A microwave-absorbing coating based on rGO aerogel loaded with transition metal carbide and its preparation method and application

Abstract

A radar-absorbing coating based on rGO aerogel-loaded transition metal carbide, and its preparation method and application, comprises: Component A: a film-forming resin, a rheological additive, a composite absorber, a leveling agent, a dispersant, a defoamer, and a solvent; and Component B: a curing agent. The composite absorber is prepared by adding a mixture of ascorbic acid, deionized water, and ethanol to an aqueous solution of graphene oxide, performing a pre-reduction-freeze-thaw-re-reduction-freeze-drying process to obtain rGOA, which is then removed for later use; adding a transition metal salt solution to an acidic aqueous solution of dopamine hydrochloride to obtain a mixed solution, and then completely immersing the obtained rGOA in the mixed solution. After the reaction, the mixture is washed, vacuum-dried overnight, and finally calcined in an inert atmosphere. The present invention packs TMC nanoparticles into the rich three-dimensional pore structure of the rGOA, resulting in a coating with advantages such as light weight, corrosion resistance, a wide absorption band, and strong absorption capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of radar wave absorbing coatings, and in particular to a radar wave absorbing coating based on rGO aerogel loaded with transition metal carbides, and a preparation method and application thereof. Background Art

[0002] Current radar-absorbing coatings suffer from issues such as heavy weight, a narrow effective absorption band, thick coatings, and weak absorption capacity. Furthermore, poor corrosion resistance and high-temperature resistance significantly limit their widespread application. Therefore, developing a radar-absorbing coating that combines both excellent corrosion resistance and radar absorption properties is crucial.

[0003] Currently, reported radar-absorbing coatings primarily consist of four components: a binder, an absorbent, an additive, and a diluent. The absorbent, acting as an absorbent filler, is crucial. Currently used absorbing fillers primarily include ferrite, carbonyl iron powder, carbon materials, magnetic metals, and magnetic metal oxide powders. Chinese patent publication CN 103725073 B discloses a stealth coating, specifically a method for preparing a nanoscale radar-absorbing coating. The method involves uniformly dispersing and mixing a film-forming resin, a solvent, an additive, and nanoscale alumina, ferrosoferric oxide, carbonyl iron powder, cobalt oxide, and graphite in a specific proportion. This yields a wide-bandwidth, highly compatible, and thin absorbing coating. However, the high density of this absorbing filler significantly increases the load, thus significantly limiting its application. Chinese patent application publication number CN 117720835 A discloses a lightweight radar absorbing material and its application coating. The modified absorber is prepared by blending a core-shell magnet with deposited strontium oxide directionally adsorbed on the surface of ferroferric oxide with a coating emulsion consisting of polycarbonate polyol, diisocyanate, and a catalyst. The coating is then made by adding 25-30% film-forming resin and 0-15% additives to form a radar absorbing coating. This coating achieves both lightweight and radar protection. However, the preparation method of the modified absorber is extremely complex, making it difficult to produce and apply on a large scale.

[0004] Composite absorbers have experienced rapid development in recent years, primarily due to their unique magnetoelectric synergy, which enables excellent impedance matching. This results in strong, broadband absorption, combined with lightweight, corrosion-resistant, and high-temperature resistant properties. Traditional composite absorbers typically utilize low-dielectric materials such as ceramics, magnetic materials, and semiconductors to modify a highly conductive substrate. With the continuous advancement of materials science, transition metal carbides (TMCs) have attracted significant attention in the field of absorbent coatings due to their high hardness, mechanical stability, excellent thermal stability, corrosion resistance, and, in particular, their exceptional metal-like conductivity. Furthermore, reduced graphene oxide aerogel (rGOA) is an excellent lightweight dielectric matrix material due to its high porosity, low density, and suitable electrical conductivity. Its well-developed pore structure not only facilitates the penetration of electromagnetic waves into the aerogel, optimizing impedance matching, but also increases multiple reflections and scattering within the aerogel, thereby facilitating electromagnetic wave attenuation.

[0005] In view of this, the present invention cleverly fills TMCs nanoparticles into the rich three-dimensional pore structure of rGOA (TMCs / rGOA), realizing a clever compound of transition metal carbides and carbon materials, which is expected to realize a new radar wave absorbing material that is lightweight, has strong absorption capacity and is corrosion-resistant. Summary of the Invention

[0006] Technical problem to be solved: In response to the problems of existing radar wave absorbing coatings, such as high density of absorbing fillers, weak absorption capacity and poor corrosion resistance of the absorbing coating, the present invention proposes an absorbing coating based on rGO aerogel loaded with transition metal carbides, as well as its preparation method and application. The coating prepared by the present invention has the advantages of light weight, corrosion resistance, wide absorption band and strong absorption capacity.

[0007] Technical solution: The first object of the present invention is to provide an absorbing coating based on rGO aerogel loaded with transition metal carbides, comprising component A and component B. Component A is formulated as follows by mass: 25-50 parts of a film-forming resin, 0.1-10 parts of a rheological additive, 30-70 parts of a composite absorber, 0.1-3.0 parts of a leveling agent, 0.1-2.0 parts of a dispersant, 0.1-4 parts of a defoamer, and 4-20 parts of a solvent; component B is a curing agent, and the mass ratio of component A to component B is (3-10):1. The composite absorber in component A is prepared as follows:

[0008] Step 1, preparation of rGOA: Add an ascorbic acid aqueous solution with a concentration of 6-20 mg / mL to an aqueous solution of graphene oxide with a concentration of 2-20 mg / mL, shake for 5-10 minutes, then add ethanol, shake again for 3-7 minutes, seal in a glass bottle, pre-reduce in an oven, then transfer to a freeze dryer for freezing, take out for thawing, then transfer to an oven for reduction, and finally vacuum dry in a freeze dryer to obtain rGOA for use, wherein the volume ratio of the graphene oxide aqueous solution to the ascorbic acid aqueous solution is 1:(2-6), and the volume ratio of ethanol to the ascorbic acid aqueous solution is 1:(3-8);

[0009] Step 2. Preparation of TMCs / rGOA composite absorber: Add a 0.1 mol / L transition metal salt solution to a 0.1 mol / L dopamine hydrochloride aqueous solution in a volume ratio of 1:(1-3), and adjust the pH to 2-4 with hydrochloric acid. Then, completely immerse the rGOA aerogel obtained in step 1 in the above-mentioned mixed solution. After the reaction, wash the aerogel several times with deionized water and ethanol alternately, dry it in a vacuum oven overnight, and finally calcine it in an inert atmosphere to obtain an rGOA-loaded TMCs composite absorber.

