Composite magnetic wave-absorbing carbon fiber based on conjugated microporous polymer as well as preparation method and application of composite magnetic wave-absorbing carbon fiber

Abstract

The invention relates to a composite magnetic wave-absorbing carbon fiber based on a conjugated microporous polymer and a preparation method and application thereof.According to the method, the conjugated microporous polymer and transition metal iron and cobalt elements are selectively introduced to serve as components of the wave-absorbing fiber, and the microstructure of the constructed nanofiber can enhance the scattering and electromagnetic synergistic effect; meanwhile, relatively high absorption strength and relatively wide absorption bandwidth are realized, and the wave-absorbing carbon fiber with wide frequency and strong absorption performance is developed.

Description

Technical Field

[0001] The present invention belongs to the field of microwave absorbing materials, and particularly relates to a composite magnetic microwave absorbing carbon fiber based on conjugated microporous polymers, and a preparation method and application thereof. Background Art

[0002] With the increasing demand for electromagnetic protection materials, the development and preparation of new microwave absorbing fibers that meet the requirements of "strong, wide, light, and thin" with excellent stability have become a major research focus in the field of microwave absorbing materials. In recent years, carbon fibers have been widely used as microwave absorbing fibers. However, carbon fibers have the disadvantages of high conductivity, single loss mechanism, and narrow absorption bandwidth. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a composite magnetic microwave absorbing carbon fiber based on conjugated microporous polymers, and a preparation method and application thereof. The composite magnetic microwave absorbing carbon fiber has electromagnetic dual components, which can effectively improve the impedance matching on the fiber surface; and the nano-fiber structure and the defect interface between the electromagnetic components and the carbon matrix can provide a large number of active sites for polarization, enhancing the attenuation loss ability of electromagnetic waves, thereby obtaining microwave absorbing performance with high absorption intensity and wide absorption bandwidth.

[0004] The present invention provides a composite magnetic microwave absorbing carbon fiber, which is obtained by in-situ growing conjugated microporous polymers on a nanofiber membrane and then introducing magnetic nanoparticles through pyrolysis.

[0005] The present invention provides a preparation method of a composite magnetic microwave absorbing carbon fiber, comprising:

[0006] (1) Preparation of precursor nanofibers:

[0007] Mix a monomer, polyacrylonitrile, and a solvent to obtain a spinning solution, and spin to obtain a precursor nanofiber membrane;

[0008] (2) In-situ growth of conjugated microporous polymers

[0009] Perform a metal coupling reaction on the precursor nanofiber membrane and a mixture, to obtain a composite nanofiber membrane; wherein the mixture is a mixture of an organic ligand, a catalyst, sodium tert-butoxide, and a solvent;

[0010] (3) Introducing magnetic nanoparticles through high-temperature pyrolysis

[0011] Immerse the composite nanofiber membrane in a mixed solution containing an iron source and a cobalt source, and carbonize to obtain the composite magnetic microwave absorbing carbon fiber.

[0012] Preferably, the monomer in step (1) is an aromatic monomer; the aromatic monomer includes tris(4-bromophenyl)amine and p-phenylenediamine; the solvent includes N-N-dimethylformamide; the molar ratio of tris(4-bromophenyl)amine to p-phenylenediamine in the monomer is (0.8-1.2):(1.3-1.8).

[0013] Preferably, the ratio of the monomer to polyacrylonitrile in step (1) is (2-3) mmol:(1.5-1.8) g.

[0014] Preferably, the spinning process parameters in step (1) include: the positive voltage is 8-12 kV, the negative voltage is 4-6 kV, the distance between the syringe needle and the receiver is 9-17 cm, the extrusion speed is 0.8-1.2 mL / h, and the receiver rotation speed is 100-300 rpm.

[0015] In step (2), a metal coupling reaction is used to prepare the conjugated microporous polymer PTPA.

