MXene@CoNi composite aerogel as well as preparation method and application thereof

Abstract

The present application relates to a kind of MXene@CoNi composite aerogel and its preparation method and application.High-efficiency absorbent Ti3CNT x MXene and one-dimensional CoNi chain are dispersed into gelatin to prepare MXene@CoNi composite aerogel.On the one hand, the conductive MXene nanosheet is fully integrated with gelatin, which can make the MXene aerogel have excellent dielectric properties. On the other hand, the one-dimensional CoNi chain produced by magnetic field-induced growth shows high aspect ratio and large specific surface area, which can produce different polarization and increase the propagation path of electromagnetic waves. In addition, the macroscopic three-dimensional morphology of MXene@CoNi composite aerogel can effectively build a conductive network and strengthen the multi-reflection ability of incident electromagnetic waves. In addition, infrared thermal imaging and stress-strain testing show that the composite aerogel has excellent infrared stealth performance, thermal insulation performance and excellent mechanical properties. This study paves the way for the design of the next generation of microwave absorbing materials, which has great potential for multifunctional applications.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic absorption material preparation technology in the field of functional materials, and in particular to an MXene@CoNi composite aerogel, its preparation method and application. Background Technology

[0002] With the advent of the artificial intelligence era, electromagnetic pollution caused by the widespread use of wireless communication devices has become a serious environmental problem. Therefore, exploring novel and efficient electromagnetic wave absorbing materials to solve this problem is imperative. To date, efficient electromagnetic wave absorbing materials capable of effectively converting electromagnetic waves into heat and other forms of energy have received widespread attention. Unfortunately, traditional single-component dielectric or ferrite materials have drawbacks such as high density, weak absorption performance, and narrow absorption bandgap, which greatly limit their practical application in electromagnetic wave absorption and cannot meet the comprehensive performance requirements of absorbing materials. Therefore, the development of high-performance absorbing materials is essential.

[0003] Generally, the microwave absorption performance of a material largely depends on two parameters: the complex dielectric constant and the complex permeability. Therefore, cleverly designing special structures with customized electromagnetic parameters is a feasible strategy to improve their microwave absorption performance. For special structures, it has been found that microwave absorbing materials with three-dimensional porous, hollow, core-shell, yolk-shell, or core-sheath structures can maximize microwave energy dissipation and impedance matching. Aerogels, with their large internal free space, light weight, porous structure, and customization capabilities, have attracted researchers' attention. The numerous pores in aerogels facilitate impedance matching based on the effective medium and provide a large number of reflection points for electromagnetic wave attenuation. The large heterogeneous interfaces within the pores enhance the interface effect, and the interconnected structural units form a conductive network, ultimately promoting dielectric loss capability. Furthermore, the low density of aerogels with continuous three-dimensional structures in the matrix implies an ultra-low fill rate. Therefore, macroscopically interconnected three-dimensional aerogels have great potential to be developed as novel electromagnetic wave absorbing materials.

[0004] As a new member of the sheet-like two-dimensional (2D) materials family, MXenes, a large class of two-dimensional early transition metal carbides / nitrides discovered in 2011, have attracted significant research attention. The general formula for MXenes is Mn + 1XnTx, where "M" represents an early transition metal, "X" represents carbon and / or nitrogen, and "Tx" represents surface functional groups. Benefiting from their excellent electrical conductivity, abundant surface functional groups, and strong hydrophilicity, MXenes can be a promising candidate material for constructing highly efficient microwave absorbers. Studies have shown that the surface morphology, size, and crystal structure of magnetic materials can effectively tune magnetic loss capabilities.

[0005] However, there are currently not many solutions for combining MXenes with magnetic materials. Therefore, developing a composite material that combines MXenes and magnetic materials is of great significance for the development and production of microwave absorbing materials. Summary of the Invention

[0006] To develop more electromagnetic wave absorbing materials, this invention provides an MXene@CoNi composite aerogel, its preparation method, and its applications.

[0007] The composite aerogel of this invention has excellent electromagnetic wave absorption performance, and can be prepared into a high-performance and stable electromagnetic wave absorbing material through simple directional freeze-drying technology and magnetic field heat treatment process. At the same time, the excellent thermal insulation and mechanical properties of the MXene@CoNi composite aerogel have the potential to withstand complex and harsh environments.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] This invention provides an MXene@CoNi (also known as Ti3CNT) x The preparation method of (@CoNi or M@CN) composite aerogel includes the following steps:

[0010] (1) Preparation of MXene nanosheets;

[0011] (2) Preparation of one-dimensional magnetic CoNi chains;

[0012] (3) MXene nanosheets, one-dimensional magnetic CoNi chains and gelatin solution were fully assembled by directional freezing and freeze drying to prepare MXene@CoNi composite aerogel.

