Preparation method of electromagnetic shielding film and electromagnetic shielding film

Abstract

The invention discloses a preparation method of an electromagnetic shielding film and the electromagnetic shielding film. The method comprises the following steps: adding cobalt salt and nickel salt into a first solvent to obtain a first mixed solution; adding a 2-methylimidazole solution into the first mixed solution, standing and centrifuging to obtain a first precipitate; and drying the first precipitate to obtain first powder. Polyacrylonitrile fibers and the first powder are dissolved in dimethylformamide, and a spinning solution and a first dispersion solution are obtained; adding the first dispersion liquid into a spinning solution, and stirring to obtain a first emulsion; treating the first emulsion by an electrostatic spinning method to obtain a carbon nanofiber membrane precursor; and performing high-temperature carbonization treatment on the carbon nanofiber membrane precursor to obtain the Co / Ni carbon nanofiber membrane. The Ti < 3 > C < 2 > T < x > dispersion liquid is subjected to suction filtration through a vacuum suction filtration method with the Co / Ni carbon fiber membrane as a filtering medium, and the Ti < 3 > C < 2 > T < x >-Co / Ni carbon fiber membrane is obtained. And carrying out drying treatment on the Ti < 3 > C < 2 > T < x >-Co / Ni carbon fiber film to obtain the electromagnetic shielding film. The electromagnetic shielding film is excellent in wave absorbing performance, and secondary pollution of electromagnetic waves is reduced.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of electromagnetic wave shielding, and in particular to a preparation method of an electromagnetic shielding film and the electromagnetic shielding film. BACKGROUND

[0002] With the rapid development of modern electronic equipment, electromagnetic interference (EMI) problems are increasingly serious, which has become a key factor affecting the reliability of electronic equipment. In particular, electronic equipment in cold environments such as aerospace and wearable heating equipment. Such equipment not only needs efficient EMI shielding materials, but also requires these materials to have multiple functions such as light weight, thinness and flexibility.

[0003] MXene, MXene is a two-dimensional material with a large specific surface area and excellent electrical conductivity, and has been widely concerned and applied in the field of electromagnetic interference shielding. However, MXene as a shielding material can cause serious impedance mismatch and easily cause secondary radiation of electromagnetic waves, resulting in poor wave absorption performance of the wave absorption material. SUMMARY

[0004] The application provides a preparation method of an electromagnetic shielding film and the electromagnetic shielding film, aiming to improve the wave absorption performance of the wave absorption material.

[0005] In a first aspect, the application provides a preparation method of an electromagnetic shielding film, which comprises adding a cobalt salt and a nickel salt into a first solvent to obtain a first mixed solution. A 2-methylimidazole solution is provided, and the 2-methylimidazole solution is added into the first mixed solution, centrifuged after standing, to obtain a first precipitate; the first precipitate is subjected to drying treatment to obtain a first powder. Acrylonitrile fibers are dissolved in dimethylformamide to obtain a spinning solution; the first powder is dispersed in dimethylformamide to obtain a first dispersion liquid; the first dispersion liquid is added into the spinning solution and stirred to obtain a first emulsion. The first emulsion is subjected to electrospinning treatment to obtain a carbon nanofiber film precursor. The carbon nanofiber film precursor is subjected to high-temperature carbonization treatment to obtain a Co / Ni carbon nanofiber film. A Ti3C2T x dispersion liquid with a concentration of 5wt% to 8wt% is provided, the Co / Ni carbon fiber film is used as a filter medium, the Ti3C2T x dispersion liquid is subjected to vacuum suction filtration by using the Co / Ni carbon fiber film as a filter medium, to obtain a Ti3C2T x -Co / Ni carbon fiber film. The Ti3C2T x -Co / Ni carbon fiber film is subjected to drying treatment to obtain an electromagnetic shielding film.

[0006] In some embodiments, the Ti3C2T xThe dispersion liquid comprises Ti3C2T x powder, the Ti3C2T x powder is dissolved in a second solvent and placed in an ice water bath for ultrasonic treatment for 10-30 min to obtain Ti3C2T x dispersion liquid. The second solvent comprises at least one of water, N-methyl pyrrolidone, dimethyl sulfoxide or ethanol.

[0007] In some embodiments, the 2-methyl imidazole solution is added to the first mixed solution, and after standing, centrifugation is performed to obtain a first precipitate, and the precipitate is dried to obtain a first powder. The 2-methyl imidazole solution is added to the first mixed solution, and after standing at a temperature of 23-26°C for 18-24 h, centrifugation is performed at a speed of 1800-2000 rpm / min to obtain the first precipitate. The first precipitate is washed with ethanol, and the washed first precipitate is placed in a vacuum environment at a temperature of 50-80°C for drying for 3-5 h to obtain the first powder.

[0008] In some embodiments, before the first emulsion is treated by an electrospinning method to obtain a carbon nanofiber membrane precursor, the first emulsion is added to an electrospinning device, and a required voltage is 18-21 kV. The electrospinning device comprises a spinning needle and a collector, and the distance between the spinning needle and the collector is 25-30 cm. The electrospinning device further comprises a spinning roller, and the diameter of the spinning roller is 5-8 cm, the length of the spinning roller is 15-25 cm, and the rotation speed of the spinning roller is 8-15 rpm / min. The first emulsion is extruded through the spinning needle to form nanofilaments, and the nanofilaments are collected on the collector. After drying the nanofilaments, a carbon nanofiber membrane precursor is obtained.

