Lightweight marine environment-resistant wave-absorbing coating and preparation method thereof

Abstract

The present application relates to nanometer wave-absorbing material preparation and marine environment wave-absorbing coating preparation technical field, especially disclose a kind of light weight marine environment resistant wave-absorbing coating and preparation method thereof, the wave-absorbing coating includes nanometer light density wave-absorbing agent coating pre-dispersion, nanometer dielectric loss type heavy density wave-absorbing agent and curing agent;And nanometer light density wave-absorbing agent coating pre-dispersion includes the material of high crystalline carbon-coated single-walled carbon nanotube prepared by in-situ, the high crystalline carbon-coated single-walled carbon nanotube structure is stable, not only has excellent wave-absorbing characteristics, while having good corrosion resistance.The wave-absorbing coating coating thickness prepared by the present application is 10mm, in 2-18GHz frequency range, wherein ≤-10dB absorption bandwidth is more than 11.6GHz, while meeting the neutral salt spray condition after 1200h, reflectivity change is ±5%, can improve the environmental adaptability and life of wave-absorbing coating.

Description

Technical Field

[0001] This invention relates to the fields of nano-absorbing material preparation and marine environment absorbing coating preparation technology, and in particular to a lightweight marine environment absorbing coating and its preparation method. Background Technology

[0002] With the continuous advancement of radar detection technology, there is an urgent need for lightweight, marine-resistant radar-absorbing stealth coatings to enhance the survivability and deep-strike capabilities of naval weapons and equipment on the battlefield.

[0003] Based on their loss mechanisms, microwave absorbing materials can be classified into three main categories: resistive loss, dielectric loss, and magnetic loss. Among commonly used microwave absorbing materials, magnetic loss materials primarily absorb electromagnetic waves through resonant absorption via a dynamic magnetization process. Typical magnetic loss materials include ferrites, iron-nickel-based materials, and carbonyl iron. They are characterized by strong absorption capacity and ease of application. However, they suffer from poor weather resistance, especially in harsh marine environments where corrosion easily leads to a decline in absorption performance. Existing solutions primarily enhance corrosion resistance by coating with absorbing agents, but this method is complex, difficult to operate, and reduces the stealth performance of the material. It also suffers from narrow absorption bandwidth, high coating density, and poor environmental stability. Common dielectric loss materials include silicon nitride, aluminum silicate, and barium titanate. They lose electromagnetic waves through the polarization relaxation of the dielectric. Because their absorption effect is not ideal under normal conditions, they usually require modification through doping to prepare composite absorbing materials.

[0004] Single-type absorbing agents are insufficient to meet the requirements of naval equipment for broadband, reflectivity, and impedance matching. From the design perspective of absorbing coatings, the selection of absorbing agents for marine environments should fully consider their resistance to salt spray, exposure to sunlight, damp heat aging, and lightweight properties. Strong absorption and broadband effects can be achieved by utilizing materials with different loss mechanisms to absorb electromagnetic waves of different frequencies. Adding a combination of materials with multiple absorbing loss mechanisms to a matrix resin to prepare marine-resistant coatings is a novel technical approach. However, the significant density differences between different types of absorbing agents often lead to uneven dispersion of the two agents in the matrix, thus affecting the stability and broadband performance advantages of the absorbing coating. Furthermore, existing absorbing materials, when facing harsh marine environments, cannot simultaneously address the issues of stable stealth performance and long service life, and suffer from significant degradation in stealth performance. Summary of the Invention:

[0005] This invention discloses a lightweight, marine-resistant absorbing coating and its preparation method, in order to solve any of the above-mentioned and other potential problems in the prior art.

[0006] To address the problems existing in the prior art, the technical solution adopted in this invention is: a lightweight marine-resistant wave-absorbing coating, which includes a nano-lightweight wave-absorbing agent coating pre-dispersion, a nano-dielectric loss type heavy-density wave-absorbing agent, and a curing agent;

[0007] The mass ratio between the light-density microwave absorbing agent pre-dispersion and the nano-dielectric loss type heavy-density microwave absorbing agent is between 100:5 and 30; the mass ratio between the curing agent and the nano-light-density microwave absorbing agent coating pre-dispersion is between 0.1 and 1.5:100.