[0010] Preferably, in step 1, the pre-reduction oven temperature is 85-95°C, the pre-reduction time is 20-40 min; the freezing temperature is -35~-45°C, the freezing time is 30-40 min; the re-reduction temperature is 85-95°C, the re-reduction time is 4-6 h; the vacuum drying temperature in the freeze dryer is -60~-75°C, and the drying time is 18-36 h.

[0011] Preferably, the transition metal in step 2 is iron, cobalt, nickel, tungsten, molybdenum, zirconium, niobium or vanadium.

[0012] Preferably, the immersion time in step 2 is 1-3 h; the number of alternating washings is 3-6 times; the temperature for drying overnight in a vacuum oven is 50-70° C.; and the calcination in an inert atmosphere is specifically as follows: the inert atmosphere is nitrogen or argon, the heating rate is 3-6° C. / min, the calcination temperature is 800-1100° C., and the calcination time is 3-5 h.

[0013] Preferably, the film-forming resin is at least one of an acrylic polyurethane resin and a fluorocarbon resin.

[0014] Preferably, the curing agent is an isocyanate curing agent.

[0015] Preferably, the rheological additive is at least one of bentonite, fumed silica, polyamide wax and polyethylene wax.

[0016] The leveling agent, dispersant, and defoaming agent are commonly used in the industry and are suitable for coating-related products such as acrylic polyurethane resin and fluorocarbon resin, and are well known to those skilled in the art.

[0017] Preferably, the leveling agent is at least one of TEGO-300, TEGO-375, TEGO-370 from Evonik, Germany, BYK-329, BYK-342, BYK-354, BYK-325N, BYK-358, NBYK-320, BYK-355 and BYK-306 from BYK; the dispersant is at least one of BYK-118, BYK-130, BYK-110, BYK-111, BYK-161, BYK- The defoaming agent is at least one of BYK-066N, BYK-088, BYK-067A, BYK-085, BYK-141, BYK-070 from BYK Chemicals, and DC-7, ACP-0544, 1430 and AFE-0120 from Dow Corning.

[0018] Preferably, the solvent is at least one of butanol, toluene, butyl acetate, xylene, cyclohexane, ethyl acetate and solvent oil.

[0019] A second object of the present invention is to provide a method for preparing the above-mentioned rGO aerogel-loaded transition metal carbide-based radar-absorbing coating, comprising the following steps: adding a film-forming resin, a first solvent, and a dispersant to a paint mixing tank and dispersing them uniformly; adding a rheological additive and dispersing them at a speed of 2000 r / min for 15 minutes; adding a composite radar-absorbing agent and continuing to disperse them at a speed of 2000 r / min for 1 hour; then adding a leveling agent, a defoaming agent, and a second solvent, wherein the mass ratio of the first solvent to the second solvent is (2.5-5):1; dispersing at a speed of 1500 r / min for 15 minutes to obtain component A; and uniformly mixing component A with component B for use.

[0020] A third object of the present invention is to provide an application of the above-mentioned rGO aerogel-loaded transition metal carbide-based absorbing coating in the preparation of a radar wave absorbing coating. The specific application process is as follows: the rGO aerogel-loaded transition metal carbide-based absorbing coating is sprayed onto a metal plate and dried and cured at 25°C for 4-8 hours to obtain a dry film thickness of 1000 μm to obtain a radar wave absorbing coating.

[0021] Beneficial effects:

[0022] (1) The present invention provides a method for preparing a TMCs / rGOA composite absorber. During the rGOA preparation process, a pre-reduction-freeze-thaw-re-reduction-freeze-drying strategy is used to achieve the regulation of the internal pore structure of the aerogel. The pre-reduction-freeze-thaw process can avoid excessive shrinkage during gel formation, allowing the aerogel to obtain a richer pore structure and a larger specific surface area, thereby greatly optimizing the impedance matching of the absorber. In addition, pre-reduction can greatly reduce the degree of reduction of graphene oxide, allowing the graphene surface to retain sufficient functional groups such as hydroxyl and carboxyl groups, providing more chemical binding sites for the growth of transition metal carbide precursors.

[0023] (2) The present invention uses a simple impregnation strategy to make the transition metal carbide precursor grow uniformly inside the rGOA pore structure, thereby obtaining a lightweight, highly absorbing, and corrosion-resistant composite absorbing filler. The synthesis method is simple and easy, reduces energy consumption, and saves preparation costs.

[0024] (3) The present invention regulates the composition by controlling the calcination temperature, introducing a multi-layered heterogeneous structure to enhance heterogeneous interface polarization and defect polarization, thereby enhancing the radar wave absorption capability of the coating. In addition, the TMCs / rGOA composite absorber has good dispersibility in the resin, and the rGO nanosheets greatly hinder the entry of the electrolyte. The excellent chloride ion pitting resistance of TMCs and the synergistic effect of multiple interfaces also slow the entry of the electrolyte, providing the absorbing coating with excellent corrosion resistance. DETAILED DESCRIPTION

[0025] In order to make the technical solutions, advantages and objectives of the present invention clearer and more specific, the present invention is described in detail below through specific embodiments. The embodiments are merely illustrative and do not limit the scope of protection of the patent of the present invention. Any non-essentially equivalent changes or adjustments made based on the above-mentioned invention content and spirit are within the scope of protection of the present invention.

