Wave-absorbing coating based on rGO aerogel loaded transition metal carbide as well as preparation method and application of wave-absorbing coating

Abstract

The invention discloses a wave-absorbing coating based on rGO aerogel loaded transition metal carbide as well as a preparation method and application thereof. The wave-absorbing coating comprises a component A and a component B, wherein the component A comprises film-forming resin, a rheological additive, a composite wave-absorbing agent, a flatting agent, a dispersing agent, a defoaming agent and a solvent; a preparation method of the composite wave absorbing agent comprises the following steps: adding a mixed solution of ascorbic acid, deionized water and ethanol into an aqueous solution of graphene oxide, carrying out pre-reduction, freeze thawing, re-reduction and freeze drying to obtain rGOA, and taking out the rGOA for later use; a transition metal salt solution is added into an acidic dopamine hydrochloride aqueous solution to obtain a mixed solution, then the obtained rGOA is completely immersed in the mixed solution, washing and vacuum drying are performed overnight after a reaction, and finally calcination is performed in an inert atmosphere. According to the invention, the abundant three-dimensional pore structure of the rGOA is filled with the TMCs nanoparticles, so that the prepared coating has the advantages of light weight, corrosion resistance, wide absorption band, strong absorption capability and the like.

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 transition metal carbide and a preparation method and application thereof. Background Art

[0002] The current radar wave absorbing coatings have the problems of heavy weight, narrow effective absorption band, large coating thickness and weak absorption capacity. In addition, the traditional absorbing coatings have poor anti-corrosion performance and are not resistant to high temperatures, which greatly limits the wide application of absorbing coatings. Therefore, it is particularly important to prepare a radar wave absorbing coating with both excellent anti-corrosion and absorbing properties.

[0003] At present, the radar wave absorbing coating reported in related reports mainly consists of four parts: binder, absorbent, additive and diluent, among which the absorbent is crucial as an absorbing filler, and the absorbing fillers currently used mainly include ferrite, carbonyl iron powder, carbon material, magnetic metal and magnetic metal oxide powder, etc. A Chinese patent with announcement number CN 103725073 B discloses a stealth coating, specifically a preparation method of a nano-level radar stealth coating, which disperses and mixes film-forming resin, solvent, additive and nano-level aluminum oxide, ferroferric oxide, carbonyl iron powder, cobalt oxide and graphite in a certain proportion to obtain a wide-band, compatible and thin absorbing coating, but the density of such absorbing fillers is relatively large, which greatly increases the load, thus greatly limiting its application. A Chinese patent application with publication number CN 117720835 A discloses a lightweight radar absorbing material and an application coating. The modified absorber is prepared by blending a core-shell magnet in which deposited strontium oxide is directionally adsorbed on the surface of ferroferric oxide with a coating emulsion consisting of polycarbonate polyol, diisocyanate and a catalyst, and then mixed with 25-30% film-forming resin and 0-15% additive to form a radar absorbing coating, which takes into account both lightweight and radar protection effects. However, the preparation method of the modified absorber is extremely complicated and difficult to produce and apply on a large scale.

[0004] In recent years, composite absorbing materials have developed rapidly, mainly because of their special magneto-electric synergy, which can achieve excellent impedance matching characteristics, making them have strong absorption and wide bandwidth absorbing effects, while also having properties such as light weight, corrosion resistance and high temperature resistance. Traditional composite absorbing materials are generally made by modifying highly conductive substrate materials with low dielectric materials such as ceramic materials, magnetic materials, and semiconductor materials. With the continuous advancement of materials science, transition metal carbides (TMCs) have attracted attention in the field of absorbing coatings due to their high hardness, mechanical stability, excellent thermal stability and corrosion resistance, especially their excellent metal-like conductivity. In addition, reduced graphene oxide aerogel (rGOA) is an excellent lightweight dielectric matrix material due to its high porosity, low density, and suitable conductivity. Its developed pore structure not only facilitates the entry of electromagnetic waves into the aerogel, optimizes impedance matching, but also increases the multiple reflections and scattering of electromagnetic waves inside the aerogel, which is beneficial to the attenuation of electromagnetic waves.

