Preparation method of heat-conducting wave-absorbing material for electromagnetic device shell

Abstract

The application relates to the technical field of materials, and discloses a preparation method of a heat-conducting wave-absorbing material for an electromagnetic device shell, the heat-conducting wave-absorbing material is prepared by compounding methyl vinyl silicone rubber as a main raw material with heat-conducting wave-absorbing additives and other auxiliary materials through mixing and vulcanization processes, wherein the heat-conducting wave-absorbing additives are a composite of modified boron nitride and nitrogen oxide doped porous carbon, the surface of the modified boron nitride contains substituted hydroxyl groups generated by ring-opening addition reaction, can interact with the epoxidized silicone rubber, greatly improves the interfacial bonding force between the heat-conducting wave-absorbing additives and the silicone rubber matrix, is beneficial to uniform dispersion of the heat-conducting wave-absorbing additives in the silicone rubber matrix, and forms continuous and stable heat-conducting wave-absorbing channels in the silicone rubber matrix by using the excellent heat-conducting performance of the modified boron nitride and the excellent wave-absorbing performance of the nitrogen-doped porous carbon material, thereby excellent heat-conducting and electromagnetic shielding effects are generated, and the heat-conducting wave-absorbing material can be directly applied to the preparation of electromagnetic device shells.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and specifically to a method for preparing a thermally conductive and wave-absorbing material for the casing of electromagnetic devices. Background Technology

[0002] With the rapid development and widespread application of 5G technology, all aspects of our lives are undergoing unprecedented changes. The core of 5G technology lies in using high-frequency electromagnetic waves for data transmission, which requires electromagnetic equipment to have extremely high performance and stability to ensure fast and accurate data transmission. However, these electromagnetic devices are affected by various environmental factors during operation, such as temperature, humidity, dust, and electromagnetic interference. To ensure the normal operation of the equipment and extend its service life, electromagnetic equipment casings have emerged. Electromagnetic equipment casings are typically made of materials such as metal, engineering plastics, or rubber, which can prevent external dust, moisture, and other harmful substances from penetrating the equipment, protecting it from damage. They also provide good support for the electromagnetic equipment, preventing damage during transportation or use.

[0003] Since 5G products consume approximately 2.5 to 3 times more power than 4G products, the casing of electromagnetic equipment needs to have excellent high-temperature resistance. Silicone rubber material has excellent insulation, high-temperature resistance, and aging resistance, and can operate for a long time in high-temperature environments without damage. It can adapt to the high-temperature environment generated during the operation of electromagnetic equipment. However, silicone rubber material has poor thermal conductivity and electromagnetic shielding performance, which not only greatly reduces the reliability of electromagnetic equipment, but also causes electromagnetic interference and electromagnetic pollution. Therefore, it still has shortcomings in practical applications.

[0004] Currently, the thermal conductivity and wave absorption properties of silicone rubber can be improved by combining inorganic materials with thermal conductivity and wave absorption properties. However, there is a mutual constraint between thermally conductive particles and wave-absorbing particles, and there are also interface problems between these inorganic particles and silicone rubber. Adding large amounts will inevitably have a negative impact on the mechanical properties of silicone rubber. Therefore, this invention provides a thermally conductive and wave-absorbing material that can be directly used as the shell of electromagnetic devices and has good thermal conductivity and wave absorption effects at the same time. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing a thermally conductive and microwave-absorbing material for the housing of electromagnetic equipment, which solves the problem of poor thermal conductivity and microwave absorption performance of silicone rubber materials.

[0007] (II) Technical Solution

[0008] A method for preparing a thermally conductive and microwave-absorbing material for the housing of an electromagnetic device, wherein the thermally conductive and microwave-absorbing material comprises the following components in parts by weight: 80-90 parts of silicone rubber base material, 10-20 parts of epoxidized silicone rubber, 15-25 parts of thermally conductive and microwave-absorbing additives, and 0.5-1.5 parts of peroxide initiator;

[0009] The thermally conductive and microwave-absorbing additive is a composite of modified boron nitride and nitrogen oxide-doped porous carbon.

