Preparation method of self-adaptive anti-electromagnetic interference composite material

Abstract

The invention discloses a preparation method of a self-adaptive anti-electromagnetic interference composite material, which comprises the following steps: firstly, etching a Ti3AlC2 precursor through a LiF / HCl solution to prepare few-layer MXene powder; the preparation method comprises the following steps: preparing a carbon nanotube / Ti < 3 > C < 2 > T < x > MXene powder / chitosan / polyethyleneimine dispersion liquid through a chemical crosslinking method; and finally, carrying out a freeze drying process to obtain the carbon nanotube / Ti < 3 > C < 2 > T < x > MXene powder / chitosan / polyethyleneimine composite aerogel. The carbon nanotube / Ti < 3 > C < 2 > T < x > MXene powder / chitosan / polyethyleneimine composite aerogel prepared by the preparation method disclosed by the invention is excellent in electromagnetic shielding performance and high in absorption capacity, and can meet the application requirements in the fields of aerospace, electronic packaging and the like. Meanwhile, the strain sensing capacity is achieved, the sensitivity is outstanding under different strains, repeatability and linearity are good, the capacity of distinguishing different strain magnitudes is achieved, and the strain sensor is suitable for scenes needing dynamic and quantitative strain monitoring. The composite material has efficient electromagnetic shielding performance and excellent sensing performance, and has a wide application prospect in practical application.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite material preparation, and particularly relates to a preparation method of an adaptive electromagnetic interference resistant composite material. Background Art

[0002] With the rapid development of communication technology and the wide popularization of wearable electronic products, the problem of electromagnetic radiation pollution has become increasingly prominent. Electromagnetic radiation not only interferes with the normal operation of adjacent electronic devices, but also poses a potential threat to human health and national security. Developing efficient electromagnetic shielding materials has become a key strategy to solve this problem. At the same time, the miniaturization of electronic products and the demand for multi-functional integration drive the development of composite materials towards the direction of "a single material with multiple properties". Especially in the fields of wearable devices, intelligent electronic skin and aerospace, composite materials with both electromagnetic shielding and strain sensing functions have important application values.

[0003] Although traditional electromagnetic shielding materials (such as metal films) have excellent shielding efficiency, they have defects such as large weight, poor flexibility, and inability to integrate sensing functions. Carbon nanotubes (CNT) and Ti3C2Tx MXene, as emerging one-dimensional / two-dimensional conductive fillers, have become research hotspots due to their high conductivity and unique layered structure. CNT can construct conductive pathways, and the two-dimensional plane of MXene provides abundant conductive contact points. The synergy of the two can significantly improve the conductivity of the material. However, the self-gelation ability of MXene is insufficient, and it is difficult to form a stable three-dimensional skeleton, which limits its application in complex environments.

[0004] The selection of polymer matrix is crucial for the performance of composite materials. Although carboxymethyl chitosan (CCS) has biocompatibility and rich functional groups, the aerogel prepared alone has insufficient flexibility and cannot meet the requirements of dynamic strain monitoring. The flexible chain segments of polyethyleneimine (PEI) can endow the material with elasticity, but interface modification is required to enhance the binding with inorganic fillers. The silane coupling agent KH560 can graft PEI onto the surface of CCS through chemical cross-linking, optimize the cross-linking network density, and at the same time enhance the interfacial binding with CNT and MXene through hydrogen bonding to form a stable organic-inorganic composite system.

[0005] In the prior art, it is necessary to provide a preparation method of an adaptive electromagnetic interference resistant composite material to balance the electromagnetic shielding efficiency and sensing performance of the composite material, and improve the filler dispersion and interfacial compatibility. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preparing an adaptive electromagnetic interference-resistant composite material. By constructing a "one-dimensional CNT + two-dimensional MXene" synergistic conductive network and combining a PEI / CCS elastic matrix with KH560 interfacial modification, a composite aerogel with both high-efficiency electromagnetic shielding (the highest SET is 36.96 dB) and wide-range strain sensing (10% - 90% strain response) is developed, providing a new path for the design of multifunctional composite materials and solving the problems that the electromagnetic shielding performance of composite materials in the prior art cannot be reconciled and it is difficult for composite materials to be applied in fields with special requirements.

[0007] The technical principle adopted in the present invention is as follows: Carbon nanotubes (CNT) and Ti3C2T x (MXene), as typical one-dimensional and two-dimensional conductive fillers, are widely used in the preparation of various shielding materials due to their unique electrical properties and structural characteristics. However, MXene has relatively weak gelation ability and it is difficult to construct a strong and stable three-dimensional skeleton structure in practical applications, which limits the full play of its performance. In contrast, carboxylated carbon nanotubes (CNT) with high conductivity and high mechanical strength can effectively bridge MXene by constructing conductive paths to make up for its structural defects. The large two-dimensional planar structure of MXene can provide rich conductive contact points and a vast conductive area. Acting synergistically with CNT, it can make the conductive network more dense and perfect, greatly promoting electron transport, significantly enhancing the conductivity of the material, and thus enhancing the electromagnetic shielding efficiency.

[0008] Carboxymethyl chitosan (CCS), as a natural polysaccharide, has attracted much attention in related research fields due to its good biodegradability, hydrophilicity and abundant functional groups. However, the aerogel prepared by using CCS alone has poor flexibility and it is difficult to achieve precise sensing in complex environments. Polyethylene imine (PEI), as a water-soluble polyelectrolyte polymer containing primary, secondary and tertiary amine groups, its flexible molecular chain segments can endow the material with good elasticity and deformation recovery ability. Grafting PEI onto the surface of CCS through a silane coupling agent (KH560) can effectively regulate the crosslinking network density and optimize the elastic properties of the aerogel. In addition, the abundant hydroxyl groups on the surface of MXene can form hydrogen bond interactions with the amino groups of PEI and the hydroxyl groups of CCS, and the carboxyl groups of CNT can also generate hydrogen bond interactions with the amino groups of PEI, the hydroxyl groups of CCS and MXene. The synergy of excellent elasticity and the conductive network can realize the recognition and resolution of external pressure signals by the aerogel, meeting its application as a piezoresistive flexible sensor in practice.