[0005] In view of this, the present invention cleverly fills TMCs nanoparticles into the three-dimensional pore structure rich in rGOA (TMCs / rGOA), realizing the ingenious compound of transition metal carbides and carbon materials, and 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 view of the problems of existing radar wave absorbing coatings, such as high density of absorbing fillers, weak absorption capacity and poor corrosion resistance of absorbing coatings, the present invention proposes an absorbing coating based on rGO aerogel loaded with transition metal carbides and a preparation method and application thereof. 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, wherein the component A is proportioned as follows by mass: 25-50 parts of film-forming resin, 0.1-10 parts of rheological additive, 30-70 parts of composite absorber, 0.1-3.0 parts of leveling agent, 0.1-2.0 parts of dispersant, 0.1-4 parts of defoamer and 4-20 parts of solvent; the component B is a curing agent, and the mass ratio of component A to component B is (3-10):1, wherein the preparation method of the composite absorber in component A is 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 min, then add ethanol, shake again for 3-7 min, 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, 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 transition metal salt solution with a concentration of 0.1 mol / L into 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, and after the reaction, wash the aerogel with deionized water and ethanol alternately for several times, dry it in a vacuum oven overnight, and finally calcine it in an inert atmosphere to obtain a composite absorber of rGOA loaded with TMCs.

[0010] Preferably, in the step 1, the pre-reduction oven temperature is 85-95°C, and the pre-reduction time is 20-40 min; the freezing temperature is -35~-45°C, and the freezing time is 30-40 min; the re-reduction temperature is 85-95°C, and 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 acrylic polyurethane resin and 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 BYK-118, BYK-130, BYK-110, BYK-111, BYK-161, BYK-306 from BYK The defoaming agent is at least one of BYK-066N, BYK-088, BYK-067A, BYK-085, BYK-141, BYK-070 from BYK Chemical, 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] The second object of the present invention is to provide a method for preparing the above-mentioned radar-absorbing coating based on rGO aerogel loaded transition metal carbide, the steps are as follows: adding a film-forming resin, a first solvent, and a dispersant into a paint mixing tank and dispersing them evenly, adding a rheological additive and dispersing them at a speed of 2000 r / min for 15 min, 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, 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 min to obtain component A, and mixing component A and component B evenly before use.

[0020] The third object of the present invention is to provide an application of the above-mentioned radar wave absorbing coating based on rGO aerogel loaded with transition metal carbides in the preparation of radar wave absorbing coatings. The specific application process is as follows: the radar wave absorbing coating based on rGO aerogel loaded with transition metal carbides is sprayed on a metal plate and dried and cured at 25°C for 4-8 h. The dry film thickness is 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. In the preparation process of rGOA, the 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, so that the aerogel obtains 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, so that the graphene surface retains 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 evenly 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 controls the components by controlling the calcination temperature, introduces a multi-heterogeneous structure to enhance the heterogeneous interface polarization and defect polarization, and enhances the radar wave absorption capacity of the coating. In addition, the TMCs / rGOA composite absorber has good dispersibility in the resin, the rGO nanosheets greatly hinder the entry of the electrolyte, and the excellent anti-chloride ion pitting effect of TMCs themselves and the synergistic effect of multiple interfaces also slow down the entry speed of the electrolyte, providing excellent corrosion resistance for the absorbing coating. DETAILED DESCRIPTION

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

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

[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] Transition metal salt is Na 2 WO 4 ·2H 2 O, purchased from Shanghai Aladdin Company, purity ≥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 Chemical Co., Ltd., Germany;

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

[0036] The 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, and the specific steps are as follows:

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

[0041] Measure 24 mL of 12.8 mg / mL ascorbic acid solution and add it to 12 mL of 10 mg / mL graphene oxide aqueous solution. After fully shaking for 5 min, add 8 mL of ethanol and shake again for 3 min. Seal the mixture in a glass container and place it in a 95°C oven for pre-reduction for 30 min. Transfer it to a -40°C freeze dryer and freeze it for 30 min. Take it out and thaw it at room temperature. Then place it in a 95°C oven for further reduction for 5 h. Finally, dry it in a -60°C freeze dryer for 24 h to obtain rGOA, which is then taken out for use. Weigh 50 mL of 0.1 mol / L Na 2 WO 4 ·2H 2 The WC / rGOA composite absorber was prepared by dissolving the WC / rGOA solution in 50 mL of 0.1 mol / L dopamine hydrochloride aqueous solution and adjusting the pH to 2 with hydrochloric acid. Then, the prepared rGOA was completely immersed in the above solution. After immersion reaction for 1 h, it was washed alternately with deionized water and ethanol for 3 times, and then dried in an oven at 60 °C overnight. Finally, it was calcined in a tubular furnace with nitrogen at a heating rate of 5 °C / min and a temperature of 1000 °C for 3 h to obtain the 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 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 composite absorber was added and dispersed at a speed of 2000 r / min for 1 h, and then 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 mixed evenly at a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel loaded with WC.

