A multifunctional terahertz absorbing fabric based on MXenes materials and its preparation method

Abstract

The present invention belongs to the field of electromagnetic wave absorbing materials, and specifically provides a multifunctional terahertz wave absorbing fabric based on MXenes materials and a preparation method thereof, aiming to solve the problems of narrow absorption bandwidth, single function, and easy oxidation existing in MXenes absorbing materials; based on the fiber microstructure in the matrix, combining the conductance loss and Ohmic loss of MXenes materials, waterborne polyurethane (WPU) is sprayed on the surface of the absorbing fabric for modification to realize a multifunctional terahertz absorbing material. The absorption efficiency can reach 100% under electromagnetic waves of 0.3 - 1.2 THz. At the same time, the water contact angle and rolling angle reach 151.3° and 0° respectively, with good self-cleaning performance, and the absorption performance of the fabric remains above 99% after self-cleaning. In addition, it has excellent acid and alkali resistance and environmental adaptability.

Description

Technical Field

[0001] The present invention belongs to the field of electromagnetic wave absorbing materials, and particularly provides a multifunctional terahertz wave absorbing fabric based on MXenes materials and a preparation method thereof. Background Art

[0002] With the rapid development of electronic technology, the widespread application of electromagnetic waves in fields such as wireless communication, information transmission, and radar detection has made the problem of electromagnetic wave radiation increasingly prominent, seriously threatening human life and health, the normal operation of instruments, and the survival ability of special equipment. Currently, materials with high electromagnetic wave loss capabilities can effectively absorb electromagnetic waves and are important materials for dealing with electromagnetic wave radiation problems and improving the stealth capabilities of special equipment; moreover, in the field of life and health protection, electromagnetic wave absorbing materials can effectively reduce the damage of electromagnetic radiation to the human body and other organisms; at the same time, the next generation of electronic devices is continuously developing towards the direction of flexible wearable and multifunctional, and whether the electromagnetic wave absorbing materials have flexibility and multifunctionality has become a decisive factor for their wide application.

[0003] MXenes materials refer to two-dimensional layered materials composed of transition metal carbides, nitrides, or carbonitrides, specifically materials with an M n+1 X n T x element composition system, where M represents an early transition metal element, X represents C or N, and T represents the group / modifier on the surface of the two-dimensional material. The value range of n is usually 1 to 3. MXenes materials were first prepared by wet etching by Professor Yury Gogotsi and Professor Michel Barsoum. They have a high specific surface area and abundant polar functional groups, and provide a large number of dipole loss centers, with higher absorption efficiency than metals and carbon, making them considered an excellent wave absorber material. However, the composite materials prepared by traditional coated wave absorbers have limitations in terms of shape adaptability, portability, and cutability.

[0004] The microwave-absorbing fabric has the characteristics of flexibility, foldability, portability, cutability and wearability. Combining microwave-absorbing agents with textiles can overcome many limitations of flexibility. Moreover, as the basic component of textiles, fibers are used as the framework of microwave-absorbing materials. This not only can obtain good impedance matching characteristics, but also has the function of carrying microwave-absorbing agents, enabling more electromagnetic waves to enter the material and be absorbed. In recent years, researchers have done a lot of pioneering work, using wet spinning, coating, electrospinning and hyperbolic methods to design various absorbing textile materials. For example, in the literature "Gupta S, Chang C, Anbalagan A K, et al. Composites Science and Technology, 2020, 188: 107994.", a composite microwave-absorbing material of zinc oxide (ZnO) and reduced graphene oxide (rGO) was prepared by in-situ sol-gel method and thermal reduction method, and the electromagnetic shielding effectiveness in the X-band was studied with the fabric as the matrix. Another example is the literature "Zhang H, Ji H, Dai G, et al. Composites Part A: Applied Science and Manufacturing, 2022, 163: 107163.", in which a composite textile fiber structure with PET textile fibers as the matrix and MXene as the conductive filler was constructed, and its effective absorption bandwidth covered the entire X-band. However, to apply absorbing textile materials in practice, not only the microwave-absorbing performance of the materials needs to be ensured, but also various environmental requirements need to be met.