[0013] In one embodiment of the present invention, the method for preparing MXene nanosheets in step (1) is as follows:

[0014] Multilayer Ti3CN MXene was prepared from MAX raw material using the LiF-HCl etching method, and then transparent MXene nanosheets were prepared by ultrasonic exfoliation.

[0015] In one embodiment of the present invention, the method for preparing MXene nanosheets in step (1) includes the following steps:

[0016] (1.1) Add Ti3AlCN to the lithium fluoride and concentrated hydrochloric acid solution, ensuring the raw material mass ratio is: Ti3AlCN: lithium fluoride: hydrochloric acid = 1:(0.95~1.05):(10~12); stir at room temperature;

[0017] (1.2) After keeping the solution obtained in step (1.1) at 40-50℃ for 20-30 hours, cool it to room temperature, and then centrifuge the liquid to obtain the precipitate after centrifugation;

[0018] (1.3) The product obtained in step (1.2) is first washed with deionized water until the pH value of the supernatant liquid after centrifugation is greater than 5;

[0019] (1.4) Transfer the product obtained in step (4.3) into a gas washing bottle, place the gas washing bottle in an ultrasonic machine, and perform ultrasonication in an argon atmosphere;

[0020] (1.5) Centrifuge the product obtained in step (1.4), collect the suspension in the centrifuge tube, and refrigerate it to obtain a suspension containing MXene nanosheets.

[0021] In one embodiment of the present invention, the concentration of hydrochloric acid in step (1.1) is 10-15 mol / L, for example, 12 mol / L.

[0022] In one embodiment of the present invention, in step (1.1), the stirring time is 1-10 minutes, for example, 5 minutes.

[0023] In one embodiment of the present invention, in step (1.4), the ultrasonication is performed at a reaction temperature of 0 to 4°C for 1 hour.

[0024] In one embodiment of the present invention, in step (1.5), the centrifugation is performed at room temperature, at a speed of 3500 rpm / min, for a duration of 1 hour. For refrigeration, the product can be placed in a refrigerator at a temperature of 0-10°C.

[0025] In one embodiment of the present invention, the method for preparing one-dimensional magnetic CoNi chains in step (2) is as follows: cobalt chloride hexahydrate, nickel chloride hexahydrate, hexamethylimine and sodium hydroxide are dissolved in 1,2-propanediol, and one-dimensional magnetic CoNi chains with high aspect ratio and large specific surface area are prepared under the action of magnetic field induction.

[0026] In one embodiment of the present invention, the method for preparing a one-dimensional magnetic CoNi chain in step (2) specifically includes the following steps:

[0027] (2.1) Add nickel chloride hexahydrate, cobalt chloride hexahydrate and hexamethylenetetramine in a molar ratio of 1:1:3 to 1,2-propanediol, stir and sonicate to fully dissolve and mix them evenly to obtain solution A;

[0028] (2.2) Add NaOH particles to solution A at 120℃, wherein the molar ratio of NaOH particles to nickel chloride hexahydrate is 1:2; stir thoroughly to mix thoroughly until it turns dark blue, thus obtaining solution B;

[0029] (2.3) Induction process of field heat treatment: Solution B is placed in a hydrothermal reactor, and then the hydrothermal reactor is placed in the magnetic field heat treatment furnace cavity for reaction;

[0030] (2.4) The final product obtained from the reaction was collected by centrifugation, washed with deionized water and anhydrous ethanol respectively, and dried to obtain a one-dimensional magnetic CoNi chain.

[0031] In one embodiment of the present invention, in step (2.3), the reaction conditions are 170°C for 20 hours.

[0032] In one embodiment of the present invention, in step (2.4), the product is rinsed three times with deionized water, then washed three times with anhydrous ethanol, and dried in a vacuum oven at 50°C for 24 hours.

[0033] In one embodiment of the present invention, in step (3), the gelatin solution is prepared according to the ratio of 1g gelatin particles dispersed in 50ml of deionized water, and the gelatin solution is an approximately transparent solution obtained after heating.

[0034] In one embodiment of the present invention, in step (3), the mass ratio of the suspension containing MXene nanosheets to the CoNi magnetic chain is 2:1. After adding the gelatin solution, the total concentration of MXene nanosheets and one-dimensional magnetic CoNi chains is 10-20 mg / mL, and the mass ratio of MXene@CoNi in the mixed solution is 30%.

