A fe-ni-c-cnts-carbon fiber composite material, a preparation method and application thereof

Abstract

The application discloses a FeNi-C-CNTs-carbon fiber composite material and a preparation method and application thereof, and comprises the following steps: (1) cutting carbon fibers into short fibers and dispersing the short fibers into fiber bundles, then fixing the fiber bundles and performing electrostatic dispersion; (2) spraying an adhesive on surfaces of the dispersed carbon fibers to form an adhesive layer on the surfaces of the carbon fibers, and then performing pre-solidification treatment of the adhesive; and (3) using a horizontal tube furnace, using a mixture of iron acetylacetonate and nickel acetylacetonate as a metal precursor, and performing chemical vapor deposition. In the FeNi-C-CNTs-carbon fiber composite material, FeNi alloy nanoparticles and carbon nanotubes cooperatively construct a three-dimensional conductive network, and by virtue of the unique structure, the composite material strengthens wave absorption mechanisms such as magnetic loss, dielectric loss and multiple scattering, significantly improves wave absorption performance and widens an effective frequency band, and has excellent microwave absorption performance and structural stability.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing materials, and particularly relates to a FeNi-C-CNTs-carbon fiber composite material, its preparation method, and its application. Background Technology

[0002] With the widespread adoption of 5G and IoT technologies, the electromagnetic environment is becoming increasingly complex, making it difficult for traditional absorbers to meet the ever-increasing electromagnetic compatibility requirements. Furthermore, the trend towards thinner and lighter designs in electronic devices is placing stricter constraints on the thickness and weight of absorbing materials. These diverse application demands are driving the evolution of this material towards ultra-thin, wide-bandwidth, and intelligent response technologies, and have spurred a surge in the research and development of next-generation high-performance absorbing materials.

[0003] Traditional microwave absorbing materials such as ferrites and metal powders / magnetic metal powders often suffer from inherent defects in practical applications, such as high density, narrow bandwidth, or insufficient environmental stability. In recent years, metal-carbon composite nanomaterials have shown great potential due to their tunable electromagnetic properties and good overall stability. However, the effective composite of metals and carbon materials still faces challenges such as poor interfacial compatibility and complex structural control, resulting in less than ideal microwave absorption performance. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a FeNi-C-CNTs-carbon fiber composite material, its preparation method and its application as a microwave absorbing material, so as to significantly improve the microwave absorption performance.

[0005] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0006] A method for preparing FeNi-C-CNTs-carbon fiber composite material includes the following steps:

[0007] (1) The carbon fiber is cut into short fibers and dispersed into fiber bundles, and then the fiber bundles are fixed and electrostatically dispersed.

[0008] (2) Spray adhesive onto the surface of dispersed carbon fibers to form an adhesive layer on the surface of the carbon fibers, and then perform pre-curing treatment of the adhesive to obtain pre-treated carbon fibers.

[0009] (3) A horizontal tube furnace is adopted. The furnace body is arranged with a precursor evaporation zone, a reaction zone and a deposition zone in sequence along the airflow direction. The temperature of the precursor evaporation zone is controlled at 200-240℃, the temperature of the reaction zone is set at 900-1000℃, and the temperature of the deposition zone is maintained at 400-500℃. A mixture of iron acetylacetone and nickel acetylacetone is used as a metal precursor and placed in the precursor evaporation zone. The pretreated carbon fiber is placed in the deposition zone. Hydrogen is used as the carrier gas and reaction atmosphere. The internal pressure of the system is maintained by a vacuum pump system. Chemical vapor deposition is carried out to grow FeNi-C-CNTs on the surface of carbon fiber to obtain FeNi-C-CNTs-carbon fiber composite material.

[0010] As a further improvement, the short fiber in step (1) has a length of 3.0-4.0 cm, and each fiber bundle contains 800-1000 monofilament fibers.

[0011] As a further improvement, the fixing in step (1) involves inserting fiber bundles into a porous substrate, with each bundle inserted into one hole; the electrostatic dispersion involves using an electrostatic meter to carry static electricity on the surface of the carbon fiber bundles and using electrostatic repulsion to disperse them.

