MXene composite coating with low infrared emissivity and radar stealth

Abstract

This application discloses an MXene composite coating that combines low infrared emissivity and radar stealth. The composite coating (100) includes: a primer layer (102) adhered to the surface of a substrate (101), and a topcoat layer (103) located on the surface of the primer layer (102); the thickness ratio of the primer layer (102) to the topcoat layer (103) is 8:1 to 15:1; the primer layer (102) comprises an aqueous polyurethane matrix resin and Fe3O4@Ti3C2T dispersed therein. x Magnetoelectric heterojunction microwave absorbing filler; topcoat layer (103) contains fluorocarbon resin and APTES-Ti3C2T x Nanosheets, APTES-Ti3C2T x The nanosheets are arranged in a two-dimensional layered orientation parallel to the surface of the substrate (101) in the topcoat layer (103). This application can overcome the incompatibility between radar waves and infrared stealth, and has a multispectral compatible camouflage effect with low emissivity and electromagnetic impedance matching, while providing anti-corrosion and moisture-proof properties.

Description

Technical Field

[0001] This application relates to the field of special functional coatings and special camouflage materials, specifically to an MXene composite coating that combines low infrared emissivity and radar stealth. Background Technology

[0002] High-value military equipment such as fighter jets, drones, missiles, and ground armor faces reconnaissance threats from infrared thermal imagers and microwave radar. Aircraft and military equipment generate infrared radiation during high-speed operation or engine exhaust, and their metal casings also create radar echoes. Surface coatings for this equipment need to balance infrared stealth and radar stealth. Infrared stealth requires surface materials to have low infrared emissivity and high infrared reflectivity, while radar stealth requires materials to possess electromagnetic impedance matching and electromagnetic wave absorption loss characteristics.

[0003] Currently, existing multi-band compatible stealth coatings suffer from irreconcilable technical contradictions. Due to the mutual repulsion between the electromagnetic properties of radar waves and the infrared band, the high conductivity and impedance mismatch of metallic low-infrared coatings lead to interface reflection of radar waves, rendering radar stealth ineffective. Conventional radar-absorbing coatings often exhibit infrared emissivity greater than 0.85. Two-dimensional transition metal carbides such as Ti3C2T... x While the material possesses high electrical conductivity, low infrared emissivity, and low sheet loss characteristics, its end groups contain hydroxyl and fluorine groups, making it prone to oxidative degradation in air and humid environments, forming TiO2. This oxidative degradation disrupts the internal conductive network of the material, leading to a decrease in stealth performance. (Single Ti3C2T) x Direct film formation from slurry also faces engineering defects such as low adhesion and easy peeling, making it difficult to meet the requirements of moisture-proof, waterproof and salt spray-proof. Summary of the Invention

[0004] This application provides an MXene composite coating that combines low infrared emissivity and radar stealth, in order to solve the problems of mutual repulsion between the radar absorption and infrared reflection electromagnetic properties of existing coatings, as well as the easy oxidation and degradation and poor adhesion of two-dimensional MXene materials in humid and hot environments.

[0005] This application provides an MXene composite coating that combines low infrared emissivity and radar stealth, comprising a primer layer and a topcoat layer. The primer layer is adhered to the surface of a substrate. The topcoat layer is located on the surface of the primer layer. The thickness ratio of the primer layer to the topcoat layer is between 8:1 and 15:1. The primer layer comprises an aqueous polyurethane matrix resin and Fe3O4@Ti3C2T dispersed in the aqueous polyurethane matrix resin. x Magnetoelectric heterojunction microwave absorbing filler. The topcoat layer contains fluorocarbon resin and APTES-Ti3C2T dispersed in the fluorocarbon resin. x Nanosheets. APTES-Ti3C2T xThe nanosheets are arranged in a two-dimensional layered orientation parallel to the substrate surface in the topcoat layer.

[0006] Furthermore, the thickness of the primer layer is configured to be 80 micrometers to 150 micrometers. Fe3O4@Ti3C2T x The mass fraction of the magnetoelectric heterojunction microwave absorbing filler in the primer layer is configured to be 15% to 25%.