[0035] In one embodiment of the present invention, in step (3), the method of directional freezing and freeze drying refers to: pouring the mixed solution into a copper-based polytetrafluoroethylene mold and placing it in a cold trap at -90°C for directional freezing; then placing the frozen sample into a freeze dryer and drying it at -90°C for 72 hours to finally obtain MXene@CoNi composite aerogel.

[0036] In one embodiment of the present invention, an MXene@CoNi (also known as Ti3CNT) is also provided. x A more specific preparation method for (@CoNi or M@CN) composite aerogels includes the following steps:

[0037] (1) Add Ti3AlCN to the lithium fluoride and concentrated hydrochloric acid solution, ensuring the raw material ratio (mass ratio) is Ti3AlCN:lithium fluoride:hydrochloric acid (12 mol / L) = 1:(0.95~1.05):(10~12); stir for 5 minutes at room temperature;

[0038] (2) Transfer the solution obtained in step (1) into an oil bath and keep it at 40-50°C for 24 hours. Then cool it to room temperature and centrifuge the liquid to obtain the precipitate after centrifugation.

[0039] (3) Wash the product obtained in step (2) with deionized water until the pH value of the supernatant liquid after centrifugation is greater than 5;

[0040] (4) Transfer the product obtained in step (3) into a gas washing bottle, place the gas washing bottle in an ultrasonic machine, atmosphere: argon, reaction temperature: 0~4℃, ultrasonic time: 1h;

[0041] (5) Add the product obtained in step (4) evenly and in equal amounts to centrifuge tubes, arrange them symmetrically, time: 1 h, rotation speed: 3500 rpm / min, temperature: room temperature. Collect the suspension in the centrifuge tubes and refrigerate them in a refrigerator;

[0042] (6) Add 0.6 mmol of nickel chloride hexahydrate, 0.6 mmol of cobalt chloride hexahydrate and 1.8 mmol of hexamethylenetetramine to 60 ml of 1,2-propanediol, stir and sonicate for 25 minutes to fully dissolve and mix evenly to obtain solution A;

[0043] (7) Place the well-stirred mixed solution into an oil bath at 120 degrees Celsius, add 0.3 mmol of NaOH particles to the mixed solution, stir thoroughly for 15 minutes to make it fully mixed and turn dark blue, and obtain solution B;

[0044] (8) Using the induction process of magnetic field heat treatment, the mixed solution B is placed in a hydrothermal reactor, and then the hydrothermal reactor is placed in the magnetic field heat treatment furnace cavity and reacted at 170°C for 20 hours.

[0045] (9) The final product obtained from the reaction was collected by centrifugation, washed three times with deionized water, then washed three times with anhydrous ethanol, and dried in a vacuum oven at 50°C for 24 hours.

[0046] (10) Disperse 1g of purchased gelatin granules in 50ml of deionized water and allow them to swell fully for one hour.

[0047] (11) The mixed solution that has swollen for one hour is stirred thoroughly in an oil bath at 60°C to obtain a nearly transparent solution C.

[0048] (12) A certain amount of Ti3CNT x MXene nanosheet suspension and CoNi magnetic chains (mass ratio: 2:1) were added to a gelatin solution to achieve a total concentration of 15 mg / mL. The mass ratio of M@CN in the mixed solution was 30%.

[0049] (13) Pour the mixed solution into a copper-based polytetrafluoroethylene mold and place it in a cold trap at -90°C for directional freezing; then place the frozen sample in a freeze dryer and dry it at -90°C for 72 hours to finally obtain MXene@CoNi composite aerogel.

[0050] The present invention further provides MXene@CoNi composite aerogel prepared based on the above preparation method.

[0051] The present invention further provides an application of the MXene@CoNi composite aerogel prepared by the above preparation method for electromagnetic wave absorption.

