Method for preparing composite aerogel containing mxene

Abstract

The application provides a preparation method of a composite aerogel containing MXene, and comprises the following steps: obtaining a few-layer MXene suspension with different concentrations through centrifugation and concentration; performing acetal modification on polyvinyl alcohol under the protection of nitrogen to obtain modified polyvinyl alcohol with catechol groups; dissolving the modified polyvinyl alcohol in water to obtain a modified polyvinyl alcohol solution, and then adding a nanocellulose aqueous solution and a few-layer MXene dispersion liquid, and pouring the mixed liquid into a mold after uniform stirring and mixing, and then performing directional freezing through liquid nitrogen, and finally performing vacuum drying to obtain the composite aerogel containing MXene. The raw material cost is low, the preparation process is simple, and the composite aerogel containing MXene has great application prospects in the fields of electromagnetic wave absorption and sound absorption.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of application of MXene materials in aerogels, and particularly relates to a preparation method of a composite aerogel containing MXene. BACKGROUND

[0002] With the continuous development of electronic technology, human production and daily life have become more convenient. However, the resulting electromagnetic wave pollution not only affects the normal operation of electronic equipment and human health, but also threatens military security in the military field. Along with the development of industry, problems such as noise pollution also exist, and therefore, it is of great significance to develop composite materials with wave-absorbing and sound-absorbing properties. Through existing research, it is found that aerogel materials with a porous structure not only exhibit excellent wave-absorbing performance, but also have light weight and high strength mechanical properties, meeting the current development requirements of wave-absorbing materials in terms of thinness, lightness, width, and strength, and are widely used in the sound-absorbing field. However, there are few studies on composite materials that simultaneously have wave-absorbing and sound-absorbing properties, and the service life of wave-absorbing materials is also a problem in research.

[0003] As a new type of two-dimensional nanomaterial, MXene has good electrical conductivity, hydrophilicity, high specific surface area, and rich surface functional groups, and can be used as a conductive filler to be added to a composite aerogel to enhance its dielectric loss performance and achieve electromagnetic wave absorption. Existing research indicates that the use of MXene alone as a wave-absorbing material has relatively limited electromagnetic wave absorption capacity, with low absorption intensity and small effective absorption width, and therefore its wave-absorbing performance still needs to be optimized. In addition, MXene materials have poor mechanical properties and are prone to oxidation, and long-term repeated use can cause a decrease in wave-absorbing and sound-absorbing performance. The combination of MXene with other materials helps to improve its mechanical properties and wave-absorbing performance. Nano-cellulose has the advantages of green renewability, biocompatibility, and degradability, and is a star in environmentally friendly materials. Composite aerogel materials based on cellulose meet the structural requirements of wave-absorbing materials and sound-absorbing materials, and exhibit high economic and environmental value in the fields of sound absorption, wave absorption, building thermal insulation, and the like. In addition, in view of the application of composite aerogel materials in the fields of wave absorption and sound absorption in the literature, a wave-absorbing and sound-absorbing composite material is prepared from the perspective of structural design, and the wave-absorbing performance and sound-absorbing performance are synergistically optimized.

[0004] Therefore, MXene is combined with a nano-cellulose aqueous solution to prepare a composite aerogel with good wave-absorbing performance, and the sound-absorbing performance and mechanical properties are improved through structural design, and modified polyvinyl alcohol is added to improve the oxidation resistance, which is of great importance to the preparation and application of new wave-absorbing and sound-absorbing composite aerogels. SUMMARY

[0005] The present invention provides a method for preparing a compressible, antioxidant cellulose-based MXene composite aerogel that absorbs waves and sounds.

[0006] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0007] A method for preparing a composite aerogel containing MXene includes the following steps:

[0008] The few-layer MXene suspension was centrifuged and concentrated to obtain few-layer MXene dispersions of different concentrations;

[0009] 3,4-Dihydroxybenzaldehyde and p-toluenesulfonic acid monohydrate were subjected to an acetalization reaction under nitrogen protection and heating conditions to obtain a catechol-modified polyvinyl alcohol solid, which was then dissolved to obtain a catechol-modified polyvinyl alcohol solution.

[0010] After adding the cellulose-based solution to the catechol-modified polyvinyl alcohol solution and stirring until homogeneous, a few layers of MXene solution were added. The mixture was then stirred, passed through a mold, and directionally frozen with liquid nitrogen. After drying, a composite aerogel containing MXene was obtained.

