A method for preparing composite electromagnetic absorbing material

Abstract

A method for preparing a composite electromagnetic absorbing material belongs to the field of nanomaterial technology. Method: SiBON powder is dispersed in a solvent, reduced graphene oxide is added, and the mixture is mixed to obtain A; a silane coupling agent is dispersed in the solvent, acid is added and the pH value is controlled to be 1-3, and B is obtained after a hydrolysis reaction; A and B are mixed, reacted until stratification, and the solid material is collected to obtain SiBON-rGO. The present invention successfully adjusts the complex dielectric constant and impedance matching of the composite material using SiBON ceramics, and introduces a rich interface to greatly improve its polarization loss. The SiBON content can adjust the balance between conductivity loss and polarization loss. A composite structure with an outer layer of SiBON ceramics and an inner layer of reduced graphene oxide is formed. This structure allows electromagnetic waves to be successfully induced into the interior of the material when incident, and the internal graphene layer is used to absorb the electromagnetic waves. It is suitable for the preparation of SiBON / rGO.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomaterials, and in particular relates to a composite electromagnetic absorbing material and a preparation method thereof. Background Art

[0002] With the application of 5G technology and the popularization of high-power electronic and electrical equipment, the impact of electromagnetic radiation on susceptible populations is gradually increasing, both in industrial production and in daily life, and its impact on the compatible operation of multiple devices is becoming increasingly obvious. Electromagnetic wave stealth refers to the lack of reflection effect on microwave bands in the UHF to ELF band, which means shielding radar, communication and other signals. Material stealth refers to the use of the electromagnetic properties of the material itself to complete the conversion of electromagnetic wave energy. This process converts the photon vibration of the electromagnetic wave into the lattice vibration (i.e., phonon vibration) within the material. Material stealth has the advantages of simple implementation, a large variety, and strong environmental adaptability, making it a focus of attention for materials researchers. Especially in the civilian field, the impact of electromagnetic wave radiation is not a single active radiation. The radiation it receives may come from all directions. Refining the structure and appearance alone cannot effectively solve the problem of electromagnetic wave radiation pollution. There are many ways to make materials invisible. They can be transformed into various shapes and their morphology can be changed through material processing methods. The outer layer of the material can also be processed into a protective layer through coating, landfilling and other methods. It can achieve effective electromagnetic absorption in harsh environments such as high temperature, acid and alkali, and has stronger environmental adaptability.

[0003] At present, the research on electromagnetic absorption materials at home and abroad mainly includes ferrite electromagnetic absorption materials, metal powder materials, ceramic materials and composite materials. Among them, the composite of carbon materials and low-dielectric wave-transmitting ceramics is an effective way to obtain high-performance absorbing materials.

[0004] Graphene, with its excellent electrical, thermal, and mechanical properties and high specific surface area, is an excellent absorber. Graphene's unique layered structure and the introduction of defects not only enhance its impedance sufficiency, providing vacancies for transitions from adjacent levels to the Fermi level, but also introduce fault polarization attenuation and bipolarization attenuation, promoting electromagnetic wave absorption. However, when the complex dielectric constant is high and the complex permeability is low, the impedance sufficiency deviates significantly from the zero-reflection condition. Therefore, to achieve optimal absorption, a method for adjusting impedance matching must be devised. Summary of the Invention

[0005] The purpose of the present invention is to solve the above-mentioned technical problems and to provide a method for preparing a composite electromagnetic absorbing material.

[0006] A method for preparing a composite electromagnetic absorbing material is implemented by the following steps:

[0007] 1. Disperse SiBON powder in a solvent, then add reduced graphene oxide and mix well to obtain solution A;

[0008] 2. Disperse the silane coupling agent in the solvent, add acid and control the pH value to 1-3, and obtain solution B after reaction;

[0009] 3. The above solution A and solution B are mixed, reacted until stratification, and solid matter is collected to obtain SiBON-rGO, which is a composite electromagnetic absorbing material, thereby completing the preparation.

[0010] Furthermore, the mass ratio of the SiBON powder to the reduced graphene oxide in step 1 is (1-1.5):(39-41).

[0011] Furthermore, the solvent in step 1 is deionized water; the mass volume ratio of the SiBON powder to deionized water is 0.1 g:50 mL.

[0012] Furthermore, the solvent in step 2 is deionized water; the volume ratio of the silane coupling agent to deionized water is 1 mL:5 mL.

[0013] Furthermore, the dispersion methods in steps 1 and 2 are both electromagnetic stirring.

[0014] Furthermore, the silane coupling agent in step 2 is KH-560.

