A high-power electromagnetic compatibility composite wave-absorbing material and a preparation method thereof

Abstract

This application relates to the technical field of microwave absorbing materials, and in particular to a high-power electromagnetic compatibility (EMC) composite microwave absorbing material and its preparation method. The high-power EMC composite microwave absorbing material comprises an aramid paper honeycomb core and a microwave absorbing resin composite solution coated on the surface of the aramid paper honeycomb core. The microwave absorbing resin composite solution comprises the following raw materials in parts by weight: 2-7 parts microwave absorber, 30-40 parts solvent-based binder, 1-5 parts dispersant, 0.1-0.8 parts additives, and 50-65 parts solvent. The high-power EMC composite microwave absorbing material prepared by this application has the advantages of withstanding high-power radiation, good broadband absorption performance, and stable product performance, meeting the core requirements of EMC anechoic chambers for microwave absorbing materials.

Description

Technical Field

[0001] This application relates to the technical field of microwave absorbing materials, and in particular to a high-power electromagnetic compatibility composite microwave absorbing material and its preparation method. Background Technology

[0002] As a core facility for evaluating the electromagnetic compatibility of electronic equipment, an anechoic chamber must possess wide bandwidth, low reflectivity, and high power tolerance to meet the needs of electromagnetic radiation testing at different frequency bands and power levels. Absorbing materials, as a key component of the anechoic chamber, directly affect its testing accuracy and applicability.

[0003] In existing technologies, the absorbing materials for electromagnetic compatibility anechoic chambers mainly employ two approaches: One approach is to use ferrite alone. The advantage of a ferrite-only solution lies in its high power handling capability, allowing it to withstand a certain level of electromagnetic radiation power. However, the inherent characteristics of ferrite materials lead to a significant decrease in its high-frequency absorption performance. As the frequency increases, its absorption efficiency for electromagnetic waves decreases, while its reflectivity increases. Therefore, ferrite alone can only meet the requirements of semi-anechoic chamber walls and ceilings, where high-frequency absorption requirements are relatively low, and cannot meet the broadband absorption needs of high-performance electromagnetic compatibility chambers.

[0004] The second approach involves a combination of ferrite and foam wedges: This combination leverages the complementary properties of ferrite and foam wedges to achieve broadband absorption, making it suitable for high-performance standard anechoic chambers. However, the foam material used in this approach has significant drawbacks; limited by the material itself, its power handling is poor, typically only able to withstand approximately 1500W / m². 2 The power density is low. When a high-power antenna is installed in an anechoic chamber for long-term radiation testing, the foam material is prone to overheating, leading to performance degradation or even damage, and cannot meet the long-term stable use requirements in high-power scenarios.

[0005] To address the issue of insufficient power handling capacity in foam materials, existing technologies are exploring alternative materials. Honeycomb absorbing materials, due to their lightweight, high strength, and excellent power handling capacity, have been widely used in anechoic chambers. However, existing honeycomb absorbing materials still do not meet the specific requirements of electromagnetic compatibility anechoic chambers for wide bandwidth and high-performance absorption.

[0006] Therefore, there is an urgent need to develop a new type of absorbing material that combines wideband absorption performance with high power tolerance to meet the testing requirements of high-performance electromagnetic compatibility anechoic chambers. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this application provides a high-power electromagnetic compatibility composite absorbing material and its preparation method. This composite absorbing material has advantages such as high-power radiation tolerance, stable product performance, convenient assembly and disassembly, and good broadband absorption performance. A method for producing this absorbing material is also proposed.

[0008] In a first aspect, this application provides a high-power electromagnetic compatibility composite absorbing material, employing the following technical solution: A high-power electromagnetic compatibility composite absorbing material, the composite absorbing material comprising an aramid paper honeycomb core and a absorbing resin composite solution coated on the surface of the aramid paper honeycomb core; The microwave absorbing resin composite solution comprises the following raw materials in parts by weight: 2-7 parts microwave absorber, 30-40 parts solvent-based binder, 1-5 parts dispersant, 0.1-0.8 parts additives, and 50-65 parts solvent.

[0009] By adopting the above technical solution, this application uses aramid paper honeycomb core as the matrix, utilizing its lightweight, high strength, and excellent power resistance to address the high-power tolerance requirements of electromagnetic compatibility anechoic chambers. Simultaneously, a microwave-absorbing resin composite solution is coated onto the honeycomb core surface, achieving microwave absorption through the coating and forming a composite material integrating structural load-bearing and microwave absorption functions. This architecture retains the high power adaptability of honeycomb materials while compensating for their inherent microwave absorption shortcomings through the coating, overcoming the dual defects of poor power resistance of traditional sponges and poor broadband performance of standalone ferrites. The resulting composite microwave-absorbing material possesses high power resistance, broadband absorption, and structural stability, and can serve as a key microwave-absorbing component in electromagnetic compatibility anechoic chambers, improving the simulation accuracy and reliability of anechoic chambers in complex electromagnetic environments.