[0012] As a further improvement, the adhesive in step (2) is prepared from phenolic resin, ethylenediamine and anhydrous ethanol in a mass ratio of 8-15:1-2:20-40.

[0013] As a further improvement, the pre-curing treatment in step (2) is to dry in a vacuum dryer at 55~65°C for 1.5~2.5 hours.

[0014] As a further improvement, the distance between the precursor evaporation zone and the reaction zone in step (3) is controlled at 20-30 cm.

[0015] As a further improvement, the molar ratio of iron to nickel in iron acetylacetone and nickel acetylacetone in step (3) is 1:1.

[0016] As a further improvement, the total hydrogen flow rate in step (3) is 200-300 sccm, the pressure is maintained at 100-200 Pa, and the reaction lasts for 2-5 hours; after the reaction is completed, the system is allowed to cool naturally to room temperature under the protection of hydrogen atmosphere.

[0017] The present invention provides a FeNi-C-CNTs-carbon fiber composite material, which is prepared by the method described above. In this material, FeNi alloy nanoparticles are embedded in the carbon matrix and intertwine with carbon nanotubes to form a three-dimensional conductive network, which is uniformly loaded on the carbon fiber surface and together constitutes a multi-level composite structure.

[0018] The present invention also provides an application of the FeNi-C-CNTs-carbon fiber composite material, wherein the FeNi-C-CNTs-carbon fiber composite material is used as a microwave absorbing material.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] In the FeNi-C-CNTs-carbon fiber composite material of this invention, FeNi alloy nanoparticles and carbon nanotubes synergistically construct a three-dimensional conductive network. This unique structure enhances absorption mechanisms such as magnetic loss, dielectric loss, and multiple scattering, significantly improving absorption performance and broadening the effective frequency band. It exhibits excellent microwave absorption performance and structural stability.

[0021] This invention utilizes chemical vapor deposition to achieve in-situ growth of FeNi-C-CNTs on carbon fibers, enabling the one-time preparation of large-area FeNi-C-CNTs-carbon fiber composite materials. The process is simple, low-cost, and highly efficient, overcoming the problems of weak interfacial bonding and difficult structural control in traditional composite materials. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 These are model diagrams and optical micrographs of carbon fiber bundles inserted into a porous substrate. (a) is a model diagram of carbon fiber bundles inserted into a porous substrate, and (b) and (c) are optical micrographs, which are top views and front views, respectively.

[0024] Figure 2 These are scanning electron microscope (SEM) images of carbon fibers and FeNi-C-CNTs-carbon fiber composites: (a) SEM image of carbon fibers; (b) low-magnification SEM image of a typical FeNi-C-CNTs-carbon fiber composite; (c) low-magnification SEM image of S8; (d) low-magnification SEM image of S12; (e) low-magnification SEM image of S16; (f) low-magnification SEM image of S20.

[0025] Figure 3The images are scanning transmission electron microscope (STEM) and transmission electron microscope (TEM) images of FeNi-C-CNTs-carbon fiber composite material: (a) and (b) are typical STEM images and corresponding TEM images of FeNi-C-CNTs-carbon fiber composite material, respectively; (c) is a side STEM image of FeNi-C-CNTs-carbon fiber composite material; (d), (e) and (f) are TEM images of FeNi-C-CNTs at different locations.

[0026] Figure 4 This is a diagram illustrating the formation mechanism of FeNi-C-CNTs-carbon fiber composite materials.

[0027] Figure 5 This is the S8 two-dimensional reflection loss spectrum (Example 1).

[0028] Figure 6 This is the S12 two-dimensional reflection loss spectrum (Example 2).

[0029] Figure 7 This is the S16 two-dimensional reflection loss spectrum (Example 3).

[0030] Figure 8 This is the S20 two-dimensional reflection loss spectrum (Example 4). Detailed Implementation

[0031] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0032] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0033] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0034] In some specific embodiments of the present invention, a method for preparing FeNi-C-CNTs-carbon fiber composite material is provided, comprising two main steps: pretreatment of carbon fibers and growth of FeNi-C-CNTs.