[0005] At present, the electromagnetic wave frequencies radiated by new communication devices are getting higher and higher, and the research on high-frequency terahertz microwave-absorbing materials has received wide attention. Conventional microwave-absorbing materials have single functions and are prone to oxidation, and there is a severe shortage of terahertz microwave-absorbing materials with functions such as self-cleaning, flexibility, ultrathinness and stability. While ensuring flexibility and microwave-absorbing performance, multifunctional microwave-absorbing textiles with characteristics such as corrosion resistance, waterproofness and self-cleaning have very important practical prospects and commercial values. Multifunctional microwave-absorbing textiles are also required to have advantages such as relatively light weight, good microwave-absorbing property, easy bending, arbitrary cutability, non-toxic and environmentally friendly. To solve these problems, the present invention provides a multifunctional terahertz microwave-absorbing fabric based on MXenes materials. Summary of the Invention

[0006] The object of the present invention is to provide a multifunctional terahertz absorbing fabric based on MXenes material and its preparation method, so as to solve the problems of narrow absorption bandwidth, single function and easy oxidation existing in MXenes absorbing materials; based on the fiber microstructure in the matrix, combining the conductance loss and ohmic loss of MXenes material, waterborne polyurethane (WPU) is sprayed on the surface of the absorbing fabric for modification to realize a multifunctional terahertz absorbing material, and the absorption efficiency can reach 100% under electromagnetic waves of 0.3 - 1.2 THz. At the same time, the water contact angle and rolling angle reach 151.3° and 0° respectively, with good self-cleaning performance, and the absorption performance of the fabric remains above 99% after self-cleaning. In addition, it has excellent acid and alkali resistance and environmental adaptability.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A multifunctional terahertz absorbing fabric based on MXenes material, characterized in that the multifunctional terahertz absorbing fabric is formed by spraying a WPU layer on the surface (complete outer surface) of the MXenes absorbing fabric, and the MXenes absorbing fabric is formed by soaking the fabric in the MXenes dispersion liquid.

[0009] Further, the MXenes material adopts Ti 3 C 2 or V 2 C.

[0010] Further, the surface of the fabric has short hairs with a length of 0.4 - 0.8 mm.

[0011] Further, the preparation method of the multifunctional terahertz absorbing fabric based on MXenes material includes the following steps:

[0012] Step 1, synthesis of MXenes dispersion liquid;

[0013] The MAX phase powder is selectively etched and intercalated with a mixed acid, and then the MXenes dispersion liquid is synthesized by centrifugal stirring;

[0014] Step 2, preparation of MXenes absorbing fabric;

[0015] The fabric is soaked in the MXenes dispersion liquid and dried to obtain the MXenes absorbing fabric;

[0016] Step 3, preparation of WPU-MXenes absorbing fabric;

[0017] A layer of WPU emulsion is sprayed on the surface of the MXenes wave-absorbing fabric by a spraying process to form a WPU layer, thus preparing a multifunctional terahertz wave-absorbing fabric based on MXenes materials.

[0018] Further, in step 1, the mixed acid is an aqueous mixed solution of hydrofluoric acid (HF) and hydrochloric acid (HCl), and the volume ratio of the mixed acid is HCl:HF:H 2 O = 12:2.5:5. A magnetic stirrer is used to stir at a speed of 200 - 400 rpm, and MAX phase powder is added simultaneously. Then, a constant-temperature magnetic stirrer is used to carry out centrifugal stirring etching at a speed of 450 - 800 rpm at 35°C for 24 hours to obtain an MXenes dispersion liquid, and its concentration range is 1.0 - 3.0 mg / ml.

[0019] Further, in step 2, the fabric needs to be completely immersed in a container filled with the MXenes dispersion liquid, and the liquid level height needs to be 3 - 5 mm higher than the fabric thickness. When the color of the fabric turns dark black, take out the fabric and dry it to obtain the MXenes wave-absorbing fabric.

[0020] Further, in step 3, the PU solid content of the WPU emulsion is (10 ± 2)%. The spraying process uses a spray gun and an air compressor to atomize the WPU emulsion into uniform and fine droplets, which adhere to the surface of the MXenes wave-absorbing fabric. The main parameters of the spraying process are: the spray gun orifice diameter is 0.5 - 1.5 mm, the air compressor pressure is 0.2 - 0.4 MPa, the spraying distance is 180 - 220 mm, the spraying angle is 65 - 75 degrees, and the spraying speed is 5 - 8 m / min.

