Modified carbon fiber as well as preparation method and application thereof

Abstract

The invention discloses a modified carbon fiber and a preparation method and application thereof, relates to the technical field of electromagnetic shielding materials, and solves the problems that an existing electromagnetic wave absorbing material is relatively weak in absorbing strength and relatively narrow in absorbing frequency band. The preparation method comprises the following steps: dissolving SnCl4. 5H2O in deionized water, and fully dissolving and stirring to obtain a solution A; carrying out hydrothermal reaction on desized carbon fiber cloth in the solution A, washing and drying to obtain SnO2 / CF; the preparation method comprises the following steps: dissolving FeCl3. 6H2O, FeCl2. 4H2O and alkali in deionized water, and fully dissolving to obtain a solution B; and adding the SnO2 / CF into the solution B, and stirring at 80 DEG C in an N2 atmosphere to obtain Fe3O4 / SnO2 / CF. The preparation method is suitable for industrial production and application, the comprehensive performance of the material can be obviously improved, a new way is opened up for a high-performance light-weight shielding technology, and a brand new choice is provided.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic shielding materials, and particularly relates to a modified carbon fiber and its preparation method and application. Background Art

[0002] With the continuous progress of modern electromagnetic technology and communication technology, the application of electromagnetic waves has become more and more extensive, which has brought great changes to modern lifestyles. However, the accompanying problem is electromagnetic wave pollution. Electromagnetic wave radiation can cause great harm to human health. Research shows that electromagnetic wave pollution can lead to a decline in the body's immune ability and have an adverse impact on people's health. At the same time, electromagnetic wave pollution will affect the operation of precision equipment, thus reducing the accuracy and lifespan of precision equipment. Therefore, it is of great significance to study electromagnetic shielding materials with high performance.

[0003] In recent years, lightweight flexible carbon-based materials have the advantages of excellent corrosion resistance, wearability, functionality, processability, etc., and have been widely used in the fields of electronic equipment such as personal electromagnetic protection, intelligent flexible materials, and communication equipment protection.

[0004] Nanoscale iron oxide particles (Fe3O4 nanoparticles) show great potential for application in the field of electromagnetic shielding due to their unique physical and chemical properties. The small size effect, optical properties, and magnetic properties of these particles enable them to significantly increase energy loss during the conversion of electromagnetic wave energy such as light absorption and light reflection. At the same time, nanoscale iron oxide particles also have a relatively high magnetic loss tangent (tanδ), which can effectively convert the energy of electromagnetic waves into heat energy to achieve the absorption and attenuation of electromagnetic waves. However, when a single introduction of nanoparticles is used as an electromagnetic wave absorption material, there are problems such as weak absorption intensity and narrow absorption bandwidth, thus limiting its application in the field of electromagnetic wave shielding.

[0005] SnO2, as an n-type direct wide-band semiconductor, has shown broad application prospects in lithium-ion batteries, perovskite solar cells, gas sensors, photocatalysts, etc. in the past decade. In addition, SnO2 can also be studied as an electromagnetic shielding and wave-absorbing material due to its advantages such as easy preparation, light weight, good chemical and thermal stability, low dielectric loss, and strong microwave absorption ability. However, when SnO2 is used alone as an electromagnetic wave absorption material, the same problems exist. On the one hand, its absorption intensity is relatively limited, and it is difficult to provide sufficient shielding effectiveness in the face of high-intensity electromagnetic interference sources. On the other hand, its absorption bandwidth is relatively narrow, and it can only effectively absorb electromagnetic waves in a specific frequency band and cannot adapt to complex and changing electromagnetic environments, which greatly limits its wide application in practical scenarios.

[0006] Therefore, how to overcome these limitations and develop high-performance, wide-band electromagnetic wave absorbing materials to improve the performance of materials in the field of electromagnetic shielding has become an important issue that needs to be urgently addressed in the current field of materials science. Summary of the invention

[0007] In order to solve the problem that the existing electromagnetic wave absorbing materials have weak absorption intensity and narrow absorption frequency band, the present invention proposes a modified carbon fiber and a preparation method and application thereof.