[0009] In summary, using CCS / PEI as an auxiliary framework and introducing conductive fillers with the advantages of different dimensions (one-dimensional CNT and two-dimensional MXene) into the framework simultaneously to construct a conductive network, and then forming a stable and excellent elastic three-dimensional composite aerogel is a highly potential innovative strategy. The synergistic effect of the improved impedance matching and the perfect conductive network of the composite aerogel endows it with excellent electromagnetic shielding effectiveness; the coexistence of excellent elasticity and the conductive network for the second time enables the detection and recognition of external signals, and it is expected to be used as a flexible sensor. The simultaneous acquisition of electromagnetic shielding effectiveness and flexible sensing performance realizes the multifunctionality of the composite aerogel and lays a foundation for expanding its application fields.

[0010] The technical solution adopted in the present invention is a preparation method of an adaptive electromagnetic interference-resistant composite material, and the specific steps are as follows:

[0011] Step 1, etching and removing the Al layer in the Ti3AlC2 precursor by the replacement HF method (a mixed solution of LiF and HCl) to prepare accordion-like Ti3C2T x MXene powder;

[0012] Step 2, subjecting the accordion-like powder to ultrasonic oscillation, centrifugal washing, and freeze-drying to prepare single (few)-layer Ti3C2T x MXene powder;

[0013] Step 3, dissolving chitosan (CCS) in deionized water to prepare an aqueous solution with a CCS concentration of 2 wt%;

[0014] Step 4, adding a certain amount of KH560 to the 2 wt% CCS aqueous solution for ultrasonic dispersion to obtain a KH560 / CCS mixed solution;

[0015] Step 5, adding an appropriate amount of PEI to the KH560 / CCS mixed solution and performing magnetic stirring to obtain a KH560 / CCS / PEI mixed solution;

[0016] Step 6, adding an appropriate amount of CNT and few-layer MXene to the above KH560 / CCS / PEI mixed solution for ultrasonic stirring to prepare a composite material precursor solution;

[0017] Step 7, transferring the composite material precursor solution to a mold, and then placing the mold in an oven for crosslinking to obtain a pre-polymerized CNT / MXene / CCS / PEI mixed solution;

[0018] Step 8, subjecting the pre-polymerized CNT / MXene / CCS / PEI mixed solution to freeze-drying to obtain a CNT / MXene / CCS / PEI aerogel.

[0019] Preferably, in Step 1, the specific steps are as follows:

[0020] First, LiF and HCl are fully mixed to obtain a LiF / HCl solution, and then the MAX phase precursor powder is slowly added to the LiF / HCl mixed solution under ice bath conditions to obtain a mixed solution; the mass ratio of LiF, HCl and MAX phase precursor powder is 1:15~20:1. The manufacturer of MAX phase precursor powder (Ti3AlC2 powder) is Beijing Fusman Technology Co., Ltd. The purity of MAX phase precursor powder is 98%, and the particle size of MAX phase precursor powder is 200~500 mesh.

[0021] Then, the mixed solution was continuously stirred magnetically at 35-45 degrees Celsius for 24-48 hours to obtain multilayer Ti3C2T x The suspension was then repeatedly centrifuged and washed with deionized water until the pH of the solution was 6-7 to obtain the accordion-shaped Ti3C2T x The precipitate is Ti3C2T x MXene powder. During centrifugal washing, the centrifugal speed is 3500~4000r / min.

[0022] Preferably, in step 2, the specific steps are as follows:

[0023] First, multilayer Ti3C2T x MXene powder was dispersed in deionized water and ultrasonically treated for 15-20 min to promote the exfoliation of multilayer MXene. Then, the mixture was centrifuged at 3500-4000 r / min for 15-20 min, and the cycle was repeated several times. The supernatant was collected to obtain a few-layer MXene dispersion.

[0024] Then, the few-layer MXene dispersion obtained above is freeze-dried in a freeze dryer to obtain a few-layer MXene powder.

[0025] Preferably, in step 3, the specific steps are as follows:

[0026] Under the action of magnetic stirring, carboxymethyl chitosan (CCS) is fully dissolved in deionized water to prepare a CCS aqueous solution. The magnetic stirring speed is 500-800 rpm / min and the duration is 1-2 hours.

[0027] Preferably, in step 4, the specific steps are as follows:

[0028] KH560 was added to the CCS aqueous solution and magnetically stirred at room temperature to obtain a KH560 / CCS mixed solution. The magnetic stirring speed was 500-800 rpm / min and the duration was 1-2 hours.

[0029] Preferably, in step 5, the specific steps are as follows:

[0030] Polyethyleneimine (PEI) was added to the uniformly mixed KH560 / CCS mixed solution, and a uniform KH560 / CCS / PEI mixed solution was obtained by ultrasonic stirring. The ultrasonic stirring power was 360 W and the duration was 1 hour.

[0031] Preferably, in step 6, the specific steps are as follows:

[0032] An appropriate amount of carboxylated carbon nanotubes (CNT) and MXene were added to the above uniform KH560 / CCS / PEI mixed solution, and they were uniformly dispersed by ultrasonic stirring. The ultrasonic stirring power was 360 - 500 W and the duration was 2 - 3 hours. The mass ratio of CCS, PEI, CNT, MXene and deionized water was 1:0.4:1:0.5:0 - 1:49.