[0009] In some embodiments, the carbon nanofiber membrane precursor is subjected to high-temperature carbonization to obtain a Co / Ni carbon fiber membrane, which comprises preheating the carbon nanofiber membrane precursor in an environment at a temperature of 220-250°C for 2-3 h. A tube furnace is provided, and the tube furnace comprises an inert gas. The tube furnace is heated to a temperature of 800-900°C at a speed of 5°C / min, and after carbonization treatment of the carbon fiber membrane precursor for 3-4 h, the Co / Ni carbon fiber membrane is obtained after cooling.

[0010] In some embodiments, the cobalt salt comprises at least one of cobalt chloride, cobalt sulfate, cobalt nitrate and cobalt carbonate; and the nickel salt comprises at least one of nickel sulfate, nickel chloride and nickel nitrate.

[0011] In some embodiments, the first solvent comprises at least one of methanol, ethanol, acetone, deionized water.

[0012] In some embodiments, the providing the 2-methylimidazole solution comprises providing 2-methylimidazole, ultrasonic mixing the 2-methylimidazole into a second solvent to obtain the 2-methylimidazole solution. The second solvent comprises at least one of methanol, ethanol, acetone, deionized water.

[0013] In some embodiments, the concentration of the spinning solution is 12wt% to 14wt%, and the concentration of the first dispersion solution is 3wt% to 5wt%.

[0014] In a second aspect, the embodiments of the present application further provide an electromagnetic shielding film prepared by the preparation method of the electromagnetic shielding film according to any one of the first aspect.

[0015] Different from the prior art, the embodiments of the present application provide a preparation method of an electromagnetic shielding film. The method comprises adding a cobalt salt and a nickel salt into a first solvent to obtain a first mixed solution. A 2-methylimidazole solution is provided, and the 2-methylimidazole solution is added into the first mixed solution, and after standing, centrifugation is performed to obtain a first precipitate; the first precipitate is subjected to drying treatment to obtain a first powder. Polyacrylonitrile fibers are dissolved in dimethylformamide to obtain a spinning solution; the first powder is dispersed in dimethylformamide to obtain a first dispersion solution; the first dispersion solution is added into the spinning solution and stirred to obtain a first emulsion. The first emulsion is subjected to electrospinning treatment to obtain a carbon nanofiber membrane precursor. The carbon nanofiber membrane precursor is subjected to high-temperature carbonization treatment to obtain a Co / Ni carbon nanofiber membrane. A Ti3C2T x dispersion solution with a concentration of 5wt% to 8wt% is provided, the Co / Ni carbon nanofiber membrane is used as a filter medium, the Ti3C2T x dispersion solution is subjected to vacuum suction filtration by using the Co / Ni carbon nanofiber membrane as the filter medium to obtain a Ti3C2T x -Co / Ni carbon nanofiber membrane. The Ti3C2T x -Co / Ni carbon nanofiber membrane is subjected to drying treatment to obtain an electromagnetic shielding film. The electromagnetic shielding film cooperates with magnetic loss, dielectric loss and electric conduction loss to enhance the electromagnetic wave absorption efficiency. The Co / Ni carbon nanofiber membrane layer and the Ti3C2T x nanosheet layer synergistically act to make the electromagnetic wave realize the process of absorption, reflection and re-absorption in the electromagnetic shielding film, prolong the propagation path of the electromagnetic wave in the electromagnetic shielding film, increase the interaction time and frequency of the electromagnetic wave with the Co / Ni carbon nanofiber membrane layer, and be conducive to fully attenuating and absorbing the electromagnetic wave, thereby reducing the secondary pollution of the electromagnetic wave. The Co / Ni carbon nanofiber membrane layer and the Ti3C2T x nanosheet layer form a complete conductor, and the current can pass through the Ti3C2T xThe conductive network efficiently converts electrical energy into heat energy.

[0016] Additional aspects and advantages of embodiments of the present application will be described in the specification, which accomplishes partial part of the objectives, technical solutions, and superiorities of the embodiments of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0017] One or more embodiments are illustrated by way of example in the drawings in which like reference numerals indicate similar elements, and as such, continuities of descriptions are not repeated unless a particular process is described several times herein. It is to be appreciated that certain embodiments of the present application are not limited by that shown in drawings.

[0018] Figure 1 Flow chart of a method for preparing some electromagnetic shielding films provided by embodiments of the present application; Figure 2 Structure schematic diagram of some electromagnetic shielding films provided by embodiments of the present application; Figure 3 Microstructure schematic diagram of some Co / Ni carbon fiber film layers provided by embodiments of the present application; Figure 4 Microstructure schematic diagram of some Ti3C2T x nanosheet layers provided by embodiments of the present application. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions, and superiorities of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Various modifications are possible for the embodiments of the present application, and the general principles defined herein can be implemented in other implementations without departing from the scope of the present application.

[0020] In the present application, the phrase “embodiments” means that the specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily mean that all the embodiments refer to the same embodiment, nor is it independent or alternative to other embodiments.

