A microwave absorber, a wave-absorbing slurry, a wave-absorbing patch and a preparation method thereof

Abstract

The application belongs to the technical field of wave-absorbing materials, and discloses a microwave absorber, wave-absorbing slurry, wave-absorbing patch and a preparation method thereof. The microwave absorber comprises microwave dielectric material or / and microwave magnetic material and magnetic metal micropowder. Through selection and proportioning calculation of the microwave dielectric material and the microwave magnetic material, dosage adjustment of the absorber, air spraying and a series of post-treatment, a composite wave-absorbing patch with smooth surface, low porosity, uniform thickness and stable wave-absorbing performance is finally obtained. The prepared wave-absorbing patch material has small density, light mass, certain flexibility and wide effective absorption bandwidth, and effectively improves the problems of low absorption efficiency, large density and heavy mass of traditional wave-absorbing materials which use a high proportion of magnetic metal micropowder as an absorber to prepare wave-absorbing patches / coatings.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing materials technology, specifically relating to a microwave absorber, a microwave absorbing paste, a microwave absorbing patch, and a method for preparing the same. Background Technology

[0002] The evolving countermeasures of radar stealth and detection technologies, along with the widespread adoption of various electronic devices, have created an urgent demand for microwave absorbing materials. High-performance microwave absorbing materials must possess characteristics such as light weight, thinness, wide bandwidth, and strong absorption performance. To obtain high-performance microwave absorbing coating materials, selecting appropriate absorbers and matrices, as well as feasible processing techniques, are crucial. Resin and rubber-based microwave absorbing materials are widely used in the field of microwave absorbing materials due to their simple preparation and molding processes, flexibility, and low production costs.

[0003] Developing high-performance absorbers is key to improving the microwave absorption performance of absorbing coatings. Researching the electromagnetic properties, content, and matching selection of absorbers is crucial for achieving ideal absorption effects. Currently, most commercially available absorbing materials rely on resin / rubber-based absorbing materials prepared from magnetic metal micropowders using specific processes. The main problems include high bulk density and areal density, excessively strong loss characteristics resulting in a wide absorption bandwidth but low absorption efficiency, making it difficult for single-phase absorbers to achieve ideal absorption effects. The introduction of dual-loss absorbers, combining two different loss mechanisms, can further optimize the absorption performance of coatings. In particular, the preparation of lightweight dual-loss absorbers is of great practical significance for improving the overall performance of absorbing materials. Summary of the Invention

[0004] The purpose of this invention is to provide a microwave absorber, a microwave absorbing paste, a microwave absorbing patch, and a method for preparing the same, which solves the problems of high bulk density, heavy weight, and even low microwave absorption efficiency that arise from the use of a large amount of magnetic metal micropowder as an absorber to prepare microwave absorbing coatings in traditional microwave absorbing materials.

[0005] This invention is achieved through the following technical solution:

[0006] A microwave absorber comprising magnetic metal micropowder and microwave dielectric material;

[0007] The mass ratio of microwave dielectric material to magnetic metal powder is 1-7:1-3.

[0008] Furthermore, the magnetic metal powder is carbonyl iron powder or FeSiAl powder;

[0009] The microwave dielectric material is LiNb 0.8 Ti 0.25 O3 ceramic powder.

[0010] The present invention also discloses a microwave absorber, comprising magnetic metal micro powder and microwave magnetic medium material;

[0011] The mass ratio of microwave magnetic dielectric material to magnetic metal powder is 1 to 4:1.

[0012] Furthermore, the magnetic metal powder is carbonyl iron powder or FeSiAl powder;

[0013] The microwave magnetic dielectric material is ferrite material Ba3Co2Fe. 24 O 41 Ceramic powder.

[0014] The present invention also discloses a microwave absorber, comprising magnetic metal micro powder, microwave dielectric material and microwave magnetic dielectric material;

[0015] The mass ratio of microwave dielectric material, microwave magnetic dielectric material and magnetic metal powder is (1-3):1:(1-3).

[0016] Furthermore, the magnetic metal powder is carbonyl iron powder or FeSiAl powder;

[0017] The microwave dielectric material is LiNb 0.8 Ti 0.25 O3 ceramic powder;

[0018] The microwave magnetic dielectric material is ferrite material Ba3Co2Fe. 24 O 41 Ceramic powder.

[0019] The present invention also discloses a method for preparing the microwave absorber, wherein the raw materials are mixed in a designed ratio and then ball-milled, dried, ground, and sieved to obtain a composite powder, which is then the microwave absorber.

[0020] The present invention also discloses a microwave absorbing slurry, comprising a binder, a curing agent, a toughening agent, a defoamer, a dispersant, and a solvent, and the microwave absorber;

[0021] The binder, curing agent, toughening agent, defoamer, dispersant and microwave absorber are cured products. Based on the mass of the cured product as 100%, the total amount of binder, curing agent, toughening agent, defoamer and dispersant accounts for 15% to 35%, and microwave absorber accounts for 65% to 85%.

[0022] Further, the binder, curing agent, toughening agent, defoamer and dispersant are dissolved in acetone and mixed, and then homogenized and dispersed to obtain a resin slurry;

[0023] Microwave absorber is added to resin slurry and homogenized to obtain microwave absorbing slurry.