[0052] This invention utilizes a convenient one-way cryogenic assembly strategy, freely fusing gelatin as a "chemical glue" to incorporate the highly efficient absorbent Ti3CNT. x MXene and one-dimensional CoNi chains were dispersed in gelatin to prepare MXene@CoNi composite aerogels. On one hand, the conductive MXene nanosheets are fully integrated with gelatin, giving the MXene aerogel excellent dielectric properties. On the other hand, the one-dimensional CoNi chains, fabricated through magnetic field-induced growth, exhibit a high aspect ratio and large specific surface area, which can generate different polarizations and increase the propagation path of electromagnetic waves. Furthermore, the macroscopic three-dimensional morphology of the MXene@CoNi composite aerogel can effectively construct a conductive network, enhancing the multi-reflection capability of incident electromagnetic waves. Experimental tests show that the MXene@CoNi composite aerogel exhibits excellent MA performance in the 2-18 GHz range, achieving a minimum reflection loss of -55.37 dB at 13.36 GHz with a thickness of 2.01 mm. More importantly, the MXene@CoNi composite aerogel also has an effective bandwidth of 6.88 GHz (from 11.12 GHz to 18 GHz) at a thickness of 1.91 mm, covering the entire Ku-band. Furthermore, infrared thermal imaging and stress-strain testing revealed that this composite aerogel possesses superior infrared stealth properties, thermal insulation properties, and excellent mechanical properties. This research paves the way for the design of next-generation microwave absorbing materials with enormous potential for multifunctional applications.

[0053] This invention utilizes one-dimensional magnetic materials, which offer the following advantages: First, compared to granular morphology, one-dimensional magnetic nanostructures exhibit stronger shape anisotropy, thus resulting in a higher Snoek-limiting frequency. Second, the high aspect ratio of the magnetic flux linkages allows for the formation of a conductive network. Third, the large specific surface area facilitates the expansion of heterogeneous interfaces, significantly promoting dielectric polarization. Therefore, by leveraging the synergistic effects and unique structural advantages of multi-component materials, this novel electromagnetic wave absorbing material can be endowed with excellent electromagnetic dissipation capabilities and diverse functionalities.

[0054] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0055] This invention assembles MXene@CoNi composite aerogels with excellent electromagnetic wave absorption properties through a simple magnetic field heat treatment, directional freezing, and freeze-drying process. In particular, the process parameters can effectively adjust the absorption performance and mechanical strength of the composite aerogel, ultimately enabling it to withstand complex and harsh environments. This significantly advances industrial production and is of great importance for the widespread application and development of microwave absorbing materials. Attached Figure Description

[0056] Figure 1 Compare the XRD patterns of Examples 1-3 and Example 1;

[0057] Figure 2 Compare the SEM and TEM images of Examples 1-2 and Example 1 (small image of Example 3);

[0058] Figure 3 Compare the absorption performance of Examples 1-3 with that of Example 1;

[0059] Figure 4 The thermal insulation and mechanical properties of the embodiments. Detailed Implementation

[0060] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0061] This invention provides the following specific embodiments, discloses the performance of various combined embodiments, and analyzes the role of each experimental parameter in the system. Therefore, it should be considered that this patent specifically describes and discloses all possible combinations of the described technical solutions.

[0062] Comparative Example 1

[0063] In this comparative example, the product obtained is MXene nanosheets prepared by an etching method.

[0064] The preparation method of MXene nanosheets is as follows:

[0065] (1) Add Ti3AlCN to the lithium fluoride and concentrated hydrochloric acid solution, ensuring the raw material ratio (mass ratio) is 1:1:11; stir for 5 minutes at room temperature.

[0066] (2) Transfer the solution obtained in step (1) into an oil bath and keep it at 45°C for 24 hours. Then cool it to room temperature and centrifuge the liquid to obtain the precipitate after centrifugation.

[0067] (3) Wash the product obtained in step (2) with deionized water until the pH value of the supernatant liquid after centrifugation is greater than 5;

[0068] (4) Transfer the product obtained in step (3) into a gas washing bottle, place the gas washing bottle in an ultrasonic machine, atmosphere: argon, reaction temperature: 4℃, ultrasonic time: 1h;

[0069] (5) Add the product obtained in step (4) evenly and in equal amounts to centrifuge tubes, arrange them symmetrically, time: 1 h, rotation speed: 3500 rpm / min, temperature: room temperature. Collect the suspension in the centrifuge tubes and refrigerate them in a refrigerator to obtain MXene nanosheets.

[0070] The product obtained above was subjected to the following tests:

[0071] (A) Irradiation source was Cu-Kα respectively X-ray diffraction (XRD) is used to determine the crystal structure of a sample.

[0072] (B) The morphology of the samples was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively.

[0073] (C) Electromagnetic parameters, including the complex permittivity and complex permeability, were determined using a coaxial line method with a Siyi 3672B-S vector network analyzer within the frequency range of 2-18 GHz. Sample preparation: The product was uniformly dispersed in paraffin wax at a weight percentage of 10%, and then pressed into a ring (outer diameter: 7.0 mm, inner diameter: 3.04 mm).

