A sensing self-repairing intelligent coating and a preparation method thereof

Abstract

The application discloses a kind of sensing self-repairing intelligent coating and preparation method thereof.The coating is compounded by component A and curing agent component B according to proportion.The component A mainly includes epoxy resin, phosphorylated lignin grafted silicon carbide, Mo-Co-Ni-S@ diatomite coated with surface SiO2, C@NiSi2@SiC composite particles and polyaniline / epoxy acrylate resin-polydopamine modified graphene microcapsule.During preparation, first mix and disperse epoxy resin with the first three fillers into uniform inorganic slurry, then add microcapsule and stir to obtain component A.During construction, optical fiber sensing element is laid in advance, and then the coating mixed with curing agent is coated.The coating has long-term corrosion prevention and excellent self-repairing and static electricity conduction capacity, and through optical fiber, damage positioning and evaluation of repair effect can be realized.

Description

Technical Field

[0001] This invention relates to a sensing self-healing smart coating and its preparation method, belonging to the field of self-healing coating technology. Background Technology

[0002] Traditional anti-corrosion coatings, during long-term service, can develop microcracks, pinholes, or macroscopic scratches due to mechanical impact, thermal expansion and contraction, substrate fatigue, or media penetration. Once the integrity of the coating is compromised, corrosive media such as water, oxygen, or chloride ions will rapidly penetrate along the defects to the metal / coating interface, causing localized pitting corrosion, crevice corrosion, or under-coating corrosion. More seriously, such hidden damage is often difficult to detect in time, causing corrosion to spread exponentially under the cover of the coating, ultimately leading to structural perforation or fracture.

[0003] To overcome the limitations of passive protection offered by traditional coatings, self-healing anti-corrosion coatings have emerged. Endogenous repair involves incorporating corrosion inhibitors into the coating, utilizing changes in environmental pH or ion exchange mechanisms to release these inhibitory components and generate a passivation film in situ on the metal surface. While these technologies have made some progress, they generally suffer from bottlenecks such as premature leakage of corrosion inhibitors and uncontrollable release of corrosion-inhibiting ions.

[0004] Meanwhile, in certain specific industrial scenarios, in addition to long-term corrosion resistance, the coating must also meet stringent electrostatic discharge requirements. The surface resistivity of the coating needs to be stably controlled at 10. 6 ~10 9 The Ω range is used to safely dissipate static charges generated by friction, flow, or induction, preventing electrostatic sparks from igniting volatile gases. Traditional conductive coatings often construct a percolation conductive network by adding a large amount of highly conductive fillers. However, this high conductivity strategy is fundamentally contradictory to long-term corrosion protection: after the conductive fillers form a continuous electronic pathway inside the coating, once the coating suffers minor damage, the conductive filler network will form a typical large cathode-small anodic microcouple corrosion cell with the exposed metal substrate, leading to an increase in anodic dissolution current density and causing localized corrosion perforation. Summary of the Invention

[0005] The purpose of this invention is to provide a self-healing intelligent coating for sensing and its preparation method. The coating has excellent corrosion resistance and self-healing properties, as well as good static electricity conductivity.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A sensing self-healing smart coating, comprising component A and component B;

[0008] Component A, by weight, includes the following components:

[0009] Epoxy resin: 40-60 parts;

[0010] Phosphorylated lignin grafted with silicon carbide: 10-21 parts;

[0011] Mo-Co-Ni-S@diatomaceous earth with SiO2 coating: 0.5-4 parts;

[0012] C@NiSi2@SiC composite particles: 0.7-3.7 parts;

[0013] Polyaniline / epoxy acrylate resin-polydopamine modified graphene microcapsules: 0.7-5 parts;

[0014] Component B is a curing agent, and its dosage is 0.2-0.3 times that of component A.

[0015] Preferably, the preparation method of phosphorylated lignin grafted silicon carbide includes the following steps:

[0016] (1) Disperse lignin in water, adjust the pH to 8-11 with alkali, add sodium trimetaphosphate to react, and then acidify to pH 2-3 to precipitate the product. After centrifugation, washing and drying, phosphorylated lignin is obtained.

[0017] (2) Disperse silicon carbide micro powder in an ethanol / water mixture, add silane coupling agent, and after reaction, centrifuge, wash and dry to obtain aminated silicon carbide.

[0018] (3) Disperse phosphorylated lignin and aminated silicon carbide in water, add EDC / NHS crosslinking agent, stir and react at room temperature in the dark, and then centrifuge, wash and dry.

[0019] Preferably, in step (1), the ratio of lignin to water is 1g:(8-15)mL; the alkali is NaOH solution, and the mass ratio of lignin to sodium trimetaphosphate is 1:(0.3-0.6); the reaction conditions are: 50-80℃, 4-8 hours.

[0020] In step (2), the amount of silane coupling agent added accounts for 5-15% of the mass of silicon carbide micro powder, and the reaction temperature conditions are: 60-80℃, 2-6 hours;

[0021] In step (3), the mass ratio of phosphorylated lignin to aminated silicon carbide is 1:(1-5), and the amount of EDC / NHS crosslinking agent added accounts for 10-45% of the phosphorylated lignin mass. The reaction is carried out at room temperature with stirring in the dark for 8-24 hours.

[0022] Preferably, the preparation method of Mo-Co-Ni-S@diatomite coated with SiO2 includes the following steps:

[0023] (1) Using diatomite as a carrier, nickel salt, cobalt salt, molybdenum salt and thiourea were added and subjected to hydrothermal reaction to obtain Mo-Co-Ni-S@diatomite precursor;

[0024] (2) Disperse the precursor in an ethanol / water mixture, add tetraethyl orthosilicate for hydrolysis and polycondensation, and then wash and dry.

