Carbon nanotube electromagnetic shielding composite material and preparation method thereof

Abstract

The invention relates to a carbon nanotube electromagnetic shielding composite material and a preparation method thereof, and belongs to the technical field of electromagnetic shielding materials. The preparation method comprises the following steps: treating a multi-walled carbon nanotube, introducing composite metal particles, treating to obtain a first mixed solution, respectively adding polyimide resin, pyrrole, an oxidant and maleic anhydride into the first mixed solution, treating to obtain a second mixed solution, and finally performing spray drying, hot press molding and cooling to obtain the carbon nanotube electromagnetic shielding composite material. An organosilane layer is formed on the surface of the multi-walled carbon nanotube, plasma treatment is carried out, the compatibility and binding force between the multi-walled carbon nanotube and organic components are improved, meanwhile, the composite metal particles, the polyimide resin, pyrrole, the oxidizing agent and maleic anhydride are added, the performance of the composite material is synergistically optimized through all the components, and the performance of the composite material is improved. And the electromagnetic shielding effectiveness of the composite material is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of electromagnetic shielding materials and relates to a carbon nanotube electromagnetic shielding composite material and a preparation method thereof. Background Art

[0002] Electromagnetic shielding refers to the use of specific materials or structures to block or attenuate the propagation of electromagnetic fields to protect electronic equipment and sensitive areas from electromagnetic interference. Electromagnetic shielding materials are the key to achieving this function. Traditional electromagnetic shielding materials include metal foil, metal mesh, etc., which are widely used in electronic communications, medical care, aviation and other fields due to their good conductivity and magnetic permeability. However, traditional metal materials are usually heavy and not suitable for portable devices, and the shielding effect of metal shielding materials is limited within certain ranges.

[0003] As a new type of nanomaterial, carbon nanotubes are considered to be an ideal choice for electromagnetic shielding materials because of their aspect ratio and good conductivity, which enables them to form an effective conductive network in a polymer matrix, thereby achieving excellent electromagnetic shielding effects. However, carbon nanotubes have poor dispersibility, making it difficult to evenly distribute them in the matrix, which may lead to unstable shielding performance. In addition, carbon nanotubes have poor compatibility in certain polymer matrices, which may affect the comprehensive performance of the material, resulting in limitations in practical applications. Summary of the invention

[0004] The purpose of the present invention is to provide a carbon nanotube electromagnetic shielding composite material and a preparation method thereof. The present invention forms an organic silane layer on the surface of multi-walled carbon nanotubes and performs plasma treatment to improve its compatibility and binding force with organic components. At the same time, composite metal particles, polyimide resin, pyrrole, oxidant and maleic anhydride are added. The components synergistically optimize the performance of the composite material and further improve the electromagnetic shielding effectiveness of the composite material.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing a carbon nanotube electromagnetic shielding composite material, the method for preparing the carbon nanotube electromagnetic shielding composite material comprising the following steps:

[0007] (1) adding multi-walled carbon nanotubes to a silane coupling agent solution, stirring, washing with deionized water, drying, and subjecting the dried product to plasma treatment to obtain treated multi-walled carbon nanotubes;

[0008] (2) adding the treated multi-walled carbon nanotubes and composite metal particles to a polyvinyl pyrrolidone solution, and mixing them with a high-speed shear mixer after ultrasonic treatment to obtain a first mixed solution;

[0009] (3) adding a polyimide resin to the first mixed solution, ultrasonically mixing, then adding pyrrole and an oxidant, stirring, then adding maleic anhydride, heating and stirring to obtain a second mixed solution;

[0010] (4) spray-drying the second mixed liquid to obtain solid composite particles, placing the solid composite particles into a mold, hot-pressing and molding, and cooling to room temperature to obtain a carbon nanotube electromagnetic shielding composite material.

[0011] Furthermore, the silane coupling agent solution in step (1) is composed of anhydrous ethanol and γ-aminopropyltriethoxysilane in a mass ratio of 8-10:0.8-1.2; and the mass ratio of the multi-walled carbon nanotubes to γ-aminopropyltriethoxysilane is 1:0.1-0.2.

