An MXene / BC@CoFe2O4 electromagnetic shielding aerogel, its preparation method and application

Abstract

The application belongs to the technical field of electromagnetic shielding materials, and relates to MXene / BC@CoFe2O4 electromagnetic shielding aerogel and a preparation method thereof. The electromagnetic shielding aerogel is composed of MXene, bacterial cellulose (BC) and cobalt ferrite (CoFe2O4) grown by a co-precipitation method, contains anisotropic MXene porous structure, and BC@CoFe2O4 forms a three-dimensional magnetic network. Nano-magnetic particles CoFe2O4 are grown on bacterial cellulose by a co-precipitation method; the bacterial cellulose with the nano-magnetic particles CoFe2O4 grown thereon is mixed with a MXene dispersion liquid to occur liquid self-assembly, thereby forming an aerogel precursor; and a directional three-dimensional porous structure is formed by using a liquid nitrogen directional freezing method. The magnetic particles of the MXene / BC@CoFe2O4 electromagnetic shielding aerogel can cause magnetic loss to electromagnetic waves, the MXene with good electrical conductivity causes impedance mismatch with electromagnetic waves, reflects electromagnetic waves, and the bacterial cellulose can enhance the mechanical properties of the aerogel.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic wave shielding materials, and in particular to an MXene / BC@CoFe2O4 electromagnetic shielding aerogel, its preparation method, and its applications. Background Technology

[0002] With the rapid development of fifth-generation (5G) information technology, electronic devices have improved social productivity and quality of life. However, electromagnetic radiation pollution generated by electronic devices seriously affects human health and the normal operation of electronic instruments. Therefore, researching lightweight and efficient electromagnetic interference (EMI) shielding materials is extremely important for preventing or eliminating electromagnetic pollution.

[0003] Unlike traditional metallic materials, which suffer from high density and susceptibility to corrosion, transition metal carbides / nitrides (MXenes), as an emerging two-dimensional sheet material, exhibit great potential in electromagnetic shielding due to their excellent conductivity and abundant interfacial functional groups. Overcoming the weak interactions between MXene nanosheets is urgently needed to better utilize their unique 3D structural advantages and thus improve their mechanical properties.

[0004] Bacterial cellulose (BC), a widely used nanocellulose, is composed of ultrafine, interconnected nanofibers. Its polymer chains contain numerous oxygen-containing functional groups, contributing to its high tensile strength and excellent hydrophilicity derived from hydrogen bonding. On one hand, the introduction of bacterial cellulose not only provides a highly flexible buffer for enhancing the interlayer separation of MXenes but also ensures the material's integrity through hydrogen bonding, thereby enhancing the mechanical strength of MXene materials. On the other hand, the insertion of nanocellulose into the interlayers of a few MXenes in a single layer can create more interlayer space and improve the effective utilization of MXenes, thus improving electrical conductivity.

[0005] EMI shielding materials composed of highly conductive MXene and magnetic CoFe2O4 exhibit superior performance compared to their single absorption and shielding properties, thus contributing to improved EMI shielding effectiveness. The porous structure increases the reflection path of electromagnetic waves, enhancing the mitigation of multiple electromagnetic losses. The synergy between anisotropic porous structures and an electromagnetic framework promises to simultaneously achieve high-efficiency and mechanically sound EMI shielding materials.

[0006] Chinese patent application number 202210135743.4 discloses an ANF / MXene composite electromagnetic shielding aerogel and its preparation method. This invention prepares an ANF / MXene composite electromagnetic shielding aerogel with a multi-layered porous structure by adding ANF and directional freezing, thereby improving conductivity and withstanding greater external forces. Chinese patent application number 202110023048.4 discloses a method for preparing an MXene / polymer electromagnetic shielding aerogel. This invention prepares an MXene / polymer aerogel by mixing MXene nanosheets and a polymer, which possesses certain mechanical strength and elasticity. Summary of the Invention

[0007] The purpose of this invention is to address the problems existing in the background technology by proposing an MXene / BC@CoFe2O4 electromagnetic shielding aerogel and its preparation method. The electromagnetic shielding aerogel material prepared by this invention has the advantages of good mechanical properties, good electromagnetic shielding performance, low density, and conductivity.

[0008] The technical solution of this invention, a method for preparing MXene / BC@CoFe2O4 electromagnetic shielding aerogel, includes the following specific steps:

[0009] S1. Mix cobalt ion and iron ion solutions, add bacterial cellulose dispersion, then add alkaline solution, heat in a water bath and stir. After the reaction is complete, wash the precipitate with deionized water and alcohol and dry it.

[0010] S2. Etch the carbon aluminum titanium powder to obtain an MXene dispersion;

[0011] S3. Add the bacterial cellulose grown with CoFe2O4 obtained in S1 to the MXene dispersion obtained in S2, and emulsify to obtain a mixed aerogel precursor solution.