[0015] Furthermore, the acid in step 2 is concentrated sulfuric acid.

[0016] Furthermore, the hydrolysis reaction in step 2 is ultrasonicated for 5 to 10 minutes.

[0017] Furthermore, in step 3, the volume ratio of solution A to solution B is 1:20.

[0018] Furthermore, the reaction in step 3 is heated to 75-85° C. in a water bath.

[0019] Furthermore, the preparation method of the SiBON powder in step 1 is as follows:

[0020] Boric acid and silicon nitride were mixed in a mass ratio of 48:52 and wet-milled for 4 hours, then dried at 70°C for 24 hours, and heat-treated at 450°C for 4 hours. After being ground into powder, the mixture was sintered at 1700°C for 1 hour. Finally, fine powder with d50 = 500 μm was obtained by crushing and grinding to obtain SiBON powder, thereby completing the preparation.

[0021] In this embodiment, the heat treatment is carried out in a box furnace;

[0022] The sintering is carried out in a large sintering furnace;

[0023] The crushing and grinding are as follows: the crushed material is crushed by a crusher and then ground into fine powder.

[0024] The beneficial technical effects of the present invention are as follows:

[0025] This invention uses a chemical grafting method to produce a composite electromagnetic absorber with a unique SiBON / rGO cladding structure, thereby mitigating the inherent high impedance matching characteristics of reduced graphene oxide and improving electromagnetic absorption performance. By adjusting the SiBON ceramic content, the present invention controls the interaction between different dielectric loss mechanism balances. The preparation method is simple, environmentally friendly, and efficient, with minimal requirements for related equipment, allowing for the rapid production of large quantities of the absorber.

[0026] After being treated with the hydrolyzed silane coupling agent KH-560, the SiBON ceramic powder can crosslink with rGO and stably exist between graphene sheets and different small particles. The ceramic particles preferentially react with the highly active functional groups on the edges of rGO to achieve bonding between the ceramic and rGO, and preferentially grow along the (110) crystal plane to achieve chemical connection between different phases. The present invention successfully adjusts the complex dielectric constant and impedance matching of the composite material using SiBON ceramics, and introduces a rich interface to significantly improve its polarization loss. The SiBON content can adjust the balance between conductivity loss and polarization loss.

[0027] The excellent electromagnetic absorption performance of the SiBON / rGO composite material of the present invention can be attributed to its unique structure. In the liquid-phase reaction system of the present invention, stronger interfacial polarization is easily formed. Furthermore, the preferred orientation of silicon dioxide during its formation in the SiBON ceramic allows for the orientation and fixation of appropriate lattice planes at the edges of the reduced graphene oxide, forming a composite structure with an outer SiBON ceramic layer and an inner reduced graphene oxide layer. This structure allows incident electromagnetic waves to be successfully channeled into the material, where they are absorbed by the internal graphene layer.

[0028] The present invention is suitable for the preparation of SiBON / rGO composite electromagnetic wave absorbing materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 are SEM images and TEM images of the SiBON / rGO composite material prepared in Example 4; wherein (a) is the SEM image of Example 4, (b) is the SEM image of Example 4, (c) is the TEM image of Example 4, and (d) is the TEM image of Example 4;

[0030] Figure 2 Schematic diagram of the microwave absorption performance of the SiBON / rGO composite material prepared in Example 1;

[0031] Figure 3 Schematic diagram of the microwave absorption performance of the SiBON / rGO composite material prepared in Example 2;

[0032] Figure 4 Schematic diagram of the microwave absorption performance of the SiBON / rGO composite material prepared in Example 3;

[0033] Figure 5 Schematic diagram of the wave absorption performance of the SiBON / rGO composite material prepared in Example 4. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0035] Specific embodiment 1: This embodiment provides a method for preparing a composite electromagnetic absorbing material, which is implemented by the following steps:

[0036] 1. Disperse SiBON powder in a solvent, then add reduced graphene oxide and mix well to obtain solution A;

[0037] 2. Disperse the silane coupling agent in the solvent, add acid and control the pH value to 1-3, and obtain solution B after reaction;

[0038] 3. The above solution A and solution B are mixed, reacted until stratification, and solid matter is collected to obtain SiBON-rGO, which is a composite electromagnetic absorbing material, thereby completing the preparation.

[0039] In this embodiment, the reduced graphene oxide is added in small amounts and multiple times.

[0040] In step 3 of this embodiment, the reaction until separation is achieved refers to when the solids turn into flocs and float to the surface.