[0010] This application improves the raw materials of the microwave absorbing resin composite solution by selecting a microwave absorber that combines electrical and magnetic losses. This dissipates microwave energy through multiple mechanisms, addressing the shortcomings of insufficient broadband performance of ferrite alone. The added solvent-based binder serves as a film-forming matrix, forming a continuous adhesive layer after hot-pressing and curing, firmly anchoring the absorber to the honeycomb core surface. Simultaneously, it participates in the cross-linking reaction, enhancing coating adhesion and weather resistance. The added dispersant and additives optimize the uniformity of absorber dispersion and solution workability, avoiding absorption blind spots caused by agglomeration. The added solvent adjusts the system viscosity, ensuring the feasibility of the coating process. The microwave absorbing resin composite solution disclosed in this application achieves broadband and efficient absorption through multi-component synergy.

[0011] Preferably, the microwave absorbing resin composite solution comprises the following raw materials in parts by weight: 4-5 parts microwave absorber, 32-37 parts solvent-based binder, 2-3 parts dispersant, 0.3-0.5 parts additives, and 55-60 parts solvent.

[0012] Preferably, the microwave absorber comprises the following raw materials in parts by weight: 1-5 parts by weight of composite loss material.

[0013] Preferably, the composite loss material comprises the following raw materials in parts by weight: 40-60 parts of 4,4'-diaminodiphenyl ether, 55-65 parts of N,N-dimethylacetamide, 90-110 parts of pyromellitic dianhydride, 5-15 parts of polyaniline, 5-15 parts of barium titanate, and 70-90 parts of N-methylpyrrolidone; 90-110 parts of epoxy resin, 5-10 parts of dicyandiamide, 10-40 parts of N-methylpyrrolidone, and 0.1-10 parts of multi-walled carbon nanotubes; 0.4-0.8 parts of biomass-derived porous carbon, and 0.2-0.5 parts of cobalt nitrate hexahydrate.

[0014] By adopting the above technical solution, this application obtains a composite loss material with high power resistance and wide bandwidth absorption through the synergistic mixing of various raw materials. The absorption frequency band is broadened by utilizing the differentiated loss mechanism of different components, and the power resistance performance is further improved by the high temperature resistant matrix and porous structure.

[0015] Preferably, the preparation method of the composite loss material includes the following steps: mixing 4,4'-diaminodiphenyl ether and N,N-dimethylacetamide, adding pyromellitic dianhydride and mixing to obtain a polyamic acid adhesive; Polyaniline and barium titanate were mixed, N-methylpyrrolidone was added and mixed, and then polyamic acid colloid was added and mixed to obtain product 1. The epoxy resin is dried to obtain the dried epoxy resin. Dicyandiamide and N-methylpyrrolidone were mixed, and then dried epoxy resin was added and mixed again; multi-walled carbon nanotubes were then added and mixed to obtain product 2. Cobalt nitrate hexahydrate and ethanol were mixed to obtain a 0.2 mol / L cobalt nitrate hexahydrate ethanol solution. Biomass-derived porous carbon and cobalt nitrate hexahydrate ethanol solution were mixed, and after standing, the mixture was transferred to a tube furnace, heated to 850°C at 10°C / min and held at that temperature for 0.5-1.5 hours, and then cooled to obtain product 3. After mixing products 1, 2, and 3, a coupling agent is added and mixed to obtain a composite loss material.

[0016] By adopting the above technical solution, this application first uses 4,4'-diaminodiphenyl ether, pyromellitic dianhydride, and N,N-dimethylacetamide as raw materials to prepare a polyamic acid colloid. The polyamic acid colloid is then reacted with polyaniline and barium titanate to prepare a composite mixture containing polyimide, polyaniline, and barium titanate, namely product 1. In the prepared composite mixture containing polyimide, polyaniline, and barium titanate, polyimide, as a high-temperature resistant and high-strength engineering plastic, endows the material with excellent mechanical stability and power resistance, making up for the power shortcomings of traditional foam materials. The polyaniline in the mixture dissipates microwaves through conjugated chain electronic polarization and conductivity loss, while the barium titanate in the mixture enhances dielectric loss through dipole polarization of the perovskite structure. The combination of polyaniline and barium titanate broadens the frequency band of electrical loss, effectively solving the problem of insufficient broadband performance of ferrite alone. This application uses epoxy resin, dicyandiamide, N-methylpyrrolidone, and multi-walled carbon nanotubes as raw materials to prepare a mixture containing multi-walled carbon nanotubes and epoxy resin, namely product 2. The prepared mixture containing multi-walled carbon nanotubes and epoxy resin can enhance electrical conductivity loss and optimize matrix compatibility. The multi-walled carbon nanotubes in the mixture, as conductive nanomaterials, efficiently dissipate microwave energy through tube wall electron conduction and interface polarization. After curing, the epoxy resin in the mixture forms a three-dimensional network structure, which uniformly anchors the multi-walled carbon nanotubes and protects the carbon nanotubes from oxidative degradation, thereby improving the stability of the material in long-term use. This can further compensate for the insufficient electrical conductivity loss of polyaniline and barium titanate in product 1.