[0012] Furthermore, the parameters of the stirring step in step (1) are: stirring temperature of 50-70°C, stirring speed of 100-300rmp, stirring time of 4-6h; the drying is drying in a vacuum drying oven at 80-100°C for 12-24h; the plasma treatment is passing a mixed gas of argon and nitrogen, wherein the volume ratio of argon to nitrogen is 1:3-4, the processing power is set to 50-150W, the gas flow rate is 10-20L / min, and the plasma treatment is 5-15min.

[0013] Furthermore, in step (2), the mass ratio of the treated multi-walled carbon nanotubes to the composite metal particles is 1:0.27-0.31; the composite metal particles are composed of yttrium oxide, lanthanum oxide and titanium carbide with an average particle size of 10-50 nm in a mass ratio of 1.2-1.3:0.9-1.2:1.6-1.9; and the polyvinyl pyrrolidone solution is composed of polyvinyl pyrrolidone and N,N-dimethylacetamide in a mass ratio of 0.8-1.6:150-170.

[0014] Furthermore, the parameters of the ultrasonic treatment in step (2) are: ultrasonic frequency is 50-70kHz, ultrasonic power is 250-350W, and ultrasonic time is 15-25min; the shear speed and shear time of the high-speed shear mixer are 6000-9000rmp and 20-30min, respectively.

[0015] Furthermore, in step (3), the amount of the polyimide resin added is 15-25wt% of the first mixed solution; the mass ratio of the pyrrole, oxidant and polyimide resin is 1.6-2:1.6-2:1.1-1.3; and the mass ratio of the maleic anhydride and the treated multi-walled carbon nanotubes is 0.2-0.4:1.

[0016] Furthermore, the parameters of the ultrasonic mixing in step (3) are: ultrasonic frequency of 40-60kHz, ultrasonic power of 100-200W, and ultrasonic time of 10-20min; the stirring refers to stirring at 20-24°C at a speed of 100-200rmp for 5-7h; the heating stirring refers to heating to 60-100°C at a speed of 2-8°C / min and stirring at a speed of 50-150rmp for 2-4h.

[0017] Furthermore, the parameters of the spray drying in step (4) are: inlet temperature is 120-130°C, outlet temperature is 60-80°C; the parameters of the hot pressing molding are: hot pressing pressure is 4-10MPa, hot pressing temperature is 90-110°C.

[0018] Beneficial effects of the present invention:

[0019] (1) The present invention first treats the multi-walled carbon nanotubes with a silane coupling agent solution, wherein the γ-aminopropyltriethoxysilane can form an organic silane layer on the surface of the multi-walled carbon nanotubes, thereby improving its compatibility with other organic components and avoiding agglomeration. The surface activity of the multi-walled carbon nanotubes is further improved by plasma treatment, thereby enhancing the binding force with other components. Composite metal particles are then added. The yttrium oxide and lanthanum oxide in the composite metal particles effectively absorb electromagnetic waves with their high dielectric constants, while titanium carbide reflects electromagnetic waves with its good electrical conductivity. The synergistically treated multi-walled carbon nanotubes achieve multiple absorption and reflection of electromagnetic waves, thereby improving electromagnetic shielding effectiveness. In addition, the addition of the composite metal particles can also improve the mechanical properties of the material.

[0020] (2) The polyimide resin introduced in the present invention has good heat resistance and mechanical strength, and can provide good heat resistance protection and structural support for the electromagnetic shielding composite material; on this basis, pyrrole and an oxidant are introduced, and pyrrole can undergo a polymerization reaction under the action of the oxidant to generate polypyrrole, forming a conductive network, and this conductive network is interconnected with the conductive paths of the multi-walled carbon nanotubes and the composite metal particles, further enhancing the electromagnetic shielding performance of the material; in addition, the conductive property of pyrrole can enable it to generate an induced current under the action of electromagnetic waves, interact with the electromagnetic waves, thereby consuming the energy of the electromagnetic waves or changing the propagation direction and intensity of the electromagnetic waves, further improving the electromagnetic shielding performance of the material; finally, maleic anhydride is introduced to improve the interface bonding between the components, thereby improving the overall performance of the composite material, and in addition, it can also improve the dispersibility of the multi-walled carbon nanotubes and the composite metal particles, improve the uniformity and integrity of the conductive network, thereby enhancing the electromagnetic shielding effectiveness of the material. DETAILED DESCRIPTION

