A bead chain-shaped FeSi / SiC@C high-temperature-resistant carbon fiber wave-absorbing composite material

Abstract

The application belongs to the technical field of magnetic wave-absorbing materials, and particularly relates to a beaded chain-shaped FeSi / SiC@C high-temperature-resistant carbon fiber wave-absorbing composite material. The application fundamentally solves the long-standing technical contradiction in the field of high-temperature-resistant electromagnetic wave-absorbing materials, ensures that the material has high-temperature stability and oxidation resistance at 800 DEG C, realizes high performance of wide frequency (6.5 GHz effective absorption bandwidth), strong absorption (-30 dB) and low filling ratio (10%), and has the potential of lightweight coating and good bonding strength due to the integrated forming of electrospinning. The beaded chain-shaped core-shell heterostructure design breaks through the technical bottleneck of narrow bandwidth and rapid performance attenuation of traditional materials due to high-temperature oxidation inactivation and single loss mechanism, and provides a key material solution for the engineering application of wide-frequency high-efficiency wave-absorbing coating in high-temperature environments.

Description

Technical Field

[0001] This invention belongs to the field of magnetic microwave absorbing materials technology, specifically relating to a beaded FeSi / SiC@C high-temperature resistant carbon fiber microwave absorbing composite material. Background Technology

[0002] The rapid development of electronic communication and radar detection technologies in fields such as smart homes, drones and robots, air traffic control, and military surveillance has generated a significant amount of invisible pollution, such as unwanted electromagnetic and sound waves. Electromagnetic pollution poses a serious threat to network communications, national defense, and human health. Currently, electromagnetic shielding and absorbing materials can mitigate electromagnetic radiation pollution and extend the service life of military equipment. However, the use of shielding materials can lead to electromagnetic wave reflection, causing re-pollution. Therefore, a highly efficient and stable electromagnetic wave absorbing material is needed to fundamentally solve the problem of electromagnetic pollution.

[0003] On the other hand, the rapid development of communication technologies and intelligent systems based on gigahertz electromagnetic waves (EMW) has ushered humanity into the intelligent era. The widespread use of intelligent devices has greatly improved the convenience of daily life. However, electromagnetic radiation pollution not only affects the performance of precision electronic instruments but also poses a serious threat to the environment and human health. Therefore, the development of electromagnetic wave absorbing materials with low reflection and high loss as primary objectives has become increasingly urgent. More importantly, the widespread use of portable and wearable electronic devices presents new challenges to electromagnetic wave absorbing materials, demanding lightweight, broadband absorption, and high absorption efficiency. Among promising candidates, carbon-based materials, such as carbon fibers (CNF), carbon microspheres, and graphene, are highly promising due to their light weight, high dielectric constant, large specific surface area, and good chemical stability. CNF also possesses a high aspect ratio and a three-dimensional (3D) network structure formed through cross-linking. The high aspect ratio effectively blocks the EMW transmission path, increasing the probability of dissipation. The 3D network structure promotes electron migration and hopping, thereby increasing conduction losses. However, the high conductivity of pure CNF often leads to impedance mismatch, causing most electromagnetic waves to fail to enter the material and be reflected. Furthermore, the single loss mechanism of CNF limits its ability to attenuate electromagnetic waves, hindering broadband absorption. Multi-component composite materials effectively overcome the limitations of single components by utilizing the synergistic effect between different components, thereby improving electromagnetic wave dissipation. Among these, electrospinning is particularly advantageous due to its ability to produce tunable surface properties, customizable composition, and controllable structural configurations. Summary of the Invention

[0004] The following problems exist with existing technologies:

[0005] 1. The contradiction between high-temperature stability and microwave absorption performance: Traditional magnetic materials (such as ferrites and metal powders) are prone to oxidation and demagnetization at high temperatures, thus losing their microwave absorption ability; while high-temperature resistant ceramic materials (such as SiC) have narrow absorption bandwidth and low efficiency, making it difficult to balance high-temperature stability and high-efficiency broadband absorption.

[0006] 2. The contradiction between wide bandwidth and strong absorption: Most materials rely on a single loss mechanism (pure dielectric or pure magnetic), and impedance matching and attenuation capabilities are difficult to optimize in a coordinated manner, making it difficult to simultaneously meet high performance requirements for effective absorption bandwidth (usually <4 GHz) and absorption intensity.