[0024] The present invention also discloses a method for preparing a microwave absorbing patch based on the microwave absorbing paste, comprising the following steps:

[0025] Cut out release paper of regular size and paste it onto the metal substrate, then place it horizontally in the central area of ​​the water curtain cabinet;

[0026] The microwave absorbing paste is poured into the feed chamber of the spray gun in small amounts multiple times. The airflow and feed amount are adjusted. The microwave absorbing paste is sprayed multiple times intermittently using the air spraying method, with an interval of 3 to 8 minutes between each spraying, to spray a uniform coating on the substrate.

[0027] After curing at room temperature, a semi-cured coating material is obtained, which is then peeled off flat from the release paper as a precursor for the microwave absorbing patch.

[0028] In the semi-cured state, the precursor of the microwave absorbing patch is rolled multiple times. The thickness of each roll is adjusted according to the actual thickness of the patch, and the rolling direction is continuously adjusted until the target thickness is reached.

[0029] After rolling, the metal plate is statically pressed and cured at room temperature to obtain the final microwave absorbing patch.

[0030] Compared with the prior art, the present invention has the following beneficial technical effects:

[0031] This invention discloses a microwave absorber comprising magnetic metal micropowder and a microwave dielectric material. By adding the microwave dielectric material, the impedance matching characteristics are effectively adjusted by regulating the real part of the microwave dielectric constant, thereby significantly enhancing the electromagnetic wave absorption effect. Compared with using only a single magnetic metal micropowder absorber, the coating and patch materials prepared by this invention have advantages such as low density and good absorption effect.

[0032] This invention discloses a microwave absorber comprising magnetic metal micropowder and a microwave magnetic dielectric material. By adding the microwave magnetic dielectric material to effectively adjust the imaginary part of the permeability, impedance matching characteristics are modified, thereby improving electromagnetic wave absorption performance. Compared to absorbers using a high proportion of magnetic metal micropowder, the resin-based absorbing coating and patch materials prepared by this invention have advantages such as low bulk density and areal density, and high absorption efficiency at specific thicknesses.

[0033] This invention discloses a microwave absorber comprising magnetic metal micropowder, a microwave dielectric material, and a microwave magnetic dielectric material. The composite absorber exhibits multiple losses, including dielectric loss, magnetic loss, and conductivity loss, offering unique advantages in effectively and precisely controlling the resistance and reactance for impedance matching. The addition of the dielectric material effectively improves capacitive reactance characteristics, while the addition of the magnetic dielectric material effectively controls resistive characteristics, synergistically optimizing the microwave absorption performance of the composite absorber. Compared to absorbers using a high proportion of magnetic metal micropowder, this invention offers advantages such as lower bulk density and areal density, and higher microwave absorption efficiency at specific thicknesses.

[0034] This invention discloses a method for preparing a microwave absorbing slurry, including the ratio of microwave absorber to resin matrix, and the amount of toughening agent, defoamer, and dispersant added to the absorbing slurry. The total amount of binder, curing agent, toughening agent, defoamer, and dispersant accounts for 15% to 35% of the total solid content of the absorbing slurry by mass, and the microwave absorber accounts for 65% to 85% of the total solid content of the absorbing slurry by mass. The resin-based composite absorbing slurry can be effectively controlled according to the absorber ratio and thickness, and can meet the "thin, light, wide, and strong" microwave absorption effect in specific frequency bands according to actual needs.

[0035] This invention discloses a method for preparing a microwave absorbing patch. Release paper is used as the contact layer during patch spraying, facilitating the intact removal of the resin layer in its semi-cured state. Combined with an air spraying process, the dispersed microwave absorbing slurry is poured into the feed chamber of the spray gun in small, frequent passes, adjusting the airflow and feed rate. The slurry is then intermittently sprayed multiple times in a water curtain chamber using an air spraying method, with each spraying interval being 3–8 minutes. This creates a coating of uniform thickness on a substrate with the release paper attached. Once the coating is semi-cured, it is removed from the release paper and rolled to achieve a uniform thickness and smooth surface, improving the patch's smoothness and density while strictly controlling its thickness. After rolling, the patch is placed at room temperature to fully cure, resulting in the microwave absorbing patch. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the preparation process of the present invention.

[0037] Figure 2 This is a physical image of the absorbing patch prepared in Example 1.

[0038] Figure 3 The electromagnetic parameters of the absorbing patch prepared in Example 1 are shown in the following figures: (a) Real part of dielectric constant; (b) Imaginary part of dielectric constant; (c) Real part of permeability; (d) Imaginary part of permeability.

[0039] Figure 4 The reflection loss diagrams of the absorbing patch prepared for Example 1 are as follows: (a) The figure shows the simulated reflection loss diagrams at different thicknesses; (b) The figure shows the measured reflection loss diagram at a thickness of 1.6 mm.

[0040] Figure 5 The reflection loss diagrams of the absorbing patch prepared for Example 2 are as follows: (a) The figure shows the simulated reflection loss diagrams at different thicknesses; (b) The figure shows the measured reflection loss diagram at a thickness of 1.7 mm.

