Surface in-situ catalytic growth CNTs modified magnetic carbon nanofiber composite material and preparation method thereof

Abstract

The invention discloses a surface in-situ catalytic growth CNTs modified magnetic carbon nanofiber composite material and a preparation method thereof, and belongs to the technical field of carbon-based functional composite materials. The preparation method comprises the following steps: firstly, metal salt and polyacrylonitrile are magnetically stirred and dissolved in a solvent at room temperature, and a homogeneous polyacrylonitrile electrostatic spinning solution containing a metal salt precursor is prepared; preparing a polyacrylonitrile nanofiber membrane loaded with a metal salt precursor by utilizing electrostatic spinning; then carrying out pre-oxidation treatment on the polyacrylonitrile nanofiber membrane loaded with the metal salt precursor; and finally carrying out high-temperature calcination on the pre-oxidized fiber membrane in a tubular furnace under the protection of inert gas to finally obtain the magnetic carbon nanofiber composite material with CNTs grown on the surface through in-situ catalysis. According to the preparation method disclosed by the invention, a simple electrostatic spinning process is combined with a high-temperature calcination process, and CNTs are catalytically grown on the upper surfaces of the carbon nanofibers in situ, so that the material has good conductivity and excellent electromagnetic wave absorption capacity.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon-based functional composite materials, and in particular relates to a surface in-situ catalytic growth CNTs modified magnetic carbon nanofiber composite material and a preparation method thereof. Background Art

[0002] With the development of modern science and technology, a large number of electronic products and communication devices have been widely used. While these devices provide convenience for human life, they also generate serious electromagnetic radiation pollution. Electromagnetic radiation pollution not only affects the normal operation of various electronic devices but also poses long-term risks to human health. The use of high-performance electromagnetic absorbing materials is one of the main means to address electromagnetic radiation pollution.

[0003] The high conductivity of traditional commercial carbon fibers results in their primary reflection of electromagnetic waves, leading to their use in electromagnetic shielding rather than absorption. This limits the application of carbon fibers and their composites. Carbon nanofibers (CNFs), particularly electrospun carbon nanofiber composites, offer advantages such as high surface area, excellent conductivity, flexibility, diverse structures, and stable chemical and physical properties. Their outstanding dielectric loss performance makes them a widely studied carbon-based electromagnetic functional material. Surface treatments, such as surface loading with CNTs, are an effective strategy for regulating the conductivity of carbon nanofibers, improving their impedance matching performance, and optimizing their electromagnetic microwave absorption properties.

[0004] At present, existing documents disclose the construction of CNTs / CNFs composite materials, which are usually ultrasonically dispersed in a solvent to obtain an electrospinning solution, and then spun and subjected to high-temperature heat treatment through an optimized spinning process to obtain carbon nanocomposite fibers containing CNTs. For example, the authorization announcement number CN112382755B discloses a transition metal-doped sulfide polyacrylonitrile flexible cathode material and its preparation method. The distribution and content of CNTs in the carbon nanocomposite fiber matrix are affected by the spinning solution. In addition, adding CNTs directly to the spinning solution and then spinning is prone to clogging the spinneret, affecting the preparation and quality of electrospun products. Moreover, due to the hydrophobic properties of the carbon material itself, its stable and uniform dispersion during spinning is also a problem.

[0005] Therefore, there is an urgent need to design a carbon nanofiber composite material that can make the distribution of CNTs in carbon nanofibers more uniform and more stable, so as to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems of complex preparation process and poor absorption performance of composite absorbing materials in the prior art, and to provide a surface in situ catalytic growth of CNTs modified magnetic carbon nanofiber composite material and a preparation method thereof. The magnetic carbon nanofiber composite material with in situ catalytic growth of CNTs on its surface is prepared by a simple electrospinning process combined with a high-temperature calcination process, so that the distribution of CNTs in the carbon nanofibers is more uniform and the stability is better. The prepared material has good electrical conductivity and excellent electromagnetic wave absorption ability.

