Sheet-shaped MoS2 and snowflake-shaped VO2 (M) nano-structure electromagnetic wave absorbing material and preparation method thereof

Abstract

The invention discloses a flaky MoS2 and snowflake-shaped VO2 (M) nanostructure electromagnetic wave absorbing material and a preparation method thereof.The preparation method comprises the steps that firstly, electrochemical stripping treatment is conducted on natural molybdenite raw materials, and at least one layer of MoS2 nanosheets is obtained; taking the MoS2 nanosheet as a substrate, and growing a snowflake-shaped VO2 (B) nanostructure on the surface of the MoS2 nanosheet in situ through a hydrothermal synthesis process; and finally, carrying out heat treatment on the obtained precursor to promote the VO2 (B) crystal form to be converted into VO2 (M) so as to prepare the flaky MoS2 and snowflake-shaped VO2 (M) nano composite material. According to the synthesis method, a unique snowflake-shaped hierarchical structure and high-specific-surface-area MoS2 nanosheet synergistic system is constructed, so that the dielectric loss characteristic of the material is remarkably improved, the prepared composite material shows excellent microwave absorption performance, and a new technical path is provided for designing a high-performance electromagnetic wave absorption material.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic wave absorbing materials, and particularly to a flaky MoS2@snowflake-like VO2(M) nanostructured electromagnetic wave absorbing material and a preparation method thereof. Background Art

[0002] In today's era, the rapid development of electronic technology and wireless communication has opened a new era of electromagnetic wave applications. However, the problem of electromagnetic pollution has also followed, and its severity cannot be ignored. Research shows that absorbing materials can convert electromagnetic waves into other forms of energy, thereby effectively reducing electromagnetic wave pollution. In recent years, wave-absorbing materials such as carbon-based materials, magnetic materials, conductive polymers, and metal oxides / sulfides have been widely studied and applied. Vanadium dioxide VO2(M) in the M phase is a binary metal oxide of a strongly correlated electron system. Due to the strong interaction between its internal electrons, orbitals, lattices, and spins, a tiny external stimulus can trigger changes in local electrons and crystal structures, thereby inducing a reversible metal-insulator phase transition in VO2(M). During this phase transition, physical properties such as the crystal structure, resistance, infrared transmittance, and refractive index of VO2(M) change significantly. It is precisely because VO2(M) has a phase transition temperature close to room temperature and significant changes in physical and chemical properties before and after the phase transition that it shows great application potential in many fields such as smart windows, optoelectronic switches, batteries, and supercapacitors. However, the research and application of VO2(M) in the field of electromagnetic wave absorption are relatively few. The main reason is its weak conductivity and low dielectric loss, resulting in poor electromagnetic wave attenuation ability.

[0003] In recent years, as an emerging two-dimensional nanomaterial, molybdenum disulfide has triggered extensive research in the field of electromagnetic wave absorption due to its rich surface defects, high specific surface area, and excellent dielectric loss characteristics. In the application of electromagnetic wave absorption, the strong interaction between MoS2 nanosheets can induce a significant polarization effect, which in turn triggers efficient electromagnetic wave dielectric loss. This property makes it show great application potential in the development of high-performance electromagnetic wave absorbing materials.

[0004] The prior art CN116410697A core-shell structure MoS2@VO2 composite material, preparation method and application disclose a core-shell structure MoS2@VO2 composite material. In its preparation, toxic isopropanol is used as a solvent, and the obtained product has a relatively thick matching thickness of 3 mm and a narrow effective absorption bandwidth, indicating its poor wave absorption performance. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art in using non-environmental protection reagents in the preparation process and low wave absorption performance of the product, the present invention provides a preparation method for a flaky MoS2@snowflake-like VO2(M) nanostructured electromagnetic wave absorbing material.