[0021] Based on the above technical solutions, the beneficial effects of the present invention are as follows:

[0022] The present invention provides a multifunctional terahertz absorbing fabric (WPU-MXenes absorbing fabric) based on MXenes materials and a preparation method thereof. Based on the surface impedance matching and the absorption loss characteristics of MXenes nanosheets, the prepared WPU-MXenes absorbing fabric can achieve an absorption efficiency of 100% under the incident electromagnetic wave of 0.3 - 1.2 THz. At the same time, the surface of the fabric is modified by spraying WPU, which increases the superhydrophobic performance of the absorbing and shielding fabric. The water contact angle and rolling angle of the WPU-MXenes absorbing fabric reach 151.3° and 0° respectively, with good self-cleaning performance. Moreover, the absorption performance of the fabric remains above 99% after self-cleaning, and it exhibits excellent acid and alkali resistance and environmental adaptability. In addition, the present invention also provides a preparation method of the WPU-MXenes absorbing fabric, which can realize large-scale preparation. The WPU layer introduced by spraying plays a good protective role for the absorbing fabric, effectively increasing the service life of the absorbing fabric, and having great potential in applications such as electromagnetic wave absorption and shielding, wearable shielding fabrics, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic flow chart of the synthesis method of the MXenes dispersion liquid in the embodiment of the present invention.

[0024] Figure 2 It is a schematic flow chart of the preparation method of the MXenes absorbing fabric in the embodiment of the present invention.

[0025] Figure 3 It is a schematic flow chart of the preparation method of the WPU-MXenes absorbing fabric in the embodiment of the present invention.

[0026] Figure 4 It is the SEM image of the MXenes dispersion liquid and the TEM image of the single-layer MXenes nanosheet in the embodiment of the present invention. Among them, (a) is the SEM image of the MXenes dispersion liquid, and (b) is the TEM image of the single-layer MXenes nanosheet.

[0027] Figure 5 It is a comparative diagram of the surface morphologies of the MXenes absorbing fabric and the WPU-MXenes absorbing fabric in the embodiment of the present invention. Among them, (a) is the optical image of the MXenes absorbing fabric, (b) is the optical image of the WPU-MXenes absorbing fabric, (c) is the surface SEM image of the MXenes absorbing fabric, and (d) is the surface SEM image of the WPU-MXenes absorbing fabric.

[0028] Figure 6Results diagrams of electromagnetic reflection, transmission, and absorption properties of MXenes absorbing fabric in the range of 0.3 - 1.2 THz in the embodiments of the present invention. Among them, (a) is the transmission efficiency diagram, (b) is the reflection efficiency diagram, and (c) is the absorption efficiency diagram.

[0029] Figure 7 Comparison diagrams of electromagnetic transmission, reflection, and absorption properties of MXenes absorbing fabric and WPU-MXenes absorbing fabric in the range of 0.3 - 1.2 THz in the embodiments of the present invention. Among them, (a) is the transmission efficiency diagram, (b) is the reflection efficiency diagram, and (c) is the absorption efficiency diagram.

[0030] Figure 8 Test result diagrams of water contact angles and water rolling angles of MXenes absorbing fabric and WPU-MXenes absorbing fabric in the embodiments of the present invention. Among them, (a) is the water contact angle of MXenes absorbing fabric, (b) is the water contact angle of WPU-MXenes absorbing fabric, (c) is the water rolling angle of MXenes absorbing fabric, and (d) is the water rolling angle of WPU-MXenes absorbing fabric.

[0031] Figure 9 Test result diagrams of the self-cleaning ability of MXenes absorbing fabric and WPU-MXenes absorbing fabric in the embodiments of the present invention.

[0032] Figure 10 Comparison diagrams of terahertz absorption properties of MXenes absorbing fabric and WPU-MXenes absorbing fabric before and after self-cleaning in the embodiments of the present invention. Among them, (a) is MXenes absorbing fabric, and (b) is WPU-MXenes absorbing fabric.

[0033] Figure 11 Test result diagrams of the corrosion resistance of MXenes absorbing fabric and WPU-MXenes absorbing fabric in the embodiments of the present invention. Among them, (a) is the water contact angle of WPU-MXenes absorbing fabric after being soaked in different solutions, (b) is the surface resistance of WPU-MXenes absorbing fabric after being soaked in different solutions; (c) is the test result diagram of terahertz absorption properties of MXenes absorbing fabric and WPU-MXenes absorbing fabric after being treated with acid and alkali solutions for 48 hours.

[0034] Figure 12 Physical diagram of WPU-MXenes absorbing fabric in the embodiments of the present invention.

[0035] Figure 13This is the optical image and Fico terahertz reflection spectral imaging result of the patterned WPU-MXenes absorbing fabric in the embodiment of the present invention. Among them, (a) is the optical image of the WPU-MXenes absorbing fabric with cross maple leaf and "UESTC" letter patterns, and (b) is the Fico terahertz reflection spectral imaging result of the WPU-MXenes absorbing fabric with cross maple leaf and "UESTC" letter patterns. Detailed implementation mode

[0036] To make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments.