[0007] To achieve the above object, the present invention adopts the following technical solution: a method for preparing a surface in-situ catalytic growth CNTs modified magnetic carbon nanofiber composite material, comprising the following steps:

[0008] S1. Preparation of electrospinning precursor solution:

[0009] The metal salt and polyacrylonitrile are dissolved in a solvent under magnetic stirring at room temperature to prepare a homogeneous polyacrylonitrile electrospinning solution containing a metal salt precursor, and the solution is allowed to stand for degassing before use;

[0010] The mass concentration of the metal salt in the electrospinning solution is 1% to 5%, and the concentration of polyacrylonitrile is 8% to 12%;

[0011] S2. Electrospinning preparation and pre-oxidation treatment of polyacrylonitrile fiber membrane:

[0012] The polyacrylonitrile electrospinning solution prepared in step S1 was poured into a 20 mL syringe equipped with a stainless steel needle, and spun according to the set electrospinning process parameters to obtain a polyacrylonitrile fiber membrane containing metal salts. The solvent was dried to remove the solvent, and then the membrane was pre-oxidized at medium temperature in a muffle furnace.

[0013] The electrospinning process parameters were as follows: the nanofibers were collected by tin foil during spinning, the high-voltage DC power supply was 15–20 kV, the distance between the needle tip and the tin foil collector was 15 cm, and the injection pump propulsion speed was 0.05 mL / min. -1 , drum speed is 300r·min -1 , relative humidity is 25% to 35% RH, and the temperature is set to 25±2℃;

[0014] S3. Preparation of magnetic carbon nanofiber composites with in-situ catalytic growth of CNTs on the surface:

[0015] The polyacrylonitrile fiber membrane after pre-oxidation treatment in the above step S2 is placed in a tubular furnace, a ceramic ark filled with melamine is placed upstream of the air flow, and a ceramic ark filled with polyacrylonitrile fiber membrane is placed downstream, wherein the mass ratio of melamine to polyacrylonitrile fiber is 1:1 to 1:3, and then high-temperature calcination at 700 to 900°C is carried out in an inert atmosphere. After carbonization treatment, a magnetic carbon nanofiber composite material with in-situ catalytic growth of CNTs on the surface is finally obtained.

[0016] In step S1, the metal salt is one or more of ferric chloride, nickel chloride, cobalt chloride, ferric acetate, nickel acetate, cobalt acetate, ferric sulfate, nickel sulfate, cobalt sulfate, ferric nitrate, nickel nitrate, cobalt nitrate, ferric acetylacetonate, nickel acetylacetonate, and cobalt acetylacetonate.

[0017] Preferably, the metal salt is an acetylacetone complex salt.

[0018] In step S1, the solvent is one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO).

[0019] Preferably, the solvent is N,N-dimethylformamide.

[0020] In step S1, the standing and degassing time is 2 hours.

[0021] In step S2, the temperature of the pre-oxidation treatment is 200-300° C., and the treatment time is 1-3 hours.

[0022] In step S3, the high-temperature calcination time is 2 to 4 hours.

[0023] In the step S3, preferably, the calcination temperature is 700° C., the calcination time is 2 h, and the mass ratio of melamine to polyacrylonitrile fiber is 1:3.

[0024] The present invention also provides a magnetic carbon nanofiber composite material prepared by the above preparation method, wherein the microstructure of the magnetic carbon nanofiber composite material is a three-dimensional carbon nanofiber network.

[0025] The beneficial effects of the present invention are:

[0026] 1) The present invention utilizes a simple electrospinning-preoxidation-carbonization process to integrate magnetic metal nanoparticles and one-dimensional carbon nanotubes (CNTs) into carbon nanofibers, forming a carbon nanofiber network with a unique three-dimensional structure. The composite absorbing material uniformly catalyzes the growth of CNTs on the surface of preoxidized polyacrylonitrile fibers, achieving a multi-dimensional and multi-scale structural design and construction. The resulting magnetic carbon nanofiber composite material has excellent impedance matching and attenuation performance, and can fully absorb and attenuate electromagnetic waves to achieve a high-efficiency loss effect.

[0027] 2) The carbon nanofiber composite material prepared by the present invention has the characteristics of light weight and adjustable conductivity, and the unique in-situ catalytic growth and embedding method of CNTs provides a new perspective for creating high-performance, lightweight electromagnetic wave absorbers; and CNTs are grown by in-situ catalytic growth, and their distribution in the carbon nanofibers is more uniform and more stable. When used as an absorbing material, the minimum reflection loss value can reach -40dB, absorbing 99.99% of electromagnetic waves.

