Preparation and application of MXene / CMC / PVA / CNTs composite elastic aerogel material

Abstract

The application provides preparation and application of MXene / CMC / PVA / CNTs composite elastic aerogel material and relates to the technical field of composite materials.The MXene / CMC / PVA / CNTs composite elastic aerogel material is prepared by the following steps: solution blending of MXene nanosheets, carbon nanotubes, sodium carboxymethyl cellulose and polyvinyl alcohol according to a mass ratio of 40-75:1-1.25:16-24:45-55, directional freezing and vacuum freeze drying to construct a three-dimensional porous network structure, and introduction of hydrophobic groups through surface silanization modification. The electromagnetic shielding performance and mechanical performance of the composite elastic aerogel material are improved through regulation and control of the addition amount of MXene and silanization modification, based on the synergistic effect of the layered porous structure, the conductive network and the interface polarization.

Description

Technical Field

[0001] This invention relates to the field of composite materials technology, specifically to the preparation and application of MXene / CMC / PVA / CNTs composite elastic aerogel materials. Background Technology

[0002] Transition metal carbonitrides (MXenes) are novel two-dimensional conductive materials with synergistic properties such as extremely high conductivity, large aspect ratio, interlayer-derived spacing control, and doping-induced band modulation, making them widely applicable in electromagnetic shielding. However, MXene-based aerogels rely on intermolecular interactions such as hydrogen bonds and van der Waals forces, resulting in generally poor mechanical properties. Furthermore, the oxygen-containing functional groups of MXene are easily oxidized under humid conditions, leading to a significant decrease in their electromagnetic shielding efficiency. Therefore, it is necessary to develop an MXene-based composite aerogel with better mechanical properties and stable electromagnetic shielding performance. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a method for preparing and applying an MXene / CMC / PVA / CNTs composite elastic aerogel material. This invention improves the electromagnetic shielding and mechanical properties of the composite elastic aerogel material by controlling the amount of MXene added and silanization modification, based on the synergistic effect of the layered porous structure, conductive network, and interfacial polarization.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing an MXene / CMC / PVA / CNTs composite elastic aerogel material, comprising the following steps: MXene nanosheets, carbon nanotubes, sodium carboxymethyl cellulose, and polyvinyl alcohol were solution blended to obtain a composite dispersion. The composite dispersion was subjected to directional freezing and vacuum freeze-drying in sequence to obtain MXene / CMC / PVA / CNTs composite aerogel; The MXene / CMC / PVA / CNTs composite aerogel was surface-silanized to obtain the MXene / CMC / PVA / CNTs composite elastic aerogel material. The mass ratio of MXene nanosheets, carbon nanotubes, sodium carboxymethyl cellulose, and polyvinyl alcohol is 40~75:1~1.25:16~24:45~55.

[0005] Preferably, the surface silanization modification reagent includes silane reagents, such as methyltrichlorosilane, 3-aminopropyltrimethoxysilane, or N-(2-aminoethyl)-3-aminopropyltriethoxysilane, and the mass ratio of the silane reagent to the MXene / CMC / PVA / CNTs composite aerogel is 0.8~1.2:0.1~0.25.

[0006] Preferably, the solution blending includes: mixing and sonicating an aqueous solution of sodium carboxymethyl cellulose, an aqueous solution of polyvinyl alcohol, an aqueous dispersion of carbon nanotubes, and an aqueous solution of MXene nanosheets.

[0007] Preferably, the concentration of the aqueous solution of sodium carboxymethyl cellulose is 4~6 mg / mL.

[0008] Preferably, the concentration of the aqueous solution of polyvinyl alcohol is 45-55 mg / mL, and the concentration of the aqueous dispersion of carbon nanotubes is 4-5 mg / mL.

[0009] Preferably, the directional freezing is unidirectional freezing, and the unidirectional freezing time is 8~12 minutes.

[0010] Preferably, the cold trap temperature for the vacuum freeze-drying is below -53°C, the vacuum degree is ≤10Pa, and the time is 24~72h.

[0011] Preferably, the carbon nanotubes include one or more of multi-walled carbon nanotubes, single-walled carbon nanotubes, and hydroxylated single-walled carbon nanotubes.

[0012] The present invention provides an MXene / CMC / PVA / CNTs composite elastic aerogel material prepared by the preparation method described above, wherein the MXene / CMC / PVA / CNTs composite elastic aerogel material has a three-dimensional porous network structure.

[0013] This invention provides the application of the MXene / CMC / PVA / CNTs composite elastic aerogel material described in the above technical solution in the field of electromagnetic shielding.