[0006] The present invention first performs electrochemical exfoliation treatment on natural molybdenite raw materials to obtain few-layer or single-layer flaky MoS2. Research shows that by performing electrochemical exfoliation treatment on natural molybdenite, high-purity 2H-MoS2 nanosheets can be obtained. This treatment process can not only effectively maintain the integrity of the crystal structure of the material, but also significantly increase the specific surface area of the material. Moreover, the intercalation of tetrabutylammonium ions (TBA⁺) into molybdenite increases the interlayer spacing. A larger specific surface area is more conducive to the composite of VO2(M) materials. The increased interlayer spacing creates nanoscale gaps between the originally stacked two-dimensional flaky structures, further enhancing the multiple reflections and scattering of incident waves, providing more contact points for electromagnetic waves, and the dipole polarization loss of MoS2 itself, jointly constituting an important basis for strong dielectric loss. VO2(M) itself has a low dielectric loss and poor microwave absorption performance. Therefore, it needs to be compounded with a high-dielectric material to increase its dielectric loss and further optimize its microwave absorption performance. Comparing with the prior art CN116410697A core-shell structure MoS2@VO2 composite material, preparation method and application, we use safer and harmless deionized water as the solvent, and then use the above-mentioned MoS2 nanosheets as the substrate to in-situ grow snowflake-like VO2(B) nanostructures on its surface through a hydrothermal synthesis process. This is because of the Ostwald ripening effect, which causes small particles of VO2 to redissolve and deposit on large particles of MoS2 in a heterogeneous reaction system. Finally, the obtained precursor is heat-treated to promote the phase transformation of VO2(B) crystal form to VO2(M), thus preparing a flaky MoS2@snowflake-like VO2(M) nanocomposite material. This synthesis method constructs a synergistic system of unique snowflake-like structure VO2(M) and high-specific-surface-area MoS2 nanosheets, significantly improving the dielectric loss characteristics of the material. The prepared composite material exhibits excellent microwave absorption performance, providing a new technical route for the design of high-performance electromagnetic wave absorption materials.

[0007] Based on flaky MoS2 as the substrate, through the synergistic effect of hydrothermal synthesis and heat treatment processes, in-situ grow VO2(M) nanostructures on its surface; finally construct a heterogeneous composite material with snowflake-like VO2(M) nanostructures in-situ loaded on the surface of flaky MoS2. Through unique microstructure design, this composite material exhibits the synergistic advantage of a wide effective absorption band and high electromagnetic wave absorption efficiency under the condition of low matching thickness.

[0008] Another technical problem to be solved by the present invention is to provide the above-mentioned preparation method of two-dimensional nanostructure MoS2@VO2(M) electromagnetic wave absorption material. This method does not require the use of highly toxic organic solvents, has simple process steps, strong controllability, low cost, and can be used for large-scale industrial production.

[0009] The specific technical solution of the present invention is as follows:

[0010] A preparation method of a flaky MoS2@snowflake-like VO2(M) electromagnetic wave absorption material, comprising the following steps:

[0011] Step 1, using an electrochemical method to exfoliate natural molybdenite, and then ultrasonically cleaning with ethanol to obtain 2H-phase two-dimensional flaky MoS2 nanosheets;

[0012] Step 2, first adding V2O5 and H2C2O4 into water, heating and stirring until a dark blue solution is obtained; then adding the two-dimensional flaky MoS2 nanosheets into the dark blue solution, after ultrasonic dispersion treatment, transferring to a reaction kettle for hydrothermal reaction, and using the Ostwald ripening effect to redissolve and deposit the generated VO2 in the reaction system, so as to achieve uniform coating of the B-phase VO2 deposit on the surface of the 2H-phase two-dimensional flaky MoS2 nanosheets;

[0013] After centrifugation and drying, a MoS2@VO2(B) composite material is obtained.

[0014] Step 3, calcining the MoS2@VO2(B) composite material prepared in Step 2 to convert VO2 from the B-phase to the M-phase, obtaining a MoS2@snowflake-like VO2(M) electromagnetic wave absorption material; the VO2 is snowflake-like particles with a particle size of 300-700 nm.

[0015] Preferably, in Step 1, the electrochemical exfoliation specifically includes: using a tetrabutylammonium bromide acetonitrile solution with a concentration of 8 mg / ml for electrochemical exfoliation.

[0016] Preferably, in Step 1, in the electrochemical exfoliation, the DC voltage used is 12V, the platinum electrode is connected to the positive electrode, the molybdenite thin sheet is connected to the negative electrode, and the electrochemical exfoliation time is 8h.

