Preparation method of anti-corrosion nano wave absorber, coating and application

Abstract

The application provides a preparation method of a corrosion-resistant nanometer wave-absorbing agent, paint and application, and the preparation method comprises the following steps: S1, mixing polyunsaturated fatty acid, polyunsaturated fatty amine and trivalent iron raw materials in a stirrer until the mixture is uniform, heating at 100-150 DEG C for 20-60 min to remove moisture; S2, preheating the reaction system at 200-250 DEG C for 20-60 min, heating to 270-300 DEG C for 20-60 min, and naturally cooling to room temperature; S3, discarding the solution after heating reaction, then adding an organic solvent, mechanically stirring for 20-50 min, and then performing solid-liquid separation, and drying to obtain the product. According to the control of the addition proportion of the reaction raw materials, the particle size, micro-morphology and electromagnetic absorption performance of the final wave-absorbing agent can be changed, and the optimization and improvement of the electromagnetic wave absorption capacity can be realized; the ester organic matter wrapped outside in the reaction process can form a capsule protection layer outside the nanoparticles, isolate external corrosion elements, and itself does not have dielectric characteristics, and has good hydrophobicity, so that the corrosion resistance of the magnetic electromagnetic absorbing agent can be effectively improved.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic wave absorbing materials, and more specifically, to a method for preparing an anti-corrosion nano-absorbing agent, a coating, and its application. Background Technology

[0002] Electromagnetic wave absorbers, also known as microwave absorbers, are functional materials that can absorb incident electromagnetic waves and convert them into heat energy for dissipation. When used as a main filler and mixed with resin, they can be used to create functional microwave absorbing coatings. Currently, the main application of microwave absorbers is soft magnetic metal micropowders. During domain rotation, these powders overcome the resistance caused by magnetocrystalline anisotropy and magnetic stress anisotropy, achieving more efficient dissipation of incident electromagnetic waves and exhibiting excellent electromagnetic absorption performance.

[0003] For example, Chinese patent CN115101946A discloses a rare-earth magnetic microwave absorbing material and its preparation method. The atomic ratio of the rare-earth magnetic microwave absorbing material is: La 0.1-0.7, Ce 0.1-0.5, Sm 0.1-0.6, Fe 1.72-3.17, Sr 0.13-0.72, Mg 0.24-0.82, Mn 0.12-0.74, B 1.8-3.4, Se 0.6-2.2. It is prepared through steps such as batching, casting, ball milling, sintering, and secondary ball milling. The above method involves some unstable metallic configurations, which are easily corroded by harsh environments such as seawater, oxygen-rich rainwater, and salt spray during application, causing them to gradually oxidize and lose their electromagnetic wave absorption performance.

[0004] Chinese patent CN115763052A discloses a carbon-coated magnetic absorber, its preparation method, and its application. The absorber is obtained by ultrasonically dispersing magnetic particles into an organic carbon source solution, followed by drying and calcination. This method can significantly improve the corrosion resistance of the absorber; however, because carbon-based materials themselves possess certain dielectric properties, they can easily interfere with the overall dielectric characteristics of the magnetic absorber.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The problem solved by this invention is that existing microwave absorbing agents are difficult to balance corrosion resistance and electromagnetic wave absorption performance.

[0007] To address the above problems, this invention provides a method for preparing an anti-corrosion nano-absorbing agent, comprising:

[0008] Step S1: Mix polyunsaturated fatty acids, polyunsaturated fatty amines and ferric iron raw materials and stir until uniform. The ratio of the amount of polyunsaturated fatty acids, polyunsaturated fatty amines and ferric iron raw materials is v1:v2:m=(80-120):(80-120):(10-18). Then heat at 100-150℃ for 20-60 minutes to remove moisture.

[0009] Step S2: Preheat the reaction system at 200-250℃ for 20-60 min, then raise the temperature to 270-300℃ and hold for 20-60 min, then allow it to cool naturally to room temperature;

[0010] Step S3: Discard the solution after heating and reaction, then add organic solvent at a mass-to-volume ratio of 1:(1.5-3), stir mechanically for 20-50 minutes, and then perform solid-liquid separation. Dry the solid to obtain the final product.