[0021] In the description of the embodiments of the present application, the technical terms “first”, “second”, and the like are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of “plurality” is two or more, unless otherwise specifically limited.

[0022] In the description of the embodiments of the present application, the term "and / or" is merely an association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents an "or" relationship between the front and rear associated objects.

[0023] The technical features involved in the different embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0024] In a first aspect, the present application provides a preparation method of an electromagnetic shielding film, please refer to Figure 1 The preparation method comprises the following steps: Step S1: cobalt salt and nickel salt are added into a first solvent to obtain a first mixed solution.

[0025] The cobalt salt and the nickel salt serve as a metal ion source of the electromagnetic shielding film, which can provide Co 2+ and Ni 2+ , which are main elements of functional nanoparticles or carbides and oxides.

[0026] In some embodiments, the cobalt salt includes at least one of cobalt chloride, cobalt sulfate, cobalt nitrate, and cobalt carbonate. The nickel salt includes at least one of nickel sulfate, nickel chloride, and nickel nitrate.

[0027] The first solvent is used to dissolve the cobalt salt and the nickel salt to form a uniform metal ion solution, which creates conditions for subsequent reaction with ligands.

[0028] In some embodiments, the first solvent includes at least one of methanol, ethanol, acetone, and deionized water. Preferably, the first solvent is methanol and / or ethanol.

[0029] Step S2: a 2-methylimidazole solution is provided, the 2-methylimidazole solution is added into the first mixed solution, and after standing, centrifugation is performed to obtain a first precipitate; the first precipitate is subjected to drying treatment to obtain a first powder.

[0030] 2-methylimidazole is an organic ligand molecule, and the nitrogen-containing heterocycle thereof can be combined with Co 2+ and Ni 2+ through coordination bonds to form stable metal-organic frameworks (MOFs). Metal-organic frameworks are a kind of crystalline porous materials with periodic network structure, which have both rigidity of inorganic materials and flexibility of organic materials. The regular pore structure of metal-organic frameworks can limit the agglomeration of metal ions and reduce the metal accumulation phenomenon in the carbonization process.

[0031] The 2-methylimidazole solution is added into the first mixed solution, and Co 2+ ions and Ni 2+The ions reacted fully with 2-methylimidazole, and a pure first precipitate was separated. The first powder obtained after drying was CoNi-MOFs powder.

[0032] In some embodiments, a 2-methylimidazole solution is added to a first mixture, allowed to stand, and then centrifuged to obtain a first precipitate. The precipitate is then dried to obtain a first powder. This process includes adding a 2-methylimidazole solution to a first mixture, allowing it to stand at 23°C to 26°C for 18 to 24 hours, and then centrifuging at 1800 rpm to 2000 rpm to obtain the first precipitate. The first precipitate is then washed with ethanol, and the washed first precipitate is dried in a vacuum environment at 50°C to 80°C for 3 to 5 hours to obtain the first powder.

[0033] In some embodiments, providing a 2-methylimidazole solution includes providing 2-methylimidazole, adding 2-methylimidazole to a second solvent and ultrasonically mixing to obtain a 2-methylimidazole solution; the second solvent includes at least one of methanol, ethanol, acetone, and deionized water.

[0034] Step S3: Polyacrylonitrile fiber is dissolved in dimethylformamide to obtain a spinning solution; the first powder is dispersed in dimethylformamide to obtain a first dispersion; the first dispersion is added to the spinning solution and stirred to obtain a first emulsion.

[0035] Polyacrylonitrile (PAN) is a precursor to carbon fiber, possessing excellent spinnability. The cyano groups in its molecular structure undergo cyclization and carbonization during high-temperature carbonization, forming carbon fibers with a conjugated structure. Carbon fibers form the structural framework of materials, exhibiting high strength, supporting the overall structure, and possessing a certain degree of flexibility. Carbon fibers also possess high electrical and thermal conductivity; the conductive mesh formed by carbon fibers can absorb electromagnetic waves through dielectric loss and serve as a heat dissipation pathway, accelerating heat transfer.

[0036] Dimethylformamide (DMF) can dissolve polyacrylonitrile to form a spinning solution and can also disperse CoNi-MOFs powder, so that the metal-organic framework is uniformly mixed into the polyacrylonitrile system and the aggregation of metal-organic framework is reduced.

[0037] In some embodiments, the concentration of the spinning solution is 12wt% to 14wt%, which ensures that the extruded filaments are continuous and uniform, and also maintain a certain tensile strength and good flexibility. The concentration of the first dispersion is 3wt% to 5wt%, which ensures that the first dispersion and the spinning solution form a stable suspension emulsion after mixing, ensuring that Co and Ni particles are uniformly distributed in the carbon nanofiber membrane and reducing the agglomeration of the first powder particles.

[0038] If the concentration of the spinning solution is too low, the polyacrylonitrile molecular chains in dimethylformamide will not be sufficiently entangled, resulting in low viscosity of the spinning solution. After extrusion, the fibers are prone to breakage due to insufficient surface tension, making it impossible to form continuous filaments. Furthermore, a low concentration will lead to excessively fine fiber diameters, making the fibers brittle after carbonization and resulting in insufficient tensile strength of the membrane. Conversely, if the concentration of the spinning solution is too high, the viscosity will increase sharply, making the spinning needles prone to clogging. The filaments are also prone to agglomeration due to excessive molecular chain entanglement, leading to uneven distribution of nanofibers on the collector, reduced inter-fiber porosity, and decreased membrane flexibility.