[0033] Preferably, in step 7, the specific steps are as follows:

[0034] First, the precursor solution was equally transferred into a six - hole mold;

[0035] Then, the mold containing the precursor solution was transferred to an oven to promote cross - linking. Through cross - linking, a pre - polymerized CNT / MXene / CCS / PEI mixed solution was obtained. The oven temperature was set at 60 - 80 °C and the time was set at 3 - 5 hours.

[0036] Preferably, in step 8, the specific steps are as follows:

[0037] First, the six - hole mold containing the pre - polymerized CNT / MXene / CCS / PEI mixed solution was frozen at - 50 - - 60 °C for 12 - 24 h to obtain a CNT / MXene / CCS / PEI hydrogel;

[0038] Then, the CNT / MXene / CCS / PEI hydrogel was freeze - dried to obtain a CNT / MXene / CCS / PEI aerogel. The freeze - drying temperature was - 60 - - 80 °C and the duration was 72 - 96 hours.

[0039] The beneficial effects of the present invention are:

[0040] 1. The CNT / MXene / CCS / PEI composite aerogel prepared by the present invention has achieved a breakthrough in the synergistic integration of high-efficiency electromagnetic shielding and precise strain sensing performance. Through the three-dimensional conductive network constructed by one-dimensional carbon nanotubes (CNT) and two-dimensional few-layer MXene, combined with the multiple reflection, scattering and polarization loss mechanisms of electromagnetic waves by the porous structure, its electromagnetic shielding effectiveness (SET) can reach up to 36.96 dB, far exceeding the commercial standard (20 dB), and can effectively meet the protection requirements in strong electromagnetic environments such as aerospace and electronic packaging. At the same time, the elastic network of the aerogel (PEI flexible segment + chemical cross-linking structure) and the conductive network act synergistically to show a sensitive and linear current signal response in the strain range of 10% - 90%, which can clearly distinguish different strain levels and provide a new solution for the dynamic deformation monitoring of wearable devices.

[0041] 2. Through the innovative multi-dimensional filler collaborative design of the present invention, one-dimensional CNT serves as a conductive bridge to make up for the deficiency of the gelation ability of MXene and construct an efficient electron transport path; the large planar structure of two-dimensional few-layer MXene provides abundant conductive contact points, and the two act synergistically to form a dense conductive network, significantly improving the conductivity of the material. At the same time, the silane coupling agent KH560 covalently connects carboxymethyl chitosan (CCS) and polyethyleneimine (PEI) through chemical cross-linking, and forms hydrogen bonds with the carboxyl group of CNT and the hydroxyl group of MXene, effectively enhancing the interfacial binding force between the inorganic filler and the organic matrix, inhibiting filler agglomeration, and improving the structural stability and conductive uniformity of the composite material.

[0042] 3. The present invention adopts a preparation process combining chemical cross-linking and freeze-drying, with a simple and controllable process. It does not require high temperature, high pressure or special equipment, and can be completed only through 8 core steps. From the etching of MXene with LiF / HCl to freeze-drying and forming, each process parameter (such as etching temperature of 35 - 45 °C, centrifugation rate of 3500 - 4000 r / min, cross-linking temperature of 60 - 80 °C, etc.) is clear and easy to reproduce, ensuring the consistency of batch production. In addition, LiF / HCl is used to replace highly toxic HF for etching, significantly improving the process safety, and the main raw materials (such as CCS, PEI, etc.) are all commercially available materials with low cost, making industrial production feasible.

[0043] 4. By flexibly regulating the MXene content (0.1 - 1 times the mass of CCS), the present invention can achieve the directional optimization of the electromagnetic shielding effectiveness of the composite aerogel: when the MXene content is 0, the shielding effectiveness is only 7.99 dB; when the MXene content is increased to 1, the shielding effectiveness jumps to 36.96 dB, meeting the differential shielding requirements in different scenarios. Meanwhile, the strain sensing performance of the aerogel can be adjusted by the filler ratio, showing significant differences in current signals in both the low strain (10%) and high strain (90%) ranges. Especially in the high strain range of 70% - 90%, the response slope is larger, making it suitable for deformation monitoring under complex working conditions, such as human joint movement tracking or real-time stress detection of intelligent equipment.

[0044] 5. In terms of the electromagnetic shielding mechanism of the present invention, the composite aerogel optimizes the impedance matching through the porous structure, guiding electromagnetic waves into the interior, and achieving the efficient attenuation of electromagnetic waves through the synergistic effects of conductive loss (CNT / MXene), multiple reflection and scattering loss (three-dimensional network), and polarization loss (heterogeneous interface). In terms of the strain sensing mechanism, the flexible molecular chain segments of PEI endow the aerogel with high elasticity (able to withstand 90% strain). During the deformation process, the conductive network is reversibly reconstructed. At the same time, the protonated amino groups of PEI fix CNT / MXene through electrostatic adsorption, ensuring the stability of the conductive path and enabling the aerogel to maintain a sensitive current signal response in both the compressed and stretched states, providing a reliable theoretical basis for the design of multifunctional composite materials. Brief Description of the Drawings

[0045] Figure 1 is the total electromagnetic shielding effectiveness (SE T ) diagram of the CNT / MXene / CCS / PEI composite aerogel under different MXene contents in the method of the present invention;

[0046] Figure 2 is the SE A diagram of the CNT / MXene / CCS / PEI composite aerogel under different MXene contents in the method of the present invention;

[0047] Figure 3 is the SE R diagram of the CNT / MXene / CCS / PEI composite aerogel under different MXene contents in the method of the present invention;

[0048] Figure 4 is the current signal response curve of the CNT / MXene / CCS / PEI composite aerogel under different MXene contents in the method of the present invention. Detailed Embodiments

[0049] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0050] Example 1

[0051] This embodiment provides a preparation method of an adaptive electromagnetic interference resistant composite material, and the specific steps are as follows:

[0052] Step 1, etching and removing the Al layer in the Ti3AlC2 precursor to prepare accordion-shaped Ti3C2T x MXene powder by the replacement HF method (LiF and HCl mixed solution), and the specific steps are as follows:

[0053] First, fully mix LiF and HCl to obtain a LiF / HCl solution, and then slowly add the MAX phase precursor powder to the LiF / HCl mixed solution under ice bath conditions to obtain a mixed solution;

[0054] The mass ratio of LiF, HCl to the MAX phase precursor powder is 1:15:1.