[0074] Comparative Example 2

[0075] In this comparative example, the product obtained is a pure gelatin aerogel.

[0076] The preparation method of pure gelatin aerogel is as follows:

[0077] (1) Disperse 1g of purchased gelatin granules in 50ml of deionized water and allow them to swell fully for one hour.

[0078] (2) The mixed solution that has swollen for one hour is stirred thoroughly in an oil bath at 60°C to obtain a nearly transparent solution.

[0079] (3) Pour the solution into a fixed mold, freeze it completely at -96℃, and vacuum dry it for 72 hours using a freeze dryer to finally prepare pure gelatin aerogel;

[0080] The product obtained above was tested, and the testing methods and contents were exactly the same as those in Comparative Example 1.

[0081] Comparative Example 3

[0082] In this comparative example, the product obtained is a cobalt-nickel magnetic flux prepared by the spraying method.

[0083] The preparation method of cobalt-nickel magnetic flux is as follows:

[0084] (1) Add 0.6 mmol of nickel chloride hexahydrate, 0.6 mmol of cobalt chloride hexahydrate and 1.8 mmol of hexamethylenetetramine to 60 ml of 1,2-propanediol, stir and sonicate for 25 minutes to fully dissolve and mix evenly to obtain solution A;

[0085] (2) Place the well-stirred mixed solution into an oil bath at 120 degrees Celsius, add 0.3 mmol of NaOH particles to the mixed solution, stir thoroughly for 15 minutes to make it fully mixed and turn dark blue, and obtain solution B;

[0086] (3) Using the induction process of magnetic field heat treatment, the mixed solution B is placed in a hydrothermal reactor, and then the hydrothermal reactor is placed in the magnetic field heat treatment furnace cavity and reacted at 170°C for 20 hours.

[0087] (4) The final product obtained from the reaction was collected by centrifugation, washed three times with deionized water, then washed three times with anhydrous ethanol, and dried in a vacuum oven at 50°C for 24 hours to obtain the cobalt-nickel magnetic chain, i.e., the CoNi magnetic chain.

[0088] The product obtained above was tested, and the testing methods and contents were exactly the same as those in Comparative Example 1.

[0089] Example 1

[0090] This embodiment is an embodiment of the above comparative embodiments, Examples 1, 2, and 3.

[0091] In this embodiment, the product obtained is MXene@CoNi composite aerogel.

[0092] The preparation method of MXene@CoNi composite aerogel is as follows:

[0093] (1) Add Ti3AlCN to the lithium fluoride and concentrated hydrochloric acid solution, ensuring the raw material ratio (mass ratio) is 1:1:11; stir for 5 minutes at room temperature.

[0094] (2) Transfer the solution obtained in step (1) into an oil bath and keep it at 45°C for 24 hours. Then cool it to room temperature and centrifuge the liquid to obtain the precipitate after centrifugation.

[0095] (3) Wash the product obtained in step (2) with deionized water until the pH value of the supernatant liquid after centrifugation is greater than 5;

[0096] (4) Transfer the product obtained in step (3) into a gas washing bottle, place the gas washing bottle in an ultrasonic machine, atmosphere: argon, reaction temperature: 4℃, ultrasonic time: 1h;

[0097] (5) Add the product obtained in step (4) evenly and in equal amounts to centrifuge tubes, arrange them symmetrically, time: 1 h, rotation speed: 3500 rpm / min, temperature: room temperature. Collect the suspension in the centrifuge tubes and refrigerate them in a refrigerator;

[0098] (6) Add 0.6 mmol of nickel chloride hexahydrate, 0.6 mmol of cobalt chloride hexahydrate and 1.8 mmol of hexamethylenetetramine to 60 ml of 1,2-propanediol, stir and sonicate for 25 minutes to fully dissolve and mix evenly to obtain solution A;

[0099] (7) Place the well-stirred mixed solution into an oil bath at 120 degrees Celsius, add 0.3 mmol of NaOH particles to the mixed solution, stir thoroughly for 15 minutes to make it fully mixed and turn dark blue, and obtain solution B;

[0100] (8) Using the induction process of magnetic field heat treatment, the mixed solution B is placed in a hydrothermal reactor, and then the hydrothermal reactor is placed in the magnetic field heat treatment furnace cavity and reacted at 170°C for 20 hours.

[0101] (9) The final product obtained from the reaction was collected by centrifugation, washed three times with deionized water, then washed three times with anhydrous ethanol, and dried in a vacuum oven at 50°C for 24 hours.