[0021] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0022] The multi-walled carbon nanotubes in all the embodiments and comparative examples of the present invention were purchased directly from the market, all purchased from Jiaxing Naco New Materials Co., Ltd., with the item number HGN-1-1; the polyimide resins were purchased directly from the market, all purchased from Wuhan Lvjing Fenghua Biotechnology Co., Ltd.

[0023] Example 1

[0024] A method for preparing a carbon nanotube electromagnetic shielding composite material. The method for preparing the carbon nanotube electromagnetic shielding composite material of this embodiment comprises the following steps:

[0025] (1) adding multi-walled carbon nanotubes to a silane coupling agent solution, stirring, washing with deionized water, drying, and subjecting the dried product to plasma treatment to obtain treated multi-walled carbon nanotubes;

[0026] (2) adding the treated multi-walled carbon nanotubes and composite metal particles to a polyvinyl pyrrolidone solution, and mixing them with a high-speed shear mixer after ultrasonic treatment to obtain a first mixed solution;

[0027] (3) adding a polyimide resin to the first mixed solution, ultrasonically mixing, then adding pyrrole and an oxidant, stirring, then adding maleic anhydride, heating and stirring to obtain a second mixed solution;

[0028] (4) spray-drying the second mixed liquid to obtain solid composite particles, placing the solid composite particles into a mold, hot-pressing and molding, and cooling to room temperature to obtain a carbon nanotube electromagnetic shielding composite material.

[0029] The silane coupling agent solution in step (1) of this embodiment is composed of anhydrous ethanol and γ-aminopropyltriethoxysilane in a mass ratio of 8:0.8; the mass ratio of multi-walled carbon nanotubes and γ-aminopropyltriethoxysilane is 1:0.1.

[0030] The parameters of the stirring step in step (1) of this embodiment are: stirring temperature of 50°C, stirring speed of 100 rpm, stirring time of 4 h; drying is drying in a vacuum drying oven at 80°C for 12 h; plasma treatment is passing a mixed gas of argon and nitrogen, wherein the volume ratio of argon to nitrogen is 1:3, the treatment power is set to 50 W, the gas flow rate is 10 L / min, and the plasma treatment is performed for 5 min.

[0031] The mass ratio of the treated multi-walled carbon nanotubes and the composite metal particles in step (2) of this embodiment is 1:0.27; the composite metal particles are composed of yttrium oxide, lanthanum oxide and titanium carbide with an average particle size of 10 nm in a mass ratio of 1.2:0.9:1.6; the polyvinyl pyrrolidone solution is composed of polyvinyl pyrrolidone and N,N-dimethylacetamide in a mass ratio of 0.8:150; the ratio of the total mass of the treated multi-walled carbon nanotubes and the composite metal particles to the mass of the polyvinyl pyrrolidone solution is 1:2.

[0032] The parameters of the ultrasonic treatment in step (2) of this embodiment are: ultrasonic frequency of 50 kHz, ultrasonic power of 250 W, and ultrasonic time of 15 min; the shear speed and shear time of the high-speed shear mixer are 6000 rpm and 20 min, respectively.

[0033] The amount of polyimide resin added in step (3) of this embodiment is 15wt% of the first mixed solution; the mass ratio of pyrrole, oxidant and polyimide resin is 1.6:1.6:1.1, and the oxidant is ferric chloride; the mass ratio of maleic anhydride and treated multi-walled carbon nanotubes is 0.2:1.

[0034] The parameters of ultrasonic mixing in step (3) of this embodiment are: ultrasonic frequency is 40kHz, ultrasonic power is 100W, and ultrasonic time is 10min; stirring refers to stirring at 100rpm for 5h at 20°C; heating stirring refers to heating to 60°C at a rate of 2°C / min and stirring at 50rpm for 2h.