[0017] Preferably, the 2H-phase two-dimensional flaky MoS2 nanosheets in Step 1 include single-layer MoS2 nanosheets and an assembly obtained by overlapping less than 5 single-layer MoS2 nanosheets;

[0018] For the assembly obtained by overlapping less than 5 single-layer MoS2 nanosheets, in Step 2, the B-phase VO2 deposit is deposited on the outer surface of the assembly and not between adjacent single-layer MoS2 nanosheets inside the assembly.

[0019] Preferably, the treatment time of the ethanol ultrasonic cleaning in Step 1 is 20 minutes.

[0020] Preferably, in Step 2, the mass ratio of the dosages of two-dimensional flaky MoS2 nanosheets, V2O5, H2C2O4, and water is (20-60):545.64:810.36:70000;

[0021] Preferably, in step 2, the reaction temperature of the hydrothermal reaction is 200 °C and the reaction time is 12 h.

[0022] Preferably, in step 3, the calcination specifically includes: heating to 500 °C at a heating rate of 5 °C / min in an argon atmosphere and holding for 3 h.

[0023] Preferably, by adjusting the dosage ratio of two-dimensional flaky MoS2 nanosheets, V2O5, H2C2O4, and water in step 2, the applicable electromagnetic wave frequency of the flaky MoS2@snowflake-like VO2(M) electromagnetic wave absorption material is adjusted:

[0024] When the electromagnetic wave frequency is 12.12 GHz, the mass ratio of the dosages of two-dimensional flaky MoS2 nanosheets, V2O5, H2C2O4, and water is 20:545.64:810.36:70000;

[0025] When the electromagnetic wave frequency is 14 GHz, the mass ratio of the dosages of two-dimensional flaky MoS2 nanosheets, V2O5, H2C2O4, and water is 40:545.64:810.36:70000;

[0026] When the electromagnetic wave frequency is 4.92 GHz, the mass ratio of the dosages of two-dimensional flaky MoS2 nanosheets, V2O5, H2C2O4, and water is 60:545.64:810.36:70000.

[0027] The present invention also provides a flaky MoS2@snowflake-like VO2(M) electromagnetic wave absorption material prepared by the preparation method described above.

[0028] Preparation principle of the flaky MoS2@snowflake-like VO2(M) of the present invention: First, the natural molybdenite raw material is subjected to electrochemical exfoliation treatment to obtain monolayer or at least multilayer MoS2 nanosheets; then, using the MoS2 nanosheets as a substrate, snowflake-like VO2(B) nanostructures are in-situ grown on its surface through a hydrothermal synthesis process; finally, the obtained precursor is subjected to heat treatment to promote the phase transformation of VO2(B) crystal form to VO2(M), thereby preparing a flaky MoS2@snowflake-like VO2(M) nanocomposite material. The electromagnetic properties of this electromagnetic wave absorption material can be regulated by the doping ratio of MoS2. Furthermore, more flaky MoS2@snowflake-like VO2(M) composite materials are obtained. The unique structure of MoS2 in this nanomaterial not only constructs a conductive network, significantly improves the electrical conductivity, but also improves multi-polarization relaxation. At the same time, the snowflake-like VO2(M) deposited on MoS2, this unique structure expands the propagation path of electromagnetic waves, enabling the electromagnetic waves to be reflected and scattered multiple times, thereby enhancing the electromagnetic wave absorption effect.

[0029] Advantages of the invention

[0030] (1)Naturally occurring molybdenite exfoliated by an electrochemical method has a large specific surface area and is embedded with tetrabutylammonium ions (TBA⁺), possessing excellent electrical conductivity. The resulting conductance loss, along with the dipole polarization loss of MoS2 itself, jointly constitutes an important basis for strong dielectric loss.