[0035] Pretreated carbon fiber:

[0036] First, the carbon fiber is cut into short fibers, preferably 3.0-4.0 cm in length. Then, the cut carbon fiber is dispersed into fiber bundles, preferably each bundle containing 800-1000 monofilaments. The fiber bundles are then fixed to provide support for subsequent processing. For example, the fiber bundles are inserted into... Figure 1 In the porous substrate shown in (a), blue represents fiber bundles and green represents the porous substrate. The porous substrate has multiple holes on the substrate for the fiber bundles to be inserted, with each bundle inserted into one hole.

[0037] Next, the fixed carbon fibers are electrostatically dispersed and coated with adhesive. For example, an electrostatic meter is used to charge the surface of the carbon fiber bundle with static electricity, and electrostatic repulsion is used to disperse the fibers as much as possible, avoiding fiber agglomeration. Adhesive is then sprayed onto the dispersed carbon fiber surface. In some embodiments, the adhesive is prepared and diluted from phenolic resin (adhesive), ethylenediamine (curing agent), and anhydrous ethanol (solvent) in a certain mass ratio (8-15:1-2:20-40) (the above ratio is the diluted ratio), and atomized using an atomizer to uniformly spray it onto the charged carbon fiber surface, forming a thin and continuous adhesive layer.

[0038] Subsequently, the adhesive is pre-cured to obtain pre-treated carbon fibers. In some embodiments, the carbon fiber bundles sprayed with adhesive are placed in a vacuum dryer and dried at 55~65°C (preferably 60°C) for 1.5~2.5 hours (preferably 2 hours) to allow the adhesive to initially cure, enhance its bonding force with the fiber surface, and lay the foundation for the subsequent high-temperature stage of adhesive carbonization.

[0039] FeNi-C-CNTs growth:

[0040] FeNi-C-CNTs were grown on carbon fibers using chemical vapor deposition.

[0041] FeNi-C-CNTs growth is performed in a horizontal tube furnace, with a precursor evaporation zone, a reaction zone, and a deposition zone arranged sequentially along the airflow direction. Preferably, the distance between the evaporation zone and the reaction zone is controlled at 20-30 cm, the distance between the reaction zone and the deposition zone is controlled at 15-25 cm, the furnace inner diameter is 50-80 mm, and the length is 100-120 cm.

[0042] A mixture of iron acetylacetonate (Fe(acac)3) and nickel acetylacetonate (Ni(acac)2) (iron-nickel molar ratio 1:1, preferably with a purity of not less than 97%) is used as a metal precursor. This precursor is placed in an evaporation zone at a temperature controlled at 200-240°C to volatilize it into a gaseous state. Pretreated carbon fibers (along with a porous substrate) are placed in a deposition zone at a temperature maintained at 400-500°C. The reaction zone temperature is set to 900-1000°C. Preferably, the mass ratio of the pretreated carbon fibers to (iron acetylacetonate + nickel acetylacetonate) is 1:(30-50).

[0043] Hydrogen is used as the carrier gas and reaction atmosphere, with the total gas flow rate preferably controlled at 200-300 sccm (standard cubic centimeters per minute). Preferably, a vacuum pump system is used to maintain the internal pressure of the system at 100-200 Pa, and the reaction lasts for 2-5 hours. The decomposition products formed in the reaction zone further generate FeNi-C-CNTs upon reaching the carbon fibers. Since there is an adhesive on the carbon fiber surface, the carbonized adhesive forms sites for FeNi-C-CNTs attachment, thereby growing FeNi-C-CNTs on the carbon fiber surface, ultimately obtaining a FeNi-C-CNTs-carbon fiber composite material.

[0044] Finally, the system was cooled and the sample was collected. After the reaction was complete, the system was allowed to cool naturally to room temperature under a hydrogen atmosphere, and the sample was removed to obtain the final FeNi-C-CNTs-carbon fiber composite material.