[0035] The parameters of spray drying in step (4) of this embodiment are: inlet temperature is 120°C, outlet temperature is 60°C; the parameters of hot pressing molding are: hot pressing pressure is 4MPa, hot pressing temperature is 90°C.

[0036] Example 2

[0037] A method for preparing a carbon nanotube electromagnetic shielding composite material. The method for preparing the carbon nanotube electromagnetic shielding composite material of this embodiment comprises the following steps:

[0038] (1) adding multi-walled carbon nanotubes to a silane coupling agent solution, stirring, washing with deionized water, drying, and subjecting the dried product to plasma treatment to obtain treated multi-walled carbon nanotubes;

[0039] (2) adding the treated multi-walled carbon nanotubes and composite metal particles to a polyvinyl pyrrolidone solution, and mixing them with a high-speed shear mixer after ultrasonic treatment to obtain a first mixed solution;

[0040] (3) adding a polyimide resin to the first mixed solution, ultrasonically mixing, then adding pyrrole and an oxidant, stirring, then adding maleic anhydride, heating and stirring to obtain a second mixed solution;

[0041] (4) spray-drying the second mixed liquid to obtain solid composite particles, placing the solid composite particles into a mold, hot-pressing and molding, and cooling to room temperature to obtain a carbon nanotube electromagnetic shielding composite material.

[0042] The silane coupling agent solution in step (1) of this embodiment is composed of anhydrous ethanol and γ-aminopropyltriethoxysilane in a mass ratio of 10:1.2; the mass ratio of multi-walled carbon nanotubes and γ-aminopropyltriethoxysilane is 1:0.2.

[0043] The parameters of the stirring step in step (1) of this embodiment are: stirring temperature of 70°C, stirring speed of 300 rpm, stirring time of 6 h; drying is drying in a vacuum drying oven at 100°C for 24 h; plasma treatment is passing a mixed gas of argon and nitrogen, wherein the volume ratio of argon to nitrogen is 1:4, the treatment power is set to 150 W, the gas flow rate is 20 L / min, and the plasma treatment is performed for 15 min.

[0044] The mass ratio of the treated multi-walled carbon nanotubes and the composite metal particles in step (2) of this embodiment is 1:0.31; the composite metal particles are composed of yttrium oxide, lanthanum oxide and titanium carbide with an average particle size of 50 nm in a mass ratio of 1.3:1.2:1.9; the polyvinyl pyrrolidone solution is composed of polyvinyl pyrrolidone and N,N-dimethylacetamide in a mass ratio of 1.6:170; the ratio of the total mass of the treated multi-walled carbon nanotubes and the composite metal particles to the mass of the polyvinyl pyrrolidone solution is 1:2.

[0045] The parameters of the ultrasonic treatment in step (2) of this embodiment are: ultrasonic frequency of 70 kHz, ultrasonic power of 350 W, and ultrasonic time of 25 min; the shear speed and shear time of the high-speed shear mixer are 9000 rpm and 30 min, respectively.

[0046] The amount of polyimide resin added in step (3) of this embodiment is 25wt% of the first mixed solution; the mass ratio of pyrrole, oxidant and polyimide resin is 2:2:1.3, and the oxidant is ferric chloride; the mass ratio of maleic anhydride and treated multi-walled carbon nanotubes is 0.4:1.

[0047] The parameters of ultrasonic mixing in step (3) of this embodiment are: ultrasonic frequency is 60kHz, ultrasonic power is 200W, and ultrasonic time is 20min; stirring refers to stirring at 200rpm for 7h at 24°C; heating stirring refers to heating to 100°C at a rate of 8°C / min and stirring at 150rpm for 2-4h.

[0048] The parameters of spray drying in step (4) of this embodiment are: inlet temperature is 130°C, outlet temperature is 80°C; the parameters of hot pressing molding are: hot pressing pressure is 10MPa, hot pressing temperature is 110°C.