[0031] (2)Compared with the core-shell structure MoS2@VO2 composite material, preparation method and application of the prior art CN116410697A, the flaky MoS2 substrate composite snowflake-like VO2(M) nanoarray structure of the present invention has a larger specific surface area and a richer interface. In the nanoarray structure, the snowflake-like VO2(M) is uniformly distributed on the flaky MoS2 substrate, forming a large number of heterointerfaces, providing more scattering and absorption sites for electromagnetic waves. In contrast, in the MoS2@VO2(M) with a core-shell heterostructure, MoS2 is wrapped outside the VO2(M) core as a shell layer, with relatively fewer interfaces and a smaller specific surface area, which is not conducive to the full absorption of electromagnetic waves. Moreover, in the complex nanoarray structure constructed by the MoS2 substrate and the snowflake-like VO2(M), multiple reflection and scattering phenomena occur when electromagnetic waves propagate therein, greatly extending the propagation path of electromagnetic waves, enabling the energy of electromagnetic waves to be more fully dissipated in this process. Finally, there is an obvious interfacial polarization effect between the MoS2 substrate and VO2(M). This interfacial polarization effect can effectively capture and consume the energy of electromagnetic waves, significantly enhancing the energy attenuation effect on electromagnetic waves.

[0032] (3)Meanwhile, the present invention does not require the use of highly toxic chemical reagents for preparation, has simple method steps, strong controllability, and low cost, and can be used for large-scale industrial production. This important result also provides a strong theoretical basis and experimental foundation for the research and development of ideal microwave absorption materials.

[0033] (4)Compared with the core-shell structure MoS2@VO2 composite material, preparation method and application of the prior art CN116410697A, when the matching thickness is 3 mm, its minimum reflection loss is -56.78 dB, and the optimal effective absorption bandwidth is 4 GHz. For the present invention, when the matching thickness is 1.55 mm and the frequency is 14 GHz, the minimum reflection loss can reach -55.19 dB; when the matching thickness is 1.41 mm, the optimal effective bandwidth is 5.28 GHz. Description of the Drawings

[0034] In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the specific implementation or the prior art description. Some specific embodiments of the present invention will be described in detail in an exemplary but not restrictive manner with reference to the drawings. The same reference numerals in the drawings indicate the same or similar components or parts. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0035] Figure 1 X-ray diffraction patterns of VO2(M), MoS2 and MoS2@VO2(M) prepared in the present invention;

[0036] Figure 2 This is a SEM image of MoS2-20@VO2(M) prepared in Example 1 of the present invention;

[0037] Figure 3 This is a SEM image of MoS2-40@VO2(M) prepared in Example 2 of the present invention;

[0038] Figure 4 This is a SEM image of MoS2-60@VO2(M) prepared in Example 3 of the present invention;

[0039] Figure 5 This is a reflection loss diagram of MoS2-20@VO2(M) prepared in Example 1 of the present invention;

[0040] Figure 6 This is a reflection loss diagram of MoS2-40@VO2(M) prepared in Example 2 of the present invention;

[0041] Figure 7 This is a reflection loss diagram of MoS2-60@VO2(M) prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0043] The embodiments of the present invention are further described below in conjunction with the accompanying drawings.

[0044] The preparation method of the MoS2@VO2(M) absorbing material of the present invention specifically comprises the following steps:

[0045] Example 1

[0046] Step 1, in a two-electrode system, use natural molybdenite flakes and a platinum foil as the cathode and anode respectively. First, dissolve 160 mg of tetrabutylammonium bromide (TBAB) in acetonitrile to prepare an acetonitrile solution with a concentration of 8 mg / mL. Then, apply an electric field to the system using a DC power supply with a voltage of 12 V for 8 hours continuously. Subsequently, place the above-treated molybdenite in absolute ethanol and perform ultrasonic treatment for 20 minutes to achieve complete exfoliation. Finally, put the exfoliated product into a freeze dryer and dry it for 12 hours to finally obtain 2H-MoS2 with a metallic luster.

[0047] Step 2, first, weigh 3 mmol of V2O5 and 9 mmol of H2C2O4, place them in 70 mL of deionized water, and continuously stir until completely dissolved. Then, transfer the mixed solution to an oil bath, set the temperature to 80 °C, and continuously stir for 1 hour until the solution becomes uniformly dark blue. Subsequently, add 20 mg of exfoliated MoS2 to the above solution and perform ultrasonic treatment for 30 minutes to ensure the uniform dispersion of MoS2. After that, transfer the mixed solution to a 100 mL hydrothermal reaction kettle and react at 200 °C for 12 hours. After the reaction, through washing and drying treatments, finally prepare the MoS2-20@VO2(B) composite material.