[0039] When the concentration of the first dispersion is too low, the interparticle spacing of the first powder in the dispersion is too large. After mixing with the spinning solution, the concentration difference easily leads to localized sparse distribution, resulting in insufficient Co and Ni particle content in the carbon nanofiber membrane and reducing the magnetic permeability of the film. When the concentration of the first dispersion is too high, the van der Waals forces between the first powder particles are enhanced, making agglomeration more likely. This results in particle-free regions and particle-agglomerated regions in the subsequent carbon nanofiber membrane, causing significant fluctuations in the electromagnetic shielding effectiveness of the electromagnetic shielding film.

[0040] Step S4: The first emulsion is treated by electrospinning to obtain a carbon nanofiber membrane precursor.

[0041] The carbon fiber membrane precursor formed by electrospinning has nanofibers with high specific surface area, which can fix the dispersion state of metal-organic frameworks, restrict the migration of metal-organic frameworks, and make the carbonized metal particles uniformly distributed.

[0042] In some embodiments, a carbon fiber membrane precursor is obtained by electrospinning a first emulsion. This includes adding the first emulsion to an electrospinning apparatus with a voltage of 18 kV to 21 kV; the electrospinning apparatus includes a spinning needle and a collector, with the distance between the spinning needle and the collector being 25 cm to 30 cm; the electrospinning apparatus also includes a spinning roller with a diameter of 5 cm to 8 cm, a length of 15 cm to 25 cm, and a rotational speed of 8 rpm / min to 15 rpm / min. The first emulsion is extruded through the spinning needle to form nanofibers, which are then collected in the collector and dried to obtain the carbon fiber membrane precursor.

[0043] Step S5: Perform high-temperature carbonization treatment on the carbon nanofiber membrane precursor to obtain Co / Ni carbon nanofiber membrane.

[0044] During the high-temperature carbonization process of carbon nanofiber membrane precursors, polyacrylonitrile undergoes dehydrogenation, cyclization, and carbonization reactions to form carbon fibers. Carbon fibers possess a continuous conductive and thermally conductive network, serving as the primary carrier for the material's heat dissipation performance. Furthermore, carbon fibers can generate dielectric losses through electronic and interfacial polarization, aiding in the absorption of electromagnetic waves. CoNi-MOFs decompose at high temperatures, with the metal-organic framework pyrolyzing into a nitrogen-doped carbon skeleton. Nitrogen doping can introduce defect polarization, enhancing dielectric loss and optimizing impedance matching. 2+ Ions, Ni 2+ The ions are reduced to Co and Ni nanoparticles, which are uniformly dispersed in the gaps or on the surface of the carbon fibers. Both Co and Ni nanoparticles have strong magnetic loss capabilities and can absorb electromagnetic waves by inducing magnetic loss.

[0045] In some embodiments, a carbon nanofiber membrane precursor is subjected to high-temperature carbonization to obtain a Co / Ni carbon fiber membrane. This includes preheating the carbon nanofiber membrane precursor at a temperature of 220°C to 250°C for 2 to 3 hours in a tube furnace containing an inert gas; the tube furnace is heated to 800°C to 900°C at a rate of 5°C / min, and the carbon fiber membrane precursor is carbonized for 3 to 4 hours, followed by cooling to obtain the Co / Ni carbon fiber membrane. The inert gas includes at least one of helium, argon, and nitrogen.

[0046] Step S6: Provide Ti3C2T at a concentration of 5 wt% to 8 wt%. x The dispersion was filtered using a Co / Ni carbon fiber membrane as the filter medium, and the Ti3C2T dispersion was filtered by vacuum filtration. x The dispersion was filtered to obtain Ti3C2T x -Co / Ni carbon fiber membrane.

[0047] Ti3C2T x MXene is a two-dimensional layered transition metal carbide with unique electrical, optical, and mechanical properties, including high electrical conductivity and a large specific surface area. In this designation, "Ti" represents titanium, "C" represents carbon, and "T" represents titanium. x "" indicates functional groups on the surface of the material, which are typically -OH (hydroxyl), -F (fluorine), or -O (oxygen), etc. As an electromagnetic wave absorbing material, Ti3C2T x Electromagnetic waves can be attenuated through methods such as conductive loss, multiple reflections, or polarization loss.

[0048] In some embodiments, Ti3C2T is provided x The dispersion contains 20 mg to 30 mg of Ti3C2T x Powder, Ti3C2T xThe powder was dissolved in a second solvent and sonicated in an ice-water bath for 10 to 30 minutes to obtain Ti3C2T. x The dispersion. The second solvent includes at least one of water, N-methylpyrrolidone, dimethyl sulfoxide, or ethanol.

