Non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber and its preparation method

Abstract

This invention relates to a non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber and its preparation method. The technical solution is as follows: fumaric acid is added to deionized water, ultrasonically dispersed, and stirred to obtain solution A; an iron salt is added to deionized water and stirred to obtain solution B. Solutions A and B are mixed to obtain solution C; solution C is subjected to a hydrothermal reaction to obtain MIL-88A template powder. A metal salt is added to N,N-dimethylformamide, stirred, and filtered to obtain a mixed solution; the MIL-88A template powder is added to the mixed solution and stirred to obtain solution D. Polyvinyl alcohol is added to solution D, heated and stirred to obtain solution E. Solution E is electrospun, and the precursor fibers are collected using a collecting roller. The precursor fibers are subjected to thermal oxidation stabilization and carbothermal reduction reactions in an oven to obtain the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber. The product manufactured by this invention has the characteristics of strong versatility, excellent performance, high efficiency in absorbing electromagnetic waves, and a wide absorption frequency band.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorber technology. Specifically, it relates to a non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber and its preparation method. Background Technology

[0002] To address the increasingly serious problem of electromagnetic pollution, the research on electromagnetic wave absorbers has become a major focus in the field of materials science. Metal-organic frameworks (MOFs) are considered ideal precursors for preparing carbon-based microwave absorbing materials due to their large specific surface area, porosity, unique mesoscopic morphology, and designable chemical composition. The use of MOFs to construct multiple heterogeneous interfaces can effectively induce the synergistic effects of various polarization mechanisms, thereby significantly enhancing polarization loss, which has attracted the attention of those skilled in the art.

[0003] Autocatalytic pyrolysis can introduce carbon layers onto the surface of MOFs, thereby forming multiple heterogeneous interfaces. Reference 1 (Zhang X, Tian X, Qiao J, et al. In-Situ Fabrication of Sustainable-N-Doped-Carbon-Nanotube-Encapsulated CoNi Heterogenous Nanocomposites for High-Efficiency Electromagnetic Wave Absorption[J]. Small, 2023, 19(40): 2302686) discloses a simple strategy for introducing MWCNTs into CoNi-MOFs using autocatalytic pyrolysis. The synthesized CoNi@CNTs composite material achieved a maximum absorption bandwidth of 4.3 GHz at a thickness of 2.2 mm. However, this method is overly dependent on the catalytic properties of the central metal in the MOF. Only specific metals possess good catalytic activity, which limits the types of MOF materials that can be used with this method.

[0004] Ion exchange can introduce other metallic phases into MOFs and is a typical method for constructing heterostructures. Reference II (Huang L, Chen C, Huang X, et al. Enhanced electromagnetic absorbing performance of MOF-derived Ni / NiO / Cu@C composites[J]. Composites Part B: Engineering, 2019, 164: 583-589) discloses a method using Mn... 2+A method for etching Co-MOF-74 to form roughened CoMn-MOF-74 nanorods was developed. The resulting Co@C@MnO nanorods, obtained after pyrolysis, exhibited a minimum reflection loss of -64.4 GHz at 13.5 GHz. However, ion exchange processes are typically conducted under strong acidic or alkaline conditions, which can disrupt the morphology of the MOF, thereby undermining the high specific surface area characteristic of the MOF-derived microwave absorbing material and reducing its impedance matching with air and microwave attenuation capability.

[0005] Research on MOF-on-MOF heterostructure microwave absorbing materials based on the assembly of two or more different MOFs is gradually emerging. Different central metal ions in MOF-on-MOF heterostructure microwave absorbing materials can be thermally converted into different metal, metal carbide and metal oxide components, thereby further constructing rich heterostructure interfaces in the absorber. Reference III (Zhu H, Jiao Q, Fu RR, et al. Cu / NC@Co / NC composites derived from core-shell Cu-MOF@Co-MOF and their electromagnetic wave absorption properties[J]. Journal of Colloid and Interface Science, 2022, 613: 182-193) discloses a method for constructing a core-shell Cu-MOF@Co-MOF structure by independently assembling Cu-MOF and Co-MOF. The Cu / NC@Co / NC composite material obtained after thermal decomposition has a minimum reflection loss of -54.13dB@9.84GHz and an effective absorption bandwidth of 5.19GHz@2.5mm. However, due to the difficulty in matching the lattice parameters of different MOFs, the assembly between MOFs is quite challenging, resulting in a low success rate in the fabrication of MOF-on-MOF heterostructure microwave absorbing materials, making large-scale production difficult.