[0028] 3) The present invention can effectively adjust the density and distribution of magnetic particles in nanofibers by simply controlling the type and concentration of magnetic metal nanoparticles in the precursor, thereby achieving precise control of magnetic loss and electromagnetic balance; on this premise, carbon nanotubes with excellent conductivity are further incorporated into carbon nanofibers to enhance their conductive loss capacity and impedance matching characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a scanning electron microscope image of the CNTs / Fe@CNFs-1 composite material prepared in Example 1 of the present invention;

[0030] Figure 2 This is a reflection loss curve of the CNTs / Fe@CNFs-1 composite material prepared in Example 1 of the present invention at different matching thicknesses.

[0031] Figure 3 This is a scanning electron microscope image of the CNTs / Fe@CNFs-2 composite material prepared in Example 2 of the present invention;

[0032] Figure 4 This is a scanning electron microscope image of the CNTs / Co@CNFs-3 composite material prepared in Example 3 of the present invention;

[0033] Figure 5 This is a reflection loss curve of the CNTs / Co@CNFs-3 composite material prepared in Example 3 of the present invention at different matching thicknesses;

[0034] Figure 6 This is a scanning electron microscope image of the CNTs / Fe@CNFs-01 composite material prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0036] Example 1: A method for preparing a magnetic carbon nanofiber composite material with in-situ catalytic growth of CNTs on the surface, comprising the following steps:

[0037] S1. Preparation of electrospinning precursor solution: 2% ferric acetylacetonate and 10% PAN were magnetically stirred and dissolved in 20 mL DMF. The mixture was stirred at room temperature for 12 h to uniformly disperse in the solvent. The mixture was allowed to stand for 2 h to degas. A homogeneous spinning precursor solution was obtained for later use.

[0038] S2. Electrospinning Preparation and Preoxidation of Polyacrylonitrile Fiber Membrane: The prepared spinning precursor solution was poured into a 20 mL syringe equipped with a stainless steel needle and spun according to the set electrospinning process parameters to obtain a polyacrylonitrile fiber membrane containing metal salts. The membrane was dried to remove the solvent and then preoxidized at 200°C in a muffle furnace for 2 h.

[0039] The electrospinning process parameters were as follows: the nanofibers were collected by tin foil, the high-voltage DC power supply was 18 kV, the distance between the needle tip and the tin foil collector was 15 cm, and the injection pump propulsion speed was 0.05 mL min -1 , drum speed is 300r·min -1 , relative humidity is 25%~35%RH, and temperature is 25±2℃.

[0040] S3. Preparation of magnetic carbon nanofiber composite materials with in situ catalytic growth of CNTs on the surface: The pre-oxidized polyacrylonitrile fiber membrane was placed in a tubular furnace, and a ceramic ark containing 1g of melamine was placed upstream of the air flow, and a ceramic ark containing the polyacrylonitrile fiber membrane was placed downstream. The composite materials were calcined at 700°C in an inert atmosphere for 3h. After carbonization treatment, a magnetic carbon nanofiber composite material with in situ catalytic growth of CNTs on the surface (CNTs / Fe@CNFs-1) was finally obtained.

[0041] Figure 1 This is a scanning electron microscope image of the magnetic carbon nanofiber composite material (CNTs / Fe@CNFs-1) with in situ catalytic growth of CNTs on the surface obtained in Example 1. It can be seen from the figure that the CNTs / Fe@CNFs-1 composite material has a unique three-dimensional network structure and can form a good conductive path.

[0042] Figure 2This is a diagram of the microwave absorption performance of the magnetic carbon nanofiber composite material (CNTs / Fe@CNFs-1) with in situ catalytic growth of CNTs on the surface obtained in Example 1. The data show that the CNTs / Fe@CNFs-1 composite material has excellent microwave absorption performance.

[0043] Example 2: A method for preparing a magnetic carbon nanofiber composite material with in-situ catalytic growth of CNTs on the surface, comprising the following steps:

[0044] S1. Preparation of electrospinning precursor solution: 2% ferric acetylacetonate and 10% PAN were magnetically stirred and dissolved in 20 mL DMF. The mixture was stirred at room temperature for 12 h to uniformly disperse in the solvent. The mixture was allowed to stand for 2 h to degas. A homogeneous spinning precursor solution was obtained for later use.