[0048] Step 3, place the obtained MoS2-20@VO2(B) in an environment protected by an argon atmosphere, heat it at a heating rate of 5 °C / min to 500 °C by programmed heating, and hold the heat treatment at this temperature for 3 hours to finally obtain MoS2-20@VO2(M).

[0049] Example 2

[0050] Step 1, in a two-electrode system, use natural molybdenite flakes and a platinum foil as the cathode and anode respectively. First, dissolve 160 mg of tetrabutylammonium bromide (TBAB) in acetonitrile to prepare an acetonitrile solution with a concentration of 8 mg / mL. Then, apply an electric field to the system using a DC power supply with a voltage of 12 V for 8 hours continuously. Subsequently, place the above-treated molybdenite in absolute ethanol and perform ultrasonic treatment for 20 minutes to achieve complete exfoliation. Finally, put the exfoliated product into a freeze dryer and dry it for 12 hours to finally obtain 2H-MoS2 with a metallic luster.

[0051] Step 2: First, weigh 3 mmol of V2O5 and 9 mmol of H2C2O4, place them in 70 mL of deionized water, and continuously stir until completely dissolved. Then, transfer the mixed solution to an oil bath, set the temperature to 80 °C, and continuously stir for 1 hour until the solution turns into a uniform dark blue. Subsequently, add 40 mg of exfoliated MoS2 to the above solution and ultrasonically treat it for 30 minutes to ensure the uniform dispersion of MoS2. After that, transfer the mixed solution to a 100 mL hydrothermal reactor and react at 200 °C for 12 hours. After the reaction, through washing and drying processes, finally obtain the MoS2-40@VO2(B) composite material.

[0052] Step 3: Place the obtained MoS2-40@VO2(B) in an environment protected by an argon atmosphere, program the temperature to rise at a rate of 5 °C / min to 500 °C, and keep heat-treating at this temperature for 3 hours to finally obtain MoS2-40@VO2(M).

[0053] Example 3

[0054] Step 1: In a two-electrode system, use natural molybdenite flakes and a platinum foil as the cathode and anode respectively. First, dissolve 160 mg of tetrabutylammonium bromide (TBAB) in acetonitrile to prepare an acetonitrile solution with a concentration of 8 mg / mL. Then, apply an electric field to the system using a DC power supply with a voltage of 12 V and continuously act for 8 hours. Subsequently, place the above-treated molybdenite in absolute ethanol and ultrasonically treat it for 20 minutes to achieve complete exfoliation. Finally, put the exfoliated product into a freeze dryer and dry it for 12 hours to finally obtain 2H-MoS2 with a metallic luster.

[0055] Step 2: First, weigh 3 mmol of V2O5 and 9 mmol of H2C2O4, place them in 70 mL of deionized water, and continuously stir until completely dissolved. Then, transfer the mixed solution to an oil bath, set the temperature to 80 °C, and continuously stir for 1 hour until the solution turns into a uniform dark blue. Subsequently, add 60 mg of exfoliated MoS2 to the above solution and ultrasonically treat it for 30 minutes to ensure the uniform dispersion of MoS2. After that, transfer the mixed solution to a 100 mL hydrothermal reactor and react at 200 °C for 12 hours. After the reaction, through washing and drying processes, finally obtain the MoS2-60@VO2(B) composite material.

[0056] Step 3: Place the obtained MoS2-60@VO2(B) in an environment protected by an argon atmosphere, program the temperature to rise at a rate of 5 °C / min to 500 °C, and keep heat-treating at this temperature for 3 hours to finally obtain MoS2-60@VO2(M).