[0011] Furthermore, it also includes the preparation of a few-layer MXene suspension, specifically prepared by etching a MAX phase precursor with LiF-HCl, wherein the MAX phase precursor includes Ti3C2T X Solution, Ti3N2T X Solution, Ti3CNT X Solution or Ti2CT X One or more of the substances in the solution.

[0012] Furthermore, the centrifugation speed during the concentration of the few-layer MXene suspension is 10000 rpm; the centrifugation time is 10-20 min; and the concentration of the few-layer MXene suspension obtained after centrifugation and concentration is 2-10 mg / mL.

[0013] Furthermore, the preparation of the catechol-modified polyvinyl alcohol specifically involves adding polyvinyl alcohol powder to dimethyl sulfone, continuously stirring and heating it until it is completely dissolved, cooling it to room temperature, and then adding 3,4-dihydroxybenzaldehyde and p-toluenesulfonic acid monohydrate to carry out an acetalization reaction.

[0014] Furthermore, the mass ratio of polyvinyl alcohol, 3,4-dihydroxybenzaldehyde and p-toluenesulfonic acid monohydrate is 1:(0.07-0.08):(0.2-0.3); the dissolution temperature of polyvinyl alcohol is 80°C.

[0015] Further, after the acetalization reaction, the catechol-modified polyvinyl alcohol solid is obtained by acetone precipitation and vacuum drying.

[0016] Further, the modified polyvinyl alcohol is dissolved in deionized water at 80°C to obtain the modified polyvinyl alcohol solution.

[0017] Furthermore, the cellulose-based solution has a mass fraction of 1%-2%; the freeze-drying temperature is -50 to -60°C; and the freeze-drying time is 48 to 72 hours.

[0018] Furthermore, the mass ratio of the nanocellulose, catechol-modified polyvinyl alcohol, and MXene is 1:1:2.

[0019] The present invention has the following beneficial effects:

[0020] This invention uses cellulose aerogel as a carrier to load conductive materials, which not only has the characteristics of traditional aerogel materials being lightweight, but also has the advantages of biomaterials being renewable, biodegradable, and biocompatible.

[0021] This invention uses MXene as a conductive filler and mixes it with cellulose to prepare a composite aerogel with a regular three-dimensional network structure through directional freezing, which can simultaneously absorb electromagnetic waves and sound waves.

[0022] This invention adds catechol-modified polyvinyl alcohol. The interaction between the catechol groups on the modified polyvinyl alcohol and the MXene surface inhibits the oxidation of MXene, thereby giving the material certain antioxidant properties and improving the service life of the composite aerogel.

[0023] This invention provides a compressible, antioxidant cellulose-based microwave and sound absorbing material. Using cellulose as the matrix and MXene as the conductive filler, and with the addition of catechol-modified polyvinyl alcohol, the material is prepared by directional freezing with liquid nitrogen and finally freeze-drying. This material exhibits excellent electromagnetic and acoustic wave absorption properties, while also possessing antioxidant, compressible resilience, and lightweight characteristics. The raw materials used in this invention are inexpensive, and the preparation process is simple, thus it has great application potential in the field of electromagnetic and acoustic wave absorption. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1a Photographs of the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 3;

[0026] Figure 1bThe image shows a scanning electron microscope image of the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 3 at 100 micrometers.

[0027] Figure 1c The image shows a scanning electron microscope image at 50 micrometers of the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 3.

[0028] Figure 1d The image shows a scanning electron microscope image of the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 3 at 20 micrometers.

[0029] Figure 2a This is a schematic diagram of the microwave absorption properties of the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 1;

[0030] Figure 2b This is a schematic diagram of the microwave absorption properties of the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 2;

[0031] Figure 2c This is a schematic diagram of the microwave absorption properties of the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 3;

[0032] Figure 2d This is a schematic diagram of the microwave absorption properties of the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 4;

[0033] Figure 2e This is a schematic diagram of the microwave absorption properties of the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 5;

[0034] Figure 3 Comparison of the sound absorption properties of MXene / nanocellulose / catechol modified polyvinyl alcohol aerogels prepared in Examples 1, 2, 3, 4 and 5;

[0035] Figure 4a The X-ray diffraction pattern and 30-day microwave absorption performance comparison diagram of the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 3 are shown.