[0045] S2. Electrospinning Preparation and Preoxidation of Polyacrylonitrile Fiber Membrane: The prepared spinning precursor solution was poured into a 20 mL syringe equipped with a stainless steel needle and spun according to the set electrospinning process parameters to obtain a polyacrylonitrile fiber membrane containing metal salts. The membrane was dried to remove the solvent and then preoxidized at 200°C in a muffle furnace for 2 h.

[0046] The electrospinning process parameters were as follows: the nanofibers were collected by tin foil, the high-voltage DC power supply was 18 kV, the distance between the needle tip and the tin foil collector was 15 cm, and the injection pump propulsion speed was 0.05 mL min -1 , drum speed is 300r·min -1 , relative humidity is 25%~35%RH, and temperature is 25±2℃.

[0047] S3. Preparation of magnetic carbon nanofiber composite materials with in situ catalytic growth of CNTs on the surface: The pre-oxidized polyacrylonitrile fiber membrane is placed in a tubular furnace, a ceramic ark containing 3g of melamine is placed upstream of the air flow, and a ceramic ark containing the polyacrylonitrile fiber membrane is placed downstream. The materials are calcined at 900°C in an inert atmosphere for 3h. After carbonization treatment, a magnetic carbon nanofiber composite material with in situ catalytic growth of CNTs on the surface (CNTs / Fe@CNFs-2) is finally obtained.

[0048] Figure 3 The scanning electron microscope image of the magnetic carbon nanofiber composite material (CNTs / Fe@CNFs-2) with in situ catalytic growth of CNTs on the surface obtained in Example 2 is shown in FIG. Figure 3 It can be seen that CNTs are uniformly loaded on the surface of polyacrylonitrile-derived carbon nanofibers to form a good conductive path. Compared with Example 1, the amount of CNTs generated in Example 2 is greater and the length is longer.

[0049] Example 3: A method for preparing a magnetic carbon nanofiber composite material with in-situ catalytic growth of CNTs on the surface, comprising the following steps:

[0050] S1. Preparation of electrospinning precursor solution: 1% cobalt acetylacetonate and 8% PAN were magnetically stirred and dissolved in 20 mL DMF. The mixture was stirred at room temperature for 24 h to uniformly disperse in the solvent. The mixture was allowed to stand for 2 h to degas. A homogeneous spinning precursor solution was obtained for later use.

[0051] S2. Electrospinning Preparation and Preoxidation of Polyacrylonitrile Fiber Membrane: The prepared spinning precursor solution was poured into a 20 mL syringe equipped with a stainless steel needle and spun according to the set electrospinning process parameters to obtain a polyacrylonitrile fiber membrane containing metal salts. The membrane was then dried to remove the solvent and then preoxidized at 200°C in a muffle furnace for 1 h.

[0052] The electrospinning process parameters were as follows: the nanofibers were collected by tin foil during spinning, the high-voltage DC power supply was 20 kV, the distance between the needle tip and the tin foil collector was 15 cm, and the injection pump propulsion speed was 0.05 mL min -1 , drum speed is 300r·min -1 , relative humidity is 25%~35%RH, and temperature is 25±2℃.

[0053] S3. Preparation of magnetic carbon nanofiber composite materials with in situ catalytic growth of CNTs on the surface: The pre-oxidized polyacrylonitrile fiber membrane is placed in a tubular furnace, a ceramic ark containing 1g of melamine is placed upstream of the air flow, and a ceramic ark containing the polyacrylonitrile fiber membrane is placed downstream. The composite materials are calcined at 900°C in an inert atmosphere for 2h. After carbonization treatment, a magnetic carbon nanofiber composite material with in situ catalytic growth of CNTs on the surface (CNTs / Fe@CNFs-3) is finally obtained.

[0054] Figure 4 This is a scanning electron microscope image of the magnetic carbon nanofiber composite material (CNTs / Co@CNFs-3) with in situ catalytic growth of CNTs on the surface obtained in Example 3. It can be seen from the figure that the CNTs / Co@CNFs-3 composite material also has a unique three-dimensional network structure. CNTs are evenly loaded on the surface of polyacrylonitrile-derived carbon nanofibers to form a good conductive path.

