Nonmagnetic metal doped Fe3C / carbon fiber electromagnetic wave absorbent and preparation method thereof

Abstract

The invention relates to a non-magnetic metal doped Fe3C / carbon fiber electromagnetic wave absorbent and a preparation method thereof. According to the technical scheme, fumaric acid is added into deionized water, ultrasonic dispersion and stirring are conducted, and a solution A is obtained; adding ferric salt into deionized water, and stirring to obtain a solution B; mixing the solution A and the solution B to obtain a solution C; the solution C is subjected to a hydrothermal reaction, and MIL-88A template powder is obtained. The preparation method comprises the following steps: adding metal salt into N, N-dimethylformamide, stirring, and carrying out suction filtration to obtain a mixed solution; adding MIL-88A template powder into the mixed solution, and stirring to obtain a solution D; adding polyvinyl alcohol into the solution D, heating and stirring to obtain a solution E; and carrying out electrostatic spinning on the solution E, and collecting precursor fibers by using a collecting roller. And performing thermal oxidation stabilization and carbon thermal reduction reaction on the precursor fiber in a drying oven to prepare the nonmagnetic metal doped Fe3C / carbon fiber electromagnetic wave absorbent. The product prepared by the invention has the characteristics of high universality, excellent performance, capability of efficiently absorbing electromagnetic waves and wide wave-absorbing frequency band.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic wave absorbers, and specifically relates to a non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber and a preparation method thereof. Background Art

[0002] In order to solve the increasingly serious electromagnetic pollution problem, the research on electromagnetic wave absorbers has become a hot topic in the current materials field. Metal organic frameworks (MOFs) are considered to be 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 multi-heterogeneous interfaces can effectively induce the synergistic effect of multiple polarization mechanisms, thereby significantly enhancing polarization losses, which has attracted the attention of technicians in this field.

[0003] The autocatalytic pyrolysis method can introduce a carbon layer on the surface of MOF, thereby forming multiple heterogeneous interfaces. Document 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-MOF using autocatalytic pyrolysis. The synthesized CoNi@CNTs composite material obtained 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 MOF. Only specific metals have good catalytic ability, which limits the types of MOF materials that can be used in this method.

[0004] The ion exchange strategy can introduce other metal phases into MOF, which is also a typical method for constructing heterogeneous interfaces. 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 of introducing Mn 2+The method of etching Co-MOF-74 and forming CoMn-MOF-74 nanorods with rough surfaces, the Co@C@MnO nanorods obtained after pyrolysis have a minimum reflection loss of -64.4GHz at 13.5GHz. However, the ion exchange process is generally carried out under strong acidic or alkaline conditions, which will destroy the morphology of MOF, resulting in the destruction of the high specific surface area characteristics of MOF-derived microwave absorbing materials themselves, reducing their impedance matching with air and microwave attenuation capabilities.

[0005] Research on MOF-on-MOF heterostructure microwave absorbers formed by assembling two or more different MOFs has gradually emerged. Different central metal ions in MOF-on-MOF heterostructure microwave absorbers can be thermally converted into different metal, metal carbide and metal oxide components, thereby further constructing rich heterogeneous 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 independently assembling Cu-MOF and Co-MOF to construct a core-shell structure Cu-MOF@Co-MOF. The Cu / NC@Co / NC composite material obtained after thermal decomposition has a minimum reflection loss of -54.13 dB@9.84 GHz and an effective absorption bandwidth of 5.19 GHz@2.5 mm. However, since it is difficult to match the lattice parameters of different MOFs and the assembly between MOFs is difficult, the success rate of preparing MOF-on-MOF heterostructure microwave absorbing materials is low and it is difficult to produce them on a large scale.

[0006] In summary, the technical deficiencies of the prior art are: complex operation, difficulty in controlling the morphology of the absorbent, poor versatility, low success rate in constructing multi-heterogeneous 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 deficiencies of the prior art and aims to provide a method for preparing a non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber which is simple to operate and has controllable absorber morphology; the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber prepared by the method has strong versatility, excellent performance, can efficiently absorb electromagnetic waves, has strong reflection loss and a wide wave absorption frequency band.

