A highly conductive MXene-based electromagnetic shielding composite film and a preparation method thereof

Abstract

The application discloses a kind of high-conductivity MXene-based electromagnetic shielding composite films and preparation method thereof, belong to new material technical field.The preparation method includes the following steps: using in-situ HF etching method to prepare MXene dispersion liquid;With deionized water as solvent, silver nitrate solution is prepared by dissolving silver nitrate;The silver nitrate aqueous solution is added to MXene dispersion liquid, and Ag@MXene film is obtained by vacuum filtration method.The method uses silver ion in silver nitrate as oxidant to make it and titanium element in MXene occur redox reaction to generate silver particles, so as to prop up MXene sheet layer and reduce the resistance caused by adhesion between sheet layers and increase the conductive path in MXene, so as to increase the conductivity of MXene;The composite film not only has excellent conductivity, electromagnetic shielding performance and is easy to form processing;The conductivity of the composite film can reach 3120S / cm, and the electromagnetic shielding performance can reach 68.5dB.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new materials, and particularly relates to a high-conductivity MXene-based electromagnetic shielding composite film and a preparation method thereof. BACKGROUND

[0002] With the development of wireless communication technology and the continuous growth of small electronic devices, serious electromagnetic interference problems have been caused, including data loss, information leakage, etc. Strong electromagnetic field radiation can not only directly affect the operation of equipment but also affect human health. The fifth generation (5G) wireless device has high integration and precision, which requires electromagnetic shielding materials to have the advantages of easy molding processing, light weight, small thickness, etc. However, high-efficiency electromagnetic shielding materials have excellent electrical conductivity, which is not possessed by the commonly seen carbon-based materials, such as graphene and carbon nanotubes. Therefore, it is necessary to find a material with high conductivity as an electromagnetic shielding material to solve such problems.

[0003] In recent years, Ti3C2T x MXene, as a new type of two-dimensional material, has attracted extensive attention. It not only has excellent electromagnetic shielding performance in the X band (8.2-12.4 GHz), but also has good electrical conductivity due to its metallic properties. Vacuum filtration is a commonly used method for preparing thin films. Although the MXene thin film prepared by vacuum filtration has excellent electrical conductivity, which provides good electromagnetic shielding performance, the arrangement between the layers increases the resistance. The electrical conductivity of pure MXene thin film is about 2902 S / cm. Therefore, enhancing the electrical conductivity of MXene thin film is of great significance for the in-depth research and development of MXene thin film. Although MXene thin film solves the problems of traditional electromagnetic shielding materials, such as large density, easy corrosion, easy falling off and difficult molding processing, MXene is essentially a two-dimensional layered material, and the layers are stacked with each other, which increases the resistance to a certain extent and reduces the electrical conductivity. Therefore, the Ti 2+ and Ag + in silver nitrate are used to carry out a redox reaction, so that Ag + is reduced to silver particles, thereby supporting the MXene layers and effectively increasing the conductive path, so as to increase the electrical conductivity. SUMMARY

[0004] To solve the problem of MXene sheet layer accumulation in the prior art which affects the conductivity to some extent, the application provides a high-conductivity MXene-based electromagnetic shielding composite film and a preparation method thereof, the method adopts silver nitrate as a filler, silver ions are introduced into the silver nitrate, and a redox reaction occurs between the silver ions and Ti elements on the surface of MXene sheet layers to form silver particles, so that the distance between the MXene sheet layers can be effectively increased and the conductive path between the sheet layers can be increased; the composite film has excellent conductivity, electromagnetic shielding performance and easy forming processing; the conductivity of the composite film is 3120 S / cm, and the electromagnetic shielding performance is 68.5 dB.

[0005] In order to achieve the above-mentioned purpose, the application adopts the following technical solutions to achieve the above-mentioned purpose:

[0006] The application provides a preparation method of a high-conductivity MXene-based electromagnetic shielding composite film, including the following steps:

[0007] S1: preparing a MXene dispersion liquid;

[0008] S2: preparing a silver nitrate aqueous solution;

[0009] S3: adding the silver nitrate aqueous solution into the MXene dispersion liquid to perform a redox reaction to obtain an AgNPs / MXene dispersion liquid, and then adopting a vacuum-assisted filtration method to obtain the high-conductivity MXene-based electromagnetic shielding composite film.