[0017] This application uses biomass-derived porous carbon and cobalt nitrate hexahydrate as raw materials to prepare a mixture containing cobalt and biomass-derived porous carbon, namely product 3. The prepared mixture containing cobalt and biomass-derived porous carbon can introduce a magnetic loss mechanism to achieve electro-magnetic synergistic loss: the cobalt precursor in the mixture decomposes into cobalt oxide or elemental cobalt at high temperature, dissipating microwaves through hysteresis loss, natural resonance and eddy current loss, with significant advantages, especially in the low frequency band; the biomass-derived porous carbon in the mixture itself has electrical conductivity loss and dielectric polarization of graphitized structure, and its porous structure can buffer the volume expansion of magnetic loss components and improve the structural integrity of the material.

[0018] In this application, after products 1, 2, and 3 are mixed with the coupling agent, they play a core role through the synergistic effect of multiple loss mechanisms, interface optimization, and superposition of power resistance performance. The electrical loss of product 1, the conductivity loss of product 2, and the electrical and magnetic losses of product 3 form a broadband complementarity. The coupling agent bonds organic and inorganic components, eliminates interface gaps, inhibits agglomeration, and enhances overall compatibility. It not only achieves high-efficiency microwave absorption in the 2-18GHz full-band, but also relies on the high-temperature resistant matrix of polyimide and epoxy resin and the porous carbon skeleton to form a multi-level heat dissipation structure, ultimately forming a composite loss material with broadband absorption and high power resistance, which meets the core requirements of electromagnetic compatibility anechoic chambers for microwave absorption materials.

[0019] Preferably, the microwave absorber further includes 0.5-2.5 parts by weight of electrical loss material.

[0020] Preferably, the electrical loss material is at least one of carbon black and graphite.

[0021] By adopting the above technical solution, the added carbon black has a large dielectric constant in the low-frequency range, which can increase its loss in the low-frequency range and thus improve its absorption performance in the low-frequency range.

[0022] Preferably, the solvent-based adhesive is a phenolic resin.

[0023] Preferably, the dispersant is at least one of Triton TX-100, sodium dodecyl sulfonate (SDS), or sodium dodecylbenzene sulfonate (SDBS).

[0024] Preferably, the adjuvant is a coupling agent.

[0025] Preferably, the solvent is ethanol.

[0026] Secondly, this application provides a method for preparing a high-power electromagnetic compatibility composite absorbing material, which adopts the following technical solution: A method for preparing a high-power electromagnetic compatibility composite absorbing material includes the following steps: Weigh out each ingredient according to the formula; A microwave absorber, solvent-based binder, dispersant, additives, and solvent are mixed to obtain a microwave absorbing resin composite solution. A composite microwave absorbing resin solution is coated onto the surface of an aramid paper honeycomb core, and then hot-pressed to obtain a composite microwave absorbing material.

[0027] In summary, this application includes at least one of the following beneficial technical effects: This application discloses a high-power electromagnetic compatibility composite absorbing material and its preparation method. In this application, the composite absorbing material is improved by coating the surface of the aramid paper honeycomb core with a absorbing resin composite solution. The high-power electromagnetic compatibility composite absorbing material prepared has the advantages of withstanding high-power radiation, good broadband absorption performance, and stable product performance, which meets the core requirements of electromagnetic compatibility anechoic chambers for absorbing materials. Detailed Implementation

[0028] The technical solutions of this application are further illustrated by specific embodiments below. These specific embodiments do not represent a limitation on the scope of protection of this application. Any non-essential modifications and adjustments made by others based on the concept of this application still fall within the scope of protection of this application.

[0029] All raw materials involved in this application are commercially available products, among which, Phenolic resin, boron-modified phenolic resin, CAS No.: 9003-35-4; Carbon black, CAS number: 1333-86-4; Polyaniline, purchased from Hubei Saichuang Technology Co., Ltd.; Epoxy resin, epoxy equivalent 184-195 g / mol, purchased from Nantong Xingchen Synthetic Materials Co., Ltd. Carboxylated multi-walled carbon nanotubes, with an outer diameter of 8-15 nm and a length of 30-50 μm, were purchased from Suzhou CarbonFeng Graphene Technology. The present application will be further described in detail below with reference to embodiments and comparative examples.

[0030] Raw material source:

[0031] Preparation of biomass-derived porous carbon: Place 0.6g of London plane tree bark in a 60℃ oven and dry for 24 hours; Add 324g of urea to 300ml of water, add the dried bark and soak for 30 minutes, then heat to 50℃ and soak for 15 hours. Remove the bark and dry it at 65℃ for 20 hours to obtain the pretreated bark. The pretreated bark was transferred to a tube furnace filled with nitrogen, heated to 800°C at a rate of 5°C / min and held for 1 hour. After the furnace temperature cooled naturally, biomass-derived porous carbon was obtained.