[0010] The preparation method includes the following steps:

[0011] Step 1: Weigh each raw material according to the weight proportions. First, put the silicone rubber base material, epoxidized silicone rubber and thermally conductive and microwave absorbing additive into the mixer for mixing. After forming a uniform mixture, let it stand for 6-8 hours. Then, add the peroxide initiator into the mixer for mixing to form a mixed silicone rubber material.

[0012] The second step is to calender the mixed silicone rubber material to form silicone rubber sheets, and then vulcanize it using a flat vulcanizing machine. The vulcanization temperature is controlled between 170-180℃, the time is 5-15 minutes, and the pressure is 5-10MPa. After vulcanization, it is placed in a temperature environment of 180-200℃ for 2-4 hours, and then discharged to obtain the thermally conductive and microwave-absorbing material.

[0013] Furthermore, the silicone rubber base material is methyl vinyl silicone rubber.

[0014] Furthermore, the epoxidized silicone rubber is prepared by epoxidizing methyl vinyl silicone rubber with 3-chloroperoxybenzoic acid as the epoxidizing agent.

[0015] Furthermore, the thermally conductive and microwave-absorbing additive is prepared using the following method:

[0016] Modified boron nitride and nitrogen oxide-doped porous carbon in a mass ratio of 1:1 are mixed with purified water. Stirring is started and the mixture is mechanically stirred at 50-60℃ for 1-2 hours. After stirring is stopped and the mixture is allowed to stand for 20-40 minutes, the solid material is separated and then vacuum dried to obtain the thermally conductive and microwave-absorbing additive.

[0017] In the above technical solution, the quaternary ammonium nitrogen positive ions on the modified boron nitride surface carry positive charges, while the nitrogen oxide-doped porous carbon surface contains oxygen-containing functional groups such as carboxyl groups, which are negatively charged in aqueous solution. They can adsorb each other under electrostatic action to form a complex, namely a thermally conductive and microwave-absorbing additive.

[0018] Furthermore, the modified boron nitride is prepared using the following method:

[0019] Hydroxylated boron nitride and tetrahydrofuran were mixed and ultrasonically dispersed to form a homogeneous dispersion. Nitrogen gas was introduced to purge the air. Then, 2,3-epoxypropyltrimethylammonium chloride and a phase transfer catalyst were added to the dispersion in sequence. The temperature was controlled at 60-65℃ and stirred for 4-6 hours. The solid material was separated by centrifugation, washed, and dried to obtain modified boron nitride.

[0020] In the above technical solution, the substituted hydroxyl groups of hydroxylated boron nitride can undergo ring-opening addition with the epoxy groups in the 2,3-epoxypropyltrimethylammonium chloride structure under the action of a phase transfer catalyst, thereby modifying a large number of quaternary ammonium nitrogen cations on the surface of boron nitride nanosheets to obtain modified boron nitride.

[0021] Furthermore, the preparation method of the hydroxylated boron nitride is as follows: add boron nitride nanosheets to a sodium hydroxide solution with a concentration of 4-5 mol / L, stir and disperse evenly, keep in a temperature environment of 90-100℃ for 6-8 hours, and then cool down and discharge the material.

[0022] Furthermore, the phase transfer catalyst is any one of tetrabutylammonium bisulfate, tetrabutylammonium bromide, or tetramethylammonium bromide.

[0023] Furthermore, the nitrogen oxide-doped porous carbon is prepared using the following method:

[0024] Step 1: Mix xanthan gum with a 1:1 volume ratio of ethanol and purified water solution and stir to form a homogeneous solution. Then add isonicotinic acid and catalyst to the solution. After the addition is complete, stir at room temperature for 6-8 hours. Separate the material, wash and vacuum dry to obtain the nitrogen-containing carbon precursor.

[0025] Step 2: Mix nitrogen-containing carbon precursor and potassium hydroxide at a mass ratio of 1:2-4, grind evenly, place in a tube furnace, raise the temperature to 750-800℃ at a heating rate of 3-5℃ / min, under nitrogen protection throughout the process, calcine for 1-3 hours, and then discharge to obtain nitrogen-doped porous carbon.