[0055] Figure 5Figure 3 shows the microwave absorption performance of a magnetic carbon nanofiber composite (CNTs / Co@CNFs-3) with in situ catalytic growth of CNTs on its surface, obtained in Example 3. The data demonstrate that the CNTs / Co@CNFs-3 composite also exhibits excellent microwave absorption. Furthermore, the above examples demonstrate the universal applicability of the present invention, which can be replaced with cobalt acetylacetonate or nickel acetylacetonate as the metal salt.

[0056] Example 4: A method for preparing a magnetic carbon nanofiber composite material with in-situ catalytic growth of CNTs on the surface, comprising the following steps:

[0057] S1. Preparation of electrospinning precursor solution: 2% cobalt acetylacetonate and 8% PAN were magnetically stirred and dissolved in 20 mL DMF. The mixture was stirred at room temperature for 24 h to uniformly disperse in the solvent. The mixture was allowed to stand for 2 h to degas. A homogeneous spinning precursor solution was obtained for later use.

[0058] S2. Electrospinning Preparation and Preoxidation of Polyacrylonitrile Fiber Membrane: The prepared spinning precursor solution was poured into a 20 mL syringe equipped with a stainless steel needle and spun according to the set electrospinning process parameters to obtain a polyacrylonitrile fiber membrane containing metal salts. The membrane was then dried to remove the solvent and then preoxidized at 300°C in a muffle furnace for 1 hour.

[0059] The electrospinning process parameters were as follows: the nanofibers were collected by tin foil during spinning, the high-voltage DC power supply was 20 kV, the distance between the needle tip and the tin foil collector was 15 cm, and the injection pump propulsion speed was 0.05 mL min -1 , drum speed is 300r·min -1 , relative humidity is 25%~35%RH, and temperature is 25±2℃.

[0060] S3. Preparation of magnetic carbon nanofiber composite materials with in situ catalytic growth of CNTs on the surface: The pre-oxidized polyacrylonitrile fiber membrane is placed in a tubular furnace, a ceramic ark containing 2g of melamine is placed upstream of the air flow, and a ceramic ark containing the polyacrylonitrile fiber membrane is placed downstream. The materials are calcined at 700°C in an inert atmosphere for 4h. After carbonization treatment, a magnetic carbon nanofiber composite material with in situ catalytic growth of CNTs on the surface (CNTs / Fe@CNFs-4) is finally obtained.

[0061] Example 5: A method for preparing a magnetic carbon nanofiber composite material with in-situ catalytic growth of CNTs on the surface, comprising the following steps:

[0062] S1. Preparation of electrospinning precursor solution: 5% cobalt acetylacetonate and 8% PAN were magnetically stirred and dissolved in 20 mL DMF. The mixture was stirred at room temperature for 12 h to uniformly disperse in the solvent. The mixture was allowed to stand for 2 h to degas. A homogeneous spinning precursor solution was obtained for later use.

[0063] S2. Electrospinning Preparation and Preoxidation of Polyacrylonitrile Fiber Membrane: The prepared spinning precursor solution was poured into a 20 mL syringe equipped with a stainless steel needle and spun according to the set electrospinning process parameters to obtain a polyacrylonitrile fiber membrane containing metal salts. The membrane was dried to remove the solvent and then preoxidized at 200°C in a muffle furnace for 2 h.

[0064] The electrospinning process parameters were as follows: the nanofibers were collected by tin foil, the high-voltage DC power supply was 18 kV, the distance between the needle tip and the tin foil collector was 15 cm, and the injection pump propulsion speed was 0.05 mL min -1 , drum speed is 300r·min -1 , relative humidity is 25%~35%RH, and temperature is 25±2℃.

[0065] S3. Preparation of magnetic carbon nanofiber composite materials with in situ catalytic growth of CNTs on the surface: The pre-oxidized polyacrylonitrile fiber membrane is placed in a tubular furnace, a ceramic ark containing 3g of melamine is placed upstream of the air flow, and a ceramic ark containing the polyacrylonitrile fiber membrane is placed downstream. The materials are calcined at 800°C in an inert atmosphere for 3h. After carbonization treatment, a magnetic carbon nanofiber composite material with in situ catalytic growth of CNTs on the surface (CNTs / Fe@CNFs-5) is finally obtained.