[0041] Figure 6 The image shows the microstructure of the composite powder prepared in Example 3.

[0042] Figure 7The image shows the cross-sectional microstructure of the absorbing patch prepared in Example 3.

[0043] Figure 8 The reflection loss diagrams of the absorbing patch prepared in Example 3 are as follows: (a) The figure shows the simulated reflection loss diagrams at different thicknesses; (b) The figure shows the measured reflection loss diagram at a thickness of 1.1 mm.

[0044] Figure 9 The reflection loss diagrams of the absorbing patch prepared in Example 4 are as follows: (a) The figure shows the simulated reflection loss diagrams at different thicknesses; (b) The figure shows the measured reflection loss diagram at a thickness of 1.3 mm. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0046] The components described and illustrated in the accompanying drawings and embodiments of this invention can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely to illustrate one selected embodiment of the invention. All other embodiments obtained by those skilled in the art based on the accompanying drawings and embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0047] It should be noted that the terms “comprising,” “including,” or any other variations are intended to cover non-exclusive inclusion, such that a process, element, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to the process, element, method, article, or apparatus.

[0048] This invention discloses a microwave absorber comprising magnetic metal micropowder, and microwave dielectric material and / or microwave magnetic dielectric material, forming a two-phase or three-phase composite.

[0049] Specifically, the microwave dielectric material is LiNb microwave dielectric ceramic powder synthesized by solid-state reaction method. 0.8 Ti 0.25 O3; the microwave magnetic medium material is ferrite ceramic powder Ba3Co2Fe prepared by solid-state reaction method. 24 O 41The magnetic metal powder is carbonyl iron powder or FeSiAl powder. This lightweight absorbent design is universally applicable to the selection of microwave dielectric materials with high dielectric constant, microwave magnetic dielectric materials with high magnetic permeability, and metal powders with high magnetic loss. Therefore, the scope of protection for specific materials is not limited to the specific materials mentioned in this invention.

[0050] The present invention also designs a microwave absorbing slurry, comprising a binder, a curing agent, a toughening agent, a defoamer, a dispersant, and a solvent, as well as the microwave absorber; the binder, curing agent, toughening agent, defoamer, dispersant, and microwave absorber are cured products, and based on the mass of the cured product as 100%, the total amount of the binder, curing agent, toughening agent, defoamer, and dispersant accounts for 15% to 35%; the microwave absorber accounts for 65% to 85%.

[0051] The adhesive used is bisphenol A type epoxy resin E-40, the curing agent is polyamide 651, the toughening agent is waterborne polyurethane P-522, and the solvent is acetone.

[0052] Bisphenol A type epoxy resin has high transparency, strength, and adhesive strength, as well as certain toughness and corrosion resistance. E-40 epoxy resin is a common resin; this type of resin can form a variety of high-performance cured products with various curing agents, additives, and absorbents. It produces virtually no small-molecule volatiles during curing, has good processability, and a simple preparation process. Polyamide 651 is a chemical substance used as a toughening curing agent for bisphenol A type epoxy resin, with an amine value of 380–450 mg / KOH / g. The curing conditions are room temperature curing for 48 hours or 65°C curing for 4 hours. Polyamide 651 cures faster than low-molecular-weight polyamide 650. Therefore, this invention uses bisphenol A type E-40 epoxy resin as the binder and polyamide 651 as the curing agent.

[0053] This invention also discloses a method for preparing a microwave absorber, specifically:

[0054] After mixing magnetic metal micro powder, microwave dielectric material and / or microwave magnetic dielectric material, the mixture is ball-milled for 10-20 hours, then dried at 50°C, ground and sieved to obtain composite powder. Anhydrous ethanol is used as a grinding aid during the ball milling process.

[0055] The preparation method of microwave absorbing slurry is also disclosed. A specific amount of epoxy resin, polyamide curing agent, waterborne polyurethane, defoamer and dispersant are weighed and dispersed by a high-speed homogenizing disperser to obtain a resin slurry. Then, composite powder is added to the resin slurry to obtain a composite slurry, and it is stirred and dispersed by a high-speed homogenizing disperser to obtain microwave absorbing slurry.

[0056] The specific steps for preparing the absorbing patch based on the absorbing paste obtained above are as follows:

[0057] Cut out release paper of regular size and paste it onto the metal substrate, then place it horizontally in the central area of ​​the water curtain cabinet;

[0058] The microwave absorbing slurry is poured into the feed chamber of the spray gun in small amounts multiple times. With the assistance of the air compressor, the appropriate airflow and feed amount are adjusted. The composite slurry is sprayed intermittently multiple times in the water curtain cabinet using the air spraying method to prepare a coating with uniform thickness on a regular flat plate.

[0059] A sample of a specific thickness and size is sprayed and cured at room temperature for 10-15 hours to obtain a lightweight microwave absorbing coating based on epoxy resin, which is a composite of dielectric, magnetic medium and magnetic metal micro powder. The flexible coating is peeled off as a precursor for the microwave absorbing patch.

[0060] The microwave absorbing patch is rolled multiple times using a rolling mill while it is in a semi-cured state to improve the smoothness and density of the patch and to control the thickness of the microwave absorbing patch.