[0026] Step 3: Mix nitrogen-doped porous carbon with hydrogen peroxide solution and oxidize at 80-90℃ for 8-12 hours. Separate the material, wash and vacuum dry it to obtain nitrogen oxide-doped porous carbon.

[0027] In the above technical solution, with the assistance of a catalyst, the substituted hydroxyl groups in the xanthan gum structure can undergo esterification condensation with the carboxyl groups in isonicotinic acid, thereby introducing pyridine groups into the xanthan gum structure to obtain a nitrogen-containing carbon precursor. Potassium hydroxide is used to activate and create pores in the precursor, followed by high-temperature calcination to obtain nitrogen-doped porous carbon. On the one hand, the porous structure of the porous carbon material can reflect and scatter electromagnetic waves, thus achieving multiple absorptions of electromagnetic waves and exhibiting good electromagnetic shielding effects. On the other hand, during the high-temperature calcination process, nitrogen doping introduces defect structures such as pyridine nitrogen. These defect structures can generate electric dipoles, improving the dielectric loss effect of the carbon material and further enhancing its wave absorption performance. Finally, hydrogen peroxide is used as an oxidant to oxidize the nitrogen-doped porous carbon, causing substituted carboxyl groups and other oxygen-containing functional groups to appear on its surface, thus obtaining nitrogen oxide-doped porous carbon.

[0028] Furthermore, in step one, the catalyst is a mixture of dicyclohexylcarbodiimide and 4-dimethylaminopyridine in a mass ratio of 1:0.2-0.4.

[0029] Furthermore, in step three, the volume fraction of the hydrogen peroxide solution is 20-30%.

[0030] (iii) Beneficial technical effects

[0031] This invention prepares a composite of modified boron nitride and nitrogen oxide-doped porous carbon as a thermally conductive and electromagnetically absorbing additive. On one hand, the modified boron nitride surface contains substituted hydroxyl groups generated by ring-opening addition reactions, which can interact with epoxidized silicone rubber during subsequent high-temperature processing. This greatly enhances the interfacial bonding force between the thermally conductive and electromagnetically absorbing additive and the silicone rubber matrix, facilitating its uniform dispersion in the silicone rubber matrix. Utilizing the excellent thermal conductivity of modified boron nitride and the excellent electromagnetic absorption properties of nitrogen-doped porous carbon, a continuous and stable thermally conductive and electromagnetically absorbing pathway is formed in the silicone rubber matrix, resulting in excellent thermal conductivity and electromagnetic shielding effects. This can be directly applied to the manufacture of electromagnetic equipment housings.

[0032] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is an infrared analysis test image of modified boron nitride. Detailed Implementation

[0035] To facilitate understanding of the present invention, a more complete description is provided below. Preferred embodiments of the invention are given below. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0036] Example 1

[0037] A thermally conductive and microwave-absorbing material for the housing of an electromagnetic device comprises the following components in parts by weight: 80 parts of methyl vinyl silicone rubber, 10 parts of epoxy silicone rubber, 15 parts of thermally conductive and microwave-absorbing additives, and 0.5 parts of dicumyl peroxide.

[0038] The preparation method of the thermally conductive and microwave-absorbing material includes the following steps:

[0039] Step 1: Weigh each raw material according to the weight proportions. First, put methyl vinyl silicone rubber, epoxidized silicone rubber and thermally conductive and microwave-absorbing additives into the mixer for mixing. After forming a uniform mixture, let it stand for 6 hours. Then, add dicumyl peroxide to the mixer for mixing to form a mixed silicone rubber material.

[0040] The second step is to calender the mixed silicone rubber material to form silicone rubber sheets, and then vulcanize it using a flat vulcanizing machine. The vulcanization temperature is controlled at 170℃ for 5 minutes and the pressure is 5MPa. After vulcanization, it is placed in a temperature environment of 180℃ for 2 hours and then discharged to obtain the thermally conductive and microwave-absorbing material.