[0055] The purity of the MAX phase precursor powder (Ti3AlC2 powder) is 98%, and the particle size of the MAX phase precursor powder is 200 mesh.

[0056] Then, continuously magnetically stir the mixed solution at 35 °C for 24 hours to obtain a multi-layer Ti3C2T x suspension, and then repeatedly centrifuge and wash with deionized water until the solution pH is 6 to obtain an accordion-shaped Ti3C2T x precipitate; when centrifuging and washing, the centrifugation rate is 3500 r / min.

[0057] Step 2, performing ultrasonic oscillation, centrifugal washing and freeze-drying on the accordion-shaped powder to prepare single (few) layer Ti3C2T x MXene powder, and the specific steps are as follows:

[0058] First, disperse the multi-layer Ti3C2T x precipitate in deionized water, perform ultrasonic treatment for 15 min to promote the peeling of the multi-layer MXene, and then continue to centrifuge at a rate of 3500 r / min for 15 min for several cycles, take the supernatant to obtain a few-layer MXene dispersion;

[0059] Then, perform freeze-drying on the obtained few-layer MXene dispersion in a freeze dryer to obtain few-layer MXene powder.

[0060] Step 3: Dissolve chitosan (CCS) in deionized water to prepare an aqueous solution with a CCS concentration of 2 wt%, and the specific steps are as follows:

[0061] Under magnetic stirring, fully dissolve carboxymethyl chitosan (CCS) in deionized water to prepare an aqueous CCS solution. The magnetic stirring speed is 500 rpm / min and the duration is 1 hour.

[0062] Step 4: Add a certain amount of KH560 to the 2 wt% CCS aqueous solution for ultrasonic dispersion to obtain a KH560 / CCS mixed solution, and the specific steps are as follows:

[0063] Add KH560 accounting for 5% of the mass of chitosan to the above CCS aqueous solution, and stir magnetically at room temperature to obtain a uniformly mixed KH560 / CCS solution. The magnetic stirring speed is 500 rpm / min and the duration is 1 hour.

[0064] Step 5: Add an appropriate amount of PEI to the KH560 / CCS mixed solution and stir magnetically to obtain a KH560 / CCS / PEI mixed solution, and the specific steps are as follows:

[0065] Add polyethyleneimine (PEI) to the uniformly mixed KH560 / CCS mixed solution. The addition amount of polyethyleneimine is 40% of the mass of chitosan, and a uniformly mixed KH560 / CCS / PEI solution is obtained through ultrasonic stirring. The ultrasonic stirring power is 360 W and the duration is 1 hour.

[0066] Step 6: Add an appropriate amount of CNT and few-layer MXene to the above KH560 / CCS / PEI mixed solution and stir ultrasonically to prepare a composite precursor solution, and the specific steps are as follows:

[0067] Add an appropriate amount of carboxylated carbon nanotubes (CNT) and MXene to the above uniformly mixed KH560 / CCS / PEI mixed solution, and disperse them uniformly through ultrasonic stirring. The ultrasonic stirring power is 360 W and the duration is 2 hours. The mass ratio of CCS, PEI, CNT, MXene and deionized water is 1:0.4:1:0.1:49.

[0068] Step 7: Transfer the composite precursor solution to a mold, and then put the mold into an oven for crosslinking to obtain a pre-polymerized CNT / MXene / CCS / PEI mixed solution, and the specific steps are as follows:

[0069] First, transfer the mixed solution in equal parts to a six-well mold;

[0070] Then, transfer the mold filled with the mixed solution to an oven to promote crosslinking. Through crosslinking, a prepolymerized CNT / MXene / CCS / PEI mixed solution is obtained. The oven temperature is set at 60 °C and the time is set at 3 hours.

[0071] Step 8, the prepolymerized CNT / MXene / CCS / PEI mixed solution is freeze-dried to obtain a CNT / MXene / CCS / PEI aerogel.

[0072] First, place the six-well mold filled with the prepolymerized CNT / MXene / CCS / PEI mixed solution in a freezer at -50 °C for 12 h to obtain a CNT / MXene / CCS / PEI hydrogel;

[0073] Then, the CNT / MXene / CCS / PEI hydrogel is freeze-dried to obtain a CNT / MXene / CCS / PEI aerogel.

[0074] The freeze-drying temperature is -60 °C and the duration is 72 hours.

[0075] The electromagnetic shielding effectiveness of the CNT / MXene / CCS / PEI composite aerogel prepared in Example 1 is 21.99 dB, which has met the requirements of commercial electromagnetic shielding applications (20 dB).

[0076] Example 2

[0077] This example provides a method for preparing an adaptive electromagnetic interference resistant composite material, and the specific steps are as follows:

[0078] Step 1, use the replacement HF method (a mixed solution of LiF and HCl) to etch and remove the Al layer in the Ti3AlC2 precursor to prepare accordion-like Ti3C2T x MXene powder, and the specific steps are as follows:

[0079] First, fully mix LiF and HCl to obtain a LiF / HCl solution, and then slowly add the MAX phase precursor powder to the LiF / HCl mixed solution under ice bath conditions to obtain a mixed solution;

[0080] The mass ratio of LiF, HCl to the MAX phase precursor powder is 1:18:1.