[0008] Furthermore, the sheet resistance of the absorbing coating is 10. 5 ~10 7 Ohms per square.

[0009] Furthermore, the mass percentage of each component in the nano-lightweight microwave absorbing agent coating pre-dispersion is as follows:

[0010] High-purity, highly crystalline carbon-encapsulated single-walled carbon nanotube microwave absorber, 3%–15%;

[0011] Resin matrix 8%–40%;

[0012] Dispersant 2%–10%;

[0013] Organic solvents 8%–18%

[0014] Leveling agent 0.5%–2%;

[0015] Thickener 3%–18%,

[0016] And the sum of the mass percentages of all components is 100%.

[0017] Furthermore, the high-purity, highly crystalline carbon-coated single-walled carbon nanotube microwave absorber is a lightweight, high-purity, highly crystalline carbon-coated single-walled carbon nanotube microwave absorber material with a carbon content greater than 90%; the high-purity, highly crystalline carbon-coated single-walled carbon nanotube microwave absorber has a real part of dielectric constant of 1.5-16, a dielectric loss of 0.01-0.7, and a carbon particle size of 3-60 nm.

[0018] Furthermore, the matrix resin is at least one of glycidyl ether epoxy resin, glycidyl ester epoxy resin, silicone-modified epoxy resin, acrylic resin, and modified acrylic epoxy resin.

[0019] Furthermore, the dispersant is a combination of one or more of polyethylene wax, sodium dodecylbenzenesulfonate, dodecyltrimethylammonium bromide, and polyethylene glycol;

[0020] Furthermore, the organic solvent is at least one selected from ethanol, xylene, butyl acetate, n-butanol, and ethylene glycol butyl ether;

[0021] The thickener is at least one of fumed nano silica powder with a specific surface area of ​​150-500 m2 / g (Evonik Degussa), gum arabic, and organobentonite.

[0022] The leveling agent is one or more of cellulose acetate butyrate, polydimethylsiloxane, acrylate copolymers, polyester-modified polydimethylsiloxanes, urea-formaldehyde, BYK-333, TBEK-750, or FY-3300.

[0023] Furthermore, the nano-dielectric loss type microwave absorber is one or more of silicon carbide, nano zinc oxide, nano barium titanate, and nano silicon carbide;

[0024] The curing agent is one of the following: polyamide, aromatic diamine, aliphatic amine, polyether amine, and alicyclic amine curing agents.

[0025] Another object of the present invention is to provide a method for preparing the above-mentioned microwave absorbing coating, the method specifically comprising the following steps:

[0026] S1) Preparation of nano-light-density microwave absorbing agent coating pre-dispersion;

[0027] S2) At a speed of 500-3000 rpm, the dielectric loss type heavy density absorber is added to the light density microwave absorbing agent coating pre-dispersion obtained in S1) at a mass ratio of 100:5-30 and stirred at high speed for 0.5-12 hours to obtain the composite microwave absorbing coating pre-dispersion.

[0028] S3) Add the curing agent to the pre-dispersion of the composite microwave absorbing coating obtained in S2) and mix thoroughly to obtain a lightweight microwave absorbing coating suitable for marine environments.

[0029] Furthermore, the specific steps of S1) are as follows:

[0030] S1.1) Weigh each component according to the designed formula amount. First, slowly add the high-purity, highly crystalline carbon-encapsulated single-walled carbon nanotube microwave absorber to the organic solvent while stirring and mixing. The stirring speed is 300-3000 rpm and the time is 1-5 hours to obtain a mixed solution.

[0031] S1.2) Add resin matrix and dispersant to the mixed solution obtained in S1.1) and stir to mix. Grind in a sand mill at 500-3500 rpm for 2-10 hours to obtain a mixed liquid.