[0014] This invention provides a method for preparing an MXene / CMC / PVA / CNTs composite elastic aerogel material, comprising the following steps: MXene nanosheets, carbon nanotubes, sodium carboxymethyl cellulose, and polyvinyl alcohol were solution blended to obtain a composite dispersion. The composite dispersion was subjected to directional freezing and vacuum freeze-drying in sequence to obtain MXene / CMC / PVA / CNTs composite aerogel; The MXene / CMC / PVA / CNTs composite aerogel was surface-silanized to obtain the MXene / CMC / PVA / CNTs composite elastic aerogel material. The mass ratio of MXene nanosheets, carbon nanotubes, sodium carboxymethyl cellulose, and polyvinyl alcohol is 40~75:1~1.25:16~24:45~55.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention improves electromagnetic shielding performance and mechanical properties by controlling the amount of MXene added and silanization modification, based on the synergistic effect of layered porous structure, conductive network and interface polarization. The resulting composite elastic aerogel material has excellent mechanical and electromagnetic shielding properties. In this invention, sodium carboxymethyl cellulose and polyvinyl alcohol are cross-linked through multiple hydrogen bonds. The hydroxyl and carboxyl groups on their molecular chains form a large number of hydrogen bonds with the oxygen-containing functional groups on the MXene surface, constructing a dense cross-linked network. Carbon nanotubes, as one-dimensional nanofibers, are interspersed between the MXene sheets, playing a reinforcing role similar to "steel bars," effectively transferring stress and preventing crack propagation, significantly improving the toughness and compression resilience of the aerogel. In addition, surface silanization modification further stabilizes the three-dimensional network structure by covalently modifying the skeleton surface, improving the material's resistance to deformation. The MXene nanosheets and carbon nanotubes overlap to form a three-dimensional interconnected conductive pathway, providing a basis for the reflection and absorption of electromagnetic waves and ensuring initial shielding effectiveness. At the same time, the numerous pores inside the aerogel cause the incident electromagnetic waves to undergo multiple reflections, scattering, and polarization losses, converting electromagnetic energy into heat energy dissipation, significantly improving shielding efficiency.

[0016] Furthermore, the surface silanization modification in this invention introduces hydrophobic methyl groups (-CH3) on the aerogel surface, which effectively prevents moisture and oxygen from contacting the oxygen-containing functional groups of MXene, thus avoiding their oxidation and maintaining the long-term stability of the material's conductivity and electromagnetic shielding performance.

[0017] This invention also provides an MXene / CMC / PVA / CNTs composite elastic aerogel material prepared by the preparation method described above. Data from the examples show that the density of the MXene / CMC / PVA / CNTs composite elastic aerogel material prepared by the method of this invention is 8 mg / cm³. 3 The EMI SE is up to 60.88dB. After 100 compression cycles at 60% strain, the EMI SE still retains 98.06% of its initial value, with an attenuation of only 1.15dB, demonstrating excellent mechanical and electromagnetic shielding performance. Attached Figure Description

[0018] Figure 1The X-ray diffraction patterns of the sample from Example 1 and MAX and MXene are shown. Figure 2 The infrared spectra of MXene for samples from Example 1 and Comparative Example 1 are shown below. Figure 3 Raman spectra of MXene for samples from Example 1 and Comparative Example 1; Figure 4 XPS broad spectrum of MXene for samples of Example 1 and Comparative Example 1; Figure 5 (a) shows the water contact angle change of the sample of Comparative Example 1 at 1s, (b) shows the water contact angle change of the sample of Comparative Example 1 at 2s, (c) shows the water contact angle change of the sample of Comparative Example 1 at 3s, (d) shows the water contact angle change of the sample of Example 1 at 1s, (e) shows the water contact angle change of the sample of Example 1 at 60s, and (f) shows the water contact angle change of the sample of Example 1 at 120s. Figure 6 In the image, (a) is a scanning electron microscope (SEM) image of the sample of Comparative Example 2, (b) is a scanning electron microscope (SEM) image of the sample of Comparative Example 3, (c) is a scanning electron microscope (SEM) image of the sample of Example 1, and (d) is a scanning electron microscope (SEM) image of the sample of Comparative Example 4. Figure 7 (a) shows the stress performance of the sample of Comparative Example 2 under 10%~60% strain, (b) shows the stress performance of the sample of Comparative Example 3 under 10%~60% strain, (c) shows the stress performance of the sample of Example 1 under 10%~60% strain, and (d) shows the stress performance of the sample of Comparative Example 4 under 10%~60% strain. Figure 8 The stress-strain diagram of the sample of Example 1 after undergoing 20 to 100 cycles of compression at 60% strain; Figure 9 EMI SE images of the samples from Example 1 and Comparative Examples 2-4 in the X-band; Figure 10 (a) shows the EMI SE diagram in the X-band before and after 100 compression cycles of the sample in Example 1; (b) shows the average SEA, SER, and SET of the sample in Example 1 before and after 100 compression cycles; and (c) shows the electromagnetic interference shielding retention rate of the sample in Example 1 after compression / release cycles before and after 100 compression cycles. Figure 11 This is a flowchart of the sample preparation process for Example 1. Detailed Implementation