[0045] like Figure 4 The mechanism involves the gaseous precursor being transported by the carrier gas to the high-temperature reaction zone where it decomposes, undergoing the following main steps to form FeNi-C-CNTs: Fe(acac)3 and Ni(acac)2 first decompose to generate iron and nickel atoms and (acac)· free radicals, as shown in the following reaction:

[0046] Fe(acac)3(g)→Fe(acac)·(g)+(acac)(g),

[0047] Fe(acac)·(g)→Fe (g)+(acac)·(g),

[0048] Ni(acac)2(g)→Ni(acac)·(g)+(acac)(g),

[0049] Ni(acac)·(g)→Ni (g)+(acac)·(g);

[0050] Iron and nickel atoms condense to form FeNi atom clusters; these clusters further catalyze the decomposition of (acac)· free radicals to produce carbon atoms, which are absorbed to form FeNiC clusters; FeNiC clusters aggregate through collisions, iron and nickel atoms combine to form alloy nanoparticles, while carbon atoms precipitate to form a carbon layer. Small-sized FeNi nanonuclei (diameter less than 10 nm) are encapsulated by the carbon layer to form FeNi-C core-shell nanoparticles, which are tightly attached to the surface of large-sized FeNi-terminated carbon nanotubes through strong surface adsorption. Because small-sized FeNi particles are covered by carbon and have limited dissolved carbon atoms, they easily lose activity and cannot catalyze the growth of carbon nanotubes; while large-sized FeNi nanoparticles can dissolve more carbon atoms, and the carbon layer covering their surface is relatively thin compared to the particle size, thus enabling the catalytic growth of carbon nanotubes. Ultimately, a FeNi-C-CNTs composite structure is constructed. The adhesive pre-coated on the carbon fiber surface forms a large number of active sites after high-temperature carbonization, which effectively promotes the nucleation, attachment and directional growth of FeNi-C-CNTs, and the final product is generated on the carbon fiber surface in the deposition area.

[0051] This FeNi-C-CNTs-carbon fiber composite material uses carbon fiber as a substrate, with FeNi alloy nanoparticles embedded in the carbon matrix (encased in carbon layers) and intertwined with in-situ grown carbon nanotubes to form a three-dimensional conductive network. The nanoparticles are uniformly loaded on the fiber surface, together forming a multi-level composite structure that exhibits excellent broadband microwave absorption performance and good structural stability.

[0052] During implementation, the following six key conditions must be strictly controlled: First, the carbon fiber substrate needs to be cut to a size of 3.0-4.0 mm. Short fiber segments of cm are physically dispersed to form uniform fiber bundles containing 800-1000 monofilaments per bundle (this size and dispersion ensures uniformity of subsequent coating and reaction efficiency), and fixed on a porous substrate (providing a stable support base); secondly, the fiber surface is charged through electrostatic dispersion to achieve monofilament separation (avoiding fiber agglomeration affecting the coating effect), and a binder prepared by phenolic resin, ethylenediamine, and anhydrous ethanol (8-15:1-2:20-40) is sprayed (this ratio can form suitable viscosity and activity) to form a uniform pre-coating; thirdly, the coating is pre-cured in a vacuum environment at 60℃ for 2 hours (promoting the initial cross-linking and curing of the binder), enhancing the bonding force and laying the foundation for the subsequent high-temperature carbonization to generate active sites; fourthly, a zoned temperature-controlled CVD process is adopted, with the evaporation zone at 200-240℃ (ensuring sufficient vaporization of the precursor), the reaction zone at 900-1000℃ (ensuring complete decomposition of the precursor), and the deposition zone at 400-500℃ (providing a suitable temperature for carbon nanotube growth), and the temperature at 200-300℃. SCCM uses hydrogen as the carrier gas (providing a reducing atmosphere and transporting the precursor), and reacts for 2-5 hours at a low pressure of 100-200 Pa (to maintain the environment required for gas-phase reaction) (ensuring sufficient carbon nanotube growth); fifth, the precursor decomposes via free radicals to form FeNi alloy clusters (serving as catalytic active centers), catalyzing the generation of carbon atoms and self-assembling through size-selective effects (<10nm nanonuclei are easily encapsulated by carbon layers to form a core-shell structure), ultimately constructing a FeNi-C-CNTs composite structure; sixth, after the reaction, the sample is cooled to room temperature under hydrogen protection (to prevent oxidation of the sample at high temperatures), ensuring the acquisition of a structurally complete final composite material.