[0036] Figure 4b The image shows the microwave absorption performance of the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 3 after being placed in air for 10 days.

[0037] Figure 4cThe image shows the microwave absorption performance of the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 3 after being placed in air for 20 days.

[0038] Figure 4d The image shows the microwave absorption performance of the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 3 after being placed in air for 30 days.

[0039] Figure 4e The image shows the microwave absorption performance of the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 3 after being placed in air for 70 days.

[0040] Figure 5a This is a schematic diagram of the compression resilience of the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 5;

[0041] Figure 5b The stress-strain diagrams of the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 5 at 10%, 20%, and 30% strain are shown.

[0042] Figure 5c The stress-strain diagram is shown for the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 5 after 800 compression-release cycles at 20% strain.

[0043] Figure 5d The graph shows the retention rate of the original compressive strength of the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared in Example 5 after 800 compression-release cycles at 20% strain. Detailed Implementation

[0044] The present invention will now be described in detail with reference to various embodiments. However, it should be noted that these embodiments are not intended to limit the present invention. Equivalent changes or substitutions in function, method, or structure made by those skilled in the art based on these embodiments are all within the protection scope of the present invention.

[0045] The purpose of this invention is to produce a method for manufacturing a compressible, antioxidant cellulose-based microwave-absorbing and sound-absorbing composite aerogel containing MXene, comprising the following steps:

[0046] (1) Concentration of few-layer MXene suspension.

[0047] Centrifuge the few-layer structure MXene suspension with a certain solid content at 10000 rpm for 10 min, discard part of the supernatant and shake well.

[0048] Depending on the solid content of the few-layer structure MXene suspension and the volume of the supernatant after decanting, the solid content of the MXene suspension is controlled to be between 2 and 10 mg / mL.

[0049] (2) Preparation of catechol-modified polyvinyl alcohol.

[0050] Polyvinyl alcohol powder was added to dimethyl sulfone (DMSO) and stirred continuously while heating until completely dissolved. After cooling to room temperature, a certain amount of 3,4-dihydroxybenzaldehyde (DBA) and p-toluenesulfonic acid monohydrate (TsOH) were added, and an acetalization reaction was carried out under nitrogen protection and heating conditions. The mixture was cooled to room temperature and precipitated twice in acetone. The precipitate was then vacuum dried under certain conditions to obtain catechol-modified polyvinyl alcohol solid. The synthesized catechol-modified polyvinyl alcohol was dissolved in deionized water and completely dissolved under heating conditions to obtain a catechol-modified polyvinyl alcohol solution.

[0051] The mass ratio of polyvinyl alcohol, 3,4-dihydroxybenzaldehyde and p-toluenesulfonic acid monohydrate is 1:(0.07~0.08):(0.2~0.3); the dissolution temperature of polyvinyl alcohol is 80℃; the acetalization reaction temperature is 80℃; the acetalization reaction time is 12h; and the vacuum drying temperature is 45℃.

[0052] (3) Preparation of MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel.

[0053] The cellulose-based solution was added to the catechol-modified polyvinyl alcohol solution described in step two and stirred until homogeneous. The MXene nano-dispersion was then added to the mixed solution and stirred until homogeneous. The solution was then placed in a mold and directionally frozen with liquid nitrogen, followed by freeze-drying in a freeze dryer to obtain an MXene / nanocellulose / catechol-modified polyvinyl alcohol aerogel.

[0054] In step (3), the cellulose-based raw material can be either nanocellulose or carboxylated nanocellulose.

[0055] The solid content of the cellulose-based solution is 1% to 2%; the freeze-drying temperature is -50 to -60°C; and the freeze-drying time is 48 to 72 hours.

[0056] In step (3), the mass ratio of nanocellulose, catechol-modified polyvinyl alcohol and MXene is 1:1:2.

[0057] The preparation method of this invention involves using a compressible, antioxidant cellulose-based microwave and sound-absorbing material with nanofibers as a scaffold, MXene as a conductive filler, and catechol-modified polyvinyl alcohol as an antioxidant. The electromagnetic wave absorption and sound absorption properties of the composite material can be controlled and optimized by adjusting the MXene content. The prepared directional three-dimensional network structure has good compression resilience, recovering its original shape after hundreds of compressions. The catechol groups on the modified polyvinyl alcohol can effectively inhibit the oxidation of MXene, giving the material excellent antioxidant properties.