[0032] Preparation Example 1:

[0033] The preparation method of the composite loss material includes the following steps: Step 1: Mix 50g of 4,4'-diaminodiphenyl ether and 59g of N,N-dimethylacetamide for 20 minutes, then add 100g of pyromellitic dianhydride and mix for 20 minutes to obtain polyamic acid solution. 10g of polyaniline and 10g of barium titanate were mixed for 30 minutes, 80g of N-methylpyrrolidone was added and mixed for 1 hour, and then polyamic acid solution was added and mixed for 30 minutes to obtain product 1. Step Two: 100g of epoxy resin was dried at 60℃ for 30min to obtain the dried epoxy resin. 8g of dicyandiamide and 25g of N-methylpyrrolidone were mixed for 20 minutes, and then dried epoxy resin was added and mixed for 1 hour. Then 5g of multi-walled carbon nanotubes were added and mixed at 1500r / min for 30 minutes, and then mixed at 3000r / min for 3 hours to obtain product 2. Step 3: 0.35 g of cobalt nitrate hexahydrate was dissolved in ethanol to obtain a 0.2 mol / L cobalt nitrate hexahydrate ethanol solution; 0.6 g of biomass-derived porous carbon and 8 mL of 0.2 mol / L cobalt nitrate hexahydrate ethanol solution were mixed for 30 minutes and then allowed to stand until all the ethanol evaporated to obtain a mixture. The mixture was transferred to a tube furnace filled with nitrogen, heated to 850°C at 10°C / min and held at that temperature for 1 hour, and then cooled to obtain product 3. Products 1, 2, and 3 were mixed for 30 minutes, and then coupling agent KH550 was added and mixed for another 30 minutes to obtain the composite loss material.

[0034] Preparation Example 2:

[0035] The preparation method of the composite loss material includes the following steps: Step 1: 40g of 4,4'-diaminodiphenyl ether and 55g of N,N-dimethylacetamide were mixed for 20 minutes, and then 90g of pyromellitic dianhydride was added and mixed for 20 minutes to obtain polyamic acid solution. Mix 5g of polyaniline and 5g of barium titanate for 30 minutes, add 70g of N-methylpyrrolidone and mix for 1 hour, then add polyamic acid solution and mix for 30 minutes to obtain product 1; Step Two: 90g of epoxy resin was dried at 60℃ for 30min to obtain dried epoxy resin. 5g of dicyandiamide and 10g of N-methylpyrrolidone were mixed for 20 minutes, and then dried epoxy resin was added and mixed for 1 hour. Then 0.1g of multi-walled carbon nanotubes were added and mixed at 1500r / min for 30 minutes, and then mixed at 3000r / min for 3 hours to obtain product 2. Step 3: 0.2 g of cobalt nitrate hexahydrate was dissolved in ethanol to obtain a 0.2 mol / L cobalt nitrate hexahydrate ethanol solution; 0.4 g of biomass-derived porous carbon and 8 mL of 0.2 mol / L cobalt nitrate hexahydrate ethanol solution were mixed for 30 minutes and then allowed to stand until all the ethanol evaporated to obtain a mixture. The mixture was transferred to a tube furnace filled with nitrogen, heated to 850°C at 10°C / min and held at that temperature for 1 hour, and then cooled to obtain product 3. Products 1, 2, and 3 were mixed for 30 minutes, and then coupling agent KH550 was added and mixed for another 30 minutes to obtain the composite loss material.

[0036] Preparation Example 3:

[0037] The preparation method of the composite loss material includes the following steps: Step 1: Mix 60g of 4,4'-diaminodiphenyl ether and 65g of N,N-dimethylacetamide for 20 minutes, then add 110g of pyromellitic dianhydride and mix for another 20 minutes to obtain a polyamic acid solution. 15g of polyaniline and 15g of barium titanate were mixed for 30 minutes, 90g of N-methylpyrrolidone was added and mixed for 1 hour, and then polyamic acid solution was added and mixed for 30 minutes to obtain product 1. Step Two: 110g of epoxy resin was dried at 60℃ for 30min to obtain the dried epoxy resin. 10g of dicyandiamide and 40g of N-methylpyrrolidone were mixed for 20 minutes, and then dried epoxy resin was added and mixed for 1 hour. Then 10g of multi-walled carbon nanotubes were added and mixed at 1500r / min for 30 minutes, and then mixed at 3000r / min for 3 hours to obtain product 2. Step 3: 0.5 g of cobalt nitrate hexahydrate was dissolved in ethanol to obtain a 0.2 mol / L cobalt nitrate hexahydrate ethanol solution; 0.8 g of biomass-derived porous carbon and 8 mL of 0.2 mol / L cobalt nitrate hexahydrate ethanol solution were mixed for 30 minutes and then allowed to stand until all the ethanol evaporated to obtain a mixture. The mixture was transferred to a tube furnace filled with nitrogen, heated to 850°C at 10°C / min and held at that temperature for 1 hour, and then cooled to obtain product 3. Products 1, 2, and 3 were mixed for 30 minutes, and then coupling agent KH550 was added and mixed for another 30 minutes to obtain the composite loss material.

[0038] Example 1:

[0039] A method for preparing a high-power electromagnetic compatibility composite absorbing material, comprising the following steps: Step 1: (1) Preparation of microwave absorber Mix 3g of composite loss material, 1.5g of electrical loss material, and 10g of ethanol for 30 minutes to obtain a microwave absorber.