[0102] (10) Disperse 1g of purchased gelatin granules in 50ml of deionized water and allow them to swell fully for one hour.

[0103] (11) The mixed solution that has swollen for one hour is stirred thoroughly in an oil bath at 60°C to obtain a nearly transparent solution C.

[0104] (12) A certain amount of Ti3CNTx MXene nanosheet suspension and CoNi magnetic chains (mass ratio: 2:1) were added to a gelatin solution to make the total concentration 15 mg / mL. The mass ratio of M@CN in the mixed solution was 30%.

[0105] (13) Pour the mixed solution into a copper-based polytetrafluoroethylene mold and place it in a cold trap at -90°C for directional freezing;

[0106] (14) The frozen sample was placed in a freeze dryer and dried at -90°C for 72 hours to finally obtain MXene@CoNi composite aerogel.

[0107] The product obtained above was tested, and the testing methods and contents were exactly the same as those in Comparative Example 1.

[0108] The phase changes of the materials obtained in Examples 1-3 and Example 1 are as follows: Figure 1 As shown, the microstructures of Comparative Examples 1-2 and Example 1 are as follows: Figure 2 As shown. The microwave absorption properties of the materials prepared in Examples 1-3 and Example 1 are compared as follows. Figure 3 As shown in Table 1. The thermal insulation and mechanical properties of Example 1 are as follows. Figure 4 As shown.

[0109] Table 1: Comparison of microwave absorption performance between Examples 1-3 and Example 1

[0110]

[0111] The symbols in Table 1 have the following meanings:

[0112] RL—Reflection Loss; RL min —Minimum reflection loss.

[0113] Phase analysis: Figure 1 XRD patterns of Comparative Example 1 (MXene), Comparative Example 3 (CoNi chain), and Example 1 (MXene@CoNi composite aerogel) are described. Comparative Example 1 (MXene) exhibits good sharpness at the (002) peak at 6.72°, indicating high crystallinity and good structural order. Since Comparative Example 2 (gelatin) is an amorphous component, its XRD data lacks characteristic peaks. Furthermore, Comparative Example 3 (CoNi chain) shows three strong peaks at 44.66°, 52.06°, and 76.58°, corresponding to the (111), (200), and (220) crystal planes, respectively, and its diffraction pattern is consistent with the cubic structures of Co (JCPDS No. 15-0806) and Ni (JCPDS No. 04-0850). For Example 1 (MXene@CoNi composite aerogel), characteristic peaks corresponding to the CoNi chain and Ti3CN MXene are displayed, indicating successful aerogel fabrication.

[0114] Morphological Change Analysis: The internal microstructure and detailed morphology of Comparative Example 1 (MXene), Comparative Example 2 (gelatin), Comparative Example 3 (CoNi chain), and Example 1 (MXene@CoNi composite aerogel) were observed using SEM and TEM. Figure 2 As shown in Figure a, Comparative Example 1 (MXene) exhibits a transparent, wrinkled film-like structure, indicating that MXene was successfully peeled from an accordion-like multilayer structure to a few-layer structure. Figure 2b describes the morphological characteristics of the synthesized comparative example 3 (CoNi chain). Under the guidance of an external magnetic field, spherical nanoparticles self-assembled to form one-dimensional CoNi chains. The length of the cobalt-nickel magnetic chains exceeds 100 micrometers, while the diameter of each nanoparticle unit is approximately 500 nanometers. Notably, the anisotropy, high aspect ratio, and large specific surface area of ​​the 1D CoNi chains are advantageous for enhancing the attenuation of incident electromagnetic wave energy. Figure 2 The image shows a SEM image of Example 1 (MXene@CoNi composite aerogel). From... Figure 2 As shown in image c, the cross-section perpendicular to the ice crystal growth direction exhibits a honeycomb morphology, while the cell walls in the longitudinal section are arranged vertically upwards in parallel. This can be attributed to the micropore formation mechanism; the MXene@CoNi composite hydrogel assembles cell walls during the unidirectional growth of ice crystals, forming a layered porous composite material with anisotropic structure after ice crystal sublimation. As for the cell walls, their distribution in the cross-section is random, exhibiting an isotropic structure in this direction. SEM images not only verify the structure of the aerogel in both the cross-section and longitudinal section but also further reveal the tight connection between the one-dimensional CoNi chains and the MXene nanosheets. Figure 2 e). The addition of magnetic nanochains enhances the magnetic loss capacity and interfacial polarization of the M@CN composite aerogel. Furthermore, the presence of Co, Ni, C, and Ti elements in Example 1 (MXene@CoNi composite aerogel) is further confirmed by related energy-dispersive X-ray spectroscopy (EDX). Figure 2 e). Therefore, it is promising to achieve excellent electromagnetic wave absorption performance by designing multidimensional and multi-component aerogels to create conductive networks and induce electromagnetic waves to reflect back and forth in porous interlaced structures.