[0025] Preferably, in step (1), the nickel salt, cobalt salt, and molybdenum salt are nickel nitrate hexahydrate, cobalt nitrate hexahydrate, and ammonium molybdate tetrahydrate, respectively, wherein the Ni:Co:Mo molar ratio is 1:(0.3-0.8):(0.02-0.1), the molar ratio of thiourea to total metal is (4-8):1, and the hydrothermal reaction conditions are 160-200℃ for 12-24 hours;

[0026] In step (2), the amount of tetraethyl orthosilicate added is 5-20% of the precursor mass, and the pH of the system is adjusted to 8.5-9.5, and the hydrolysis-condensation reaction time is 2-6 hours.

[0027] Preferably, the preparation method of C@NiSi2@SiC includes the following steps:

[0028] (1) Aminated silicon carbide micro powder was dispersed in an aqueous solution of nickel nitrate hexahydrate, stirred and loaded and dried. Then anhydrous ethanol, water, ammonia and tetraethyl orthosilicate were added to carry out sol-gel reaction to coat the SiO2 layer and obtain Ni-SiO2@SiC precursor.

[0029] (2) The Ni-SiO2@SiC precursor was mixed with magnesium powder and inert salt, ground and dried, heated and reacted under an inert atmosphere, and then cooled and acid washed to remove byproducts to obtain NiSi2@SiC intermediate;

[0030] (3) The intermediate is mixed with phenolic resin and heated and carbonized under an inert atmosphere to obtain C@NiSi2@SiC composite particles.

[0031] Preferably, in step (1), the concentration of the nickel nitrate hexahydrate aqueous solution is 0.05-0.2 mol / L, and the mass ratio of aminated silicon carbide micro powder to nickel nitrate hexahydrate is 1:(0.4-0.6); in the sol-gel reaction, the amount of tetraethyl orthosilicate added is 20-50% of the mass of aminated silicon carbide, the pH of the system is controlled at 9-10, and the reaction is stirred at 20-50℃ for 10-15 hours;

[0032] In step (2), the inert salt is anhydrous NaCl, and the mass ratio of the precursor, magnesium powder and inert salt is 1:(0.5-1):(1-3).

[0033] The heating reaction conditions are as follows: first, raise the temperature to 400-500℃ at a rate of 2-5℃ / min and hold for 0.5-1 hour, then raise the temperature to 650-750℃ and hold for 1-3 hours;

[0034] In step (3), the mass ratio of intermediate to phenolic resin is (3-6):1, and the carbonization conditions are: heating to 700-800℃ at a heating rate of 3-5℃ / min and holding for 1-2 hours.

[0035] Preferably, the preparation method of polyaniline / epoxy acrylate resin-polydopamine modified graphene microcapsules includes the following steps:

[0036] (1) Graphene was dispersed in Tris-HCl buffer, dopamine hydrochloride was added and stirred to react, and PDA-modified graphene was obtained by centrifugation, washing and drying.

[0037] (2) A mixture of PDA-modified graphene and epoxy acrylate resin monomers was added to an aqueous phase containing emulsifier as an oil phase to form a stable oil / water emulsion. Aniline monomer and ammonium persulfate were slowly added to the emulsion to carry out an interfacial oxidative polymerization reaction, forming a polyaniline capsule wall that encapsulates the oil phase droplets. After separation, washing, and freeze-drying, microcapsules were obtained.

[0038] Preferably, in step (1), the pH of the Tris-HCl buffer is 8-9, the amount of dopamine hydrochloride added is 50-200% of the graphene mass, and the stirring reaction conditions are: 20-30℃, 8-24 hours;

[0039] In step (2), the mass ratio of epoxy acrylate resin to PDA-modified graphene in the oil phase is 1:(0.05-0.15);

[0040] The mass ratio of oil phase, aniline monomer, ammonium persulfate, and emulsifier is 1:(1.1-1.3):(2.9-3.4):(0.25-0.35);

[0041] The emulsifier is sodium dodecylbenzenesulfonate, and the ratio of emulsifier to aqueous phase is (0.5-0.7) g: 120 mL;

[0042] The emulsification conditions are 800-1200 rpm for 20-45 minutes; the temperature for dropwise addition and oxidative polymerization is controlled at 0-5℃, and the reaction time is 4-5 hours.

[0043] Preferably, component A further includes 0.5-3 parts by weight of auxiliary additives, which include one or more of fumed silica thixotropic agents, defoamers, and leveling agents.

[0044] In any of the above-mentioned methods for preparing a self-healing intelligent coating, component A is prepared by mixing and dispersing epoxy resin with phosphorylated lignin-grafted silicon carbide, SiO2-coated Mo-Co-Ni-S@diatomaceous earth, and C@NiSi2@SiC composite particles to obtain a uniform inorganic slurry; then, polyaniline / epoxy acrylate resin-polydopamine modified graphene microcapsules are added to the system and stirred.

[0045] The coating construction method based on any one of the above-mentioned sensing self-healing smart coatings includes the following steps:

[0046] (1) Sandblasting is performed on the surface of the metal substrate to remove rust;

[0047] (2) Lay the fiber optic sensing element on the surface of the metal substrate and fix it;

[0048] (3) After thoroughly mixing and maturing component A and component B, spray them evenly onto the surface of the metal substrate and the fiber optic sensing element.