[0026] Unless otherwise specified, all raw materials used in the examples of this specification are from common commercially available products.

[0027] Graphene oxide was purchased from Xianfeng Nanomaterials Technology Co., Ltd. with a flake diameter of 5-10 μm;

[0028] Ascorbic acid was purchased from Shanghai Aladdin Company with a purity of ≥99%;

[0029] The transition metal salt was Na2WO4·2H2O, purchased from Shanghai Aladdin Company, with a purity of ≥99.5%;

[0030] Dopamine hydrochloride was purchased from Shanghai Aladdin Company with a purity of ≥98%;

[0031] The film-forming resin was acrylic polyurethane resin, purchased from Dongsheng Chemical Co., Ltd.

[0032] The rheological additive was bentonite, purchased from Zhejiang Fenghong New Materials Co., Ltd.

[0033] The leveling agent was TEGO-300, purchased from Evonik, Germany;

[0034] The dispersant was BYK-163, purchased from BYK-Chemie GmbH, Germany;

[0035] The defoamer was BYK-141, purchased from BYK Chemical Co., Ltd., Germany;

[0036] Solvents were xylene and butyl acetate, purchased from Shanghai Aladdin Company;

[0037] The isocyanate curing agent was HT-100, purchased from Wanhua Chemical.

[0038] Example 1

[0039] This embodiment is a method for preparing an absorbing coating based on rGO aerogel loaded with transition metal carbides. The specific steps are as follows:

[0040] (1) Preparation of WC (tungsten carbide) / rGOA composite absorber:

[0041] 24 mL of 12.8 mg / mL ascorbic acid solution was added to 12 mL of 10 mg / mL graphene oxide aqueous solution. After vibrating thoroughly for 5 min, 8 mL of ethanol was added and vibrated again for 3 min. The mixture was sealed in a glass container and placed in a 95°C oven for pre-reduction for 30 min. It was then transferred to a -40°C freeze dryer and frozen for 30 min. After being taken out, it was thawed at room temperature and then placed in a 95°C oven for further reduction for 5 h. Finally, rGOA was obtained after drying in a -60°C freeze dryer for 24 h. It was taken out for use. 50 mL of 0.1 mol / L Na2WO4·2H2O solution was weighed and dissolved in 50 mL of 0.1 mol / L dopamine hydrochloride aqueous solution, and the pH was adjusted to 2 with hydrochloric acid. Then, the prepared rGOA was completely immersed in the above solution. After soaking and reacting for 1 hour, it was washed three times with deionized water and ethanol alternately, and then dried in a 60℃ oven overnight. Finally, it was calcined in a tubular furnace with nitrogen at a heating rate of 5℃ / min and a temperature of 1000℃ for 3 hours to obtain a WC / rGOA composite absorber.

[0042] (2) Preparation of radar-absorbing coating:

[0043] 40 parts by mass of acrylic polyurethane resin, 10 parts by mass of xylene, and 0.1 parts by mass of BYK-163 dispersant were added to a paint mixing can and dispersed evenly. 0.8 parts by mass of bentonite was added and dispersed at a speed of 2000 r / min for 15 minutes. 45 parts by mass of a composite absorber was added and dispersed at a speed of 2000 r / min for 1 hour. 0.1 parts by mass of TEGO-300 leveling agent, 0.5 parts by mass of BYK-141 defoamer, and 3.5 parts by mass of butyl acetate were then added and dispersed at a speed of 1500 r / min for 15 minutes to obtain component A. Component A was then mixed evenly with component B (HT-100 curing agent) in a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel-loaded WC.

[0044] (3) Preparation of microwave absorbing coating:

[0045] The absorbing coating based on rGO aerogel loaded with WC obtained in step (2) was sprayed on a metal plate and dried and cured at 25°C for 6 h. The dry film thickness was 1000 μm, thereby obtaining an absorbing coating.

[0046] Example 2

[0047] This embodiment is a method for preparing an absorbing coating based on rGO aerogel loaded with transition metal carbides. The specific steps are as follows:

[0048] (1) Preparation of WC / rGOA composite absorber:

[0049] 24 mL of 12.8 mg / mL ascorbic acid solution was added to 12 mL of 10 mg / mL graphene oxide aqueous solution. After vibrating thoroughly for 5 min, 8 mL of ethanol was added and vibrated again for 3 min. The mixture was sealed in a glass container and placed in an 85°C oven for pre-reduction for 30 min. It was then transferred to a -40°C freeze dryer and frozen for 30 min. After being taken out, it was thawed at room temperature and then placed in a 95°C oven for further reduction for 5 h. Finally, rGOA was obtained after drying in a -60°C freeze dryer for 24 h. It was taken out for use. 50 mL of 0.1 mol / L Na2WO4·2H2O was weighed and dissolved in 50 mL of 0.1 mol / L dopamine hydrochloride aqueous solution, and the pH was adjusted to 2 with hydrochloric acid. Then, the prepared rGOA was completely immersed in the above solution. After soaking and reacting for 1 hour, it was washed three times with deionized water and ethanol alternately, and then dried in a 60℃ oven overnight. Finally, it was calcined in a tubular furnace with nitrogen at a heating rate of 5℃ / min and a temperature of 1000℃ for 3 hours to obtain a WC / rGOA composite absorber.

[0050] (2) Preparation of radar-absorbing coating:

[0051] 25 parts by mass of acrylic polyurethane resin, 3 parts by mass of xylene, and 0.7 parts by mass of BYK-163 dispersant were added to a paint mixing can and dispersed evenly. 0.1 parts by mass of bentonite was added and dispersed at a speed of 2000 r / min for 15 minutes. 70 parts by mass of a composite absorber was added and dispersed at a speed of 2000 r / min for 1 hour. 0.1 parts by mass of TEGO-300 leveling agent, 0.1 parts by mass of BYK-141 defoamer, and 1 part by mass of butyl acetate were added and dispersed at a speed of 1500 r / min for 15 minutes to obtain component A. Component A was then mixed evenly with component B (HT-100 curing agent) in a mass ratio of 3:1 to obtain an absorbing coating based on rGO aerogel-loaded WC.