[0007] Furthermore, Fe3O4@Ti3C2T x Magnetoelectric heterojunction absorbing fillers include two-dimensional Ti3C2T x Substrate and in-situ growth on two-dimensional Ti3C2T x Fe3O4 nanoparticles on the substrate surface and between layers.

[0008] Furthermore, the thickness of the topcoat layer is configured to be 10 to 20 micrometers. APTES-Ti3C2T x The mass fraction of nanosheets in the topcoat layer is configured to be between 10% and 20%.

[0009] Furthermore, APTES-Ti3C2T x The nanosheets consist of pure MXene nanosheets and a passivation layer formed by an aminosilane coupling agent coating the surface of the pure MXene nanosheets. The amino groups in the aminosilane coupling agent are bonded to the oxygen-containing functional groups on the surface of the pure MXene nanosheets via hydrogen bonds.

[0010] This application also provides a method for preparing an MXene composite coating that combines low infrared emissivity and radar stealth, comprising the following steps: obtaining Fe3O4@Ti3C2T x A magnetoelectric heterojunction microwave absorbing filler was dispersed in an aqueous polyurethane matrix resin to obtain a primer coating. APTES-Ti3C2T was then obtained. x Nanosheets are dispersed in fluorocarbon resin to obtain a topcoat layer. A primer layer is applied to the substrate surface and cured for the first time to form a primer layer. A topcoat layer is then applied to the primer layer surface and cured for the second time to form the topcoat layer. During the application of the topcoat layer, APTES-Ti3C2T... x The nanosheets are arranged in a layered, oriented manner parallel to the substrate surface under the action of coating shear force.

[0011] Furthermore, in obtaining Fe3O4@Ti3C2T x Before the magnetoelectric heterojunction absorbing filler, the preparation method also includes two-dimensional Ti3C2T x The dispersion was mixed with an iron salt solution. Under alkaline conditions, a co-precipitation reaction was carried out, allowing iron ions to precipitate in a two-dimensional Ti3C2T atmosphere. xFe3O4 nanoparticles were conformally grown in situ in the dispersion, and Fe3O4@Ti3C2T were obtained after centrifugation and washing. x Magnetoelectric heterojunction wave-absorbing filler.

[0012] Furthermore, in acquiring APTES-Ti3C2T x Prior to nanosheets, preparation methods also included two-dimensional Ti3C2T x The dispersion was mixed with the hydrolysate of the aminosilane coupling agent. The reaction was carried out under magnetic stirring at a preset temperature, utilizing the aminosilane coupling agent to react with two-dimensional Ti3C2T. x The surface was passivated and then centrifuged and washed to obtain APTES-Ti3C2T. x Nanosheets.

[0013] Furthermore, both the steps of applying the primer layer to the substrate surface and the steps of applying the topcoat layer to the primer layer surface are performed using an air spraying process. When spraying the topcoat layer, the nozzle axis of the spray gun is perpendicular to the primer layer surface, causing the atomized droplets to generate a laterally broadened flow field parallel to the primer layer surface after impacting it, driving the APTES-Ti3C2T... x Nanosheets are produced in a two-dimensional layered orientation.

[0014] This application also provides a military equipment, including a substrate and the aforementioned MXene composite coating with both low infrared emissivity and radar stealth properties coated on the surface of the substrate.

[0015] By constructing a composite coating with a dual-layer gradient impedance structure, the topcoat layer utilizes a specific concentration of directional APTES-Ti3C2T. x Nanosheets form a high-reflectivity cross-section, blocking outward emission of thermal radiation and maintaining a low infrared emissivity. Microwave electromagnetic waves penetrate the topcoat layer and enter the primer layer, utilizing the magnetic loss provided by Fe3O4 nanoparticles and the interaction between Ti3C2T... x The provided polarization relaxation and conduction loss generate electromagnetic synergistic coupling, dissipating radar wave energy. Fluorocarbon resin and passivation layer improve the oxidation problem of MXene and enhance substrate adhesion, achieving the integration of multispectral compatible camouflage and anti-corrosion and moisture-proof properties. Attached Figure Description

[0016] Figure 1 A two-dimensional cross-sectional view of the composite coating provided in an embodiment of this application is shown;

[0017] Figure 2 A flowchart of the composite coating preparation method provided in the embodiments of this application is shown;

[0018] Figure 3 This application illustrates the Fe3O4@Ti3C2T provided in an embodiment. xTwo-dimensional cross-sectional view of the internal morphology of the magnetoelectric heterojunction absorbing filler;

[0019] Figure 4 The present application provides exemplary test results data for different coating performances.