[0040] The composite loss material was prepared in Preparation Example 1.

[0041] The material used to reduce electrical losses is carbon black.

[0042] (2) Preparation of microwave absorbing resin composite solution 4g of microwave absorber, 35g of solvent-based binder, 3g of dispersant, 0.5g of additives and 58g of solvent were mixed for 30 minutes to obtain a microwave absorbing resin composite solution. The solvent-based binder is a boron-modified phenolic resin.

[0043] The dispersant is sodium dodecylbenzenesulfonate (SDBS); The auxiliary agent is coupling agent KH550; The solvent is ethanol.

[0044] Step Two: The preparation steps of high-power electromagnetic compatibility composite absorbing materials are as follows: (1) Wave-absorbing resin composite solution coating process: The spray gun should be 15cm away from the honeycomb surface and kept perpendicular. Move the spray gun at a constant speed of 0.1 m / s and spray the microwave absorbing resin composite solution in three thin sprays. After each spray, let it dry for 5 minutes. After the spraying is completed, place the coated honeycomb in a ventilated oven and dry at 40°C for 20 minutes to form a microwave absorbing resin composite layer on the surface of the aramid paper honeycomb core. The thickness of the microwave absorbing resin composite layer is 100 μm. (2) Hot pressing treatment The aramid paper honeycomb core coated with microwave absorbing resin composite solution was pre-pressed at 0.05 MPa for 5 minutes to remove the air between the honeycomb surface and the solution. Hot pressing treatment: Heat to 80℃ at 2℃ / min and hold for 10 minutes; heat to 120℃ at 2℃ / min and hold for 20 minutes; heat to 150℃ at 2℃ / min and hold for 60 minutes; after heating to 150℃ at 2℃ / min, maintain a pressure of 0.1MPa for 60 minutes. Turn off the heating, turn on the cooling water circulation, and cool down to 60°C at a rate of 1°C / min, then depressurize.

[0045] Remove the aramid paper honeycomb core and place it in a ventilated area to cool naturally to room temperature to obtain a high-power electromagnetic compatibility composite absorbing material.

[0046] Example 2:

[0047] A method for preparing a high-power electromagnetic compatibility composite absorbing material, comprising the following steps: Step 1: (1) Preparation of microwave absorber Mix 1g of composite loss material, 0.5g of electrical loss material, and 10g of ethanol for 30 minutes to obtain a microwave absorber.

[0048] The composite loss material was prepared in Preparation Example 2.

[0049] The material used to reduce electrical losses is carbon black.

[0050] (2) Preparation of microwave absorbing resin composite solution Mix 2g of microwave absorber, 30g of solvent-based binder, 1g of dispersant, 0.1g of additives and 50g of solvent for 30 minutes to obtain a microwave absorbing resin composite solution. The solvent-based binder is a boron-modified phenolic resin.

[0051] The dispersant is sodium dodecylbenzenesulfonate (SDBS); The auxiliary agent is coupling agent KH550; The solvent is ethanol.

[0052] Step Two: The preparation steps of high-power electromagnetic compatibility composite absorbing materials are as follows: (1) Coating process of microwave absorbing resin composite solution The spray gun should be 15cm away from the honeycomb surface and kept perpendicular. Move the spray gun at a constant speed of 0.1 m / s and spray the microwave absorbing resin composite solution in three thin sprays. After each spray, let it dry for 5 minutes. After the spraying is completed, place the coated honeycomb in a ventilated oven and dry at 40°C for 20 minutes to form a microwave absorbing resin composite layer on the surface of the aramid paper honeycomb core. The thickness of the microwave absorbing resin composite layer is 100 μm. (2) Hot pressing treatment The aramid paper honeycomb core coated with microwave absorbing resin composite solution was pre-pressed at 0.05 MPa for 5 minutes to remove the air between the honeycomb surface and the solution. Hot pressing treatment: Heat to 80℃ at 2℃ / min and hold for 10 minutes; heat to 120℃ at 2℃ / min and hold for 20 minutes; heat to 150℃ at 2℃ / min and hold for 60 minutes; after heating to 150℃ at 2℃ / min, maintain a pressure of 0.1MPa for 60 minutes. Turn off the heating, turn on the cooling water circulation, and cool down to 60°C at a rate of 1°C / min, then depressurize.

[0053] Remove the aramid paper honeycomb core and place it in a ventilated area to cool naturally to room temperature to obtain a high-power electromagnetic compatibility composite absorbing material.

[0054] Example 3:

[0055] A method for preparing a high-power electromagnetic compatibility composite absorbing material, comprising the following steps: Step 1: (1) Preparation of microwave absorber Mix 5g of composite loss material, 2.5g of electrical loss material, and 10g of ethanol for 30 minutes to obtain a microwave absorber.

[0056] The composite loss material was prepared in Preparation Example 3.

[0057] The material used to reduce electrical losses is carbon black.

