Flower-shaped electromagnetic wave-absorbing material and preparation method thereof

Abstract

The invention discloses a flower-shaped electromagnetic wave-absorbing material and a preparation method thereof. The material comprises polypyrrole and V2O5, v2O5 is of a sheet structure; polypyrrole grows along the direction of the V2O5 nanosheet layer to form a two-dimensional plane; the two-dimensional nanosheets grow dispersedly by taking the crystal nucleus as the center to generate flower-shaped morphology; the polypyrrole / V2O5 composite wave-absorbing material with a flower-like structure is prepared through a hydrothermal reaction; the problems that in the prior art, V2O5 is poor in EMW absorption dielectric property, low in dielectric loss and the like are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave absorbing materials, and particularly relates to a flower-shaped electromagnetic wave absorbing material and a preparation method thereof. Background Art

[0002] With the rapid development of wireless communication technology, especially the advent of the 5G era, high-frequency intelligent electromagnetic devices represented by the gigahertz (GHz) frequency have provided us with a convenient and intelligent life due to their great advantages in long-distance, wireless, and high-speed response, and are becoming increasingly popular among people. However, this comes at the cost of a significant increase in electromagnetic interference and pollution. Microwave absorbing (MA) materials that can absorb incident electromagnetic waves (EMW) are of great significance in solving electromagnetic pollution and have therefore received extensive attention. An ideal electromagnetic wave absorbing material should meet the following requirements: a wide effective absorption bandwidth, strong reflection loss, a thin thickness, and a light weight.

[0003] Currently, researchers have made a great deal of efforts to meet these requirements of microwave absorbing materials. Transition metal oxides (TMOs), such as Fe2O3, Co3O4, CoO, NiO, and TiO2, are considered to be the most promising electromagnetic wave absorbers because of their large specific surface area, excellent chemical stability, and rich heterointerfaces, which can induce interfacial polarization to enhance electromagnetic wave loss. As one of the transition metal oxides, V2O5 has attracted great interest due to its layered structure, excellent chemical stability, rich resources, and low price, and has been widely used in the fields of optics, electricity, electrochemistry, etc. in recent years. However, there are few reports on the absorption of EMW by V2O5, because V2O5 has poor dielectric properties and low dielectric loss. Therefore, finding a feasible strategy to improve the dielectric properties of V2O5 and enhance its dielectric loss has become an urgent task. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a flower-shaped electromagnetic wave absorbing material and a preparation method thereof to solve the problems of poor dielectric properties and low dielectric loss of V2O5 for EMW absorption in the prior art.

[0005] The technical solution of the present invention is as follows:

[0006] A flower-shaped electromagnetic wave absorbing material, the material comprising polypyrrole and V2O5; V2O5 has a flaky structure; polypyrrole grows along the direction of the V2O5 nanosheet layer to form a two-dimensional plane; the two-dimensional nanosheets are dispersed and grown with the crystal nucleus as the center to produce a flower-shaped morphology.

[0007] A preparation method of a flower-shaped electromagnetic wave absorbing material, comprising:

[0008] Step 1: Add 0.117 g of NH4VO3, 21 mL of deionized water, and 5 μL of pyrrole solution into a beaker, and mix and stir for 15 minutes;

[0009] Step 2: Add 1 mol / L hydrochloric acid during stirring. When the pH value of the solution is adjusted to 1, continue stirring for 15 minutes.

[0010] Step 3: Transfer the stirred solution to an 80 mL Teflon-lined stainless steel autoclave for hydrothermal reaction.

[0011] Step 4: The material after hydrothermal reaction is centrifuged by a centrifuge to collect the polypyrrole-V2O5 composite material, and then washed with absolute ethanol and deionized water.

[0012] Step 5: Freeze the washed polypyrrole-V2O5 composite material at -20 °C for 12 hours, and then freeze-dry it by a freeze dryer for 1 day to obtain the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material.

[0013] The purity of the pyrrole solution is above 99%.

[0014] The hydrothermal reaction is carried out at 120 °C for 24 hours.

[0015] For the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material within the test frequency range of 2 - 18 GHz, the real part of the dielectric constant of the flower-shaped absorbing material is 6.86 - 11.59, and the imaginary part is between 2.20 - 2.58.