[0081] The purity of the MAX phase precursor powder is 98%, and the particle size of the MAX phase precursor powder is 350 mesh.

[0082] Then, continuously magnetically stir the mixed solution at 40 °C for 36 hours to obtain multilayer Ti3C2T xThe suspension was then repeatedly centrifuged and washed with deionized water until the solution pH reached 6.5, obtaining accordion-like Ti3C2T x precipitate; during centrifugation and washing, the centrifugation rate was 3750 r / min.

[0083] Step 2: The accordion-like powder was ultrasonically oscillated, centrifuged and washed, and freeze-dried to prepare monolayer (few-layer) Ti3C2T x MXene powder, and the specific steps are as follows:

[0084] First, disperse the multi-layer Ti3C2T x precipitate in deionized water and ultrasonically treat it for 18 min to promote the exfoliation of multi-layer MXene. Then continue to centrifuge at a rate of 3750 r / min for 18 min for several cycles, take the supernatant, and obtain a few-layer MXene dispersion;

[0085] Then, the obtained few-layer MXene dispersion was freeze-dried in a freeze dryer to obtain few-layer MXene powder.

[0086] Step 3: Dissolve chitosan (CCS) in deionized water to prepare an aqueous solution with a CCS concentration of 2 wt%, and the specific steps are as follows:

[0087] Under magnetic stirring, carboxymethyl chitosan (CCS) was fully dissolved in deionized water to prepare a CCS aqueous solution. The magnetic stirring speed was 650 rpm / min and the duration was 1.5 hours.

[0088] Step 4: Add a certain amount of KH560 to the 2 wt% CCS aqueous solution for ultrasonic dispersion to obtain a KH560 / CCS mixed solution, and the specific steps are as follows:

[0089] Add KH560 to the above CCS aqueous solution and magnetically stir at room temperature to obtain a uniformly mixed KH560 / CCS solution. The magnetic stirring speed was 650 rpm / min and the duration was 1.5 hours.

[0090] Step 5: Add an appropriate amount of PEI to the KH560 / CCS mixed solution and magnetically stir to obtain a KH560 / CCS / PEI mixed solution, and the specific steps are as follows:

[0091] Add polyethyleneimine (PEI) to the uniformly mixed KH560 / CCS mixed solution and obtain a uniformly mixed KH560 / CCS / PEI solution through ultrasonic stirring. The ultrasonic stirring power was 360 W and the duration was 1 hour.

[0092] Step 6: Add an appropriate amount of CNT and few-layer MXene to the above KH560 / CCS / PEI mixed solution, and stir it with ultrasonic waves to prepare a composite precursor solution. The specific steps are as follows:

[0093] Add an appropriate amount of carboxylated carbon nanotubes (CNT) and MXene to the above homogeneous KH560 / CCS / PEI mixed solution, and disperse them evenly by ultrasonic stirring. The ultrasonic stirring power is 420 W, and the duration is 2.5 hours. The mass ratio of CCS, PEI, CNT, MXene, and deionized water is 1:0.4:1:0.5:49.

[0094] Step 7: Transfer the composite precursor solution to a mold, and then place the mold in an oven for crosslinking to obtain a prepolymerized CNT / MXene / CCS / PEI mixed solution. The specific steps are as follows:

[0095] First, transfer the mixed solution in equal parts to a six-well mold;

[0096] Then, transfer the mold containing the mixed solution to an oven to promote crosslinking. Through crosslinking, a prepolymerized CNT / MXene / CCS / PEI mixed solution is obtained. The oven temperature is set at 70 °C, and the time is set at 4 hours.

[0097] Step 8: Freeze-dry the prepolymerized CNT / MXene / CCS / PEI mixed solution to obtain a CNT / MXene / CCS / PEI aerogel.

[0098] First, freeze the six-well mold containing the prepolymerized CNT / MXene / CCS / PEI mixed solution at -55 °C for 18 h to obtain a CNT / MXene / CCS / PEI hydrogel;

[0099] Then, freeze-dry the CNT / MXene / CCS / PEI hydrogel to obtain a CNT / MXene / CCS / PEI aerogel.

[0100] The freeze-drying temperature is -70 °C, and the duration is 84 hours.

[0101] Compared with the commercial electromagnetic shielding material (20 dB), the electromagnetic shielding effectiveness of the CNT / MXene / CCS / PEI composite aerogel prepared in Example 2 is 37.56 dB, corresponding to an increase of 87.8%.

[0102] Example 3

[0103] The preparation method of an adaptive electromagnetic interference-resistant composite material of the present invention is as follows:

[0104] Step 1: Use the replacement HF method (a mixture of LiF and HCl) to etch and remove the Al layer in the Ti3AlC2 precursor to prepare accordion-like Ti3C2T x MXene powder. The specific steps are as follows:

[0105] First, fully mix LiF and HCl to obtain a LiF / HCl solution, and then slowly add the MAX phase precursor powder to the LiF / HCl mixed solution under ice bath conditions to obtain a mixed solution;

[0106] The mass ratio of LiF, HCl to the MAX phase precursor powder is 1:20:1.

[0107] The purity of the MAX phase precursor powder is 98%, and the particle size of the MAX phase precursor powder is 500 mesh.

[0108] Then, continuously magnetically stir the mixed solution at 45 °C for 48 hours to obtain a multi-layer Ti3C2T x suspension, and then repeatedly centrifuge and wash with deionized water until the solution pH is 7 to obtain accordion-like Ti3C2T x precipitate; when centrifuging and washing, the centrifugation rate is 4000 r / min.