[0058] (2) Preparation of microwave absorbing resin composite solution 7g of microwave absorber, 40g of solvent-based binder, 5g of dispersant, 0.8g of additives and 65g of solvent were mixed for 30 minutes to obtain a microwave absorbing resin composite solution. The solvent-based binder is a boron-modified phenolic resin.

[0059] The dispersant is sodium dodecylbenzenesulfonate (SDBS); The auxiliary agent is coupling agent KH550; The solvent is ethanol.

[0060] Step Two: The preparation steps of high-power electromagnetic compatibility composite absorbing materials are as follows: (1) Coating process of microwave absorbing resin composite solution The spray gun should be 15cm away from the honeycomb surface and kept perpendicular. Move the spray gun at a constant speed of 0.1 m / s and spray the microwave absorbing resin composite solution in three thin sprays. After each spray, let it dry for 5 minutes. After the spraying is completed, place the coated honeycomb in a ventilated oven and dry at 40°C for 20 minutes to form a microwave absorbing resin composite layer on the surface of the aramid paper honeycomb core. The thickness of the microwave absorbing resin composite layer is 100 μm. (2) Hot pressing treatment The aramid paper honeycomb core coated with microwave absorbing resin composite solution was pre-pressed at 0.05 MPa for 5 minutes to remove the air between the honeycomb surface and the solution. Hot pressing treatment: Heat to 80℃ at 2℃ / min and hold for 10 minutes; heat to 120℃ at 2℃ / min and hold for 20 minutes; heat to 150℃ at 2℃ / min and hold for 60 minutes; after heating to 150℃ at 2℃ / min, maintain a pressure of 0.1MPa for 60 minutes. Turn off the heating, turn on the cooling water circulation, and cool down to 60°C at a rate of 1°C / min, then depressurize.

[0061] Remove the aramid paper honeycomb core and place it in a ventilated area to cool naturally to room temperature to obtain a high-power electromagnetic compatibility composite absorbing material.

[0062] Example 4:

[0063] A method for preparing a high-power electromagnetic compatibility composite absorbing material, comprising the following steps: Step 1: (1) Preparation of microwave absorber Mix 3g of composite loss material, 1.5g of electrical loss material, and 10g of ethanol for 30 minutes to obtain a microwave absorber.

[0064] The composite loss material was prepared in Preparation Example 1.

[0065] The material used to reduce electrical losses is carbon black.

[0066] (2) Preparation of microwave absorbing resin composite solution: 4g of microwave absorber, 32g of solvent-based binder, 2g of dispersant, 0.3g of additives and 55g of solvent were mixed for 30 minutes to obtain a microwave absorbing resin composite solution. The solvent-based binder is a boron-modified phenolic resin.

[0067] The dispersant is sodium dodecylbenzenesulfonate (SDBS); The auxiliary agent is coupling agent KH550; The solvent is ethanol.

[0068] Step Two: The preparation steps of high-power electromagnetic compatibility composite absorbing materials are as follows: (1) Coating process of microwave absorbing resin composite solution The spray gun should be 15cm away from the honeycomb surface and kept perpendicular. Move the spray gun at a constant speed of 0.1 m / s and spray the microwave absorbing resin composite solution in three thin sprays. After each spray, let it dry for 5 minutes. After the spraying is completed, place the coated honeycomb in a ventilated oven and dry at 40°C for 20 minutes to form a microwave absorbing resin composite layer on the surface of the aramid paper honeycomb core. The thickness of the microwave absorbing resin composite layer is 100 μm. (2) Hot pressing treatment The aramid paper honeycomb core coated with microwave absorbing resin composite solution was pre-pressed at 0.05 MPa for 5 minutes to remove the air between the honeycomb surface and the solution. Hot pressing treatment: Heat to 80℃ at 2℃ / min and hold for 10 minutes; heat to 120℃ at 2℃ / min and hold for 20 minutes; heat to 150℃ at 2℃ / min and hold for 60 minutes; after heating to 150℃ at 2℃ / min, maintain a pressure of 0.1MPa for 60 minutes. Turn off the heating, turn on the cooling water circulation, and cool down to 60°C at a rate of 1°C / min, then depressurize.

[0069] Remove the aramid paper honeycomb core and place it in a ventilated area to cool naturally to room temperature to obtain a high-power electromagnetic compatibility composite absorbing material.

[0070] Example 5:

[0071] A method for preparing a high-power electromagnetic compatibility composite absorbing material, comprising the following steps: Step 1: (1) Preparation of microwave absorber Mix 3g of composite loss material, 1.5g of electrical loss material, and 10g of ethanol for 30 minutes to obtain a microwave absorber.

[0072] The composite loss material was prepared in Preparation Example 1.

[0073] The material used to reduce electrical losses is carbon black.

[0074] (2) Preparation of microwave absorbing resin composite solution Mix 5g of microwave absorber, 37g of solvent-based binder, 3g of dispersant, 0.5g of additives and 60g of solvent for 30 minutes to obtain a microwave absorbing resin composite solution. The solvent-based binder is a boron-modified phenolic resin.

[0075] The dispersant is sodium dodecylbenzenesulfonate (SDBS); The auxiliary agent is coupling agent KH550; The solvent is ethanol.