[0007] 3. The contradiction between high filling rate and lightweight / processability: In order to achieve the practical absorption threshold, traditional microwave absorbers need to be filled with a high proportion (often >30%), resulting in high coating density, poor flexibility, and easy cracking, which makes it difficult to meet the urgent needs of modern equipment for thin coatings.

[0008] 4. The disconnect between laboratory performance and engineering applications: Existing material designs mostly focus on intrinsic electromagnetic parameters, lacking systematic solutions to key engineering issues such as coating bonding strength, thermal shock resistance, and long-term stability in high-temperature environments. Laboratory performance is difficult to translate into actual products.

[0009] 5. Rigid material system design: Functional composite is mainly achieved through physical mixing or simple coating. The interfacial bonding between components is weak, the structural controllability is poor, the performance regulation dimension is limited, and it is impossible to carry out rational customized design for specific frequency bands and temperatures.

[0010] This invention provides a structurally innovative, performance-synergistic, and engineering-applicable beaded FeSi / SiC@C high-temperature resistant carbon fiber microwave absorbing composite material.

[0011] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0012] A beaded FeSi / SiC@C high-temperature resistant carbon fiber microwave absorbing composite material, wherein the composite material has a 3D network structure with spherical FeSi and nano SiC as the core layer and polyacrylonitrile (PAN) as the shell layer.

[0013] Furthermore, the length and shell thickness of the beaded composite carbon fibers can be controlled by adjusting the ratio of FeSi and SiC core layers and the ratio of shell to core layer.

[0014] A method for preparing a beaded FeSi / SiC@C high-temperature resistant carbon fiber microwave absorbing composite material includes the following steps:

[0015] Step 1: Spherical FeSi, nano-worm-like SiC and polyacrylonitrile (PAN) are dissolved in N,N-dimethylformamide (DMF), heated and stirred until uniform, so that FeSi and SiC are uniformly dispersed in DMF to form a stable suspension slurry, thus obtaining slurry A;

[0016] Step 2: Dissolve PAN separately in DMF, heat and stir until homogeneous to obtain slurry B;

[0017] Step 3: Coaxial electrospinning of slurry A and slurry B, with slurry A as the core layer and slurry B as the shell layer, and drying to remove bound water and volatiles to obtain the precursor.

[0018] Step 4: Pre-oxidize the precursor by heating it to 200℃~250℃ at a rate of 1℃ / min;

[0019] Step 5: Then, using argon as a protective gas, the temperature is increased at 3℃ / min. First, the temperature is increased to 380~420℃ and held for 40~80min, and then the temperature is increased to 750℃~850℃ and held for 40~80min. Finally, FeSi / SiC@C composite fiber material is obtained.

[0020] Furthermore, in step 1, the mass ratio of spherical FeSi, nano-worm-like SiC, and polyacrylonitrile (PAN) is 1:1:4.

[0021] Furthermore, the Fe / Si mass ratio in FeSi and SiC is 1~3:1.

[0022] Furthermore, the amount of polyacrylonitrile used in slurry A and slurry B remains the same.

[0023] Furthermore, the specific operation of coaxial electrospinning in step 3 is as follows: slurry A and slurry B are respectively loaded into two syringes, and coaxial electrospinning is performed using inner 25G and outer 13G coaxial needles at speeds of 0.03 μL / min and 0.04 μL / min, respectively. The air humidity is 33.9%, the temperature is 21℃, a roller filled with oil paper is used as the receiver, the receiver rotation speed is 140 rpm, and the voltage is 20 kV.

[0024] Furthermore, the pre-oxidation temperature in step 4 is 225℃~240℃.