[0011] The preparation method of this invention includes reaction pretreatment, hydrothermal process, separation and other steps. The reaction pretreatment process preheats the entire reaction system and removes water from the reaction system to form the microemulsion system required for the synthesis process. The hydrothermal process initiates the reduction of iron salts and the growth of nanoparticles. The separation process separates the synthesized products and retains an appropriate amount of amide polymer components, which can isolate external corrosive elements and has no dielectric characteristics and good hydrophobicity. Finally, an anti-corrosion nanomagnetic electromagnetic absorber coated with amide polymer is obtained. By controlling the proportion of organic matter in the reaction raw materials, the volume of the microemulsion coating the magnetic particles can be changed, thereby limiting the formation process of the magnetic absorber, changing the size and surface state of the magnetic absorber, and taking into account both anti-corrosion and electromagnetic absorption performance. The microwave absorber is formed in the form of nanoparticles with a particle size of 50-200 nm.

[0012] Preferably, the ferric raw material is one of ferric acetylacetone, ferric chloride, ferric nitrate, and ferric sulfate. Its specific dosage needs to be controlled so that it can be uniformly dispersed after stirring, although a small amount of precipitation may occur. Preferably, the entire reaction system is placed in a polytetrafluoroethylene liner, and the volume V of the reaction system is... 反 Volume V of the polytetrafluoroethylene liner 衬 Basically the same, for example, V 反 = (0.95-0.99)*V 衬 Only a small gap is allowed. The PTFE high-temperature resistant reaction liner is only to prevent the container from reacting at high temperatures during heating and affecting the formation of the target product. Preferably, in step S2, the PTFE liner is installed into the stainless steel hydrothermal reactor shell, tightened, and placed in a muffle furnace for heating. The entire reaction system is in an oxygen-free state.

[0013] Preferably, the polyunsaturated fatty acid and the polyunsaturated fatty amine correspond, that is, they have the same number of carbon atoms, such as 12-18 carbon compounds. This setting ensures that the reaction system is liquid, and the reaction effect is better when mixed. Preferably, the polyunsaturated fatty acid is (Z)-9-octadecenoic acid, and the polyunsaturated fatty amine is (Z)-9-octadecenoamine. Preferably, the polyunsaturated fatty acid is (Z)-9-octadecenoic acid, and the polyunsaturated fatty amine is (Z)-9-octadecenoamine. Preferably, in step S1, ultrasonic treatment is performed simultaneously with stirring, and the treatment is carried out at a power of 240-600W for 5-10 minutes.

[0014] Preferably, the volume of the polyunsaturated fatty acid accounts for 40%-60% of the reaction system, and the volume V1 of the polyunsaturated fatty acid is not less than the volume V2 of the polyunsaturated fatty acid. Amide microemulsion droplets are generated through an amidation reaction, and then some of the ferric ions in the system are reduced to divalent ions, ultimately forming magnetic ferrites. By controlling the amount of oleic acid and oleylamine in the reaction system, the volume and composition of the microemulsion droplets can be controlled, thereby affecting the growth of the ferrite particles, including their size and morphology, and thus influencing the electromagnetic properties of the absorbent. The electromagnetic absorption capacity of the absorbent can be controlled through simple control of the reaction system.

[0015] Preferably, the ratio of the polyunsaturated fatty acids, polyunsaturated fatty amines, and ferric iron raw materials is v1:v2:m = 120ml:80ml:14g. Alternatively, the ratio can be v1:v2:m = 100ml:100ml:14g, v1:v2:m = 80ml:120ml:14g, v1:v2:m = 100ml:100ml:12g, v1:v2:m = 80ml:120ml:12g, v1:v2:m = 100ml:100ml:15g, or v1:v2:m = 80ml:120ml:15g.