[0008] The technical solution of the present invention is as follows:

[0009] A method for preparing modified carbon fiber comprises the following steps:

[0010] S1. Dissolve SnCl4.5H2O in deionized water, and stir to obtain solution A;

[0011] S2, subjecting the desized carbon fiber cloth to a hydrothermal reaction in the solution A, washing and drying, to obtain SnO2 / CF;

[0012] S3, dissolving FeCl3.6H2O, FeCl2.4H2O and alkali in deionized water, and obtaining solution B after fully dissolving;

[0013] S4. Add the SnO2 / CF into the solution B and stir at 80°C under N2 atmosphere to obtain Fe3O4 / SnO2 / CF.

[0014] Preferably, in step S1, the ratio of the mass of SnCl4.5H2O to the volume of the solvent in the solution A is (0.01-20) g:100 mL.

[0015] Preferably, the stirring time in step S1 is 0.5 h to 24 h.

[0016] Preferably, the desizing carbon fiber cloth is obtained by washing the carbon fiber cloth by condensation reflux, using condensed water as a condensation reflux agent and 80° C. acetone as a solvent and a cleaning agent.

[0017] Preferably, the carbon fiber cloth is selected to include but not limited to fabrics such as carbon felt made of chopped carbon fiber, carbon fiber cloth obtained from different tow carbon fibers (from 1k to 48k) and different weaving methods, including plain weave, twill, satin and other fabrics, and is also suitable for activated carbon fiber felt, carbon nanofiber felt, and electrospun carbon fiber products.

[0018] More preferably, the carbon fiber cloth is one or a mixture of at least two of 1K / 3K carbon fiber plain / twill fabric, electrospun carbon fiber, and carbon fiber needle felt.

[0019] Preferably, the hydrothermal reaction in step S2 is carried out for 0.5 h to 15 h at a reaction temperature of 100 °C to 150 °C.

[0020] Preferably, the base in step S3 is sodium hydroxide.

[0021] Preferably, the molar ratio of FeCl3·6H2O, FeCl2·4H2O to sodium hydroxide is 0.5 - 2:0.1 - 5:0.01 - 5.

[0022] The present invention also provides a modified carbon fiber prepared by the above preparation method.

[0023] The present invention also provides an application of the above modified carbon fiber in the field of electromagnetic shielding.

[0024] Compared with the prior art, the specific beneficial effects of the present invention are as follows:

[0025] The present invention realizes the extended application of nano-tin dioxide (SnO2) and nano-ferroferric oxide (Fe3O4) in the field of electromagnetic shielding through innovative technologies. As a carbon material, carbon fiber itself has excellent conductivity, laying a good conductive foundation for the composite material. The present invention adopts a unique surface modification strategy and uses a multi-level structure interface layer constructed by nano-SnO2 dielectric loss particles and nano-ferroferric oxide magnetic loss particles to treat the carbon fiber. The nano-SnO2 and SnO2 / Fe3O4 interfaces can play a dielectric loss role, while nano-ferroferric oxide has a significant magnetic loss function. The synergistic effect of these three promotes the formation of an efficient electromagnetic loss system, thereby obtaining a composite material with excellent electromagnetic shielding performance.

[0026] Verified by tests, in the key frequency range of 8 - 12 GHz, the electromagnetic shielding effectiveness of the composite material provided by the present invention can reach up to 60 dB at most. Compared with the original carbon fiber (CF), a significant performance improvement is achieved. This remarkable performance advantage makes the composite material have extremely high application value in the field of electromagnetic shielding.

[0027] The preparation method provided by the present invention uses a hydrothermal method to introduce composite nanoparticles, successfully constructs a Fe3O4 / SnO2 multi-level structure on the surface of the carbon cloth, and further forms a multi-level loss mechanism structure on the carbon fiber, effectively enhancing the electromagnetic shielding performance. This preparation method is not only simple and reasonable, but also suitable for industrial production applications, can significantly improve the comprehensive performance of the material, opens up a new path for high-performance lightweight shielding technology, and provides a new choice. Description of the Drawings

[0028] Figure 1 It is the SEM image of CF in Example 1;

[0029] Figure 2 SEM image of SnO2 / CF in Example 1;

[0030] Figure 3 SEM image of Fe3O4 / SnO2 / CF in Example 1;

[0031] Figure 4 Absorption loss curves of shielding effectiveness of CF and Fe3O4 / SnO2 / CF in Example 1;

[0032] Figure 5 Reflection loss curves of shielding effectiveness of CF and Fe3O4 / SnO2 / CF in Example 1;

[0033] Figure 6 Total shielding effectiveness curves of CF and Fe3O4 / SnO2 / CF in Example 1. Detailed implementation manners

[0034] To make the technical solutions of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention. It should be noted that the following embodiments are only used to better understand the technical solutions of the present invention and should not be construed as a limitation of the present invention.