[0008] To achieve the above purpose, 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 to 100 g / L, ultrasonically disperse for 5 to 20 minutes, and stir for 10 to 40 minutes to obtain solution A; add iron salt to deionized water at a solid-liquid ratio of 100 to 160 g / L, and stir for 5 to 20 minutes to obtain solution B.

[0010] Step 2, mixing the solution A and the solution B at a volume ratio of the solution A to the solution B of (4-7) to 1, stirring for 10-40 minutes to obtain a solution C; subjecting the solution C to a hydrothermal reaction; solid-liquid separation, washing, and drying to obtain a MIL-88A template powder.

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

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

[0013] Step 5: electrospinning the solution E at a spinning voltage of 15 to 21 kV and a syringe propulsion speed of 1.0 to 1.6 mL / min, and collecting the precursor fibers with a collecting roller at a distance of 12 to 20 cm.

[0014] Step 6: The collected precursor fibers are thermally oxidized and stabilized in an oven, and then subjected to a carbon thermal reduction reaction at 600-900° C. to obtain a 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 temperature of the hydrothermal reaction is 80-130° C., and the time of the hydrothermal reaction is 6-12 hours.

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

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

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

[0020] The thermal oxidation stabilization temperature is 200-300° C., and the thermal oxidation stabilization insulation time is 0.5-2 hours.

[0021] The heating rate of the carbon thermal reduction reaction is 5 to 10° C. / min, and the heat preservation time is 2 to 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 that in step 1.

[0023] Due to the adoption of the above-mentioned preparation scheme, the present invention has the following beneficial effects compared with the prior art:

[0024] 1) The present invention forms MIL-88A template powder by hydrothermal reaction of iron salt and fumaric acid, adds the powder to N,N-dimethylformamide solution containing metal salt and polyvinyl alcohol, and electrospins to obtain precursor fiber; then, non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber with controllable morphology is obtained by thermal oxidation and carbon thermal reduction. The preparation process of the present invention is simple to operate, and the carbon fiber obtained by electrospinning is a high-quality carrier for realizing multiple heterogeneous interfaces.

[0025] 2) The present invention uses fumaric acid as an organic ligand and iron as a central metal, and adopts a hydrothermal reaction to make the above ligand and metal ions mutually bonded through coordination bonds to form a MIL-88A template powder. The MIL-88A template powder and discrete phase metal salt are composited with one-dimensional carbon nanofibers by electrostatic spinning to obtain a non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber. The high carbon thermal temperature used in the present invention will promote the graphitization of the carbon matrix and enhance the crystallinity of the metal carbide, resulting in the effective absorption of electromagnetic waves by the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber at different carbon thermal temperatures.

[0026] 3) The present invention proposes a strategy to composite MOF and non-magnetic metals with one-dimensional carbon fibers. This method combines the advantages of multiple materials and achieves synergistic effects of chemical components and structures. The prepared non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber contains multiple phases, which enhances the interface polarization loss. At the same time, the magneto-electric synergy of multiple materials also optimizes the impedance matching of the product. After testing: when the matching thickness is 2.12mm, the optimal reflection loss is -66.02dB; when the matching thickness is 1.5mm, the effective bandwidth reaches 4.57GHz.

[0027] 4) Based on electrospinning, the present invention blends MIL-88A template powder and non-magnetic metal salt with polymer polyvinyl alcohol to achieve the composite of MIL-88A powder and non-magnetic metal with one-dimensional carbon fiber. First, Fe3C produced by pyrolysis of MIL-88A powder brings magnetic loss capacity, while nitrogen-doped carbon fiber has high dielectric loss capacity; secondly, the addition of non-magnetic metal brings a large number of heterogeneous interfaces, effectively enhancing interface polarization loss; thirdly, due to the excellent microwave attenuation capacity and good impedance matching produced by magneto-electric synergy, the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber obtains efficient electromagnetic wave absorption performance.