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

[0045] The radar 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 a radar 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, and the specific steps are as follows:

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

[0049] Measure 24 mL of 12.8 mg / mL ascorbic acid solution and add it to 12 mL of 10 mg / mL graphene oxide aqueous solution. After fully shaking for 5 min, add 8 mL of ethanol and shake again for 3 min. Seal the mixture in a glass container and place it in an oven at 85°C for pre-reduction for 30 min. Transfer it to a -40°C freeze dryer and freeze it for 30 min. Take it out and thaw it at room temperature. Then place it in a 95°C oven and reduce it for 5 h. Finally, dry it in a -60°C freeze dryer for 24 h to obtain rGOA, which is then taken out for use. Weigh 50 mL of 0.1 mol / L Na 2 WO 4 ·2H 2 WC / rGOA composite absorber was obtained by immersing the prepared rGOA in the above solution for 1 h, washing it with deionized water and ethanol for 3 times, and then drying it in an oven at 60 °C overnight. Finally, the rGOA was calcined in a nitrogen-filled tubular furnace at a heating rate of 5 °C / min and a temperature of 1000 °C for 3 h to obtain the 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 tank and dispersed evenly, 0.1 parts by mass of bentonite was added and dispersed at a speed of 2000 r / min for 15 min, 70 parts by mass of composite absorber was added and dispersed at a speed of 2000 r / min for 1 h, and then 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 min to obtain component A. Component A and component B (HT-100 curing agent) were mixed evenly at a mass ratio of 3:1 to obtain an absorbing coating based on rGO aerogel loaded with WC.

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

[0053] The radar 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 a radar 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, and 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, and 9 mL of ethanol was added after vibrating for 5 min. The mixture was sealed in a glass container and placed in a 95°C oven for pre-reduction for 40 min. It was 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, it was dried in a -75°C freeze dryer for 18 h to obtain rGOA, which was taken out for use. 50 mL of 0.1 mol / L Na 2 WO 4 ·2H 2 WC / rGOA composite absorber was obtained by immersing the prepared rGOA in the above solution for 3 h, washing it with deionized water and ethanol for 6 times, and then drying it in an oven at 50 °C overnight. Finally, the rGOA was calcined in a tubular furnace with nitrogen at a heating rate of 3 °C / min and a temperature of 1000 °C for 3 h to obtain the 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 tank and dispersed evenly, 0.2 parts by mass of bentonite was added and dispersed at a speed of 2000 r / min for 15 min, 45 parts by mass of composite absorber was added and dispersed at a speed of 2000 r / min for 1 h, and then 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 a speed of 1500 r / min for 15 min to obtain component A. The obtained absorbing coating was evenly mixed with HT-100 curing agent at a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel loaded WC.

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

[0061] The radar 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 a radar 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, and the specific steps are as follows:

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

[0065] Measure 28 mL of 12.8 mg / mL ascorbic acid solution and add it to 12 mL of 10 mg / mL graphene oxide aqueous solution. After fully shaking for 5 min, add 8 mL of ethanol and shake again for 3 min. Seal the mixture in a glass container and place it in a 95°C oven for pre-reduction for 20 min. Transfer it to a -45°C freeze dryer and freeze it for 30 min. Take it out and thaw it at room temperature. Then place it in a 95°C oven for another 6 h. Finally, dry it in a -60°C freeze dryer for 36 h to obtain rGOA, which is then taken out for use. Weigh 50 mL of 0.1 mol / L Na 2 WO 4 ·2H 2WC / rGOA composite absorber was obtained by immersing the prepared rGOA in the above solution for 2 h, washing it with deionized water and ethanol for 3 times, and then drying it in an oven at 70 °C overnight. Finally, the rGOA was calcined in a tubular furnace with nitrogen at a heating rate of 6 °C / min and a temperature of 1000 °C for 3 h to obtain the 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 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 composite absorber was added and dispersed at a speed of 2000 r / min for 1 h, and then 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 min to obtain component A. Component A and component B (HT-100 curing agent) were mixed evenly at a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel loaded with WC.