[0032] S1.3) Add the mixed liquid obtained in S1.2) to a mixing tank, add the leveling agent and thickener in the formula in sequence, and stir thoroughly for 1-8 hours. Adjust the viscosity of the system to 300-1350 mpa.s to obtain the nano-light density microwave absorbing agent coating pre-dispersion.

[0033] Furthermore, when the coating thickness of the lightweight marine-resistant absorbing coating is 10 mm, the reflectivity is within the 2-18 GHz frequency band, the absorption bandwidth of ≤-10 dB exceeds 11.6 GHz, and the reflectivity change is within ±5% after 1200 h under neutral salt spray conditions.

[0034] Explanation of the principle:

[0035] Carbon nanotubes (CNTs) possess excellent electrical conductivity, resulting in a certain resistance loss when incident electromagnetic waves are emitted. Furthermore, based on the macroscopic quantum tunneling effect, CNTs exhibit split electronic energy levels, with the energy level spacing falling within the energy range of microwaves. Under microwave irradiation, the accelerated movement of atoms and electrons induces magnetization, converting electronic energy into heat energy and thus attenuating electromagnetic waves. More importantly, carbon nanotubes possess a plasmonic resonance frequency with absorption peaks. The plasmonic resonance frequency shift exhibited by the CNT absorption peaks can be controlled by adjusting the size to regulate the absorption bandwidth.

[0036] The electromagnetic wave absorption characteristics of carbon nanotubes are closely related to their chemical composition, diameter, and growth process. Single-walled carbon nanotubes can be prepared in situ using chemical vapor deposition (CVD), high-temperature plasma methods, or arc discharge methods. The catalyst precursor contains four components: catalyst, co-catalyst, liquid hydrocarbon solvent, and oxidant. Ferrocene is preferred as the catalyst, thiophene as the co-catalyst to limit the growth of nanocatalyst particles, and anhydrous ethanol serves not only as the liquid hydrocarbon solvent to dissolve the catalyst and co-catalyst but also as the first-phase carbon source required for growth. Pure water is preferred as the weak oxidant. The evaporation of pure water in the high-temperature region serves two purposes: firstly, it etches the amorphous carbon formed by the decomposition of the generated carbon source; secondly, it etches the carbon shell of the carbon-coated iron layer, ensuring high crystallinity of the grown carbon-coated single-walled carbon nanotubes, making them difficult to oxidize and decompose at low temperatures. By adding a second-phase carbon source, highly crystalline carbon-coated magnetic single-walled carbon nanotubes with specific structures can be prepared in situ using CVD. The first-phase liquid hydrocarbon carbon source plays a growth role, while the second-phase gaseous carbon source mainly generates highly crystalline carbon to effectively encapsulate the catalyst particles. Therefore, by restricting the location of the carbon source, more highly crystalline carbon-coated magnetic single-walled carbon nanotube materials can be grown.

[0037] This material possesses both magnetic and electrical loss characteristics. Furthermore, after further high-temperature calcination and acid washing pretreatment, the material becomes purer, and its stability and uniformity are greatly improved. It can maintain long-term relative stability under extreme salt spray, exposure to sunlight, and humid heat aging without significantly affecting its microwave absorption performance.

[0038] Furthermore, due to its low content, it needs to be designed in combination with dielectric loss absorbing materials to achieve absorption over a wider frequency range. Simultaneously, to ensure uniform mixing of the two absorbing agents with significantly different densities, a two-step pre-dispersion process is used for mixing to achieve homogeneity. This nanocomposite absorbing agent, possessing three loss mechanisms, can withstand harsh marine environments while addressing both stable stealth performance and long service life.

