to a carbon steel surface using a spin coater, dried at room temperature for 24 hours, and then cured at 60 °C for 12 hours. The resulting coating sample was labeled RCN-1 / PDMS.

[0040] Example 2

[0041] (1) Preparation of rod-shaped carbon nitride composite RCN-2: 2 g of melamine was dispersed in 30 mL of deionized water and stirred at 600 r / min for 30 min. Then, it was placed in a 50 mL reaction vessel and stored at a heating temperature of 200 ℃ / min for 12 hours. The precipitate was washed several times with deionized water and then dried in a vacuum drying oven at 60 ℃. The obtained precursor material was placed in a 50 mL crucible and heated in a muffle furnace at a heating rate of 2 ℃ / min from room temperature to 550 ℃. Then, it was kept isothermally for 2 hours. The obtained sample was then collected for later use and labeled as RCN-2.

[0042] (2) Preparation of rod-shaped carbon nitride RCN-2-polydimethylsiloxane composite coating: Take 10g of polydimethylsiloxane and 1.0g of Dow Corning 184 curing agent, stir for 10~20min until completely uniform; then add 30mg of RCN-2, and continue stirring for 30min to obtain the composite coating;

[0043] The coating was applied to a carbon steel surface using a spin coater, dried at room temperature for 24 hours, and then cured at 60 °C for 12 hours. The resulting coating sample was labeled RCN-2 / PDMS.

[0044] Example 3

[0045] (1) Preparation of rod-shaped carbon nitride composite RCN-3: 2 g of melamine was dispersed in 30 mL of deionized water and stirred at 600 r / min for 30 min. Then, it was placed in a 50 mL reaction vessel and stored at a heating temperature of 200 ℃ / min for 12 hours. The precipitate was washed several times with deionized water and then dried in a vacuum drying oven at 60 ℃. The obtained precursor material was placed in a 50 mL crucible and heated in a muffle furnace at a heating rate of 3 ℃ / min from room temperature to 550 ℃. Then, it was kept isothermally for 2 hours. The obtained sample was then collected for later use and labeled as RCN-3.

[0046] (2) Preparation of rod-shaped carbon nitride RCN-3-polydimethylsiloxane composite coating: Take 10g of polydimethylsiloxane and 1.0g of Dow Corning 184 curing agent, stir for 10~20min until completely uniform; then add 30mg of RCN-3, and continue stirring for 30min to obtain the composite coating;

[0047] The coating was applied to a carbon steel surface using a spin coater, dried at room temperature for 24 hours, and then cured at 60 °C for 12 hours. The resulting coating sample was labeled RCN-3 / PDMS.

[0048] Comparative Example 1

[0049] Compared to Example 1, pure-phase PDMS was prepared as follows:

[0050] Take 10 g of polydimethylsiloxane and 1.0 g of Dow Corning 184 curing agent, stir for 10-20 min until completely homogeneous to obtain pure phase PDMS;

[0051] The coating was applied to a carbon steel surface using a spin coater, dried at room temperature for 24 hours, and then cured at 60 °C for 2 hours. The resulting coating sample was labeled as PDMS.

[0052] Comparative Example 2

[0053] Compared with Example 1, a carbon nitride-polydimethylsiloxane coating was prepared:

[0054] (1) Thermal polymerization synthesis of carbon nitride: 2 g of melamine was placed in a 50 mL crucible and placed in a muffle furnace. The temperature was heated from room temperature to 550 °C at a heating rate of 5 °C / min, and then kept at a constant temperature for 2 h. The obtained sample was ground in an agate mortar and collected for later use. The sample was labeled as BCN.

[0055] (2) Preparation of carbon nitride-polydimethylsiloxane coating: Take 10 g of polydimethylsiloxane and 1.0 g of Dow Corning 184 curing agent, stir for 10~20 min until completely uniform, then add 30 mg of BCN and continue stirring for half an hour to obtain composite coating;

[0056] The coating was applied to a carbon steel surface using a spin coater, dried at room temperature for 24 hours, and then cured at 60 °C for 12 hours. The resulting coating sample was labeled BCN / PDMS.

[0057] like Figure 1As shown, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize Comparative Example 2 BCN and all embodiments, observing the changes in the anti-corrosion filler at calcination rates of 1, 2, and 3 °C / min, and comparing it with BCN produced by direct calcination. It was clearly observed that BCN exhibited an irregular and disordered blocky structure with significant aggregation. RCN-X (X=1, 2, 3) released a large amount of gas during thermal polymerization due to controlled calcination rates, which had a significant impact on the shaping of the interlayer structure. RCN-1 exhibited a distinct layered wrinkled structure during slow heating, significantly increasing the material surface area and showing abundant surface defects and active sites. In contrast, RCN-2 had a more complete columnar structure than RCN-1, but its surface showed obvious damage and cracks. The internal layering formed a needle-like, densely packed structure, increasing the total contact area while introducing a large number of active edge sites and crystal defects. The surface structure of RCN-3 is relatively loose, with obvious interlayer cracks and debris accumulation. This may be due to uneven thermal expansion of the material caused by rapid heating, which triggers internal stress and accelerates interlayer fracture and breakage, affecting its physical barrier effect.