[0049] Example 3

[0050] A method for preparing a carbon nanotube electromagnetic shielding composite material. The method for preparing the carbon nanotube electromagnetic shielding composite material of this embodiment comprises the following steps:

[0051] (1) adding multi-walled carbon nanotubes to a silane coupling agent solution, stirring, washing with deionized water, drying, and subjecting the dried product to plasma treatment to obtain treated multi-walled carbon nanotubes;

[0052] (2) adding the treated multi-walled carbon nanotubes and composite metal particles to a polyvinyl pyrrolidone solution, and mixing them with a high-speed shear mixer after ultrasonic treatment to obtain a first mixed solution;

[0053] (3) adding a polyimide resin to the first mixed solution, ultrasonically mixing, then adding pyrrole and an oxidant, stirring, then adding maleic anhydride, heating and stirring to obtain a second mixed solution;

[0054] (4) spray-drying the second mixed liquid to obtain solid composite particles, placing the solid composite particles into a mold, hot-pressing and molding, and cooling to room temperature to obtain a carbon nanotube electromagnetic shielding composite material.

[0055] The silane coupling agent solution in step (1) of this embodiment is composed of anhydrous ethanol and γ-aminopropyltriethoxysilane in a mass ratio of 9:1; the mass ratio of multi-walled carbon nanotubes to γ-aminopropyltriethoxysilane is 1:0.15.

[0056] The parameters of the stirring step in step (1) of this embodiment are: stirring temperature of 60°C, stirring speed of 200 rpm, stirring time of 5 h; drying is drying in a vacuum drying oven at 80-100°C for 18 h; plasma treatment is passing a mixed gas of argon and nitrogen, wherein the volume ratio of argon to nitrogen is 1:3.5, the treatment power is set to 100 W, the gas flow rate is 15 L / min, and the plasma treatment is performed for 10 min.

[0057] The mass ratio of the treated multi-walled carbon nanotubes and the composite metal particles in step (2) of this embodiment is 1:0.29; the composite metal particles are composed of yttrium oxide, lanthanum oxide and titanium carbide with an average particle size of 30 nm in a mass ratio of 1.25:1.05:1.75; the polyvinyl pyrrolidone solution is composed of polyvinyl pyrrolidone and N,N-dimethylacetamide in a mass ratio of 1.2:160; the ratio of the total mass of the treated multi-walled carbon nanotubes and the composite metal particles to the mass of the polyvinyl pyrrolidone solution is 1:2.

[0058] The parameters of the ultrasonic treatment in step (2) of this embodiment are: ultrasonic frequency of 60 kHz, ultrasonic power of 300 W, and ultrasonic time of 20 min; the shear speed and shear time of the high-speed shear mixer are 7500 rpm and 25 min, respectively.

[0059] The amount of polyimide resin added in step (3) of this embodiment is 20wt% of the first mixed solution; the mass ratio of pyrrole, oxidant and polyimide resin is 1.8:1.8:1.2, and the oxidant is ferric chloride; the mass ratio of maleic anhydride and treated multi-walled carbon nanotubes is 0.3:1.

[0060] The parameters of ultrasonic mixing in step (3) of this embodiment are: ultrasonic frequency is 50kHz, ultrasonic power is 150W, and ultrasonic time is 15min; stirring refers to stirring at 150rpm for 6h at 22°C; heating stirring refers to heating to 80°C at a rate of 5°C / min and stirring at 100rpm for 3h.

[0061] The parameters of spray drying in step (4) of this embodiment are: inlet temperature is 125°C, outlet temperature is 70°C; the parameters of hot pressing molding are: hot pressing pressure is 7MPa, hot pressing temperature is 100°C.

[0062] Comparative Example 1

[0063] On the basis of Example 3, keeping other conditions the same, step (1) in the method for preparing the carbon nanotube electromagnetic shielding composite material is changed to:

[0064] The multi-walled carbon nanotubes are added into the silane coupling agent solution, stirred, washed with deionized water, and dried to obtain the treated multi-walled carbon nanotubes.