[0006] In summary, the shortcomings of existing technologies are: complex operation, difficulty in controlling the morphology of absorbers, poor versatility, low success rate in constructing multi-heteromeric interface microwave absorbing materials, and difficulty in achieving effective absorption of electromagnetic waves. Summary of the Invention

[0007] The present invention aims to overcome the shortcomings of the prior art and proposes a method for preparing a non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber with simple operation and controllable absorber morphology. The non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber prepared by this method has strong versatility, excellent performance, high efficiency in absorbing electromagnetic waves, strong reflection loss, and wide absorption frequency band.

[0008] To achieve the above objectives, the specific steps of the technical solution adopted by the present invention are as follows:

[0009] Step 1: Add fumaric acid to deionized water at a solid-liquid ratio of 70-100 g / L, sonicate for 5-20 minutes, and stir for 10-40 minutes to obtain solution A; add iron salt to deionized water at a solid-liquid ratio of 100-160 g / L, and stir for 5-20 minutes to obtain solution B.

[0010] Step 2: Mix solution A and solution B at a volume ratio of (4-7):1, stir for 10-40 minutes to obtain solution C; then subject solution C to a hydrothermal reaction; separate the solid and liquid, wash, and dry to obtain MIL-88A template powder.

[0011] Step 3: Add the metal salt to N,N-dimethylformamide at a solid-liquid ratio of 100-160 g / L, stir for 5-10 minutes, filter, and obtain a mixed solution; then add the MIL-88A template powder to the mixed solution at a solid-liquid ratio of 180-240 g / L, stir for 30-60 minutes, and obtain solution D.

[0012] Step 4: Add polyvinyl alcohol to solution D at a solid-liquid ratio of 125-170 g / L, heat and stir for 12-18 hours to obtain solution E.

[0013] Step 5: Electrospin the solution E with a spinning voltage of 15-21 kV and a syringe advance speed of 1.0-1.6 mL / min. Collect the precursor fibers with a collection roller at a distance of 12-20 cm.

[0014] Step 6: The collected precursor fibers are thermally oxidized and stabilized in an oven, and then carbothermic reduction reaction is carried out at 600-900℃ to obtain non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber.

[0015] The iron salt is one of ferric chloride, ferric nitrate, and ferric sulfate.

[0016] The hydrothermal reaction temperature is 80–130°C, and the hydrothermal reaction time is 6–12 hours.

[0017] The average particle size of the MIL-88A template powder is 1.8–2.9 μm.

[0018] The metal salt is one of molybdenum acetylacetonate, manganese acetylacetonate, copper acetylacetonate, and zirconium acetylacetonate.

[0019] The heating and stirring mentioned refers to heating from room temperature to 50-80°C.

[0020] The temperature for thermal oxidation stabilization is 200–300℃, and the holding time for thermal oxidation stabilization is 0.5–2 hours.

[0021] The heating rate of the carbothermic reduction reaction is 5–10 °C / min, and the holding time is 2–5 hours.

[0022] The stirring speed in step 1 is 300-600 rpm; the stirring speeds in steps 2, 3 and 4 are the same as those in step 1.

[0023] Due to the adoption of the above-described preparation method, the present invention has the following advantages compared with the prior art:

[0024] 1) This invention uses a hydrothermal reaction of iron salts and fumaric acid to form MIL-88A template powder, which is then added to an N,N-dimethylformamide solution containing metal salts and polyvinyl alcohol. Precursor fibers are obtained through electrospinning. Then, a non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber with controllable morphology is prepared through thermal oxidation and carbothermal reduction. The preparation process of this invention is simple, and the carbon fibers obtained by electrospinning are excellent carriers for achieving multiple heterogeneous interfaces.