[0049] During vacuum filtration, Ti3C2T x Nanosheets are trapped by the Co / Ni carbon fiber membrane because the Co / Ni carbon fiber membrane has a porous network structure, resulting in Ti3C2T x Nanosheets not only adhere to the surface of the Co / Ni carbon fiber film, but also fill the pores within the film, along with Ti3C2T x As the amount of dispersion added increases, Ti3C2T x Nanosheets accumulate on the surface of the Co / Ni carbon fiber film, forming Ti3C2T. x Nanosheets were used to obtain Ti3C2T. x -Co / Ni carbon fiber membrane.

[0050] Step S7: For Ti3C2T x -Co / Ni carbon fiber films are dried to obtain electromagnetic shielding films. For example, Ti3C2T x - The Co / Ni carbon fiber membrane is dried in an oven at a temperature of 60℃ to 80℃ for 2 to 3 hours to obtain the dried electromagnetic shielding membrane.

[0051] Please refer to Figure 2 The electromagnetic shielding film 10 has a Co / Ni carbon fiber film layer 11 and a Ti3C2T layer. x The nanosheet layer 12 and the Co / Ni carbon fiber film layer 11 possess low electrical conductivity and a porous structure, resulting in low impedance, allowing more electromagnetic waves to penetrate into the interior of the electromagnetic shielding film. Combined with... Figure 3 and Figure 4 The Co / Ni carbon fiber film 11 contains Co nanoparticles 111 and Ni nanoparticles 112. Incoming electromagnetic waves are partially absorbed and converted into heat due to the magnetic losses of Co and Ni in this layer and the relatively weak dielectric losses. The remaining electromagnetic waves reach Ti3C2T. x Nanosheet 12 will combine with Ti3C2T x When the nanosheet 121 encounters significant impedance, most of the electromagnetic waves are reflected back to the Co / Ni carbon fiber film 11. During reflection, the remaining electromagnetic wave energy is rapidly converted into heat energy through strong conductive losses. xThe electromagnetic waves reflected back from the nanosheet layer 12 will pass through the Co / Ni carbon fiber film layer 11 again, resulting in magnetic and dielectric losses once more. This process prolongs the propagation path of the electromagnetic waves within the electromagnetic shielding film, increasing the interaction time and frequency between the electromagnetic waves and the Co / Ni carbon fiber film layer 11, which is beneficial for sufficiently attenuating and absorbing the electromagnetic waves. Ti3C2T x The nanosheets 12 form a continuous, dense, and highly conductive network, while the Co / Ni carbon fiber film 11 provides auxiliary conductive pathways, making the entire electromagnetic shielding film a complete conductor. When a voltage is applied across the electromagnetic shielding film, current can efficiently flow through the Ti3C2T film. x The conductive network of nanosheet layer 12 rapidly generates Joule heating, and the heating is uniform. In particular, the electromagnetic shielding film prepared in the embodiments of this application can be used in complex environments such as outdoors and at low temperatures to improve the problem of low ambient temperature causing performance degradation of electronic devices.

[0052] This application provides a method for preparing an electromagnetic shielding film. The method includes adding cobalt salt and nickel salt to a first solvent to obtain a first mixture. A 2-methylimidazole solution is provided and added to the first mixture. After standing, the mixture is centrifuged to obtain a first precipitate. The first precipitate is dried to obtain a first powder. Polyacrylonitrile fibers are dissolved in dimethylformamide to obtain a spinning solution. The first powder is dispersed in dimethylformamide to obtain a first dispersion. The first dispersion is added to the spinning solution and stirred to obtain a first emulsion. The first emulsion is treated by electrospinning to obtain a carbon nanofiber membrane precursor. The carbon nanofiber membrane precursor is subjected to high-temperature carbonization to obtain a Co / Ni carbon nanofiber membrane. A Ti3C2T solution with a concentration of 5 wt% to 8 wt% is provided. x The dispersion was filtered using a Co / Ni carbon fiber membrane as the filter medium, and the Ti3C2T dispersion was filtered by vacuum filtration. x The dispersion was filtered to obtain Ti3C2T x -Co / Ni carbon fiber film. For Ti3C2T x -Co / Ni carbon fiber film is dried to obtain an electromagnetic shielding film. The electromagnetic shielding film enhances electromagnetic wave absorption efficiency through the interaction of magnetic loss, dielectric loss, and conductive loss. The Co / Ni carbon fiber film layer is combined with Ti3C2T... x The synergistic effect of nanosheets enables electromagnetic waves to undergo absorption, reflection, and reabsorption within the electromagnetic shielding film. This prolongs the propagation path of electromagnetic waves within the shielding film, increases the interaction time and frequency between the electromagnetic waves and the Co / Ni carbon fiber film, and facilitates sufficient attenuation and absorption of electromagnetic waves, reducing secondary electromagnetic pollution. The Co / Ni carbon fiber film and Ti3C2T... x The nanosheets form a complete conductor, allowing current to pass through Ti3C2T efficiently.x The conductive network efficiently converts electrical energy into heat energy.