[0016] Preferably, the organic ligand in step (2) includes 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl; the catalyst includes bis(dibenzylideneacetone)palladium(0); the solvent includes toluene.

[0017] Preferably, the molar ratio of the monomer, organic ligand, catalyst, and sodium tert-butoxide in step (2) is (2-3):(0.09-0.12):(0.06-0.08):(3.8-4.2).

[0018] Preferably, the coupling reaction in step (2) is carried out at 100-110 °C for 24-48 h in an anhydrous and anaerobic environment.

[0019] Further, for the metal coupling reaction: take bis(dibenzylideneacetone)palladium(0) (0.06-0.08 mmol), 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (0.09-0.12 mmol), and sodium tert-butoxide (3.8-4.2 mmol) in a reaction tube, add anhydrous toluene, and then react with the precursor nanofibers at 100-110 °C under a nitrogen atmosphere for 24-48 h. After the reaction is cooled to room temperature, wash, and finally dry to obtain PTPA nanofibers; the washing is to roughly wash the product with methanol, chloroform, and deionized water; the ratio of bis(dibenzylideneacetone)palladium(0), 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl, and sodium tert-butoxide is (0.06-0.08 mmol):(0.09-0.12 mmol):(3.8-4.2 mmol):70-80 ml.

[0020] Preferably, in step (3), the iron source includes iron salts; the cobalt source includes cobalt salts; among which, the iron salts include ferric chloride hexahydrate; the cobalt salts include cobalt acetylacetonate.

[0021] Preferably, in step (3), the ratio of the composite nanofiber membrane, the iron source and the cobalt source is (0.1 - 0.5) g : (0.01 - 0.5) mol : (0.01 - 0.5) mol.

[0022] In step (3), the mixed solution containing the iron source and the cobalt source, wherein the solvent of the mixed solution includes one or more of methanol and water.

[0023] The impregnation time in step (3) is 6 - 12 h.

[0024] Preferably, in step (3), carbonization is carried out in an inert atmosphere (such as N2, etc.), the carbonization heating rate is 3 - 10 °C / min, the carbonization temperature is 600 - 900 °C, and the heat preservation time is 1 - 3 h.

[0025] Before carbonization in step (3), washing and drying are carried out, wherein drying is carried out at 50 - 65 °C for 5 - 15 h.

[0026] The present invention provides an application of the composite magnetic wave - absorbing carbon fiber in the field of electromagnetic protection.

[0027] In the present invention, an electrospinning method is used to prepare a precursor nanofiber membrane of aromatic monomers and polyacrylonitrile; conjugated microporous polymers are in - situ grown on the nanofiber membrane; then Fe and Co nanoparticles are introduced during the pyrolysis process to obtain composite magnetic wave - absorbing carbon fibers.

[0028] The method of the present invention selects to introduce conjugated microporous polymers, transition metals iron and cobalt elements as components of the wave - absorbing fibers, and the constructed microstructure of the nanofibers can enhance the scattering and electromagnetic synergy effect. Meanwhile, a strong absorption intensity and a wide absorption bandwidth are achieved, and a wave - absorbing carbon fiber with wide - band and strong absorption performance is developed.

[0029] The strongest absorption intensity of the composite magnetic wave - absorbing carbon fiber of the present invention reaches - 59.9 dB, and the maximum absorption bandwidth below - 10 dB is 5.7 GHz.

[0030] Beneficial effects

[0031] (1) The present invention provides a composite magnetic wave - absorbing carbon fiber based on conjugated microporous polymers, using conjugated microporous polymers as precursors. Its unique pore structure increases the multiple scattering of electromagnetic waves inside it, thereby enhancing the loss; and on this basis, magnetic metals are loaded to introduce a magnetic loss mechanism, and it has high - strength and wide - band absorption performance under the electromagnetic coupling synergistic loss mechanism, providing a new method for assembling "light, thin, wide, and strong" wave - absorbing materials;