[0066] Example 6: A method for preparing a magnetic carbon nanofiber composite material with in-situ catalytic growth of CNTs on the surface, comprising the following steps:

[0067] S1. Preparation of electrospinning precursor solution: 1% nickel acetylacetonate and 12% PAN were magnetically stirred and dissolved in 20 mL DMF. The mixture was stirred at room temperature for 12 h to uniformly disperse in the solvent. The mixture was allowed to stand for 2 h to degas. A homogeneous spinning precursor solution was obtained for later use.

[0068] S2. Electrospinning Preparation and Preoxidation of Polyacrylonitrile Fiber Membrane: The prepared spinning precursor solution was poured into a 20 mL syringe equipped with a stainless steel needle and spun according to the set electrospinning process parameters to obtain a polyacrylonitrile fiber membrane containing metal salts. The membrane was then dried to remove the solvent and then preoxidized at 200°C in a muffle furnace for 3 h.

[0069] The electrospinning process parameters were as follows: the nanofibers were collected by tin foil, the high-voltage DC power supply was 18 kV, the distance between the needle tip and the tin foil collector was 15 cm, and the injection pump propulsion speed was 0.05 mL min -1 , drum speed is 300r·min -1 , relative humidity is 25%~35%RH, and temperature is 25±2℃.

[0070] S3. Preparation of magnetic carbon nanofiber composite materials with in situ catalytic growth of CNTs on the surface: The pre-oxidized polyacrylonitrile fiber membrane is placed in a tubular furnace, a ceramic ark containing 1g of melamine is placed upstream of the air flow, and a ceramic ark containing the polyacrylonitrile fiber membrane is placed downstream. The materials are calcined at 900°C in an inert atmosphere for 2h. After carbonization treatment, a magnetic carbon nanofiber composite material with in situ catalytic growth of CNTs on the surface (CNTs / Fe@CNFs-6) is finally obtained.

[0071] Example 7: A method for preparing a magnetic carbon nanofiber composite material with in-situ catalytic growth of CNTs on the surface, comprising the following steps:

[0072] S1. Preparation of electrospinning precursor solution: 2% nickel acetylacetonate and 12% PAN were magnetically stirred and dissolved in 20 mL DMF. The mixture was stirred at room temperature for 12 h to uniformly disperse in the solvent. The mixture was allowed to stand for 2 h to degas. A homogeneous spinning precursor solution was obtained for later use.

[0073] S2. Electrospinning Preparation and Preoxidation of Polyacrylonitrile Fiber Membrane: The prepared spinning precursor solution was poured into a 20 mL syringe equipped with a stainless steel needle and spun according to the set electrospinning process parameters to obtain a polyacrylonitrile fiber membrane containing metal salts. The membrane was then dried to remove the solvent and then preoxidized at 300°C in a muffle furnace for 1 hour.

[0074] The electrospinning process parameters were as follows: the nanofibers were collected by tin foil, the high-voltage DC power supply was 18 kV, the distance between the needle tip and the tin foil collector was 15 cm, and the injection pump propulsion speed was 0.05 mL min -1 , drum speed is 300r·min -1 , relative humidity is 25%~35%RH, and temperature is 25±2℃.

[0075] S3. Preparation of magnetic carbon nanofiber composite materials with in situ catalytic growth of CNTs on the surface: The pre-oxidized polyacrylonitrile fiber membrane is placed in a tubular furnace, a ceramic ark containing 2g of melamine is placed upstream of the air flow, and a ceramic ark containing the polyacrylonitrile fiber membrane is placed downstream. The materials are calcined at 800°C in an inert atmosphere for 3h. After carbonization treatment, a magnetic carbon nanofiber composite material with in situ catalytic growth of CNTs on the surface (CNTs / Fe@CNFs-7) is finally obtained.

[0076] Example 8: A method for preparing a magnetic carbon nanofiber composite material with in-situ catalytic growth of CNTs on the surface, comprising the following steps:

[0077] S1. Preparation of electrospinning precursor solution: 5% nickel acetylacetonate and 12% PAN were magnetically stirred and dissolved in 20 mL DMF. The mixture was stirred at room temperature for 12 h to uniformly disperse in the solvent. The mixture was allowed to stand for 2 h to degas. A homogeneous spinning precursor solution was obtained for later use.