[0115] Wave absorption performance analysis: Figure 3 The microwave absorption properties of Comparative Example 1 (MXene), Comparative Example 2 (gelatin), Comparative Example 3 (CoNi chain), and Example 1 (MXene@CoNi composite aerogel) are illustrated graphically. Figure 3 As shown in the upper right figure, the RLmin value of Comparative Example 2 (gelatin) is close to 0 because gelatin is a simple wave-transmitting material and does not possess electromagnetic wave absorption properties. In contrast, MXene exhibits unsatisfactory electromagnetic wave absorption performance (RL > -10dB) at the same paraffin filling rate, which can be attributed to the superior conductivity of MXene. Furthermore, as... Figure 3As shown in the lower left figure, the RLmin value of Comparative Example 3 (CoNi chain) is -17.16 dB at 5.68 GHz, with a thickness of 5 mm. Its widest EAB is only 2.2 GHz (from 4.00 GHz to 6.2 GHz), which can be attributed to the fact that magnetic loss does not play a dominant role in the electromagnetic wave absorption process. It is noteworthy that, benefiting from the synergistic effect of multi-component composite and multiple loss mechanisms, this composite aerogel exhibits significant electromagnetic wave absorption performance. Figure 3 (See bottom right figure). The example (MXene@CoNi composite aerogel) showed a minimum RL of -55.37 dB and an EAB of 4.48 GHz (from 10.64 to 15.12 GHz) at 13.36 GHz, with a matching thickness of only 2.01 mm. When the thickness was reduced to 1.91 mm, the EAB reached as high as 6.88 GHz (covering the entire Ku band) from 11.12 to 18 GHz. By comparing the electromagnetic wave absorption characteristics of all samples, it can be concluded that the MXene@CoNi composite aerogel not only has a good RL value but also a wide electromagnetic wave absorption bandwidth.

[0116] Thermal insulation and mechanical property analysis: The thermal insulation and mechanical properties of Example 1 (MXene@CoNi composite aerogel) are as follows: Figure 4 As shown. Figure 4 Figure a shows the stress-strain curves of MXene@CoNi composite aerogels with different concentrations. The strength of the aerogel increases with increasing density. When the density of the aerogel reaches 0.1 g / cm³... 3 At that time, its strength can reach 25 MPa (90% of compressive strain). Furthermore, Figure 4 b provides MXene@CoNi composite aerogel (ρ = 15 mg / cm³). 3 The compressive stress-strain curves under different strains show that when the strain reaches 80%, the maximum stress of the M@CN composite aerogel can reach 548.58 kPa, indicating that aerogels of a specific density have good impact resistance. In addition, the MXene@CoNi composite aerogel (ρ=15mg / cm³) exhibits good impact resistance. 3 It almost recovers to its original size after 35% compression and shows as low as 8.9% non-recoverable strain after 1000 cycles. Figure 4 c). The ultimate stress remained at 141.97 kPa, close to that of the first cycle (160.64 kPa), indicating that the macroscopic structure remained well maintained. Heat transfer is mainly divided into heat conduction, heat convection, and heat radiation, which depend on solid-phase, gas-phase, and radiative heat transfer, respectively. Figure 4Figures d and e illustrate the thermal insulation performance of Example 1 (MXene@CoNi aerogel). When the aerogel was placed on a constant-temperature heating platform with a surface temperature stable at approximately 85°C, three temperature monitoring points were collected at the top, middle, and bottom of the aerogel. Over time, the surface temperature of the MXene@CoNi composite aerogel (thickness d = 30 mm) remained almost unchanged, fluctuating around 25°C after 40 minutes of heating. This suggests that the fabricated aerogel possesses satisfactory long-term thermal insulation stability. Furthermore, based on the temperature monitoring point in the middle of the aerogel, the temperature consistently remained below 40°C. This is likely due to the aerogel's low density and porous structure hindering heat conduction. Therefore, it can be inferred that the composite aerogel exhibits good application prospects in harsh environments.

[0117] In summary, MXene@CoNi composite aerogels with excellent electromagnetic wave absorption properties can be assembled through simple magnetic field heat treatment, directional freezing, and freeze-drying processes. In particular, the process parameters can effectively adjust the absorption performance and mechanical strength of the composite aerogel, ultimately enabling it to withstand complex and harsh environments. This significantly advances industrial production and is of great importance for the widespread application and development of microwave absorbing materials.