[0012] S4. The aerogel precursor solution obtained in S3 is subjected to directional freezing, and then freeze-dried to obtain MXene / BC@CoFe2O4 electromagnetic shielding aerogel.

[0013] The alkaline solution in S1 includes one or a combination of sodium hydroxide solution and ammonia solution;

[0014] The cobalt ion solution in S1 includes one or a combination of cobalt nitrate and cobalt chloride.

[0015] The ferric ion solution in S1 includes one or a combination of ferric nitrate and ferric chloride.

[0016] Preferably, the molar ratio of cobalt ions to iron ions in S1 is 1:2.

[0017] Preferably, the water bath heating temperature in S1 is 80-100℃, and the stirring time is 1-3h.

[0018] Preferably, the etching solution used in S2 is a hydrofluoric acid solution obtained by reacting hydrochloric acid and lithium fluoride.

[0019] Preferably, the mass ratio of bacterial cellulose with CoFe2O4 grown in S3 to MXene in the MXene dispersion is 1:1, 1:2, or 1:3.

[0020] Preferably, the freeze-drying temperature in S4 is -40 to -60°C, and the freeze-drying time is 40 to 60 hours.

[0021] Preferably, the vacuum degree of freeze drying in S4 is 5-20 Pa.

[0022] An MXene / BC@CoFe2O4 electromagnetic shielding aerogel was prepared using the above-described method.

[0023] Application of MXene / BC@CoFe2O4 electromagnetic shielding aerogel prepared using the above method as a shielding material in electronic devices.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects:

[0025] 1. Pure MXene films have high conductivity, which easily leads to impedance mismatch, while the porous structure of MXene aerogels can enhance multiple reflections of electromagnetic waves. MXene aerogels have weak mechanical strength and poor mechanical properties, limiting their application scenarios. Adding bacterial cellulose can enhance the mechanical properties of MXene aerogels, but the poor conductivity of bacterial cellulose reduces the electromagnetic shielding performance of the mixed aerogel. This invention improves the mechanical properties of the mixed aerogel by adding bacterial cellulose to MXene aerogels; by growing CoFe2O4 nanoparticles on bacterial cellulose to form a three-dimensional magnetic network, magnetic loss of electromagnetic waves is induced, improving the absorption capacity of electromagnetic waves. Compared with other methods for preparing electromagnetic shielding materials, the MXene / BC@CoFe2O4 electromagnetic shielding aerogel and its preparation method of this invention have advantages such as simple and feasible process and unique structure. The MXene / BC@CoFe2O4 electromagnetic shielding aerogel and its preparation method of this invention can obtain electromagnetic shielding materials with strong electromagnetic shielding performance. Attached Figure Description

[0026] Figure 1 This is a SEM image of an MXene / BC@CoFe2O4 electromagnetic shielding aerogel according to the present invention;

[0027] Figure 2 SEM image of bacterial cellulose with CoFe2O4 nanoparticles grown on it.

[0028] Figure 3 This invention relates to the electromagnetic shielding performance of the MXene / BC@CoFe2O4 electromagnetic shielding aerogel. Detailed Implementation

[0029] Example 1

[0030] The present invention discloses an MXene / BC@CoFe2O4 electromagnetic shielding aerogel, which is composed of bacterial cellulose grown with CoFe2O4 nanomagnetic particles and a three-dimensional MXene porous structure, and is an electromagnetic shielding aerogel with a three-dimensional magnetic network.

[0031] The present invention discloses an MXene / BC@CoFe2O4 electromagnetic shielding aerogel and its preparation method, comprising the following steps:

[0032] (1) Pretreatment of bacterial cellulose: First, prepare a 1 mol / L ammonium persulfate solution, add a certain amount of bacterial cellulose dispersion into the ammonium persulfate solution, stir for 30 min, and sonicate for 30 min. Centrifuge and wash the treated bacterial cellulose.

[0033] (2) Growth of CoFe2O4 on bacterial cellulose: Prepare a 0.05 mol / L cobalt chloride solution and a 0.1 mol / L ferric chloride solution. Mix the two solutions and stir until homogeneous. Add the bacterial cellulose treated in (1) to the mixed solution and stir. Add sodium hydroxide solution dropwise and stir the solution at 95°C for 2 hours.

[0034] (3) Preparation of MXene dispersion: First, mix 40 mL of analytical grade hydrochloric acid and 10 mL of deionized water to prepare a hydrochloric acid solution. Add 4 g of LiF to the hydrochloric acid solution and stir for 5 min. After stirring, gradually add 2 g of Ti3AlC2 powder to the mixed solution and stir with a magnetic stirrer for 24 h at a stirring speed of 500 r / min. The reaction temperature is room temperature. Wash the product continuously with deionized water until the solution is neutral, and then centrifuge. Add 200 mL of deionized water to the lower layer of product, introduce argon gas, and sonicate in an ice-water bath for 4 h. Centrifuge the sonicated solution at 4000 r / min for 10 min to obtain the upper liquid, which is the MXene dispersion.