[0109] Step 2: Perform ultrasonic oscillation, centrifugal washing and freeze-drying on the accordion-like powder to prepare single (few)-layer Ti3C2T x MXene powder. The specific steps are as follows:

[0110] First, disperse the multi-layer Ti3C2T x precipitate in deionized water, ultrasonically treat for 20 min to promote the peeling of multi-layer MXene, and then continue to centrifuge at a rate of 4000 r / min for 20 min for several cycles, take the supernatant to obtain a few-layer MXene dispersion;

[0111] Then, perform freeze-drying on the obtained few-layer MXene dispersion in a freeze dryer to obtain few-layer MXene powder.

[0112] Step 3: Dissolve chitosan (CCS) in deionized water to prepare an aqueous solution with a CCS concentration of 2 wt%. The specific steps are as follows:

[0113] Under magnetic stirring, fully dissolve carboxymethyl chitosan (CCS) in deionized water to prepare a CCS aqueous solution. The magnetic stirring speed is 800 rpm / min and the duration is 2 hours.

[0114] Step 4: Add a certain amount of KH560 to the 2 wt% CCS aqueous solution for ultrasonic dispersion to obtain a KH560 / CCS mixed solution. The specific steps are as follows:

[0115] KH560 was added to the above-mentioned CCS aqueous solution and magnetically stirred at room temperature to obtain a uniformly mixed KH560 / CCS solution. The magnetic stirring speed was 800 rpm / min and the duration was 2 hours.

[0116] Step 5: An appropriate amount of PEI was added to the KH560 / CCS mixed solution and magnetically stirred to obtain a KH560 / CCS / PEI mixed solution. The specific steps are as follows:

[0117] Polyethyleneimine (PEI) was added to the uniformly mixed KH560 / CCS mixed solution, and through ultrasonic stirring, a uniformly mixed KH560 / CCS / PEI solution was obtained. The ultrasonic stirring power was 360 W and the duration was 1 hour.

[0118] Step 6: An appropriate amount of CNT and few-layer MXene were added to the above-mentioned KH560 / CCS / PEI mixed solution and ultrasonically stirred to prepare a composite precursor solution. The specific steps are as follows:

[0119] An appropriate amount of carboxylated carbon nanotubes (CNT) and MXene were added to the above-mentioned uniformly mixed KH560 / CCS / PEI mixed solution, and ultrasonic stirring was used to uniformly disperse them. The ultrasonic stirring power was 500 W and the duration was 3 hours. The mass ratio of CCS, PEI, CNT, MXene and deionized water was 1:0.4:1:1:49.

[0120] Step 7: The composite precursor solution was transferred to a mold, and then the mold was placed in an oven for crosslinking to obtain a pre-polymerized CNT / MXene / CCS / PEI mixed solution. The specific steps are as follows:

[0121] First, the mixed solution was equally divided and transferred to a six-well mold;

[0122] Then, the mold containing the mixed solution was transferred to an oven to promote crosslinking. Through crosslinking, a pre-polymerized CNT / MXene / CCS / PEI mixed solution was obtained. The oven temperature was set at 80 °C and the time was set at 5 hours.

[0123] Step 8: The pre-polymerized CNT / MXene / CCS / PEI mixed solution was freeze-dried to obtain a CNT / MXene / CCS / PEI aerogel.

[0124] First, the six-well mold containing the pre-polymerized CNT / MXene / CCS / PEI mixed solution was frozen at -60 °C for 24 h to obtain a CNT / MXene / CCS / PEI hydrogel;

[0125] Then, the CNT / MXene / CCS / PEI hydrogel was freeze-dried to obtain the CNT / MXene / CCS / PEI aerogel. The freeze-drying temperature was -80 °C and the duration was 96 hours.

[0126] Compared with the commercial electromagnetic shielding material (20 dB), the electromagnetic shielding effectiveness of the CNT / MXene / CCS / PEI composite aerogel prepared in Example 3 was 57.96 dB, corresponding to a 189.8% increase.

[0127] The composite aerogels prepared in Examples 1-3 of the present invention showed different performances at different MXene contents. As Figure 1 shown, the SE of the CNT / MXene / CCS / PEI composite aerogel T Figure. As the content of MXene in the CNT / MXene / CCS / PEI composite aerogel increased, the electromagnetic shielding effectiveness also increased. This was because a more perfect conductive network was formed inside the composite aerogel at high filler contents. Figure 2 and Figure 3 were the SE of the CNT / MXene / CCS / PEI composite aerogel at different MXene contents A and SE R Figure, respectively. It can be seen from the figure that:

[0128] (1) Both SE A and SE R were enhanced with the increase of MXene content. The increase of SE A was mainly due to the enhanced multiple reflection and scattering inside the composite aerogel at high MXene contents, and the increase of SE R was mainly attributed to the serious impedance mismatch caused by high MXene contents.

[0129] (2) By comparing SE A and SE R it can be found that: at the same MXene content, SE A was much higher than SE R , indicating that SE A was the main contribution source of SE T . Figure 4 was the current signal response curve of the composite aerogel under different strains. It can be seen that: as the strain increased, the current signal increased. The signal difference between low strain (such as 10%) and high strain (such as 90%) was significant, and different magnitudes of strain could be clearly distinguished, meeting the application requirements of a sensor in practice. At the same time, in the high strain range (70%, 90%), the rising slope and amplitude of the signal were significantly higher than those of low strain, indicating that the prepared composite aerogel could be used as a sensor to effectively distinguish a wide range of strains.