[0053] Secondly, embodiments of this application also provide an electromagnetic shielding film, which is prepared using the preparation method of the electromagnetic shielding film as described in any embodiment of the first aspect. Please refer to... Figure 2 The electromagnetic shielding film includes Ti3C2T x Nanosheet 12 and Co / Ni carbon fiber film 11, Ti3C2T x Nanosheets 12 are partially disposed on the Co / Ni carbon fiber film layer 11. This electromagnetic shielding film can be attached to electromagnetic shielding equipment to achieve the function of shielding electromagnetic waves. Typically, Ti3C2T... x Nanosheet 12 is disposed on the inner side of the electromagnetic shielding film near the electromagnetic shielding device, and Co / Ni carbon fiber film 11 is disposed on Ti3C2T x The nanosheet layer 12 is located away from the side facing the electromagnetic shielding device. Electromagnetic waves are absorbed by the Co / Ni carbon fiber film layer 11 and then absorbed by the Ti3C2T film. x The nanosheet layer 12 reflects the electromagnetic radiation, which is then absorbed by the Co / Ni carbon fiber film layer 11 to achieve a better electromagnetic shielding effect.

[0054] The preparation method of the electromagnetic shielding film is described below with reference to specific embodiments: Example 1 (1) 0.625 mmol of cobalt nitrate hexahydrate and 0.625 mmol of nickel nitrate hexahydrate were added to 10 mL of methanol to prepare the first mixture. 0.1 mol of 2-methylimidazole was added to 10 mL of methanol and thoroughly ultrasonicated to obtain a 2-methylimidazole solution. The 2-methylimidazole solution was added to the first mixture, stirred and mixed, and allowed to stand at room temperature for 24 h. The mixture was then centrifuged at 2000 rpm / min to obtain the first precipitate. The first precipitate was washed three times with ethanol and then dried in a vacuum drying oven at 70 °C for 4 h to obtain CoNi-MOF powder.

[0055] (2) PAN was dissolved in DMF to obtain 5 mL of spinning solution with a concentration of 12 wt%. CoNi-MOF powder was dispersed in DMF to obtain 5 mL of first dispersion with a concentration of 4 wt%. The first dispersion was added to the spinning solution and stirred to obtain the first emulsion. The first emulsion was added to an electrospinning device. During spinning, a voltage of 15 kV was applied, the distance between the spinning needle and the collector was 30 cm, the diameter of the spinning roller was 5 cm, the length was 20 cm, and the rotation speed was 10 rpm / min. The first emulsion was extruded through the spinning needle to form nanofibers. The nanofibers were collected on the collector and dried to obtain the carbon fiber membrane precursor.

[0056] (3) The carbon fiber membrane precursor was placed in an oven and preheated at 240°C for 2 hours. Then the carbon fiber membrane precursor was placed in a tube furnace and heated to 850°C at a rate of 5°C / min. It was carbonized at 850°C for 1.5 hours and then cooled to obtain Co / Ni carbon fiber membrane.

[0057] (4) Using Co / Ni carbon fiber membrane as the filter medium, the prepared 5 mL of 5 wt% Ti3C2T solution was filtered by vacuum filtration. x The dispersion was filtered to obtain Ti3C2T x -Co / Ni carbon fiber film will yield Ti3C2T x -Co / Ni carbon fiber film was vacuum dried at 80℃ for 2 hours to obtain an electromagnetic shielding film.

[0058] Example 2 (1) 0.625 mmol of cobalt nitrate hexahydrate and 0.625 mmol of nickel nitrate hexahydrate were added to 10 mL of methanol to prepare the first mixture. 0.1 mol of 2-methylimidazole was added to 10 mL of methanol and thoroughly ultrasonicated to obtain a 2-methylimidazole solution. The 2-methylimidazole solution was added to the first mixture, stirred and mixed, and allowed to stand at room temperature for 24 h. The mixture was then centrifuged at 2000 rpm / min to obtain the first precipitate. The first precipitate was washed three times with ethanol and then dried in a vacuum drying oven at 70 °C for 4 h to obtain CoNi-MOF powder.

[0059] (2) PAN was dissolved in DMF to obtain 7 mL of spinning solution with a concentration of 12 wt%. CoNi-MOF powder was dispersed in DMF to obtain 3 mL of first dispersion with a concentration of 4 wt%. The first dispersion was added to the spinning solution and stirred to obtain the first emulsion. The first emulsion was added to an electrospinning device. During spinning, a voltage of 20 kV was applied, the distance between the spinning needle and the collector was 30 cm, the diameter of the spinning roller was 5 cm, the length was 20 cm, and the rotation speed was 5 rpm / min. The first emulsion was extruded through the spinning needle to form nanofibers. The nanofibers were collected on the collector and dried to obtain the carbon fiber membrane precursor.

[0060] (3) The carbon fiber membrane precursor was placed in an oven and preheated at 260°C for 2 hours. Then the carbon fiber membrane precursor was placed in a tube furnace and heated to 800°C at a rate of 5°C / min. It was carbonized at 800°C for 2 hours and then cooled to obtain Co / Ni carbon fiber membrane.

[0061] (4) Using Co / Ni carbon fiber membrane as the filter medium, the prepared 5 mL of 7 wt% Ti3C2T solution was filtered by vacuum filtration.x The dispersion was filtered to obtain Ti3C2T x -Co / Ni carbon fiber film will yield Ti3C2T x -Co / Ni carbon fiber film was vacuum dried at 80℃ for 2 hours to obtain an electromagnetic shielding film.