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

[0069] The radar 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 a radar 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, and the specific steps are as follows:

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

[0073] Measure 28 mL of 12.8 mg / mL ascorbic acid solution and add it to 12 mL of 10 mg / mL graphene oxide aqueous solution. After fully shaking for 5 min, add 8 mL of ethanol and shake again for 3 min. Seal the mixture in a glass container and place it in a 95°C oven for pre-reduction for 30 min. Transfer it to a -40°C freeze dryer and freeze it for 30 min. Take it out and thaw it at room temperature. Then place it in a 95°C oven for further reduction for 5 h. Finally, dry it in a -60°C freeze dryer for 24 h to obtain rGOA, which is then taken out for use. Weigh 50 mL of 0.1 mol / L Na 2 WO 4·2H 2 WC / rGOA composite absorber was obtained by immersing the prepared rGOA in the above solution for 3 h, washing it with deionized water and ethanol for 3 times, and then drying it in an oven at 60 °C overnight. Finally, the rGOA was calcined in a tubular furnace with nitrogen at a heating rate of 5 °C / min and a temperature of 800 °C for 5 h to obtain the 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 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 composite absorber was added and dispersed at a speed of 2000 r / min for 1 h, and then 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 mixed evenly at a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel loaded with WC.

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

[0077] The radar 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 a radar 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, and the specific steps are as follows:

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

[0081] Measure 28 mL of 12.8 mg / mL ascorbic acid solution and add it to 12 mL of 10 mg / mL graphene oxide aqueous solution. After fully shaking for 5 min, add 8 mL of ethanol and shake again for 3 min. Seal the mixture in a glass container and place it in a 95°C oven for pre-reduction for 30 min. Transfer it to a -40°C freeze dryer and freeze it for 30 min. Take it out and thaw it at room temperature. Then place it in a 95°C oven for further reduction for 5 h. Finally, dry it in a -60°C freeze dryer for 24 h to obtain rGOA, which is then taken out for use. Weigh 50 mL of 0.1 mol / L Na2 WO 4 ·2H 2 WC / rGOA composite absorber was obtained by immersing the prepared rGOA in the above solution for 1 h, washing it with deionized water and ethanol for 3 times, and then drying it in an oven at 60 °C overnight. Finally, the rGOA was calcined in a tubular furnace with nitrogen at a heating rate of 5 °C / min and a temperature of 900 °C for 3 h.

[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 tank and dispersed evenly, 10 parts by mass of bentonite were added and dispersed at a speed of 2000 r / min for 15 min, 30 parts by mass of composite absorber were added and dispersed at a speed of 2000 r / min for 1 h, and then 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 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 mixed evenly at a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel loaded with WC.

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

[0085] The radar 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 a radar 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, and the specific steps are as follows:

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

[0089] Measure 28 mL of 12.8 mg / mL ascorbic acid solution and add it to 12 mL of 10 mg / mL graphene oxide aqueous solution. After fully shaking for 5 min, add 8 mL of ethanol and shake again for 3 min. Seal the mixture in a glass container and place it in a 95°C oven for pre-reduction for 30 min. Transfer it to a -40°C freeze dryer and freeze it for 30 min. Take it out and thaw it at room temperature. Then place it in a 95°C oven for further reduction for 5 h. Finally, dry it in a -60°C freeze dryer for 24 h to obtain rGOA, which is then taken out for use. Weigh 50 mL of 0.1 mol / L Na 2 WO 4 ·2H 2 WC / rGOA composite absorber was obtained by immersing the prepared rGOA in the above solution for 3 h, washing it with deionized water and ethanol for 3 times, and then drying it in an oven at 60 °C overnight. Finally, the rGOA was calcined in a tubular furnace with nitrogen at a heating rate of 5 °C / min and a temperature of 1100 °C for 3 h to obtain the 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 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, 50 parts by mass of composite absorber was added and dispersed at a speed of 2000 r / min for 1 h, and then 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 mixed evenly at a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel loaded with WC.