[0052] (3) Preparation of microwave absorbing coating:

[0053] The absorbing coating based on rGO aerogel loaded with WC obtained in step (2) was sprayed on a metal plate and dried and cured at 25°C for 6 h. The dry film thickness was 1000 μm, thereby obtaining an absorbing coating.

[0054] Example 3

[0055] This embodiment is a method for preparing an absorbing coating based on rGO aerogel loaded with transition metal carbides. The specific steps are as follows:

[0056] (1) Preparation of WC / rGOA composite absorber:

[0057] 72 mL of 12.8 mg / mL ascorbic acid solution was added to 12 mL of 10 mg / mL graphene oxide aqueous solution. After vibrating thoroughly for 5 min, 9 mL of ethanol was added and vibrated again for 3 min. The mixture was sealed in a glass container and placed in a 95°C oven for pre-reduction for 40 min. It was then transferred to a -35°C freeze dryer and frozen for 40 min. After being taken out, it was thawed at room temperature and then placed in an 85°C oven for further reduction for 4 h. Finally, rGOA was obtained after drying in a -75°C freeze dryer for 18 h. It was taken out for use. 50 mL of 0.1 mol / L Na2WO4·2H2O was weighed and dissolved in 50 mL of 0.1 mol / L dopamine hydrochloride aqueous solution, and the pH was adjusted to 4 with hydrochloric acid. Then, the prepared rGOA was completely immersed in the above solution. After soaking and reacting for 3 h, it was washed alternately with deionized water and ethanol for 6 times, then dried in a 50℃ oven overnight, and finally calcined in a tubular furnace with nitrogen at a heating rate of 3℃ / min and a temperature of 1000℃ for 3 h to obtain a WC / rGOA composite absorber.

[0058] (2) Preparation of radar-absorbing coating:

[0059] 40 parts by mass of acrylic polyurethane resin, 5 parts by mass of xylene, and 0.8 parts by mass of BYK-163 dispersant were added to a paint mixing can and dispersed evenly. 0.2 parts by mass of bentonite was added and dispersed at 2000 r / min for 15 minutes. 45 parts by mass of a composite absorber was added and dispersed at 2000 r / min for 1 hour. Finally, 3 parts by mass of TEGO-300 leveling agent, 4 parts by mass of BYK-141 defoamer, and 2 parts by mass of butyl acetate were added and dispersed at 1500 r / min for 15 minutes to obtain component A. The resulting absorbing coating was then mixed evenly with HT-100 curing agent in a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel-loaded WC.

[0060] (3) Preparation of microwave absorbing coating:

[0061] The absorbing coating based on rGO aerogel loaded with WC obtained in step (2) was sprayed on a metal plate and dried and cured at 25°C for 6 h. The dry film thickness was 1000 μm, thereby obtaining an absorbing coating.

[0062] Example 4

[0063] This embodiment is a method for preparing an absorbing coating based on rGO aerogel loaded with transition metal carbides. The specific steps are as follows:

[0064] (1) Preparation of WC / rGOA composite absorber:

[0065] 28 mL of 12.8 mg / mL ascorbic acid solution was added to 12 mL of 10 mg / mL graphene oxide aqueous solution. After vibrating thoroughly for 5 min, 8 mL of ethanol was added and vibrated again for 3 min. The mixture was sealed in a glass container and placed in a 95°C oven for pre-reduction for 20 min. It was then transferred to a -45°C freeze dryer and frozen for 30 min. After being taken out, it was thawed at room temperature and then placed in a 95°C oven for another 6 h. Finally, rGOA was obtained after drying in a -60°C freeze dryer for 36 h. It was taken out for use. 50 mL of 0.1 mol / L Na2WO4·2H2O was weighed and dissolved in 50 mL of 0.1 mol / L dopamine hydrochloride aqueous solution, and the pH was adjusted to 2 with hydrochloric acid. Then, the prepared rGOA was completely immersed in the above solution. After soaking and reacting for 2 h, it was washed three times with deionized water and ethanol alternately, and then dried in a 70℃ oven overnight. Finally, it was calcined in a tubular furnace with nitrogen at a heating rate of 6℃ / min and a temperature of 1000℃ for 3 h to obtain a WC / rGOA composite absorber.

[0066] (2) Preparation of radar absorbing coating:

[0067] 30 parts by mass of acrylic polyurethane resin, 15 parts by mass of xylene, and 1.2 parts by mass of BYK-163 dispersant were added to a paint mixing can and dispersed evenly. 0.8 parts by mass of bentonite was added and dispersed at a speed of 2000 r / min for 15 minutes. 45 parts by mass of a composite absorber was added and dispersed at a speed of 2000 r / min for 1 hour. 2 parts by mass of TEGO-300 leveling agent, 3 parts by mass of BYK-141 defoamer, and 3 parts by mass of butyl acetate were added and dispersed at a speed of 1500 r / min for 15 minutes to obtain component A. Component A was then mixed evenly with component B (HT-100 curing agent) in a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel-loaded WC.

[0068] (3) Preparation of microwave absorbing coating:

[0069] The absorbing coating based on rGO aerogel loaded with WC obtained in step (2) was sprayed on a metal plate and dried and cured at 25°C for 4 h. The dry film thickness was 1000 μm, thereby obtaining an absorbing coating.