[0130] The mechanism of action of the method of the present invention is as follows:

[0131] (1) In terms of electromagnetic shielding: When electromagnetic waves are incident on the CNT / MXene / CCS / PEI composite aerogel with a three-dimensional conductive network structure, the synergistic effect of the porous structure on the material surface and the three-dimensional conductive network can significantly optimize the impedance matching performance, making the incident electromagnetic waves easily enter the interior of the composite aerogel for dissipation and attenuation. For the electromagnetic waves entering the interior, the internal multiple reflection scattering of the pore walls and the coupling effect of the multi-dimensional (one-dimensional CNT and two-dimensional MXene) conductive network strengthen the dissipation of electromagnetic wave energy, dissipating the electromagnetic waves to the greatest extent. In addition, the introduction of MXene and CNT forms a large number of heterogeneous interfaces inside the composite aerogel, inducing the generation of polarization losses (interface polarization and dipole polarization), and further attenuating the electromagnetic waves. The improved impedance matching and the combined action of various dissipation mechanisms endow the prepared composite aerogel with excellent electromagnetic shielding effectiveness.

[0132] (2) In terms of flexible sensing: The silanol generated by the hydrolysis of KH560 undergoes dehydration condensation to form siloxane. Under the condition of 60 degrees Celsius, the siloxane undergoes a ring-opening reaction to chemically crosslink with PEI and CCS. At the same time, hydrogen bond forces are generated between the carboxyl group of CNT-COOH and the amino group of PEI and the hydroxyl group of CCS, enhancing the structural strength of the composite aerogel. In addition, the amino groups present on the surface of PEI are easily protonated and present a cationic state. Under the action of electrostatic adsorption, the conductive fillers (CNT and MXene) will be more firmly combined with the polymer matrix, contributing to the improvement of the electrical properties and mechanical strength of the composite aerogel, and is expected to be applied as a compressive flexible strain sensor in practice.

[0133] Comparative Example 1

[0134] The difference between Comparative Example 1 and Example 1 is only that there is no addition of Ti3C2T x MXene powder.

[0135] This comparative example provides a preparation method for an adaptive electromagnetic interference-resistant composite material, and the specific steps are as follows:

[0136] Step 1, dissolve chitosan (CCS) in deionized water to prepare an aqueous solution with a CCS concentration of 2 wt%, and the specific steps are as follows:

[0137] Under the action of magnetic stirring, carboxymethyl chitosan (CCS) is fully dissolved in deionized water to prepare a CCS aqueous solution. The magnetic stirring speed is 500 rpm / min, and the duration is 1 hour.

[0138] Step 2, add a certain amount of KH560 to the 2 wt% CCS aqueous solution for ultrasonic dispersion to obtain a KH560 / CCS mixed solution, and the specific steps are as follows:

[0139] KH560 was added to the above CCS aqueous solution and magnetically stirred at room temperature to obtain a uniformly mixed KH560 / CCS solution. The magnetic stirring speed was 500 rpm / min and the duration was 1 hour.

[0140] Step 3: An appropriate amount of PEI was added to the KH560 / CCS mixed solution and magnetically stirred to obtain a KH560 / CCS / PEI mixed solution. The specific steps are as follows:

[0141] Polyethyleneimine (PEI) was added to the uniformly mixed KH560 / CCS mixed solution, and a uniformly mixed KH560 / CCS / PEI solution was obtained through ultrasonic stirring. The ultrasonic stirring power was 360 W and the duration was 1 hour.

[0142] Step 4: An appropriate amount of CNT was added to the above KH560 / CCS / PEI mixed solution and ultrasonically stirred to prepare a composite precursor solution. The specific steps are as follows:

[0143] An appropriate amount of carboxylated carbon nanotubes (CNT) was added to the above uniformly mixed KH560 / CCS / PEI mixed solution and uniformly dispersed through ultrasonic stirring. The ultrasonic stirring power was 360 W and the duration was 2 hours. The mass ratio of CCS, PEI, CNT, and deionized water was 1:0.4:1:0.5:49.

[0144] Step 5: The composite precursor solution was transferred to a mold, and then the mold was placed in an oven for crosslinking to obtain a pre-polymerized CNT / CCS / PEI mixed solution. The specific steps are as follows:

[0145] First, the mixed solution was equally divided and transferred into a six-well mold;

[0146] Then, the mold containing the mixed solution was transferred to an oven to promote crosslinking. Through crosslinking, a pre-polymerized CNT / CCS / PEI mixed solution was obtained. The oven temperature was set at 60 °C and the time was set at 3 hours.

[0147] Step 6: The pre-polymerized CNT / CCS / PEI mixed solution was freeze-dried to obtain a CNT / CCS / PEI aerogel.

[0148] First, the six-well mold containing the pre-polymerized CNT / CCS / PEI mixed solution was frozen at -50 °C for 12 h to obtain a CNT / CCS / PEI hydrogel;

[0149] Then, the CNT / CCS / PEI hydrogel was freeze-dried to obtain a CNT / CCS / PEI aerogel.

[0150] The freeze-drying temperature is -60 degrees Celsius and the duration is 72 hours.

[0151] The electromagnetic shielding effectiveness of the CNT / CCS / PEI composite aerogel prepared in Comparative Example 1 is 7.99 dB, which fails to meet the requirements of commercial electromagnetic shielding applications (20 dB).

[0152] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced by the present invention.

Claims

1. A preparation method of an adaptive electromagnetic interference resistant composite material, characterized in that, It includes the following steps: Step 1, etching and removing the Al layer in the Ti3AlC2 precursor with a mixed solution of LiF and HCl to prepare Ti3C2T x MXene powder; Step 2: Ultrasonically oscillate, centrifuge and wash, and freeze-dry the Ti3C2T x MXene powder to prepare few-layer Ti3C2T x MXene powder with 2 - 10 layers; Step 3: Dissolve chitosan in deionized water to prepare a chitosan aqueous solution with a concentration of 2 wt%. Step 4: Add an appropriate amount of silane coupling agent into the 2 wt% chitosan aqueous solution and perform ultrasonic dispersion to obtain a silane coupling agent / chitosan mixed solution. Step 5: Add an appropriate amount of polyethyleneimine into the silane coupling agent / chitosan mixed solution and perform magnetic stirring to obtain a silane coupling agent / chitosan / polyethyleneimine mixed solution. Step six, add an appropriate amount of carbon nanotubes and Ti3C2T x MXene powder into the silane coupling agent / chitosan / polyethyleneimine mixed solution prepared in step five, and perform ultrasonic stirring to obtain a precursor solution of the composite material; Step 7: Transfer the precursor solution to a mold, and then place the mold in an oven to cause the cross-linking reaction of the precursor solution, thereby obtaining a pre-polymerized carbon nanotube / Ti3C2T x MXene powder / chitosan / polyethyleneimine mixed solution; Step eight, subject the pre-polymerized carbon nanotube / Ti3C2T x MXene powder / chitosan / polyethyleneimine mixed solution to freeze drying to obtain a carbon nanotube / Ti3C2T x MXene powder / chitosan / polyethyleneimine mixed solution aerogel.