[0049] The beneficial effects of this invention are as follows:

[0050] (1) The phosphorylated lignin layer grafted onto the PL-g-SiC surface possesses insulation and steric hindrance effects. When it is filled in a high proportion in the coating, it acts as the dominant insulating phase, separating the components in the coating and preventing them from contacting each other to form a long-range percolation conductive network. This structure stabilizes the surface resistivity of the coating at 10 Ω·cm. 6 -10 9 Within the Ω range, it meets the requirements for electrostatic conductivity; at the same time, since no long-range continuous conductive path is formed, the galvanic current between the coating and the metal substrate after the coating is damaged is limited to a low level, thereby mitigating localized corrosion. The SiO2 insulating coating layer on the surface of Mo-Co-Ni-S@diatomite and the outer carbon shell of C@NiSi2@SiC serve as auxiliary isolation barriers, further reducing the probability of direct contact between conductive fillers, and together with PL-g-SiC, they form a multi-level insulation isolation system.

[0051] (2) When the coating develops microcracks due to stress fatigue or media penetration, or macroscopic penetrating scratches due to mechanical impact, moisture or chloride ions in the local microenvironment can invade the filler interface. The phosphate ester bonds on the PL-g-SiC surface undergo controlled breakage, slowly releasing phosphate ions. Phosphate ions complex with iron ions generated by the anodic dissolution of the matrix to form an iron phosphate passivation film. At the same time, the SiO2 coating layer on the Mo-Co-Ni-S@diatomite surface undergoes controlled hydrolysis in the weakly alkaline electrolyte of the local microenvironment at the crack, slowly releasing silicate ions; in C@NiSi2@SiC, the outer carbon shell has a nanoscale microporous structure, allowing the corrosive medium to slowly penetrate to the NiSi2 core surface, inducing local electrochemical activation of NiSi2 and releasing trace amounts of SiO3.2- with Ni 2+ Both work synergistically to participate in the deposition of silicate gel. The iron phosphate film and silicate gel intertwine at the microcracks, forming a mineralized sealing layer.

[0052] The forces generated by the aforementioned defects cause the microcapsules to rupture. Upon exposure of the metal substrate, polyaniline forms a dense passivation film, effectively inhibiting anodic dissolution and allowing time for subsequent chemical bonding, achieving active protection through passivation followed by healing. The released epoxy acrylate resin rapidly fills the cracks via capillary action. Its large molecular long chains undergo physical wetting, diffusion, and chain entanglement at the crack interface, achieving physical sealing of the microcracks through the resin's high adhesion and cohesive force. Simultaneously, the abundant hydroxyl and ester groups in the epoxy acrylate resin molecular chain spontaneously construct a dense supramolecular hydrogen bond network with the unreacted active sites of the matrix epoxy resin, enabling the repaired area to quickly restore excellent coating cohesion and structural integrity. The graphene sheets further form a physical barrier, enhancing the mechanical integrity and barrier properties of the repaired area.

[0053] (3) By pre-laying fiber optic sensing elements on the surface of the substrate and encapsulating them with a coating, the degree of damage and damage location can be determined by monitoring changes in the optical signal. At the same time, the repair effect can also be evaluated by monitoring changes in the optical signal. Detailed Implementation

[0054] The present invention will be described in detail below with reference to embodiments and comparative examples. It should be understood that the specific embodiments described herein are for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention.

[0055] Example 1

[0056] 1. Preparation of phosphorylated lignin grafted with silicon carbide (PL-g-SiC)

[0057] Add 120 mL of deionized water to a 500 mL three-necked flask and turn on the magnetic stirrer (350 rpm). Slowly add 12.0 g of industrial alkali lignin, and adjust the pH of the system to 9.8 by adding 1 mol / L NaOH solution dropwise. Continue stirring for 60 minutes until the lignin is completely dissolved. Raise the water bath temperature to 68 °C, and under nitrogen protection, add a total of 6.0 g of sodium trimetaphosphate in three batches at 30-minute intervals. Maintain a constant temperature of 68 °C and stir for 6.5 hours. After the reaction is complete, slowly add 1 mol / L HCl solution dropwise to gradually lower the pH to 2.5, causing a flocculent precipitate to form. Centrifuge the precipitate at 4000 rpm for 12 minutes and discard the supernatant. Repeat the resuscitation and centrifugation washing of the precipitate with deionized water 5 times until the pH of the washing solution is neutral. Finally, transfer the wet precipitate to a lyophilization tray, pre-freeze at -50 °C for 12 hours, and then freeze-dry under vacuum for 48 hours to obtain PL powder.

[0058] Take 12.0 g of SiC micro powder (particle size 0.5-1.0 μm) and add it to 250 mL of a mixed solvent of anhydrous ethanol and deionized water (volume ratio 9:1). Disperse ultrasonically (40 kHz, 300 W) for 35 minutes. Add 1.5 g of silane coupling agent KH-550 and react with magnetic stirring in a 72 °C water bath for 4.5 hours. After the reaction is complete, centrifuge the mixture at 6000 rpm for 10 minutes. Wash the precipitate four times with anhydrous ethanol and dry it under vacuum at 65 °C for 12 hours to obtain aminated silicon carbide powder.

[0059] Take another 5.0 g of the above PL powder and dissolve it in 180 mL of deionized water (add a small amount of NaOH to aid dissolution until pH 8.2). Disperse 6.0 g of aminated SiC powder ultrasonically in the PL solution. Then, add 1.0 g of EDC and 1.0 g of NHS sequentially. The system is magnetically stirred at room temperature (25±2℃) in the dark for 14 hours. After the reaction is complete, collect the product by centrifugation and wash it 6 times alternately with deionized water and anhydrous ethanol. Dry under vacuum at 65℃ for 12 hours, grind through a 300-mesh sieve to obtain PL-g-SiC.