[0061] After rolling, the lightweight microwave absorbing patch is cured by static pressing of a metal plate at room temperature for 48 hours to obtain the finished product.

[0062] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0063] Example 1

[0064] like Figure 1 As shown, this embodiment describes a method for preparing a lightweight magnetic dielectric material + magnetic metal micropowder composite resin-based microwave absorbing patch. The specific preparation method includes the following steps:

[0065] Step 1: Preparation of Ba3Co2Fe 24 O 41 (Co2Z) powder.

[0066] The raw materials BaCO3, Fe2O3, and Co2O3 were mixed according to the formula Ba3Co2Fe 24 O 41 The stoichiometric ratios of the raw materials were measured separately in a dry environment. The raw materials were thoroughly mixed by wet ball milling, and the resulting slurry was completely dried at 50°C. After grinding and sieving, ferrite ceramics Ba3Co2Fe were synthesized using a solid-state reaction method. 24 O 41 Powder.

[0067] Step 2: Prepare Co2Z@CIP composite powder.

[0068] Ba3Co2Fe 24 O 41Powdered and granular CIP were weighed and placed into a stainless steel ball mill jar at mass ratios of 1:1, 2:1, 3:1, and 4:1. The composite powder was mixed with stainless steel balls (3-6 mm in diameter) at a ball-to-powder ratio of 10:1. Anhydrous ethanol was used as a grinding aid, and a planetary ball mill was used at a speed of 300 rpm to mix Ba3Co2Fe. 24 O 41 Powdered and granular CIP powders were ball-milled for 18 hours. The ball-milled Co2Z@CIP mixture was completely dried at 50°C, and after grinding and sieving, four composite powders of magnetic media material + magnetic metal micro powder with different mass ratios were obtained.

[0069] Step 3: Prepare resin slurry.

[0070] Dissolve 20g of bisphenol A type epoxy resin E-40 and 5g of curing agent polyamide 651 in acetone, add 3g of P-522 waterborne polyurethane, 1g of defoamer and 1g of dispersant, and then use a high-speed homogenizer to stir and disperse at a rate of 3kr / min for 10min to obtain resin slurry.

[0071] Step 4: Prepare microwave absorbing paste.

[0072] Subsequently, 70g of each of the four different mass ratios of Co2Z@CIP composite powder were slowly poured into the above resin slurry, and then uniformly dispersed for 1 hour at a rate of 3kr / min using a high-speed homogenizer to obtain the microwave absorbing slurry.

[0073] Step 5: Apply the coating.

[0074] The dispersed microwave absorbing slurry is poured into the feed chamber of the spray gun in small amounts multiple times. With the assistance of an air compressor, the appropriate airflow and feed rate are adjusted. The composite slurry is sprayed intermittently multiple times in a water curtain cabinet using an air spraying method, with each spraying interval being 3 minutes. A coating with uniform thickness is prepared on a regular flat plate.

[0075] Step Six: Rolling Operation.

[0076] When the coating is semi-cured, it needs to be peeled off the plate and rolled to reduce defects such as internal pores and cracks. By gradually reducing the thickness and rolling in different directions multiple times, the smoothness and density of the patch are improved, and the thickness of the absorbing patch is strictly controlled.

[0077] Step 7: Curing and shaping.

[0078] After rolling, it is placed at room temperature and allowed to fully solidify to obtain the following result: Figure 2 The Co2Z@CIP epoxy resin-based microwave absorbing patch shown.

[0079] Electromagnetic parameters of the Co2Z@CIP epoxy resin-based absorbing patch were tested, and the results were as follows: Figure 3 The electromagnetic parameters shown are: Figure 3 Figures (a) and (b) in the figure illustrate that both the real and imaginary parts of the dielectric constant decrease as the proportion of the magnetic medium increases; Figure 3 Figures (c) and (d) illustrate that by adding a magnetic dielectric material, the imaginary part of the permeability of the composite material is significantly reduced while the real part of the permeability remains relatively unchanged. Since magnetic loss is the main loss mechanism of this type of material, the reduction of the real and imaginary parts of the dielectric constant does not significantly weaken the loss characteristics of the material. By effectively controlling the size of the imaginary part of the permeability, the magnetic loss characteristics of the patch material can be controlled within a large range.

[0080] Table 1 shows the densities, absorption bandwidths, and absorption peak data of the 1:1, 2:1, 3:1, and 4:1 patch materials at partial thicknesses. Among them, the patch materials with Co2Z to CIP mass ratios of 1:1 and 2:1 effectively cover the X-band (8.2–12.4 GHz) with absorption bandwidths (RL ≤ -8 dB) at thicknesses of 1.6 mm and 1.9 mm, respectively, and have densities of 2.08 g / cm³. 3 and 1.96 g / cm 3 Compared to commonly available absorbing patches, the density is significantly reduced. When the Co2Z to CIP mass ratio is 3:1 and 4:1, the patch material density is slightly reduced, but the absorption peak and effective absorption bandwidth in the X (8.2~12.4GHz) and Ku (12.4~18GHz) bands are weakened.