[0041] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the mass ratio of SiBON powder to reduced graphene oxide in step 1 is (1-1.5):(39-41). Other steps and parameters are the same as those in specific embodiment 1.

[0042] Specific embodiment 3: This embodiment differs from specific embodiment 2 in that the mass ratio of SiBON powder to reduced graphene oxide in step 1 is 1:40. Other steps and parameters are the same as those in specific embodiment 2.

[0043] Specific embodiment 4: This embodiment differs from specific embodiment 1 in that the solvent in step 1 is deionized water, and the mass volume ratio of the SiBON powder to deionized water is 0.1 g:50 mL. Other steps and parameters are the same as those in specific embodiment 1.

[0044] Specific embodiment 5: This embodiment differs from specific embodiment 1 in that the solvent in step 2 is deionized water, and the volume ratio of the silane coupling agent to deionized water is 1 mL:5 mL. Other steps and parameters are the same as those in specific embodiment 1.

[0045] Specific embodiment 6: This embodiment differs from specific embodiment 1 in that the dispersion method in steps 1 and 2 is electromagnetic stirring. Other steps and parameters are the same as those in specific embodiment 1.

[0046] Specific embodiment 7: This embodiment differs from specific embodiment 1 in that the silane coupling agent in step 2 is KH-560. Other steps and parameters are the same as those in specific embodiment 1.

[0047] Specific embodiment 8: This embodiment differs from specific embodiment 1 in that the acid in step 2 is concentrated sulfuric acid. The other steps and parameters are the same as those in specific embodiment 1.

[0048] Specific embodiment 9: This embodiment differs from specific embodiment 1 in that the hydrolysis reaction in step 2 is ultrasonically treated for 5 to 10 minutes. Other steps and parameters are the same as those in specific embodiment 1.

[0049] Specific embodiment 10: This embodiment differs from specific embodiment 1 in that the volume ratio of solution A to solution B in step 3 is 1:20. The other steps and parameters are the same as those in specific embodiment 1.

[0050] Specific embodiment 11: This embodiment differs from specific embodiment 1 in that the reaction in step 3 is heated in a water bath at 75-85° C. The other steps and parameters are the same as those in specific embodiment 1.

[0051] Specific embodiment 12: This embodiment differs from specific embodiment 1 in that the preparation method of SiBON powder in step 1 is as follows:

[0052] Boric acid and silicon nitride were mixed in a mass ratio of 48:52, wet-milled for 4 hours, dried at 70°C for 24 hours, heat-treated at 450°C for 4 hours, ground into a powder, and sintered at 1700°C for 1 hour. Finally, the powder was crushed and ground to obtain a fine powder with a d50 of 500 μm, thereby completing the preparation process. Other steps and parameters were the same as those in the first embodiment.

[0053] In this embodiment, the heat treatment is carried out in a box-type furnace; the sintering is carried out in a large sintering furnace; and the crushing and grinding are carried out by crushing in a crusher and then grinding into fine powder.

[0054] The beneficial effects of the present invention are verified by the following examples:

[0055] The reduced graphene oxide used in the following examples was purchased from AP-3 reduced graphene oxide from Luobei Yunshan Carbon Industry; the SiBON powder was homemade in the laboratory; and the other raw materials used were all commercially available products.

[0056] Example 1:

[0057] A method for preparing a composite electromagnetic absorbing material is implemented by the following steps:

[0058] 1. Disperse SiBON powder in a solvent, then add reduced graphene oxide and mix well to obtain solution A;

[0059] 2. Disperse the silane coupling agent in the solvent, add acid and control the pH value to 1-3, and obtain solution B after hydrolysis reaction;

[0060] 3. The above solution A and solution B are mixed and reacted until stratification, and the solid matter is collected to obtain SiBON-rGO (referred to as sample powder in the following experiments), which is a composite electromagnetic absorbing material, thereby completing the preparation.

[0061] In step 1 of this embodiment, the amount of SiBON powder is 0.1 g, and the amount of reduced graphene oxide is 1 g.

[0062] In step 1 of this embodiment, the solvent is deionized water; the mass volume ratio of the SiBON powder to deionized water is 0.1 g:50 mL.

[0063] In step 2 of this embodiment, the solvent is deionized water; the volume ratio of the silane coupling agent to deionized water is 2 mL:10 mL.

[0064] The dispersion methods described in steps 1 and 2 of this embodiment are both electromagnetic stirring.

[0065] The silane coupling agent in step 2 of this embodiment is KH-560.

[0066] The acid in step 2 of this embodiment is concentrated sulfuric acid.

