A catalytic graphitization method for preparing a magnetic graphene film for electromagnetic shielding

Abstract

The application belongs to the technical field of carbon nanomaterials, and particularly relates to a catalytic graphitization method for preparing a magnetic graphene film for electromagnetic shielding. The method is to dope magnetic nanoparticles in graphene oxide dispersion in situ, then spin-coat into a film, and finally perform catalytic graphitization treatment under inert gas protection to obtain a magnetic graphene film. The magnetic nanoparticles play a dual role of catalyst and wave absorber. On the one hand, the graphene oxide film is catalytically graphitized at a temperature lower than the conventional graphitization temperature; on the other hand, the electromagnetic wave can be absorbed by magnetic loss, thereby improving the electromagnetic shielding performance of the graphene film. The method greatly reduces the graphitization temperature of the graphene film, simplifies the requirements for the production equipment, realizes energy saving and cost reduction, and the prepared magnetic graphene film has an absorption-based electromagnetic shielding performance and can be used to solve the electromagnetic compatibility problem of high-integration electronic products.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of carbon nanomaterials, and particularly relates to a catalytic graphitization preparation method of a magnetic graphene film for electromagnetic shielding. BACKGROUND

[0002] The rapid development of advanced electronic devices and wireless communication technologies has caused an electromagnetic interference problem that cannot be ignored, which not only seriously interferes with the normal operation of surrounding electronic components, reduces information security and communication quality, but also endangers human health. With the rapid increase in the number of new-generation highly integrated, high-power and high-frequency electronic devices led by the 5G era, the problem of electromagnetic interference is becoming increasingly prominent. Developing high-performance electromagnetic shielding materials is an important means to suppress electromagnetic interference and is also an indispensable component to ensure the normal operation of electronic devices. Electronic products that are constantly miniaturized, lightweight, flexible and intelligent have higher requirements for the shielding performance, density, thickness and flexibility of electromagnetic shielding materials. Traditional metal shielding materials have been difficult to meet the development trend of shielding materials due to problems such as high density, easy corrosion and poor toughness, and it is imperative to develop new electromagnetic shielding materials.

[0003] Graphene is a two-dimensional nanomaterial with a honeycomb-like structure composed of carbon six-membered rings. Each carbon atom is sp 2 hybridized, contributes one remaining electron on the p orbital to form a large π bond, and the π electron can move freely, giving graphene good electrical conductivity. At the same time, graphene has a very high specific surface area and a unique layered structure, and electromagnetic waves are lost by multiple reflections between graphene layers. More importantly, graphene films have excellent properties such as light weight, ultra-thinness and free bending, and have unique advantages in solving the electromagnetic interference of high-integration electronic devices. The Zhai Wentao team of the Ningbo Institute of Materials Technology and Engineering of the Chinese Academy of Sciences prepared an oxidized graphene film by a direct evaporation method, and obtained a graphene film by high-temperature thermal reduction at 2000℃. The thickness of the film is only 8.4μm, and the shielding effectiveness in the X band is about 20dB.

[0004] However, the electromagnetic shielding effectiveness of graphene films is mainly reflected, which will inevitably cause secondary radiation pollution. In addition, the preparation of high-performance graphene films requires long-time high-temperature (2000-3000℃) graphitization treatment to repair the structural defects of the precursor, which will consume a large amount of energy and time, shorten the service life of the equipment, and increase the preparation cost. SUMMARY

[0005] In view of the above technical problems, the application provides a catalytic graphitization preparation method of a magnetic graphene film for electromagnetic shielding, which can improve the wave absorption performance while reducing the graphitization temperature, thereby reducing the preparation cost of the graphene film.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is:

[0007] A catalytic graphitization method for preparing a magnetic graphene film for electromagnetic shielding, comprising the following steps:

[0008] S1, disperse graphene oxide in distilled water to form a graphene oxide dispersion liquid with a certain concentration; add magnetic catalyst particles to the graphene oxide dispersion liquid, stir uniformly, and obtain a black suspension;

[0009] S2, the black suspension obtained in S1 is subjected to film forming treatment to obtain a magnetic graphene oxide film;

[0010] S3, the magnetic graphene oxide film obtained in S2 is placed in a graphitization furnace, heated and subjected to catalytic graphitization treatment under the protection of inert gas to obtain a magnetic graphene film.

[0011] In S1, the concentration of graphene oxide is 2-10 mg / mL.

[0012] In S1, the magnetic catalyst includes any one of Fe, Co, Ni and their magnetic oxides.

[0013] In S1, the mass of the magnetic catalyst is 1-5 times that of graphene oxide, and the particle size is not more than 500 nm.

[0014] In S2, the film forming treatment refers to pouring the black suspension obtained in S1 into a rotary film coating machine, forming a film by high-speed centrifugation, and obtaining a magnetic graphene oxide film after freeze-drying.

[0015] The centrifugal rate is 500-3000 rpm.

[0016] In S3, the heating rate is 2-10 ℃ / min, the heating temperature is 800-1500 ℃, and the holding time is 1-2 h.