[0016] Advantages of the present invention:

[0017] The flower-shaped electromagnetic wave absorbing material of the present invention has a unique microstructure and flower-shaped morphology, and the preparation process is simple, which can be mass-produced.

[0018] The flower-shaped electromagnetic wave absorbing material of the present invention not only has a thin thickness and light weight, but also has a wide frequency band and strong reflection loss. The strongest loss frequency point can attenuate more than 99.99% of the electromagnetic wave.

[0019] The flower-shaped electromagnetic wave absorbing material of the present invention improves the disadvantages of poor dielectric properties, low dielectric loss and poor absorption of V2O5, enhances the wave absorption performance of V2O5. When the matching thickness is 1.9 mm, the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material obtains an effective absorption bandwidth (EAB) of 5.44 GHz. When it is 2.0 mm, the strongest reflection loss (RL min ) is -42.50.

[0020] Within the range of 2 - 18 GHz, the real part of the dielectric constant of the flower-shaped electromagnetic wave absorbing material of the present invention remains at 6.86 - 11.59, and the imaginary part remains at 2.20 - 2.58. It not only has excellent dielectric properties, but also has good impedance matching. At the same time, the dielectric loss tangent is 0.22 - 0.4 within the test frequency band, and it has excellent dielectric loss performance.

[0021] It solves the problems of poor dielectric properties and low dielectric loss of EMW absorption of V2O5 in the prior art. Description of the Drawings

[0022] Figure 1 In Figure a, it is the SEM image of pure V2O5. In Figure b, it is the SEM image of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in Example 1. In Figure c, it is the Mapping image of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in Example 1;

[0023] Figure 2 It is the TEM image of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in Example 1;

[0024] Figure 3 It is the XRD image of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in Example 1;

[0025] Figure 4 It is the dielectric constant image of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in Example 1;

[0026] Figure 5 It is the reflection loss image of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in Example 1;

[0027] Figure 6 It is the dielectric loss image of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in Example 1;

[0028] Figure 7 It is the dielectric constant image of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in Comparative Example 1;

[0029] Figure 8 It is the reflection loss image of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in Comparative Example 1;

[0030] Figure 9 It is the dielectric loss image of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in Comparative Example 1;

[0031] Figure 10 It is the dielectric constant image of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in Comparative Example 2;

[0032] Figure 11 It is the reflection loss image of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in Comparative Example 2;

[0033] Figure 12 It is the dielectric loss image of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in Comparative Example 2;

[0034] Figure 13 Attenuation constant diagrams of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing materials prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0035] Figure 14 Impedance matching diagrams of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing materials prepared in Example 1, Comparative Example 1, and Comparative Example 2. Specific implementation manners

[0036] The main characteristics of the flower-shaped electromagnetic wave absorbing material prepared by the present invention include:

[0037] (1) A flower-shaped polypyrrole / V2O5 composite wave absorbing material was prepared by a hydrothermal reaction;

[0038] (2) By adjusting the addition amount of pyrrole, the dielectric properties of the composite material were enhanced and the impedance matching was optimized;

[0039] (3) The addition of pyrrole enhanced the dielectric properties and dielectric loss of V2O5 and optimized its electromagnetic wave absorption performance;

[0040] (4) The nano-petals of the composite material have a strong scattering effect on the incident electromagnetic waves, which helps to create multiple scattering paths for the attenuation of the electromagnetic waves;

[0041] (5) The polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material has a simple preparation process and can be mass-produced;

[0042] (6) The polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material has excellent impedance matching performance and strong electromagnetic wave attenuation performance, making it have excellent wave absorption performance.

[0043] Example 1:

[0044] A flower-shaped electromagnetic wave absorbing material was prepared in this example. The electromagnetic wave absorbing material is composed of polypyrrole and V2O5. Among them, V2O5 has a flaky structure, and the growth of polypyrrole is restricted by the V2O5 nanosheets, so that the polypyrrole layer can only grow along the direction of the V2O5 nanosheet layer, resulting in the formation of only a two-dimensional plane. Finally, the two-dimensional nanosheets grow dispersedly with the crystal nucleus as the center, generating a flower-shaped morphology.

[0045] The preparation method of the material includes:

[0046] Step 1. Preparation of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material.