[0028] Therefore, the present invention 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, efficient absorption of electromagnetic waves, strong reflection loss and wide absorption frequency band. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The scanning electron microscope images of a precursor fiber and a non-magnetic metal-doped Fe3C / carbon fiber prepared by the present invention;

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

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

[0032] Figure 4 for Figure 2 The reflection loss diagram of the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber is shown. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with the accompanying drawings and specific implementations, but the protection scope of the present invention is not limited thereto.

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

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

[0036] Step 2, mixing the solution A and the solution B at a volume ratio of the solution A to the solution B of (4-7) to 1, stirring for 10-40 minutes to obtain a solution C; subjecting the solution C to a hydrothermal reaction; solid-liquid separation, washing, and drying to obtain a MIL-88A template powder.

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

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

[0039] Step 5: electrospinning the solution E at a spinning voltage of 15 to 21 kV and a syringe propulsion speed of 1.0 to 1.6 mL / min, and collecting the precursor fibers with a collecting roller at a distance of 12 to 20 cm.

[0040] Step 6: The collected precursor fibers are thermally oxidized and stabilized in an oven, and then subjected to a carbon thermal reduction reaction at 600-900° C. to obtain a 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 temperature of the hydrothermal reaction is 80-130° C., and the time of the hydrothermal reaction is 6-12 hours.

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

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

[0045] The thermal oxidation stabilization temperature is 200-300° C., and the thermal oxidation stabilization insulation time is 0.5-2 hours.

[0046] The heating rate of the carbon thermal reduction reaction is 5 to 10° C. / min, and the heat preservation time is 2 to 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 to 2.9 μm.

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

[0051] This will not be described in detail in the embodiments.

[0052] Example 1

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

[0054] Step 1: Add fumaric acid to deionized water at a solid-liquid ratio of 70 g / L, ultrasonically disperse 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, mixing the solution A and the solution B at a volume ratio of 4:1, stirring for 10 minutes to obtain a solution C; subjecting the solution C to a hydrothermal reaction; and performing solid-liquid separation, washing, and drying to obtain a 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, and filter to 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: electrospinning the solution E at a spinning voltage of 15 kV and a syringe propulsion speed of 1.0 mL / min, and collecting the precursor fibers with a collecting roller at a distance of 12 cm.

[0059] Step 6: The collected precursor fibers are thermally oxidized and stabilized in an oven, and then subjected to a carbon thermal reduction reaction at 900° C. to obtain a non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber.

[0060] The iron salt is ferric nitrate.

[0061] The temperature of the hydrothermal reaction is 110° C., and the time of the hydrothermal reaction is 6 hours.

[0062] The metal salt is molybdenum acetylacetonate.

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

[0064] The thermal oxidation stable temperature is 230° C., and the heat preservation time is 0.5 h.

[0065] The heating rate of the carbon thermal reduction reaction is 5°C / min, and the insulation 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 a preparation method thereof. The steps of the preparation method described in this embodiment are:

[0069] Step 1: Add fumaric acid to deionized water at a solid-liquid ratio of 80 g / L, ultrasonically disperse 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, mixing the solution A and the solution B at a volume ratio of 5:1, stirring for 20 minutes to obtain a solution C; subjecting the solution C to a hydrothermal reaction; solid-liquid separation, washing, and drying to obtain a 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, and filter to 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: electrospinning the solution E at a spinning voltage of 17 kV and a syringe propulsion speed of 1.2 mL / min, and collecting the precursor fibers with a collecting roller at a distance of 15 cm.

[0074] Step 6: The collected precursor fibers are thermally oxidized and stabilized in an oven, and then subjected to a carbon thermal reduction reaction at 800° C. to obtain a non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber.

[0075] The iron salt is ferric chloride.

[0076] The temperature of the hydrothermal reaction is 130° C., and the time of the hydrothermal reaction is 8 hours.

[0077] The metal salt is manganese acetylacetonate.

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

[0079] The thermal oxidation stable temperature is 260° C., and the heat preservation time is 1 hour.