[0017] In S1, the stirring is uniform by mechanical method.

[0018] Compared with the prior art, the present application has the beneficial effects that:

[0019] The magnetic nanoparticles play a dual role of catalyst and wave absorber, on the one hand, the graphene oxide film is catalytically graphitized at a lower temperature than the conventional graphitization temperature, and on the other hand, the electromagnetic waves can be absorbed by magnetic loss, thereby improving the electromagnetic shielding performance of the graphene film.

[0020] The magnetic graphene film is composed of two-dimensional graphene nanosheets and zero-dimensional magnetic nanoparticles, and the magnetic nanoparticles cause magnetic loss to electromagnetic waves through hysteresis effect, eddy current effect, natural resonance and the like, so that a large amount of electromagnetic energy is converted into heat energy and dissipated, thereby achieving the effect of absorbing electromagnetic waves and greatly reducing secondary radiation pollution.

[0021] The preparation method adopted by the application greatly reduces the graphitization temperature of the graphene film, simplifies the requirements for the production equipment, realizes energy saving and consumption reduction and cost reduction, and the prepared magnetic graphene film has excellent electromagnetic shielding performance and can be used to solve the electromagnetic compatibility problem of high-integration electronic products. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a physical photo of the magnetic graphene film of the application;

[0023] Figure 2 is an SEM photo of the magnetic graphene film of the application;

[0024] Figure 3 is a shielding efficiency curve of the magnetic graphene film of the application in the X wave band, wherein SE total represents the total electromagnetic shielding efficiency, SE A represents the absorption loss, and SE R represents the reflection loss. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0026] A catalytic graphitization preparation method of a magnetic graphene film for electromagnetic shielding comprises the following steps:

[0027] S1: disperse graphene oxide in distilled water to form a graphene oxide dispersion liquid with a certain concentration; add a certain mass of magnetic catalyst particles to the graphene oxide dispersion liquid, uniformly mechanically stir, and obtain a black suspension.

[0028] S2: pour the black suspension obtained in S1 into a rotary film coater, form a film through high-speed centrifugation, and obtain a magnetic graphene oxide film after freeze-drying.

[0029] S3: place the magnetic graphene oxide film obtained in S2 in a graphitization furnace, heat to a certain temperature under the protection of inert gas for catalytic graphitization treatment, and obtain a magnetic graphene film (as shown in Figure 1 ).

[0030] Further, in the S1 process, the concentration of graphene oxide is 2-10 mg / mL; the magnetic catalyst includes but is not limited to Fe, Co, Ni and their magnetic oxides, and the mass of the magnetic catalyst is 1-5 times that of the graphene oxide, and the particle size is not more than 500 nm.

[0031] Further, in the S2 process, the centrifugal rate is 500-3000 rpm, and the listed film forming method is the optimal film forming method for graphene oxide, and other film forming methods should be included within the scope of the present application without departing from the purpose of the present application.

[0032] Further, in the S3 process, the heating rate is 2-10 ℃ / min, the heating temperature is 800-1500 ℃, and the holding time is 1-2 h.

[0033] In order to obtain a graphene film with high conductivity, the existing preparation technology is to perform high-temperature graphitization treatment on the graphene film, and the graphitization temperature is not less than 2000 ℃, which consumes a large amount of energy and time, increases the production cost of the graphene film. The magnetic graphene film preparation technology disclosed by the present application introduces magnetic nanoparticles as a catalyst for catalyzing graphitization in the graphene oxide film, which greatly reduces the graphitization temperature of the graphene oxide film (800-1500 ℃), saves a large amount of energy and time, simplifies the requirements for equipment, and reduces the preparation cost.

[0034] Although the existing graphene film has a certain electromagnetic shielding efficiency, its shielding mechanism is mainly reflection, and the electromagnetic waves reflected back to the free space by the graphene film will cause secondary electromagnetic pollution to the surrounding environment. The magnetic graphene film disclosed by the present application is composed of two-dimensional graphene nanosheets and zero-dimensional magnetic nanoparticles, and the magnetic nanoparticles cause magnetic loss to the electromagnetic waves through hysteresis effect, eddy current effect, natural resonance and other ways, so that a large amount of electromagnetic energy is converted into heat energy and dissipated, thereby playing an effect of absorbing electromagnetic waves and greatly reducing secondary radiation pollution.

[0035] Example 1

[0036] S1: Disperse graphene oxide in distilled water to form a graphene oxide dispersion liquid with a concentration of 2 mg / mL; add Fe nanoparticles to the graphene oxide dispersion liquid, the mass ratio of Fe nanoparticles to graphene oxide is 2:1, mechanically stir uniformly to obtain a black suspension.

[0037] S2: Pour the black suspension obtained in S1 into a rotary film coater, centrifuge at a high speed to form a film, the rotation speed is 500 rpm, and a magnetic graphene oxide film is obtained after freeze-drying;

[0038] S3 places the magnetic graphene oxide film obtained by S2 into a graphitization furnace, heats to 800℃ at a heating rate of 2℃ / min under the protection of argon gas, and graphitizes for 2h to obtain a magnetic graphene film;

[0039] Example 2

[0040] S1 disperses graphene oxide in distilled water to form a graphene oxide dispersion liquid with a concentration of 5mg / mL; Co nanoparticles are added to the graphene oxide dispersion liquid, the mass ratio of Co nanoparticles to graphene oxide is 3:1, and the mixture is uniformly stirred by mechanical stirring to obtain a black suspension.