[0016] Preferably, step S2 specifically involves: preheating the reaction system at 220-240℃ for 25-45 minutes, then raising the temperature to 285-300℃ and holding it at that temperature for 30-45 minutes, followed by natural cooling to room temperature. Preferably, the reaction system is preheated at 230℃ for 30 minutes, then raised to 300℃ and held at that temperature for 30 minutes.

[0017] Preferably, the organic solvent in step S3 is composed of xylene and ethanol in a ratio of 1:1.

[0018] Preferably, the process parameters for drying in step S3 are: drying at 60-80℃ for 18-30 hours until the solid is in the form of a black powder.

[0019] A coating comprises 70-80 parts of an anti-corrosion nano-absorbing agent and 20-30 parts of resin. The anti-corrosion nano-absorbing agent is prepared by the method described in any one of claims 1-8, and the weight percentage of the amide polymer in the anti-corrosion nano-absorbing agent is 20-30%. The absorbing agent prepared by this invention has an effective absorption bandwidth of 10.5 GHz in the 2-18 GHz range, exhibiting excellent broadband wave absorption performance. When the absorbing agent is used as the main filler and mixed with resin, an anti-corrosion absorbing coating can be prepared. This coating can be applied to the outer surface of marine or coastal facilities and equipment, effectively reducing their radar cross-section and achieving radar stealth effect, thus possessing significant military and social benefits.

[0020] This invention discloses the application of the coating in the preparation of marine equipment.

[0021] Compared with existing technologies, the preparation method of the anti-corrosion nano-absorbing agent of the present invention has the following beneficial effects:

[0022] (1) This invention utilizes the reduction reaction mechanism of ferric iron in organic amide polymer droplets, and controls the proportion of organic raw materials in the raw materials to limit the growth volume environment of the material, thereby achieving the synthesis of nanomagnetic absorbers with different particle sizes and morphologies. At the same time, during the synthesis process, the organic ester compounds that encapsulate the magnetic absorbers are partially retained, so that they form an amide polymer protective film on the outside of the magnetic nanoparticles, blocking external environmental corrosion factors and enhancing the anti-corrosion performance of the nanomagnetic absorbers.

[0023] (2) This invention generates spatial volume constraint by controlling the proportion of reactants in the reaction process, thereby limiting and regulating the size growth of iron-based magnetic microwave absorber, changing the morphology and size of the final synthesized product and the magnetoelectric effect between materials, thereby controlling its electromagnetic parameters and optimizing electromagnetic wave absorption performance. When used as a functional filler in electromagnetic microwave absorbing coating, it can achieve the purpose of electromagnetic stealth and protection.

[0024] (3) The anti-corrosion nano-absorbing agent prepared by one-step hydrothermal method is carried out in a hydrophobic organic system. The nanoparticles are wrapped with an amide polymer layer to form a microcapsule structure during the synthesis process. The process is simple and the performance is adjustable. It can be applied to the synthesis and modification of other types of easily corroded magnetic materials and has great research value and application market.

[0025] (4) The reaction conditions of the present invention are simple and involve fewer types of equipment, which can meet the needs of large-scale production and application. Attached Figure Description

[0026] Figure 1 This is a scanning electron microscope image of the anti-corrosion nano-absorbing agent prepared in Example 1 of the present invention;

[0027] Figure 2 The electromagnetic parameters of the anti-corrosion nano-absorbing agent prepared in Example 1 of this invention are shown in the diagram.

[0028] Figure 3 The electromagnetic loss performance diagram of the anti-corrosion nano-absorbing agent prepared in Example 1 of the present invention is shown.

[0029] Figure 4 Scanning electron microscope image of the anti-corrosion nano-absorbing agent prepared in Example 2 of the present invention;

[0030] Figure 5 The electromagnetic parameters of the anti-corrosion nano-absorbing agent prepared in Example 2 of this invention are shown in the diagram.

[0031] Figure 6 The electromagnetic loss performance diagram of the anti-corrosion nano-absorbing agent prepared in Example 2 of the present invention is shown.

[0032] Figure 7 This is a scanning electron microscope image of the anti-corrosion nano-absorbing agent prepared in Example 3 of the present invention;

[0033] Figure 8 The electromagnetic parameters of the anti-corrosion nano-absorbing agent prepared in Example 3 of this invention are shown in the diagram.