[0041] Example 2

[0042] A thermally conductive and microwave-absorbing material for the housing of an electromagnetic device comprises the following components in parts by weight: 85 parts of methyl vinyl silicone rubber, 12 parts of epoxy silicone rubber, 18 parts of thermally conductive and microwave-absorbing additives, and 1 part of peroxide initiator.

[0043] The preparation method of the thermally conductive and microwave-absorbing material includes the following steps:

[0044] Step 1: Weigh each raw material according to the weight proportions. First, put the methyl vinyl silicone rubber, epoxy silicone rubber and thermally conductive and microwave absorbing additive into the mixer for mixing. After forming a uniform mixture, let it stand for 8 hours. Then, add dicumyl peroxide into the mixer for mixing to form a mixed silicone rubber material.

[0045] The second step is to calender the mixed silicone rubber material to form silicone rubber sheets, and then vulcanize it using a flat vulcanizing machine. The vulcanization temperature is controlled at 180℃ for 10 minutes and the pressure is 5MPa. After vulcanization, it is placed in a temperature environment of 200℃ for 3 hours and then discharged to obtain the thermally conductive and microwave-absorbing material.

[0046] Example 3

[0047] A thermally conductive and microwave-absorbing material for the housing of an electromagnetic device comprises the following components in parts by weight: 90 parts of methyl vinyl silicone rubber, 20 parts of epoxy silicone rubber, 25 parts of thermally conductive and microwave-absorbing additives, and 1.5 parts of peroxide initiator.

[0048] The preparation method of the thermally conductive and microwave-absorbing material includes the following steps:

[0049] Step 1: Weigh each raw material according to the weight proportions. First, put the methyl vinyl silicone rubber, epoxy silicone rubber and thermally conductive and microwave absorbing additive into the mixer for mixing. After forming a uniform mixture, let it stand for 8 hours. Then, add dicumyl peroxide into the mixer for mixing to form a mixed silicone rubber material.

[0050] The second step is to calender the mixed silicone rubber material to form silicone rubber sheets, and then vulcanize it using a flat vulcanizing machine. The vulcanization temperature is controlled at 180℃ for 15 minutes and the pressure is 10MPa. After vulcanization, it is placed in a temperature environment of 200℃ for 4 hours and then discharged to obtain the thermally conductive and microwave-absorbing material.

[0051] The thermally conductive and microwave-absorbing materials used in the above embodiments were prepared using the following method:

[0052] Mix 5g of modified boron nitride and 5g of nitrogen oxide-doped porous carbon with purified water, turn on the stirrer, and mechanically stir at 50°C for 2 hours. After stirring is stopped and the mixture is allowed to stand for 30 minutes, the solid material is separated and vacuum dried to obtain the thermally conductive and microwave-absorbing additive.

[0053] The modified boron nitride was prepared using the following method:

[0054] Step A: Add 2g of boron nitride nanosheets to 60mL of 5mol / L sodium hydroxide solution, stir and disperse evenly, keep in a temperature environment of 95℃ for 6h, cool down and discharge the material to obtain hydroxylated boron nitride.

[0055] Step B: Mix 1.6g of hydroxylated boron nitride and tetrahydrofuran, disperse by ultrasonication to form a homogeneous dispersion, purge with nitrogen to remove air, then add 2.5g of 2,3-epoxypropyltrimethylammonium chloride and 0.3g of tetrabutylammonium bromide to the dispersion in sequence, control the temperature at 60℃, stir for 6 hours, centrifuge to separate the solid material, and after washing and drying, modified boron nitride can be obtained.

[0056] Figure 1 The image shows the infrared analysis results of modified boron nitride. As can be seen from the image, 3392 cm⁻¹ -1 The absorption peak at 2946 cm⁻¹ represents the stretching vibration of the hydroxyl group generated by the ring-opening reaction. -1 2873cm -1 The absorption peak at 1395 cm⁻¹ represents the hydrocarbon stretching vibration absorption peak in methyl and ethyl compounds. -1 The peak at this location represents the CN stretching vibration absorption peak in the quaternary ammonium nitrogen functional group.