[0065] Comparative Example 2

[0066] On the basis of Example 3, the volume ratio of argon and nitrogen introduced during plasma treatment was changed to 1:2, and other conditions were consistent with Example 3.

[0067] Comparative Example 3

[0068] On the basis of Example 3, keeping other conditions the same, step (1) in the method for preparing the carbon nanotube electromagnetic shielding composite material is changed to:

[0069] The multi-walled carbon nanotubes are subjected to plasma treatment to obtain treated multi-walled carbon nanotubes.

[0070] Comparative Example 4

[0071] On the basis of Example 3, the polyvinyl pyrrolidone in the polyvinyl pyrrolidone solution was removed, and other conditions were consistent with those in Example 3.

[0072] Comparative Example 5

[0073] On the basis of Example 3, yttrium oxide in the composite metal particles was removed and replaced with an equal weight of lanthanum oxide, and other conditions were consistent with Example 3.

[0074] Comparative Example 6

[0075] On the basis of Example 3, the lanthanum oxide in the composite metal particles was removed and replaced with an equal weight of titanium carbide. Other conditions were the same as those in Example 3.

[0076] Comparative Example 7

[0077] On the basis of Example 3, titanium carbide in the composite metal particles was removed and replaced with an equal weight of yttrium oxide. Other conditions were consistent with Example 3.

[0078] Comparative Example 8

[0079] On the basis of Example 3, keeping other conditions the same, step (3) in the method for preparing the carbon nanotube electromagnetic shielding composite material is changed to:

[0080] The polyimide resin is added into the first mixed liquid, and after ultrasonic mixing, pyrrole, an oxidant and maleic anhydride are added, and the mixture is heated and stirred to obtain a second mixed liquid.

[0081] The carbon nanotube electromagnetic shielding composite materials prepared in Example 3 and Comparative Examples 1-8 were used as samples, the sample thickness was controlled at 2±0.1 mm, and the electromagnetic shielding effectiveness of the samples in the frequency range of 8-12 GHz was tested using an Agilent N5230A vector network analyzer. The test results are shown in Table 1 below.

[0082] Table 1

[0083] Electromagnetic shielding effectiveness / dB Example 3 53 Comparative Example 1 42 Comparative Example 2 44 Comparative Example 3 45 Comparative Example 4 49 Comparative Example 5 47 Comparative Example 6 48 Comparative Example 7 47 Comparative Example 8 41

[0084] As shown in Table 1, the carbon nanotube electromagnetic shielding composite material prepared by the present invention has good electromagnetic shielding effectiveness. Comparative Example 1 removes the plasma treatment, which may cause the binding force between the multi-walled carbon nanotubes and other components to decrease, thereby reducing the electromagnetic shielding effectiveness. Comparative Example 2 changes the volume ratio of argon and nitrogen in the plasma treatment. Argon has a higher ionization energy and may cause excessive etching of the multi-walled carbon nanotubes, affecting the performance of the multi-walled carbon nanotubes. Comparative Example 3 removes the silane coupling agent solution treatment step, which may also affect the compatibility between the components and thus affect the electromagnetic shielding effectiveness. Energy; Comparative Example 4 removes the polyvinyl pyrrolidone in the polyvinyl pyrrolidone solution, which may affect the dispersibility of the composite metal particles in the solution and the combination with the multi-walled carbon nanotubes, thereby affecting the electromagnetic shielding effectiveness; Comparative Examples 5-7 replace a certain component in the composite metal particles. Compared with the synergistic effect of the components in the composite metal particles of the present invention, the electromagnetic shielding effectiveness is weakened; Comparative Example 8 removes the step of preliminary low-temperature treatment of pyrrole and oxidant, and directly mixes them with other components at high temperature. Too high temperature may cause excessive polymerization of pyrrole, thereby affecting the electromagnetic shielding effectiveness of the subsequent composite material.