[0078] S2. Electrospinning Preparation and Preoxidation of Polyacrylonitrile Fiber Membrane: The prepared spinning precursor solution was poured into a 20 mL syringe equipped with a stainless steel needle and spun according to the set electrospinning process parameters to obtain a polyacrylonitrile fiber membrane containing metal salts. The membrane was dried to remove the solvent and then preoxidized at 200°C in a muffle furnace for 2 h.

[0079] The electrospinning process parameters were as follows: the nanofibers were collected by tin foil, the high-voltage DC power supply was 18 kV, the distance between the needle tip and the tin foil collector was 15 cm, and the injection pump propulsion speed was 0.05 mL min -1 , drum speed is 300r·min -1 , relative humidity is 25%~35%RH, and temperature is 25±2℃.

[0080] S3. Preparation of magnetic carbon nanofiber composite materials with in situ catalytic growth of CNTs on the surface: The pre-oxidized polyacrylonitrile fiber membrane was placed in a tubular furnace, and a ceramic ark containing 3g of melamine was placed upstream of the air flow, and a ceramic ark containing the polyacrylonitrile fiber membrane was placed downstream. The composite materials were calcined at 700°C in an inert atmosphere for 4 hours. After carbonization treatment, a magnetic carbon nanofiber composite material with in situ catalytic growth of CNTs on the surface (CNTs / Fe@CNFs-8) was finally obtained.

[0081] Comparative Example 1: A method for preparing a magnetic carbon nanofiber composite material with in-situ catalytic growth of CNTs on the surface, comprising the following steps:

[0082] S1. Preparation of electrospinning precursor solution: 2% ferric acetylacetonate and 10% PAN were magnetically stirred and dissolved in 20 mL DMF. The mixture was stirred at room temperature for 12 h to uniformly disperse in the solvent. The mixture was allowed to stand for 2 h to degas. A homogeneous spinning precursor solution was obtained for later use.

[0083] S2. Electrospinning Preparation and Preoxidation of Polyacrylonitrile Fiber Membrane: The prepared spinning precursor solution was poured into a 20 mL syringe equipped with a stainless steel needle and spun according to the set electrospinning process parameters to obtain a polyacrylonitrile fiber membrane containing metal salts. The membrane was dried to remove the solvent and then preoxidized at 200°C in a muffle furnace for 2 h.

[0084] The electrospinning process parameters were as follows: the nanofibers were collected by tin foil, the high-voltage DC power supply was 18 kV, the distance between the needle tip and the tin foil collector was 15 cm, and the injection pump propulsion speed was 0.05 mL min -1 , drum speed is 300r·min -1 , relative humidity is 25%~35%RH, and temperature is 25±2℃.

[0085] S3. Preparation of magnetic carbon nanofiber composite materials with in situ catalytic growth of CNTs on the surface: The pre-oxidized polyacrylonitrile fiber membrane was placed in a tubular furnace, and a ceramic ark containing 3g of melamine was placed upstream of the air flow, and a ceramic ark containing the polyacrylonitrile fiber membrane was placed downstream. The composite materials were calcined at 600°C in an inert atmosphere for 3h. After carbonization treatment, a magnetic carbon nanofiber composite material with in situ catalytic growth of CNTs on the surface (CNTs / Fe@CNFs-01) was finally obtained.

[0086] Figure 6 The scanning electron microscope image of the magnetic carbon nanofiber composite material (CNTs / Fe@CNFs-3) obtained in comparative example 1 is shown in FIG. Figure 6 It can be seen that no CNTs are generated at a calcination temperature of 600° C. Based on the above analysis, the present invention can regulate the generation and content of CNTs by controlling the amount of melamine and the calcination temperature.

[0087] According to the results of single-factor experiments, in the process of preparing magnetic carbon nanofiber composites with surface-loaded CNTs, the solubility of the spinning solution, pre-oxidation treatment, the amount of melamine and high-temperature calcination process have a great influence on the structure and properties of the material, so the process parameters need to be strictly controlled.

[0088] The magnetic carbon nanofiber composite materials prepared in Examples 1 to 8 and Comparative Example 1 were subjected to performance tests, including electromagnetic parameters and absorption bandwidth, as shown in Table 1 below. The absorption performance results measured under different experimental parameters and conditions were obtained.

[0089] Table 1

[0090]

[0091] It can be seen from the above test results that materials with good absorbing properties can be obtained within the experimental conditions range included in Examples 1 to 8, while too low or too high spinning solution solubility is not conducive to spinning. In addition, as shown in the test results obtained in Comparative Example 1, too low high temperature calcination temperature is also not conducive to the in situ catalytic growth of CNTs.