[0019] This invention provides a method for preparing an MXene / CMC / PVA / CNTs composite elastic aerogel material, comprising the following steps: MXene nanosheets, carbon nanotubes, sodium carboxymethyl cellulose, and polyvinyl alcohol were solution blended to obtain a composite dispersion. The composite dispersion was subjected to directional freezing and vacuum freeze-drying in sequence to obtain MXene / CMC / PVA / CNTs composite aerogel; The MXene / CMC / PVA / CNTs composite aerogel was surface-silanized to obtain the MXene / CMC / PVA / CNTs composite elastic aerogel material. The mass ratio of MXene nanosheets, carbon nanotubes, sodium carboxymethyl cellulose, and polyvinyl alcohol is 40~75:1~1.25:16~24:45~55.

[0020] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0021] This invention involves solution blending of MXene nanosheets, carbon nanotubes, sodium carboxymethyl cellulose, and polyvinyl alcohol to obtain a composite dispersion.

[0022] In this invention, the MXene nanosheets are preferably used in the form of an aqueous solution of MXene nanosheets. This invention does not impose special requirements on the source of MXene nanosheets, which can be prepared using methods well known in the art.

[0023] In this invention, the aqueous solution of the MXene nanosheets is obtained by selectively etching and stripping the MAX material sequentially. The MAX material preferably includes Ti3AlC2, and the selective etching is preferably performed by mixing LiF and hydrochloric acid to generate HF in situ.

[0024] In this invention, the LiF and hydrochloric acid are mixed and placed in a polytetrafluoroethylene reactor, and Ti3AlC2 is added for selective etching. The preferred ratio of LiF, hydrochloric acid and Ti3AlC2 is 2.5~3.5g:35~45mL:1.7~2.1g, specifically 3g:40mL:2g. The preferred concentration of hydrochloric acid is 8~10mol / L. The selective etching is preferably carried out under oil bath stirring conditions, the preferred temperature is 37~42℃, and the preferred time is 22~26h.

[0025] After the selective etching is completed, excess acid is preferably removed by centrifugal washing. The centrifugal washing speed is preferably 3300~5000 r / min, specifically 3500, 4000, or 4500 r / min, and the single centrifugation time is preferably 5~10 min, specifically 6, 8, or 9 min. The total centrifugal washing time is preferably 1.5 h~2.5 h. After washing until the pH value of the supernatant is close to 6, ultrasonic peeling is then performed. The ultrasonic peeling is preferably performed in an ice bath for 1 h. After the ultrasonic peeling is completed, centrifugation is preferably performed again at a speed of 3500 r / min for 30 min. The supernatant is collected, which is the aqueous solution of the MXene nanosheets.

[0026] In this invention, the concentration of the aqueous solution of the MXene nanosheets is preferably 8-15 mg / mL, specifically 10, 12 or 14 mg / mL.

[0027] In this invention, the carbon nanotubes (CNTs) are preferably used in the form of an aqueous dispersion of carbon nanotubes. The carbon nanotubes preferably include one or more of multi-walled carbon nanotubes, single-walled carbon nanotubes, and hydroxylated single-walled carbon nanotubes. The concentration of the aqueous dispersion of carbon nanotubes is preferably 4-5 mg / mL.

[0028] In this invention, the carbon nanotubes, as functional fillers, are uniformly distributed within the composite system. On one hand, their high aspect ratio structure physically blocks the MXene sheets, preventing their dense packing and preserving the material's high specific surface area. On the other hand, they form conductive bridges within the matrix, reducing interfacial contact resistance and optimizing overall conductivity. Furthermore, the carbon nanotubes, together with sodium carboxymethyl cellulose and polyvinyl alcohol, form a three-dimensional network framework that significantly enhances the aerogel's mechanical toughness and compressive strength.

[0029] In this invention, sodium carboxymethyl cellulose (CMC) is preferably used in the form of an aqueous solution of sodium carboxymethyl cellulose, and the concentration of the aqueous solution of sodium carboxymethyl cellulose is preferably 4~6 mg / mL.

[0030] The sodium carboxymethyl cellulose described in this invention serves to provide a three-dimensional framework structure and molding substrate for aerogels; inhibit MXene sheet aggregation, improve the compressive strength, toughness, and cyclic resilience of aerogels; and form numerous interconnected pores through fiber interweaving, increasing the specific surface area and facilitating the transport of ions and gases, thus adapting to applications such as electromagnetic shielding. Simultaneously, its surface is rich in hydroxyl groups, which can form hydrogen bonds with MXene and carbon nanotubes, strengthening interfacial bonding and enhancing the structural stability of the composite system.

[0031] In this invention, the polyvinyl alcohol (PVA) is preferably used in the form of an aqueous solution of polyvinyl alcohol, the concentration of the aqueous solution of polyvinyl alcohol is preferably 45~55 mg / mL, and the average molecular weight of the polyvinyl alcohol is preferably 7.5 × 10⁻⁶.4 ~8.0×10 4 .