[0039] In summary, this invention prepares a material with a specific structure and highly crystalline carbon-coated single-walled carbon nanotubes in situ by adding a second-phase carbon source. Pretreatment removes some easily exposed and poorly crystalline amorphous carbon, resulting in a high-purity, highly crystalline carbon-encapsulated single-walled carbon nanotube material with a lightweight absorbing agent. This material is first dispersed in a resin matrix to form a nano-lightweight absorbing agent coating pre-dispersion, then mixed with a dielectric loss type heavy-density absorbing agent, and dispersed in a two-step process to prepare a uniform absorbing coating. Furthermore, by optimizing the ratio of the two absorbing agents, a lightweight absorbing coating suitable for marine environments is prepared. The material prepared using this method not only improves the corrosion resistance of the absorbing material but also reduces its surface density and broadens its absorption bandwidth.

[0040] The beneficial effects of this invention are:

[0041] (1) This invention utilizes in-situ prepared highly crystalline carbon-encapsulated nanomagnetic single-walled carbon nanotubes to prepare a low-density microwave absorbing agent coating pre-dispersion, which is then compounded with a nano-dielectric loss type high-density absorber. Combining the advantages of both, a composite microwave absorbing coating is designed based on the principle of microwave absorbing agent loss, achieving strong absorption over a wide frequency range. Experiments show that the absorption peak intensity of a 10 mm thick coating prepared using this microwave absorbing agent exceeds -18 dB, and the absorption bandwidth of less than or equal to -10 dB exceeds 11.6 GHz.

[0042] (2) The present invention includes pretreatment of the prepared in-situ highly crystalline carbon-encapsulated nanomagnetic single-walled carbon nanotube lightweight microwave absorbing agent to obtain a high-purity, highly crystalline carbon-encapsulated single-walled carbon nanotube material lightweight microwave absorbing agent. The prepared microwave absorbing coating has better corrosion resistance and more stable performance, while meeting the requirement that the reflectivity change is within ±5% after 1200h under neutral salt spray conditions, and the reflectivity stability is good.

[0043] (3) The lightweight marine-resistant absorbing coating of the present invention, in order to achieve uniform mixing of two absorbing agents with large density differences, uses a two-step method to prepare a pre-dispersion for mixing, thereby achieving uniformity. Furthermore, the ratio of the two absorbing agents is optimized to prepare a lightweight marine-resistant absorbing coating. A two-step method is employed. This nanocomposite absorbing agent, which combines three loss mechanisms, can withstand harsh marine environments and addresses both the issues of stable stealth performance and long service life.

[0044] (4) The microwave absorbing coating obtained by using the microwave absorbing coating prepared by the present invention can withstand more than 1200 hours in neutral salt spray and more than 300 hours in acidic salt spray (pH 3.5);

[0045] (5) The microwave absorbing coating of the present invention has a low surface density under certain thickness conditions. When the coating thickness is 1 mm, the surface density can be only 1.0-1.3 kg / m³. 2 This meets the performance requirements of "light and thin" for absorbing coatings. Attached Figure Description

[0046] Figure 1 This is a flowchart of a lightweight marine-resistant wave-absorbing coating and its preparation method according to the present invention.

[0047] Figure 2 The dielectric constant of the high-purity, highly crystalline carbon-encapsulated single-walled carbon nanotube microwave absorber in the present invention is shown in the X-band.

[0048] Figure 3 This is a dielectric loss diagram of the high-purity, highly crystalline carbon-encapsulated single-walled carbon nanotube microwave absorber in the X-band of this invention.

[0049] Figure 4 Thermogravimetric analysis (TGA) of the high-purity, highly crystalline carbon-encapsulated single-walled carbon nanotubes used in Example 3 of this invention.

[0050] Figure 5 This is a scanning electron microscope image of a highly crystalline carbon-encapsulated single-walled carbon nanotube used in Example 1 of the present invention.

[0051] Figure 6 This is a transmission electron microscope image of a high-purity, highly crystalline carbon-encapsulated single-walled carbon nanotube prepared in Example 1 of this invention.

[0052] Figure 7 This is a scanning electron microscope image of the coating prepared in Example 1 of the present invention.