[0037] The present invention aims at the deficiencies of the existing technology and proposes a multifunctional terahertz absorbing fabric based on MXenes materials (hereinafter simply referred to as WPU-MXenes absorbing fabric) and its preparation method. The prepared WPU-MXenes absorbing fabric can achieve an absorption efficiency of 100% under the incident electromagnetic wave of 0.3-1.2 THz. Moreover, the sprayed WPU (waterborne polyurethane) layer plays a good protective role for the absorbing fabric, effectively increasing the service life of the absorbing fabric and adding its self-cleaning and corrosion-resistant characteristics.

[0038] This embodiment provides a WPU-MXenes absorbing fabric, and its preparation method is as Figures 1 to 3 shown, and specifically includes the following steps:

[0039] Step 1, synthesis of MXenes dispersion liquid, as Figure 1 shown;

[0040] Selectively etch and intercalate the MAX phase powder with a mixed acid, and then synthesize the MXenes dispersion liquid by centrifugal stirring method;

[0041] Specifically, the mixed acid is an aqueous mixed solution of hydrofluoric acid (HF) and hydrochloric acid (HCl), and the volume ratio of the mixed acid is HCl:HF:H 2 O = 12:2.5:5. Then use a magnetic stirrer to adjust the rotation speed to 200-400 revolutions per minute, add the MAX phase powder while rotating, and then put the plastic bottle containing the mixed acid and the MAX phase powder into a constant temperature magnetic stirring water bath, adjust the rotation speed to 450-800 revolutions per minute, the temperature is 35°, set the etching time to 24 h, and the concentration range of the prepared MXenes dispersion liquid is 1.0-3.0 mg / ml;

[0042] Step 2, preparation of MXenes absorbing fabric, as Figure 2 shown;

[0043] Use a fabric with a rich fibrous microstructure on its surface, such as suede fabric, and prepare MXenes absorbing fabric by soaking it in an MXenes dispersion and then drying it, so that MXenes nanosheets are effectively adsorbed on the fabric fibers, which is conducive to the formation of many absorbing and shielding films, thus achieving the effect of high electromagnetic absorption;

[0044] Specifically, the fabric needs to be completely immersed in a container filled with MXenes dispersion, and the liquid level height should be 3 - 5 mm higher than the fabric thickness. When the fabric color turns dark black, take out the fabric and dry it to obtain MXenes absorbing fabric;

[0045] Step 3: Preparation of WPU-MXenes absorbing fabric, as Figure 3 shown;

[0046] Use a spraying process to spray a layer of WPU emulsion with low surface energy, good corrosion resistance and strong waterproofness on the surface of MXenes absorbing fabric to prepare WPU-MXenes absorbing fabric; Since the WPU layer is covered on the surface of the fibers of the absorbing fabric, while enhancing the interfacial interaction between MXenes nanosheets and suede fabric fibers, it can also protect the MXenes material from oxidation and degradation, thus improving the overall chemical corrosion resistance and self-cleaning ability of the absorbing fabric;

[0047] Specifically, the PU solid content of the WPU emulsion is (10 ± 2)%, and in the spraying process, through a spray gun and an air compressor, the WPU emulsion is atomized into uniform and fine droplets and adheres to the surface of the MXenes absorbing fabric; The main parameters of the spraying process: the spray gun orifice diameter is 0.5 - 1.5 mm, the air compressor pressure is 0.2 - 0.4 MPa, the spraying distance is 180 - 220 mm, the spraying angle is 65 - 75 degrees, and the spraying speed is 5 - 8 m / min.

[0048] The detailed structural characteristics of the MXenes dispersion prepared in this example are as Figure 4 shown. The scanning electron microscope (SEM) image of the characterized MXenes dispersion shows a typical accordion-like microstructure, with a certain interval between each layer of MXenes nanosheets, proving that the metal layer in the MAX phase has been etched away; Moreover, the transmission electron microscope (TEM) test of single-layer MXenes nanosheets further confirms the single-molecule-layer MXenes nanosheets and their single-crystal structure with a hexagonal base lattice; These results indicate that a high-quality MXenes dispersion has been successfully prepared.