[0032] In this invention, the solution blending preferably includes: mixing an aqueous solution of sodium carboxymethyl cellulose with an aqueous solution of polyvinyl alcohol and then ultrasonically dispersing the mixture to obtain a composite matrix solution; adding an aqueous dispersion of carbon nanotubes to the composite matrix solution and stirring until homogeneous to obtain a carbon nanotube-composite matrix solution; and finally mixing the solution with an aqueous solution of MXene nanosheets and ultrasonically dispersing the solution in an ice bath to obtain the MXene / CMC / PVA / CNTs composite dispersion.

[0033] In this invention, the preferred mass ratio of the sodium carboxymethyl cellulose aqueous solution to the polyvinyl alcohol aqueous solution is 4:1, the preferred ultrasonic dispersion time is 1~1.5h, the preferred frequency is 40~50kHz, and the preferred temperature is 23~26℃.

[0034] In this invention, the mass of the aqueous dispersion of carbon nanotubes is preferably 4-6% of the total mass of the composite matrix solution, the stirring is preferably carried out on a magnetic stirring table, the stirring time is preferably 30-40 min, and the temperature is preferably room temperature (23-26℃).

[0035] In this invention, the volume ratio of the aqueous solution of MXene nanosheets to the carbon nanotube-composite matrix solution is preferably 1~7:3~9, and the ice bath ultrasonication time is preferably 25~40 min.

[0036] After obtaining the composite dispersion, the present invention sequentially subjected the composite dispersion to directional freezing and vacuum freeze-drying to obtain the MXene / CMC / PVA / CNTs composite aerogel.

[0037] In this invention, the directional freezing is preferably unidirectional freezing, the unidirectional freezing time is preferably 8~12 min, and the temperature is preferably -196℃~-185℃. The unidirectional freezing preferably includes: pouring the composite dispersion into a mold, and then placing the mold on the surface of a copper block pre-cooled by liquid nitrogen for unidirectional freezing. The mold preferably includes a copper-based polytetrafluoroethylene mold.

[0038] In this invention, during the unidirectional freezing process, ice crystals grow directionally along the temperature gradient, causing MXene, CMC, and PVA to align in an directional manner. On the one hand, this constructs an anisotropic three-dimensional network, significantly enhancing the material's mechanical strength and resilience. On the other hand, the ice crystal separation effectively alleviates the aggregation and stacking of MXene sheets, and the directionally overlapping point network further optimizes the system's conductivity.

[0039] In this invention, it is preferable to transfer the directionally frozen composite dispersion to a vacuum freeze dryer for vacuum freeze drying. The cold trap temperature of the vacuum freeze dryer is preferably below -53°C, the vacuum degree is preferably ≤10Pa, and the time is preferably 24~72h.

[0040] After obtaining the MXene / CMC / PVA / CNTs composite aerogel, the present invention performs surface silanization modification on the MXene / CMC / PVA / CNTs composite aerogel to obtain the MXene / CMC / PVA / CNTs composite elastic aerogel material.

[0041] In this invention, the surface silanization modification reagent preferably includes a silane reagent, which preferably includes methyltrichlorosilane, 3-aminopropyltrimethoxysilane, or N-(2-aminoethyl)-3-aminopropyltriethoxysilane. The mass ratio of the silane reagent to the MXene / CMC / PVA / CNTs composite aerogel is preferably 0.8~1.2:0.1~0.25. The surface silanization modification temperature is preferably 52~60℃, specifically 54, 56, or 58℃, and the time is preferably 8~12h, specifically 9, 10, or 11h.

[0042] In this invention, the surface silanization modification is preferably a vapor deposition modification, which is preferably carried out in a vacuum drying oven. The silane reagent is placed in a sample vial and placed together with the MXene / CMC / PVA / CNTs composite aerogel (MCPC composite aerogel) in the vacuum drying oven to ensure that the MCPC composite aerogel does not come into direct contact with methyltrichlorosilane.

[0043] The MXene / CMC / PVA composite aerogel described in this invention is rich in hydroxyl groups on its surface, making it extremely hydrophilic. In humid or aquatic environments, it easily absorbs water and swells, severely reducing structural stability and durability. This invention employs a silane-based vapor deposition method to hydrophobically modify the aerogel. The silane reagent vapor hydrolyzes under trace amounts of water vapor to generate highly active silanol groups, which then undergo dehydration condensation with the abundant hydroxyl groups on the aerogel surface, forming stable Si-O-Si covalent bonds. This successfully grafts low-surface-energy methyl groups onto the material surface. The silanization modification only regulates the chemical state of the material surface. After modification, a large number of polar hydroxyl groups are replaced by non-polar methyl groups, significantly reducing the surface energy and transforming the aerogel from superhydrophilic to hydrophobic. This effectively inhibits water vapor penetration and structural collapse due to moisture absorption. Simultaneously, the dense silane-modified layer isolates air and moisture, slowing down the oxidative degradation of MXene and significantly improving the environmental stability of the composite aerogel. This allows it to maintain excellent mechanical resilience and electromagnetic shielding performance in high-humidity and complex environments.