[0057] Nitrogen oxide-doped porous carbon was prepared using the following method:

[0058] Step 1: Mix 2.4g xanthan gum with 150mL of a 1:1 mixture of ethanol and purified water and stir to form a homogeneous solution. Then add 1g isonicotinic acid, 0.8g dicyclohexylcarbodiimide and 0.24g 4-dimethylaminopyridine to the solution. After the addition is complete, stir at room temperature for 8 hours. Separate the material, wash and vacuum dry to obtain the nitrogen-containing carbon precursor.

[0059] Step 2: Mix 5g of nitrogen-containing carbon precursor and 20g of potassium hydroxide, grind them evenly, place them in a tube furnace, raise the temperature to 750℃ at a heating rate of 5℃ / min, keep the process under nitrogen protection, calcine for 2 hours, and then discharge the material to obtain nitrogen-doped porous carbon.

[0060] The nitrogen content in the nitrogen-doped porous carbon material was tested using a CHN-type elemental analyzer. The results showed that the nitrogen content was 6.91%. This nitrogen was doped into the porous carbon material in the form of pyridine nitrogen, which caused a large number of defect structures in the porous carbon material, which is beneficial to improving its microwave absorption effect.

[0061] Step 3: Mix 1.8g of nitrogen-doped porous carbon with 120mL of 30% hydrogen peroxide solution, oxidize at 85℃ for 9h, separate the material, wash and vacuum dry to obtain nitrogen oxide-doped porous carbon.

[0062] Comparative Example 1

[0063] A thermally conductive and wave-absorbing material for the housing of an electromagnetic device comprises the following components in parts by weight: 85 parts of methyl vinyl silicone rubber, 12 parts of epoxy silicone rubber, 9 parts of boron nitride nanosheets, 9 parts of activated carbon, and 1 part of peroxide initiator.

[0064] The preparation method of the thermally conductive and microwave-absorbing material includes the following steps:

[0065] Step 1: Weigh each raw material according to the weight proportions. First, put methyl vinyl silicone rubber, epoxidized silicone rubber, boron nitride nanosheets and activated carbon into a mixer for mixing. After forming a uniform mixture, let it stand for 8 hours. Then add dicumyl peroxide into the mixer for mixing to form a mixed silicone rubber material.

[0066] The second step is to calender the mixed silicone rubber material to form silicone rubber sheets, and then vulcanize it using a flat vulcanizing machine. The vulcanization temperature is controlled at 180℃ for 10 minutes and the pressure is 5MPa. After vulcanization, it is placed in a temperature environment of 200℃ for 3 hours and then discharged to obtain the thermally conductive and microwave-absorbing material.

[0067] Comparative Example 2

[0068] A thermally conductive and wave-absorbing material for the housing of an electromagnetic device comprises the following components in parts by weight: 85 parts of methyl vinyl silicone rubber, 12 parts of epoxy silicone rubber, 18 parts of boron nitride nanosheets, and 1 part of peroxide initiator.

[0069] The preparation method of the thermally conductive and microwave-absorbing material includes the following steps:

[0070] Step 1: Weigh each raw material according to the weight proportions. First, put methyl vinyl silicone rubber, epoxide silicone rubber and boron nitride nanosheets into a mixer and mix them to form a uniform mixture. Then let it stand for 8 hours. Next, add dicumyl peroxide to the mixer and mix it to form a mixed silicone rubber material.

[0071] The second step is to calender the mixed silicone rubber material to form silicone rubber sheets, and then vulcanize it using a flat vulcanizing machine. The vulcanization temperature is controlled at 180℃ for 10 minutes and the pressure is 5MPa. After vulcanization, it is placed in a temperature environment of 200℃ for 3 hours and then discharged to obtain the thermally conductive and microwave-absorbing material.

[0072] Comparative Example 3

[0073] A thermally conductive and microwave-absorbing material for the housing of an electromagnetic device comprises the following components in parts by weight: 85 parts of methyl vinyl silicone rubber, 12 parts of epoxy silicone rubber, 18 parts of activated carbon, and 1 part of peroxide initiator.