[0053] This invention employs electrostatic dispersion technology and a binder pre-coating process to pretreat carbon fibers. Then, through in-situ growth and heat treatment, using iron acetylacetonate and nickel acetylacetonate as precursors, and precisely controlling the temperature range, pressure, and gas flow parameters of the chemical vapor deposition system, FeNi-C-CNTs are catalytically grown in situ on the carbon fiber surface. The carbonized binder provides attachment sites for the FeNi-C-CNTs, uniformly constructing a multidimensional FeNi-C-CNTs nanostructure on the carbon fiber surface, ultimately forming a FeNi-C-CNTs-carbon fiber composite material with a multi-level composite structure. This not only enhances interfacial polarization and magnetic coupling effects but also significantly optimizes impedance matching characteristics. This multi-scale composite structure effectively integrates magnetic loss and dielectric loss mechanisms, achieving broadband strong absorption and structural functionality.

[0054] Compared with conventional microwave absorbing systems, this composite material exhibits significant advantages in absorption performance, bandwidth, mechanical strength, and environmental friendliness, providing a new strategy for the design and fabrication of next-generation high-performance microwave absorbing materials.

[0055] Example 1 (Low Precursor Load)

[0056] 1. Pre-treated carbon fiber:

[0057] The purchased carbon fiber was cut into short fibers with a length of 3.5 cm. The cut carbon fiber was dispersed into bundles, each bundle containing about 900 carbon fibers, and then inserted into a self-made porous substrate for fixation.

[0058] An electrostatic meter is used to charge the carbon fiber bundles with static electricity, allowing them to disperse fully.

[0059] Adhesive preparation: Mix phenolic resin, ethylenediamine, and ethanol in a mass ratio of 10:1.2:30 and stir to dilute. Use an atomizer to spray it evenly onto the surface of the charged carbon fiber.

[0060] The carbon fiber bundles coated with adhesive were placed in a vacuum drying oven at 60°C and dried for 2.5 hours.

[0061] 2. Growth of FeNi-C-CNTs:

[0062] A horizontal tubular furnace system with an inner diameter of 60 mm and a length of 110 cm was used. The distance between the evaporation zone and the reaction zone was set to 25 cm, and the distance between the reaction zone and the deposition zone was set to 20 cm.

[0063] Weigh a total of 8g of the metal precursor (ferric acetylacetone and nickel acetylacetone with a purity ≥97%, mixed uniformly at a 1:1 iron-nickel molar ratio), place it in a quartz boat, and then place it in the evaporation zone of a tube furnace. Place 0.2g of pretreated carbon fiber in the deposition zone. Set the evaporation zone temperature to 220℃, the reaction zone temperature to 950℃, and the deposition zone temperature to 450℃. Introduce hydrogen gas into the system as a carrier gas, controlling the total flow rate at 250 sccm. Turn on the vacuum pump system to maintain and stabilize the internal pressure of the system at 150 Pa. React under the above conditions for 3 hours.

[0064] After the reaction was completed, the mixture was naturally cooled to room temperature under a hydrogen atmosphere to obtain the FeNi-C-CNTs-carbon fiber composite material.

[0065] Example 2 (Medium precursor load)

[0066] 1. Pre-treated carbon fiber:

[0067] The carbon fiber pretreatment steps were exactly the same as in Example 1 (3.5 cm in length, 900 fibers per bundle, adhesive ratio of 10:1.2:30, drying at 60°C for 2.5 hours) to ensure the uniqueness of the variables.

[0068] 2. Growth of FeNi-C-CNTs:

[0069] The growth equipment and system parameters were kept consistent with those in Example 1 (furnace size, zone spacing, temperature of each zone, carrier gas flow rate, system pressure, and reaction time).

[0070] The only change is that the total mass of the metal precursors (iron acetylacetone and nickel acetylacetone, molar ratio 1:1) is increased to a total of 12g.