[0010] Further, in S1, the process of preparing the MXene dispersion liquid is as follows:

[0011] Titanium aluminum carbide is used as a raw material, and an in-situ HF etching method is adopted to selectively etch the aluminum layer in the titanium aluminum carbide; the obtained product is washed by centrifugation with concentrated hydrochloric acid and deionized water to remove impurities, and then a MXene dispersion liquid is obtained by hand peeling.

[0012] Further, the etching solution of the in-situ HF etching method is a compounded solution of hydrochloric acid and lithium fluoride.

[0013] Further, the etching time is 24h-72h.

[0014] Further, in S2, the process of preparing the silver nitrate aqueous solution is as follows: deionized water is used to dissolve silver nitrate solid to prepare a silver nitrate aqueous solution.

[0015] Further, in S1, the concentration of the silver nitrate aqueous solution is 2.5mg / mL-25mg / mL.

[0016] Further, in S3, the reaction time of the redox reaction is 20-40min.

[0017] A high-conductivity MXene-based electromagnetic shielding composite film prepared by any of the preparation methods.

[0018] Further, when the thickness of the high-conductivity MXene-based electromagnetic shielding composite film is 17-20 μm, the highest conductivity of the high-conductivity MXene-based electromagnetic shielding composite film is 3120 S / cm, and the highest electromagnetic shielding performance is 68.5 dB.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] The preparation method of the high-conductivity MXene-based electromagnetic shielding composite film provided by the present application uses MXene as a matrix, and the MXene is a dispersion liquid prepared by a selective etching method from a MAX phase. The MXene contains a large amount of titanium elements and carbon elements, and the layered structure formed by the two can not only provide excellent conductivity but also has abundant surface end groups for better modification. The purpose of introducing Ag in the Ag@MXene composite film is to increase the distance between the MXene film layers and increase the conductive path between the layers. The main reason is that the silver ions in silver nitrate are reduced to silver particles by the redox reaction with the Ti elements on the MXene layers, thereby increasing the distance between the layers and providing more conductive paths. The method has the advantages of simplicity, high efficiency, low equipment requirement, wide application range, environmental friendliness and low cost, and can effectively avoid the problem of low conductivity of MXene-based electromagnetic shielding films. The obtained composite film can be used in the field of electromagnetic shielding and has high potential application value in the field of electromagnetic shielding.

[0021] The high-conductivity MXene-based electromagnetic shielding composite film provided by the present application uses a selective etching method to prepare a MXene dispersion liquid as a subsequent matrix, and uses silver nitrate as an oxidizing agent. Silver ions can be reduced to silver particles by Ti elements on the MXene layers to support the MXene layers and increase the conductive path, thereby improving the conductivity. The high-conductivity MXene-based electromagnetic shielding composite film has high conductivity and is easy to process and shape. The conductivity of the composite film can reach 3120 S / cm, and the electromagnetic shielding performance can reach 68.5 dB. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Figure is the electromagnetic shielding performance diagram of the MXene and Ag@MXene composite film of the present application;

[0023] Figure 2 Figure is the SEM diagram of the Ag@MXene composite film of the present application;

[0024] Figure 3The conductivity map of the MXene, Ag@MXene composite film of the present application. DETAILED DESCRIPTION

[0025] To enable persons skilled in the art to understand the features and effects of the present application, the following is a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific words used herein have their usual meanings to those skilled in the art of the present application, and in the event of conflict, the definitions in the present specification shall prevail.

[0026] Theories or mechanisms described and disclosed herein, whether correct or not, should not be considered limiting the scope of the present application, i.e., the present application can be practiced without regard to any particular theory or mechanism.