[0025] 2) This invention uses fumaric acid as an organic ligand and iron as the central metal. A hydrothermal reaction is employed to bond the ligand and metal ions through coordination bonds, forming MIL-88A template powder. Electrospinning is then used to composite the MIL-88A template powder and discrete phase metal salt with one-dimensional carbon nanofibers to prepare a non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber. The high carbothermal temperature used in this invention promotes the graphitization of the carbon matrix and enhances the crystallinity of the metal carbides, resulting in effective absorption of electromagnetic waves by the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber at different carbothermal temperatures.

[0026] 3) This invention proposes a strategy for compositing MOFs and non-magnetic metals with one-dimensional carbon fibers. This method integrates the advantages of multiple materials, achieving synergistic effects in chemical composition and structure. The prepared non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber contains multiple phases, enhancing interfacial polarization loss. Simultaneously, the magnetoelectric synergy of multiple materials optimizes the impedance matching of the product. Testing showed that with a matching thickness of 2.12 mm, the optimal reflection loss was -66.02 dB; and with a matching thickness of 1.5 mm, the effective bandwidth reached 4.57 GHz.

[0027] 4) This invention is based on electrospinning, which involves blending MIL-88A template powder and non-magnetic metal salts with polyvinyl alcohol (PVA) to achieve a composite of MIL-88A powder, non-magnetic metals, and one-dimensional carbon fibers. First, the Fe3C generated from the pyrolysis of MIL-88A powder contributes magnetic loss capability, while nitrogen-doped carbon fibers exhibit high dielectric loss capability. Second, the addition of non-magnetic metals creates numerous heterogeneous interfaces, effectively enhancing interfacial polarization loss. Third, the magnetoelectric synergy produces excellent microwave attenuation capability and good impedance matching, resulting in highly efficient electromagnetic wave absorption performance for the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber.

[0028] Therefore, the present invention is easy to operate and the morphology of the absorbent is controllable. The non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber prepared has the characteristics of strong versatility, excellent performance, high efficiency in absorbing electromagnetic waves, strong reflection loss and wide absorption frequency band. Attached Figure Description

[0029] Figure 1 This is a scanning electron microscope image of a precursor fiber and a non-magnetic metal-doped Fe3C / carbon fiber prepared according to the present invention.

[0030] Figure 2 For use Figure 1 TEM image of non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber prepared from precursor fibers;

[0031] Figure 3 for Figure 2 The X-ray diffraction pattern of the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber is shown.

[0032] Figure 4 for Figure 2 The diagram shows the reflection loss of the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of protection of the present invention.

[0034] A non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber and its preparation method. The preparation method described in this specific embodiment includes the following steps:

[0035] Step 1: Add fumaric acid to deionized water at a solid-liquid ratio of 70-100 g / L, sonicate for 5-20 minutes, and stir for 10-40 minutes to obtain solution A; add iron salt to deionized water at a solid-liquid ratio of 100-160 g / L, and stir for 5-20 minutes to obtain solution B.

[0036] Step 2: Mix solution A and solution B at a volume ratio of (4-7):1, stir for 10-40 minutes to obtain solution C; then subject solution C to a hydrothermal reaction; separate the solid and liquid, wash, and dry to obtain MIL-88A template powder.

[0037] Step 3: Add the metal salt to N,N-dimethylformamide at a solid-liquid ratio of 100-160 g / L, stir for 5-10 minutes, filter, and obtain a mixed solution; then add the MIL-88A template powder to the mixed solution at a solid-liquid ratio of 180-240 g / L, stir for 30-60 minutes, and obtain solution D.

[0038] Step 4: Add polyvinyl alcohol to solution D at a solid-liquid ratio of 125-170 g / L, heat and stir for 12-18 hours to obtain solution E.

[0039] Step 5: Electrospin the solution E with a spinning voltage of 15-21 kV and a syringe advance speed of 1.0-1.6 mL / min. Collect the precursor fibers with a collection roller at a distance of 12-20 cm.

[0040] Step 6: The collected precursor fibers are thermally oxidized and stabilized in an oven, and then carbothermic reduction reaction is carried out at 600-900℃ to obtain non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber.