[0085] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any indirect modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a carbon nanotube electromagnetic shielding composite material, characterized in that: The method for preparing the carbon nanotube electromagnetic shielding composite material comprises the following steps: (1) adding multi-walled carbon nanotubes to a silane coupling agent solution, stirring, washing with deionized water, drying, and subjecting the dried product to plasma treatment to obtain treated multi-walled carbon nanotubes; (2) adding the treated multi-walled carbon nanotubes and composite metal particles to a polyvinyl pyrrolidone solution, and mixing them with a high-speed shear mixer after ultrasonic treatment to obtain a first mixed solution; (3) adding a polyimide resin to the first mixed solution, ultrasonically mixing, then adding pyrrole and an oxidant, stirring, then adding maleic anhydride, heating and stirring to obtain a second mixed solution; (4) spray-drying the second mixed liquid to obtain solid composite particles, placing the solid composite particles into a mold, hot-pressing and molding, and cooling to room temperature to obtain a carbon nanotube electromagnetic shielding composite material.

2. The method for preparing a carbon nanotube electromagnetic shielding composite material according to claim 1, characterized in that: The silane coupling agent solution in step (1) is composed of anhydrous ethanol and γ-aminopropyltriethoxysilane in a mass ratio of 8-10:0.8-1.2; the mass ratio of the multi-walled carbon nanotubes to γ-aminopropyltriethoxysilane is 1:0.1-0.

2.

3. The method for preparing a carbon nanotube electromagnetic shielding composite material according to claim 1, characterized in that: The parameters of the stirring step in step (1) are: stirring temperature of 50-70°C, stirring speed of 100-300rmp, stirring time of 4-6h; the drying is drying in a vacuum drying oven at 80-100°C for 12-24h; the plasma treatment is passing a mixed gas of argon and nitrogen, wherein the volume ratio of argon to nitrogen is 1:3-4, the treatment power is set to 50-150W, the gas flow rate is 10-20L / min, and the plasma treatment is 5-15min.

4. The method for preparing a carbon nanotube electromagnetic shielding composite material according to claim 1, characterized in that: In step (2), the mass ratio of the treated multi-walled carbon nanotubes to the composite metal particles is 1:0.27-0.31; the composite metal particles are composed of yttrium oxide, lanthanum oxide and titanium carbide with an average particle size of 10-50 nm in a mass ratio of 1.2-1.3:0.9-1.2:1.6-1.9; and the polyvinyl pyrrolidone solution is composed of polyvinyl pyrrolidone and N,N-dimethylacetamide in a mass ratio of 0.8-1.6:150-170.

5. The method for preparing a carbon nanotube electromagnetic shielding composite material according to claim 1, characterized in that: The parameters of the ultrasonic treatment in step (2) are: ultrasonic frequency of 50-70kHz, ultrasonic power of 250-350W, and ultrasonic time of 15-25min; the shear speed and shear time of the high-speed shear mixer are 6000-9000rmp and 20-30min, respectively.

6. The method for preparing a carbon nanotube electromagnetic shielding composite material according to claim 1, characterized in that: In step (3), the amount of the polyimide resin added is 15-25wt% of the first mixed solution; the mass ratio of the pyrrole, oxidant and polyimide resin is 1.6-2:1.6-2:1.1-1.3; the mass ratio of the maleic anhydride and the treated multi-walled carbon nanotubes is 0.2-0.4:

1.

7. The method for preparing a carbon nanotube electromagnetic shielding composite material according to claim 1, characterized in that: The parameters of the ultrasonic mixing in step (3) are: ultrasonic frequency of 40-60kHz, ultrasonic power of 100-200W, and ultrasonic time of 10-20min; the stirring refers to stirring at 20-24°C at a speed of 100-200rmp for 5-7h; the heating stirring refers to heating to 60-100°C at a speed of 2-8°C / min and stirring at a speed of 50-150rmp for 2-4h.

8. The method for preparing a carbon nanotube electromagnetic shielding composite material according to claim 1, characterized in that: The parameters of the spray drying in step (4) are: inlet temperature is 120-130°C, outlet temperature is 60-80°C; the parameters of the hot pressing molding are: hot pressing pressure is 4-10MPa, and hot pressing temperature is 90-110°C.