[0034] Figure 9 The electromagnetic loss performance diagram of the anti-corrosion nano-absorbing agent prepared in Example 3 of the present invention is shown. Detailed Implementation

[0035] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Without conflict, the technical features in the embodiments of the present invention can be combined with each other. It should be noted that the heating rate of the heating steps in the entire preparation process is 2-10℃ / min. The embodiments of this application are merely for explanation and illustration, and not for limiting the present invention. Similar results are obtained when using ferric chloride, ferric nitrate, ferric sulfate, or other ferric raw materials, as well as oleic acid and oleylamine; similarly, similar results are obtained when using C12-C14 compounds to prepare the reaction system. Due to space limitations, these will not be described in detail here.

[0036] Example 1

[0037] A method for preparing an anti-corrosion nano-absorbing agent includes the following steps:

[0038] Step S1: Take 80ml of (Z)-9-octadecenoic acid, 120ml of (Z)-9-octadecenoamine, and 14g of acetylacetone iron, mix them together and disperse them thoroughly. After sonication, pour the mixed solution into a 250ml polytetrafluoroethylene high-temperature resistant liner. Then, put the polytetrafluoroethylene high-temperature resistant liner containing the mixed solution into an oven and heat it at 120℃ for 40 minutes to remove the water in the reaction system.

[0039] Step S2: After removing the water, insert the polytetrafluoroethylene liner containing the mixed solution into the stainless steel hydrothermal reactor shell, tighten it, and place it in the muffle furnace. Heat it to 230°C and maintain it for 30 minutes, then heat it to 300°C and maintain it for 30 minutes. Allow it to cool naturally until the whole thing reaches room temperature.

[0040] Step S3: Remove the polytetrafluoroethylene liner and pour out the solution after heating and reaction. Then, add 250 ml of xylene and 250 ml of ethanol to the mixed solution, stir mechanically for 30 minutes, and centrifuge to separate the solid product in the mixed solution. Dry the separated solid material at 60-80℃ for 24 hours until it is completely dry and in a black powder state, to obtain the anti-corrosion nano-absorbing agent sample coated with amide polymer. Its scanning electron microscope results are as follows: Figure 1 At this time, the size of the absorbing agent particles is about 50-100nm, and the morphology is basically octahedral.

[0041] The prepared sample was mixed with paraffin at a mass ratio of 80:20 and pressed into a ring with an inner diameter of 3.04 mm and an outer diameter of 7.00 mm. Electromagnetic parameters and electromagnetic loss performance were then tested using a vector network analyzer. The results are shown in [Figure number missing]. Figure 2-3 , Figure 3 The area within the black line represents the range where the sample's reflectivity is below -10dB, corresponding to an electromagnetic absorption capacity of 90% electromagnetic reflection efficiency. Calculations show that the effective absorption bandwidth of this sample in the 2-18GHz frequency range is 2.4GHz, corresponding to a coating thickness of 2.5mm.

[0042] Example 2

[0043] A method for preparing an anti-corrosion nano-absorbing agent includes the following steps:

[0044] Step S1: Take 100ml of (Z)-9-octadecenoic acid, 100ml of (Z)-9-octadecenoamine, and 14g of acetylacetone iron, mix them together, and then use an ultrasonic machine to fully disperse them. After ultrasonication, pour the mixed solution into a 250ml polytetrafluoroethylene high-temperature resistant reaction liner. Then, put the polytetrafluoroethylene high-temperature resistant liner containing the mixed solution into an oven and heat it at 115℃ for 45 minutes to remove the water in the reaction system.

[0045] Step S2: After removing the water, insert the polytetrafluoroethylene liner containing the mixed solution into the stainless steel hydrothermal reactor shell, tighten it, and place it in the muffle furnace. Heat it to 230°C and maintain it for 30 minutes, then heat it to 300°C and maintain it for 30 minutes. Allow it to cool naturally until the whole thing reaches room temperature.