[0118] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing MXene@CoNi composite aerogel, characterized in that, Includes the following steps: (1) Preparation of MXene nanosheets; (2) Preparation of one-dimensional magnetic CoNi chains; (3) MXene nanosheets, one-dimensional magnetic CoNi chains and gelatin solution were fully assembled by directional freezing and freeze drying to prepare MXene@CoNi composite aerogel; The method for preparing MXene nanosheets in step (1) includes the following steps: (1.1) Add Ti3AlCN to the lithium fluoride and concentrated hydrochloric acid solution, ensuring the raw material mass ratio is: Ti3AlCN: lithium fluoride: hydrochloric acid = 1: (0.95~1.05): (10~12); stir at room temperature; (1.2) After keeping the solution obtained in step (1.1) at 40~50℃ for 20-30 hours, cool it to room temperature, and then centrifuge the liquid to obtain the precipitate after centrifugation; (1.3) The product obtained in step (1.2) is first washed with deionized water until the pH value of the supernatant liquid after centrifugation is greater than 5; (1.4) Transfer the product obtained in step (1.3) into a gas washing bottle, place the gas washing bottle in an ultrasonic machine, and perform ultrasonication in an argon atmosphere; (1.5) Centrifuge the product obtained in step (1.4), collect the suspension in the centrifuge tube, refrigerate it, and obtain a suspension containing MXene nanosheets; The method for preparing one-dimensional magnetic CoNi chains in step (2) is as follows: cobalt chloride hexahydrate, nickel chloride hexahydrate, hexamethylimine and sodium hydroxide are dissolved in 1,2-propanediol, and one-dimensional magnetic CoNi chains are prepared under the induction of a magnetic field. In step (3), the mass ratio of the suspension containing MXene nanosheets to the CoNi magnetic chains is 2:

1. After adding the gelatin solution, the total concentration of MXene nanosheets and one-dimensional magnetic CoNi chains is 10-20 mg / mL, and the mass ratio of MXene@CoNi in the mixed solution is 30%. In step (3), the directional freezing and freeze-drying method refers to: pouring the mixed solution into a copper-based polytetrafluoroethylene mold and placing it in a cold trap at -90°C for directional freezing; then placing the frozen sample into a freeze dryer and drying it at -90°C for 72 hours to finally obtain MXene@CoNi composite aerogel.

2. The method for preparing an MXene@CoNi composite aerogel according to claim 1, characterized in that, In step (1.1), the concentration of hydrochloric acid is 10-15 mol / L, and the stirring time in step (1.1) is 1-10 minutes. In step (1.4), during ultrasound, the reaction temperature is 0~4℃ and the ultrasound time is 1h; In step (1.5), the temperature is room temperature, the speed is 3500 rpm / min, and the centrifugation time is 1 h.

3. The method for preparing an MXene@CoNi composite aerogel according to claim 1, characterized in that, The method for preparing one-dimensional magnetic CoNi chains in step (2) specifically includes the following steps: (2.1) Add nickel chloride hexahydrate, cobalt chloride hexahydrate and hexamethylenetetramine in a molar ratio of 1:1:3 to 1,2-propanediol, stir and sonicate to dissolve and mix them thoroughly to obtain solution A; (2.2) Add NaOH particles to solution A at 120℃, wherein the molar ratio of NaOH particles to nickel chloride hexahydrate is 1:2; stir thoroughly to mix thoroughly until it turns dark blue, thus obtaining solution B; (2.3) The magnetic field heat treatment induction process involves placing solution B in a hydrothermal reactor and then placing the hydrothermal reactor into the magnetic field heat treatment furnace chamber for reaction; (2.4) The final product obtained from the reaction was collected by centrifugation, washed with deionized water and anhydrous ethanol respectively, and dried to obtain a one-dimensional magnetic CoNi chain.

4. The method for preparing an MXene@CoNi composite aerogel according to claim 1, characterized in that, In step (3), the gelatin solution is prepared according to the ratio of 1g gelatin particles dispersed in 50ml of deionized water, and the gelatin solution is an approximately transparent solution obtained after heating.

5. MXene@CoNi composite aerogel prepared by any one of the preparation methods described in claims 1-4.

6. The application of the MXene@CoNi composite aerogel prepared by the preparation method according to any one of claims 1-4, characterized in that, Used for electromagnetic wave absorption.

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