[0067] The hydrolysis reaction in step 2 of this embodiment is carried out by ultrasonication for 5 to 10 minutes.

[0068] In step 3 of this embodiment, the volume ratio of solution A to solution B is 1:20.

[0069] The reaction in step 3 of this embodiment was heated to 80°C in a water bath.

[0070] The preparation method of the SiBON powder described in step 1 of this embodiment is as follows:

[0071] Boric acid and silicon nitride were mixed in a mass ratio of 48:52 and wet-milled for 4 hours, then dried at 70°C for 24 hours, and heat-treated at 450°C for 4 hours. After being ground into powder, the mixture was sintered at 1700°C for 1 hour. Finally, fine powder with d50 = 500 μm was obtained by crushing and grinding to obtain SiBON powder, thereby completing the preparation.

[0072] Example 2:

[0073] This embodiment differs from embodiment 1 in that the amount of reduced graphene oxide in step 1 is 2 g. Other steps are the same as those in embodiment 1.

[0074] Example 3:

[0075] This embodiment differs from embodiment 1 in that the amount of reduced graphene oxide in step 1 is 3 g. Other steps are the same as those in embodiment 1.

[0076] Example 4:

[0077] This embodiment differs from embodiment 1 in that the amount of reduced graphene oxide in step 1 is 4 g. Other steps are the same as those in embodiment 1.

[0078] The SEM and TEM images of the SiBON / rGO composite material prepared in Example 4 are as follows: Figure 1 As shown; wherein, (a) is the SEM image of Example 4, (b) is the SEM image of Example 4, (c) is the TEM image of Example 4, and (d) is the TEM image of Example 4. Figure 1 It can be seen that SiBON / rGO forms the white part in the SEM image, the black part in the TEM image, and the SiBON realizes the electromagnetic wave transmission property on the outside to improve the impedance matching of the composite material, while the rGO realizes the electromagnetic wave loss on the inside.

[0079] Comparative Example 1

[0080] Compared with Example 4, the only difference is that the added amount of reduced graphene oxide is modified to 5 g.

[0081] Comparative Example 2

[0082] Compared with Example 4, the only difference is that the addition of concentrated sulfuric acid is omitted.

[0083] Comparative Example 3

[0084] Compared with Example 4, the only difference is that the addition of 4 g of reduced graphene oxide is modified to the addition of 95.24 g of aqueous graphene oxide slurry (4.2 wt.% solid content) purchased from Luobei Yunshan Carbon Industry.

[0085] Effect verification

[0086] (1) In order to verify the microwave absorption performance of the products obtained in the present invention, microwave absorption tests were conducted on the products in Examples 1-4 and Comparative Examples 1-3. The test method is as follows: The electromagnetic wave absorption performance test mainly measures the complex dielectric constant and complex magnetic permeability of the material and uses the following formula:

[0087]

[0088]

[0089] Among them, tanδ E : dielectric loss tangent; ε' is the real part of the complex dielectric constant; ε" is the imaginary part of the complex dielectric constant; tanδ m : The dielectric loss tangent μ' is the real part of the complex magnetic permeability, and μ" is the imaginary part of the complex magnetic permeability.

[0090] The quality of the absorption performance can be expressed objectively by the reflection loss (RL) value, which can be expressed by the following formula based on the transmission line theory:

[0091]

[0092]

[0093] where f, d, and c are the frequency, absorber thickness, and speed of light in free space, respectively; Z in is the input impedance; ε r Complex dielectric constant; μ r Complex magnetic permeability; j is the imaginary unit.

[0094] A reflection loss RL value <-10dB indicates 90.00% effective absorption, a reflection loss RL value <-20dB indicates 99.00% effective absorption, and a reflection loss RL value <-30dB indicates 99.90% effective absorption. The attenuation of electromagnetic waves in a material can be expressed by the following formula:

[0095]

[0096] where α is the decay constant.

[0097] The reflection loss value of the material was calculated. Agilent VNA, Model N5245A network vector analyzer was used to study the electromagnetic wave absorption performance of the sample. The sample powder and paraffin wax were uniformly mixed in a molten state at a ratio of 20 wt.% of the sample mass to the total mass. The mixture was then pressed into a mold with an inner diameter of 3.04 mm and an outer diameter of 7 mm to obtain the desired hollow coaxial cylinder. Within the frequency range of 2 to 18 GHz, 201 sampling points were used. The real and imaginary parts of the sample's complex dielectric constant and complex magnetic permeability were retained. The dielectric loss tangent and magnetic loss tangent were equal to the ratio of the real part to the imaginary part. The test results are shown in Table 1.