[0057] Figure 1The X-ray diffraction patterns of VO2(M), MoS2, and MoS2@VO2(M) are shown. According to the standard card PDF#37-1492, the characteristic diffraction peaks of MoS2 appear at 14.37°, 39.53°, 44.15°, and 60.14°, corresponding to its (002), (103), (006), and (008) crystal planes. When VO2(M) is grown on the surface of MoS2, the characteristic diffraction peaks presented by the composite material at 26.86°, 27.79°, and 37.08° are in complete agreement with the (-111), (011), and (200) crystal planes of the VO2(M) standard card PDF#43-1051. The overall analysis of the pattern shows that as the content of MoS2 increases, the intensity of the characteristic diffraction peaks of MoS2 increases regularly, which fully proves that the MoS2@VO2(M) composite material has been successfully prepared.

[0058] Figure 2 , 3, and 4 are the SEM images of MoS2-20@VO2(M), MoS2-40@VO2(M), and MoS2-60@VO2(M) respectively. It can be seen from the figure that as the amount of the MoS2 substrate increases, more and more snowflake-like VO2(M) is obtained.

[0059] Figure 5 is the reflection loss diagram of MoS2-20@VO2(M). From Figure 5 it can be seen that MoS2-20@VO2(M) exhibits general microwave absorption performance. The matching thickness is 1.78 mm, and the maximum reflection loss can reach -27.75 dB at a frequency of 12.12 GHz; when the thickness is 1.71 mm, the optimal effective bandwidth is 3.32 GHz.

[0060] Figure 6 is the reflection loss diagram of MoS2-40@VO2(M). From Figure 6 it can be seen that MoS2-40@VO2(M) exhibits excellent microwave absorption performance. The matching thickness is 1.55 mm, and the maximum reflection loss can reach -55.19 dB at a frequency of 14 GHz; when the thickness is 1.41 mm, the optimal effective bandwidth is 5.28 GHz.

[0061] Figure 7 is the reflection loss diagram of MoS2-60@VO2(M). From Figure 7 it can be seen that MoS2-60@VO2(M) exhibits excellent microwave absorption performance. The matching thickness is 3.34 mm, and the maximum reflection loss can reach -55.88 dB at a frequency of 4.92 GHz; when the thickness is 1.33 mm, the optimal effective bandwidth is 5.64 GHz.

[0062] The electromagnetic wave absorption performance of the flaky MoS2@snowflake-like VO2(M) composite material of the present invention mainly stems from the significant increase in both the real and imaginary parts of the complex permittivity of the MoS2@VO2(M) composite material after the introduction of flaky MoS2. At the same time, its dielectric loss tangent angle also increases correspondingly. This phenomenon fully demonstrates that the addition of MoS2 effectively improves the dielectric loss ability of the material. The main reasons for the enhanced dielectric loss ability are as follows: On the one hand, both VO2(M) and MoS2 belong to dielectric loss materials; the combination of the two endows the MoS2@VO2(M) composite material with high intrinsic conductivity, thus generating high conductance loss. On the other hand, the interfacial polarization effect between the MoS2 substrate and VO2(M) further leads to an increase in dielectric loss. Finally, the snowflake-like VO2(M) structure. This unique structure extends the propagation path of electromagnetic waves, enabling multiple reflection and scattering events, thereby improving the absorption efficiency of electromagnetic waves. The existence of multiple loss mechanisms ensures strong absorption of incident electromagnetic waves. Therefore, the present invention can still achieve strong reflection loss and a wide effective absorption bandwidth at a relatively low thickness.

[0063] Both the experimental and theoretical results of the present invention indicate that by means of ion intercalation, natural molybdenite is exfoliated into single-layer and few-layer nanosheets, and then combined with VO2(M), the resulting two-dimensional nanostructured material can exhibit more excellent electromagnetic wave absorption performance.

[0064] As described above, only some specific embodiments of the present invention are provided, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A preparation method of a flaky MoS2@snowflake-like VO2(M) electromagnetic wave absorbing material, characterized in that, It includes the following steps: Step 1: Use the electrochemical method to exfoliate natural molybdenite, and then ultrasonically clean it with ethanol to obtain 2H-phase two-dimensional flaky MoS2 nanosheets; Step 2: First, add V2O5 and H2C2O4 to water, heat and stir until a dark blue solution is obtained; then add the two-dimensional flaky MoS2 nanosheets to the dark blue solution, after ultrasonic dispersion treatment, transfer it to a reaction kettle for hydrothermal reaction, and utilize the Ostwald ripening effect to redissolve and deposit the generated VO2 in the reaction system, so as to achieve uniform coating of the surface of the 2H-phase two-dimensional flaky MoS2 nanosheets by the B-phase VO2 deposit; After centrifugation and drying, a MoS2@VO2(B) composite material is obtained; Step 3: Calcinate the MoS2@VO2(B) composite material prepared in Step 2 to convert VO2 from the B-phase to the M-phase, and obtain a MoS2@snowflake-like VO2(M) electromagnetic wave absorption material; the VO2 is snowflake-like particles with a particle size of 300-700 nm.