[0035] Example 1.

[0036] The preparation method of the Fe3O4 / SnO2 multi - structure modified carbon fiber electromagnetic shielding composite material of the present invention includes the following steps:

[0037] (1) Using a Soxhlet extractor, through the way of condensation reflux, using condensed water as the condensation reflux agent and acetone as the solvent and cleaning agent for carbon fiber, heating the acetone solution to 80 °C, cleaning the carbon fiber cloth (a mixed cloth of 1K / 3K carbon fiber plain / twill fabric, electrospun carbon fiber, and carbon fiber needle felt) for 48 h to thoroughly remove the sizing agent on the surface of the original fiber. The obtained desized carbon fiber cloth sample is denoted as CF.

[0038] (2) Dissolve 7 g of SnCl4·5H2O in 50 mL of deionized water, stir at room temperature for 12 h to form a colorless transparent colloidal solution. Transfer the mixed solution and the carbon fiber cloth to a 100 ml Teflon - lined stainless - steel autoclave, heat at 150 °C for 12 h. After cooling to room temperature, wash with deionized water and dry at 50 °C. The obtained sample is denoted as SnO2 / CF.

[0039] (3) Add SnO2 / CF to an aqueous solution containing FeCl3·6H2O, FeCl2·4H2O and NaOH, and mechanically stir for 2 h under a N2 atmosphere at 80 °C. Fe3O4 nanoparticles are in-situ adhered to the fiber surface through a coordination reaction. The obtained sample is denoted as Fe3O4 / SnO2 / CF.

[0040] Example 2.

[0041] Omit step (3) in Example 1, and other parameters are the same as those in Example 1.

[0042] Example 3.

[0043] Omit step (2) in Example 1, and other parameters are the same as those in Example 1.

[0044] The carbon fiber cloth CF after removing the sizing agent in step (1) of Example 1, the SnO2 / CF prepared in step (2), and the Fe3O4 / SnO2 / CF prepared in step (3) were observed by scanning electron microscopy, and the obtained SEM images are respectively as Figures 1 to 3 shown.

[0045] As can be seen from Figure 1 , the surface of the carbon fiber cloth CF after removing the sizing agent is relatively smooth, the fiber thickness is uniform, showing a typical carbon fiber morphology. The fibers are arranged tightly and orderly, and the overall fiber structure is complete without obvious damage or defects, providing a good basis for subsequent particle loading. In Figure 2 , compared with the original CF, the morphology of the SnO2 / CF sample shows obvious changes. SnO2 particles are successfully loaded on the carbon fiber surface, and the particle distribution is relatively uniform, changing the originally smooth surface morphology of the carbon fiber and increasing the specific surface area of the material. This will be beneficial to enhancing the dielectric loss effect and further improving the electromagnetic shielding performance. The scanning electron microscope image of Fe3O4 / SnO2 / CF shows ( Figure 3 ), a more complex hierarchical nanostructure is formed on the carbon fiber surface. Fe3O4 particles and SnO2 particles are co-loaded on the carbon fiber. The Fe3O4 particles show a unique morphology and are intertwined with the SnO2 particles, forming a more compact composite structure. The particles are more evenly distributed on the carbon fiber surface. The construction of this hierarchical structure can effectively promote the synergistic effect of magnetic loss and dielectric loss, further enhancing the electromagnetic shielding performance of the material.

[0046] The carbon fiber cloth CF after removing the sizing agent in Example 1 and Fe3O4 / SnO2 / CF in Example 1 were tested by the waveguide method for vector network analysis. The size of the test sample was 22.90 mm × 10.20 mm × 1.80 mm, and the measurement range was the X-band (8.2 GHz to 12.4 GHz). The S-parameters of the materials were obtained. Through the S-parameters, the electromagnetic shielding effectiveness SE value could be calculated to quantify the electromagnetic shielding performance of the materials, and the absorption loss curve SE A and the reflection loss curve SE R as well as the total shielding effectiveness curve SE results are respectively shown in Figures 4 to 6 as follows.