[0053] Figure 8 The image shows the reflectance of the coatings prepared in Example 3 and Comparative Example 1 of this invention on a flat panel at 2-18 GHz. Detailed Implementation

[0054] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0055] Example 1:

[0056] like Figure 1As shown, the preparation process is as follows: First, a microwave absorbing agent consisting of 4.5% highly crystalline carbon-encapsulated single-walled carbon nanotubes with a purity greater than 92% is slowly added to a 12% ethanol organic solvent while stirring at 1000 rpm for 1.5 hours. Then, a combination of 28% organosilicon-modified epoxy resin, 2% polyethylene wax, and 3% dodecyltrimethylammonium bromide dispersant is added and stirred. The mixture is then ground in a sand mill at 1500 rpm for 2.5 hours. The liquid mixture is then added to a mixing tank, followed by the addition of 1.2% leveling agent polydimethylsiloxane and 6% thickener fumed silica powder with a specific surface area of ​​200-300 m². 2 / g, stir and mix thoroughly for 3 hours, adjust the viscosity of the system to 750-950 mpa.s, and obtain the nano-light-density microwave absorbing agent coating pre-dispersion;

[0057] At a speed of 1200 rpm, silicon carbide, a dielectric loss type heavy density absorber, was added to the obtained light density microwave absorbing agent coating pre-dispersion at a mass ratio of 100:8 and stirred at high speed for 2 hours to obtain the composite microwave absorbing coating pre-dispersion.

[0058] The curing agent polyamide and the composite microwave absorbing agent coating pre-dispersion were thoroughly stirred at a mass ratio of 1.2:100 to obtain a lightweight, marine-resistant microwave absorbing coating. Scanning electron microscopy of the coating showed... Figure 7 As shown, tubular structures are clearly visible.

[0059] At this point, the sheet resistance of the absorbing coating is 5.6*10. 7 Ohms per cubic meter. As shown in Table 1, when the coating thickness of the lightweight, marine-resistant, wave-absorbing coating is 10 mm, the areal density is 1.23 kg / m³. 2 The surface density is low and the reflectivity is -6 to -17 dB in the 2-18 GHz band, -11 to -14 dB in the 4-8 GHz band, and -11 to -14 dB in the 8-18 GHz band.

[0060] In-situ preparation of carbon-coated single-walled carbon nanotubes using chemical vapor deposition, high-temperature plasma methods, or arc discharge methods includes the following steps:

[0061] Inert gas was introduced into the growth zone and the collection zone for venting, and the reaction temperature was raised to the specified temperature of 1350℃.

[0062] A catalyst precursor solution was prepared by mixing four components: 2,2-bis(ethylferrocene)propane as catalyst, dimethyl sulfoxide as co-catalyst with an iron / sulfur molar ratio of 15:1-2:1 in the catalyst precursor, anhydrous ethanol as liquid hydrocarbon solvent accounting for 93.5 wt% of the catalyst precursor, and pure water as 3 wt% of oxidant. The catalyst precursor solution was atomized into droplets with a diameter range of 5-50 micrometers and introduced into the high-temperature growth zone along with a preheated 580°C carrier gas containing 35% hydrogen to carry out the reaction.

[0063] The second-phase carbon source natural gas is preheated to 350℃. The molar ratio of carbon in the second-phase carbon source to carbon in the solvent is 1:9. The injection port is located 3 cm after the atomization port of the catalyst precursor solution. The second-phase carbon source gas and the mixed gas flow react in the growth zone, and the product generated is the highly crystalline carbon-encapsulated single-walled carbon nanotube product.

[0064] The in-situ prepared highly crystalline carbon-encapsulated single-walled carbon nanotube microwave absorber, as shown in the scanning electron microscope image. Figure 5 As shown.