[0070] Example 5

[0071] This embodiment is a method for preparing an absorbing coating based on rGO aerogel loaded with transition metal carbides. The specific steps are as follows:

[0072] (1) Preparation of WC / rGOA composite absorber:

[0073] 28 mL of 12.8 mg / mL ascorbic acid solution was added to 12 mL of 10 mg / mL graphene oxide aqueous solution. After vibrating thoroughly for 5 min, 8 mL of ethanol was added and vibrated again for 3 min. The mixture was sealed in a glass container and placed in a 95°C oven for pre-reduction for 30 min. It was then transferred to a -40°C freeze dryer and frozen for 30 min. After being taken out, it was thawed at room temperature and then placed in a 95°C oven for further reduction for 5 h. Finally, rGOA was obtained after drying in a -60°C freeze dryer for 24 h. It was taken out for use. 50 mL of 0.1 mol / L Na2WO4·2H2O was weighed and dissolved in 50 mL of 0.1 mol / L dopamine hydrochloride aqueous solution, and the pH was adjusted to 2 with hydrochloric acid. Then, the prepared rGOA was completely immersed in the above solution. After soaking and reacting for 3 h, it was washed three times with deionized water and ethanol alternately, and then dried in a 60℃ oven overnight. Finally, it was calcined in a tubular furnace with nitrogen at a heating rate of 5℃ / min and a temperature of 800℃ for 5 h to obtain a WC / rGOA composite absorber.

[0074] (2) Preparation of radar absorbing coating:

[0075] 40 parts by mass of acrylic polyurethane resin, 10 parts by mass of xylene, and 0.1 parts by mass of BYK-163 dispersant were added to a paint mixing can and dispersed evenly. 0.8 parts by mass of bentonite was added and dispersed at a speed of 2000 r / min for 15 minutes. 45 parts by mass of a composite absorber was added and dispersed at a speed of 2000 r / min for 1 hour. 0.1 parts by mass of TEGO-300 leveling agent, 0.5 parts by mass of BYK-141 defoamer, and 3.5 parts by mass of butyl acetate were then added and dispersed at a speed of 1500 r / min for 15 minutes to obtain component A. Component A was then mixed evenly with component B (HT-100 curing agent) in a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel-loaded WC.

[0076] (3) Preparation of microwave absorbing coating:

[0077] The absorbing coating based on rGO aerogel loaded with WC obtained in step (2) was sprayed on a metal plate and dried and cured at 25°C for 8 h. The dry film thickness was 1000 μm, thereby obtaining an absorbing coating.

[0078] Example 6

[0079] This embodiment is a method for preparing an absorbing coating based on rGO aerogel loaded with transition metal carbides. The specific steps are as follows:

[0080] (1) Preparation of WC / rGOA composite absorber:

[0081] 28 mL of 12.8 mg / mL ascorbic acid solution was added to 12 mL of 10 mg / mL graphene oxide aqueous solution. After vibrating thoroughly for 5 min, 8 mL of ethanol was added and vibrated again for 3 min. The mixture was sealed in a glass container and placed in a 95°C oven for pre-reduction for 30 min. It was then transferred to a -40°C freeze dryer and frozen for 30 min. After being taken out, it was thawed at room temperature and then placed in a 95°C oven for further reduction for 5 h. Finally, rGOA was obtained after drying in a -60°C freeze dryer for 24 h. It was taken out for use. 50 mL of 0.1 mol / L Na2WO4·2H2O was weighed and dissolved in 50 mL of 0.1 mol / L dopamine hydrochloride aqueous solution, and the pH was adjusted to 2 with hydrochloric acid. Then, the prepared rGOA was completely immersed in the above solution. After soaking and reacting for 1 hour, it was washed three times with deionized water and ethanol alternately, and then dried in a 60℃ oven overnight. Finally, it was calcined in a tubular furnace with nitrogen at a heating rate of 5℃ / min and a temperature of 900℃ for 3 hours to obtain a WC / rGOA composite absorber.

[0082] (2) Preparation of radar absorbing coating:

[0083] 50 parts by mass of acrylic polyurethane resin, 5 parts by mass of xylene, and 2 parts by mass of BYK-163 dispersant were added to a paint mixing can and dispersed evenly. 10 parts by mass of bentonite was added and dispersed at a speed of 2000 r / min for 15 minutes. 30 parts by mass of a composite absorber was added and dispersed at a speed of 2000 r / min for 1 hour. 0.5 parts by mass of TEGO-300 leveling agent, 0.5 parts by mass of BYK-141 defoamer, and 2 parts by mass of butyl acetate were then added and dispersed at a speed of 1500 r / min for 15 minutes to obtain component A. Component A was then mixed evenly with component B (HT-100 curing agent) in a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel-loaded WC.

[0084] (3) Preparation of microwave absorbing coating:

[0085] The absorbing coating based on rGO aerogel loaded with WC obtained in step (2) was sprayed on a metal plate and dried and cured at 25°C for 6 h. The dry film thickness was 1000 μm, thereby obtaining an absorbing coating.

[0086] Example 7

[0087] This embodiment is a method for preparing an absorbing coating based on rGO aerogel loaded with transition metal carbides. The specific steps are as follows:

[0088] (1) Preparation of WC / rGOA composite absorber:

[0089] 28 mL of 12.8 mg / mL ascorbic acid solution was added to 12 mL of 10 mg / mL graphene oxide aqueous solution. After vibrating thoroughly for 5 min, 8 mL of ethanol was added and vibrated again for 3 min. The mixture was sealed in a glass container and placed in a 95°C oven for pre-reduction for 30 min. It was then transferred to a -40°C freeze dryer and frozen for 30 min. After being taken out, it was thawed at room temperature and then placed in a 95°C oven for further reduction for 5 h. Finally, rGOA was obtained after drying in a -60°C freeze dryer for 24 h. It was taken out for use. 50 mL of 0.1 mol / L Na2WO4·2H2O was weighed and dissolved in 50 mL of 0.1 mol / L dopamine hydrochloride aqueous solution, and the pH was adjusted to 2 with hydrochloric acid. Then, the prepared rGOA was completely immersed in the above solution. After soaking and reacting for 3 h, it was washed three times with deionized water and ethanol alternately, and then dried in a 60℃ oven overnight. Finally, it was calcined in a tubular furnace with nitrogen at a heating rate of 5℃ / min and a temperature of 1100℃ for 3 h to obtain a WC / rGOA composite absorber.