[0027] Herein, all features defined in the form of numerical ranges or percentage ranges such as values, amounts, contents and concentrations are for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered to have encompassed and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0028] Herein, unless otherwise specified, "comprise", "include", "contain", "have" or similar words encompass the meaning of "consist of" and "consist essentially of", for example, "A comprises a" encompasses the meaning of "A comprises a and other" and "A comprises only a".

[0029] Herein, for the sake of brevity, all possible combinations of the technical features in each embodiment or example are not described. Therefore, as long as the combinations of the technical features do not contradict each other, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope of the present specification.

[0030] The present application provides a high-conductivity MXene-based electromagnetic shielding composite film and a preparation method thereof.

[0031] The present application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application. Furthermore, it should be understood that after reading the content taught by the present application, those skilled in the art can make various modifications or changes to the present application, and these equivalent forms also fall within the scope of the appended claims of the present application.

[0032] The following examples use apparatus and equipment that are conventional in the art. The experimental methods in the following examples, unless otherwise specified, are generally conducted under conventional conditions, or under conditions recommended by the manufacturer. The following examples use various raw materials, unless otherwise specified, all of which are conventional commercially available products, and the specifications thereof are conventional in the art. In the specification of the present application and in the following examples, unless otherwise specified, "%" means "percent by weight", "parts" means "parts by weight", and the ratio means "ratio by weight".

[0033] The present application provides a preparation method of a high-conductivity MXene-based electromagnetic shielding composite film, specifically comprising the following steps:

[0034] S1, etching titanium aluminum carbide in hydrochloric acid / lithium fluoride to obtain MXene.

[0035] Preferably, the centrifuge tube and the magnet are treated with anhydrous ethanol by ultrasonic treatment to remove surface impurities, and are dried for standby. The weighed hydrochloric acid, lithium fluoride and titanium aluminum carbide are added to the centrifuge tube with the magnet, and the reaction is carried out at 40°C for 24h-72h. The obtained product is washed with concentrated hydrochloric acid and deionized water to remove impurities generated in the reaction, and finally MXene dispersion is obtained by repeated concentration and centrifugation through hand shaking.

[0036] The preparation of the MXene refers to the acid etching method, and the in-situ HF etching method is further selected to selectively etch the aluminum layer in the titanium aluminum carbide with a hydrochloric acid / lithium fluoride solution as the etching liquid.

[0037] The ratio of 9M hydrochloric acid to lithium fluoride in the etching liquid is (20-40mL):(1-2g);

[0038] The mass ratio of Ti3AlC2 to lithium fluoride is 1:1;

[0039] The etching time is 24h-72h.

[0040] S2, dissolving silver nitrate solid in deionized water to obtain an aqueous silver nitrate solution.

[0041] Preferably, the beaker, magnet and the like are treated with anhydrous ethanol by ultrasonic treatment to remove surface impurities, and are dried for standby. 1g of silver nitrate solid is added to 20mL of deionized water, and a uniform solution is formed by stirring at room temperature, i.e. 50mg / mL silver nitrate solution, and then the obtained solution is diluted to form silver nitrate aqueous solutions with concentration gradients of 2.5mg / mL, 5mg / mL, 7.5mg / mL, 10mg / mL, 12.5mg / mL, 15mg / mL, 17.5mg / mL, 20mg / mL, 22.5mg / mL and 25mg / mL.

[0042] S3, adding silver nitrate aqueous solution in MXene dispersion liquid, 1 mL of silver nitrate aqueous solution is added to 50 mg MXene dispersion liquid, the concentration of the silver nitrate aqueous solution is 2.5 mg / mL-25 mg / mL, and a redox reaction is carried out for 20-40 min to obtain AgNPs / MXene dispersion liquid, and a Ag@MXene composite film is prepared by a vacuum-assisted suction filtration method.

[0043] Preferably, a beaker, a sand core funnel and the like are treated by ultrasonic treatment with anhydrous ethanol to remove surface impurities, and are dried for standby use. A weighed silver nitrate aqueous solution is added to a quantitative MXene dispersion liquid, and is poured into a sand core funnel to be taken out after film formation.