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

[0093] The radar 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 a radar absorbing coating.

[0094] Comparative Example 1

[0095] The same as Example 1, except that no composite absorber is 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 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, and then 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 mixed evenly at a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel-loaded WC.

[0097] The microwave-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 by 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 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 carbonyl iron powder was added and dispersed at a speed of 2000 r / min for 1 h, and then 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 mixed evenly at a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel loaded with WC.

[0101] The radar 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, and the radar absorbing coating was obtained.

[0102] Comparative Example 3

[0103] The difference is that the composite absorber is replaced by 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. Then 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 with WC.

[0105] The radar 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, and the radar absorbing coating was obtained.

[0106] Comparative Example 4

[0107] The difference is the same as Example 1, in which the 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] Measure 28 mL of 12.8 mg / mL ascorbic acid solution and add it to 12 mL of 10 mg / mL graphene oxide aqueous solution. After vibrating for 5 min, add 8 mL of ethanol and vibrate again for 3 min. Seal the mixture in a glass container and place it in a 95°C oven for 5 h. Finally, dry it in a -60°C freeze dryer for 24 h to obtain rGOA, which is then taken out for use. Weigh 50 mL of 0.1 mol / L Na 2 WO 4 ·2H 2 WC / rGOA composite absorber was obtained by immersing the prepared rGOA in the above solution for 1 h, washing it with deionized water and ethanol for 3 times, and then drying it in an oven at 60 °C overnight. Finally, the rGOA was calcined in a tubular furnace with nitrogen at a heating rate of 5 °C / min and a temperature of 1000 °C for 3 h 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 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 composite absorber was added and dispersed at a speed of 2000 r / min for 1 h, and then 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 mixed evenly at a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel loaded with WC.

[0112] The radar-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 radar-absorbing coating.

[0113] Comparative Example 5

[0114] The difference is the same as Example 1, in which the present comparative example does not adopt the impregnation strategy, but 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] Measure 28 mL of 12.8 mg / mL ascorbic acid solution and add it to 12 mL of 10 mg / mL graphene oxide aqueous solution. After fully shaking for 5 min, add 8 mL of ethanol and shake again for 3 min. Seal the mixture in a glass container and place it in a 95°C oven for pre-reduction for 30 min. Transfer it to a -40°C freeze dryer and freeze it for 30 min. Take it out and thaw it at room temperature. Then place it in a 95°C oven for further reduction for 5 h. Finally, dry it in a -60°C freeze dryer for 24 h to obtain rGOA, which is then taken out for use. Weigh 50 mL of 0.1 mol / L Na 2 WO 4 ·2H 2 WC was dissolved in 50 mL of 0.1 mol / L dopamine hydrochloride aqueous solution, and the pH was adjusted to 2 with hydrochloric acid. After reacting for 1 h, the precipitate was separated by centrifugation, and then washed alternately with deionized water and ethanol for 3 times, and then dried in an oven at 60 °C overnight, and finally calcined in a tubular furnace with nitrogen at a heating rate of 5 °C / min and a temperature of 1000 °C for 3 h. After WC and rGOA were evenly mixed, a composite absorber was obtained.

[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 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 composite absorber was added and dispersed at a speed of 2000 r / min for 1 h, and then 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 mixed evenly at a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel loaded with WC.

[0119] The radar-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 radar-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] Measure 28 mL of 12.8 mg / mL ascorbic acid solution and add it to 12 mL of 10 mg / mL graphene oxide aqueous solution. After fully shaking for 5 min, add 8 mL of ethanol and shake again for 3 min. Seal the mixture in a glass container and place it in a 95°C oven for pre-reduction for 30 min. Transfer it to a -40°C freeze dryer and freeze it for 30 min. Take it out and thaw it at room temperature. Then place it in a 95°C oven for further reduction for 5 h. Finally, dry it in a -60°C freeze dryer for 24 h to obtain rGOA, which is then taken out for use. Weigh 50 mL of 0.1 mol / L Na 2 WO 4 ·2H 2 WC / rGOA composite absorber was obtained by immersing the prepared rGOA in the above solution for 1 h, washing it with deionized water and ethanol for 3 times, and then drying it in an oven at 60 °C overnight. Finally, the rGOA was calcined in a tubular furnace with nitrogen at a heating rate of 5 °C / min and a temperature of 700 °C for 3 h.