[0032] (2) The preparation method of a composite magnetic wave-absorbing carbon fiber based on conjugated microporous polymer provided by the present invention obtains composite magnetic wave-absorbing carbon fibers with uniform diameters through electrospinning. The microstructure and morphology between nanofibers also play a positive role in improving the wave-absorbing performance of fiber materials. Description of the Drawings

[0033] Figure 1 It is the absorption performance diagram of a composite magnetic wave-absorbing carbon fiber based on conjugated microporous polymer provided in Example 1 of the present invention;

[0034] Figure 2 It is the absorption performance diagram of a composite magnetic wave-absorbing carbon fiber based on conjugated microporous polymer provided in Example 2 of the present invention;

[0035] Figure 3 It is the absorption performance diagram of a composite magnetic wave-absorbing carbon fiber based on conjugated microporous polymer provided in Example 3 of the present invention;

[0036] Figure 4 It is the absorption performance diagram of carbonized polyacrylonitrile fiber provided in Comparative Example 1 of the present invention;

[0037] Figure 5 It is the absorption performance diagram of the composite powder provided in Comparative Example 2 of the present invention;

[0038] Figure 6 It is the scanning electron microscope micrograph of a composite magnetic wave-absorbing carbon fiber based on conjugated microporous polymer provided in Example 2 of the present invention. Detailed Embodiments

[0039] The following further elaborates the present invention in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0040] In both the embodiments and comparative examples, the coaxial method is adopted for testing. The composite magnetic carbon fiber and the paraffin matrix need to be mixed evenly according to a mass ratio of 2:8 and pressed into a concentric cylinder with an inner diameter of 3.04 mm and an outer diameter of 7 mm. Reference test standard: SJ 20512-1995 Test Method for Complex Dielectric Constant and Complex Magnetic Permeability of Microwave High-Loss Solid Materials.

[0041] Example 1

[0042] The composite magnetic wave-absorbing carbon fiber based on conjugated microporous polymer is prepared by the following method:

[0043] Weigh 1.5 g of polyacrylonitrile, 1 mmol of tris(4-bromophenyl)amine, and 1.5 mmol of p-phenylenediamine, and place them in 8.5 g of N,N-dimethylformamide. Swell at room temperature for 3 h and dissolve at 60 °C for 4 h to obtain a spinning solution. Take a 10 mL syringe to extract an appropriate amount of the above-prepared spinning solution, and then fix the syringe on a micro pump. Set the distance from the syringe to the receiver to be 13 cm, the left and right swing distance of the translation motor to be 40 mm, the moving speed to be 10 mm / min, set the positive voltage to be 10 kV, the negative voltage to be 5 kV, the extrusion speed to be 1.0 mL / h, and the rotation speed of the receiver to be 100 rpm to obtain a precursor nanofiber membrane.

[0044] Prepare PTPA / PAN fibers through Buchwald-Hartwig coupling reaction. Specifically, bis(dibenzylideneacetone)palladium(0) (0.07 mmol), 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (0.10 mmol), and sodium tert-butoxide (4.0 mmol) are placed in a Schlenk tube (volume 100 ml). Hang the precursor nanofiber membrane in the Schlenk tube to avoid contacting the magnetic stir bar at the bottom of the tube. Dissolve the mixture in 75 mL of anhydrous toluene under an anhydrous and anaerobic environment, and then react at 110 °C for 24 h. After the reaction is completed, cool to room temperature, and then rinse three times with methanol and water respectively. Finally, place the product in a vacuum oven at 40 °C and dry for 12 h to obtain a PTPA nanofiber membrane.

[0045] Weigh 0.01 mol of ferric chloride hexahydrate, 0.01 mol of cobalt acetylacetonate, and 100 mL of methanol in a 200 mL beaker, and stir for 0.5 h until fully dispersed to obtain a mixed solution of Fe ions and Co ions. Take 0.2 g of the PTPA nanofiber membrane and place it in the mixed solution, and take it out and rinse after 6 h. Then dry the above fiber membrane in an oven at 60 °C for 12 h and carbonize it under a N2 atmosphere. The temperature is 700 °C, the heating rate is 5 °C / min, and the holding time is 2 h.