[0020] Explanation of reference numerals in the attached figures

[0021] In the diagram: 100 - composite coating, 101 - substrate, 102 - primer layer, 103 - topcoat layer, 301 - two-dimensional Ti3C2T x Substrate, 302-Fe3O4 nanoparticles, -Fe3O4@Ti3C2T x Magnetoelectric heterojunction microwave absorbing filler, - waterborne polyurethane matrix resin, - APTES-Ti3C2T x Nanosheets, fluorocarbon resin. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solutions of this application, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] In one embodiment of this application, an MXene composite coating that combines low infrared emissivity with radar stealth is provided. Figure 1 As shown in the two-dimensional cross-sectional view, the composite coating 100 is attached to the surface of the substrate 101 of the equipment and is composed of a primer layer 102 and a topcoat layer 103 in sequence along the direction away from the substrate 101. The thickness ratio of the primer layer 102 to the topcoat layer 103 is strictly controlled within the range of 8:1 to 15:1. This thickness ratio design is based on the difference in skin depth of electromagnetic waves in different bands. Radar microwave bands have longer wavelengths, and the skin effect is weaker when electromagnetic waves penetrate extremely thin materials; therefore, the topcoat layer 103 is designed to be thinner so that radar waves can pass through. In contrast, infrared bands have extremely short wavelengths, and a thinner topcoat layer 103 is sufficient to form a thermal radiation reflection barrier.

[0024] Specifically, the primer layer 102 serves as the main radar-absorbing layer of the composite coating 100, and its thickness is configured to be 150 micrometers to 250 micrometers. It should be noted that, to adapt to the actual coating requirements of substrates with different volumes or curvatures, in certain specific embodiments, the thickness of the primer layer 102 can also be configured to be 80 micrometers to 150 micrometers. The primer layer 102 mainly consists of a waterborne polyurethane matrix resin and Fe3O4@Ti3C2T uniformly dispersed within the waterborne polyurethane matrix resin. x It is composed of a magnetoelectric heterojunction microwave absorbing filler. In terms of formulation ratio, every 100 parts by weight of waterborne polyurethane matrix resin contains 25 to 40 parts by weight of Fe3O4@Ti3C2T xMagnetoelectric heterojunction microwave absorbing filler. Corresponding to the solid contents in the primer layer 102 after film formation, Fe3O4@Ti3C2T x The mass fraction of the magnetoelectric heterojunction absorbing filler is configured to be 15% to 25%. The waterborne polyurethane matrix resin has flexibility and substrate adhesion properties, which can ensure that the thick primer layer 102 does not crack under long-term thermal expansion and contraction stress.

[0025] like Figure 3 The microscopic morphology cross-section diagram shows the core loss unit Fe3O4@Ti3C2T in the primer layer 102. x The magnetoelectric heterojunction absorbing filler exhibits a specific hierarchical structure. It mainly comprises two-dimensional Ti3C2T... x Substrate 301, and in-situ grown on two-dimensional Ti3C2T x Fe3O4 nanoparticles 302 on the surface of substrate 301 and between layers within the sheets. Fe3O4 nanoparticles 302 and two-dimensional Ti3C2T. x A magnetic-dielectric double-loss mechanism is formed between the substrates 301. In this magnetoelectric heterojunction network, after radio frequency electromagnetic waves enter the primer layer 102, the conversion of electromagnetic energy into thermal energy follows the impedance matching theory and the transmission line attenuation model. According to microwave transmission line theory, the specific formula for calculating the reflection loss of the absorbing material is as follows:

[0026] (1)

[0027] (2)