[0081] Table 1

[0082]

[0083] like Figure 4 As shown, the reflectivity of the absorbing patch prepared in this embodiment was tested, and the results were analyzed and compared. Figure 4 Figure (a) shows that the Co2Z@CIP patch prepared in this embodiment, with a composite absorber mass ratio of Co2Z:CIP = 1:1 and a thickness of 2.0 mm, can achieve a C2 full-band reflectivity of less than -8 dB, a minimum reflection loss of -27 dB (7.5 GHz), and an effective absorption bandwidth of 4.87 GHz (5.51–10.38 GHz). Through observation and comparison… Figure 4 Figure (b) shows that the absorbing patch has a wide effective absorption bandwidth and good absorption effect. By comparing the measured reflection loss with the simulated reflection loss, it can be found that the measured results are basically consistent with the simulation results.

[0084] Example 2

[0085] This embodiment describes a method for preparing a lightweight dielectric material + magnetic metal micropowder composite resin-based microwave absorbing patch. The specific preparation method includes the following steps:

[0086] Step 1: Prepare LNT powder.

[0087] First, according to LiNb 0.8 Ti 0.25 To determine the stoichiometric ratio of O3, the raw materials Li2CO3, Nb2O5, and TiO2 were weighed separately in a dry environment. The raw materials were thoroughly mixed using wet ball milling. The resulting slurry was then completely dried at 50°C, ground, and sieved before being synthesized into LNT powder using a solid-state reaction method.

[0088] Step 2: Prepare LNT@FeSiAl composite powder.

[0089] 100g each of LNT and FeSiAl powders were weighed and placed into a stainless steel ball mill jar at mass ratios of 2:3, 1:1, and 3:2. The composite powder was mixed with stainless steel balls with a diameter of 3-6mm at a ball-to-powder ratio of 10:1. Anhydrous ethanol was used as a grinding aid, and the LNT and FeSiAl powders were ball-milled at 250 rpm for 18 hours using a planetary ball mill. The ball-milled LNT@FeSiAl mixture was completely dried, ground, and sieved to obtain four different mass ratios of LNT@FeSiAl composite powders.

[0090] Step 3: Prepare resin slurry.

[0091] Dissolve 20g of bisphenol A type epoxy resin E-40 and 5g of polyamide 651 in acetone at a mass ratio of 4:1. Add 3g of P-522 waterborne polyurethane, 1g of defoamer and 1g of dispersant, and then disperse evenly for 10min using a homogenizer at a rate of 3kr / min.

[0092] Step 4: Prepare microwave absorbing paste.

[0093] Subsequently, 70g of each of the four different mass ratios of LNT@FeSiAl composite powder were slowly poured into the above resin slurry, and then uniformly dispersed for 1 hour at a rate of 3kr / min using a homogenizer to obtain the microwave absorbing slurry.

[0094] Step 5: Apply the coating.

[0095] The dispersed microwave absorbing slurry is poured into the feed chamber of the spray gun in small amounts multiple times. With the assistance of an air compressor, the appropriate airflow and feed rate are adjusted. The composite slurry is sprayed intermittently multiple times in a water curtain cabinet using an air spraying method, with each spraying interval being 5 minutes. A coating with uniform thickness is prepared on a regular flat plate.

[0096] Step Six: Rolling Operation.

[0097] When the coating is semi-cured, it needs to be peeled off the plate and rolled to reduce defects such as internal pores and cracks. By gradually reducing the thickness and rolling in different directions multiple times, the smoothness and density of the patch are improved, and the thickness of the absorbing patch is strictly controlled.

[0098] Step 7: Curing and shaping.

[0099] After rolling, it is placed at room temperature for 48 hours to allow it to fully solidify, resulting in the following: Figure 2 The lightweight LNT@FeSiAl epoxy resin-based microwave absorbing patch shown.

[0100] like Figure 5 As shown, the reflectivity of the absorbing patch prepared in this embodiment was calculated and tested, and the results were analyzed and compared. Figure 5 Figure (a) shows that the LNT@FeSiAl patch prepared in this embodiment, with a composite absorber mass ratio of LNT:FeSiAl = 2:3 and a thickness of 1.8 mm, can achieve a full-band X-band reflectivity of less than -8 dB, a minimum reflection loss of -17.6 dB (10.2 GHz), and an effective absorption bandwidth of 4.3 GHz (8.1–12.4 GHz). Through observation and comparison… Figure 5 Figure (b) shows that the absorbing patch has a wide effective absorption bandwidth and good absorption effect. The measured results are close to the simulation results.

[0101] Table 2 shows the densities of the 2:3, 1:1, and 3:2 patch materials, as well as the absorption bandwidth and absorption peak data at certain thicknesses. Among them, the patch with a LNT to FeSiAl mass ratio of 2:3 can achieve full coverage of the effective absorption bandwidth (RL≤-8dB) in the X-band (8.2~12.4GHz) at a thickness of only 1.8mm, with a patch density of only 1.86g / cm³. 3 When the LNT to FeSiAl mass ratio is 1:1, the patch can achieve full coverage of the C1 band (3.85~5.85GHz) effective absorption bandwidth (RL≤-8dB) with a thickness of only 3.0mm, and the patch density is only 1.72g / cm³. 3 When the mass ratio of LNT to FeSiAl is 3:2, the effective absorption bandwidth of the patch at a thickness of 3mm is weaker than the previous group, but the density is reduced.