[0060] 2. Preparation of SiO2-coated Mo-Co-Ni-S@diatomaceous earth

[0061] Weigh 12.0 g of natural diatomaceous earth ore and place it in a polytetrafluoroethylene beaker. Add 120 mL of 1 mol / L dilute hydrochloric acid solution and soak the ore at room temperature with magnetic stirring for 26 hours. After filtration, wash with deionized water until the pH of the filtrate reaches 7.0. Then, redisperse the filter cake in anhydrous ethanol and ultrasonically wash twice (18 minutes each time). After drying at 65℃, place the calcined diatomaceous earth in a muffle furnace and calcine it at a heating rate of 5℃ / min to 520℃ for 3.5 hours. Allow it to cool naturally to obtain activated diatomaceous earth.

[0062] 1.2 g of activated diatomaceous earth was ultrasonically dispersed in 60 mL of deionized water. 0.350 g of nickel nitrate hexahydrate, 0.175 g of cobalt nitrate hexahydrate, and 0.014 g of ammonium molybdate tetrahydrate were added sequentially, and the mixture was stirred for 35 minutes until completely dissolved (Ni:Co:Mo molar ratio ≈ 1:0.5:0.05). Then, 0.660 g of thiourea was added, and stirring was continued for 18 minutes. The mixture was transferred to a 75 mL PTFE-lined stainless steel high-pressure reactor, with the filling density controlled at 70%. After sealing, the reactor was placed in an oven and subjected to a hydrothermal reaction at 185 °C for 19 hours. After natural cooling to room temperature, the solid was collected by centrifugation, washed five times sequentially with deionized water and anhydrous ethanol, and dried at 65 °C to obtain the Mo-Co-Ni-S@diatomaceous earth precursor.

[0063] 1.2 g of the above precursor was dispersed in 60 mL of an ethanol / water (9:1) mixture. 0.15 g of TEOS was added dropwise, and the pH was adjusted to 9.3 with dilute ammonia. The hydrolysis and condensation reaction was carried out at 65 °C for 4.5 hours with stirring. After centrifugation, washing, and drying at 65 °C, Mo-Co-Ni-S@diatomaceous earth with a SiO2 insulating layer on the surface was obtained.

[0064] 3. Preparation of C@NiSi2@SiC

[0065] Take 6.0 g of the aminated SiC obtained in step 1 of Example 1, disperse it in 60 mL of 0.16 mol / L nickel nitrate aqueous solution, and stir at room temperature for 2.5 hours. Remove water by rotary evaporation at 65 °C to obtain dry Ni-supported SiC. Redisperse it in 60 mL of anhydrous ethanol, add 2.5 mL of TEOS and 0.6 mL of deionized water, add concentrated ammonia dropwise as a catalyst, and stir at room temperature for 13 hours. The sol-gel process generates a SiO2 layer on the particle surface. After centrifugation and drying, obtain the Ni-SiO2@SiC composite precursor.

[0066] 3.5 g of the above composite precursor was mixed with 2.5 g of magnesium powder (200 mesh) and 7.0 g of anhydrous NaCl in an agate mortar. 25 mL of anhydrous ethanol was added, and the mixture was wet-ground and dried under vacuum at 60 °C. The mixture was placed in a corundum boat and then placed in a tube furnace. High-purity Ar gas was introduced to purge the furnace for 35 minutes. The temperature was increased to 450 °C at 5 °C / min and held for 35 minutes (to initiate the magnesothermic reaction), then increased to 710 °C at 2 °C / min and held for 2.5 hours. After the reaction was complete, the furnace was cooled to room temperature. The product was removed, washed four times with deionized water, and then placed in a 1.2 mol / L dilute hydrochloric acid solution and magnetically stirred at 55 °C for 4.5 hours. The product was collected by centrifugation, washed repeatedly with deionized water until the filtrate pH reached 7.0, washed twice with anhydrous ethanol, and dried under vacuum at 65 °C to obtain the NiSi2@SiC intermediate.

[0067] 3.5 g of NiSi2@SiC intermediate and 0.7 g of thermosetting phenolic resin were mixed, and the mixture was wet-milled in 12 mL of anhydrous ethanol and then evaporated to dryness. The mixture was placed in a corundum boat and then placed in a tube furnace. High-purity Ar gas was introduced to purge the mixture for 35 minutes. The temperature was increased to 760℃ at 3℃ / min and held at that temperature for 1.5 hours for carbonization. After the reaction was completed, the mixture was allowed to cool naturally to room temperature under an Ar atmosphere. The product was then removed, gently ground, and passed through a 400-mesh sieve to obtain C@NiSi2@SiC composite particles.

[0068] 4. Preparation of polyaniline / epoxy acrylate resin-polydopamine modified graphene microcapsules

[0069] 1.2 g of graphene powder was added to 120 mL of Tris-HCl buffer (50 mM) at pH 8.6. The mixture was ultrasonically dispersed (200 W, ice-water bath) for 70 minutes to form a homogeneous suspension. 1.8 g of dopamine hydrochloride was added, and the mixture was magnetically stirred at 26 °C in the dark for 13 hours. The solid was collected by centrifugation and washed four times alternately with deionized water and ethanol. The solid was then vacuum-dried at 65 °C for 12 hours to obtain PDA-modified graphene.