[0049] As Figure 5The figure shows the comparison of the surface morphologies of MXenes microwave-absorbing fabric and WPU-MXenes microwave-absorbing fabric. Figure 5 As can be seen from the comparison between (a) and (b), the surface of the suede fabric after WPU treatment is smoother and darker in color; after the WPU surface treatment, the surface morphology of the microwave-absorbing fabric remains unchanged. As Figure 5 shown in (c), the surface SEM characterization image of the MXenes microwave-absorbing fabric shows that under the driving force of van der Waals forces and hydrogen bonds, the MXenes nanosheets are firmly adsorbed on the surface of the fabric fibers, bridging and interconnecting with adjacent fibers, and a rich MXenes membrane structure is formed within the fabric, thereby increasing the absorption loss characteristics of the fabric. As Figure 5 shown in (d), the surface SEM image of the WPU-MXenes microwave-absorbing fabric after WPU treatment is presented. From a detailed perspective, the MXenes membrane is covered by a thin layer of WPU polymer, resulting in a reduction in the surface roughness of the fibers and the formation of a micro-nano structure similar to a bird's nest. In addition, the SEM structure of the WPU-MXenes microwave-absorbing fabric is similar to that of the MXenes microwave-absorbing fabric, indicating that the addition of the WPU solution does not affect the dispersion structure of the MXenes nanosheets within the fabric and plays a role in preventing the oxidation of MXenes when attached to the surface.

[0050] Next, the electromagnetic absorption ability and versatility of the multifunctional terahertz microwave-absorbing fabric (WPU-MXenes microwave-absorbing fabric) based on MXenes materials provided in this embodiment will be described in detail.

[0051] When electromagnetic waves are incident on the surface of an object, reflection waves usually occur due to the impedance discontinuity on the surface, while microwave-absorbing materials have the ability to absorb and dissipate electromagnetic waves; therefore, if it is assumed that the total energy of the incident electromagnetic waves is 1, the following relationship holds for the reflection efficiency R, transmission efficiency T, and absorption efficiency A of the microwave-absorbing material:

[0052] A = 1 - R - T

[0053] Among them, the coefficients of R and T can be obtained in the form of scattering parameters S 11 、S 12 、S 21 、S 22 as follows:

[0054] R = |S 11 | 2 = |S 22 | 2

[0055] T = |S 21 | 2 = |S 12 | 2

[0056] According to the above formula, to improve the wave absorption performance and shielding efficiency of electromagnetic wave absorbing materials, it is necessary to reduce the transmission coefficient and reflection coefficient of the materials; first, to achieve the minimum surface reflection coefficient, it is necessary to ensure that as much electromagnetic wave as possible can enter the absorber; based on the principle of electromagnetic wave propagation, the reflection impedance matching and normal incidence expressions of the material can be derived as follows:

[0057] R=(Z-Z 0 ) / (Z+Z 0 )

[0058]

[0059]

[0060] where R is the reflection coefficient, Z is the wave impedance at the material interface, Z 0 ≈377Ω is the free space impedance, E and H are the electric field strength and magnetic field strength respectively, μ r and μ 0 represent the relative permeability and vacuum permeability of the wave absorbing material respectively, ε r and ε 0 represent the relative permittivity and vacuum permittivity of the wave absorbing material respectively; therefore, to minimize the reflection of electromagnetic waves, it is necessary to ensure that Z and Z 0 are maximally matched, that is, μ r ≈ε r .

[0061] On this basis, in this embodiment, the electromagnetic reflection, transmission and absorption performances (in the range of 0.3 - 1.2 THz) of MXenes wave absorbing fabrics soaked in different MXenes dispersions are compared. As Figure 6 shown, the MXenes dispersions include Ti 3 C 2 , V 2 C, Mo 2 Ti 2 C 3 , Nb 4 C 3 , Mo 2 TiC 2 , Mo 2 C, Nb 2 C solutions; as can be seen from the figure, the reflection efficiencies of the seven MXenes wave absorbing fabrics are all close to 0, indicating that the impedance on the surface of the wave absorbing fabric is matched with the air impedance, and the electromagnetic waves in the range of 0.3 - 1.2 THz incident almost enter the interior of the fabric; however, due to the different absorption loss capabilities of different MXenes dispersions, there are differences in the transmission of electromagnetic waves by the fabric; fromFigure 6 As can be seen from (c), the absorption efficiencies of different MXenes dispersions in this frequency band range can be ranked as: Ti 3 C 2 ≈V 2 C > Mo 2 Ti 2 C 3 > Nb 4 C 3 > Mo 2 TiC 2 > Mo 2 C > Nb 2 C, among which, Ti 3 C 2 and V 2 C dispersions have the best absorption efficiency, and the absorption efficiency reaches 100% in the range of 0.3 - 1.2 THz; therefore, in this embodiment, Ti 3 C 2 dispersion is selected as the immersion liquid.