[0058] The raw materials of this invention are inexpensive and the preparation process is simple, and it has great application prospects in the fields of electromagnetic wave absorption and sound absorption.

[0059] Example 1

[0060] (1) Centrifuge a few-layer MXene suspension with a certain solid content at 10000 rpm for 10 min, discard part of the supernatant, and shake evenly to obtain a stable and uniform black suspension. Adjust the volume of the discarded supernatant according to the solid content of the few-layer MXene suspension to obtain a concentration of 2 mg / mL for the few-layer MXene suspension.

[0061] (2) 1 g of polyvinyl alcohol powder was added to 10 mL of dimethyl sulfone (DMSO) and stirred at 80 °C until completely dissolved. After cooling to room temperature, 75 mg of 3,4-dihydroxybenzaldehyde (DBA) and 25 mg of p-toluenesulfonic acid monohydrate (TsOH) were added, and the mixture was stirred at 80 °C for 12 h under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, and acetone was added to obtain a precipitate. The precipitate was then dried under vacuum at 45 °C for 30 min to obtain catechol-modified polyvinyl alcohol solid. The synthesized catechol-modified polyvinyl alcohol was dissolved in deionized water, stirred at 90 °C for 1 h, and cooled to room temperature to obtain a 2% catechol-modified polyvinyl alcohol solution.

[0062] (3) Take 2g of 2% catechol-modified polyvinyl alcohol solution, add 2% nanocellulose with a mass ratio of 1:1 to catechol-modified polyvinyl alcohol, and stir evenly. Add MXene dispersion with a mass ratio of 1:1 to the mixture and a concentration of 2mg / mL to the mixture solution, stir evenly, then put the solution into a mold and freeze it in liquid nitrogen for 2min, and then freeze-dry it in a freeze dryer at -58°C for 48h to obtain MXene / nanocellulose / catechol-modified polyvinyl alcohol aerogel.

[0063] The composite aerogel prepared in the embodiments of the present invention was tested for microwave absorption and sound absorption properties. The microwave absorption properties exhibited in the X-ray band are as follows: Figure 2aAs shown, the minimum reflection coefficient for a thickness of 13.15 mm can reach -15.66 dB, indicating that the invention has certain wave absorption performance; the sound absorption performance exhibited in the frequency range of 1000 Hz-6300 Hz is as follows: Figure 3 As shown, for a sample with a thickness of 30 mm, the sound absorption coefficient is >0.2 dB, which indicates that the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared by this invention has good sound absorption performance.

[0064] Example 2

[0065] (1) A few-layer MXene suspension with a certain solid content was centrifuged at 10000 rpm for 10 min. After discarding part of the supernatant, the suspension was shaken to obtain a stable and uniform black suspension. Based on the solid content of the few-layer MXene suspension, the volume of the supernatant was adjusted to obtain a concentration of 4 mg / mL for the few-layer MXene suspension.

[0066] (2) 1 g of polyvinyl alcohol powder was added to 10 mL of dimethyl sulfone (DMSO) and stirred at 80 °C until completely dissolved. After cooling to room temperature, 75 mg of 3,4-dihydroxybenzaldehyde (DBA) and 25 mg of p-toluenesulfonic acid monohydrate (TsOH) were added, and the mixture was stirred at 80 °C for 12 h under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, and acetone was added to obtain a precipitate. The precipitate was then dried under vacuum at 45 °C for 30 min to obtain catechol-modified polyvinyl alcohol solid. The synthesized catechol-modified polyvinyl alcohol was dissolved in deionized water, stirred at 90 °C for 1 h, and cooled to room temperature to obtain a 2% catechol-modified polyvinyl alcohol solution.

[0067] (3) Take 2g of a 2% catechol-modified polyvinyl alcohol solution, add 2% nanocellulose at a mass ratio of 1:1 with the catechol-modified polyvinyl alcohol, and stir until homogeneous. Add MXene dispersion at a mass ratio of 1:1 with the mixture and a concentration of 4mg / mL to the mixed solution, stir until homogeneous, then place the solution in a mold and freeze it directionally with liquid nitrogen for 5min, and then freeze-dry it in a freeze dryer at -55℃ for 48h to obtain MXene / nanocellulose / catechol-modified polyvinyl alcohol aerogel.