[0074] The preparation method of the thermally conductive and microwave-absorbing material includes the following steps:

[0075] Step 1: Weigh each raw material according to the weight proportions. First, put methyl vinyl silicone rubber, epoxide silicone rubber and activated carbon into a mixer for mixing. After forming a uniform mixture, let it stand for 8 hours. Then add dicumyl peroxide into the mixer for mixing to form a mixed silicone rubber material.

[0076] The second step is to calender the mixed silicone rubber material to form silicone rubber sheets, and then vulcanize it using a flat vulcanizing machine. The vulcanization temperature is controlled at 180℃ for 10 minutes and the pressure is 5MPa. After vulcanization, it is placed in a temperature environment of 200℃ for 3 hours and then discharged to obtain the thermally conductive and microwave-absorbing material.

[0077] The activated carbon was purchased from Anhui Xingheng Environmental Protection Technology Co., Ltd. as Grade A bamboo charcoal with a fixed carbon content of ≥90.0%.

[0078] The epoxy silicone rubber in the above embodiments and comparative examples was prepared using the following method:

[0079] Mix 5g of methyl vinyl silicone rubber with chloroform and stir to dissolve. Then add 1.75g ​​of 3-chloroperoxybenzoic acid. After the addition is complete, stir at room temperature for 48 hours. Then precipitate with methanol. Soak the precipitated material in purified water for 48 hours. After the precipitation is complete, remove the material and dry it under vacuum to obtain epoxide silicone rubber.

[0080] Performance testing

[0081] The thermally conductive and microwave-absorbing materials in Examples 1-3 and Comparative Examples 1-3 of the present invention were made into ring-shaped test samples with a thickness of 2 mm, an inner diameter of 3 mm, and an outer diameter of 5 mm. The microwave absorption performance of the samples at an electromagnetic parameter of 9.5 GHz was tested using a vector network analyzer.

[0082] The thermally conductive and microwave-absorbing materials from Examples 1-3 and Comparative Examples 1-3 of this invention were prepared into test samples with a size of 4cm × 2cm. The thermal conductivity of the samples was tested using a thermal conductivity meter, and the results are recorded in Table 1:

[0083]

[0084] Analysis of the test results shows that the thermally conductive and microwave-absorbing material prepared by adding thermally conductive and microwave-absorbing additives exhibits excellent thermal conductivity and microwave absorption performance. However, in Comparative Example 1, the thermally conductive and microwave-absorbing additives were replaced with equal amounts of boron nitride nanosheets and activated carbon. This may be because these additives agglomerated, failing to form stable and continuous thermally conductive and microwave-absorbing pathways in the silicone rubber matrix, resulting in a decrease in both thermal conductivity and microwave absorption performance. In Comparative Example 2, only boron nitride nanosheets were added, leading to a significant reduction in microwave absorption performance. In Comparative Example 3, only activated carbon was added, resulting in significantly poor thermal conductivity.