[0062] Furthermore, in this embodiment, the electromagnetic transmission, reflection, and absorption performances of MXenes microwave-absorbing fabrics and WPU-MXenes microwave-absorbing fabrics in the range of 0.3 - 1.2 THz are compared, as Figure 7 shown; it can be seen from the figure that the introduction of the WPU solution does not reduce the absorption loss ability of the MXenes fabric. On the contrary, the addition of the WPU solution reduces the transmission efficiency in the low-frequency part and increases the absorption loss ability; this is because the surface WPU layer can improve the surface impedance matching of the MXenes microwave-absorbing fabric, enabling more incident electromagnetic waves to enter the fabric and be absorbed by MXenes; at the same time, the surface WPU layer also enhances the interaction between MXenes nanosheets and fabric fibers, generating more interfacial polarization, increasing the conductive loss caused by MXenes nanosheets, so the measured reflection efficiency of the WPU-MXenes microwave-absorbing fabric is lower.

[0063] Microwave-absorbing fabrics with self-cleaning properties have very broad application prospects in daily life and industry. To determine the hydrophobic properties of MXenes microwave-absorbing fabrics and WPU-MXenes microwave-absorbing fabrics, the water contact angle (contact angle, abbreviated as CA) and rolling angle (Sliding Angle, abbreviated as SA) of the two are compared in this embodiment. First, the Laplace-Young method is used to measure the water contact angles of MXenes microwave-absorbing fabrics and WPU-MXenes microwave-absorbing fabrics respectively, as Figure 8As shown in (a) and (b); it can be seen from the figure that the water contact angle CA of the MXenes microwave-absorbing fabric after WPU spraying treatment has increased from the original 140.9° to 151.3°, realizing a microwave-absorbing fabric with superhydrophobic ability; the MXenes surface has rich hydrophilic functional groups, while the WPU solution has superhydrophobicity and low surface energy. By spraying the WPU solution on the surface of the microwave-absorbing fabric to form a hydrophobic protective layer, most of the MXenes nanosheets and WPU are adsorbed on the surface of the flannelette fibers, which can effectively increase the superhydrophobicity of the microwave-absorbing fabric. Then, the rolling angles of the MXenes microwave-absorbing fabric and the WPU-MXenes microwave-absorbing fabric were measured to evaluate the self-cleaning performance of the microwave-absorbing fabric, as Figure 8 shown in (c) and (d); the rolling angle SA refers to the critical angle formed between the inclined surface and the horizontal plane when the liquid droplet just starts to roll on the inclined surface. It can be seen that the measured SA of the MXenes microwave-absorbing fabric is 8°, while the SA of the WPU-MXenes microwave-absorbing fabric reaches 0°. For the surface of the microwave-absorbing fabric sprayed with the WPU solution, it has extremely strong hydrophobic ability.

[0064] The test proves that the liquid dropped on the WPU-MXenes microwave-absorbing fabric can quickly slide out of the fabric surface, showing obvious waterproofness; during this process, it can also take away the impurities on the surface of the microwave-absorbing fabric, meeting the self-cleaning performance of the fabric. Based on this, in this example, the self-cleaning abilities of the MXenes microwave-absorbing fabric and the WPU-MXenes microwave-absorbing fabric were compared and tested, as Figure 9 shown; the same dose of silica powder was sprinkled on the surfaces of the two fabrics. At this time, the silica powder on the MXenes microwave-absorbing fabric adhered firmly to the surface, while the silica powder on the WPU-MXenes microwave-absorbing fabric detached from the fabric surface and had a tendency to roll down; then, the impurities on the surface of the microwave-absorbing fabric were rinsed with an aqueous solution. After the same rinsing time, although most of the silica powder on the MXenes microwave-absorbing fabric was successfully taken away by the aqueous solution, there was still a small amount of silica powder adsorbed on the surface of the microwave-absorbing fabric together with the aqueous solution; on the contrary, after the WPU-MXenes microwave-absorbing fabric was rinsed with the aqueous solution, the silica powder on the surface was quickly rinsed clean, and almost all of the aqueous solution flowed into the petri dish, and the surface of the microwave-absorbing fabric remained dry and comfortable, showing satisfactory self-cleaning performance. Further, to understand in detail the protective effect of WPU on the terahertz wave absorption performance, the terahertz wave absorption performances of the MXenes microwave-absorbing fabric and the WPU-MXenes microwave-absorbing fabric before and after cleaning were compared, as Figure 10As shown; it can be seen from the figure that after the MXenes absorbing fabric is washed, its absorption performance is significantly reduced. This is because the MXenes nanosheets adsorbed on the surface of the suede fibers have hydrophilic properties and will be partially carried away by the aqueous solution without protection, resulting in a reduction in the MXenes nanosheets that play an absorbing role inside the absorbing fabric, and thus the absorption performance becomes weaker. However, due to the protection of the WPU layer, the WPU-MXenes absorbing fabric has superhydrophobic ability on its surface, and the aqueous solution cannot contact the MXenes nanosheets, and the MXenes nanosheets are hardly reduced. Therefore, the terahertz absorption performance of the WPU-MXenes absorbing fabric hardly changes before and after cleaning.