[0044] In this invention, after the surface silanization modification is completed, the obtained modified MXene / CMC / PVA / CNTs composite aerogel is preferably vacuum dried to obtain the MXene / CMC / PVA / CNTs composite elastic aerogel material.

[0045] In this invention, the vacuum drying is preferably carried out in a vacuum drying oven, the vacuum drying time is preferably 1.5 to 3 hours, and the vacuum degree is preferably -25 to -20 kPa. The purpose of the vacuum drying is to remove residual methyltrichlorosilane on the surface.

[0046] The present invention also provides an MXene / CMC / PVA / CNTs composite elastic aerogel material prepared by the preparation method described above, wherein the MXene / CMC / PVA / CNTs composite elastic aerogel material has a three-dimensional porous network structure.

[0047] This invention also provides the application of the MXene / CMC / PVA / CNTs composite elastic aerogel material described above in the field of electromagnetic shielding.

[0048] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0049] Example 1 Figure 11 The sample preparation flowchart for Example 1 is shown below; the preparation steps are as follows: (1) In an oil bath at 40°C, 3g of LiF and 40mL of 9M hydrochloric acid solution were added to a polytetrafluoroethylene reaction vessel and magnetically stirred for 15min. 2g of Ti3AlC2 powder (MAX) was added to the reaction vessel and stirred continuously for 48h. After etching, the product was transferred to a centrifuge tube and centrifuged at 3500r / min for 5min to remove the upper acid layer. Deionized water was then added, and the mixture was shaken manually and centrifuged again. When the pH of the supernatant was close to 6 and the supernatant turned dark green after dilution, it indicated that the washing and centrifugation were completed and a multilayer MXene aqueous solution was obtained. The multilayer MXene aqueous solution was subjected to ice bath sonication and ultrasonic peeling for 1h. Then it was centrifuged at 3500r / min for 30min and the supernatant was collected, which is the MXene aqueous solution. (2) Sodium carboxymethyl cellulose aqueous solution (5 mg / mL) and polyvinyl alcohol aqueous solution (50 mg / mL) were mixed at a mass ratio of 4:1 and ultrasonically dispersed to obtain a composite matrix solution. The ultrasonic time was 1 h. Aqueous dispersion of multi-walled carbon nanotubes (5 mg / mL) was added to the composite matrix solution. The aqueous dispersion of multi-walled carbon nanotubes accounted for 5% of the total mass of the carboxymethyl cellulose composite matrix solution. The solution was placed on a magnetic stirring table and stirred at room temperature for 30 min to obtain a mixed solution. (3) Mix the mixed solution from step (2) and the aqueous solution of 10 mg / mL MXene at a volume ratio of 1:1, and sonicate in an ice bath for 30 min to obtain a composite dispersion (multi-component mixed solution). (4) Pour the composite dispersion from step (3) into a copper-based polytetrafluoroethylene mold, then place the mold on the surface of a copper block pre-cooled by liquid nitrogen. After the solution in the mold is completely frozen, transfer it to a freeze dryer and set the freeze drying parameters as follows: cold trap temperature -55℃, vacuum degree 10Pa, and continue drying for 24h to obtain MXene / CMC / PVA / CNT composite aerogel, denoted as MCPC aerogel. (5) Place 0.2 mL of methyltrichlorosilane in a sample bottle, and put 29.7 mg of MXene / CMC / PVA / CNT composite aerogel and the sample bottle into a vacuum drying oven at 60 °C for 10 h. After the reaction is complete, place the MXene / CMC / PVA / CNT composite aerogel separately in a vacuum drying oven for 2 h to remove residual methyltrichlorosilane on the surface, and obtain the MXene / CMC / PVA / CNT composite elastic aerogel material, denoted as S-MCPC aerogel, with a density of 8 mg / cm³. 3 The mass ratio of MXene nanosheets, carbon nanotubes, sodium carboxymethyl cellulose and polyvinyl alcohol is 50:1.25:20:50.

[0050] Example 2 Similar to Example 1, the only difference is that in step (3), the mixed solution from step (2) and the 15 mg / mL MXene aqueous solution are mixed in a 1:1 volume ratio, and the mass ratio of MXene nanosheets, carbon nanotubes, sodium carboxymethyl cellulose and polyvinyl alcohol is 75:1.25:20:50.

[0051] Example 3 Similar to Example 1, the only difference is that in step (3), the mixed solution from step (2) and the 8 mg / mL MXene aqueous solution are mixed in a 1:1 volume ratio, and the mass ratio of MXene nanosheets, carbon nanotubes, sodium carboxymethyl cellulose and polyvinyl alcohol is 40:1.25:20:50.