[0044] The mold can be any container, preferably a beaker, a polytetrafluoroethylene mold or other glass products and the like.

[0045] The method uses silver ions in silver nitrate as an oxidizing agent to cause a redox reaction with titanium elements in MXene to generate silver particles, thereby supporting MXene sheets to reduce the resistance caused by the adhesion between the sheets and increase the conductive path in MXene, so as to increase the conductivity of MXene; the composite film not only has excellent conductive performance and electromagnetic shielding performance, but also is easy to process; the conductivity of the composite film can reach 3120 S / cm, and the electromagnetic shielding performance can reach 68.5 dB.

[0046] The technical solutions of the present application are described in detail in combination with the embodiments and the accompanying drawings:

[0047] Example 1

[0048] Preparation of the composite MXene film: first, 1 g of lithium fluoride, 20 mL of 9 mol / L hydrochloric acid and 1 g of titanium aluminum carbide are added to a centrifuge tube with a magnet, and the reaction is carried out at 40℃ for 48 h. The obtained product is washed with concentrated hydrochloric acid and deionized water to remove impurities generated in the reaction, and finally a large-size MXene dispersion liquid is obtained by hand peeling; 1 g of silver nitrate solid is added to 20 mL of deionized water, and stirred at room temperature to form a uniform solution, 1 mL of 2.5 mg / mL silver nitrate aqueous solution is added to 50 mg of MXene dispersion liquid, and a film is formed by vacuum suction filtration.

[0049] Example 2

[0050] Preparation of composite MXene film: First, 1 g of lithium fluoride, 20 mL of 9 mol / L hydrochloric acid, and 1 g of titanium aluminum carbide were added to a centrifuge tube with a magnet, and the mixture was reacted at 40 °C for 48 h. The resulting product was washed with concentrated hydrochloric acid and deionized water to remove impurities produced during the reaction, and finally a large-size MXene dispersion liquid was obtained by hand shaking. 1 g of silver nitrate solid was added to 20 mL of deionized water, and the mixture was stirred at room temperature to form a uniform solution. 1 mL of 5 mg / mL silver nitrate aqueous solution was added to 50 mg of MXene dispersion liquid, and the mixture was filtered by vacuum suction to form a film.

[0051] Example 3

[0052] Preparation of composite MXene film: First, 1 g of lithium fluoride, 20 mL of 9 mol / L hydrochloric acid, and 1 g of titanium aluminum carbide were added to a centrifuge tube with a magnet, and the mixture was reacted at 40 °C for 48 h. The resulting product was washed with concentrated hydrochloric acid and deionized water to remove impurities produced during the reaction, and finally a large-size MXene dispersion liquid was obtained by hand shaking. 1 g of silver nitrate solid was added to 20 mL of deionized water, and the mixture was stirred at room temperature to form a uniform solution. 1 mL of 5 mg / mL silver nitrate aqueous solution was added to 50 mg of MXene dispersion liquid, and the mixture was filtered by vacuum suction to form a film.

[0053] Example 4

[0054] Preparation of composite MXene film: First, 1 g of lithium fluoride, 20 mL of 9 mol / L hydrochloric acid, and 1 g of titanium aluminum carbide were added to a centrifuge tube with a magnet, and the mixture was reacted at 40 °C for 48 h. The resulting product was washed with concentrated hydrochloric acid and deionized water to remove impurities produced during the reaction, and finally a large-size MXene dispersion liquid was obtained by hand shaking. 1 g of silver nitrate solid was added to 20 mL of deionized water, and the mixture was stirred at room temperature to form a uniform solution. 1 mL of 5 mg / mL silver nitrate aqueous solution was added to 50 mg of MXene dispersion liquid, and the mixture was filtered by vacuum suction to form a film.