[0046] When the thickness is 5.0 mm, the strongest absorption intensity of the composite magnetic wave-absorbing carbon fiber reaches -46.6 dB; when the thickness is 2.5 mm, the maximum absorption bandwidth below -10 dB is 5.1 GHz.

[0047] Example 2

[0048] The composite magnetic wave-absorbing carbon fiber based on conjugated microporous polymer is prepared by the following method:

[0049] Weigh 1.5 g of polyacrylonitrile, 1 mmol of tris(4-bromophenyl)amine, and 1.5 mmol of p-phenylenediamine and place them in 8.5 g of N,N-dimethylformamide. Swell at room temperature for 3 h and dissolve at 60 °C for 4 h to obtain a spinning solution. Take a 10 mL syringe and draw an appropriate amount of the above-prepared spinning solution, and then fix the syringe on a micro pump. Set the distance from the syringe to the receiver to be 13 cm, the left and right swing distance of the translation motor to be 40 mm, the moving speed to be 10 mm / min, set the positive voltage to be 10 kV, the negative voltage to be 5 kV, the extrusion speed to be 1.0 mL / h, and the rotation speed of the receiver to be 100 rpm to obtain a precursor nanofiber membrane.

[0050] Prepare PTPA / PAN fibers through Buchwald-Hartwig coupling reaction. Specifically, bis(dibenzylideneacetone)palladium(0) (0.07 mmol), 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (0.10 mmol), and sodium tert-butoxide (4 mmol) are placed in a Schlenk tube (volume 100 ml). Suspend the precursor nanofiber membrane in the Schlenk tube to avoid contacting the magnetic stirrer at the bottom of the tube, dissolve the mixture in 75 mL of anhydrous toluene under an anhydrous and anaerobic environment, and then react at 110 °C for 24 h. After the reaction is completed, cool to room temperature, and then rinse three times with methanol and water respectively. Finally, place the product in a vacuum oven at 40 °C and dry for 12 h to obtain a PTPA nanofiber membrane.

[0051] Weigh 0.05 mol of ferric chloride hexahydrate, 0.05 mol of cobalt acetylacetonate, and 100 mL of methanol in a 200 mL beaker, and stir for 0.5 h until fully dispersed to obtain a mixed solution of Fe ions and Co ions. Take 0.2 g of the PTPA nanofiber membrane and place it in the mixed solution, take it out and rinse after placing for 6 h. Then dry the above fiber membrane in an oven at 60 °C for 12 h and carbonize it under a N2 atmosphere. The temperature is 700 °C, the heating rate is 5 °C / min, and the holding time is 2 h.

[0052] When the matching thickness is 5.0 mm, the strongest absorption intensity of the composite magnetic wave-absorbing carbon fiber reaches -41.4 dB; when the thickness is 2.5 mm, the maximum absorption bandwidth below -10 dB is 5.7 GHz.

[0053] Example 3

[0054] The composite magnetic wave-absorbing carbon fiber based on conjugated microporous polymer is prepared by the following method:

[0055] Weigh 1.5 g of polyacrylonitrile, 1 mmol of tris(4-bromophenyl)amine, and 1.5 mmol of p-phenylenediamine and place them in 8.5 g of N,N-dimethylformamide. Swell at room temperature for 3 h and dissolve at 60 °C for 4 h to obtain a spinning solution. Take a 10 mL syringe and draw an appropriate amount of the above-prepared spinning solution, and then fix the syringe on a micropump. Set the distance from the syringe to the receiver to 13 cm, the left and right swing distance of the translation motor to 40 mm, the moving speed to 10 mm / min, set the positive voltage to 10 kV, the negative voltage to 5 kV, the extrusion speed to 1.0 mL / h, and the rotation speed of the receiver to 100 rpm to obtain a precursor nanofiber membrane.