[0070] In a 250 mL three-necked flask, 120 mL of deionized water and 0.6 g of SDBS emulsifier were added, and the mixture was stirred at 1000 rpm to form a micelle solution. A mixture of 1.8 g of epoxy acrylate resin and 0.18 g of PDA-modified graphene was used as the oil phase and slowly added dropwise to the aqueous phase. Emulsification was continued for 30 minutes to form a stable oil / water emulsion. In a separate beaker, 2.4 g of aniline monomer was dissolved in 30 mL of 1 mol / L HCl and slowly added dropwise to the emulsion at 0-5 °C, while simultaneously adding 6.5 g of ammonium persulfate dissolved in 25 mL of 1 mol / L HCl as an oxidizing agent. Aniline underwent oxidative polymerization at the oil-water interface, forming polyaniline (PANI) capsules that encapsulated oil droplets of epoxy acrylate resin / PDA-G. After reacting for 4.5 hours, the mixture was collected by centrifugation, washed with deionized water until the filtrate was free of chloride ions, and freeze-dried for 48 hours to obtain microcapsules.

[0071] 5. Coating Preparation

[0072] Accurately weigh the following components by weight: 50 parts of bisphenol A type epoxy resin (E-51, epoxy value 0.51eq / 100g), 1.0 part of fumed silica thixotropic agent, 0.3 parts of defoamer, 0.2 parts of leveling agent, 12 parts of the above-prepared PL-g-SiC, 1 part of insulating Mo-Co-Ni-S@diatomaceous earth, and 1 part of C@NiSi2@SiC. Place the above materials in a high-speed dispersion tank and disperse and grind at 1600 rpm for 45 minutes, controlling the slurry temperature to <40℃ during this period. Obtain a uniform inorganic slurry. Subsequently, reduce the dispersion speed to 250 rpm and slowly add 2 parts of the above-prepared microcapsules. Gently stir at 200 rpm for 15 minutes to obtain component A. Before construction, add polyamide curing agent to component A at a mass ratio of 4:1, stir evenly, and cure for 15 minutes.

[0073] 6. Coating Structure Construction

[0074] Take a Q235 carbon steel substrate (200 mm × 100 mm × 2 mm) and sandblast it with brown corundum abrasive. The surface roughness Ra is controlled at 40-60 μm, achieving a cleanliness level of Sa2.5. Wipe off the oil with anhydrous ethanol and dry with cold air.

[0075] The optical fibers (125μm core diameter, 250μm cladding) were laid in parallel straight lines on the steel plate surface, with an adjacent fiber spacing of 100mm. A small amount of epoxy primer was applied to both ends of the fibers and every 50mm. A glass rod was used to gently press the fibers into close contact with the steel plate. The primer was allowed to dry at room temperature for 30 minutes.

[0076] The prepared coating was uniformly sprayed onto the steel plate and optical fiber surface using a spray gun. The spray gun distance was controlled at 25 cm, the moving speed at 15 cm / s, and two cross-coats were applied. The wet film thickness was controlled at 200 μm. After curing at room temperature (25±2℃, relative humidity 50±5%) for 7 days, the dry film thickness was 150±10 μm. The optical fiber was tightly wrapped under the coating, approximately 80 μm from the outer surface of the coating.

[0077] Splice the two ends of the optical fiber into pigtails and connect them to an OTDR demodulator (wavelength 1550nm, pulse width 10ns).

[0078] Example 2

[0079] It is basically the same as Example 1, except that:

[0080] The composite functional filler is formulated as follows: 11 parts PL-g-SiC, 2 parts insulating Mo-Co-Ni-S@diatomaceous earth, 2 parts C@NiSi2@SiC, and 1 part microcapsule.

[0081] Fine-tuning of the preparation temperature for each filler: Phosphorylated lignin preparation temperature is 70℃, reaction time is 6 hours; hydrothermal growth temperature is 190℃, reaction time is 20 hours; magnesiac reduction stepwise heating: 450℃ constant temperature for 30 minutes, then heated to 720℃ and held for 2 hours; carbonization temperature is 770℃, held for 1.5 hours.

[0082] The fiber optic laying path was changed to an orthogonal grid pattern, with a grid cell size of 50 mm × 50 mm.

[0083] Coating preparation parameters: dispersion speed 1500 rpm, 40 min; microcapsule compounding speed 220 rpm, 12 min.

[0084] The coating construction process is the same as in Example 1.

[0085] Example 3

[0086] It is basically the same as Example 1, except that:

[0087] The composite functional filler is formulated as follows: 12 parts PL-g-SiC, 1 part insulating Mo-Co-Ni-S@diatomaceous earth, 1 part C@NiSi2@SiC, and 1 part microcapsule.

[0088] Fine-tuning of the preparation temperature for each filler: Phosphorylated lignin preparation temperature is 65℃, reaction time is 7 hours; hydrothermal growth temperature is 175℃, reaction time is 22 hours; magnesiac reduction stepwise heating: 450℃ constant temperature for 40 minutes, then heated to 690℃ and held for 2.5 hours; carbonization temperature is 740℃, held for 1.8 hours.

[0089] Comparative Example 1

[0090] This is essentially the same as Example 1, except that PL-g-SiC is replaced with aminated SiC micropowder without grafted phosphorylated lignin.

[0091] Comparative Example 2

[0092] It is basically the same as Example 1, except that Mo-Co-Ni-S@diatomaceous earth is not coated with an insulating layer.

[0093] Comparative Example 3

[0094] The coating is basically the same as in Example 1, except that Mo-Co-Ni-S@diatomaceous earth with surface insulation coating is not added to the coating.

[0095] Comparative Example 4

[0096] It is basically the same as Example 1, except that C@NiSi2@SiC composite particles were not added to the coating.

[0097] Comparative Example 5

[0098] It is basically the same as Example 1, except that the amount of PL-g-SiC used in the coating is 2 parts by weight.

[0099] Performance testing methods

[0100] All example and comparative test panels were cured in a standard curing room (25°C, RH 50%) for 7 days and then tested according to the following methods.