[0102] Table 2

[0103]

[0104] Example 3

[0105] This embodiment describes a method for preparing a lightweight dielectric material + magnetic metal micropowder composite resin-based microwave absorbing patch. The specific preparation method includes the following steps:

[0106] Step 1: Prepare LNT powder.

[0107] First, according to LiNb 0.8 Ti 0.25 To determine the stoichiometric ratio of O3, the raw materials Li2CO3, Nb2O5, and TiO2 were weighed separately in a dry environment. The raw materials were thoroughly mixed using wet ball milling. The ball-milled LNT mixture was then completely dried at 50°C. After grinding and sieving, LiNb dielectric ceramic powder was synthesized using a solid-state reaction method. 0.8 Ti 0.25 O3 (LNT powder).

[0108] Step 2: Prepare LNT@CIP composite powder.

[0109] 100g of LNT powder and granular CIP were weighed and placed into a stainless steel ball mill jar at mass ratios of 1:1, 2:1, 3:1, and 4:1, respectively. The composite powder was mixed with stainless steel balls with a diameter of 3–6 mm at a ball-to-powder ratio of 10:1. Anhydrous ethanol was used as a grinding aid, and the LNT powder and granular CIP powder were ball-milled at 300 rpm for 18 hours. The ball-milled LNT@CIP mixture was completely dried, ground, and sieved to obtain four different mass ratios of LNT@CIP composite powder.

[0110] Step 3: Prepare resin slurry.

[0111] Dissolve 20g of bisphenol A type epoxy resin E-40 and 5g of polyamide 651 in acetone, add 3g of toughening P-522 waterborne polyurethane, 1g of defoamer and 1g of dispersant, and then use a high-speed homogenizer to uniformly disperse at a rate of 3kr / min for 10min.

[0112] Step 4: Prepare microwave absorbing paste.

[0113] Subsequently, 70g of each of the four LNT@CIP composite powders with different mass ratios were slowly poured into the above resin slurry, and then uniformly dispersed for 1 hour at a rate of 3kr / min using a high-speed homogenizer to obtain the composite slurry.

[0114] Step 5: Apply the coating.

[0115] The dispersed microwave absorbing slurry is poured into the feed chamber of the spray gun in small amounts multiple times. With the assistance of an air compressor, the appropriate airflow and feed rate are adjusted. The composite slurry is sprayed intermittently multiple times in a water curtain cabinet using an air spraying method, with each spraying interval being 6 minutes. A coating with uniform thickness is prepared on a regular flat plate.

[0116] Step Six: Rolling Operation.

[0117] When the coating is semi-cured, it needs to be peeled off the plate and rolled to reduce defects such as internal pores and cracks. By gradually reducing the thickness and rolling in different directions multiple times, the smoothness and density of the patch are improved, and the thickness of the absorbing patch is strictly controlled.

[0118] Step 7: Curing and shaping.

[0119] After rolling, the LNT@CIP epoxy resin-based microwave absorbing patch is placed at room temperature for 48 hours to allow it to fully cure.

[0120] After scanning electron microscopy observation of the composite powder, the following results were obtained: Figure 6 The SEM image shown clearly reveals a large number of LNT particles coated on the flake-shaped carbonyl iron powder, with some LNT particles dispersed around the flake-shaped carbonyl iron powder. Electron scanning of the LNT@CIP epoxy resin-based microwave absorbing patch yielded the following results: Figure 7 The SEM image shown clearly shows that some LNT particles are coated on the flake carbonyl iron powder, while some LNT particles are dispersed around the carbonyl iron powder. It can also be seen that the absorbent LNT particles and flake CIP are relatively uniformly dispersed in the resin matrix.

[0121] like Figure 8 As shown, the reflectivity of the absorbing patch prepared in this embodiment was tested and calculated, and the results were analyzed and compared. Figure 8 Figure (a) shows that the LNT@CIP patch prepared in this embodiment, with a composite absorber mass ratio of LNT:CIP = 1:1 and a thickness of 1.1 mm, can achieve a Ku-band reflectivity of less than -8 dB, a minimum reflection loss of -22.2 dB (14.02 GHz), and an effective absorption bandwidth of 7.34 GHz (10.6–18 GHz). Through observation and comparison… Figure 8 Figure (b) shows that the absorbing patch has a wide effective absorption bandwidth and good absorption effect. A comparison between the measured reflection loss and the simulated reflection loss indicates that the measured results are close to the simulation results.

[0122] Table 3 shows the density of the patch materials at ratios of 1:1, 2:1, 3:1, and 4:1, as well as the absorption bandwidth and absorption peak data at certain thicknesses. When the LNT to CIP mass ratios are 1:1 and 2:1, respectively, the effective absorption bandwidth of the patch materials with thicknesses of only 1.1 mm and 1.2 mm can cover the Ku band (12.4–18 GHz), and the density is only 1.93 g / cm³. 3 and 1.68 g / cm 3 When the LNT to CIP mass ratio is 3:1, a 1.7mm thick patch material can achieve full X-band absorption bandwidth with a density of 1.6g / cm³. 3 When the LNT to CIP quality ratio is 4:1, a 2.2mm thick patch can achieve a high proportion of C2 band (5.85–8.2GHz) absorbing bandwidth with a density of only 1.53g / cm³. 3 .