[0068] The composite aerogel prepared in the embodiments of the present invention was tested for microwave absorption and sound absorption properties. The microwave absorption properties exhibited in the X-ray band are as follows: Figure 2b As shown, the minimum reflection coefficient of a 2.45mm thickness can reach -37.87dB, indicating that this invention has excellent wave absorption performance; the sound absorption performance exhibited in the 1000Hz-6300Hz frequency range is as follows: Figure 3As shown, the sound absorption coefficient of the sample with a thickness of 30 mm is >0.2 dB, which indicates that the invention has good sound absorption performance.

[0069] Example 3

[0070] (1) A few-layer structure MXene suspension with a certain solid content was centrifuged at 10000 rpm for 10 min. After discarding part of the supernatant, the suspension was shaken evenly to obtain a stable and uniform black suspension. Based on the solid content of the few-layer structure MXene suspension, the volume of the supernatant was adjusted to obtain a concentration of 6 mg / mL for the few-layer structure MXene suspension.

[0071] (2) 1 g of polyvinyl alcohol powder was added to 10 mL of dimethyl sulfone (DMSO) and stirred at 80 °C until completely dissolved. After cooling to room temperature, 75 mg of 3,4-dihydroxybenzaldehyde (DBA) and 25 mg of p-toluenesulfonic acid monohydrate (TsOH) were added, and the mixture was stirred at 80 °C for 12 h under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, and acetone was added to obtain a precipitate. The precipitate was then dried under vacuum at 45 °C for 30 min to obtain catechol-modified polyvinyl alcohol solid. The synthesized catechol-modified polyvinyl alcohol was dissolved in deionized water, stirred at 90 °C for 1 h, and cooled to room temperature to obtain a 2% catechol-modified polyvinyl alcohol solution.

[0072] (3) Take 2g of a 2% catechol-modified polyvinyl alcohol solution, add 2% nanocellulose at a mass ratio of 1:1 with the catechol-modified polyvinyl alcohol, and stir until homogeneous. Add MXene dispersion at a mass ratio of 1:1 with the mixture and a concentration of 6mg / mL to the mixed solution, stir until homogeneous, then place the solution in a mold and freeze it directionally with liquid nitrogen for 3min, and then freeze-dry it in a freeze dryer at a temperature of -60℃ for 48h to obtain MXene / nanocellulose / catechol-modified polyvinyl alcohol aerogel.

[0073] pass Figures 1a-1d The photographs and scanning electron microscope images show that the prepared MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel has a layered structure. Figure 1 initially shows a regular layered structure in the aerogel. However, while this layered structure is related to good sound absorption and wave absorption properties, it doesn't provide a direct conclusion. Further observation and verification are needed.

[0074] And through Figure 2c and Figure 3 As can be clearly seen, the performance verification in this embodiment, specifically, involves testing the microwave absorption and sound absorption performance of the composite aerogel prepared in this embodiment. The microwave absorption performance exhibited in the X-ray band is as follows: Figure 2cAs shown, the minimum reflection coefficient of a 2.8mm thickness can reach -46.85dB, and the effective absorption bandwidth can cover the entire X-band (8.2-12.4GHz), indicating that the invention has excellent wave absorption performance; the sound absorption performance exhibited in the 1000Hz-6300Hz frequency range is as follows... Figure 3 As shown, the sound absorption coefficient of the sample with a thickness of 30 mm is >0.2 dB, which indicates that the invention has good sound absorption performance.

[0075] The composite aerogels prepared in the embodiments of the present invention were subjected to lifetime testing, such as... Figure 4a As shown, after the CNF / PVA-CA / MXene-6 composite aerogel was placed at room temperature for 70 days, the characteristic peak of MXene (~6.1°) could still be observed by XRD test. This indicates that the catechol-modified polyvinyl alcohol prevented the oxidation of MXene in the composite aerogel, thus preserving its microwave absorption properties. Figure 4b ~e, after being placed at room temperature for 70 days, the effective absorption bandwidth of the CNF / PVA-CA / MXene-6 composite aerogel can cover the entire X-band (8.2~12.4GHz), and its minimum reflection coefficient at 2.65mm can reach -55.95dB. This indicates that the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel of this invention has excellent microwave absorption performance stability.

[0076] Example 4

[0077] (1) Centrifuge a few-layer MXene suspension with a certain solid content at 10000 rpm for 10 min, discard part of the supernatant, and shake evenly to obtain a stable and uniform black suspension. Adjust the volume of the discarded supernatant according to the solid content of the few-layer MXene suspension to obtain a concentration of 8 mg / mL for the few-layer MXene suspension.