[0058] like Figure 2 As shown, the chemical structures of Comparative Example 2 BCN and Example 2 RCN-2 are similar, with a thickness of 3000-3500 cm⁻¹. -1 A distinct broad peak is observed at 1200–1700 cm⁻¹, attributed to stretching vibrations between uncondensed terminal amino groups (-NH₂) or interlayer hydrogen bonds. -1 The strong fluctuation region between these regions is caused by the stretching vibrations unique to the CN heterocycle, verifying the stability of its short-range structure, while the absorption peak is 810 cm⁻¹. -1 The corresponding respiratory vibration pattern of the triazine ring.

[0059] like Figure 3 As shown, the main components of BCN and RCN are C, N, and O. The high-resolution C 1s spectrum of BCN exhibits two distinct peaks, with the strong peak at 288.0 eV being the characteristic main peak of g-C3N4, attributed to the NC=N bond, representing the sp in the triazine and heptaazine rings. 2 Hybridized carbon atoms form a g-C3N4 framework structure. The N 1s spectrum of BCN contains three sub-peaks: the peak at 398.5 eV corresponds to the sp in the triazine ring. 2Hybridized nitrogen atoms; the peak at 400.1 eV is influenced by the heptasulfur ring, while the peak at 401.1 eV may be attributed to hydrogen bonding or charged states. In contrast, the hybridization peaks in the C 1s and N 1s spectra of RCN-2 show a slight negative shift, indicating that the rod-like structure usually forms a more complete conjugated aromatic system, thus providing a stronger shielding effect on the core atom and slightly reducing the binding energy. In the O 1s band spectra of BCN and RCN-2, the characteristic oxygen peaks of both materials are observed at approximately 532.0 eV and 533.2 eV, respectively, corresponding to oxygen-containing functional groups such as COC and C=O.

[0060] like Figure 4 As shown, the cross-sectional morphology of the coatings was compared using scanning electron microscopy (SEM). A smoother cross-sectional image indicates a higher cross-linking density. Visible cracks and microcracks were identifiable on the cross-section of the PDMS coating. The cross-sectional morphology of the BCN / PDMS coating did not change significantly, while the RCN-2 / PDMS coating exhibited a smooth and uniform morphology, interspersed with fine RCN-2 filler particles to fill the micro-cracks and voids in the coating.

[0061] like Figure 5 As shown, the pure PDMS coating and the BCN / PDMS coating have weak adhesion strength and obvious peeling at the scratch edges. The RCN-2 / PDMS coating shows superior integrity and smoothness at the scratch edges, effectively demonstrating the ability of RCN filler to enhance coating adhesion performance.

[0062] like Figure 6 As shown, in the initial stage, all coatings were intact, without defects or water penetration. Low frequency (|Z| f=0.01 Hz Impedance results under Nyquist plots are semi-quantitative indicators for evaluating the corrosion resistance of coatings. In the Nyquist plot, the diameter of the capacitive arc reflects the difference in protective performance of the coatings. In the early stages of immersion, the impedance arc radius of the RCN-modified composite coating is much larger than that of the pure PDMS and CN / PDMS composite coatings, with RCN-2 / PDMS exhibiting the best impedance arc radius. As the immersion time increases, the arc radius decreases slightly, but after 60 days, the impedance radius of the RCN-2 / PDMS coating remains at 5.17 × 10⁻⁶. 9 Ω·cm 2 This indicates that rod-shaped RCN materials can effectively prevent corrosion ions from eroding and enhance the barrier effect of the coating.

[0063] like Figure 7As shown, the salt spray test is a process that simulates the high-salt and high-humidity environment of a marine or industrial setting to accelerate the corrosion process of the coating, thereby evaluating its corrosion resistance. After 72 hours, both pure PDMS and BCN / PDMS coatings exhibited numerous rust spots and corrosion marks in and around the scratches. In contrast, the composite coating with added RCN-2 filler showed weaker diffusion of corrosive substances and demonstrated the best corrosion resistance. This is attributed to the dense rod-like structure of RCN-2 forming an electrically insulating barrier between the metal and the corrosive medium, effectively blocking the penetration of corrosive ions.

[0064] like Figure 8 As shown, the corrosion status of the coating surface in the corrosion area after 60 days of immersion was examined using SEM and energy-dispersive spectroscopy (EDS). The surface beneath the pure PDMS coating was covered and penetrated by the corrosive agent, resulting in extensive rust and cracks, providing convenient channels for corrosive ions and leading to a widespread distribution of iron and corrosive elements. Under the BCN / PDMS coating, the substrate corrosion was mitigated due to the barrier effect of the BCN filler, although visible pitting corrosion still existed. The RCN-2 / PDMS coating surface showed only trace amounts of iron and corrosive elements, indicating no significant rust. This is attributed to the dense layer structure of the rod-shaped RCN material, which forms an insulating barrier between the metal and the corrosive medium, while significantly delaying the penetration of corrosive ions, thereby inhibiting the corrosion process.