[0028] Where RL represents reflection loss, the unit is decibel; Z in Z0 represents the input impedance of the absorbing coating surface; Z0 represents the intrinsic impedance in free space, approximately 377 ohms; μ r ε represents the complex permeability of the absorbing coating medium, characterizing the material's response to and dissipation capability in an alternating magnetic field; r The complex permittivity of the absorbing coating medium represents the polarization response and attenuation capability of the material to an alternating electric field; f represents the frequency of the incident electromagnetic wave; d represents the thickness of the absorbing coating medium; c represents the speed of light in a vacuum; and j represents the imaginary unit. Specifically, the system performs calculations based on the above equations during the measurement process. In this embodiment, the thickness d of the primer layer 102 is set between 150 micrometers and 250 micrometers, and the two-dimensional Ti3C2T... x The substrate 301 generates a large complex permittivity ε through internal multiple interface polarizations and leakage current. r The imaginary part, and the complex permeability μ of Fe3O4 nanoparticles 3O2 is provided through natural resonance, exchange resonance and magnetic domain wall resonance mechanisms. rEffective improvement. In-situ growth achieves a tight bond between the two materials, mitigating the input impedance Z caused by the excessively high complex permittivity of a single MXene material. in The problem lies in the mismatch with the spatial impedance Z0. This impedance gradient structure guides 8 to 12 GHz X-band microwaves into the interior of the coating, where they are deeply lost, thus reducing interface reflection.

[0029] Refer again Figure 1 The topcoat layer 103 serves as the main control layer for infrared reflection and three-proof protection, with a thickness ranging from 10 micrometers to 20 micrometers. The topcoat layer 103 comprises a fluorocarbon resin, specifically an aqueous dispersion of polytetrafluoroethylene, and APTES-Ti3C2T dispersed within the fluorocarbon resin. x Nanosheets. In terms of formulation ratio, each 100 parts by weight of fluorocarbon resin contains 5 to 10 parts by weight of APTES-Ti3C2T. x Nanosheets. Corresponding to the solids contained in the topcoat layer 103 after film formation, APTES-Ti3C2T x The nanosheets are configured with a mass fraction of 10% to 20%. APTES-Ti3C2T x The nanosheets are arranged in a two-dimensional layered orientation parallel to the surface of the substrate 101 in the topcoat layer 103.

[0030] Specifically, APTES-Ti3C2T x The internal structure of the nanosheets comprises pure MXene nanosheets and a passivation layer formed by an aminosilane coupling agent coating the surface of the pure MXene nanosheets. The surface of the pure MXene nanosheets has highly active end groups, which readily bind water molecules and oxygen and undergo degradation reactions under humid and hot environments. Here, the aminosilane coupling agent chemically seals the defect sites on the surface of the pure MXene nanosheets, and the amino groups in its molecular structure also bind with the residual oxygen-containing functional groups on the surface of the pure MXene nanosheets through numerous hydrogen bonds, forming a dense, cross-linked passivation protection network. Due to APTES-Ti3C2T x The concentration of nanosheets exceeds the percolation threshold and is oriented within the 10-20 micrometer topcoat layer 103. These parallel nanosheets overlap horizontally to form a dense metallic conductive network. In the 8-14 micrometer infrared long-wave band, this continuous conductive network exhibits a high reflectivity cross-section, blocking the outward emission of heat radiation generated by internal equipment. The fluorocarbon resin topcoat prevents the intrusion of external water and oxygen, achieving moisture-proof and corrosion-proof functions and improving the overall substrate bonding strength of the coating to level 5B. Through the gradient impedance and pure fluorocarbon separation structure of the primer layer 102 and the topcoat layer 103, the disordered distribution of MXene in a single mixed slurry, which would lead to excessively high coating roughness, is prevented.

[0031] In another embodiment of this application, a method for preparing an MXene composite coating that combines low infrared emissivity and radar stealth is provided. This method is used to prepare the composite coating described in the above embodiment. Figure 2 The method flowchart is shown, and the preparation method includes the following steps.

[0032] Step S201 involves surface pretreatment of the substrate. The substrate is typically made of hard aluminum alloy. Before the coating process begins, the substrate surface is sandblasted to remove oxide scale and increase surface roughness. Anhydrous ethanol or a specialized degreasing solvent is then used for cleaning to remove surface grease and dirt. This surface pretreatment increases the mechanical adhesion between the coating and the substrate, ensuring initial adhesion of the subsequent primer layer.