2. The preparation method of a flaky MoS2@snowflake-like VO2(M) electromagnetic wave absorption material as described in claim 1, characterized in that In Step 1, the specific electrochemical exfoliation method includes: Electrochemical exfoliation is carried out through a tetrabutylammonium bromide acetonitrile solution with a concentration of 8 mg / ml.

3. The preparation method of a flaky MoS2@snowflake-like VO2(M) electromagnetic wave absorbing material according to claim 2, characterized in that, In Step 1, in the electrochemical exfoliation, the DC voltage used is 12 V, the platinum electrode is connected to the positive electrode, the molybdenite thin sheet is connected to the negative electrode, and the electrochemical exfoliation time is 8 h.

4. The preparation method of a flaky MoS2@snowflake-like VO2(M) electromagnetic wave absorption material as described in claim 1, characterized in that, The 2H-phase two-dimensional flaky MoS2 nanosheets in Step 1 include single-layer MoS2 nanosheets and aggregates obtained by overlapping less than 5 single-layer MoS2 nanosheets; For the aggregates obtained by overlapping less than 5 single-layer MoS2 nanosheets, in Step 2, the B-phase VO2 deposit is deposited on the outer surface of the aggregate and not deposited between adjacent single-layer MoS2 nanosheets inside the aggregate.

5. The preparation method of a flaky MoS2@snowflake-like VO2(M) electromagnetic wave absorption material as described in claim 1, characterized in that, The treatment time of the ethanol ultrasonic cleaning in Step 1 is 20 minutes.

6. The preparation method of a flaky MoS2@snowflake-like VO2(M) electromagnetic wave absorption material as described in claim 1, characterized in that, In Step 2, the mass ratio of the dosages of two-dimensional flaky MoS2 nanosheets, V2O5, H2C2O4, and water is (20-60):545.64:810.36:70000.

7. The preparation method of a flaky MoS2@snowflake-like VO2(M) electromagnetic wave absorption material according to claim 6, characterized in that In Step 2, the reaction temperature of the hydrothermal reaction is 200 °C and the reaction time is 12 h.

8. The preparation method of a flaky MoS2@snowflake-like VO2(M) electromagnetic wave absorption material according to claim 1, characterized in that, In Step 3, the specific calcination includes: In an argon atmosphere, heat up to 500 °C at a heating rate of 5 °C / min and keep it warm for 3 h.

9. The preparation method of a flaky MoS2@snowflake-like VO2(M) electromagnetic wave absorption material according to claim 6, characterized in that, By adjusting the dosage ratio of two-dimensional flaky MoS2 nanosheets, V2O5, H2C2O4, and water in Step 2, the applicable electromagnetic wave frequency of the flaky MoS2@snowflake-like VO2(M) electromagnetic wave absorption material is adjusted: When the electromagnetic wave frequency is 12.12 GHz, the mass ratio of the dosages of two-dimensional flaky MoS2 nanosheets, V2O5, H2C2O4, and water is 20:545.64:810.36:70000; When the electromagnetic wave frequency is 14 GHz, the mass ratio of the dosages of two-dimensional flaky MoS2 nanosheets, V2O5, H2C2O4, and water is 40:545.64:810.36:70000; The electromagnetic wave frequency is 4.92 GHz, and the mass ratio of the dosages of two-dimensional flaky MoS2 nanosheets, V2O5, H2C2O4, and water is 60:545.64:810.36:70000.

10. A flaky MoS2@snowflake-like VO2(M) electromagnetic wave absorption material prepared by the preparation method according to any one of claims 1 to 9.

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