[0046] Step S3: Remove the polytetrafluoroethylene liner and pour out the solution after heating and reaction. Then, add 250 ml of xylene and 250 ml of ethanol to the mixed solution, stir mechanically for 30 minutes, and centrifuge to separate the solid product in the mixed solution. This centrifugation step only separates the liquid phase from the solid phase. Dry the separated solid material at 60-80℃ for 24 hours until it is completely dry and in a black powder state. This is the product, and its scanning electron microscope results are as follows: Figure 4 At this point, the particle size grows to 200-400 nm, and it is basically in an octahedral state, with partial depressions appearing on all eight faces of the octahedron.

[0047] The prepared sample was mixed with paraffin at a mass ratio of 80:20 and pressed into a ring with an inner diameter of 3.04 mm and an outer diameter of 7.00 mm. Electromagnetic parameters and electromagnetic loss performance were then tested using a vector network analyzer. The results are shown in [Figure number missing]. Figure 5-6 Calculations show that the effective absorption bandwidth of this sample in the 2-18GHz frequency range is 6.2GHz, corresponding to a coating thickness of 2.3mm.

[0048] Example 3

[0049] Step S1: Take 120ml of (Z)-9-octadecenoic acid, 80ml of (Z)-9-octadecenoamine, and 14g of acetylacetone iron, mix them together, and then use an ultrasonic machine to fully disperse them. After ultrasonication, pour the mixed solution into a 250ml polytetrafluoroethylene high-temperature resistant reaction liner. Then, put the polytetrafluoroethylene high-temperature resistant liner containing the mixed solution into an oven and heat it at 125℃ for 35 minutes to remove the water in the reaction system.

[0050] Step S2: After removing the water, insert the polytetrafluoroethylene liner containing the mixed solution into the stainless steel hydrothermal reactor shell, tighten it, and place it in the muffle furnace. Heat it to 230°C and maintain it for 30 minutes, then heat it to 300°C and maintain it for 30 minutes. Allow it to cool naturally until the whole thing reaches room temperature.

[0051] Step S3: Remove the polytetrafluoroethylene liner and pour out the solution after heating and reaction. Then, add 250 ml of xylene and 250 ml of ethanol to the mixed solution, stir mechanically for 30 minutes, and centrifuge to separate the solid product in the mixed solution. This centrifugation step only separates the liquid phase from the solid phase. Dry the separated solid material at 60-80℃ for 24 hours until it is completely dry and in a black powder state. This is the product, which can be seen under a scanning electron microscope. Figure 7 At this point, the size of the absorbing agent particles remains at 200-400nm, but the degree of concavity on each facet intensifies, and the overall structure can no longer maintain the basic octahedral state.

[0052] The prepared sample was mixed with paraffin at a mass ratio of 80:20 and pressed into a ring with an inner diameter of 3.04 mm and an outer diameter of 7.00 mm. Electromagnetic parameters and electromagnetic loss performance were then tested using a vector network analyzer. The results are shown in [Figure number missing]. Figure 5-6 Calculations show that the effective absorption bandwidth of this sample in the 2-18GHz frequency range is 10.5GHz, corresponding to a coating thickness of 1.8mm.

[0053] As shown above, different proportions of raw materials in the synthesis reaction will change the microstructure and size of the final absorber, leading to changes in the electromagnetic parameters of the absorber, as well as the effective absorption bandwidth and corresponding matching thickness of the final coating. However, the absorbers prepared in this application all possess certain electromagnetic absorption properties. Specifically, when the absorber particles are larger, the real part of the dielectric constant of the coating material decreases by 2-3, while the imaginary part remains essentially unchanged. The real part curve of the permeability of the coating material is smooth, and the fluctuation is reduced. Conversely, when the absorber particles are smaller, the real part of the permeability of the material fluctuates within a certain range, with more obvious peaks. In other words, as the particle morphology increases, the overall electromagnetic parameters tend to develop towards a more stable state, which is beneficial for maintaining the balance between impedance matching and attenuation performance of the material.