[0047] Step 1.1. Add 0.117 g of NH4VO3, 21 mL of deionized water, and 5 μL of pyrrole solution into a beaker, mix and stir for 15 minutes to fully mix different reactants. The purity of pyrrole is above 99%;

[0048] Step 1.2: During the stirring process in Step 1.1, add 1 mol / L hydrochloric acid. When the pH value of the solution is adjusted to 1, continue stirring for 15 minutes to create an acidic environment for the synthesis of the polypyrrole-V2O5 composite material.

[0049] Step 1.3: Transfer the solution from Step 1.2 to an 80 mL Teflon-lined stainless steel autoclave and carry out a hydrothermal reaction at 120 °C for 24 hours. The purpose of carrying out the hydrothermal reaction at 120 °C for 24 hours is to obtain a flower-like polypyrrole-V2O5 composite material.

[0050] Step 1.4: Collect the product by centrifugation using a centrifuge, and then wash the product several times with absolute ethanol and deionized water. Collect the polypyrrole-V2O5 composite material by centrifugation, and then remove the excess impurities through washing with absolute ethanol and deionized water.

[0051] Step 1.5: Freeze the product at -20 °C for 12 hours, and then freeze-dry it for 1 day using a freeze dryer to remove the excess moisture, obtaining the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material.

[0052] Figure 1 Figure a of this shows the SEM image of V2O5 without added polypyrrole prepared according to this example. It can be seen that the morphology of pure V2O5 is a nanoribbon structure, which is due to the fact that orthorhombic V2O5 tends to grow along the (00l) crystal plane. Figure b is the SEM image of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in this example. It can be seen that after adding polypyrrole, the morphology of the polypyrrole-V2O5 composite material has changed significantly, showing a uniform flower cluster-like morphology. Figure c is the Mapping image of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in this example. It can be seen that the wave-absorbing material is composed of C, O, N, and V elements.

[0053] Figure 2 This is the TEM image of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in this example. It can be seen that the petals of the flower-shaped morphology of the wave-absorbing material have typical two-dimensional structural characteristics of layer-by-layer intercalation.

[0054] Figure 3 This is the XRD pattern of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in this example. It can be seen that the diffraction peaks of the XRD pattern of pure V2O5 near 2θ = 15°, 20°, 26°, and 31° correspond to the (200), (001), (110), and (301) crystal planes respectively, and the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in this example also shows these crystal planes, proving the successful composite of polypyrrole and V2O5. In addition, the diffraction pattern of the wave-absorbing material contains low-angle peaks, indicating that it is composed of bilayer V2O5.

[0055] Figure 4 Dielectric constant diagram of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in this example (loading amount of the absorbing material is 40%). It can be seen that in the test frequency range of 2 - 18 GHz, the real part of the dielectric constant of the flower-shaped absorbing material is 6.86 - 11.59, and the imaginary part remains at 2.20 - 2.58, indicating that the composite material has strong dielectric properties and can effectively absorb incident electromagnetic waves and dissipate electromagnetic waves through multiple loss methods such as multiple reflection and scattering loss, and interfacial polarization.

[0056] Figure 5 Reflection loss diagram of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in this example. It can be seen that due to the strong dielectric properties of the absorbing material, an RL of -42.50 dB min (with a matching thickness of 2.0 mm) and an EAB of 5.44 GHz (range from 12.56 to 18 GHz) (with a matching thickness of 1.9 mm) are obtained, almost covering the entire Ku band.

[0057] Figure 6 Dielectric loss tangent diagram of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in this example. It can be seen that the dielectric loss tangent of the absorbing material remains at 0.22 - 0.4 in the test frequency band range, having strong dielectric loss performance and being able to effectively dissipate incident electromagnetic waves.

[0058] Comparative example 1:

[0059] The difference from Example 1 is that the addition amount of pyrrole is 0 μL.

[0060] Figure 7 Dielectric constant diagram of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in this comparative example (loading amount of the absorbing material is 40%). It can be seen that the real part of the dielectric constant of the absorbing material prepared in this comparative example is about 3.5 in the entire frequency band range, and the imaginary part is about 0. The electromagnetic energy storage and dissipation ability is not ideal, which is due to the poor dielectric properties of vanadium oxide.

[0061] Figure 8 Reflection loss diagram of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in this comparative example. It can be seen that the RL min value of pure V2O5 is almost 0 in all bands, indicating that it is a microwave transparent material with extremely poor ability to absorb electromagnetic waves, and its wave absorption performance is much smaller than that of the absorbing material in Example 1.