[0055] Example 5

[0056] Preparation of composite MXene film: First, 1 g of lithium fluoride, 20 mL of 9 mol / L hydrochloric acid, and 1 g of titanium aluminum carbide were added to a centrifuge tube with a magnet, and the mixture was reacted at 40 °C for 48 h. The resulting product was washed with concentrated hydrochloric acid and deionized water to remove impurities produced during the reaction, and finally a large-size MXene dispersion liquid was obtained by hand shaking. 1 g of silver nitrate solid was added to 20 mL of deionized water, and the mixture was stirred at room temperature to form a uniform solution. 1 mL of 5 mg / mL silver nitrate aqueous solution was added to 50 mg of MXene dispersion liquid, and the mixture was filtered by vacuum suction to form a film.

[0057] Example 6

[0058] Preparation of composite MXene film: First, 2 g of lithium fluoride, 40 mL of 9 mol / L hydrochloric acid, and 2 g of titanium aluminum carbide were added to a centrifuge tube with a magnet, and the mixture was reacted at 40 °C for 24 h. The resulting product was washed with concentrated hydrochloric acid and deionized water to remove impurities generated during the reaction, and finally a large-size MXene dispersion liquid was obtained by hand-shaking peeling; 1 g of silver nitrate solid was added to 20 mL of deionized water, and stirred at room temperature to form a uniform solution. 1 mL of 15 mg / mL silver nitrate aqueous solution was added to 50 mg of MXene dispersion liquid, and the film was formed by vacuum filtration.

[0059] Example 7

[0060] Preparation of composite MXene film: First, 2 g of lithium fluoride, 40 mL of 9 mol / L hydrochloric acid, and 2 g of titanium aluminum carbide were added to a centrifuge tube with a magnet, and the mixture was reacted at 40 °C for 72 h. The resulting product was washed with concentrated hydrochloric acid and deionized water to remove impurities generated during the reaction, and finally a large-size MXene dispersion liquid was obtained by hand-shaking peeling; 1 g of silver nitrate solid was added to 20 mL of deionized water, and stirred at room temperature to form a uniform solution. 1 mL of 17.5 mg / mL silver nitrate aqueous solution was added to 50 mg of MXene dispersion liquid, and the film was formed by vacuum filtration.

[0061] Example 8

[0062] Preparation of composite MXene film: First, 2 g of lithium fluoride, 40 mL of 9 mol / L hydrochloric acid, and 2 g of titanium aluminum carbide were added to a centrifuge tube with a magnet, and the mixture was reacted at 40 °C for 72 h. The resulting product was washed with concentrated hydrochloric acid and deionized water to remove impurities generated during the reaction, and finally a large-size MXene dispersion liquid was obtained by hand-shaking peeling; 1 g of silver nitrate solid was added to 20 mL of deionized water, and stirred at room temperature to form a uniform solution. 1 mL of 20 mg / mL silver nitrate aqueous solution was added to 50 mg of MXene dispersion liquid, and the film was formed by vacuum filtration.

[0063] Example 9

[0064] Preparation of composite MXene films: First, 2g of weighed lithium fluoride, 40mL of 9mol / L hydrochloric acid, and 2g of titanium aluminum carbide were added to a centrifuge tube equipped with a magnetic stir bar, and the reaction was carried out at 40℃ for 72h. The resulting product was washed with concentrated hydrochloric acid and deionized water to remove impurities generated during the reaction. Finally, the product was manually peeled off to obtain a large-sized MXene dispersion. 1g of silver nitrate solid was added to 20mL of deionized water and stirred at room temperature to form a homogeneous solution. 1mL of 22.5mg / mL silver nitrate aqueous solution was added to 50mg of MXene dispersion, and the film was formed by vacuum filtration.

[0065] Example 10

[0066] Preparation of composite MXene films: First, 2g of weighed lithium fluoride, 40mL of 9mol / L hydrochloric acid, and 2g of titanium aluminum carbide were added to a centrifuge tube equipped with a magnetic stir bar and reacted at 40℃ for 36h. The resulting product was washed with concentrated hydrochloric acid and deionized water to remove impurities generated during the reaction. Finally, the product was manually peeled off to obtain a large-sized MXene dispersion. 1g of silver nitrate solid was added to 20mL of deionized water and stirred at room temperature to form a homogeneous solution. 1mL of 25mg / mL silver nitrate aqueous solution was added to 50mg of MXene dispersion, and the film was formed by vacuum filtration.