[0052] Comparative Example 1 Same as in Example 1, except that step (5) is omitted.

[0053] Comparative Example 2 Similar to Example 1, the only difference is that in step (3), the mixed solution from step (2) and the 10 mg / mL MXene aqueous solution are mixed at a volume ratio of 9:1, and the mass ratio of MXene nanosheets, carbon nanotubes, sodium carboxymethyl cellulose and polyvinyl alcohol is 10:2.25:36:90.

[0054] Comparative Example 3 Similar to Example 1, the only difference is that in step (3), the mixed solution from step (2) and the 10 mg / mL MXene aqueous solution are mixed at a volume ratio of 7:3, and the mass ratio of MXene nanosheets, carbon nanotubes, sodium carboxymethyl cellulose and polyvinyl alcohol is 30:1.75:28:70.

[0055] Comparative Example 4 Similar to Example 1, the only difference is that in step (3), the mixed solution from step (2) and the 10 mg / mL MXene aqueous solution are mixed at a volume ratio of 3:7, and the mass ratio of MXene nanosheets, carbon nanotubes, sodium carboxymethyl cellulose and polyvinyl alcohol is 70:0.75:12:30.

[0056] Test Example 1 The microstructure and related properties of the products obtained in Example 1 and Comparative Examples 1-4 were characterized. Diffraction signals were acquired using a Bruker D8 Advance X-ray diffractometer (Germany); functional group structures were characterized using a Nicolet iS50 Fourier transform infrared spectrometer (Thermo Fisher Scientific); sample structures were characterized using an Alpha 300R Raman spectrometer (WITec, Germany); elemental composition and functional groups were characterized using a Kratos AXIS Ultra DLD X-ray photoelectron spectroscopy (KRATOS ANALYTICAL, UK); water contact angles were measured using an SDC-100 contact angle meter (Shanghai SDC Precision Instruments Co., Ltd.); and microstructures were determined using a Verios (FEI, USA). Characterized using a G4 ultra-high resolution field emission scanning electron microscope; compression or cyclic compression performance was measured using a CMT8505 universal testing machine from Shenzhen Xin Sansi Measurement Technology Co., Ltd.; shielding performance was tested using a 3672 vector network analyzer from China Electronics Technology Group Corporation to measure the scattering parameters (S-parameters) of electromagnetic waves within the waveguide.

[0057] Figure 1The X-ray diffraction patterns of the sample, MAX, and MXene in Example 1 are shown. It can be seen that MXene was prepared by etching away the (104) peak of MAX. The (002) peak of MXene changed from 8.57° to 5.33° in Example 1, which indicates that the spacing between MXene nanosheets increased, which was caused by the intercalation of CMC and PVA.

[0058] Figure 2 The infrared spectra of MXene for samples from Example 1 and Comparative Example 1 are shown; it can be seen that at 3500 cm⁻¹... -1 The strong absorption peak of MXene in this region corresponds to its surface -OH functional groups; the absorption peak of Comparative Example 1 originates from the hydrogen bonding between the organic component (CMC / PVA) and the -OH groups on the MXene surface; the peak of Example 1 is further weakened, indicating that methyltrichlorosilane underwent a dehydration condensation reaction with the -OH groups on the MXene surface, consuming some of the -OH groups; the absorption peak of Comparative Example 1 is in the range of 2800~3000 cm⁻¹. -1 A new absorption peak appeared in the region, corresponding to the methylene vibration (-CH2-) in CMC / PVA, proving the successful composite of the organic polymers; this peak was retained in Example 1, indicating that the silane modification did not destroy the internal organic component structure of Comparative Example 1. Example 1 showed a peak at 1100 cm⁻¹. -1 The presence of a characteristic absorption peak of Si-O in the region, while MXene and Comparative Example 1 did not exhibit this peak, demonstrating that the silane reagent was successfully deposited on the surface of the example and formed a siloxane coating; at the same time, the shift of the Ti-O peak reflects the chemical bonding between silane and the MXene surface.

[0059] Figure 3 The images show the Raman spectra of MXene from samples of Example 1 and Comparative Example 1; it can be seen that MXene has a Raman spectrum in the range of 150~600 cm⁻¹. -1 The characteristic peaks in the region correspond to the vibrations of Ti-C bonds and surface Ti-O bonds; the enhanced peak intensity in Comparative Example 1 is due to the interfacial interaction between CMC and MXene; the increased peak intensity in Example 1 indicates that the silane coating introduces interfacial stress, altering the local bonding environment of MXene; comparison shows that the MXene structure persists throughout the aerogel preparation process, resulting in successful composite aerogel preparation with a peak intensity of 500-600 cm⁻¹. -1 The peak appearing at the point is due to the bending vibration of the COC chemical bond, which is caused by CMC. The appearance of this peak in the aerogel of Comparative Example 1 directly proves that CMC has been successfully combined with MXene and multi-walled carbon nanotubes. The retention of this peak in the aerogel of Example 1 indicates that the silane modification only acts on the surface groups of Comparative Example 1, while the bulk structure of CMC is not destroyed.