[0065] In practical applications, the chemical stability of the surface of the absorbing fabric is also very important because the fabric will inevitably come into contact with various acid and alkali solutions in life. Therefore, in the present invention, the WPU-MXenes absorbing fabric is immersed in deionized water, sodium chloride, hydrochloric acid (pH = 1) and potassium hydroxide (pH = 14) solutions to simulate a harsh environment to further evaluate the corrosion resistance of the absorbing fabric, as Figure 11 shown; it can be seen from the figure that the water contact angle of the WPU-MXenes absorbing fabric slowly decreases with the increase of the immersion time. Obviously, the WPU layer plays a protective role for the WPU-MXenes absorbing fabric. However, with the prolongation of the immersion time, the stability performance of the WPU-MXenes absorbing fabric gradually decreases to a certain extent, which may be due to the gradual desorption of WPU molecules. Among them, the rate of decrease in the contact angle is the largest in the potassium hydroxide solution. After soaking for 48 hours, the water contact angle decreases from 151.3° to 147.8°, as Figure 11 (a) in shows. The surface resistance of the WPU-MXenes absorbing fabric during the immersion treatment was further tested, as Figure 11 (b) in shows. After soaking in deionized water, sodium chloride, hydrochloric acid (pH = 1) and potassium hydroxide (pH = 14) solutions for 48 hours, the surface resistance of the WPU-MXenes absorbing fabric increased from the initial 20.2 ± 4.2 Ω / square to 21.5 ± 4.5 Ω / square, 22.7 ± 5.2 Ω / square, 24.1 ± 5.5 Ω / square and 24.3 ± 5.6 Ω / square respectively; during the first 24 hours of soaking treatment, the surface resistance of the WPU-MXenes absorbing fabric was relatively stable, but after 24 hours, the surface resistance began to increase rapidly. Similarly, due to the hydrolysis of WPU in an acid-base environment, the protective performance decreases, and the increase in surface resistance will lead to a decrease in conductivity, thereby affecting the absorption attenuation performance of the absorbing fabric. As Figure 11As shown in Fig. (c), the terahertz absorption properties of MXene absorbent fabric and WPU-MXene absorbent fabric were further tested after being immersed in hydrochloric acid (pH = 1) and potassium hydroxide (pH = 14) solutions for 48 hours. As can be seen from the figure, after the MXene absorbent fabric was immersed in hydrochloric acid (pH = 1) and potassium hydroxide (pH = 14) solutions, its terahertz absorption performance decreased significantly. The MXene nanosheets on the fiber surface were easily oxidized by strong acids and alkalis, especially alkaline substances. However, due to the presence of the WPU layer in the WPU-MXene absorbent fabric, the WPU would provide protection for the MXene nanosheets during the immersion process. Therefore, after being immersed in strong acids and alkalis for 48 hours, its terahertz absorption performance still remained above 99%. The results show that by spraying a WPU solution with superhydrophobicity, the MXene nanosheets on the fiber surface can be protected, and the service life of the absorbent fabric can be extended. Moreover, the WPU-MXene absorbent fabric has good self-cleaning performance and shows corrosion resistance for long-term application in various application environments.

[0066] Specifically, in this embodiment, a WPU-MXene absorbent fabric with a size of 80×80 cm was successfully prepared, as Figure 12 shown, which proves the feasibility of large-area preparation of WPU-MXene absorbent fabric. Based on this, the first application of the WPU-MXene absorbent fabric is a terahertz absorbing and shielding fabric. The absorbent fabric with a thickness of 1 mm can achieve more than 99% terahertz absorption. Moreover, using a white fabric as the substrate, placing a graphic mold on the fabric, and spraying the MXene dispersion and the WPU solution on the surface of the pattern mold respectively, WPU-MXene absorbent fabrics with different patterns can be obtained by changing the shape of the mold. As Figure 13 shown in Fig. (a), WPU-MXene absorbent fabrics with cross maple leaf and "UESTC" letter patterns were prepared. Then, a Fico fiber-coupled terahertz time-domain spectroscopy system was used to perform reflection imaging on the above-mentioned patterned WPU-MXene absorbent fabric, as Figure 13 shown in Fig. (b). It can be seen that the terahertz reflection of the patterned WPU-MXene absorbent fabric is extremely low at the cross maple leaf and "UESTC" letters, and the contour of the area loaded with the MXene dispersion is clear, which is significantly different from other areas. This is because most of the terahertz electromagnetic waves are absorbed on the surface of the absorbent fabric after spraying the MXene dispersion and the WPU solution. Based on this, the WPU-MXene absorbent fabric can be applied to wearable applications for pattern absorption and shielding.