[0054] The electromagnetic absorption performance of the anti-corrosion nano-absorbing agent described in this application mainly originates from the electromagnetic absorption effect of ferromagnetic materials. The magnetism of the material system originates from the regular arrangement of crystal molecules. Under the action of an electromagnetic field, the molecular currents inside the material are induced to orient in a regular manner, resulting in a magnetization effect and a tendency to move. When the solid volume is limited, it restricts movement and hinders this tendency to move. In this process, the absorbed electromagnetic energy is converted into electrical energy. When the particle size is small, the degree of hindrance is small, and the effect on electromagnetic waves of different frequencies varies greatly, resulting in a narrower effective absorption bandwidth. However, when the particle size is large, while the magnetic state of the material remains the same, the spatial confinement effect on the particles is enhanced, the response effect to electromagnetic waves of different bands is enhanced, the effective absorption bandwidth is significantly increased, and the electromagnetic absorption effect is improved.

[0055] Corrosion resistance test

[0056] The microwave absorbing agents prepared in Examples 1-3 were mixed with resin binders at a weight ratio of 8:2 and coated onto metal surfaces to form coatings. Salt spray resistance tests were then conducted on these coatings. The results showed that the coatings corresponding to the microwave absorbing agents prepared in Examples 1-3 exhibited no blistering, peeling, or corrosion after 1500 hours of salt spray testing.

[0057] This invention utilizes a specific synthesis process to form an amidation reaction on the outer layer of particles, resulting in an amide polymer. This polymer is not only soluble in xylene-based organic solvents and exhibits good dispersibility and miscibility in resin systems, but also has numerous hydrophobic groups distributed on its surface that can isolate water molecules and salts from the external environment, preventing the internal microwave absorber from being corroded by water.

[0058] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A coating, characterized in that, The anti-corrosion nano wave absorber 70-80 parts, resin 20-30 parts, the weight of the amide polymer in the anti-corrosion nano wave absorber accounts for 20-30%. The preparation method of the anti-corrosion nano wave absorber comprises: Step S1: mixing polyunsaturated fatty acid, polyunsaturated fatty amine and trivalent iron raw materials in stirring until they are uniformly mixed, the amount ratio of the polyunsaturated fatty acid, polyunsaturated fatty amine and trivalent iron raw materials is v1:v2:m=(80-120)ml:(80-120)ml:(10-18)g, then heating at 100-150℃ for 20-60min to remove moisture; Step S2: preheating the reaction system at 200-250℃ for 20-60min, then heating to 270-300℃ for 20-60min, and naturally cooling to room temperature; Step S3: pouring out the solution after heating reaction, then adding organic solvent according to the mass-volume ratio of 1:(1.5-3), and performing solid-liquid separation after mechanical stirring for 20-50min, and drying the solid to obtain the product; The organic solvent in step S3 is composed of dimethylbenzene:ethanol=1:1; The microstructure of the wave absorber is in the form of nanoparticles, and the particle size is 50-200nm; The trivalent iron raw material is one of acetylacetone iron, ferric chloride, ferric nitrate and ferric sulfate; The polyunsaturated fatty acid is (Z)-9-octadecenoic acid, and the polyunsaturated fatty amine is (Z)-9-octadecenylamine.

2. The coating of claim 1, wherein, The volume of the polyunsaturated fatty acid accounts for 40%-60% of the reaction system, and the volume V1 of the polyunsaturated fatty acid is not less than the volume V2 of the polyunsaturated fatty acid.

3. The coating of claim 1, wherein, The amount ratio of the polyunsaturated fatty acid, polyunsaturated fatty amine and trivalent iron raw material is v1:v2:m=120ml:80ml:14g.

4. The coating of claim 1, wherein, Step S2 specifically is: preheating the reaction system at 220-240℃ for 25-45min, then heating to 285-300℃ for 30-45min, and naturally cooling to room temperature.

5. The coating of claim 1, wherein, The process parameters of the drying operation in step S3 are: drying at 60-80℃ for 18-30h until the solid is in the form of black powder.

6. The use of the coating of claim 1 in the preparation of marine equipment.

Images