[0035] (4) Preparation of mixed aerogel precursor: The bacterial cellulose with CoFe2O4 growth is added to the MXene dispersion, wherein the mass ratio of MXene is 80% and the mixture is stirred at high speed with an emulsifier to uniformly disperse the bacterial cellulose with CoFe2O4 growth in the MXene dispersion to form a mixed aerogel precursor.

[0036] (5) Preparation of MXene / BC@CoFe2O4 electromagnetic shielding aerogel: The precursor solution in (4) was introduced into a custom polytetrafluoroethylene mold, and then the mold containing the solution was placed in a liquid nitrogen atmosphere and directionally frozen for a period of time. Then the frozen mold was transferred to a vacuum freeze dryer and freeze-dried at -60℃ and 10Pa for 48h.

[0037] Example 2

[0038] The present invention discloses an MXene / BC@CoFe2O4 electromagnetic shielding aerogel, which is composed of bacterial cellulose grown with CoFe2O4 nanomagnetic particles and a three-dimensional MXene porous structure, and is an electromagnetic shielding aerogel with a three-dimensional magnetic network.

[0039] The present invention discloses an MXene / BC@CoFe2O4 electromagnetic shielding aerogel and its preparation method, comprising the following steps:

[0040] (1) Pretreatment of bacterial cellulose: First, prepare a 1 mol / L ammonium persulfate solution, add a certain amount of bacterial cellulose dispersion into the ammonium persulfate solution, stir for 30 min, and sonicate for 30 min. Centrifuge and wash the treated bacterial cellulose.

[0041] (2) Growth of CoFe2O4 on bacterial cellulose: Prepare a 0.05 mol / L cobalt chloride solution and a 0.1 mol / L ferric chloride solution. Mix the two solutions and stir until homogeneous. Add the bacterial cellulose treated in (1) to the mixed solution and stir. Add sodium hydroxide solution dropwise and stir the solution at 95°C for 2 hours.

[0042] (3) Preparation of MXene dispersion: First, mix 40 mL of analytical grade hydrochloric acid and 10 mL of deionized water to prepare a hydrochloric acid solution. Add 4 g of LiF to the hydrochloric acid solution and stir for 5 min. After stirring, gradually add 2 g of Ti3AlC2 powder to the mixed solution and stir with a magnetic stirrer for 24 h at a stirring speed of 500 r / min. The reaction temperature is room temperature. Wash the product continuously with deionized water until the solution is neutral, and then centrifuge. Add 200 mL of deionized water to the lower layer of product, introduce argon gas, and sonicate in an ice-water bath for 4 h. Centrifuge the sonicated solution at 4000 r / min for 10 min to obtain the upper liquid, which is the MXene dispersion.

[0043] (4) Preparation of mixed aerogel precursor: The bacterial cellulose with CoFe2O4 growth was added to the MXene dispersion, wherein the mass ratio of MXene was 85.7% and the mixture was stirred at high speed with an emulsifier to uniformly disperse the bacterial cellulose with CoFe2O4 growth in the MXene dispersion to form a mixed aerogel precursor.

[0044] (5) Preparation of MXene / BC@CoFe2O4 electromagnetic shielding aerogel: The precursor solution in (4) was introduced into a custom polytetrafluoroethylene mold, and then the mold containing the solution was placed in a liquid nitrogen atmosphere and directionally frozen for a period of time. Then the frozen mold was transferred to a vacuum freeze dryer and freeze-dried at -60℃ and 10Pa for 48h.

[0045] Example 3

[0046] The present invention discloses an MXene / BC@CoFe2O4 electromagnetic shielding aerogel, which is composed of bacterial cellulose grown with CoFe2O4 nanomagnetic particles and a three-dimensional MXene porous structure, and is an electromagnetic shielding aerogel with a three-dimensional magnetic network.

[0047] The present invention discloses an MXene / BC@CoFe2O4 electromagnetic shielding aerogel and its preparation method, comprising the following steps:

[0048] (1) Pretreatment of bacterial cellulose: First, prepare a 1 mol / L ammonium persulfate solution, add a certain amount of bacterial cellulose dispersion into the ammonium persulfate solution, stir for 30 min, and sonicate for 30 min. Centrifuge and wash the treated bacterial cellulose.