[0090] (2) Preparation of radar-absorbing coating:

[0091] 35 parts by mass of acrylic polyurethane resin, 10 parts by mass of xylene, and 0.1 parts by mass of BYK-163 dispersant were added to a paint mixing can and dispersed evenly. 0.8 parts by mass of bentonite was added and dispersed at a speed of 2000 r / min for 15 minutes. 50 parts by mass of a composite absorber was added and dispersed at a speed of 2000 r / min for 1 hour. 0.1 parts by mass of TEGO-300 leveling agent, 0.5 parts by mass of BYK-141 defoamer, and 3.5 parts by mass of butyl acetate were then added and dispersed at a speed of 1500 r / min for 15 minutes to obtain component A. Component A was then mixed evenly with component B (HT-100 curing agent) in a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel-loaded WC.

[0092] (3) Preparation of microwave absorbing coating:

[0093] The absorbing coating based on rGO aerogel loaded with WC obtained in step (2) was sprayed on a metal plate and dried and cured at 25°C for 6 h. The dry film thickness was 1000 μm, thereby obtaining an absorbing coating.

[0094] Comparative Example 1

[0095] The same as Example 1, except that no composite absorber was added in this comparative example. The specific steps are as follows:

[0096] 40 parts by mass of acrylic polyurethane resin, 10 parts by mass of xylene, and 0.1 parts by mass of BYK-163 dispersant were added to a paint mixing can and dispersed evenly. 0.8 parts by mass of bentonite was added and dispersed at a speed of 2000 r / min for 15 minutes. 0.1 parts by mass of TEGO-300 leveling agent, 0.5 parts by mass of BYK-141 defoamer, and 3.5 parts by mass of butyl acetate were then added and dispersed at a speed of 1500 r / min for 15 minutes to obtain component A. Component A was then mixed with component B (HT-100 curing agent) in a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel-loaded WC.

[0097] The absorbing coating based on rGO aerogel loaded with WC was sprayed on a metal plate and dried and cured at 25°C for 6 h. The dry film thickness was 1000 μm to obtain a coating.

[0098] Comparative Example 2

[0099] The difference is that the composite absorber is replaced with carbonyl iron powder in this comparative example. The specific steps are as follows:

[0100] 35 parts by mass of acrylic polyurethane resin, 10 parts by mass of xylene, and 0.1 parts by mass of BYK-163 dispersant were added to a paint mixing can and dispersed evenly. 0.8 parts by mass of bentonite was added and dispersed at a speed of 2000 r / min for 15 minutes. 45 parts by mass of carbonyl iron powder was added and dispersed at a speed of 2000 r / min for 1 hour. 0.1 parts by mass of TEGO-300 leveling agent, 0.5 parts by mass of BYK-141 defoamer, and 3.5 parts by mass of butyl acetate were added and dispersed at a speed of 1500 r / min for 15 minutes to obtain component A. Component A was then mixed with component B (HT-100 curing agent) in a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel-loaded WC.

[0101] The absorbing coating based on rGO aerogel loaded with WC was sprayed on a metal plate and dried and cured at 25°C for 6 hours. The dry film thickness was 1000 μm to obtain the absorbing coating.

[0102] Comparative Example 3

[0103] The difference is that the composite absorber is replaced with tungsten carbide nanopowder in this comparative example. The specific steps are as follows:

[0104] 35 parts by mass of acrylic polyurethane resin, 10 parts by mass of xylene, and 0.1 parts by mass of BYK-163 dispersant were added to a paint mixing tank and dispersed evenly. 0.8 parts by mass of bentonite was added and dispersed at a speed of 2000 r / min for 15 min. 45 parts by mass of tungsten carbide nanopowder was added and dispersed at a speed of 2000 r / min for 1 h. 0.1 parts by mass of TEGO-300 leveling agent, 0.5 parts by mass of BYK-141 defoamer, and 3.5 parts by mass of butyl acetate were added and dispersed at a speed of 1500 r / min for 15 min to obtain component A. Component A and component B (HT-100 curing agent) were evenly mixed in a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel-loaded WC.

[0105] The absorbing coating based on rGO aerogel loaded with WC was sprayed on a metal plate and dried and cured at 25°C for 6 hours. The dry film thickness was 1000 μm to obtain the absorbing coating.

[0106] Comparative Example 4

[0107] The difference is that this comparative example does not adopt the pre-reduction-freeze-thaw-re-reduction-freeze-drying strategy, but adopts a one-step reduction-freeze-drying method. The specific steps are as follows:

[0108] (1) Preparation of WC / rGOA composite absorber:

[0109] 28 mL of 12.8 mg / mL ascorbic acid solution was added to 12 mL of 10 mg / mL graphene oxide aqueous solution. The mixture was shaken thoroughly for 5 minutes, followed by the addition of 8 mL of ethanol and further shaken for 3 minutes. The mixture was sealed in a glass container and reduced in a 95°C oven for 5 hours. Finally, it was dried in a -60°C freeze dryer for 24 hours to obtain rGOA, which was then removed for later use. 50 mL of 0.1 mol / L Na₂WO₄·2H₂O was weighed and dissolved in 50 mL of 0.1 mol / L dopamine hydrochloride aqueous solution. The pH was adjusted to 2 with hydrochloric acid. The prepared rGOA was then completely immersed in the solution. After soaking for 1 hour, the mixture was washed three times with deionized water and ethanol alternately, then dried in a 60°C oven overnight. Finally, the mixture was calcined in a nitrogen-filled tube furnace at 1000°C for 3 hours at a heating rate of 5°C / min to obtain the WC / rGOA composite absorber.