[0123] Table 3

[0124]

[0125] Example 4

[0126] This embodiment describes a method for preparing a lightweight dielectric material + magnetic metal micropowder + magnetic dielectric material epoxy resin-based microwave absorbing coating. The specific preparation method includes the following steps:

[0127] Step 1: Preparation of LNT powder by solid-state reaction method.

[0128] First, according to LiNb 0.8 Ti 0.25 To determine the stoichiometric ratio of O3, the raw materials Li2CO3, Nb2O5, and TiO2 were weighed separately in a dry environment. The raw materials were thoroughly mixed using wet ball milling. The ball-milled LNT slurry was then completely dried at 50°C, ground, and sieved before being used to synthesize LNT powder via a solid-state reaction method.

[0129] Step 2: Prepare Co2Z powder.

[0130] The raw materials BaCO3, Fe2O3, and Co2O3 were mixed according to the formula Ba3Co2Fe 24 O 41 The stoichiometric ratios of the raw materials were measured separately in a dry environment. Several powder raw materials were mixed evenly by wet ball milling. The Co2Z mixture after ball milling was completely dried at 50°C, ground and sieved, and then Co2Z powder was synthesized by solid-state reaction method.

[0131] Step 3: Prepare LNT@Co2Z@CIP composite powder.

[0132] 100g of LNT, CIP, and Co2Z powders were weighed and placed into a stainless steel ball mill jar at mass ratios of 1:1:1, 2:1:1, and 1:2:1. The composite powder was mixed with stainless steel balls with a diameter of 3–6 mm at a ball-to-powder ratio of 10:1. Anhydrous ethanol was used as the milling medium, and the LNT, Co2Z, and CIP powders were ball-milled at 300 rpm for 18 hours using a planetary ball mill. The ball-milled LNT@Co2Z@CIP mixture was completely dried, ground, and sieved to obtain three LNT@Co2Z@CIP composite powders with different mass ratios.

[0133] Step 4: Prepare resin slurry.

[0134] Dissolve 20g of bisphenol A type epoxy resin E-40 and 5g of polyamide 651 in acetone, add 3g of P-522 waterborne polyurethane, 1g of defoamer and 1g of dispersant, and then use a high-speed homogenizer to uniformly disperse at a rate of 3kr / min for 10min.

[0135] Step 5: Prepare microwave absorbing paste.

[0136] Subsequently, 70g of each of the three LNT@Co2Z@CIP composite powders with different mass ratios were slowly poured into the above resin slurry, and then uniformly dispersed for 1 hour at a rate of 3kr / min using a high-speed homogenizer to obtain three different microwave absorbing slurries.

[0137] Step Six: Apply the coating.

[0138] The dispersed microwave absorbing slurry is poured into the feed chamber of the spray gun in small amounts multiple times. With the assistance of an air compressor, the appropriate airflow and feed amount are adjusted. The composite slurry is sprayed intermittently multiple times in a water curtain cabinet using an air spraying method to prepare a coating with uniform thickness on a regular flat plate. The time interval between each spraying is 8 minutes.

[0139] Step 7: Rolling operation.

[0140] When the coating is semi-cured, it needs to be peeled off the plate and rolled to reduce defects such as internal pores and cracks. By gradually reducing the thickness and rolling in different directions multiple times, the smoothness and density of the patch are improved, and the thickness of the absorbing patch is strictly controlled.

[0141] Step 8: Curing and shaping.

[0142] After rolling, the material is placed at room temperature and allowed to fully cure to obtain a lightweight LNT@Co2Z@CIP epoxy resin-based microwave absorbing patch.

[0143] like Figure 9 As shown, the reflectivity of the absorbing patch prepared in this embodiment was tested and calculated, and the results were analyzed and compared. Figure 9Figure (a) shows that the LNT@Co2Z@CIP patch prepared in this embodiment, with a composite absorber mass ratio of LNT:Co2Z:CIP = 2:1:1, and a thickness of 1.3 mm, can achieve a Ku-band reflectivity of less than -8 dB, a minimum reflection loss of -29.3 dB (15.3 GHz), and an effective absorption bandwidth of 5.1 GHz (12.4–17.5 GHz). Through observation and comparison… Figure 9 Figure (b) shows that the absorbing patch has a wide effective absorption bandwidth and good absorption effect. By comparing the measured reflection loss with the simulated reflection loss, it can be found that the measured results are basically consistent with the simulation results.

[0144] Table 4 shows the density, absorption bandwidth, and absorption peak data of LNT, Co2Z, and CIP patch materials with mass ratios of 1:1:1, 2:1:1, and 1:1:2, respectively, at various thicknesses. At a thickness of 1.4 mm, they can achieve effective absorption bandwidths of 5.2 GHz, 5.9 GHz, and 5 GHz within the 2–18 GHz range, respectively, with the strongest absorption peaks at -22.5 dB, -21.5 dB, and -34.4 dB, respectively, and their densities all not exceeding 1.9 g / cm³. 3 It is a dual-band broadband absorbing material with great potential.