[0080] The heating rate of the carbon thermal reduction reaction is 6°C / min, and the insulation 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 a preparation method thereof. The steps of the preparation method described in this embodiment are:

[0084] Step 1: Add fumaric acid to deionized water at a solid-liquid ratio of 90 g / L, ultrasonically disperse 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, mixing the solution A and the solution B at a volume ratio of 6:1, stirring for 30 minutes to obtain a solution C; subjecting the solution C to a hydrothermal reaction; solid-liquid separation, washing, and drying to obtain a 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, and filter to 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: electrospinning the solution E at a spinning voltage of 19 kV and a syringe propulsion speed of 1.4 mL / min, and collecting the precursor fibers with a collecting roller at a distance of 17 cm.

[0089] Step 6: The collected precursor fibers are thermally oxidized and stabilized in an oven, and then subjected to a carbon thermal reduction reaction at 700° C. to obtain a non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber.

[0090] The iron salt is ferric sulfate.

[0091] The temperature of the hydrothermal reaction is 80° C., and the time of the hydrothermal reaction is 10 h.

[0092] The metal salt is copper acetylacetonate.

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

[0094] The thermal oxidation stable temperature is 200° C. and the heat preservation time is 1.5 hours.

[0095] The heating rate of the carbon thermal reduction reaction is 8°C / min, and the insulation 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 a preparation method thereof. The steps of the preparation method described in this embodiment are:

[0099] Step 1: Add fumaric acid to deionized water at a solid-liquid ratio of 100 g / L, ultrasonically disperse 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, mixing the solution A and the solution B at a volume ratio of 7:1, stirring for 40 minutes to obtain a solution C; subjecting the solution C to a hydrothermal reaction; and performing solid-liquid separation, washing, and drying to obtain a 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, and filter to 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: electrospinning the solution E at a spinning voltage of 21 kV and a syringe propulsion speed of 1.6 mL / min, and collecting the precursor fibers with a collecting roller at a distance of 20 cm.

[0104] Step 6: The collected precursor fibers are thermally oxidized and stabilized in an oven, and then subjected to a carbon thermal reduction reaction at 900° C. to obtain a non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber.

[0105] The iron salt is ferric nitrate.

[0106] The temperature of the hydrothermal reaction is 95° C., and the time of the hydrothermal reaction is 12 h.

[0107] The metal salt is zirconium acetylacetonate.

[0108] The heating and stirring temperature is 80°C.

[0109] The thermal oxidation stabilization temperature is 300° C. and the heat preservation time is 2 hours.

[0110] The heating rate of the carbon thermal reduction reaction is 10°C / min, and the insulation time is 5h.

[0111] The stirring speed is 600 rpm.

[0112] Compared with the existing technology, this specific implementation has the following beneficial effects:

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

[0114] 2) This specific embodiment uses fumaric acid as an organic ligand and iron as a central metal, and uses a hydrothermal reaction to allow the above ligands and metal ions to bind to each other through coordination bonds to form a MIL-88A template powder. The MIL-88A template powder and discrete phase metal salts are composited with one-dimensional carbon nanofibers using electrospinning to obtain a non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber. This specific embodiment uses a high carbon thermal temperature to promote graphitization of the carbon matrix and enhance the crystallinity of the metal carbide, resulting in the effective absorption of electromagnetic waves by the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber at different carbon thermal temperatures.

[0115] 3) This specific implementation method proposes a strategy to composite MOF and non-magnetic metals with one-dimensional carbon fibers. This method combines the advantages of multiple materials and achieves synergistic effects of chemical components and structures. There are multiple phases in the prepared non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber, which enhances the interface polarization loss. At the same time, the magneto-electric synergy of multiple materials also optimizes the impedance matching of the sample. After testing: when the matching thickness is 2.12mm, the optimal reflection loss is -66.02dB; when the matching thickness is 1.5mm, the effective bandwidth reaches 4.57GHz.