[0062] Figure 9This is the dielectric loss tangent graph of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in this comparative example. It can be seen that the dielectric loss tangent value of the absorbing material is very small, indicating that its dielectric loss ability is very poor, corresponding to its wave absorption performance.

[0063] Comparative Example 2:

[0064] The difference from Example 1 is that the addition amount of pyrrole is 30 μL.

[0065] Figure 10 This is the dielectric constant graph of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in this comparative example (the loading amount of the absorbing material is 40%). It can be seen that the real part of the dielectric constant of the absorbing material prepared in this comparative example is in the range of 5-7, and the imaginary part is about 1.5, which is lower than the dielectric performance of the absorbing material in Example 1, which is related to the reduction of interfacial polarization.

[0066] Figure 11 This is the reflection loss graph of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in this comparative example. It can be seen that due to the weakening of the interfacial polarization effect and dielectric performance, the absorption performance of the sample prepared in this comparative example is also lower than that of the sample prepared in Example 1. The strongest reflection loss of the sample prepared in this comparative example is only -11.85 dB (the thickness is 2.0 mm), and the effective absorption bandwidth is 1.44 GHz (the thickness is 2.1 mm).

[0067] Figure 12 This is the dielectric loss tangent graph of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing material prepared in this comparative example. It can be seen that the increase in the addition amount of pyrrole makes the dielectric loss tangent value of the absorbing material in this comparative example lower than that in Example 1, which is the same as the change trend of the wave absorption performance.

[0068] Figure 13 This is the attenuation constant graph of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing materials prepared in Example 1, Comparative Example 1 and Comparative Example 2. It can be seen that as the addition amount of pyrrole increases, the attenuation constant value of the absorbing material first increases and then decreases, and the absorbing material prepared in Example 1 has the strongest electromagnetic wave attenuation performance.

[0069] Figure 14 This is the impedance matching graph of the polypyrrole / V2O5 flower-shaped electromagnetic wave absorbing materials prepared in Example 1, Comparative Example 1 and Comparative Example 2. It can be seen that the impedance matching of the absorbing material prepared in Example 1 is closest to 1, indicating that its impedance matching is the best and it can absorb more electromagnetic waves into the material. Combining its excellent electromagnetic wave attenuation performance, it obtains the best wave absorption performance.

Claims

1. A flower-shaped electromagnetic wave absorbing material, characterized in that: The materials include polypyrrole and V2O5; V2O5 has a flaky structure; polypyrrole grows along the direction of the V2O5 nanosheet layer to form a two-dimensional plane; the two-dimensional nanosheets are dispersed and grown with the crystal nucleus as the center to produce a flower-like morphology.

2. The preparation method of a flower-shaped electromagnetic wave absorbing material according to claim 1, characterized in that: The method includes: Step 1: Add 0.117 g of NH4VO3, 21 mL of deionized water, and 5 μL of pyrrole solution into a beaker, and mix and stir for 15 minutes; Step 2: Add 1 mol / L hydrochloric acid during the stirring process. When the pH value of the solution is adjusted to 1, continue to stir for 15 minutes; Step 3: Transfer the stirred solution to an 80 mL Teflon-lined stainless steel autoclave for hydrothermal reaction; Step 4: The material after the hydrothermal reaction is centrifuged by a centrifuge to collect the pyrrole-V2O5 composite material, and then washed with absolute ethanol and deionized water; Step 5: Freeze the washed pyrrole-V2O5 composite material at minus 20 degrees Celsius for 12 hours, and then freeze-dry it with a freeze dryer for 1 day to obtain the polypyrrole / V2O5 flower-like electromagnetic wave absorbing material.

3. The preparation method of a flower-shaped electromagnetic wave absorbing material according to claim 2, characterized in that: The purity of the pyrrole solution is above 99%.

4. The preparation method of a flower-shaped electromagnetic wave absorbing material according to claim 2, characterized in that: The hydrothermal reaction is carried out at 120 °C for 24 hours.

5. The preparation method of a flower-shaped electromagnetic wave absorbing material according to claim 2, characterized in that: For the polypyrrole / V2O5 flower-like electromagnetic wave absorbing material within the test frequency range of 2 - 18 GHz, the real part of the dielectric constant of the flower-like wave absorbing material is 6.86 - 11.59, and the imaginary part is between 2.20 - 2.58.

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