[0062] Comparative Example 1 (1) 0.625 mmol of cobalt nitrate hexahydrate and 0.625 mmol of nickel nitrate hexahydrate were added to 10 mL of methanol to prepare the first mixture. 0.1 mol of 2-methylimidazole was added to 10 mL of methanol and thoroughly ultrasonicated to obtain a 2-methylimidazole solution. The 2-methylimidazole solution was added to the first mixture, stirred and mixed, and allowed to stand at room temperature for 24 h. The mixture was then centrifuged at 2000 rpm / min to obtain the first precipitate. The first precipitate was washed three times with ethanol and then dried in a vacuum drying oven at 70 °C for 4 h to obtain CoNi-MOF powder.

[0063] (2) PAN was dissolved in DMF to obtain 5 mL of spinning solution with a concentration of 12 wt%. CoNi-MOF powder was dispersed in DMF to obtain 5 mL of first dispersion with a concentration of 4 wt%. The first dispersion was added to the spinning solution and stirred to obtain the first emulsion. The first emulsion was added to an electrospinning device. During spinning, a voltage of 15 kV was applied, the distance between the spinning needle and the collector was 30 cm, the diameter of the spinning roller was 5 cm, the length was 20 cm, and the rotation speed was 10 rpm / min. The first emulsion was extruded through the spinning needle to form nanofibers. The nanofibers were collected on the collector and dried to obtain the carbon fiber membrane precursor.

[0064] (3) The carbon fiber membrane precursor was placed in an oven and preheated at 240°C for 2 hours. Then the carbon fiber membrane precursor was placed in a tube furnace and heated to 850°C at a rate of 5°C / min. It was carbonized at 850°C for 1.5 hours and then cooled to obtain Co / Ni carbon fiber membrane.

[0065] (4) Using a Co / Ni carbon fiber membrane as the filter medium, 2.5 mL of a prepared 5 wt% Ti3C2T solution was filtered by vacuum filtration. x The dispersion was filtered to allow Ti3C2T to adhere to one surface of the Co / Ni carbon fiber membrane. x The nanosheets were then vacuum-dried at 80°C for 2 hours after the first filtration. The dried composite membrane was used as the filter medium, and 2.5 mL of a prepared 5wt% Ti3C2T solution was added. x The dispersion was filtered, resulting in Ti3C2T adhering to the other surface of the Co / Ni carbon fiber membrane. xThe nanosheets are then vacuum dried at 80°C for 2 hours to obtain an electromagnetic shielding film.

[0066] The shielding performance and conductivity of the electromagnetic shielding films prepared in Example 1, Example 2, and Comparative Example 1 were tested respectively. In Example 1 and Example 2, the first surface of the electromagnetic shielding film was the surface of the Co / Ni carbon fiber film layer, and the second surface was Ti3C2T. x The surface of the nanosheets. Unlike Examples 1 and 2, the electromagnetic shielding film in Comparative Example 1 includes a first Ti3C2T... x Nanosheets, Co / Ni carbon fiber film, and second Ti3C2T x Nanosheets and Co / Ni carbon fiber films are deposited on the first Ti3C2T x Nanosheets and the second Ti3C2T x Between nanosheets. In Comparative Example 1, the electromagnetic shielding film has a first surface made of Ti3C2T. x The surface of the nanosheets, the second surface is a second Ti3C2T x The surface of the nanosheets. The test results are shown in Table 1.

[0067] Table 1 Electromagnetic shielding effectiveness (dB) Upper surface conductivity (S / m) Lower surface conductivity (S / m) Reflection coefficient Example 1 66.5 1.75 x 10 3 ]]> 1.53 x 10 6 ]]> 0.12 Example 2 62.2 1.52 x 10 3 ]]> 1.74 x 10 6 ]]> 0.16 Comparative Example 1 60.5 5.21 x 10 5 ]]> 5.95 x 10 5 ]]> 0.75 Based on the test results of electromagnetic shielding effectiveness in Table 1, and by comparing the above embodiments and comparative examples, it can be seen that the electromagnetic shielding effectiveness in Embodiments 1 and 2 is higher than that in Comparative Example 1, indicating that the electromagnetic shielding film prepared in this application embodiment can significantly improve the overall shielding capability. The electromagnetic shielding effectiveness in Embodiment 1 is the highest at 66.5 dB, which can shield the vast majority of electromagnetic waves, and the loss rate is optimal.

[0068] The conductivity of the upper surface in Example 1 is 1.75 × 10⁻⁶. 3 S / m, conductivity of the lower surface is 1.53×10 6 S / m, the conductivity of the upper surface in Example 2 is 1.52 × 10⁻⁶. 3 S / m, conductivity of the lower surface is 1.74×10 6 S / m, the conductivity of the upper surface of Comparative Example 1 is 5.21 × 10⁻⁶. 5 S / m, conductivity of the lower surface is 5.95×10 5S / m. The electromagnetic shielding film in the embodiments exhibits a clear gradient conductivity. In Comparative Example 1, the conductivity of the upper and lower surfaces is similar, with no obvious gradient change. The upper surface in the embodiments has lower conductivity and lower impedance, allowing more electromagnetic waves to enter and be absorbed. The lower surface has higher conductivity, consuming energy through strong conductivity loss and reflecting the remaining electromagnetic waves back to the upper surface for secondary absorption. In Comparative Example 1, the upper surface has higher impedance, making it prone to electromagnetic wave reflection. Less energy is absorbed inside the electromagnetic shielding film, relying mainly on reflection for shielding. Although the electromagnetic shielding effectiveness reaches 60.5dB, it easily causes secondary electromagnetic pollution.