[0047] From Figure 4 the absorption spectrum data, it can be seen that due to the lack of effective absorption media in CF itself, its ability to absorb electromagnetic waves is limited, and the single surface characteristics lead to limited reflection ability. Relying on the synergistic effect of the magnetic loss of Fe3O4 and the dielectric loss of SnO2, Fe3O4 / SnO2 / CF significantly enhances its ability to absorb electromagnetic waves throughout the frequency band, which is closely related to its complex micro multi-level structure, providing more paths for the absorption of electromagnetic waves. In addition, from Figure 5 it can be seen that the complex multi-level structure of Fe3O4 / SnO2 / CF also changes the reflection of electromagnetic waves. The multiple reflections and scattering of electromagnetic waves by the multi-level structure effectively change the reflection loss situation. From Figure 6 it can be seen that the total shielding effectiveness of CF is relatively low, and it is difficult to efficiently shield electromagnetic waves only relying on its own conductivity. While the total shielding effectiveness of Fe3O4 / SnO2 / CF is significantly improved. This is due to the synergistic effect of its multi-level interface structure, absorption loss and reflection loss, enabling Fe3O4 / SnO2 / CF to exhibit good shielding effects when facing electromagnetic waves of different frequencies, further confirming its advantages in the field of electromagnetic shielding.

[0048] The electromagnetic shielding performance of the composite materials prepared in Examples 1-3 and the desized carbon fiber cloth CF was tested respectively. The total electromagnetic shielding effectiveness results obtained from the test are shown in Table 1.

[0049] Table 1

[0050] Example 1 Example 2 Example 3 CF SE (dB) 60 46 50 45

[0051] It can be seen that the total shielding effectiveness of CF is the lowest. The SnO2 / CF in Example 2 changes the original smooth surface morphology of carbon fiber, enhances the dielectric loss effect, and thus improves the electromagnetic shielding performance. The Fe3O4 / CF in Example 3 also improves the electromagnetic shielding effectiveness. However, the improvement of the electromagnetic wave shielding effectiveness is limited when they are introduced alone. In Fe3O4 / SnO2 / CF of Example 1, Fe3O4 particles and SnO2 particles are co-loaded on carbon fiber. The Fe3O4 particles exhibit a unique morphology, interweave with SnO2 particles, and form a more compact composite structure. The construction of this multi-level structure effectively promotes the synergistic effect of magnetic loss and dielectric loss, and greatly enhances the electromagnetic shielding performance of the material.

Claims

1. A method for preparing modified carbon fiber, characterized in that: The following steps are involved: S1. Dissolve SnCl4.5H2O in deionized water, and stir to obtain solution A; S2, subjecting the desized carbon fiber cloth to a hydrothermal reaction in the solution A, washing and drying, to obtain SnO2 / CF; S3, dissolving FeCl3.6H2O, FeCl2.4H2O and alkali in deionized water, and obtaining solution B after fully dissolving; S4. Add the SnO2 / CF into the solution B and stir at 80°C under N2 atmosphere to obtain Fe3O4 / SnO2 / CF.

2. The method for preparing modified carbon fiber according to claim 1, characterized in that: The ratio of the mass of SnCl4.5H2O to the volume of the solvent in the solution A in step S1 is (0.01-20) g:100 mL.

3. The method for preparing Fe3O4 / SnO2 multi-level structure modified carbon fiber according to claim 1, characterized in that: The stirring time in step S1 is 0.5h to 24h.

4. The method for preparing modified carbon fiber according to claim 1, characterized in that: The desizing carbon fiber cloth is obtained by washing the carbon fiber cloth in a condensation reflux manner, using condensed water as a condensation reflux agent and 80° C. acetone as a solvent and a cleaning agent.

5. The method for preparing modified carbon fiber according to claim 4, characterized in that: The carbon fiber cloth is one of 1K / 3K carbon fiber plain / twill fabric, electrostatically spun carbon fiber, and carbon fiber needle felt, or a mixture of at least two of them.

6. The method for preparing modified carbon fiber according to claim 1, characterized in that: The hydrothermal reaction time in step S2 is 0.5h to 15h, and the reaction temperature is 100°C to 150°C.

7. The method for preparing modified carbon fiber according to claim 1, characterized in that: The alkali in step S3 is sodium hydroxide.

8. The method for preparing modified carbon fiber according to claim 7, characterized in that: The molar ratio of FeCl3.6H2O, FeCl2.4H2O and sodium hydroxide is 0.5-2:0.1-5:0.01-5.

9. A modified carbon fiber, characterized in that: The method is used to prepare the product according to any one of claims 1 to 8.

10. Use of the modified carbon fiber as claimed in claim 9 in the field of electromagnetic shielding.

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