[0025] Furthermore, in step 5, the temperature is first raised to 400°C and held for 60 minutes, and then raised to 800°C and held for 60 minutes.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] Traditional magnetic absorbing materials (such as ferrites and metal powders) are prone to oxidation and phase transitions at high temperatures, leading to a sharp decrease in magnetic loss. High-temperature resistant ceramic materials (such as pure SiC) generally suffer from narrow absorption bandwidth and insufficient absorption intensity. This invention fundamentally solves the long-standing technical contradictions in the field of high-temperature electromagnetic wave absorbing materials. While ensuring high-temperature stability and oxidation resistance at 800℃, it achieves high performance with a wide bandwidth (6.5 GHz effective absorption bandwidth), strong absorption (-30 dB), and low filler ratio (10%). It also incorporates the integrated molding capabilities of electrospinning, possessing the potential for lightweight coating and good bonding strength. Through a unique "beaded chain" core-shell heterostructure design, it coordinates magnetic and dielectric loss mechanisms, overcoming the technical bottlenecks of narrow bandwidth and rapid performance degradation caused by high-temperature oxidation deactivation and a single loss mechanism in traditional materials. This provides a key material solution for the engineering application of wideband, high-efficiency absorbing coatings in high-temperature environments. These materials not only require excellent wave absorption properties, but can also be relatively easy to use as coatings or structural components to meet the stringent physical, chemical and mechanical environmental requirements. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 These are scanning electron microscope (SEM) images of the morphology and structure of FeSi / SiC@C 1-1 composite fiber materials at different magnifications.

[0030] Figure 2 This is an elemental distribution diagram of FeSi / SiC@C 1-1 composite fiber material.

[0031] Figure 3 These are scanning electron microscope (SEM) images of the morphology and structure of FeSi / SiC@C 3-1 composite fiber materials at different magnifications.

[0032] Figure 4 This is an X-ray diffraction analysis diagram of FeSi / SiC@C 1-1 and FeSi / SiC@C 3-1 composite fiber materials.

[0033] Figure 5 The thermogravimetric analysis (TGA) diagrams of FeSi / SiC@C 1-1 and FeSi / SiC@C 3-1 composite fiber materials in air atmosphere are shown.

[0034] Figure 6This is a graph showing the electromagnetic wave absorption performance of FeSi / SiC@C 1-1 composite fiber material.

[0035] Figure 7 This is a scanning electron microscope image of the FeSi / SiC@C 1-1-T composite fiber material.

[0036] Figure 8 This is a graph showing the electromagnetic wave absorption performance of FeSi / SiC@C 3-1 composite fiber material. Detailed Implementation

[0037] To gain a deeper understanding of this invention, we will provide a comprehensive and detailed description. However, this invention has various implementations and is not limited to the specific examples listed herein. These examples are presented to enhance a full understanding of the disclosure of this invention.

[0038] Example 1

[0039] The first step involves weighing 0.5g of spherical FeSi, 0.5g of nano-worm-like SiC, and 2g of polyacrylonitrile (PAN) and dissolving them in 22.5mL of N,N-dimethylformamide (DMF). The mixture is heated to 80℃ and stirred until homogeneous, so that FeSi and SiC are evenly dispersed in DMF to form a stable suspension slurry, thus obtaining slurry A.

[0040] The second step involves weighing 2g of PAN and dissolving it in 22.5 mL of DMF. The mixture is heated to 80℃ and stirred until homogeneous to obtain slurry B.

[0041] The third step involves taking 10 mL of slurry A and 10 mL of slurry B and loading them into two syringes. Coaxial electrospinning is then performed using inner 25G and outer 13G coaxial needles at speeds of 0.03 μL / min and 0.04 μL / min, respectively. The air humidity is 33.9%, the temperature is 21℃, and a roller filled with oil paper is used as the receiver. The receiver rotation speed is 140 rpm and the voltage is 20 kV. Slurry A is used as the core layer and slurry B is used as the shell layer.

[0042] The fourth step is to place the mat spun by the electrospinning machine into an electric heating drying oven at 80°C for 24 hours to remove bound water and volatiles, thereby obtaining the precursor.

[0043] The fifth step is to place the dried precursor into a muffle furnace and pre-oxidize it at 230°C for 2 hours, with a heating rate of 1°C / min.

[0044] The sixth step involves placing the pre-oxidized precursor into a high-temperature tubular atmosphere furnace and heating it at 3°C / min. The temperature is first raised to 400°C and held for 60 minutes, then raised to 800°C and held for 60 minutes. Argon is used as a protective gas during this process, and the FeSi / SiC@C 1-1 composite fiber material is finally obtained. Figure 1 The diagram shows its morphological structure, which is mainly beaded. The joint structure is FeSi coated with C, and the chain is mainly composed of nano-SiC coated with C, which provides a three-dimensional skeleton for the entire beaded composite fiber structure. Figure 2 The elemental distribution diagram of FeSi / SiC@C 1-1 composite fiber material further illustrates the elemental distribution in the composite material.