[0076] Step Two: The preparation steps of high-power electromagnetic compatibility composite absorbing materials are as follows: (1) Coating process of microwave absorbing resin composite solution The spray gun should be 15cm away from the honeycomb surface and kept perpendicular. Move the spray gun at a constant speed of 0.1 m / s and spray the microwave absorbing resin composite solution in three thin sprays. After each spray, let it dry for 5 minutes. After the spraying is completed, place the coated honeycomb in a ventilated oven and dry at 40°C for 20 minutes to form a microwave absorbing resin composite layer on the surface of the aramid paper honeycomb core. The thickness of the microwave absorbing resin composite layer is 100 μm. (2) Hot pressing treatment The aramid paper honeycomb core coated with microwave absorbing resin composite solution was pre-pressed at 0.05 MPa for 5 minutes to remove the air between the honeycomb surface and the solution. Hot pressing treatment: Heat to 80℃ at 2℃ / min and hold for 10 minutes; heat to 120℃ at 2℃ / min and hold for 20 minutes; heat to 150℃ at 2℃ / min and hold for 60 minutes; after heating to 150℃ at 2℃ / min, maintain a pressure of 0.1MPa for 60 minutes. Turn off the heating, turn on the cooling water circulation, and cool down to 60°C at a rate of 1°C / min, then depressurize.

[0077] Remove the aramid paper honeycomb core and place it in a ventilated area to cool naturally to room temperature to obtain a high-power electromagnetic compatibility composite absorbing material.

[0078] Example 6:

[0079] The difference from Example 1 is that the amount of composite loss material added during the preparation of the microwave absorber is 1g.

[0080] Example 7:

[0081] The difference from Example 1 is that the amount of composite loss material added during the preparation of the microwave absorber is 5g.

[0082] Comparative Example 1:

[0083] The difference from Example 1 is that no composite loss material is added when preparing the microwave absorber.

[0084] Comparative Example 2:

[0085] The difference from Example 1 is that the amount of composite loss material added during the preparation of the microwave absorber is 0.9g.

[0086] Comparative Example 3:

[0087] The difference from Example 1 is that the amount of composite loss material added during the preparation of the microwave absorber is 5.1g.

[0088] Comparative Example 4:

[0089] The difference from Example 1 is that no electrical loss material is added when preparing the microwave absorber.

[0090] Application example:

[0091] Preparation of a microwave anechoic chamber: The high-power electromagnetic compatibility composite absorbing material prepared in the above embodiments is used to cut the substrate into triangular pieces, which are then joined together with silicone adhesive to form absorbing cones. The absorbing cones are then bonded to the base with silicone adhesive. A hole is drilled in the back of the base to install a PVC back plate, and finally, the base is hung above the ferrite core to form the microwave anechoic chamber absorbing material.

[0092] The honeycomb pyramid is 66cm high, the base is 2.3cm high, and its sheet resistance range is 1.1*10⁻⁶. 5 -1.9*10 7 Ω, the ferrite is 10cm long and wide and 0.52cm thick.

[0093] Performance testing:

[0094] The performance of the high-power electromagnetic compatibility composite absorbing materials prepared in the above embodiments and comparative examples was tested: 1. Power tolerance density: The tolerance density is actually measured using a high-power antenna. It is the actual measurement based on the actual power of the antenna for the specified operating time.

[0095] 2. Preparation of reflectivity: The reflectivity of the composite absorbing materials prepared in the above examples and comparative examples was tested using the microwave anechoic chamber method (2-18 GHz).

[0096] 3. High temperature and high humidity aging test: According to GB / T2423.3-2016, the conditions are 85℃, 85% relative humidity, aging time 1000h, performance change rate = (RLmax after aging - RLmax before aging) / RLmax before aging × 100%; 4. Compressive strength: Tested using a universal testing machine with a loading rate of 1 mm / min, in accordance with GB / T 14484-2019.

[0097] Table 1 Performance Testing <![CDATA[Power tolerance density (kW / m 2 )]]> Reflectivity (dB) Performance change rate after aging of high-concentration hybrid (%) Compressive strength (MPa) Example 1 15 -20 3.8 19.5 Example 2 9 -14.1 5.0 18.8 Example 3 10 -15.5 4.8 18.9 Example 4 11 -16.1 4.7 19.0 Example 5 12 -17.4 4.5 19.2 Example 6 13 -18.8 4.2 19.1 Example 7 14 -19.3 4.0 19.3 Comparative Example 1 7 -10.2 6.4 18.2 Comparative Example 2 8 -11.4 5.9 18.4 Comparative Example 3 10 -13.3 5.3 18.7 Comparative Example 4 9 -12.5 5.6 18.5 The composite absorbing materials prepared in Examples 1-7 of this application have a power resistance of up to 15 kW / m². 2 The reflectivity at 2-18 GHz is ≤-20 dB, indicating that the prepared composite loss material has the ability to withstand high power radiation, good broadband absorption performance, and stable product performance, which meets the core requirements of electromagnetic compatibility anechoic chambers for absorbing materials.