[0049] (2) Growth of CoFe2O4 on bacterial cellulose: Prepare a 0.05 mol / L cobalt chloride solution and a 0.1 mol / L ferric chloride solution. Mix the two solutions and stir until homogeneous. Add the bacterial cellulose treated in (1) to the mixed solution and stir. Add sodium hydroxide solution dropwise and stir the solution at 95°C for 2 hours.

[0050] (3) Preparation of MXene dispersion: First, mix 40 mL of analytical grade hydrochloric acid and 10 mL of deionized water to prepare a hydrochloric acid solution. Add 4 g of LiF to the hydrochloric acid solution and stir for 5 min. After stirring, gradually add 2 g of Ti3AlC2 powder to the mixed solution and stir with a magnetic stirrer for 24 h at a stirring speed of 500 r / min. The reaction temperature is room temperature. Wash the product continuously with deionized water until the solution is neutral, and then centrifuge. Add 200 mL of deionized water to the lower layer of product, introduce argon gas, and sonicate in an ice-water bath for 4 h. Centrifuge the sonicated solution at 4000 r / min for 10 min to obtain the upper liquid, which is the MXene dispersion.

[0051] (4) Preparation of mixed aerogel precursor: The bacterial cellulose with CoFe2O4 growth is added to the MXene dispersion, wherein the mass ratio of MXene is 90.9% and the mixture is stirred at high speed with an emulsifier to uniformly disperse the bacterial cellulose with CoFe2O4 growth in the MXene dispersion to form a mixed aerogel precursor.

[0052] (5) Preparation of MXene / BC@CoFe2O4 electromagnetic shielding aerogel: The precursor solution in (4) was introduced into a custom polytetrafluoroethylene mold, and then the mold containing the solution was placed in a liquid nitrogen atmosphere and directionally frozen for a period of time. Then the frozen mold was transferred to a vacuum freeze dryer and freeze-dried at -60℃ and 10Pa for 48h.

[0053] The electromagnetic shielding performance of the MXene / BC@CoFe2O4 electromagnetic shielding aerogels prepared in Examples 1-3 was tested; the results are as follows: Figure 3 As shown in the figure, the electromagnetic shielding aerogel exhibits the best electromagnetic shielding performance when the MXene mass percentage is 85.7%, with a corresponding electromagnetic shielding performance of 82.5 dB.

[0054] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A method for preparing MXene / BC@CoFe2O4 electromagnetic shielding aerogel, characterized in that, The specific steps include the following: S1. Mix cobalt ion and iron ion solutions, add bacterial cellulose dispersion, then add alkaline solution, heat in a water bath and stir. After the reaction is complete, wash the precipitate with deionized water and alcohol and dry it. In S1, the alkaline solution is sodium hydroxide solution; the cobalt ion solution is cobalt chloride; the ferric ion solution is ferric chloride; and the molar ratio of cobalt ions to ferric ions in S1 is 1:

2. S2. Etch the carbon aluminum titanium powder to obtain an MXene dispersion; S3. Add the bacterial cellulose with CoFe2O4 growth obtained in S1 to the MXene dispersion obtained in S2, and emulsify it to obtain a mixed aerogel precursor solution. S4. The aerogel precursor solution obtained in S3 is directionally frozen and then freeze-dried to obtain MXene / BC@CoFe2O4 electromagnetic shielding aerogel. The prepared electromagnetic shielding aerogel is an electromagnetic shielding aerogel with a three-dimensional magnetic network.

2. The preparation method of the MXene / BC@CoFe2O4 electromagnetic shielding aerogel according to claim 1, characterized in that, The water bath heating temperature in S1 is 80-100℃, and the stirring time is 1-3h.

3. The method for preparing an MXene / BC@CoFe2O4 electromagnetic shielding aerogel according to claim 1, characterized in that, The etching solution used in S2 is a hydrofluoric acid solution obtained by reacting hydrochloric acid and lithium fluoride.

4. The method for preparing an MXene / BC@CoFe2O4 electromagnetic shielding aerogel according to claim 1, characterized in that, The mass ratio of bacterial cellulose with CoFe2O4 grown in S3 to MXene in the dispersion was 1:1, 1:2, and 1:

3.

5. The method for preparing an MXene / BC@CoFe2O4 electromagnetic shielding aerogel according to claim 1, characterized in that, In S4, the freeze-drying temperature is -40 to -60 ℃, and the freeze-drying time is 40-60 h.

6. The method for preparing an MXene / BC@CoFe2O4 electromagnetic shielding aerogel according to claim 1, characterized in that, The vacuum degree for freeze drying in S4 is 5-20 Pa.

7. An MXene / BC@CoFe2O4 electromagnetic shielding aerogel, characterized in that, It is prepared using the preparation method described in any one of claims 1-6.

8. The application of MXene / BC@CoFe2O4 electromagnetic shielding aerogel, prepared using the preparation method according to any one of claims 1-6, as a shielding material in electronic devices.

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