[0033] Step S202: Etching and stripping are performed to prepare two-dimensional Ti3C2T. x Aqueous dispersion. 5 g of Ti3AlC2 powder was slowly added in portions to a mixed solution containing 1 g LiF and 20 mL of HCl at a concentration of 9 mol / L. The mixture was placed in a water bath and magnetically stirred at a constant temperature of 35°C for 24 hours. During this process, LiF reacted with HCl in situ to generate hydrofluoric acid, which selectively etched the highly reactive Al atomic layers. After the etching reaction was complete, the mixture was transferred to a centrifuge and washed repeatedly with deionized water until the pH of the supernatant was close to 6. Under an inert argon atmosphere, the mixture was sonicated for 1 hour using a cell disruptor. The microjets generated by the ultrasonic cavitation effect broke the van der Waals forces between the etched material layers, achieving layer exfoliation. The supernatant was collected by centrifugation at 3500 rpm, yielding a monolayer of pure Ti3C2T with a concentration of approximately 5 mg / mL. x Aqueous dispersion.

[0034] Step S203: Prepare Fe3O4@Ti3C2T via in-situ coprecipitation reaction. x Magnetoelectric heterojunction microwave absorbing filler. Measure 100 ml of the above-prepared Ti3C2T... x The dispersion was prepared by sequentially adding 2.5 mmol of FeCl3·6H2O and 1.25 mmol of FeCl2·4H2O. Nitrogen gas was introduced to purge oxygen from the reaction system, and the mixture was stirred thoroughly at 800 rpm for 30 minutes under nitrogen protection to dissolve the iron salts and allow them to be converted to Ti3C2T. xAdsorption by functional groups on the surface. A 0.5 mol / L NaOH solution was added dropwise using a peristaltic pump, with the pH of the system monitored in real time until the pH of the mixture reached 10.5. The system was heated to 65°C and held at that temperature for 2 hours. Under alkaline conditions, ferric ions and ferrous ions co-precipitated to form Fe3O4 nuclei. Due to the negative charge and oxygen-containing functional groups on the MXene surface providing numerous low-barrier nucleation sites, the generated Fe3O4 nanoparticles with a particle size distribution of 15 nm to 30 nm were uniformly anchored on the two-dimensional Ti3C2T. x In-situ conformal growth was achieved on the substrate surface. After the reaction, the precipitate was washed by centrifugation and then dried at constant weight in a vacuum drying oven at 60°C to obtain black Fe3O4@Ti3C2T. x Magnetoelectric heterojunction microwave absorbing filler powder. By employing an in-situ growth process, the agglomeration of magnetic nanoparticles in the slurry system is prevented, ensuring the uniform distribution of electromagnetic loss centers.

[0035] Step S204: Prepare APTES-Ti3C2T by surface passivation modification. x Nanosheets. Measure 100 mL of pure Ti3C2T at a concentration of 5 mg / mL. x An aqueous dispersion was prepared by adding 10 mL of anhydrous ethanol and 2 mL of 3-aminopropyltriethoxysilane. The mixture was placed in a reflux condenser and refluxed at 40°C for 6 hours. During the reaction, the molecules underwent hydrolysis to generate silanol structures, which reacted with two-dimensional Ti3C2T... x The hydroxyl groups on the surface undergo condensation and dehydration reactions to form stable Si-O-Ti covalent bonds. The outwardly extending amino groups in the coupling agent molecule alter the surface energy and hydrophilic wettability of MXene, and some amino groups form hydrogen bond networks with the residual oxygen-containing end groups of adjacent nanosheets. After the reaction, the mixture is transferred to a centrifuge and washed three times with ethanol to remove unreacted residues. After freeze-drying, highly dispersed APTES-Ti3C2T is obtained. x Nanoparticle powder.

[0036] Step S205: Prepare the coating slurry. Obtain the Fe3O4@Ti3C2T prepared in step S203 above. x Magnetoelectric heterojunction microwave absorbing filler powder. 30 grams of Fe3O4@Ti3C2T... x The powder, along with 100g of aqueous polyurethane emulsion and 3g of polycarboxylate dispersant, was added to the grinding jar of a planetary ball mill. An appropriate amount of grinding media was added, and the mixture was continuously ground at 400 rpm for 2 hours to break up particle agglomeration, producing a primer coating slurry with a solid content of 45%. The APTES-Ti3C2T prepared in step S204 was obtained. xNanoparticle powder. 8 grams of APTES-Ti3C2T x The powder was added to 100 grams of polytetrafluoroethylene emulsion with a solid content of 50%, and then placed in an ultrasonic cleaning tank for ultrasonic dispersion for 30 minutes to obtain a uniform topcoat slurry.