[0056] Prepare PTPA / PAN fibers through Buchwald-Hartwig coupling reaction. Specifically, bis(dibenzylideneacetone)palladium(0) (0.07 mmol), 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (0.10 mmol), and sodium tert-butoxide (4 mmol) are placed in a Schlenk tube (volume 100 ml). Hang the precursor nanofiber membrane in the Schlenk tube to avoid contacting the magnetic stirrer at the bottom of the tube. Dissolve the mixture in 75 mL of anhydrous toluene under an anhydrous and anaerobic environment, and then react at 110 °C for 24 h. After the reaction is completed, cool to room temperature, and then rinse three times with methanol and water respectively. Finally, place the product in a vacuum oven at 40 °C and dry for 12 h to obtain a PTPA nanofiber membrane.

[0057] Weigh 0.1 mol of ferric chloride hexahydrate, 0.1 mol of cobalt acetylacetonate, and 100 mL of methanol in a 200 mL beaker, and stir for 0.5 h until fully dispersed to obtain a mixed solution of Fe ions and Co ions. Take 0.2 g of the PTPA nanofiber membrane and place it in the mixed solution, and then take it out and rinse after 6 h. Then dry the above fiber membrane in an oven at 60 °C for 12 h and carbonize it under a N2 atmosphere. The temperature is 700 °C, the heating rate is 5 °C / min, and the holding time is 2 h.

[0058] When the matching thickness is 5.0 mm, the strongest absorption intensity of the composite magnetic wave-absorbing carbon fiber reaches -59.9 dB; when the thickness is 2.5 mm, the maximum absorption bandwidth below -10 dB is 5.1 GHz.

[0059] Comparative Example 1

[0060] Carbonized polyacrylonitrile fiber is prepared by the following method:

[0061] Weigh 1.5 g of polyacrylonitrile and place it in 8.5 g of N,N-dimethylformamide. Swell it at room temperature for 3 h and dissolve it at 60 °C for 4 h to obtain a spinning solution. Take a 10 mL syringe to extract an appropriate amount of the above-prepared spinning solution, and then fix the syringe on a micro pump. Set the distance from the syringe to the receiver to be 13 cm, the left and right swing distance of the translation motor to be 40 mm, the moving speed to be 10 mm / min, set the positive voltage to be 10 kV, the negative voltage to be 5 kV, the extrusion speed to be 1.0 mL / h, and the rotation speed of the receiver to be 100 rpm to obtain polyacrylonitrile nanofibers.

[0062] Carbonize the above polyacrylonitrile nanofibers under a N2 atmosphere at a temperature of 700 °C, a heating rate of 5 °C / min, and a holding time of 2 h.

[0063] When the matching thickness is 5.0 mm, the strongest absorption intensity of the carbonized polyacrylonitrile fiber reaches -20.0 dB. When the thickness is 2.5 mm, the maximum absorption bandwidth below -10 dB is 5.23 GHz.

[0064] Comparative Example 2

[0065] The composite magnetic wave-absorbing carbon material based on conjugated microporous polymer is prepared by the following method:

[0066] Prepare the composite magnetic wave-absorbing carbon material through Buchwald-Hartwig coupling reaction. Specifically, weigh 1 mmol of tris(4-bromophenyl)amine, 1.5 mmol of p-phenylenediamine, palladium(0) bis(dibenzylideneacetone) (0.07 mmol), 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (0.10 mmol) and sodium tert-butoxide (4.0 mmol) in a Schlenk tube. Dissolve the mixture in 75 mL of anhydrous toluene under an anhydrous and anaerobic environment, and then react at 110 °C for 24 h. After the reaction is completed, cool it to room temperature, and then rinse it three times with methanol and water respectively. Finally, place the product in a vacuum oven at 40 °C and dry it for 12 h to obtain a composite powder.