[0078] (2) 1 g of polyvinyl alcohol powder was added to 10 mL of dimethyl sulfone (DMSO) and stirred at 80 °C until completely dissolved. After cooling to room temperature, 75 mg of 3,4-dihydroxybenzaldehyde (DBA) and 25 mg of p-toluenesulfonic acid monohydrate (TsOH) were added, and the mixture was stirred at 80 °C for 12 h under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, and acetone was added to obtain a precipitate. The precipitate was then dried under vacuum at 45 °C for 30 min to obtain catechol-modified polyvinyl alcohol solid. The synthesized catechol-modified polyvinyl alcohol was dissolved in deionized water, stirred at 90 °C for 1 h, and cooled to room temperature to obtain a 2% catechol-modified polyvinyl alcohol solution.

[0079] (3) Take 2g of a 2% catechol-modified polyvinyl alcohol solution, add 2% nanocellulose at a mass ratio of 1:1 with the catechol-modified polyvinyl alcohol, and stir until homogeneous. Add MXene dispersion at a mass ratio of 1:1 with the mixture and a concentration of 8mg / mL to the mixed solution, stir until homogeneous, then place the solution in a mold and freeze it directionally with liquid nitrogen for 1 min, and then freeze-dry it in a freeze dryer at a temperature of -65℃ for 48 h to obtain MXene / nanocellulose / catechol-modified polyvinyl alcohol aerogel.

[0080] The composite aerogel prepared in the embodiments of the present invention was subjected to microwave absorption and sound absorption tests. The microwave absorption performance exhibited in the X-ray band is as follows: Figure 2d As shown, the minimum reflection coefficient of a 4.05mm thickness can reach -35.82dB, and the effective absorption bandwidth can cover the entire X-band (8.2~12.4GHz), indicating that this invention has excellent wave absorption performance; the sound absorption performance exhibited in the frequency range of 1000Hz~6300Hz is as follows: Figure 3 As shown, the sound absorption coefficient of the sample with a thickness of 30 mm is >0.2 dB, which indicates that the invention has good sound absorption performance.

[0081] Example 5

[0082] (1) Centrifuge a few-layer MXene suspension with a certain solid content at 10000 rpm for 10 min, discard part of the supernatant, and shake evenly to obtain a stable and uniform black suspension. Adjust the volume of the discarded supernatant according to the solid content of the few-layer MXene suspension to obtain a concentration of 10 mg / mL for the few-layer MXene suspension.

[0083] (2) 1 g of polyvinyl alcohol powder was added to 10 mL of dimethyl sulfone (DMSO) and stirred at 80 °C until completely dissolved. After cooling to room temperature, 75 mg of 3,4-dihydroxybenzaldehyde (DBA) and 25 mg of p-toluenesulfonic acid monohydrate (TsOH) were added, and the mixture was stirred at 80 °C for 12 h under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, and acetone was added to obtain a precipitate. The precipitate was then dried under vacuum at 45 °C for 30 min to obtain catechol-modified polyvinyl alcohol solid. The synthesized catechol-modified polyvinyl alcohol was dissolved in deionized water, stirred at 90 °C for 1 h, and cooled to room temperature to obtain a 2% catechol-modified polyvinyl alcohol solution.

[0084] (3) Take 2g of a 2% catechol-modified polyvinyl alcohol solution, add 2% nanocellulose at a mass ratio of 1:1 with the catechol-modified polyvinyl alcohol, and stir until homogeneous. Add MXene dispersion at a mass ratio of 1:1 with the mixture and stir until homogeneous. Then, place the solution in a mold and freeze it directionally with liquid nitrogen for 2 min. Then, freeze-dry it in a freeze dryer at -62℃ for 48 h to obtain MXene / nanocellulose / catechol-modified polyvinyl alcohol aerogel.

[0085] The composite aerogel prepared in the embodiments of the present invention was subjected to microwave absorption and sound absorption tests. The microwave absorption performance exhibited in the X-ray band is as follows: Figure 2e As shown, the minimum reflection coefficient of a 2.55mm thickness can reach -27.51dB, and the effective absorption bandwidth can cover the entire X-band (8.2~12.4GHz), indicating that this invention has excellent wave absorption performance; the sound absorption performance exhibited in the frequency range of 1000Hz~6300Hz is as follows: Figure 3 As shown, the sound absorption coefficient of the sample with a thickness of 30 mm is >0.2 dB, which indicates that the invention has good sound absorption performance.