[0037] Step S206: Primer application and curing. Using a high-pressure airless spraying device, the primer layer is evenly applied to the surface of the hard aluminum alloy substrate treated in step S201. High-pressure airless spraying effectively overcomes the atomization difficulties of high-viscosity slurries. The sprayed substrate is then placed in an 80°C constant-temperature oven for the first curing process for 30 minutes. During curing, moisture evaporates, and the polyurethane resin undergoes physical cross-linking to form a film. The final film thickness is precisely controlled at 200 micrometers, with an error range of ±15 micrometers, forming a dense primer layer.

[0038] Step S207, Topcoat Layer Oriented Coating and Curing. The topcoat layer is applied to the surface of the primer layer, using either a wire-bar coater or electrostatic air spraying. When using a wire-bar coater, the wet film thickness is precisely controlled at 25 micrometers; when using air spraying, the nozzle axis of the spray gun is perpendicular to the primer layer surface. Driven by a high-speed airflow, atomized droplets impact the primer layer surface with extremely high normal kinetic energy. Upon impact, the normal velocity rapidly decays, and the fluid diffuses outwards, generating a laterally broadened flow field parallel to the primer layer surface. Both the physical shear force of the wire-bar coating and the lateral flow field distribution shear force of the air spraying cause directional deformation and stretching of the fluid micro-clusters within the slurry. Due to APTES-Ti3C2T x Nanosheets possess extremely high aspect ratio geometry, enabling them to overcome the randomness of Brownian motion and undergo orientation flipping along the shear flow direction under the forced drive of microscopic shear force. Combined with the physical spatial constraints of the thinness of the topcoat layer itself, this forces all nanosheets to form a two-dimensional layered orientation parallel to the substrate surface. After coating, the substrate is placed in a high-temperature curing oven at 150 degrees Celsius for a second curing of 1 hour, allowing the fluorocarbon resin to crosslink and cure, ultimately forming a dense topcoat layer with a dry thickness of 12 micrometers and an error range of ±2 micrometers.

[0039] In another embodiment of this application, a military equipment is provided. The external structural components of this military equipment include a metal substrate and the aforementioned MXene composite coating, which combines low infrared emissivity and radar stealth, coated on the surface of the substrate. The primer layer and topcoat layer of this composite coating work together. External radar detection microwaves can penetrate the topcoat layer, enter the polyurethane primer layer, and be absorbed by Fe3O4@Ti3C2T xThe internal magnetic loss mechanism is converted into heat dissipation; the heat generated by the operation of the equipment's own engine or electronic components, when attempting to radiate to the outside, is blocked by the dense APTES-Ti3C2T structure oriented within the topcoat layer. x The high reflectivity cross-section formed by the conductive network blocks and causes internal reflection, reducing the infrared radiation brightness of the equipment surface.

[0040] Standardized tests were performed on the samples from Example 1 and the corresponding comparative examples:

[0041] Example 1: A double-layer composite coating sample prepared entirely according to the above preparation method steps S201 to S207.

[0042] Comparative Example 1, i.e., the control group without magnetic modification, had its microwave-absorbing filler in the primer layer replaced with an equal mass of unmodified pure two-dimensional Ti3C2T. x The nanosheets do not contain Fe3O4, and the remaining structure, formulation, and process parameters of the coating are consistent with those in Example 1.

[0043] Comparative Example 2, i.e., the single-layer mixed control group, did not employ the double-layer gradient coating process. Fe3O4@Ti3C2T x Filler and APTES-Ti3C2T x After the fillers are mixed in the same proportion, they are directly added to the mixture of waterborne polyurethane and polytetrafluoroethylene for a one-time single-layer thick coating. The total thickness after drying is controlled to be 215 micrometers.