[0098] Table 1 Microwave absorption test

[0099]

[0100] As can be seen from Table 1, the products of Examples 1-4 all have the best microwave absorption in the Ku band; as can be seen from the comparison between Example 4 and Comparative Examples 1-3, the type and proportion of raw materials are very important for the microwave absorption performance.

[0101] The present invention also tested the microwave absorption performance of the product of Example 4 against the following materials. Device filling refers to the ratio of the composite material to the mass of the paraffin ring required for testing; thickness refers to the thickness of the device formed by the composite material. The test results are shown in Table 2.

[0102] Table 2 Absorption properties of other materials

[0103]

[0104]

[0105] It can be seen from Table 2 that this material has the thinnest thickness while achieving the average reflection loss value.

[0106] (2) In order to verify the wave absorption performance of the product obtained in the present invention at different frequencies, the return loss test of SiBON / rGO prepared in Examples 1-4 was carried out in the frequency range of 2-18 GHz, and the test method was: vector network analyzer coaxial ring method test. The return loss test is mainly to determine the complex dielectric constant and complex magnetic permeability of the material and calculate the reflection loss value of the material through the above formula (1-5). The electromagnetic wave absorption performance of the sample was studied using Agilent VNA, N5245A network vector analyzer; 20 wt.% of the sample powder accounting for the total mass was added to the molten paraffin and mixed evenly, and pressed into a mold with an inner diameter of 3.04 mm and an outer diameter of 7 mm to obtain the required hollow coaxial cylinder. In the frequency range of 2 to 18 GHz, the number of sampling points was 201, and the real and imaginary parts of the complex dielectric constant and complex magnetic permeability of the sample were retained. The dielectric loss tangent and the magnetic loss tangent were equal to the ratio of the real part to the imaginary part. The test results are as follows. Figure 2 shown.

[0107] Figure 2 Schematic diagram of the wave absorption performance of the SiBON / rGO composite materials prepared in Examples 1-4. (a) is a schematic diagram of the wave absorption performance of Example 1, (b) is a schematic diagram of the wave absorption performance of Example 2, (c) is a schematic diagram of the wave absorption performance of Example 3, and (d) is a schematic diagram of the wave absorption performance of Example 4. Figure 2It can be seen that when SiBON:rGO=1:40, the composite material has the smallest reflection loss value and the largest absorption bandwidth, that is, Example 4 has better electromagnetic wave absorption performance than other examples.

[0108] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a composite electromagnetic absorbing material, characterized in that It is implemented as follows:

1. Disperse SiBON powder in a solvent, then add reduced graphene oxide and mix well to obtain solution A; 2. Disperse the silane coupling agent in the solvent, add acid and control the pH value to 1-3, and obtain solution B after hydrolysis reaction; 3. The above solution A and solution B are mixed, reacted until delamination, and the solid matter is collected to obtain SiBON-rGO, which is a composite electromagnetic absorbing material, thereby completing the preparation; The mass ratio of SiBON powder to reduced graphene oxide in step 1 is (1-1.5):(39-41); The acid in step 2 is concentrated sulfuric acid; The preparation method of the SiBON powder in step 1 is as follows: Boric acid and silicon nitride were mixed in a mass ratio of 48:52 and wet-milled for 4 hours, then dried at 70°C for 24 hours, and heat-treated at 450°C for 4 hours. After being ground into powder, the mixture was sintered at 1700°C for 1 hour. Finally, fine powder with d50 = 500 μm was obtained by crushing and grinding to obtain SiBON powder, thereby completing the preparation.

2. The method for preparing a composite electromagnetic absorbing material according to claim 1, characterized in that The solvent in step 1 is deionized water; the mass volume ratio of the SiBON powder to deionized water is 0.1 g:50 mL.

3. The method for preparing a composite electromagnetic absorbing material according to claim 1, characterized in that The solvent in step 2 is deionized water; the volume ratio of the silane coupling agent to deionized water is 1 mL:5 mL.

4. The method for preparing a composite electromagnetic absorbing material according to claim 1, characterized in that The silane coupling agent in step 2 is KH-560.

5. The method for preparing a composite electromagnetic absorbing material according to claim 1, characterized in that The hydrolysis reaction conditions in step 2 are ultrasonication for 5 to 10 minutes.

6. The method for preparing a composite electromagnetic absorbing material according to claim 1, characterized in that The volume of solution A and solution B in step 3 is 1:

20.

7. The method for preparing a composite electromagnetic absorbing material according to claim 1, characterized in that The reaction conditions in step 3 are a water bath heated to 75-85°C.

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