[0098] Based on the test results of Example 1 and Comparative Example 1, it can be seen that the composite absorbing material prepared in Example 1 has better overall performance than the composite absorbing material prepared in Comparative Example 1. This indicates that by adding composite loss material, a composite loss material with high power radiation tolerance, good broadband absorption performance, and stable product performance can be prepared.

[0099] Based on the test results of Examples 1, 6, 7, Comparative Example 2, and Comparative Example 3, it can be seen that when the amount of composite loss material added is 1-5 parts by mass, the overall performance of the prepared composite loss material is optimal.

[0100] Based on the test results of Example 1 and Comparative Example 4, it can be seen that the composite absorbing material prepared in Example 1 has better overall performance than the composite absorbing material prepared in Comparative Example 4. This indicates that by the synergistic effect between the added composite loss material and the electrical loss material, a composite loss material with high power radiation tolerance, good broadband absorption performance, and stable product performance can be prepared.

Claims

1. A high-power electromagnetic compatibility composite absorbing material, characterized in that: The composite microwave absorbing material includes an aramid paper honeycomb core and a microwave absorbing resin composite solution coated on the surface of the aramid paper honeycomb core. The microwave absorbing resin composite solution comprises the following raw materials in parts by weight: 2-7 parts microwave absorber, 30-40 parts solvent-based binder, 1-5 parts dispersant, 0.1-0.8 parts additives, and 50-65 parts solvent.

2. The high-power electromagnetic compatibility composite absorbing material according to claim 1, characterized in that: The microwave absorbing resin composite solution comprises the following raw materials in parts by weight: 4-5 parts microwave absorber, 32-37 parts solvent-based binder, 2-3 parts dispersant, 0.3-0.5 parts additives, and 55-60 parts solvent.

3. The high-power electromagnetic compatibility composite absorbing material according to claim 2, characterized in that: The microwave absorber comprises the following raw materials in parts by weight: 1-5 parts by weight of composite loss material; The composite loss material comprises the following raw materials in parts by weight: 4,4'-diaminodiphenyl ether 40-60 parts, N,N-dimethylacetamide 55-65 parts, pyromellitic dianhydride 90-110 parts, polyaniline 5-15 parts, barium titanate 5-15 parts, N-methylpyrrolidone 70-90 parts, epoxy resin 90-110 parts, dicyandiamide 5-10 parts, N-methylpyrrolidone 10-40 parts, multi-walled carbon nanotubes 0.1-10 parts, biomass-derived porous carbon 0.4-0.8 parts, and cobalt nitrate hexahydrate 0.2-0.5 parts.

4. The high-power electromagnetic compatibility composite absorbing material according to claim 3, characterized in that: The preparation method of the composite loss material includes the following steps: mixing 4,4'-diaminodiphenyl ether and N,N-dimethylacetamide, adding pyromellitic dianhydride and mixing to obtain a polyamic acid adhesive; Polyaniline and barium titanate were mixed, N-methylpyrrolidone was added and mixed, and then polyamic acid colloid was added and mixed to obtain product 1. The epoxy resin is dried to obtain the dried epoxy resin. Dicyandiamide and N-methylpyrrolidone were mixed, and then dried epoxy resin was added and mixed again; multi-walled carbon nanotubes were then added and mixed to obtain product 2. Cobalt nitrate hexahydrate and ethanol were mixed to obtain a 0.2 mol / L cobalt nitrate hexahydrate ethanol solution. Biomass-derived porous carbon and cobalt nitrate hexahydrate ethanol solution were mixed, and after standing, the mixture was transferred to a tube furnace, heated to 850°C at 10°C / min and held at that temperature for 0.5-1.5 hours, and then cooled to obtain product 3. After mixing products 1, 2, and 3, a coupling agent is added and mixed to obtain a composite loss material.

5. The high-power electromagnetic compatibility composite absorbing material according to claim 3, characterized in that: The microwave absorber also includes 0.5-2.5 parts by weight of electrical loss material.

6. The high-power electromagnetic compatibility composite absorbing material according to claim 5, characterized in that: The electrical loss material is at least one of carbon black and graphite.

7. The high-power electromagnetic compatibility composite absorbing material according to claim 2, characterized in that: The solvent-based adhesive is a phenolic resin.

8. The high-power electromagnetic compatibility composite absorbing material according to claim 2, characterized in that: The dispersant is at least one of Triton TX-100, sodium dodecyl sulfonate SDS, or sodium dodecylbenzene sulfonate SDBS.

9. The high-power electromagnetic compatibility composite absorbing material according to claim 2, characterized in that: The auxiliary agent is a coupling agent; And / or; the solvent is ethanol.

10. A method for preparing a high-power electromagnetic compatibility composite absorbing material, characterized in that: Includes the following steps: Weigh out each ingredient according to the formula; A microwave absorber, solvent-based binder, dispersant, additives, and solvent are mixed to obtain a microwave absorbing resin composite solution. A composite microwave absorbing resin solution is coated onto the surface of an aramid paper honeycomb core, and then hot-pressed to obtain a composite microwave absorbing material.