[0101] 1. Surface resistivity test: The surface resistivity of the coating was tested using a high-resistivity meter (EST121 type, DC 100 V). Five measurement points (four corners and center) were taken for each test plate, and the average value was taken. The test environment temperature was 23±2℃ and the relative humidity was 50±5%.

[0102] 2. Electrochemical impedance spectroscopy (EIS) test: In a 3.5 wt% NaCl solution, a three-electrode system (working area 1 cm²) was used. 2 (Saturated calomel electrode reference, platinum sheet counter electrode), frequency range 10 5 -10 -2 Hz, amplitude 10mV. Before testing, the test plate was immersed in NaCl solution for 30 days, and the low-frequency impedance modulus |Z| was recorded.0.01 Hz. A 20mm scratch penetrating to the substrate was then artificially created using a blade, and the substrate was soaked for another 7 days, with impedance changes monitored. The impedance recovery rate was calculated: (after repair |Z|) 0.01 Hz / Initial |Z| 0.01 (Hz)×100%.

[0103] 3. According to ASTM B117, test panels with pre-prepared 20 mm artificial scratches were placed in a salt spray chamber and continuously sprayed for 500 hours. After the test, the test panels were removed, rinsed with deionized water to remove surface salt deposits, and dried. Standard tape (or a hard scraper) was firmly applied to the scratches and quickly peeled off to remove loose coating that had lost adhesion at the scratch edges. Subsequently, the width of unilateral rust spread due to corrosion was measured, with measurements taken at three different locations on each test panel and the average value recorded.

[0104] 4. Fiber Optic Signal Monitoring: During the salt spray test, the OTDR continuously records changes in optical power (every 2 hours). The initial optical power P0, the lowest optical power Pmin after the instantaneous attenuation following the scratch, and the optical power Prec after stabilization following repair are recorded. The optical intensity recovery rate is defined as: (Prec - Pmin) / (P0 - Pmin) × 100%.

[0105] 5. Interface Adhesion Test: A three-point bending tester was used with a span of 150 mm and a loading rate of 2 mm / min. Loading was stopped after the first visible microcrack appeared on the coating surface (the optical power after unloading is recorded as Punload). OTDR was connected throughout the process to monitor fiber optic power drift. After unloading, the area was allowed to stand for 2 hours, and the optical signal recovery rate was calculated as: (Punload - Pmin) / (P0 - Pmin) × 100%.

[0106] 6. Galvanic corrosion current test: Using a zero-resistance galvanometer, a galvanic pair is formed between the coated test plate (exposed metal at the scratch) and a pure platinum electrode, and the steady-state galvanic current density is measured in a 3.5% NaCl solution.

[0107] Performance test results.

[0108] Table 1. Overall performance test data of the examples and comparative examples.

[0109]

[0110] Note: Due to severe interface debonding in Comparative Example 1, the optical signal continued to drift erratically, making it impossible to calculate the light intensity recovery rate.

[0111] The surface resistivity of all three embodiments is 2.1 × 10⁻⁶. 8 -4.2×10 8 Within the Ω range, it fully meets the usage requirements. After soaking for 30 days, the low-frequency impedance modulus reached 10.9 Ω·cm 2 The magnitude indicates that the coating possesses excellent long-term corrosion resistance. After 500 hours of salt spray testing, the unilateral rust width at the scratch was between 0.6 and 1.3 mm, significantly smaller than that in the comparative studies. The galvanic current density was 0.8–1.2 μA / cm². 2 Within the range, it is far lower than the 8.5 μA / cm of Comparative Example 1. 2 Compared to Comparative Example 5, it is 6.8 μA / cm. 2 This indicates that the addition of PL-g-SiC insulating isolation pillars can effectively suppress galvanic corrosion.

[0112] Regarding fiber optic monitoring, the optical signal recovery rate after bending unloading in all three embodiments was greater than 94%, indicating good bonding at the fiber / resin interface and no significant micro-debonding. The trend of light intensity change after scratching was a consistent attenuation followed by a stable recovery, indicating that the redistribution of local stress field after microcrack repair can be detected by optical fiber, achieving in-situ evaluation of the repair effect. As shown in Table 1, Embodiment 2 exhibited the highest light intensity recovery rate after scratch repair and the highest optical signal recovery rate after bending unloading. This is mainly attributed to its orthogonal mesh fiber laying method, where denser fiber intersections significantly improved the detection sensitivity of local stress changes and the damage repair process.

[0113] Comparative Example 1 uses ungrafted, unmodified SiC, although the surface resistivity is still 4.0 × 10⁻⁶. 8 The impedance was Ω, but after soaking for 30 days, it dropped significantly to 1.2 × 10⁻⁶. 8 Ω·cm 2 The salt spray corrosion width reached 3.8 mm, and the galvanic current density was as high as 8.5 μA / cm. 2 This is because the original SiC and resin interface lacks chemical bonding, resulting in numerous micron-sized debonding pores that become channels for rapid penetration of corrosive media. These debonding pores form localized electrolyte-rich regions at the coating / metal interface, forming microscopic electrical couples with the discretely distributed Mo-Co-Ni-S@diatomite and C@NiSi2@SiC in the coating, significantly accelerating localized anodic dissolution. Simultaneously, the lack of steric hindrance from PL macromolecules leads to a certain degree of SiC particle aggregation. Although a macroscopic percolation conductive network is not formed, the local electric field distortion at the edges of the aggregates further promotes pitting corrosion initiation. The continuous random drift of the fiber optic signal indicates that interface failure triggers irreversible microbending loss.