[0041] The iron salt is one of ferric chloride, ferric nitrate, and ferric sulfate.

[0042] The hydrothermal reaction temperature is 80–130°C, and the hydrothermal reaction time is 6–12 hours.

[0043] The metal salt is one of molybdenum acetylacetonate, manganese acetylacetonate, copper acetylacetonate, and zirconium acetylacetonate.

[0044] The heating and stirring mentioned refers to heating from room temperature to 50-80°C.

[0045] The temperature for thermal oxidation stabilization is 200–300℃, and the holding time for thermal oxidation stabilization is 0.5–2 hours.

[0046] The heating rate of the carbothermic reduction reaction is 5–10 °C / min, and the holding time is 2–5 hours.

[0047] The stirring speed in step 1 is 300-600 rpm.

[0048] In this specific embodiment:

[0049] The average particle size of the MIL-88A template powder is 1.8–2.9 μm.

[0050] The stirring speed in steps 2, 3 and 4 is the same as the stirring speed in step 1.

[0051] The details will not be repeated in the examples.

[0052] Example 1

[0053] A non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0054] Step 1: Add fumaric acid to deionized water at a solid-liquid ratio of 70 g / L, sonicate for 5 minutes, and stir for 10 minutes to obtain solution A; add iron salt to deionized water at a solid-liquid ratio of 100 g / L, and stir for 5 minutes to obtain solution B.

[0055] Step 2: Mix solution A and solution B at a volume ratio of 4:1 and stir for 10 minutes to obtain solution C; then subject solution C to a hydrothermal reaction; separate the solid and liquid, wash, and dry to obtain MIL-88A template powder.

[0056] Step 3: Add the metal salt to N,N-dimethylformamide at a solid-liquid ratio of 100 g / L, stir for 5 minutes, filter, and obtain a mixed solution; then add the MIL-88A template powder to the mixed solution at a solid-liquid ratio of 180 g / L, stir for 30 minutes, and obtain solution D.

[0057] Step 4: Add polyvinyl alcohol to solution D at a solid-liquid ratio of 125 g / L, heat and stir for 12 hours to obtain solution E.

[0058] Step 5: Electrospin the solution E with a spinning voltage of 15kV and a syringe advance speed of 1.0mL / min. Collect the precursor fibers with a collection roller at 12cm.

[0059] Step 6: The collected precursor fibers are thermally oxidized and stabilized in an oven, and then carbothermic reduction reaction is carried out at 900℃ to obtain non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber.

[0060] The iron salt mentioned is ferric nitrate.

[0061] The hydrothermal reaction was carried out at a temperature of 110°C for 6 hours.

[0062] The metal salt mentioned is molybdenum acetylacetonate.

[0063] The heating and stirring temperature is 50°C.

[0064] The temperature at which thermal oxidation is stabilized is 230℃, and the holding time is 0.5h.

[0065] The heating rate of the carbothermic reduction reaction is 5℃ / min, and the holding time is 2h.

[0066] The stirring speed is 400 rpm.

[0067] Example 2

[0068] A non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0069] Step 1: Add fumaric acid to deionized water at a solid-liquid ratio of 80 g / L, sonicate for 10 minutes, and stir for 20 minutes to obtain solution A; add iron salt to deionized water at a solid-liquid ratio of 120 g / L, and stir for 10 minutes to obtain solution B.

[0070] Step 2: Mix solution A and solution B at a volume ratio of 5:1 and stir for 20 minutes to obtain solution C; then subject solution C to a hydrothermal reaction; separate the solid and liquid, wash, and dry to obtain MIL-88A template powder.

[0071] Step 3: Add the metal salt to N,N-dimethylformamide at a solid-liquid ratio of 120 g / L, stir for 7 minutes, filter, and obtain a mixed solution; then add the MIL-88A template powder to the mixed solution at a solid-liquid ratio of 200 g / L, stir for 40 minutes, and obtain solution D.

[0072] Step 4: Add polyvinyl alcohol to solution D at a solid-liquid ratio of 140 g / L, heat and stir for 14 hours to obtain solution E.