[0086] The composite aerogels prepared in the embodiments of the present invention were subjected to compression-resilience performance tests, such as... Figure 5a As shown, the CNF / PVA-CA / MXene-10 composite aerogel (0.08g) can withstand a load of 50g (approximately 600 times its own weight); after compression along the perpendicular growth direction of the composite aerogel using a 50g weight, repeated three times, the compressed shape can basically recover. Furthermore, when different degrees of compression (10%, 20%, and 30% strain) are applied to the CNF / PVA-CA / MXene-10 composite aerogel along the perpendicular growth direction, as shown... Figure 5b As shown, its stress-strain diagram exhibits a continuous closed loop, indicating that the composite aerogel possesses excellent compressive-rebound properties. Figure 5c As shown in Figures d and d, the CNF / PVA-CA / MXene-10 composite aerogel under 20% strain and perpendicular to the growth direction underwent 800 compression-rebound cycles, and the compression recovery rate of the composite aerogel was still as high as 80%. The test results indicate that the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel has good structural stability.

[0087] As can be seen from the above embodiments and related experimental tests, the MXene / nanocellulose / catechol modified polyvinyl alcohol aerogel prepared by the preparation method of the present invention has good wave absorption performance, sound absorption performance, compression-resilience performance and antioxidant performance.

[0088] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0089] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a composite aerogel containing MXene, characterized in that, Includes the following steps, The few-layer MXene suspension was centrifuged and concentrated to obtain few-layer MXene dispersions of different concentrations; Under nitrogen protection, polyvinyl alcohol was modified by acetalization to obtain catechol-modified polyvinyl alcohol. The preparation of the catechol-modified polyvinyl alcohol specifically involves adding polyvinyl alcohol powder to dimethyl sulfone, stirring continuously and heating until it is completely dissolved, cooling to room temperature, and then adding 3,4-dihydroxybenzaldehyde and p-toluenesulfonic acid monohydrate to carry out an acetalization reaction. Modified polyvinyl alcohol was dissolved in water to obtain a modified polyvinyl alcohol solution. Then, nanocellulose aqueous solution and few-layer MXene dispersion were added sequentially. After the modified polyvinyl alcohol solution and nanocellulose aqueous solution were stirred evenly, the few-layer MXene dispersion was added and stirred evenly. The mixture was poured into a mold and directionally frozen with liquid nitrogen for 2-5 minutes. Then, it was placed in a freeze dryer at -55℃ to -62℃ and vacuum dried for 48 hours to obtain a composite aerogel containing MXene. The mass fraction of the nanocellulose aqueous solution is 1%-2%; The concentration of the few-layer MXene suspension obtained after centrifugation and concentration is 2-10 mg / mL; The composite aerogel containing MXene is a composite aerogel with a regular three-dimensional network structure; The mass ratio of the nanocellulose, modified polyvinyl alcohol, and MXene is 1:1:

2.

2. The method for preparing the composite aerogel containing MXene according to claim 1, characterized in that, It also includes the preparation of a few-layer MXene suspension, specifically prepared by etching a MAX phase precursor with LiF-HCl, wherein the MAX phase precursor includes Ti3C2T X Solution, Ti3N2T X Solution, Ti3CNT X Solution or Ti2CT X One or more of the substances in the solution.

3. The method for preparing the composite aerogel containing MXene according to claim 1, characterized in that, The centrifugation speed for concentrating the few-layer MXene suspension is 10,000 rpm; the centrifugation time is 10-20 min.

4. The method for preparing the composite aerogel containing MXene according to claim 1, characterized in that, The mass ratio of polyvinyl alcohol, 3,4-dihydroxybenzaldehyde and p-toluenesulfonic acid monohydrate is 1:(0.07-0.08):(0.2-0.3); the acetalization reaction temperature is 80°C.

5. The method for preparing the composite aerogel containing MXene according to claim 1, characterized in that, After acetalization, the modified polyvinyl alcohol is obtained by acetone precipitation and vacuum drying.

6. The method for preparing the composite aerogel containing MXene according to claim 1, characterized in that, The modified polyvinyl alcohol is dissolved in deionized water at 80°C to obtain the modified polyvinyl alcohol solution.

Images