[0114] In Comparative Example 2, the surface resistivity of Mo-Co-Ni-S@diatomaceous earth without a SiO2 insulating layer decreased to 2.5 × 10⁻⁶. 7 Ω, the galvanic current density rises to 5.6 μA / cm 2The salt spray corrosion width was 2.2 mm, and the light intensity recovery rate was only 18%. This is because the uncoated Mo-Co-Ni-S@diatomite has high conductivity, forming local conductive channels in the coating and increasing the risk of galvanic corrosion. At the same time, the lack of the SiO2 layer caused the Mo-Co-Ni-S@diatomite to release silicate and metal ions too quickly in the microcracks, which could not work synergistically with phosphate mineralization, resulting in a decreased repair effect.

[0115] In Comparative Example 3, after removing Mo-Co-Ni-S@diatomite, the salt spray corrosion width was 1.9 mm, the impedance recovery rate was 48%, and the light intensity recovery rate was only 12%, all of which were inferior to Example 1. This is because the removal of Mo-Co-Ni-S@diatomite led to a significant decrease in the total supply of silicate. The silicate provided by C@NiSi2@SiC alone was insufficient to fully synergize with phosphate, resulting in insufficient mineralization layer deposition, decreased density, and incomplete microcrack sealing.

[0116] In Comparative Example 4, after removing C@NiSi2@SiC, the salt spray corrosion width was 1.7 mm, the impedance recovery rate was 51%, and the light intensity recovery rate was 15%, which was also worse than that of Example 1. This is because C@NiSi2@SiC provides silicate and trace amounts of Ni through the slow-release effect of the carbon shell micropores. 2+ This compensates for the insufficient ion concentration when Mo-Co-Ni-S@diatomite is supplied alone, and forms a physical barrier layer in the repair area with the help of carbon shell deposition, blocking the penetration of corrosive media. Without it, the amount of silicate gel deposition is insufficient, the density decreases, the crack sealing is incomplete, and the local electrochemical activity in the repair area increases.

[0117] The galvanic current density of Comparative Examples 3 and 4 remained at a low level, indicating that PL-g-SiC, as the main insulating filler, is the core factor in inhibiting galvanic corrosion. The amounts of Mo-Co-Ni-S@diatomite and C@NiSi2@SiC were small, and their removal alone was insufficient to destroy the overall insulating isolation framework established by PL-g-SiC, but it would significantly weaken the self-healing mineralization ability at the crack (manifested as a decrease in impedance recovery rate and light intensity recovery rate).

[0118] In Comparative Example 5, reducing the amount of PL-g-SiC to 2 parts resulted in a severe deficiency in the density of the insulating isolation pillars. The surface resistivity decreased to 5.0 × 10⁻⁶. 5 Ω, already below 10 6The conductive coating with a resistivity of Ω enters the strong conductivity range, falling below the safety lower limit. At this point, the static charge dissipation rate on the coating surface is too fast, potentially generating a large discharge current and posing a risk of electrostatic spark ignition. Simultaneously, the excessively low resistivity indicates that the conductive filler has formed a long-range percolation network, creating a large cathodic-small anodic galvanic corrosion system with the exposed metal substrate, increasing the galvanic current density to 6.8 μA / cm². Furthermore, the sharp reduction in PL-g-SiC dosage not only leads to insufficient phosphate release sources but also reduces the overall cohesion of the coating. The epoxy acrylic resin released after microcapsule rupture cannot effectively anchor and entangle based on sufficient inorganic-organic interface hydrogen bonding networks. The adhesion strength at the crack interface after physical filling is insufficient, microcracks cannot be effectively sealed, and the salt spray corrosion width reaches 3.2 mm with no significant recovery in light intensity. After immersion for 30 days, the impedance is only 3.5 × 10⁻⁶. 8 Ω·cm², which is much lower than in Example 1.

Claims

1. A sensor-based self-healing intelligent coating, characterized in that, Includes component A and component B; Component A, by weight, includes the following components: Epoxy resin: 40-60 parts; Phosphorylated lignin grafted with silicon carbide: 10-21 parts; Mo-Co-Ni-S@diatomaceous earth with SiO2 coating: 0.5-4 parts; C@NiSi2@SiC composite particles: 0.7-3.7 parts; Polyaniline / epoxy acrylate resin-polydopamine modified graphene microcapsules: 0.7-5 parts; Component B is a curing agent, and its dosage is 0.2-0.3 times that of component A.

2. The self-healing intelligent coating according to claim 1, characterized in that, The preparation method of phosphorylated lignin grafted silicon carbide includes the following steps: (1) Disperse lignin in water, adjust the pH to 8-11 with alkali, add sodium trimetaphosphate to react, and then acidify to pH 2-3 to precipitate the product. After centrifugation, washing and drying, phosphorylated lignin is obtained. (2) Disperse silicon carbide micro powder in an ethanol / water mixture, add silane coupling agent, and after reaction, centrifuge, wash and dry to obtain aminated silicon carbide. (3) Disperse phosphorylated lignin and aminated silicon carbide in water, add EDC / NHS crosslinking agent, stir and react at room temperature in the dark, and then centrifuge, wash and dry.

3. The sensing self-healing intelligent coating according to claim 2, characterized in that, In step (1), the ratio of lignin to water is 1g:(8-15)mL; the alkali is NaOH solution, and the mass ratio of lignin to sodium trimetaphosphate is 1:(0.3-0.6); the reaction conditions are: 50-80℃, 4-8 hours. In step (2), the amount of silane coupling agent added accounts for 5-15% of the mass of silicon carbide micro powder, and the reaction temperature conditions are: 60-80℃, 2-6 hours; In step (3), the mass ratio of phosphorylated lignin to aminated silicon carbide is 1:(1-5), and the amount of EDC / NHS crosslinking agent added accounts for 10-45% of the phosphorylated lignin mass. The reaction is carried out at room temperature with stirring in the dark for 8-24 hours.