[0145] Table 4

[0146]

[0147] This invention provides a design and preparation method for a lightweight epoxy resin-based microwave absorbing material composed of microwave dielectric materials and / or microwave magnetic dielectric materials combined with magnetic metal micropowders. Adding appropriate amounts of microwave dielectric and microwave magnetic dielectric ceramic powders to the magnetic metal micropowders can effectively adjust electromagnetic parameters to achieve impedance matching and good attenuation characteristics, thereby obtaining excellent microwave absorption performance. Furthermore, the relatively lightweight dielectric and magnetic ceramic powders have a much lower density than the metal powders, thus significantly reducing the bulk density and areal density of the absorbing slurry. This invention also features a simple preparation process, good plasticity and toughness, light weight, and excellent electromagnetic and microwave absorption properties.

[0148] This invention primarily achieves effective impedance matching by adjusting the ratio of microwave dielectric material, microwave magnetic dielectric material, and magnetic metal powder in the composite absorber, thereby regulating the high-frequency resistance and reactance characteristics of the patch over a wide range. Specifically, it optimizes the ratio of different types of absorbers through two-phase and three-phase composites of microwave dielectric material, microwave magnetic dielectric material, and magnetic metal powder. By coupling multiple loss mechanisms of electric dipoles, magnetic dipoles, and hysteresis currents in the microwave electromagnetic field, impedance matching characteristics are optimized in specific frequency bands, improving the microwave absorption performance of the composite coating and broadening the absorption bandwidth. This provides a foundation for subsequent research and development of microwave absorbing coatings.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A microwave absorber, characterized in that, Including magnetic metal micropowders and microwave dielectric materials; The mass ratio of microwave dielectric material to magnetic metal powder is 1~7:1~3; The magnetic metal powder is carbonyl iron powder or FeSiAl powder; The microwave dielectric material is LiNb 0.8 Ti 0.25 O3 ceramic powder.

2. A microwave absorber, characterized in that, Including magnetic metal micropowders and microwave magnetic media materials; The mass ratio of microwave magnetic dielectric material to magnetic metal powder is 1~4:1; The magnetic metal powder is carbonyl iron powder or FeSiAl powder; The microwave magnetic dielectric material is ferrite material Ba3Co2Fe. 24 O 41 Ceramic powder.

3. A microwave absorber, characterized in that, This includes magnetic metal micropowders, microwave dielectric materials, and microwave magnetic dielectric materials; The mass ratio of microwave dielectric material, microwave magnetic dielectric material and magnetic metal powder is (1~3):1:(1~3). The magnetic metal powder is carbonyl iron powder or FeSiAl powder; The microwave dielectric material is LiNb 0.8 Ti 0.25 O3 ceramic powder; The microwave magnetic dielectric material is ferrite material Ba3Co2Fe. 24 O 41 Ceramic powder.

4. A method for preparing the microwave absorber according to any one of claims 1 to 3, characterized in that, After mixing the raw materials according to the designed ratio, they are ball-milled, dried, ground, and sieved to obtain a composite powder, which is then the microwave absorber.

5. A microwave absorbing slurry, characterized in that, It includes binders, curing agents, toughening agents, defoamers, dispersants, and solvents, as well as the microwave absorber according to any one of claims 1 to 3; The binder, curing agent, toughening agent, defoamer, dispersant and microwave absorber are solidified products. Based on the mass of the solidified products as 100%, the total amount of binder, curing agent, toughening agent, defoamer and dispersant accounts for 15% to 35%, and the microwave absorber accounts for 65% to 85%.

6. The method for preparing the microwave absorbing paste according to claim 5, characterized in that, The binder, curing agent, toughening agent, defoamer and dispersant are dissolved in a solvent and mixed, and then homogenized and dispersed to obtain a resin slurry; Microwave absorber is added to resin slurry and homogenized to obtain microwave absorbing slurry.

7. A method for preparing a microwave absorbing patch based on the microwave absorbing paste according to claim 5, characterized in that, Includes the following steps: Cut out release paper of regular size and paste it onto the metal substrate, then place it horizontally in the central area of ​​the water curtain cabinet; The microwave absorbing paste is poured into the feed chamber of the spray gun in small amounts multiple times. The airflow and feed amount are adjusted. The microwave absorbing paste is sprayed multiple times intermittently using the air spraying method, with an interval of 3 to 8 minutes between each spraying, to spray a uniform coating on the substrate. After curing at room temperature, a semi-cured coating material is obtained, which is then peeled off flat from the release paper as a precursor for the microwave absorbing patch. In the semi-cured state, the precursor of the microwave absorbing patch is rolled multiple times. The thickness of each roll is adjusted according to the actual thickness of the patch, and the rolling direction is continuously adjusted until the target thickness is reached. After rolling, the metal plate is statically pressed and cured at room temperature to obtain the final microwave absorbing patch.

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