[0110] (2) Preparation of radar-absorbing coating:

[0111] 40 parts by mass of acrylic polyurethane resin, 10 parts by mass of xylene, and 0.1 parts by mass of BYK-163 dispersant were added to a paint mixing can and dispersed evenly. 0.8 parts by mass of bentonite was added and dispersed at a speed of 2000 r / min for 15 minutes. 45 parts by mass of a composite absorber was added and dispersed at a speed of 2000 r / min for 1 hour. 0.1 parts by mass of TEGO-300 leveling agent, 0.5 parts by mass of BYK-141 defoamer, and 3.5 parts by mass of butyl acetate were added and dispersed at a speed of 1500 r / min for 15 minutes to obtain component A. Component A was then mixed evenly with component B (HT-100 curing agent) in a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel-loaded WC.

[0112] The absorbing coating based on rGO aerogel loaded with WC was sprayed on a metal plate and dried and cured at 25°C for 6 h. The dry film thickness was 1000 μm to obtain the absorbing coating.

[0113] Comparative Example 5

[0114] The difference is that this comparative example does not adopt the impregnation strategy, but instead adopts the method of directly mixing rGOA and tungsten carbide nanopowder to prepare the composite absorber. The specific steps are as follows:

[0115] (1) Preparation of WC / rGOA composite absorber:

[0116] 28 mL of 12.8 mg / mL ascorbic acid solution was added to 12 mL of 10 mg / mL graphene oxide aqueous solution. After vibrating thoroughly for 5 min, 8 mL of ethanol was added and vibrated again for 3 min. The mixture was sealed in a glass container and placed in a 95°C oven for pre-reduction for 30 min. It was then transferred to a -40°C freeze dryer and frozen for 30 min. After being taken out, it was thawed at room temperature and then placed in a 95°C oven for further reduction for 5 h. Finally, rGOA was obtained after drying in a -60°C freeze dryer for 24 h. It was taken out for use. 50 mL of 0.1 mol / L Na2WO4·2H2O was weighed and dissolved in 50 mL of 0.1 mol / L dopamine hydrochloride aqueous solution. The pH was adjusted to 2 with hydrochloric acid. After reacting for 1 h, the precipitate was separated by centrifugation and washed alternately with deionized water and ethanol three times. It was then dried in a 60°C oven overnight and finally calcined in a nitrogen-filled tubular furnace at a heating rate of 5°C / min and a temperature of 1000°C for 3 h. WC and rGOA were evenly mixed to obtain a composite absorber.

[0117] (2) Preparation of radar absorbing coating:

[0118] 40 parts by mass of acrylic polyurethane resin, 10 parts by mass of xylene, and 0.1 parts by mass of BYK-163 dispersant were added to a paint mixing can and dispersed evenly. 0.8 parts by mass of bentonite was added and dispersed at a speed of 2000 r / min for 15 minutes. 45 parts by mass of a composite absorber was added and dispersed at a speed of 2000 r / min for 1 hour. 0.1 parts by mass of TEGO-300 leveling agent, 0.5 parts by mass of BYK-141 defoamer, and 3.5 parts by mass of butyl acetate were added and dispersed at a speed of 1500 r / min for 15 minutes to obtain component A. Component A was then mixed evenly with component B (HT-100 curing agent) in a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel-loaded WC.

[0119] The absorbing coating based on rGO aerogel loaded with WC was sprayed on a metal plate and dried and cured at 25°C for 6 h. The dry film thickness was 1000 μm to obtain the absorbing coating.

[0120] Comparative Example 6

[0121] The difference is that the calcination temperature is adjusted to 700°C in this comparative example. The specific steps are as follows:

[0122] (1) Preparation of WC / rGOA composite absorber:

[0123] 28 mL of 12.8 mg / mL ascorbic acid solution was added to 12 mL of 10 mg / mL graphene oxide aqueous solution. After vibrating thoroughly for 5 min, 8 mL of ethanol was added and vibrated again for 3 min. The mixture was sealed in a glass container and placed in a 95°C oven for pre-reduction for 30 min. It was then transferred to a -40°C freeze dryer and frozen for 30 min. After being taken out, it was thawed at room temperature and then placed in a 95°C oven for further reduction for 5 h. Finally, rGOA was obtained after drying in a -60°C freeze dryer for 24 h. It was taken out for use. 50 mL of 0.1 mol / L Na2WO4·2H2O was weighed and dissolved in 50 mL of 0.1 mol / L dopamine hydrochloride aqueous solution, and the pH was adjusted to 2 with hydrochloric acid. Then, the prepared rGOA was completely immersed in the above solution. After soaking and reacting for 1 hour, it was washed three times with deionized water and ethanol alternately, and then dried in a 60℃ oven overnight. Finally, it was calcined in a tubular furnace with nitrogen at a heating rate of 5℃ / min and a temperature of 700℃ for 3 hours to obtain a WC / rGOA composite absorber.

[0124] (2) Preparation of radar-absorbing coating:

[0125] 40 parts by mass of acrylic polyurethane resin, 10 parts by mass of xylene, and 0.1 parts by mass of BYK-163 dispersant were added to a paint mixing can and dispersed evenly. 0.8 parts by mass of bentonite was added and dispersed at a speed of 2000 r / min for 15 minutes. 45 parts by mass of a composite absorber was added and dispersed at a speed of 2000 r / min for 1 hour. 0.1 parts by mass of TEGO-300 leveling agent, 0.5 parts by mass of BYK-141 defoamer, and 3.5 parts by mass of butyl acetate were then added and dispersed at a speed of 1500 r / min for 15 minutes to obtain component A. Component A was then mixed evenly with component B (HT-100 curing agent) in a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel-loaded WC.

[0126] The absorbing coating based on rGO aerogel loaded with WC was sprayed on a metal plate and dried and cured at 25°C for 6 h. The dry film thickness was 1000 μm to obtain the absorbing coating.