[0116] 4) This specific implementation method is based on electrospinning, and the MIL-88A template powder and non-magnetic metal salt are blended with polymer polyvinyl alcohol to achieve the composite of MIL-88A powder and non-magnetic metal with one-dimensional carbon fiber. First, the Fe3C produced by the pyrolysis of MIL-88A powder brings magnetic loss capacity, while nitrogen-doped carbon fiber has high dielectric loss capacity; secondly, the addition of non-magnetic metal brings a large number of heterogeneous interfaces, which effectively enhances the interface polarization loss; thirdly, due to the excellent microwave attenuation capacity and good impedance matching produced by magnetoelectric synergy, the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber obtains 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 accompanying drawings. Figure 1 The scanning electron microscope images of the precursor fiber and the non-magnetic metal-doped Fe3C / carbon fiber prepared in Example 1 are shown in FIG. Figure 1 (a) is a scanning electron microscope image of the prepared precursor fiber. Figure 1 (b) is the prepared non-magnetic metal-doped Fe3C / carbon fiber; Figure 2 For use Figure 1 TEM image of the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber prepared from the precursor fiber shown; Figure 3 for Figure 2 The X-ray diffraction pattern of the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber shown; Figure 4 for Figure 2 The reflection loss diagram of the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber in the frequency range of 2-18GHz and a thickness of 1-3mm is shown.

[0118] from Figure 1 (a) It can be seen that the MIL-88A template powder has been successfully filled into carbon fibers by electrospinning; Figure 1 As can be seen in (b), the MIL-88A template powder can still maintain its original morphology through high-temperature carbon heating of the precursor fiber. Figure 2 It can be seen that a large number of crystalline metal compound particles are present inside the carbon fibers of the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber, reflecting the heterogeneous interface between the abundant metal compound particles and carbon inside the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber. Figure 3 It can be seen that the peaks of iron and iron carbide and the characteristic peak of Mo2C at 39.58° indicate that there are abundant phases inside the sample. Figure 4It can be seen that the prepared F non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber obtained an optimal 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, the specific implementation method 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, efficient absorption of 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: Step 1, adding fumaric acid to deionized water at a solid-liquid ratio of 70-100 g / L, ultrasonically dispersing for 5-20 minutes, stirring for 10-40 minutes, to obtain solution A; adding iron salt to deionized water at a solid-liquid ratio of 100-160 g / L, stirring for 5-20 minutes, to obtain solution B; Step 2, mixing the solution A and the solution B at a volume ratio of the solution A to the solution B of (4-7) to 1, stirring for 10-40 minutes to obtain a solution C; and subjecting the solution C to a hydrothermal reaction; Solid-liquid separation, washing, and drying to obtain MIL-88A template powder; Step 3, adding the metal salt to N,N-dimethylformamide at a solid-liquid ratio of 100 to 160 g / L, stirring for 5 to 10 minutes, and filtering to obtain a mixed solution; then adding the MIL-88A template powder to the mixed solution at a solid-liquid ratio of 180 to 240 g / L, stirring for 30 to 60 minutes, and obtaining a solution D; Step 4, adding polyvinyl alcohol to solution D at a solid-liquid ratio of 125 to 170 g / L, heating and stirring for 12 to 18 hours to obtain solution E; Step 5, electrospinning the solution E at a spinning voltage of 15 to 21 kV and a syringe propulsion speed of 1.0 to 1.6 mL / min, and collecting the precursor fibers with a collecting roller at a distance of 12 to 20 cm; Step 6: The collected precursor fibers are thermally oxidized and stabilized in an oven, and then subjected to a carbon thermal reduction reaction at 600-900° C. to obtain a 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 temperature of the hydrothermal reaction is 80-130° C., and the time of the hydrothermal reaction 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 average particle size of the MIL-88A template powder is 1.8 to 2.9 μm.

5. 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, manganese acetylacetonate, copper acetylacetonate and zirconium acetylacetonate.

6. The method for preparing the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber according to claim 1, characterized in that: The heating with heating and stirring refers to heating from room temperature to 50-80°C.

7. The method for preparing the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber according to claim 1, characterized in that: The thermal oxidation stabilization temperature is 200-300° C., and the thermal oxidation stabilization insulation time is 0.5-2 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 heating rate of the carbon thermal reduction reaction is 5 to 10° C. / min, and the heat preservation time is 2 to 5 hours.

9. 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 that in step 1.

10. 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 according to the preparation method of the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber according to any one of claims 1 to 9.

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