[0045] Example 2

[0046] The spacing of the beaded spheres in the composite fiber material can be adjusted by changing the Fe / Si mass ratio of FeSi to SiC. For example, a FeSi / SiC ratio of 3:1 yields a more compact beaded composite fiber material, FeSi / SiC@C 3-1. Figure 3 The diagram shown is a morphological structure diagram, and it is clear that an increased number of beads are linked together by nanofibers. Figure 4 The X-ray diffraction patterns of FeSi / SiC@C1-1 and FeSi / SiC@C3-1 composite fiber materials show that the composite material is indeed composed of FeSi, SiC and C. Figure 5 Thermogravimetric analysis (TGA) diagrams of FeSi / SiC@C 1-1 and FeSi / SiC@C 3-1 composite fiber materials in air atmosphere are shown. The results indicate that the mass loss of both samples at 400℃ does not exceed 10%, demonstrating excellent oxidation resistance, and no morphological structural changes before and after high temperature. The high FeSi / SiC ratio indicates a higher content of spherical FeSi in slurry A, with the diameter of the spherical FeSi slightly larger than the fiber diameter. Compared to FeSi / SiC@C 1-1, the higher FeSi content, under the same preparation conditions, will shorten the spinning continuity and output of FeSi spheres in the same fiber, resulting in a shorter distance between the spheres. Figure 3 The images show a comparison of the microstructures of two samples: (a) FeSi / SiC@C 3-1 and (b) FeSi / SiC@C 1-1.

[0047] Example 3

[0048] The shell thickness of the composite fiber material can be adjusted by changing the amount of PAN in slurry B. Higher PAN concentration in slurry B results in higher viscosity and a thicker, denser shell at the same flow rate. For example, replacing slurry B in Scheme 1 with 3g of PAN dissolved in 22.5 mL of DMF yields a beaded composite fiber material FeSi / SiC@C 1-1-T with a thicker shell. Figure 7 This is a morphological structure diagram of FeSi / SiC@C1-1-T. If the concentration is too low, the shell may be discontinuous. Other factors determining the shell thickness include the electrospinning voltage, receiving distance, shell flow rate, and the diameter of the needles with different outer diameters.

[0049] Example 4: Absorption Performance Test

[0050] The microwave absorption performance of FeSi / SiC@C1-1 composite fiber material was tested using a vector network analyzer in the range of 2–18 GHz. The test results are shown in [reference needed]. Figure 6 Currently, military products are required to have a reflection loss value of less than -5dB (absorption rate ≥ 68.4%). According to the requirements, the reflection loss value of a 5.5mm thick sample is less than -5dB in the range of 3.74~18GHz. With a thickness of 5.0 mm, the effective absorption bandwidth is 13.83 GHz (4.17-18 GHz); with a thickness of 4.5 mm, the effective absorption bandwidth is 13.28 GHz (4.72-18 GHz); with a thickness of 4.0 mm, the effective absorption bandwidth is 12.66 GHz (5.34-18 GHz); with a thickness of 3.5 mm, the effective absorption bandwidth is 11.68 GHz (5.34-18 GHz); with a thickness of 3.0 mm, the effective absorption bandwidth is 10.42 GHz (7.58-18 GHz). With a thickness of 2.5 mm, the minimum reflection loss is -30.0 dB, and the effective absorption bandwidth is 8.53 GHz (9.4-18 GHz), which can effectively cover the X and Ku bands of radar. With a thickness of 2.0 mm, the effective absorption bandwidth is still 5.77 GHz (12.23-18 GHz).

[0051] The test results of the microwave absorption performance of FeSi / SiC@C 3-1 composite fiber material can be found in [link to relevant documentation]. Figure 8 The composite material samples exhibited reflection loss values ​​below -5dB across the 3.76–18GHz range at a thickness of 5.5mm. The effective absorption bandwidth was 13.71 GHz (4.29–18GHz) at 5.0mm thickness, 13.23 GHz (4.77–18GHz) at 4.5mm thickness, 12.47 GHz (5.53–18GHz) at 4.0mm thickness, 11.52 GHz (6.48–18GHz) at 3.5mm thickness, and 10.00 GHz (8.00–18GHz) at 3.0mm thickness, with a minimum reflection loss of -40.1dB. The effective absorption bandwidth was 8.00 GHz (10.00–18GHz) at 2.5mm thickness, and the thinnest sample at 2.0mm thickness still maintained an effective absorption bandwidth of 5.00 GHz (13–18GHz).