[0071] After the reaction was completed, the mixture was naturally cooled to room temperature to obtain the FeNi-C-CNTs-carbon fiber composite material.

[0072] Example 3 (High Precursor Load)

[0073] 1. Pre-treated carbon fiber:

[0074] The carbon fiber pretreatment steps are exactly the same as those in Examples 1 and 2.

[0075] 2. Growth of FeNi-C-CNTs:

[0076] The growth equipment and system parameters are consistent with those in Examples 1 and 2.

[0077] The only change is that the total mass of the metal precursors (iron acetylacetone and nickel acetylacetone, molar ratio 1:1) is increased to a total of 16g.

[0078] After the reaction was completed, the mixture was naturally cooled to room temperature to obtain the FeNi-C-CNTs-carbon fiber composite material.

[0079] Example 4 (Ultra-high precursor load)

[0080] 1. Pre-treated carbon fiber:

[0081] The carbon fiber pretreatment steps are the same as those in the previous embodiments.

[0082] 2. Growth of FeNi-C-CNTs:

[0083] The growth equipment and system parameters can remain unchanged, or to accommodate a larger amount of precursors, the temperature of the evaporation zone can be slightly increased to 240°C to ensure full vaporization.

[0084] Change point: Increase the total mass of the metal precursor to a total of 20g.

[0085] After the reaction was completed, the mixture was naturally cooled to room temperature to obtain the FeNi-C-CNTs-carbon fiber composite material.

[0086] Based on the quality of the precursor in the embodiments, the samples obtained in each embodiment are named S8, S12, S16 and S20, respectively.

[0087] Figure 2The images are scanning electron microscope (SEM) images of carbon fibers and FeNi-C-CNTs-carbon fiber composites: (a) SEM image of carbon fibers; (b) low-magnification SEM image of a typical FeNi-C-CNTs-carbon fiber composite; (c) low-magnification SEM image of S8; (d) low-magnification SEM image of S12; (e) low-magnification SEM image of S16; (f) low-magnification SEM image of S20. In Example 1, the CNT density loaded on the material surface was relatively low, forming a sparse three-dimensional network. In Example 2, compared to Example 1, due to the increased precursor mass, more catalyst particles were generated, and the CNT density grown on the carbon fiber surface was significantly increased, resulting in a denser and more complete three-dimensional conductive network. In Example 3, the CNTs loaded on the carbon fiber surface were extremely dense, almost completely covering the carbon fiber surface, forming a very thick interwoven network. The FeNi-C nanoparticle content was also higher. In Example 4, the CNT growth density in the composite material reached its limit, possibly exhibiting a distinct layered or stacked structure. It should be noted that excessive precursor content may lead to excessively large catalyst particles or agglomeration, which may affect the quality of CNTs and the mechanical properties of composite materials.

[0088] Figure 3 These are scanning transmission electron microscope (STEM) and transmission electron microscope (TEM) images of FeNi-C-CNTs-carbon fiber composite materials: (a) and (b) are typical STEM images and corresponding TEM images of the FeNi-C-CNTs-carbon fiber composite material, respectively; (c) is a side STEM image of the FeNi-C-CNTs-carbon fiber composite material; (d), (e), and (f) are TEM images of FeNi-C-CNTs at different locations. Image (d) illustrates that the material covering the carbon fiber is FeNi-C-CNTs, and image (e) illustrates that the surface of the CNTs is covered with fine FeNi particles.

[0089] Each sample was pressed into a coaxial ring, and its electromagnetic parameters were tested using a vector network analyzer. The reflection loss (RL) value was then calculated based on the electromagnetic parameters. Figure 5 The two-dimensional reflection loss spectrum of S8 samples with different thicknesses (2mm-5mm) is shown in Example 1, with the maximum effective bandwidth being 3.2 GHz. Figure 6 The two-dimensional reflection loss spectrum of S12 samples with different thicknesses (Example 2) shows that the maximum effective bandwidth is 8.8 GHz, which is the optimal sample. Figure 7 This is a two-dimensional reflection loss spectrum of S16 samples with different thicknesses (Example 3), with an effective bandwidth of 6.1 GHz. Figure 8 This is a two-dimensional reflection loss spectrum of S20 samples with different thicknesses (Example 4), with an effective bandwidth of 0 GHz.