2. The preparation method of an adaptive electromagnetic interference resistant composite material according to claim 1, wherein, The said Step 1 has the following steps: a) Thoroughly mix LiF and HCl solution, and then slowly add the Ti3AlC2 precursor powder under ice bath conditions to obtain a mixed solution. Among them, the mass ratio of LiF, HCl, and Ti3AlC2 precursor powder is 1:15 - 20:

1. The purity of the Ti3AlC2 precursor powder is 98%, and the particle size is 200 - 500 mesh. b) Continuously stir the mixed solution prepared in step a) magnetically for 24 to 48 hours at 35 to 45 °C to obtain a multi-layer Ti3C2T x suspension, and then repeatedly centrifuge and wash it with deionized water until the solution pH is 6 to 7 to obtain Ti3C2T x precipitate, which is the Ti3C2T x MXene powder; Among them, during centrifugal washing, the centrifugal rate is 3500 - 4000 r / min.

3. The preparation method of an adaptive electromagnetic interference resistant composite material according to claim 1, wherein The said Step 2 has the following steps: a) Disperse the Ti3C2T x MXene powder in deionized water and ultrasonically treat it for 15 - 20 min to promote the exfoliation of the Ti3C2T x MXene powder, then continue to centrifuge it at a rate of 3500 - 4000 r / min for 15 - 20 min for several cycles, take the supernatant to obtain a few-layer Ti3C2T x MXene powder dispersion; b) The obtained few-layer Ti3C2T x MXene powder dispersion is freeze-dried in a freeze dryer to obtain few-layer Ti3C2T x MXene powder.

4. The preparation method of an adaptive electromagnetic interference resistant composite material according to claim 1, wherein In the said Step 3, the chitosan is carboxymethyl chitosan. Under magnetic stirring, fully dissolve the carboxymethyl chitosan in deionized water to prepare a carboxymethyl chitosan aqueous solution. Among them, the magnetic stirring speed is 500 - 800 rpm / min, and the duration is 1 - 2 hours.

5. The preparation method of an adaptive electromagnetic interference resistant composite material according to claim 1, characterized in that, In the said Step 4, the silane coupling agent is KH560, and the addition amount of KH560 is 5% - 10% of the mass of chitosan. Add KH560 into the carboxymethyl chitosan aqueous solution prepared in Step 3 and perform magnetic stirring at room temperature to obtain a KH560 / chitosan mixed solution. Among them, the magnetic stirring speed is 500 - 800 rpm / min, and the duration is 1 - 2 hours.

6. The preparation method of an adaptive electromagnetic interference resistant composite material according to claim 1, characterized in that, In the said Step 5, add polyethyleneimine into the uniformly mixed KH560 / chitosan mixed solution and perform ultrasonic stirring to obtain a uniform KH560 / chitosan / polyethyleneimine mixed solution. Among them, the addition amount of the polyethyleneimine is 40% of the mass of chitosan, the ultrasonic stirring power is 360 W, and the duration is 1 hour.

7. The preparation method of an adaptive electromagnetic interference resistant composite material according to claim 6, wherein In the sixth step, an appropriate amount of carboxylated carbon nanotubes and Ti3C2T x MXene powder are added to the above-mentioned homogeneous KH560 / chitosan / polyethyleneimine mixed solution, and they are uniformly dispersed by ultrasonic stirring; Among them, the ultrasonic stirring power is 360 - 500 W, and the duration is 2 - 3 hours. Chitosan, polyethyleneimine, carbon nanotubes, Ti3C2T x The mass ratio of MXene powder and deionized water is 1:0.4:1:0.1 to 1:

49.

8. The preparation method of an adaptive electromagnetic interference resistant composite material according to claim 1, characterized in that, The said Step 7 has the following steps: a) Equally transfer the precursor solution into a six-well mold. b) Transfer the mold containing the precursor solution to an oven to promote crosslinking. Through crosslinking, a pre-polymerized carbon nanotube / Ti3C2T x MXene powder / chitosan / polyethyleneimine mixed solution is obtained; Among them, the oven temperature is set at 60 - 80 degrees Celsius, and the time is set at 3 - 5 hours.

9. The preparation method of an adaptive electromagnetic interference resistant composite material according to claim 1, characterized in that, The said Step 8 has the following steps: a) Place the six-well mold containing the pre-polymerized carbon nanotube / Ti3C2T x MXene powder / chitosan / polyethyleneimine mixed solution in a freezer at -50 to -60 °C for 12 to 24 h to obtain a carbon nanotube / Ti3C2T x MXene powder / chitosan / polyethyleneimine hydrogel; b) Carbon nanotubes / Ti3C2T x The MXene powder / chitosan / polyethyleneimine hydrogel is freeze-dried to obtain carbon nanotubes / Ti3C2T x MXene powder / chitosan / polyethyleneimine aerogel; Among them, the freeze-drying temperature is -60 - 80 degrees Celsius, and the duration is 72 - 96 hours.

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