[0065] It requires high-temperature heat treatment and acid washing pretreatment. The specific pretreatment process is as follows: calcination at 500℃ in air for 3 hours, followed by stirring and acid washing with 6M mol / L hydrochloric acid for 12 hours until neutral, yielding a lightweight, high-purity, highly crystalline carbon-encapsulated single-walled carbon nanotube microwave absorber material with a carbon content greater than 90%, and a real part of its dielectric constant of 1.5-2.7. Figure 2 As shown, the dielectric loss is 0.02-0.37, as... Figure 3 As shown, the carbon particles have a diameter of 3-60 nm, and are composed of... Figure 6 Transmission electron microscopy characterization revealed that arrow B represents a highly crystalline carbon-encapsulated nanomagnetic catalyst (arrow A), while arrow C represents a single-walled carbon nanotube.

[0066] Example 2:

[0067] The difference in the process method of Example 1 is that the crystalline carbon-encapsulated single-walled carbon nanotubes, with a purity greater than 95% and a proportion of 9.5%, are stirred in 15% ethanol organic solvent at a stirring speed of 2000 rpm for 2.5 hours; the 35% organosilicon-modified epoxy resin, 3% polyethylene wax, and 5% sodium dodecylbenzenesulfonate combined dispersant are stirred and mixed; the mixed liquid is added to a stirring tank, and 1.0% of leveling agent polydimethylsiloxane and 12% of thickener fumed silica powder are added sequentially to obtain the nano-light-density microwave absorbing agent coating pre-dispersion; the dielectric loss type heavy-density absorber nano-barium carbonate silicon and the light-density microwave absorbing agent coating pre-dispersion are stirred at high speed at a mass ratio of 100:15 to obtain the composite microwave absorbing coating pre-dispersion.

[0068] The curing agent polyamide and the composite microwave absorbing agent coating pre-dispersion were thoroughly stirred at a mass ratio of 1.4:100 to obtain a lightweight, marine-resistant microwave absorbing coating. At this point, the sheet resistance of the microwave absorbing coating was 5.6 × 10⁻⁶. 6 Ohms per cubic meter. As shown in Table 1, when the coating thickness of the lightweight, marine-resistant, wave-absorbing coating is 10 mm, the surface density is 1.18 kg / m³. 2 The surface density is lower than that of Example 1, and the reflectivity is -1.5 to -10 dB in the 2-18 GHz frequency band, -5 to -17 dB in the 4-8 GHz range, and -9 to -15 dB in the 8-18 GHz range.

[0069] Example 3:

[0070] The difference in the process method used in Example 1 is that the crystalline carbon-encapsulated single-walled carbon nanotubes have a purity greater than 98%, see [link to example]. Figure 4 The thermogravimetric characterization (TGA) of high-purity, highly crystalline carbon-encapsulated single-walled carbon nanotubes is shown. The residual TG mass is 0.32%, and the carbon content is close to 99.68%, indicating high product purity. As shown in the figure, the product begins to decompose at a high temperature of 538.3℃ and only completely decomposes at 883.1℃, indicating high thermal stability. The product accounts for 14.5% of the total content. In a 16% ethanol organic solvent, the stirring speed is 1600 rpm for 3.5 hours. Then, 38% organosilicon-modified epoxy resin, 2.5% polyethylene wax, and 6.5% sodium dodecylbenzenesulfonate combined dispersant are added and stirred. The dielectric loss type heavy density absorber nano-barium carbonate silicon and the light density microwave absorbing agent coating pre-dispersion are stirred at high speed at a mass ratio of 100:26 to obtain the composite microwave absorbing coating pre-dispersion.

[0071] The curing agent polyamide and the composite microwave absorbing agent coating pre-dispersion were thoroughly stirred at a mass ratio of 1.1:100 to obtain a lightweight, marine-resistant microwave absorbing coating. At this point, the sheet resistance of the microwave absorbing coating was 2.1 × 10⁻⁶. 5 Ohms per cubic meter. As shown in Table 1, when the coating thickness of the lightweight, marine-resistant, wave-absorbing coating is 10 mm, the surface density is 1.03 kg / m³. 2 The reflectance is significantly lower than that of Examples 1 and 2. The reflectance is within the 2-18 GHz frequency band: -2.8 to -11 dB in the 2-4 GHz range, -8 to -18.6 dB in the 4-8 GHz range, and -12 to -14.5 dB in the 8-18 GHz range. At this time, the frequency and reflectance curves before the salt spray test are as follows... Figure 8 As shown, the absorption peak intensity of the prepared 10 mm thick coating exceeds -18 dB, and the absorption bandwidth of less than or equal to -10 dB exceeds 11.6 GHz.