[0052] In summary, the FeSi / SiC@C carbon fiber composite material synthesized by the method of this invention not only exhibits excellent oxidation resistance at 800℃, but also demonstrates superior performance in electromagnetic wave absorption applications. The preparation method is simple and can be directly combined with metal parts for electrostatic coating (applicable to different surface structures), possessing considerable industrial application value. Furthermore, it can be used directly or indirectly as a coating and device for electromagnetic wave absorption.

[0053] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.

Claims

1. A beaded FeSi / SiC@C high-temperature resistant carbon fiber microwave absorbing composite material, characterized in that: The composite material has a 3D network structure with spherical FeSi and nano-SiC as the core layer and polyacrylonitrile as the shell layer.

2. The beaded FeSi / SiC@C high-temperature resistant carbon fiber microwave absorbing composite material according to claim 1, characterized in that: The length and shell thickness of beaded composite carbon fibers can be controlled by adjusting the ratio of FeSi and SiC core layers and the ratio of shell to core layer.

3. A method for preparing a beaded FeSi / SiC@C high-temperature resistant carbon fiber microwave absorbing composite material, characterized in that: Includes the following steps: Step 1: Spherical FeSi, nano-worm-like SiC and polyacrylonitrile are dissolved in N,N-dimethylformamide, heated and stirred until uniform, so that FeSi and SiC are uniformly dispersed in DMF to form a stable suspension slurry, and slurry A is obtained; Step 2: Dissolve PAN separately in DMF, heat and stir until homogeneous to obtain slurry B; Step 3: Coaxial electrospinning of slurry A and slurry B, with slurry A as the core layer and slurry B as the shell layer, and drying to remove bound water and volatiles to obtain the precursor. Step 4: Pre-oxidize the precursor by heating it to 200℃~250℃ at a rate of 1℃ / min; Step 5: Then, using argon as a protective gas, the temperature is increased at 3℃ / min. First, the temperature is increased to 380~420℃ and held for 40~80min, and then the temperature is increased to 750℃~850℃ and held for 40~80min. Finally, FeSi / SiC@C composite fiber material is obtained.

4. The preparation method of the beaded FeSi / SiC@C high-temperature resistant carbon fiber microwave absorbing composite material according to claim 3, characterized in that: In step 1, the mass ratio of spherical FeSi, nano-worm-like SiC, and polyacrylonitrile is 1:1:

4.

5. The preparation method of the beaded FeSi / SiC@C high-temperature resistant carbon fiber microwave absorbing composite material according to claim 3, characterized in that: The mass ratio of Fe / Si in FeSi and SiC is 1~3:

1.

6. The method for preparing a beaded FeSi / SiC@C high-temperature resistant carbon fiber microwave absorbing composite material according to claim 3, characterized in that: The amount of polyacrylonitrile in slurry A and slurry B is the same.

7. The preparation method of the beaded FeSi / SiC@C high-temperature resistant carbon fiber microwave absorbing composite material according to claim 3, characterized in that: The specific operation of coaxial electrospinning in step 3 is as follows: take slurry A and slurry B into two syringes respectively, and use inner 25G and outer 13G coaxial needles to perform coaxial electrospinning at speeds of 0.03 μL / min and 0.04 μL / min respectively. The air humidity is 33.9%, the temperature is 21℃, and a roller filled with oil paper is used as the receiver. The receiver rotation speed is 140 rpm and the voltage is 20 kV.

8. The preparation method of the beaded FeSi / SiC@C high-temperature resistant carbon fiber microwave absorbing composite material according to claim 3, characterized in that: The pre-oxidation temperature in step 4 is 225℃~240℃.

9. The preparation method of the beaded FeSi / SiC@C high-temperature resistant carbon fiber microwave absorbing composite material according to claim 3, characterized in that: In step 5, the temperature is first raised to 400℃ and held for 60 minutes, and then raised to 800℃ and held for 60 minutes.

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