[0060] Figure 4The XPS broad spectrum of the samples of Example 1 and Comparative Example 1 and MXene shows that MXene and Comparative Example 1 mainly contain four elements: C, O, F and Ti. This proves the successful etching of MXene and the successful preparation of Comparative Example 1. Example 1 introduces the element Si, which is the Si group introduced by hydrolysis after methyltrichlorosilane vapor deposition.

[0061] Figure 5 (a) shows the water contact angle change of the sample in Comparative Example 1 at 1 s; (b) shows the water contact angle change of the sample in Comparative Example 1 at 2 s; (c) shows the water contact angle change of the sample in Comparative Example 1 at 3 s; (d) shows the water contact angle change of the sample in Example 1 at 1 s; (e) shows the water contact angle change of the sample in Example 1 at 60 s; and (f) shows the water contact angle change of the sample in Example 1 at 120 s. It can be seen that the water contact angles of the two surfaces in Comparative Example 1 and Example 1 show significant differences over time. The contact angle of the surface in Comparative Example 1 is 25.113° at 1 s, decreases to 14.580° at 2 s, and further decreases to 9.465° at 3 s. This indicates that the contact angle of the surface in Comparative Example 1 decreases rapidly over time, and the initial contact angle is relatively small (far less than 90°). This is because the surface of Comparative Example 1 is a hydrophilic surface (contact angle <90°), and droplets will gradually spread on the surface. The contact angle of the composite aerogel surface of Example 1 changes as follows: the contact angle is 88.176° at 1s, only slightly decreases to 88.013° at 60s, and remains basically unchanged at 88.013° at 120s. It can be seen that the contact angle of the surface of Example 1 is almost stable over time and has anti-wetting ability. This is because the surface of Example 1 is modified with methyltrichlorosilane, which introduces Si-O bonds and methyl groups to inhibit the further spread of droplets, so that the interaction between droplets and the surface reaches equilibrium. Therefore, the contact angle remains stable for a long time. This difference shows that the surface modification of Example 1 effectively improves the hydrophobicity of the aerogel, which is suitable for scenarios that require long-term surface wettability and provides the possibility for multi-scenario use of aerogel.

[0062] Figure 6(a) is a scanning electron microscope (SEM) image of the sample in Comparative Example 2, (b) is a scanning electron microscope (SEM) image of the sample in Comparative Example 3, (c) is a scanning electron microscope (SEM) image of the sample in Example 1, and (d) is a scanning electron microscope (SEM) image of the sample in Comparative Example 4. The microstructures of S-MCPC aerogels with different contents of MXene are shown. Comparative Example 2 exhibits a regular layered pore structure along the growth direction of ice crystals. This is due to the pore structure left after the ice crystals are removed by freeze-drying after orderly growth from bottom to top. As the content of MXene increases, the polymer content decreases. From Comparative Example 3 to Example 1, it can be seen that the layered order of the pores gradually decreases, and the pore structure and size distribution tend to be uneven. However, when the MXene content reaches 70 wt%, the pore structure of Comparative Example 4 tends to be more disordered, transforming into an irregular porous morphology.

[0063] Figure 7 (a) shows the stress performance of the sample in Comparative Example 2 under strain ranging from 10% to 60%; (b) shows the stress performance of the sample in Comparative Example 3 under strain ranging from 10% to 60%; (c) shows the stress performance of the sample in Example 1 under strain ranging from 10% to 60%; and (d) shows the stress performance of the sample in Comparative Example 4 under strain ranging from 10% to 60%. All S-MCPC aerogels exhibit hyperelastic mechanical response characteristics, with stress increasing nonlinearly with increasing strain, reaching a maximum of 60%. At a strain of 20%, the aerogels are all in the linear elastic region, where the aerogel skeleton undergoes elastic deformation, and the stress increases linearly with strain, within the strain range of 20%. At approximately 50% strain, the slope of the curve decreases with increasing strain, entering a relatively flat region. This reflects the yielding of the pore walls of the microporous structure inside the aerogel. When the strain reaches 60%, the pores are significantly compressed, and the skeleton material begins to directly contact, resulting in a sharp increase in stress. Stress unloading is performed within a stress range of 20% to 60%, and the curve can return to the origin relatively well. Furthermore, the hysteresis loop area increases significantly with increasing maximum strain, indicating that the aerogel has good shape recovery ability and flexibility. At 60% strain, the strain loss of Example 1 is minimal, almost returning to the origin, indicating that the composite aerogel of Example 1 has the best elasticity and recovery performance.