[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 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 composite absorber was added and dispersed at a speed of 2000 r / min for 1 h, and then 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 mixed evenly at a mass ratio of 10:1 to obtain an absorbing coating based on rGO aerogel loaded with WC.

[0126] The radar-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 radar-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 is measured by the arch method, and the neutral salt spray resistance is tested according to GB / T 1771-2007. The performance test results are as follows:

[0128]

[0129] The coatings prepared in Examples 1-4 exhibited 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 the failure to form tungsten carbide nanoparticles with complete crystal form. 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 absorbers and anti-corrosion fillers, 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. In Comparative Example 3, a single tungsten carbide nanoparticle is added as an absorber, and its wave absorption capacity is poor, but the salt spray resistance is good. This is mainly because the impedance matching ability of the single tungsten carbide nanoparticle is poor, and it is difficult for radar waves to enter the absorber for loss. After tungsten carbide is loaded on the rich pore structure of reduced graphene oxide aerogel, the porous structure of the aerogel easily allows radar waves to enter, optimizes the impedance matching, and thus enhances the wave absorption capacity and improves the salt spray resistance of the coating. The wave absorption performance of Comparative Example 4 is much lower than that of Example 1. This is because the direct reduction-freeze drying method is used, which causes rGOA to shrink significantly and the porosity is reduced, so the wave absorption performance is reduced. Comparative Example 5 directly mixes WC and rGOA, and the wave absorption performance is poor. This is because the impedance matching of the composite material obtained by direct mixing is poor. The sample of Comparative Example 6 has no wave absorption performance and poor salt spray resistance. This is because the lower calcination temperature fails to form tungsten carbide.

[0130] Finally, it should be noted that the above implementation modes are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned implementation modes, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned implementation modes can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the implementation modes 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 prepared in the following proportions by mass: 25-50 parts of film-forming resin, 0.1-10 parts of rheological additive, 30-70 parts of composite absorber, 0.1-3.0 parts of leveling agent, 0.1-2.0 parts of dispersant, 0.1-4 parts of defoamer and 4-20 parts of solvent, the component B is a curing agent, and the mass ratio of component A to component B is (3-10):1, wherein 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 min, then add ethanol, shake thoroughly for 3-7 min again, 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, finally vacuum dry in a freeze dryer to obtain rGOA aerogel 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); Step 2, preparation of TMCs / rGOA composite absorber: add a transition metal salt solution with a concentration of 0.1 mol / L into 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, and after the reaction, wash the aerogel alternately with deionized water and ethanol, dry it in a vacuum oven overnight, and finally calcine it in an inert atmosphere to obtain a composite absorber of rGOA loaded with TMCs.

2. The radar absorbing coating based on rGO aerogel loaded with transition metal carbides according to claim 1, characterized in that: In the step 1, the pre-reduction oven temperature is 85-95°C, and the pre-reduction time is 20-40 min; the freezing temperature is -35~-45°C, and the freezing time is 30-40 min; the re-reduction temperature is 85-95°C, and 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.

3. The radar absorbing coating based on rGO aerogel loaded with transition metal carbides according to claim 1, characterized in that: In the step 2, the transition metal is iron, cobalt, nickel, tungsten, molybdenum, zirconium, niobium or vanadium.

4. The radar absorbing coating based on rGO aerogel loaded with transition metal carbides according to claim 1, characterized in that: 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; 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.

5. The radar absorbing coating based on rGO aerogel loaded with transition metal carbides according to claim 1, characterized in that: The film-forming resin is at least one of an acrylic polyurethane resin and a fluorocarbon resin.

6. 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.

7. 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.

8. 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.

9. A method for preparing an absorbing coating based on rGO aerogel loaded with transition metal carbides according to any one of claims 1 to 8, 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 them 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.

10. Use of an absorbing coating based on rGO aerogel loaded with transition metal carbides according to any one of claims 1 to 8 in the preparation of a radar wave absorbing coating, characterized in that: The specific application process is as follows: spray the radar wave absorbing coating based on rGO aerogel loaded transition metal carbide on the metal plate and dry and cure it 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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