[0065] like Figure 9 As shown, *Chlorella*, *Escherichia coli*, and *Staphylococcus aureus* were used as test organisms to evaluate the coating's resistance to and inactivation of biofouling. Comparing the antifouling effects of different coatings on *Chlorella* adhesion, a large amount of *Chlorella* growth was observed on the pure PDMS coating surface, while the adhesion rate of the BCN / PDMS coating was significantly reduced. The RCN-2 / PDMS surface showed very little fouling, exhibiting superior antifouling performance against microorganisms. This is attributed to the RCN-2 filler generating a large amount of photogenerating carriers under light conditions, which react with adsorbed O2 and H2O to generate reactive oxygen species with strong redox properties, thereby destroying the cell wall of *Chlorella* and inhibiting its growth. Simultaneously, the antibacterial effects of the tested coatings against *Escherichia coli* and *Staphylococcus aureus* were also evaluated. Comparing the colony counts of different coatings, it was confirmed that RCN-2 / PDMS achieved inhibition rates of 94.2% and 96.5% against *Escherichia coli* and *Staphylococcus aureus*, respectively. This further validates the high redox activity of ·OH and ·O2. − The substance possesses significant antibacterial properties, giving the coating excellent protection against biofouling.

[0066] like Figure 10 As shown, the number of hydroxyl radicals (·OH) and superoxide radicals (·O2) generated by BCN / PDMS coating and RCN-2 / PDMS coating were compared. -The signal indicates the presence of DMPO-·OH and DMPO-·O2 in the RCN-2 / PDMS coating. - The signal is stronger than that of the BCN / PDMS coating, indicating that the modified RCN-2 filler can significantly promote the generation of ROS active free radicals. These free radicals can disperse into the bacterial suspension, directly contact the bacteria, destroy the bacterial structure, and achieve the property of preventing biocontamination.

Claims

1. A rod-shaped carbon nitride-polydimethylsiloxane composite coating, characterized in that, The composite coating is obtained by mixing rod-shaped carbon nitride filler, polydimethylsiloxane and curing agent; the mass ratio of rod-shaped carbon nitride filler, polydimethylsiloxane and curing agent is 0.019~0.021:10:0.98~1.

02.

2. The carbon nitride packing according to claim 1, characterized in that, The rod-shaped carbon nitride is a g-C3N4 rod-shaped structure with a layered arrangement, and an overall length of about 50~100 μm. It has a dense layered stacked structure inside. Its synthesis is directly obtained by a two-step method of hydrothermal treatment followed by calcination. First, melamine and water are subjected to a hydrothermal reaction, and the mass ratio of water to melamine is 15:1~1.

02. Then, the washed and dried hydrothermal precursor is placed in a muffle furnace for high-temperature calcination. The heating rate is 1~3℃ / min, the holding temperature is 520~550℃, and the holding time is 1.5~3h.

3. The composite coating according to claim 1, characterized in that, The rod-shaped carbon nitride filler has a complete rod-shaped shape. The rod-shaped carbon nitride-polydimethylsiloxane composite coating uses polydimethylsiloxane as the polymer matrix, and the rod-shaped carbon nitride filler is uniformly dispersed in the polymer matrix.

4. A method for preparing the composite coating according to claim 1, characterized in that, Includes the following steps: (1) Dissolve melamine in deionized water and stir; (2) The obtained solution was placed in a reaction vessel for hydrothermal treatment to obtain a rod-shaped precursor; (3) The precursor was washed and dried several times and then calcined in a muffle furnace to obtain rod-shaped carbon nitride filler. (4) Disperse the rod-shaped carbon nitride filler into polydimethylsiloxane and curing agent, and stir to obtain rod-shaped carbon nitride-polydimethylsiloxane composite coating.

5. The manufacturing method according to claim 4, characterized in that, In step (1), the stirring time is 25~35 min, the stirring temperature is room temperature, and the stirring speed is 600~800 r / min; in step (2), the hydrothermal treatment has a heat preservation temperature of 180~200 ℃ and a heat preservation time of 11~13 h.

6. The manufacturing method according to claim 4, characterized in that, In step (3), the calcination has a heating rate of 1~3℃ / min, a holding temperature of 520~550℃, and a holding time of 1.5~3h.

7. The manufacturing method according to claim 4, characterized in that, In step (4), the mass ratio of the rod-shaped carbon nitride filler, polydimethylsiloxane and curing agent is 0.019~0.021: 9.25~10.75: 0.95~1.

05. The mixture is stirred evenly for 10~30 min.

8. The application of the rod-shaped carbon nitride-polydimethylsiloxane composite coating of claim 1 in anti-corrosion, antibacterial and antifouling coatings.

9. The application according to claim 8, characterized in that, Specifically, the application involves applying rod-shaped carbon nitride-polydimethylsiloxane composite coating to the surface of a carbon steel substrate using a spin coater to form a composite coating with a thickness of 30~80 μm.

10. The application according to claim 9, characterized in that, The coating process involves first applying the coating at a low speed (300-600 r / min) for 1-2 minutes, followed by applying the coating at a high speed (1200-1500 r / min) for 3-5 minutes.

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