[0064] Figure 8 The stress-strain diagrams of the sample of Example 1 after 20 to 100 cycles of compression at 60% strain are shown. The results show that the curve trajectories of each cycle have a very high degree of overlap. In particular, the morphology of the loading and unloading segments remains highly consistent. This indicates that after experiencing multiple large strain cyclic loading, the internal skeleton of Example 1 did not experience significant structural collapse or irreversible mechanical damage, demonstrating excellent cyclic stability.

[0065] Figure 9The EMI SE (Electromagnetic Shielding Sequence) images of the samples from Examples 1 and Comparative Examples 2-4 in the X-band are shown. The electromagnetic shielding effect in the X-band is displayed when the S-MCPC aerogel thickness is 4.5 mm. It can be seen that the electromagnetic shielding effect of Comparative Example 2 is poor, with a maximum EMI SE of only 5.63 dB. The electromagnetic shielding effect improves with increasing MXene content, and the maximum EMI SE of Comparative Example 3 in the X-band is 31.67 dB. The EMI SE of Examples 1 and Comparative Example 4 are relatively close, and the maximum EMI SE of Example 1 is 60.88 dB, which is greater than that of Comparative Example 4 (55.65 dB).

[0066] Figure 10 (a) shows the EMI SE in the X-band before and after 100 compression cycles of the sample in Example 1; (b) shows the average SEA, SER, and SET of the sample in Example 1 before and after 100 compression cycles; (c) shows the electromagnetic interference shielding retention rate of the sample in Example 1 after compression / release cycles before and after 100 compression cycles. In Example 1, the EMI SE changes little before and after 100 cycles, and SEA is dominant, indicating that it is still an absorption-based electromagnetic shielding mechanism. The average EMI SE of Example 1 remains relatively stable after 100 compression-release cycles. Example 1 retains 98.06% of the initial EMI SE, and the attenuation value is only 1.15dB. This demonstrates its hyperelastic shielding performance. During the cycling process, the absorption efficiency of the material is almost completely maintained, and the overall EMI SE retention rate is high, verifying its electromagnetic shielding stability under cyclic conditions.

[0067] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an MXene / CMC / PVA / CNTs composite elastic aerogel material, characterized in that, Includes the following steps: MXene nanosheets, carbon nanotubes, sodium carboxymethyl cellulose, and polyvinyl alcohol were solution-blended to obtain a composite dispersion. The composite dispersion was subjected to directional freezing and vacuum freeze-drying in sequence to obtain MXene / CMC / PVA / CNTs composite aerogel; The MXene / CMC / PVA / CNTs composite aerogel was surface-silanized to obtain the MXene / CMC / PVA / CNTs composite elastic aerogel material. The mass ratio of MXene nanosheets, carbon nanotubes, sodium carboxymethyl cellulose and polyvinyl alcohol is 40~75:1~1.25:16~24:45~55.

2. The preparation method according to claim 1, characterized in that, The surface silanization modification reagent includes silane reagents, including methyltrichlorosilane, 3-aminopropyltrimethoxysilane or N-(2-aminoethyl)-3-aminopropyltriethoxysilane, and the mass ratio of the silane reagent to the MXene / CMC / PVA / CNTs composite aerogel is 0.8~1.2:0.1~0.

25.

3. The preparation method according to claim 1, characterized in that, The solution blending includes: mixing and sonicating an aqueous solution of sodium carboxymethyl cellulose, an aqueous solution of polyvinyl alcohol, an aqueous dispersion of carbon nanotubes, and an aqueous solution of MXene nanosheets.

4. The preparation method according to claim 3, characterized in that, The concentration of the aqueous solution of sodium carboxymethyl cellulose is 4~6 mg / mL.

5. The preparation method according to claim 3, characterized in that, The concentration of the aqueous solution of polyvinyl alcohol is 45~55 mg / mL, and the concentration of the aqueous dispersion of carbon nanotubes is 4~5 mg / mL.

6. The preparation method according to claim 1, characterized in that, The directional freezing is unidirectional freezing, and the unidirectional freezing time is 8~12 minutes.

7. The preparation method according to claim 1, characterized in that, The cold trap temperature for the vacuum freeze-drying is below -53°C, the vacuum degree is ≤10Pa, and the time is 24~72h.

8. The preparation method according to claim 1, characterized in that, The carbon nanotubes include one or more of multi-walled carbon nanotubes, single-walled carbon nanotubes, and hydroxylated single-walled carbon nanotubes.

9. The MXene / CMC / PVA / CNTs composite elastic aerogel material prepared by the preparation method according to any one of claims 1 to 8, characterized in that, The MXene / CMC / PVA / CNTs composite elastic aerogel material has a three-dimensional porous network structure.

10. The application of the MXene / CMC / PVA / CNTs composite elastic aerogel material as described in claim 9 in the field of electromagnetic shielding.

Images