[0073] Step 5: Electrospin the solution E with a spinning voltage of 17kV and a syringe advance speed of 1.2mL / min. Collect the precursor fibers with a collection roller at 15cm.

[0074] Step 6: The collected precursor fibers are thermally oxidized and stabilized in an oven, and then carbothermic reduction reaction is carried out at 800℃ to obtain non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber.

[0075] The iron salt mentioned is ferric chloride.

[0076] The hydrothermal reaction was carried out at a temperature of 130°C for 8 hours.

[0077] The metal salt mentioned is manganese acetylacetone.

[0078] The heating and stirring temperature is 60°C.

[0079] The temperature at which thermal oxidation is stabilized is 260℃, and the holding time is 1 hour.

[0080] The heating rate of the carbothermic reduction reaction is 6℃ / min, and the holding time is 3h.

[0081] The stirring speed is 500 rpm.

[0082] Example 3

[0083] A non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0084] Step 1: Add fumaric acid to deionized water at a solid-liquid ratio of 90 g / L, sonicate for 15 minutes, and stir for 30 minutes to obtain solution A; add iron salt to deionized water at a solid-liquid ratio of 140 g / L, and stir for 15 minutes to obtain solution B.

[0085] Step 2: Mix solution A and solution B at a volume ratio of 6:1, stir for 30 minutes to obtain solution C; then subject solution C to a hydrothermal reaction; separate the solid and liquid, wash, and dry to obtain MIL-88A template powder.

[0086] Step 3: Add the metal salt to N,N-dimethylformamide at a solid-liquid ratio of 140 g / L, stir for 8 minutes, filter, and obtain a mixed solution; then add the MIL-88A template powder to the mixed solution at a solid-liquid ratio of 220 g / L, stir for 50 minutes, and obtain solution D.

[0087] Step 4: Add polyvinyl alcohol to solution D at a solid-liquid ratio of 155 g / L, heat and stir for 16 hours to obtain solution E.

[0088] Step 5: Electrospin the solution E with a spinning voltage of 19kV and a syringe advance speed of 1.4mL / min. Collect the precursor fibers with a collection roller at 17cm.

[0089] Step 6: The collected precursor fibers are thermally oxidized and stabilized in an oven, and then carbothermic reduction reaction is carried out at 700℃ to obtain non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber.

[0090] The iron salt mentioned is ferric sulfate.

[0091] The hydrothermal reaction was carried out at a temperature of 80°C for 10 hours.

[0092] The metal salt mentioned is copper acetylacetonate.

[0093] The heating and stirring temperature is 70°C.

[0094] The temperature for thermal oxidation stabilization is 200℃, and the holding time is 1.5h.

[0095] The heating rate of the carbothermic reduction reaction is 8℃ / min, and the holding time is 4h.

[0096] The stirring speed is 300 rpm.

[0097] Example 4

[0098] A non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber and its preparation method. The steps of the preparation method described in this embodiment are as follows:

[0099] Step 1: Add fumaric acid to deionized water at a solid-liquid ratio of 100 g / L, sonicate for 20 minutes, and stir for 40 minutes to obtain solution A; add iron salt to deionized water at a solid-liquid ratio of 160 g / L, and stir for 20 minutes to obtain solution B.

[0100] Step 2: Mix solution A and solution B at a volume ratio of 7:1 and stir for 40 minutes to obtain solution C; then subject solution C to a hydrothermal reaction; separate the solid and liquid, wash, and dry to obtain MIL-88A template powder.

[0101] Step 3: Add the metal salt to N,N-dimethylformamide at a solid-liquid ratio of 160 g / L, stir for 10 minutes, filter, and obtain a mixed solution; then add the MIL-88A template powder to the mixed solution at a solid-liquid ratio of 240 g / L, stir for 60 minutes, and obtain solution D.

[0102] Step 4: Add polyvinyl alcohol to solution D at a solid-liquid ratio of 170 g / L, heat and stir for 18 hours to obtain solution E.