4. The sensing self-healing intelligent coating according to claim 1, characterized in that, The preparation method of SiO2-coated Mo-Co-Ni-S@diatomite includes the following steps: (1) Using diatomite as a carrier, nickel salt, cobalt salt, molybdenum salt and thiourea were added and subjected to hydrothermal reaction to obtain Mo-Co-Ni-S@diatomite precursor; (2) Disperse the precursor in an ethanol / water mixture, add tetraethyl orthosilicate for hydrolysis and polycondensation, and then wash and dry.

5. The sensing self-healing intelligent coating according to claim 4, characterized in that, In step (1), the nickel salt, cobalt salt, and molybdenum salt are nickel nitrate hexahydrate, cobalt nitrate hexahydrate, and ammonium molybdate tetrahydrate, respectively. The molar ratio of Ni:Co:Mo is 1:(0.3-0.8):(0.02-0.1), the molar ratio of thiourea to total metal is (4-8):1, and the hydrothermal reaction conditions are 160-200℃ for 12-24 hours. In step (2), the amount of tetraethyl orthosilicate added is 5-20% of the precursor mass, and the pH of the system is adjusted to 8.5-9.

5. The hydrolysis and polycondensation reaction time is 2-6 hours.

6. The sensing self-healing intelligent coating according to claim 1, characterized in that, The preparation method of C@NiSi2@SiC includes the following steps: (1) Aminated silicon carbide micro powder was dispersed in an aqueous solution of nickel nitrate hexahydrate, stirred and loaded and dried. Then anhydrous ethanol, water, ammonia and tetraethyl orthosilicate were added to carry out sol-gel reaction to coat the SiO2 layer and obtain Ni-SiO2@SiC precursor. (2) The Ni-SiO2@SiC precursor was mixed with magnesium powder and inert salt, ground and dried, heated and reacted under an inert atmosphere, and then cooled and acid washed to remove byproducts to obtain NiSi2@SiC intermediate; (3) The intermediate is mixed with phenolic resin and heated and carbonized under an inert atmosphere to obtain C@NiSi2@SiC composite particles.

7. The sensing self-healing intelligent coating according to claim 6, characterized in that, In step (1), the concentration of the nickel nitrate hexahydrate aqueous solution is 0.05-0.2 mol / L, and the mass ratio of aminated silicon carbide micro powder to nickel nitrate hexahydrate is 1:(0.4-0.6); in the sol-gel reaction, the amount of tetraethyl orthosilicate added is 20-50% of the mass of aminated silicon carbide, the pH of the system is controlled at 9-10, and the reaction is stirred at 20-50℃ for 10-15 hours; In step (2), the inert salt is anhydrous NaCl, and the mass ratio of the precursor, magnesium powder and inert salt is 1:(0.5-1):(1-3). The heating reaction conditions are as follows: first, raise the temperature to 400-500℃ at a rate of 2-5℃ / min and hold for 0.5-1 hour, then raise the temperature to 650-750℃ and hold for 1-3 hours; In step (3), the mass ratio of intermediate to phenolic resin is (3-6):1, and the carbonization conditions are: heating to 700-800℃ at a heating rate of 3-5℃ / min and holding for 1-2 hours.

8. The self-healing intelligent coating according to claim 1, characterized in that, The preparation method of polyaniline / epoxy acrylate resin-polydopamine modified graphene microcapsules includes the following steps: (1) Graphene was dispersed in Tris-HCl buffer, dopamine hydrochloride was added and stirred to react, and PDA-modified graphene was obtained by centrifugation, washing and drying. (2) A mixture of PDA-modified graphene and epoxy acrylate resin monomers was added to an aqueous phase containing emulsifier as an oil phase to form a stable oil / water emulsion. Aniline monomer and ammonium persulfate were slowly added to the emulsion to carry out an interfacial oxidative polymerization reaction, forming a polyaniline capsule wall that encapsulates the oil phase droplets. After separation, washing, and freeze-drying, microcapsules were obtained.

9. The self-healing intelligent coating according to claim 8, characterized in that, In step (1), the pH of the Tris-HCl buffer is 8-9, the amount of dopamine hydrochloride added is 50-200% of the graphene mass, and the stirring reaction conditions are: 20-30℃, 8-24 hours. In step (2), the mass ratio of epoxy acrylate resin to PDA-modified graphene in the oil phase is 1:(0.05-0.15); The mass ratio of oil phase, aniline monomer, ammonium persulfate, and emulsifier is 1:(1.1-1.3):(2.9-3.4):(0.25-0.35); The emulsifier is sodium dodecylbenzenesulfonate, and the ratio of emulsifier to aqueous phase is (0.5-0.7) g: 120 mL; The emulsification conditions are 800-1200 rpm for 20-45 minutes; the temperature for dropwise addition and oxidative polymerization is controlled at 0-5℃, and the reaction time is 4-5 hours.

10. The method for preparing the sensing self-healing smart coating according to any one of claims 1-9, characterized in that, The preparation of component A involves mixing and dispersing epoxy resin with phosphorylated lignin-grafted silicon carbide, SiO2-coated Mo-Co-Ni-S@diatomaceous earth, and C@NiSi2@SiC composite particles to obtain a uniform inorganic slurry; then, polyaniline / epoxy acrylate resin-polydopamine modified graphene microcapsules are added to the system and stirred.

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