[0067] Weigh 0.05 mol of ferric chloride hexahydrate, 0.05 mol of cobalt acetylacetonate, and 100 mL of methanol in a 200 mL beaker, and stir for 0.5 h until fully dispersed to obtain a mixed solution of Fe ions and Co ions. Take 0.2 g of the composite powder and place it in the mixed solution, take it out and rinse it after 6 h. Then dry the product in an oven at 60 °C for 12 h and carbonize it under a N2 atmosphere. The temperature is 700 °C, the heating rate is 5 °C / min, and the holding time is 2 h.

[0068] When the matching thickness is 5.0 mm, the strongest absorption intensity of the composite magnetic wave-absorbing carbon fiber reaches -16.4 dB. When the thickness is 2.5 mm, the maximum absorption bandwidth below -10 dB is 2.94 GHz.

Claims

1. A composite magnetic wave-absorbing carbon fiber, characterized in that, The composite magnetic wave-absorbing carbon fiber is obtained by in-situ growing conjugated microporous polymers on a nanofiber membrane and then introducing magnetic nanoparticles through pyrolysis.

2. A method for preparing a composite magnetic wave-absorbing carbon fiber, comprising: (1) Mixing a monomer, polyacrylonitrile, and a solvent to obtain a spinning solution, and spinning to obtain a precursor nanofiber membrane; (2) Performing a coupling reaction on the precursor nanofiber membrane and a mixture, to obtain a composite nanofiber membrane; wherein the mixture comprises a mixture of an organic ligand, a catalyst, sodium tert-butoxide, and a solvent; (3) Immersing the composite nanofiber membrane in a mixed solution containing an iron source and a cobalt source, and carbonizing to obtain the composite magnetic wave-absorbing carbon fiber.

3. The preparation method according to claim 2, wherein, In the step (1), the monomer is an aromatic monomer; wherein the aromatic monomer comprises tris(4-bromophenyl)amine and p-phenylenediamine; the solvent comprises N,N-dimethylformamide; In the step (1), the ratio of the monomer to polyacrylonitrile is (2-3) mmol:(1.5-1.8) g.

4. The preparation method according to claim 2, characterized in that, The spinning process parameters in the step (1) include: the positive voltage is 8-12 kV, the negative voltage is 4-6 kV, the distance between the syringe needle and the receiver is 9-17 cm, the extrusion speed is 0.8-1.2 mL / h, and the rotation speed of the receiver is 100-300 rpm.

5. The preparation method according to claim 2, characterized in that, In the step (2), the organic ligand comprises 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl; the catalyst comprises bis(dibenzylideneacetone)palladium; the solvent comprises toluene.

6. The preparation method according to claim 2, wherein, In the step (2), the molar ratio of the monomer, the organic ligand, the catalyst, and sodium tert-butoxide is (2-3):(0.09-0.12):(0.06-0.08):(3.8-4.2).

7. The preparation method according to claim 2, characterized in that, In the step (2), the coupling reaction is carried out in an anhydrous and anaerobic environment at 100-110 °C for 24-48 h.

8. The preparation method according to claim 2, wherein In the step (3), the iron source comprises an iron salt; the cobalt source comprises a cobalt salt; wherein the iron salt comprises ferric chloride hexahydrate; the cobalt salt comprises cobalt acetylacetonate; In the step (3), the ratio of the composite nanofiber membrane, the iron source, and the cobalt source is (0.1-0.5) g:(0.01-0.5) mol:(0.01-0.5) mol.

9. The preparation method according to claim 2, characterized in that, In the step (3), the carbonization is carried out in an inert atmosphere, the carbonization heating rate is 3-10 °C / min, the carbonization temperature is 600-900 °C, and the holding time is 1-3 h; In the step (3), the immersion time is 6-12 h.

10. An application of the composite magnetic wave-absorbing carbon fiber according to claim 1 in the field of electromagnetic protection.

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