[0103] Step 5: Electrospin the solution E with a spinning voltage of 21kV and a syringe advance speed of 1.6mL / min. Collect the precursor fibers with a collection roller at a distance of 20cm.

[0104] Step 6: The collected precursor fibers are thermally oxidized and stabilized in an oven, and then carbothermic reduction reaction is carried out at 900℃ to obtain non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber.

[0105] The iron salt mentioned is ferric nitrate.

[0106] The hydrothermal reaction was carried out at a temperature of 95°C for 12 hours.

[0107] The metal salt mentioned is zirconium acetylacetonate.

[0108] The heating and stirring temperature is 80℃.

[0109] The temperature at which thermal oxidation is stabilized is 300℃, and the holding time is 2 hours.

[0110] The heating rate of the carbothermic reduction reaction is 10℃ / min, and the holding time is 5h.

[0111] The stirring speed is 600 rpm.

[0112] Compared with existing technologies, this specific embodiment has the following advantages:

[0113] 1) In this specific embodiment, iron salt and fumaric acid are reacted hydrothermally to form MIL-88A template powder, which is then added to an N,N-dimethylformamide solution containing metal salt and polyvinyl alcohol. Precursor fibers are obtained by electrospinning. Then, non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber with controllable morphology is prepared through thermal oxidation and carbothermal reduction. The preparation process of this specific embodiment is simple, and the carbon fibers obtained by electrospinning are excellent carriers for realizing multiple heterogeneous interfaces.

[0114] 2) In this specific embodiment, fumaric acid is used as the organic ligand and iron as the central metal. A hydrothermal reaction is employed to allow the ligand and metal ions to combine through coordination bonds, forming MIL-88A template powder. Electrospinning is then used to composite the MIL-88A template powder and discrete phase metal salt with one-dimensional carbon nanofibers to prepare a non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber. The high carbothermal temperature used in this specific embodiment promotes the graphitization of the carbon matrix and enhances the crystallinity of the metal carbides, resulting in effective absorption of electromagnetic waves by the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber at different carbothermal temperatures.

[0115] 3) This specific embodiment proposes a strategy of compositing MOFs and non-magnetic metals with one-dimensional carbon fibers. This method integrates the advantages of multiple materials, achieving synergistic effects in chemical composition and structure. The prepared non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber contains multiple phases, enhancing interfacial polarization loss. Simultaneously, the magnetoelectric synergy of multiple materials optimizes the impedance matching of the sample. Testing showed that with a matching thickness of 2.12 mm, the optimal reflection loss was -66.02 dB; and with a matching thickness of 1.5 mm, the effective bandwidth reached 4.57 GHz.

[0116] 4) This specific embodiment is based on electrospinning, where MIL-88A template powder and non-magnetic metal salt are blended with polyvinyl alcohol to achieve a composite of MIL-88A powder, non-magnetic metal, and one-dimensional carbon fiber. First, the Fe3C generated by the pyrolysis of MIL-88A powder brings magnetic loss capability, while nitrogen-doped carbon fiber has high dielectric loss capability; second, the addition of non-magnetic metal brings a large number of heterogeneous interfaces, effectively enhancing interfacial polarization loss; third, due to the magnetoelectric synergy, excellent microwave attenuation capability and good impedance matching are generated, and the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber achieves highly efficient electromagnetic wave absorption performance.

[0117] The MIL-88A / Mo / PAN precursor fiber and Fe3C / Mo2C / NCFs electromagnetic wave absorber prepared in this specific embodiment are shown in the attached figure. Figure 1 The images shown are scanning electron microscope (SEM) images of the precursor fibers and non-magnetic metal-doped Fe3C / carbon fibers prepared in Example 1. Figure 1 (a) is a scanning electron microscope image of the prepared precursor fibers. Figure 1 (b) The prepared non-magnetic metal-doped Fe3C / carbon fiber; Figure 2 For use Figure 1 TEM image of non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber prepared from precursor fibers; Figure 3 for Figure 2 The X-ray diffraction pattern of the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber is shown. Figure 4 for Figure 2 The diagram shows the reflection loss of non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber in the frequency range of 2-18 GHz and with a thickness of 1-3 mm.