[0072] Comparative Example 1

[0073] The lightweight marine-resistant absorbing coating prepared in Example 3 was exposed to a salt spray test chamber (5% NaCl solution spray) for 1200 hours. Afterward, the sample was removed and its plate reflectance was tested. Figure 8 The table shows a comparison of reflectance before and after the salt spray experiment. As shown in Table 1, the density remained essentially unchanged before and after the salt spray experiment.

[0074] According to the data above, the corrosion-resistant microwave absorbing coating prepared by this invention can remain intact after 1200 hours of salt spray testing without corrosion, demonstrating good corrosion resistance and waterproof performance. It also meets the requirement that the reflectivity change is within ±5% after 1200 hours under neutral salt spray conditions and can withstand more than 300 hours in acidic salt spray (pH 3.5), exhibiting excellent microwave absorption performance and broad application prospects.

[0075] Table 1. Performance comparison of samples prepared in the examples and comparative examples.

[0076]

[0077] Performance testing methods

[0078] (1) Reflectivity test method: Refer to the national standard GJB 2038A-2011, and use the reflectivity-bow method to test the reflectivity of the examples and comparative examples in the frequency range of 2 to 18 GHz. Test conditions: electromagnetic waves are incident perpendicularly. Sample preparation refers to GB / T 1727-92, and sample collection refers to GB 3186-1982.

[0079] (2) Coating thickness test method: Refer to GB / T 1727-92, control the mass of the coating product to be 10g each time the sample is prepared, dry at room temperature for 24h, prepare the coating products obtained from the examples and comparative examples into standard test samples, and determine the thickness of the test samples according to the national standard GB / T13452.2-92.

[0080] (3) The corrosion resistance test was conducted using the salt spray test method. The test method was as follows: the sample of Example 3 was exposed to the spray of 5% NaCl solution in the salt spray test chamber. After 1200 hours, the sample was taken out and the reflectivity of the plate was tested.

[0081] (4) For the Raman spectroscopy, thermogravimetric characterization, scanning electron microscopy and energy-dispersive X-ray spectroscopy and transmission electron microscopy characterization methods for high-quality single-walled carbon nanotube samples, please refer to GB / T 32871-2016, GB / T24490-2009 and GB / T 32869-2016.

[0082] The foregoing has provided a detailed description of a lightweight, marine-resistant microwave-absorbing coating and its preparation method, as provided in the embodiments of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this application; furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

[0083] Certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising / including but not limited to". "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error. The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of illustrating the general principles of this application and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0084] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.

[0085] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0086] The foregoing description illustrates and describes several preferred embodiments of this application. However, as previously stated, it should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be within the protection scope of the appended claims.

Claims

1. A lightweight, marine-resistant wave-absorbing coating, characterized in that, The microwave absorbing coating comprises a nano-light-density microwave absorbing agent coating pre-dispersion, a nano-dielectric loss type heavy-density microwave absorbing agent, and a curing agent; The mass ratio between the light-density microwave absorbing agent pre-dispersion and the nano-dielectric loss type heavy-density microwave absorbing agent is between 100:5 and 30; the mass ratio between the curing agent and the nano-light-density microwave absorbing agent coating pre-dispersion is between 0.1 and 1.5:

100. Furthermore, the sheet resistance of the absorbing coating is 10. 5 ~10 7 Ohms per square; The mass percentages of each component in the nano-lightweight microwave absorber coating predispersant are as follows: High-purity, highly crystalline carbon-encapsulated single-walled carbon nanotube microwave absorber, 3%~15%; Resin matrix 8%~40%; Dispersant 2%~10%; Organic solvents 8%~18% Leveling agent 0.5%~2%; Thickener 3%~18%, And the sum of the mass percentages of all components is 100%; The high-purity, highly crystalline carbon-coated single-walled carbon nanotube microwave absorber is a lightweight, high-purity, highly crystalline carbon-coated single-walled carbon nanotube microwave absorber material with a carbon content greater than 90%; the high-purity, highly crystalline carbon-coated single-walled carbon nanotube microwave absorber has a real part of dielectric constant of 1.5-16, a dielectric loss of 0.01-0.7, and a carbon particle size of 3-60 nm.

2. The microwave absorbing coating according to claim 1, characterized in that, The resin matrix is ​​at least one of glycidyl ether epoxy resin, glycidyl ester epoxy resin, silicone-modified epoxy resin, acrylic resin, and modified acrylic epoxy resin.

3. The microwave absorbing coating according to claim 1, characterized in that, The dispersant is a combination of one or more of polyethylene wax, sodium dodecylbenzenesulfonate, dodecyltrimethylammonium bromide, and polyethylene glycol.

4. The microwave absorbing coating according to claim 1, characterized in that, The organic solvent is at least one selected from ethanol, xylene, butyl acetate, n-butanol, and ethylene glycol butyl ether. The thickener is fumed silica nanoparticles with a specific surface area of ​​150-500 m². 2 / g, gum arabic, and at least one of organic bentonite; The leveling agent is one or more of the following: cellulose acetate butyrate, polydimethylsiloxane, acrylate copolymers, polyester-modified polydimethylsiloxanes, urea-formaldehyde, and BYK-333.

5. The microwave absorbing coating according to claim 1, characterized in that, The nano-dielectric loss type microwave absorber is one or more of nano zinc oxide, nano barium titanate, and nano silicon carbide. The curing agent is one of the following: polyamide, aromatic diamine, aliphatic amine, polyether amine, and alicyclic amine curing agents.

6. A method for preparing the microwave absorbing coating as described in any one of claims 1-5, characterized in that, The method specifically includes the following steps: S1) Preparation of nano-light-density microwave absorbing agent coating pre-dispersion; S2) At a speed of 500-3000 rpm, the dielectric loss type heavy density absorber is added to the light density microwave absorbing agent coating pre-dispersion obtained in S1) at a mass ratio of 100:5-30 and stirred at high speed for 0.5-12 hours to obtain the composite microwave absorbing coating pre-dispersion. S3) Add the curing agent to the pre-dispersion of the composite microwave absorbing coating obtained in S2) and mix thoroughly to obtain a lightweight microwave absorbing coating suitable for marine environments.

7. The method according to claim 6, characterized in that, The specific steps of S1 are as follows: S1.1) Weigh each component according to the designed formula amount. First, slowly add the high-purity, highly crystalline carbon-encapsulated single-walled carbon nanotube microwave absorber to the organic solvent while stirring and mixing. The stirring speed is 300-3000 rpm and the time is 1-5 hours to obtain a mixed solution. S1.2) Add resin matrix and dispersant to the mixed solution obtained in S1.1) and stir to mix. Grind in a sand mill at 500-3500 rpm for 2-10 hours to obtain a mixed liquid. S1.3) Add the mixed liquid obtained in S1.2) to a mixing tank, and add the leveling agent and thickener in the formula in sequence. Stir and mix thoroughly for 1-8 hours, and adjust the viscosity of the system to 300-1350 mpa.s to obtain the nano-light density microwave absorbing agent coating pre-dispersion.

8. The method according to claim 6, characterized in that, When the coating thickness of the lightweight marine-resistant absorbing coating is 10 mm, the reflectivity is in the 2-18 GHz frequency band, and the absorption bandwidth of ≤-10 dB exceeds 11.6 GHz. It can simultaneously meet the requirement that the reflectivity change is within ±5% after 1200 h under neutral salt spray conditions.

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