[0127] The electromagnetic wave absorption performance (reflection loss value and effective absorption bandwidth) of the samples in the embodiments and comparative examples of the present invention was measured by the arch method, and the neutral salt spray resistance was tested according to GB / T 1771-2007. The performance test results are as follows:

[0128]

[0129] The coatings prepared in Examples 1-4 showed good absorbing effects, among which Example 2 had better radar wave absorption capacity and salt spray resistance due to the large amount of absorber added. Examples 5-6 had poor absorbing performance and salt spray resistance due to the low calcination temperature, and tungsten carbide nanoparticles with complete crystal form were not formed. Example 7 used calcination at 1100°C and still formed a WC / rGOA composite absorber, so the absorbing performance and salt spray resistance were similar to those of Example 1. Comparative Example 1 did not add any absorber or anti-corrosion filler, so it did not show absorbing performance and salt spray resistance. Comparative Example 2 added carbonyl iron as an absorber, and although it showed certain absorbing performance, it also accelerated the corrosion of the coating. Comparative Example 3, in which single tungsten carbide nanoparticles were added as an absorber, exhibited poor absorption but good salt spray resistance. This was primarily due to the poor impedance matching of single tungsten carbide nanoparticles, making it difficult for radar waves to enter the absorber and be lost. However, when tungsten carbide was loaded onto the rich pore structure of reduced graphene oxide aerogel, the aerogel's porous structure allowed radar waves to enter, optimizing impedance matching and thus enhancing absorption and improving the coating's salt spray resistance. The absorption performance of Comparative Example 4 was significantly lower than that of Example 1. This was due to the direct reduction-freeze-drying method, which caused significant shrinkage of the rGOA and reduced porosity, thus reducing absorption. Comparative Example 5, in which WC and rGOA were directly mixed, exhibited poor absorption due to the poor impedance matching of the resulting composite material. The sample from Comparative Example 6 had no absorption and poor salt spray resistance, due to the lower calcination temperature, which prevented the formation of tungsten carbide.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A radar absorbing coating based on rGO aerogel loaded with transition metal carbides, characterized in that: The invention comprises component A and component B, wherein the component A is formulated as follows in parts by mass: 25-50 parts of a film-forming resin, 0.1-10 parts of a rheological additive, 30-70 parts of a composite absorber, 0.1-3.0 parts of a leveling agent, 0.1-2.0 parts of a dispersant, 0.1-4 parts of a defoamer, and 4-20 parts of a solvent; the film-forming resin is at least one of an acrylic polyurethane resin and a fluorocarbon resin; the component B is a curing agent; the mass ratio of component A to component B is (3-10):1; and the preparation method of the composite absorber in component A is as follows: Step 1, preparation of rGOA: add an ascorbic acid aqueous solution with a concentration of 6-20 mg / mL to an aqueous solution of graphene oxide with a concentration of 2-20 mg / mL, shake thoroughly for 5-10 minutes, then add ethanol, shake thoroughly again for 3-7 minutes, seal in a glass bottle, pre-reduce in an oven, then transfer to a freeze dryer for freezing, take out for thawing, then transfer to an oven for redistribution, and finally vacuum dry in a freeze dryer to obtain rGOA aerogel for standby use, wherein the volume ratio of the graphene oxide aqueous solution to the ascorbic acid aqueous solution is 1: (2-6), the volume ratio of ethanol to the ascorbic acid aqueous solution is 1: (3-8), the pre-reduction oven temperature is 85-95°C, the pre-reduction time is 20-40 minutes; the freezing temperature is -35~-45°C, the freezing time is 30-40 minutes; the re-reduction temperature is 85-95°C, the re-reduction time is 4-6 hours; the vacuum drying temperature in the freeze dryer is -60~-75°C, and the drying time is 18-36 hours; Step 2, preparation of TMCs / rGOA composite absorber: adding a transition metal salt solution with a concentration of 0.1 mol / L to a 0.1 mol / L dopamine hydrochloride aqueous solution in a volume ratio of 1: (1-3), and adjusting the pH to 2-4 with hydrochloric acid, then completely immersing the rGOA aerogel obtained in step 1 in the mixed solution, and after the reaction, washing the aerogel alternately with deionized water and ethanol, drying in a vacuum oven overnight, and finally calcining in an inert atmosphere to obtain an rGOA-loaded TMCs composite absorber, wherein the transition metal is tungsten, the immersion time is 1-3 h; the number of alternating washings is 3-6 times; the temperature for drying overnight in a vacuum oven is 50-70°C; the calcination in an inert atmosphere is specifically as follows: the inert atmosphere is nitrogen or argon, the heating rate is 3-6°C / min, the calcination temperature is 1000-1100°C, and the calcination time is 3-5 h.

2. The radar absorbing coating based on rGO aerogel loaded with transition metal carbides according to claim 1, characterized in that: The curing agent is an isocyanate curing agent.

3. The radar absorbing coating based on rGO aerogel loaded with transition metal carbides according to claim 1, characterized in that: The rheological additive is at least one of bentonite, fumed silica, polyamide wax and polyethylene wax.

4. The radar absorbing coating based on rGO aerogel loaded with transition metal carbides according to claim 1, characterized in that: The solvent is at least one of butanol, toluene, butyl acetate, xylene, cyclohexane, ethyl acetate and solvent oil.

5. The method for preparing a radar absorbing coating based on rGO aerogel loaded with transition metal carbides according to any one of claims 1 to 4, characterized in that: The steps are as follows: add the film-forming resin, the first solvent, and the dispersant into the paint mixing tank and disperse them evenly; add the rheological additive and disperse at a speed of 2000 r / min for 15 minutes; add the composite absorber and continue to disperse at a speed of 2000 r / min for 1 hour; then add the leveling agent, defoaming agent and the second solvent; the mass ratio of the first solvent to the second solvent is (2.5-5):1; disperse at a speed of 1500 r / min for 15 minutes to obtain component A; mix component A and component B evenly before use.

6. Use of a radar absorbing coating based on rGO aerogel loaded with transition metal carbides according to any one of claims 1 to 4 in the preparation of a radar wave absorbing coating, characterized in that: The specific application process is as follows: the radar wave absorbing coating based on rGO aerogel loaded with transition metal carbide is sprayed on the metal plate and dried and cured at 25°C for 4-8 hours. The dry film thickness is 1000 μm to obtain a radar wave absorbing coating.

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