[0069] The reflection coefficients in Examples 1 and 2 are much lower than those in Comparative Example 1, indicating that the electromagnetic shielding film prepared in these examples can significantly reduce the reflectivity of electromagnetic waves and reduce secondary electromagnetic pollution.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of this application as described above, which are not provided in detail for the sake of brevity; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing an electromagnetic shielding film, characterized in that, include: Cobalt salt and nickel salt are added to a first solvent to obtain a first mixture; A 2-methylimidazole solution is provided, which is added to the first mixture, allowed to stand, and then centrifuged to obtain a first precipitate; the first precipitate is dried to obtain a first powder. Polyacrylonitrile fiber is dissolved in dimethylformamide to obtain a spinning solution; a first powder is dispersed in dimethylformamide to obtain a first dispersion; the first dispersion is added to the spinning solution and stirred to obtain a first emulsion. The first emulsion was treated by electrospinning to obtain a carbon nanofiber membrane precursor. The carbon nanofiber membrane precursor is subjected to high-temperature carbonization treatment to obtain a Co / Ni carbon nanofiber membrane. Provides Ti3C2T at concentrations of 5 wt% to 8 wt%. x The dispersion, with the Co / Ni carbon fiber membrane as the filter medium, is filtered by vacuum filtration of the Ti3C2T. x The dispersion was filtered to obtain Ti3C2T x -Co / Ni carbon fiber membrane; For the Ti3C2T x -Co / Ni carbon fiber film is dried to obtain an electromagnetic shielding film.

2. The preparation method according to claim 1, characterized in that, The provided Ti3C2T x The dispersion includes: Provides 20mg to 30mg of Ti3C2T x Powder, containing the Ti3C2T x The powder was dissolved in a second solvent and sonicated in an ice-water bath for 10 to 30 minutes to obtain Ti3C2T. x Dispersion; The second solvent includes at least one of water, N-methylpyrrolidone, dimethyl sulfoxide, or ethanol.

3. The preparation method according to claim 1, characterized in that, The 2-methylimidazole solution is added to the first mixture, allowed to stand, and then centrifuged to obtain a first precipitate. The precipitate is dried to obtain a first powder, comprising: The 2-methylimidazole solution was added to the first mixture and allowed to stand at 23°C to 26°C for 18 to 24 hours. Then, the mixture was centrifuged at 1800 rpm to 2000 rpm to obtain the first precipitate. The first precipitate was washed with ethanol, and then dried in a vacuum environment at a temperature of 50°C to 80°C for 3 to 5 hours to obtain the first powder.

4. The preparation method according to claim 1, characterized in that, The step of obtaining a carbon fiber membrane precursor by electrospinning the first emulsion includes: The first emulsion is added to an electrospinning device with a required voltage of 18kV to 21kV. The electrospinning device includes a spinning needle and a collector, with the distance between the spinning needle and the collector being 25cm to 30cm. The electrospinning device also includes a spinning roller with a diameter of 5cm to 8cm, a length of 15cm to 25cm, and a rotation speed of 8 rpm / min to 15 rpm / min. The first emulsion is extruded through the spinning needle to form nanofibers, which are then collected on the collector and dried to obtain a carbon fiber membrane precursor.

5. The preparation method according to claim 1, characterized in that, The carbon nanofiber membrane precursor is subjected to high-temperature carbonization to obtain a Co / Ni carbon fiber membrane, comprising: The carbon nanofiber membrane precursor was preheated at a temperature of 220°C to 250°C for 2 to 3 hours. A tube furnace is provided, the tube furnace including an inert gas; the tube furnace is heated to 800°C to 900°C at a rate of 5°C / min, the carbon fiber membrane precursor is carbonized for 3 to 4 hours, and then cooled to obtain the Co / Ni carbon fiber membrane.

6. The preparation method according to claim 1, characterized in that, The cobalt salt includes at least one of cobalt chloride, cobalt sulfate, cobalt nitrate, and cobalt carbonate; The nickel salt includes at least one of nickel sulfate, nickel chloride, and nickel nitrate.

7. The preparation method according to claim 1, characterized in that, The first solvent includes at least one of methanol, ethanol, acetone, and deionized water.

8. The preparation method according to claim 1, characterized in that, The provision of the 2-methylimidazole solution comprises: 2-Methylimidazole is provided, and the 2-methylimidazole is added to a second solvent and ultrasonically mixed to obtain the 2-methylimidazole solution; The second solvent includes at least one of methanol, ethanol, acetone, and deionized water.

9. The preparation method according to claim 1, characterized in that, The concentration of the spinning solution is 12 wt% to 14 wt%; the concentration of the first dispersion is 3 wt% to 5 wt%.

10. An electromagnetic shielding film, characterized in that, It is prepared by the method for preparing electromagnetic shielding film as described in any one of claims 1 to 9.

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