[0044] The testing standards and equipment are as follows: Infrared emissivity in the 8-14 micrometer band was measured at room temperature using a dual-band infrared emissivity meter. The minimum radar reflection loss (RL) of the coating in the 8-12 GHz X-band was tested using a vector network analyzer based on the coaxial line method. The effective absorption bandwidth was defined as the frequency bandwidth where RL is less than or equal to -10 dB. The surface resistivity change rate was measured after 72 hours in a constant temperature and humidity chamber at 85°C and 85% relative humidity to evaluate the resistance to damp heat degradation. A 96-hour neutral salt spray corrosion test was conducted in a 5% NaCl solution according to ASTM B117 standard to observe the red rust and adhesion.

[0045] The obtained test data results are summarized in the table below. Relevant data were also extracted and plotted. Figure 4 The performance test results data curve is shown in the figure.

[0046] A physical mechanism analysis was conducted on the experimental results. Comparing the test results of Example 1 and Comparative Example 1, it can be seen that the primer layer of Comparative Example 1 lacks the Fe3O4 magnetoelectric heterostructure design, resulting in low real and imaginary parts of the complex permeability of the material in a high-frequency microwave alternating field. Consequently, radar waves entering the coating lack a magnetic loss mechanism and cannot be effectively absorbed, with a minimum reflection loss of only -12.4 dB. This demonstrates that the technical feature of in-situ anchoring magnetic particles via co-precipitation to improve the impedance matching and absorption capacity of the primer layer is indispensable.

[0047] Comparing the test results of Example 1 and Comparative Example 2, it can be seen that Comparative Example 2 abandoned the double-layer gradient impedance and pure fluorocarbon surface layer separation structure, resulting in a spatially disordered three-dimensional random distribution of MXene nanosheets in the mixed slurry. This disordered distribution increases the overall surface roughness of the coating and disrupts the impedance gradient channel for microwave transmission on the surface, causing direct reflection of radar waves at the air-coating interface, with the absorption performance attenuating to -21.3 dB. Simultaneously, the disordered arrangement cannot form a continuous, dense, low-emissivity reflective network, increasing the infrared emissivity to 0.82 and reducing infrared stealth capabilities. Because Comparative Example 2 lacks the combined protection mechanism of the fluorocarbon resin surface layer and passivation modification, moisture and oxygen-containing salt ions easily penetrate into the coating along resin defects, attacking high-energy defect sites of MXene and inducing oxidation. This leads to an increase in the resistivity change rate to positive 45.2% after the damp heat resistance test, and the appearance of swelling spots on the coating.

[0048] This application constructs a synergistic transmission path that combines microwave transmission dissipation and infrared high reflectivity isolation through the combined effects of double-layer physical layer thickness gradient control, in-situ eutectic growth of the bottom layer, and aminosilane coupling modification and directional arrangement process of the surface layer. This reduces infrared emissivity and radar return reflection loss indicators, and improves the adhesion strength and corrosion aging resistance of the coating system. It should be noted that the specific parameters listed in the above embodiments and test data are only preferred examples. Those skilled in the art can adaptively adjust the resin component ratio or coating thickness within the scope defined by the claims according to actual application needs. As long as the multi-band separation effect of impedance gradient can be achieved, the technical solution of this application can also be realized.

Claims

1. An MXene composite coating that combines low infrared emissivity and radar stealth, characterized in that, include: A primer layer (102) is attached to the surface of a substrate (101); a topcoat layer (103) is located on the surface of the primer layer (102); wherein the thickness ratio of the primer layer (102) to the topcoat layer (103) is 8:1 to 15:1; the primer layer (102) comprises an aqueous polyurethane matrix resin and Fe3O4@Ti3C2T dispersed in the aqueous polyurethane matrix resin. x Magnetoelectric heterojunction microwave absorbing filler; the topcoat layer (103) comprises fluorocarbon resin and APTES-Ti3C2T dispersed in the fluorocarbon resin. x Nanosheets; the APTES-Ti3C2T x The nanosheets are arranged in a two-dimensional layered orientation parallel to the surface of the substrate (101) in the topcoat layer (103).

2. The MXene composite coating with both low infrared emissivity and radar stealth as described in claim 1, characterized in that, The thickness of the primer layer (102) is configured to be 80 micrometers to 150 micrometers; the Fe3O4@Ti3C2T x The mass fraction of the magnetoelectric heterojunction microwave absorbing filler in the primer layer (102) is configured to be 15% to 25%.