[0090] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for preparing FeNi-C-CNTs-carbon fiber composite material, characterized in that, Includes the following steps: (1) The carbon fiber is cut into short fibers and dispersed into fiber bundles, and then the fiber bundles are fixed and electrostatically dispersed. (2) Spray adhesive onto the surface of dispersed carbon fibers to form an adhesive layer on the surface of the carbon fibers, and then perform pre-curing treatment of the adhesive to obtain pre-treated carbon fibers. (3) A horizontal tube furnace is adopted. The furnace body is arranged with a precursor evaporation zone, a reaction zone and a deposition zone in sequence along the airflow direction. The temperature of the precursor evaporation zone is controlled at 200-240℃, the temperature of the reaction zone is set at 900-1000℃, and the temperature of the deposition zone is maintained at 400-500℃. A mixture of iron acetylacetone and nickel acetylacetone is used as a metal precursor and placed in the precursor evaporation zone. The pretreated carbon fiber is placed in the deposition zone. Hydrogen is used as the carrier gas and reaction atmosphere. The internal pressure of the system is maintained by a vacuum pump system. Chemical vapor deposition is carried out to grow FeNi-C-CNTs on the surface of carbon fiber to obtain FeNi-C-CNTs-carbon fiber composite material.

2. The method for preparing the FeNi-C-CNTs-carbon fiber composite material according to claim 1, characterized in that, The short fiber in step (1) has a length of 3.0-4.0 cm, and each fiber bundle contains 800-1000 monofilament fibers.

3. The method for preparing the FeNi-C-CNTs-carbon fiber composite material according to claim 1 or 2, characterized in that, The fixing in step (1) involves inserting fiber bundles into a porous substrate, with each bundle inserted into one hole; the electrostatic dispersion involves using an electrostatic meter to make the surface of the carbon fiber bundles carry static electricity, and then using electrostatic repulsion to disperse them.

4. The method for preparing the FeNi-C-CNTs-carbon fiber composite material according to claim 1, characterized in that, The adhesive in step (2) is prepared by mixing phenolic resin, ethylenediamine and anhydrous ethanol in a mass ratio of 8-15:1-2:20-40.

5. The method for preparing the FeNi-C-CNTs-carbon fiber composite material according to claim 1 or 4, characterized in that, The pre-curing treatment in step (2) is to dry in a vacuum dryer at 55~65℃ for 1.5~2.5 hours.

6. The method for preparing the FeNi-C-CNTs-carbon fiber composite material according to claim 1, characterized in that, In step (3), the distance between the precursor evaporation zone and the reaction zone is controlled to be 20-30 cm.

7. The method for preparing the FeNi-C-CNTs-carbon fiber composite material according to claim 1 or 6, characterized in that, In step (3), the molar ratio of iron to nickel in iron acetylacetone and nickel acetylacetone is 1:

1.

8. The method for preparing the FeNi-C-CNTs-carbon fiber composite material according to claim 1 or 6, characterized in that, In step (3), the total hydrogen flow rate is 200-300 sccm, the pressure is maintained at 100-200 Pa, and the reaction lasts for 2-5 hours. After the reaction is completed, the system is allowed to cool naturally to room temperature under the protection of hydrogen atmosphere.

9. A FeNi-C-CNTs-carbon fiber composite material, characterized in that, It is prepared by the method described in any one of claims 1 to 8. In this material, FeNi alloy nanoparticles are embedded in a carbon matrix and intertwine with carbon nanotubes to form a three-dimensional conductive network, which is uniformly loaded on the surface of carbon fibers and together constitutes a multi-level composite structure.

10. An application of the FeNi-C-CNTs-carbon fiber composite material according to claim 9, characterized in that, The FeNi-C-CNTs-carbon fiber composite material was used as a microwave absorbing material.

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