[0041] S2 pours the black suspension obtained in S1 into a rotary film coater, centrifuges at a high speed to form a film, the rotation speed is 1000rpm, and a magnetic graphene oxide film is obtained after freeze-drying;

[0042] S3 places the magnetic graphene oxide film obtained by S2 into a graphitization furnace, heats to 800℃ at a heating rate of 2℃ / min under the protection of argon gas, and graphitizes for 2h to obtain a magnetic graphene film;

[0043] Example 3

[0044] S1 disperses graphene oxide in distilled water to form a graphene oxide dispersion liquid with a concentration of 7mg / mL; Ni nanoparticles are added to the graphene oxide dispersion liquid, the mass ratio of Ni nanoparticles to graphene oxide is 5:1, and the mixture is uniformly stirred by mechanical stirring to obtain a black suspension.

[0045] S2 pours the black suspension obtained in S1 into a rotary film coater, centrifuges at a high speed to form a film, the rotation speed is 2000rpm, and a magnetic graphene oxide film is obtained after freeze-drying;

[0046] S3 places the magnetic graphene oxide film obtained by S2 into a graphitization furnace, heats to 800℃ at a heating rate of 2℃ / min under the protection of argon gas, and graphitizes for 2h to obtain a magnetic graphene film;

[0047] Example 4

[0048] S1 disperses graphene oxide in distilled water to form a graphene oxide dispersion liquid with a concentration of 10mg / mL; Fe3O4 nanoparticles are added to the graphene oxide dispersion liquid, the mass ratio of Fe3O4 nanoparticles to graphene oxide is 1:1, and the mixture is uniformly stirred by mechanical stirring to obtain a black suspension.

[0049] S2 pours the black suspension obtained in S1 into a rotary film coater, centrifuges at a high speed to form a film, the rotation speed is 3000rpm, and a magnetic graphene oxide film is obtained after freeze-drying;

[0050] S3 places the magnetic graphene oxide film obtained by S2 into a graphitization furnace, heats to 1500 DEG C at a heating rate of 10 DEG C / min under protection of argon gas, and is graphitized for 2 h to obtain a magnetic graphene film;

[0051] The test results of the above examples are as follows:

[0052] Table 1 Test results of electromagnetic shielding effectiveness of sample X in X band

[0053]

[0054]

[0055] The above only describes the preferred embodiments of the present application in detail, but the present application is not limited to the above examples, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present application, and all the changes shall be included in the protection scope of the present application.

Claims

1. A method for preparing a magnetic graphene film for electromagnetic shielding by catalytic graphitization, characterized by, The method comprises the following steps: S1, dispersing graphene oxide in distilled water to form a graphene oxide dispersion liquid with a certain concentration; adding magnetic nano-catalyst particles to the graphene oxide dispersion liquid, stirring uniformly to obtain a black suspension; S2, performing film forming treatment on the black suspension obtained in S1 to obtain a magnetic graphene oxide film; S3, placing the magnetic graphene oxide film obtained in S2 in a graphitization furnace, heating and performing catalytic graphitization treatment under the protection of inert gas to obtain a magnetic graphene film; In S1, the magnetic nano-catalyst includes any one of Fe, Co, Ni and their magnetic oxides; The magnetic graphene film is composed of two-dimensional graphene nanosheets and zero-dimensional magnetic nano-catalyst particles, and the magnetic nano-catalyst particles cause magnetic loss to electromagnetic waves through hysteresis effect, eddy current effect and natural resonance mode, so that a large amount of electromagnetic energy is converted into heat energy and dissipated, thereby achieving the effect of absorbing electromagnetic waves and greatly reducing secondary radiation pollution.

2. The method according to claim 1, wherein the method is characterized by, In S1, the concentration of graphene oxide is 2-10 mg / mL.

3. The method according to claim 1, wherein the method is characterized by, In S1, the mass of the magnetic nano-catalyst is 1-5 times that of the graphene oxide, and the particle size is not more than 500 nm.

4. The method according to claim 1, wherein the method is characterized by, In S2, the film forming treatment refers to pouring the black suspension obtained in S1 into a rotary film coater, forming a film through high-speed centrifugation, and obtaining a magnetic graphene oxide film after freeze-drying.

5. The method according to claim 4, wherein the catalytic graphitization is performed by using a catalytic graphitization method. The centrifugal rate is 500-3000 rpm.

6. The method according to claim 1, wherein the catalytic graphitization is performed by using a catalytic graphitization method. In S3, the heating rate is 2-10 ℃ / min, the heating temperature is 800-1500 ℃, and the holding time is 1-2 h.

7. The method according to claim 1, wherein the method is characterized by, In S1, the stirring is performed in a mechanical manner.

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