[0067] The above are only specific embodiments of the present invention. Any feature disclosed in this specification, unless specifically described, can be replaced by other equivalent or alternative features with similar purposes; all the disclosed features, or all the steps in any method or process, except for mutually exclusive features and / or steps, can be combined in any manner.

Claims

1. A multifunctional terahertz absorbing fabric based on MXenes material, characterized in that: The multifunctional terahertz absorbing fabric is formed by spraying a WPU layer on the surface of a MXenes absorbing fabric, and the MXenes absorbing fabric is formed by soaking the fabric in a MXenes dispersion; The process of spraying the WPU layer on the surface of the MXenes absorbing fabric is as follows: the PU solid content of the WPU emulsion is (10±2)%, and the WPU emulsion is atomized by a spray gun to form droplets, which are then attached to the surface of the MXenes absorbing fabric; the main parameters are: the spray gun caliber is 0.5-1.5mm, the air compressor pressure is 0.2-0.4MPa, the spray distance is 180-220mm, the spray angle is 65-75 degrees, and the spray speed is 5-8m / min; The multifunctional terahertz absorbing fabric has a self-cleaning property, and its water contact angle and rolling angle reach 151.3° and 0° respectively.

2. The multifunctional terahertz absorbing fabric based on MXenes material according to claim 1, characterized in that: MXenes materials use Ti3C2 or V2C.

3. The multifunctional terahertz absorbing fabric based on MXenes material according to claim 1, characterized in that: The surface of the woven fabric has short hairs with a length of 0.4 to 0.8 mm.

4. The method for preparing the multifunctional terahertz absorbing fabric based on MXenes material according to claim 1, characterized in that: The following steps are involved: Step 1, synthesis of MXenes dispersion; MXenes dispersion was synthesized by selectively etching and intercalating MAX phase powders with mixed acid and then centrifugally stirring. Step 2, preparation of MXenes absorbing fabric; The fabric is soaked in MXenes dispersion and dried to obtain MXenes absorbing fabric; Step 3, preparation of WPU-MXenes absorbing fabric; A layer of WPU emulsion is sprayed on the surface of the MXenes absorbing fabric by a spraying process to form a WPU layer, thereby preparing a multifunctional terahertz absorbing fabric based on MXenes material.

5. The method for preparing the multifunctional terahertz absorbing fabric based on MXenes material according to claim 4, characterized in that: In step 1, the mixed acid is a mixed aqueous solution of hydrofluoric acid (HF) and hydrochloric acid (HCI), and the volume ratio of the mixed acid is HCI: HF: H2O = 12: 2.5:

5. A magnetic stirrer is used to stir at a speed of 200-400 rpm, and MAX phase powder is added at the same time. Then, a constant temperature magnetic stirrer is used to centrifugally stir at a speed of 450-800 rpm at 35°C. The setting time is 24 hours to obtain a MXenes dispersion, and its concentration range is 1.0-3.0 mg / ml.

6. The method for preparing the multifunctional terahertz absorbing fabric based on MXenes material according to claim 4, characterized in that: In step 2, the fabric is immersed in a container containing a MXenes dispersion, the liquid level is 3 to 5 mm greater than the thickness of the fabric, and the fabric is taken out and dried to obtain the MXenes absorbing fabric.

7. The method for preparing the multifunctional terahertz absorbing fabric based on MXenes material according to claim 4, characterized in that: In step 3, the PU solid content of the WPU emulsion is (10±2)%, and the WPU emulsion is atomized by a spray gun to form droplets, which are then attached to the surface of the MXenes absorbing fabric; the main parameters are: the spray gun caliber is 0.5-1.5mm, the air compressor pressure is 0.2-0.4MPa, the spraying distance is 180-220mm, the spraying angle is 65-75 degrees, and the spraying speed is 5-8m / min.

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