3. The MXene composite coating with both low infrared emissivity and radar stealth as described in claim 2, characterized in that, The Fe3O4@Ti3C2T x Magnetoelectric heterojunction absorbing fillers include two-dimensional Ti3C2T x The substrate (301) and the in-situ grown on the two-dimensional Ti3C2T x Fe3O4 nanoparticles (302) on the surface of substrate (301) and between layers.

4. The MXene composite coating with both low infrared emissivity and radar stealth as described in claim 1, characterized in that, The thickness of the topcoat layer (103) is configured to be 10 micrometers to 20 micrometers; the APTES-Ti3C2T x The nanosheets are configured in the topcoat layer (103) in a mass fraction of 10% to 20%.

5. The MXene composite coating with both low infrared emissivity and radar stealth as described in claim 4, characterized in that, The APTES-Ti3C2T x The nanosheets include pure MXene nanosheets and a passivation layer formed by an aminosilane coupling agent coating the surface of the pure MXene nanosheets; the amino groups in the aminosilane coupling agent are bonded to the oxygen-containing functional groups on the surface of the pure MXene nanosheets through hydrogen bonds.

6. A method for preparing an MXene composite coating possessing both low infrared emissivity and radar stealth, used to prepare an MXene composite coating possessing both low infrared emissivity and radar stealth as described in any one of claims 1 to 5, characterized in that, include: Obtain Fe3O4@Ti3C2T x A magnetoelectric heterojunction microwave absorbing filler is dispersed in an aqueous polyurethane matrix resin to obtain a primer coating. Obtain APTES-Ti3C2T x Nanosheets are dispersed in fluorocarbon resin to obtain a topcoat coating. The primer layer is applied to the surface of the substrate (101) and cured for the first time to form a primer layer (102); The topcoat layer is applied to the surface of the primer layer (102) and then cured a second time to form the topcoat layer (103); wherein, during the application of the topcoat layer, the APTES-Ti3C2T x The nanosheets are arranged in a layered orientation parallel to the surface of the substrate (101) under the action of coating shear force.

7. The method for preparing the MXene composite coating with both low infrared emissivity and radar stealth as described in claim 6, characterized in that, In obtaining Fe3O4@Ti3C2T x Before the magnetoelectric heterojunction absorbing filler, the preparation method further includes: Two-dimensional Ti3C2T x The dispersion was mixed with an iron salt solution; under alkaline conditions, a co-precipitation reaction was carried out to allow iron ions to form in the two-dimensional Ti3C2T solution. x Fe3O4 nanoparticles (302) were conformally grown in situ in the dispersion, and the Fe3O4@Ti3C2T nanoparticles were obtained after centrifugation and washing. x Magnetoelectric heterojunction wave-absorbing filler.

8. The method for preparing the MXene composite coating with both low infrared emissivity and radar stealth as described in claim 6, characterized in that, In obtaining APTES-Ti3C2T x Prior to the preparation of nanosheets, the preparation method further includes: Two-dimensional Ti3C2T x The dispersion was mixed with the aminosilane coupling agent hydrolysate; a magnetic stirring reaction was carried out under a preset temperature condition to utilize the aminosilane coupling agent for the two-dimensional Ti3C2T reaction. x The surface was passivated and then centrifuged and washed to obtain the APTES-Ti3C2T. x Nanosheets.

9. The method for preparing the MXene composite coating with both low infrared emissivity and radar stealth as described in claim 6, characterized in that, Both the steps of applying the primer coating to the substrate (101) and applying the topcoat coating to the primer layer (102) are performed using an air spraying process. When spraying the topcoat coating, the nozzle axis of the spray gun is perpendicular to the surface of the primer layer (102), causing the atomized droplets to generate a laterally broadened flow field parallel to the surface of the primer layer (102) after impacting it, thus driving the APTES-Ti3C2T... x Nanosheets are produced in a two-dimensional layered orientation.

10. A type of military equipment, characterized in that, It includes a substrate (101) and an MXene composite coating (100) with both low infrared emissivity and radar stealth coated on the surface of the substrate (101); the MXene composite coating (100) with both low infrared emissivity and radar stealth is the MXene composite coating with both low infrared emissivity and radar stealth as described in any one of claims 1 to 5.

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