[0118] from Figure 1 (a) It can be seen that MIL-88A template powder has been successfully incorporated into carbon fibers via electrospinning; from Figure 1 As can be seen in (b), the MIL-88A template powder can still maintain its original morphology through high-temperature carbotherm treatment of the precursor fiber. Figure 2 As can be seen, the abundant crystalline metal compound particles within the carbon fibers of the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber reflect the heterogeneous interface between the rich metal compound particles and carbon within the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber. Figure 3 The peaks of iron and iron carbides, as well as the characteristic peak of Mo2C at 39.58°, indicate the presence of abundant phases within the sample. From... Figure 4It can be seen that the prepared Fe3C / carbon fiber electromagnetic wave absorber doped with non-magnetic metal achieved the best reflection loss of -66.02dB when the matching thickness was 2.12mm, and the effective bandwidth reached 4.57GHz (13.43~18GHz) when the matching thickness was 1.5mm.

[0119] Therefore, this specific embodiment is easy to operate and the morphology of the absorbent is controllable. The prepared non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber has the characteristics of strong versatility, excellent performance, high efficiency in absorbing electromagnetic waves, strong reflection loss and wide absorption frequency band.

Claims

1. A method for preparing a non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber, characterized in that, The steps of the preparation method are as follows: Step 1: Add fumaric acid to deionized water at a solid-liquid ratio of 70-100 g / L, sonicate for 5-20 minutes, and stir for 10-40 minutes to obtain solution A; add iron salt to deionized water at a solid-liquid ratio of 100-160 g / L, and stir for 5-20 minutes to obtain solution B. Step 2: Mix solution A and solution B at a volume ratio of (4-7):1, stir for 10-40 minutes to obtain solution C; then subject solution C to a hydrothermal reaction; separate solid and liquid, wash, and dry to obtain MIL-88A template powder; The average particle size of the MIL-88A template powder is 1.8–2.9 μm; Step 3: Add the metal salt to N,N-dimethylformamide at a solid-liquid ratio of 100-160 g / L, stir for 5-10 minutes, filter, and obtain a mixed solution; then add the MIL-88A template powder to the mixed solution at a solid-liquid ratio of 180-240 g / L, stir for 30-60 minutes, and obtain solution D; Step 4: Add polyvinyl alcohol to solution D at a solid-liquid ratio of 125-170 g / L, heat and stir for 12-18 hours to obtain solution E; Step 5: Electrospin the solution E with a spinning voltage of 15-21 kV and a syringe advance speed of 1.0-1.6 mL / min. Collect the precursor fibers with a collection roller at a distance of 12-20 cm. Step 6: The collected precursor fibers are thermally oxidized and stabilized in an oven, and then carbothermic reduction reaction is carried out at 600~900℃ to obtain non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber.

2. The method for preparing the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber according to claim 1, characterized in that, The iron salt is one of ferric chloride, ferric nitrate, and ferric sulfate.

3. The method for preparing the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber according to claim 1, characterized in that, The hydrothermal reaction temperature is 80–130°C, and the hydrothermal reaction time is 6–12 hours.

4. The method for preparing the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber according to claim 1, characterized in that, The metal salt is one of molybdenum acetylacetonate, copper acetylacetonate, and zirconium acetylacetonate.

5. The method for preparing the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber according to claim 1, characterized in that, The heating and stirring mentioned refers to heating from room temperature to 50~80℃.

6. The method for preparing the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber according to claim 1, characterized in that, The temperature for thermal oxidation stabilization is 200–300℃, and the holding time for thermal oxidation stabilization is 0.5–2 hours.

7. The method for preparing the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber according to claim 1, characterized in that, The heating rate of the carbothermic reduction reaction is 5–10 °C / min, and the holding time is 2–5 hours.

8. The method for preparing the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber according to claim 1, characterized in that, The stirring speed in step 1 is 300-600 rpm; the stirring speeds in steps 2, 3 and 4 are the same as those in step 1.

9. A non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber, characterized in that... The non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber is prepared by the preparation method of the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber according to any one of claims 1 to 8.

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