[0067] like Figure 1 As shown, the electromagnetic shielding performance of the composite film in the X-band (8.2–12.4 GHz) was characterized by a vector network analyzer. Since the silver ions in silver nitrate react with the titanium elements on the MXene sheet to form silver particles, the MXene sheet is supported and the conductive path is effectively increased, thereby increasing the conductivity and thus increasing the electromagnetic shielding performance of the composite film.

[0068] like Figure 2 As shown in Figures (a) and (b), scanning the cross-section of the composite film using cold field emission scanning electron microscopy revealed that the redox reaction between silver ions and titanium did not alter the MXene sheet structure. In fact, silver ions were effectively generated, supporting the MXene sheets and increasing the conductive pathways.

[0069] like Figure 3 As shown, the resistivity of the composite film was tested using a four-probe tester, and its conductivity was calculated. The conductivity of the composite film was improved compared to that of the pure MXene film, indicating that the addition of silver ions significantly improved the conductivity.

[0070] The MXene-based electromagnetic shielding composite film prepared by the above method, such as Figure 1 The electromagnetic shielding test diagram is shown. Figure 3The conductivity of the composite film can reach 3120 S / cm and the electromagnetic shielding performance can reach 68.5 dB, as shown in a conductivity test diagram.

[0071] The high-conductivity MXene-based electromagnetic shielding composite film has MXene prepared by a selective etching method as a base material. The large specific surface area of the MXene is conducive to the construction of a conductive network. Silver nitrate is used as a filler. Silver ions can undergo an oxidation-reduction reaction with titanium elements on the MXene sheet layer, so that the silver ions are reduced to silver particles to prop up the MXene sheet layer and increase the conductive path, thereby increasing the conductivity and the conductive performance of the high-conductivity MXene-based electromagnetic shielding composite film.

[0072] The above content only illustrates the technical idea of the present application and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the claims of the present application.

Claims

1. A method for preparing a high-conductivity MXene-based electromagnetic shielding composite film, characterized in that, The method comprises the following steps: S1: preparing a MXene dispersion liquid; S2: preparing an aqueous silver nitrate solution; S3: adding the aqueous silver nitrate solution into the MXene dispersion liquid to perform a redox reaction to obtain an AgNPs / MXene dispersion liquid, and then adopting a vacuum-assisted filtration method to prepare a high-conductivity MXene-based electromagnetic shielding composite film; The concentration of the aqueous silver nitrate solution is 2.5 mg / mL to 25 mg / mL. When the thickness of the high-conductivity MXene-based electromagnetic shielding composite film is 17 to 20 microns, the highest conductivity of the high-conductivity MXene-based electromagnetic shielding composite film is 3120 S / cm, and the highest electromagnetic shielding performance is 68.5 dB. 2.The method of claim 1, wherein, In the S1, the process of preparing the MXene dispersion liquid is as follows: Titanium aluminum carbide is used as a raw material, and an in-situ HF etching method is adopted to selectively etch the aluminum layer in the titanium aluminum carbide; the obtained product is centrifugally washed with concentrated hydrochloric acid and deionized water to remove impurities, and then a MXene dispersion liquid is obtained through manual peeling. 3.The method of claim 2, wherein the method further comprises the step of mixing the MXene and the polymer solution. The etching solution of the in-situ HF etching method is a compounded solution of hydrochloric acid and lithium fluoride. 4.The method of claim 2, wherein the method is characterized by, The etching time is 24 hours to 72 hours. 5.The method of claim 1, wherein, In the S2, the process of preparing the aqueous silver nitrate solution is as follows: deionized water is used to dissolve solid silver nitrate to prepare an aqueous silver nitrate solution. 6.The method of claim 1, wherein, In the S3, the reaction time of the redox reaction is 20 to 40 minutes.

7. A high-conductivity MXene-based electromagnetic shielding composite film prepared by the preparation method in any one of claims 1 to 6.

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