[0085] Based on the preferred embodiments of the present invention, and through the above description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing a thermally conductive and wave-absorbing material for the housing of an electromagnetic device, characterized in that, The thermally conductive and microwave-absorbing material comprises the following components in parts by weight: 80-90 parts of silicone rubber base, 10-20 parts of epoxidized silicone rubber, 15-25 parts of thermally conductive and microwave-absorbing additives, and 0.5-1.5 parts of peroxide initiator. The thermally conductive and microwave-absorbing additive is a composite of modified boron nitride and nitrogen oxide-doped porous carbon. The preparation method includes the following steps: Step 1: Weigh each raw material according to the weight proportions. First, put the silicone rubber base material, epoxidized silicone rubber and thermally conductive and microwave absorbing additive into the mixer for mixing. After forming a uniform mixture, let it stand for 6-8 hours. Then, add the peroxide initiator into the mixer for mixing to form a mixed silicone rubber material. The second step is to calender the mixed silicone rubber material to form silicone rubber sheets, and then vulcanize it using a flat vulcanizing machine. The vulcanization temperature is controlled between 170-180℃, the time is 5-15 minutes, and the pressure is 5-10MPa. After vulcanization, it is placed in a temperature environment of 180-200℃ for 2-4 hours and then discharged to obtain the thermally conductive and microwave-absorbing material. The nitrogen oxide-doped porous carbon was prepared using the following method: Step 1: Mix xanthan gum with a 1:1 volume ratio of ethanol and purified water solution and stir to form a homogeneous solution. Then add isonicotinic acid and catalyst to the solution. After the addition is complete, stir at room temperature for 6-8 hours. Separate the material, wash and vacuum dry to obtain the nitrogen-containing carbon precursor. Step 2: Mix nitrogen-containing carbon precursor and potassium hydroxide at a mass ratio of 1:2-4, grind evenly, place in a tube furnace, raise the temperature to 750-800℃ at a heating rate of 3-5℃ / min, under nitrogen protection throughout the process, calcine for 1-3 hours, and then discharge to obtain nitrogen-doped porous carbon. Step 3: Mix nitrogen-doped porous carbon with hydrogen peroxide solution and oxidize at 80-90℃ for 8-12 hours. Separate the material, wash and vacuum dry it to obtain nitrogen oxide-doped porous carbon.

2. The method for preparing a thermally conductive and wave-absorbing material for the housing of an electromagnetic device according to claim 1, characterized in that, The silicone rubber base material is methyl vinyl silicone rubber.

3. The method for preparing a thermally conductive and wave-absorbing material for the housing of an electromagnetic device according to claim 1, characterized in that, The epoxidized silicone rubber is prepared by epoxidizing methyl vinyl silicone rubber with 3-chloroperoxybenzoic acid as the epoxidizing agent.

4. The method for preparing a thermally conductive and wave-absorbing material for the housing of an electromagnetic device according to claim 1, characterized in that, The thermally conductive and microwave-absorbing additive is prepared using the following method: Modified boron nitride and nitrogen oxide-doped porous carbon in a mass ratio of 1:1 are mixed with purified water. Stirring is started and the mixture is mechanically stirred at 50-60℃ for 1-2 hours. After stirring is stopped and the mixture is allowed to stand for 20-40 minutes, the solid material is separated and then vacuum dried to obtain the thermally conductive and microwave-absorbing additive.

5. A method for preparing a thermally conductive and wave-absorbing material for an electromagnetic device housing according to any one of claims 1 or 4, characterized in that, The modified boron nitride was prepared using the following method: Hydroxylated boron nitride and tetrahydrofuran were mixed and ultrasonically dispersed to form a homogeneous dispersion. Nitrogen gas was introduced to purge the air. Then, 2,3-epoxypropyltrimethylammonium chloride and a phase transfer catalyst were added to the dispersion in sequence. The temperature was controlled at 60-65℃ and stirred for 4-6 hours. The solid material was separated by centrifugation, washed, and dried to obtain modified boron nitride.

6. The method for preparing a thermally conductive and wave-absorbing material for the housing of an electromagnetic device according to claim 5, characterized in that, The preparation method of the hydroxylated boron nitride is as follows: add boron nitride nanosheets to a sodium hydroxide solution with a concentration of 4-5 mol / L, stir and disperse evenly, keep in a temperature environment of 90-100℃ for 6-8 hours, and then cool down and discharge the material.

7. A method for preparing a thermally conductive and wave-absorbing material for an electromagnetic device housing according to claim 5, characterized in that, The phase transfer catalyst is any one of tetrabutylammonium bisulfate, tetrabutylammonium bromide, or tetramethylammonium bromide.

8. The method for preparing a thermally conductive and wave-absorbing material for the housing of an electromagnetic device according to claim 1, characterized in that, In step one, the catalyst is a mixture of dicyclohexylcarbodiimide and 4-dimethylaminopyridine in a mass ratio of 1:0.2-0.

4.

9. A method for preparing a thermally conductive and wave-absorbing material for an electromagnetic device housing according to claim 1, characterized in that, In step three, the volume fraction of the hydrogen peroxide solution is 20-30%.

Images