[0092] According to the test results, the different CNTs / M@CNFs composite materials obtained in different specific embodiments have significant differences in their absorption properties, especially the effective absorption band and minimum reflection loss value. Therefore, the absorption properties of the composite materials can be regulated by simply controlling the type and concentration of the metal particle precursors and the high-temperature calcination treatment temperature, thereby making the electromagnetic parameters and electromagnetic wave absorption capacity of the products controllable and adjustable.

[0093] The amount of melamine used in the method of the present invention and the subsequent high-temperature calcination treatment temperature not only affect the dielectric / magnetic properties of the final CNTs / M@CNFs composite material, but also affect the attenuation and matching performance of the composite material, thereby affecting the composite material's absorption performance.

[0094] In the method of the present invention, a polyacrylonitrile fiber membrane containing a metal salt precursor is first prepared by an electrospinning process, and then subjected to a medium-temperature pre-oxidation treatment. CNTs are in situ catalytically grown on its surface using the membrane as a carrier to obtain a magnetic carbon nanofiber composite material loaded with CNTs. The preparation method is simple, and the prepared material exhibits excellent electromagnetic wave absorption capacity, good impedance matching and attenuation performance, and can fully absorb and attenuate electromagnetic waves to achieve a loss effect.

[0095] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit the present invention. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a surface in-situ catalytic growth CNTs modified magnetic carbon nanofiber composite material, characterized by: The following steps are involved: S1. Preparation of electrospinning precursor solution: The metal salt and polyacrylonitrile are dissolved in a solvent under magnetic stirring at room temperature to prepare a homogeneous polyacrylonitrile electrospinning solution containing a metal salt precursor, and the solution is allowed to stand for degassing before use; The mass concentration of metal salt in the electrospinning solution is 1%~5%, and the concentration of polyacrylonitrile is 8%~12%; S2. Electrospinning preparation and pre-oxidation treatment of polyacrylonitrile fiber membrane: The polyacrylonitrile electrospinning solution prepared in step S1 was poured into a 20 mL syringe equipped with a stainless steel needle, and spun according to the set electrospinning process parameters to obtain a polyacrylonitrile fiber membrane containing metal salts. The solvent was dried to remove the solvent, and then the membrane was pre-oxidized at medium temperature in a muffle furnace. The electrospinning process parameters were as follows: the nanofibers were collected by tin foil during spinning, the high-voltage DC power supply was 15–20 kV, the distance between the needle tip and the tin foil collector was 15 cm, and the injection pump propulsion speed was 0.05 mL / min. -1 , drum speed is 300r·min -1 , relative humidity is 25% to 35% RH, and the temperature is set to 25±2℃; S3. Preparation of magnetic carbon nanofiber composites with in-situ catalytic growth of CNTs on the surface: The polyacrylonitrile fiber membrane after pre-oxidation treatment in the above step S2 is placed in a tubular furnace, a ceramic ark filled with melamine is placed upstream of the air flow, and a ceramic ark filled with polyacrylonitrile fiber membrane is placed downstream, wherein the mass ratio of melamine to polyacrylonitrile fiber is 1:1~1:3, and then high-temperature calcination at 700~900℃ is carried out in an inert atmosphere. After carbonization treatment, a magnetic carbon nanofiber composite material with in-situ catalytic growth of CNTs on the surface is finally obtained.

2. The preparation method according to claim 1, wherein: In step S1, the metal salt is one or more of ferric chloride, nickel chloride, cobalt chloride, ferric acetate, nickel acetate, cobalt acetate, ferric sulfate, nickel sulfate, cobalt sulfate, ferric nitrate, nickel nitrate, cobalt nitrate, ferric acetylacetonate, nickel acetylacetonate, and cobalt acetylacetonate.

3. The preparation method according to claim 2, wherein: Preferably, the metal salt is an acetylacetone complex salt.

4. The preparation method according to claim 1, wherein: In step S1, the solvent is one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO).

5. The preparation method according to claim 4, characterized in that: Preferably, the solvent is N,N-dimethylformamide.

6. The preparation method according to claim 1, wherein: In step S1, the standing and degassing time is 2 hours.

7. The preparation method according to claim 1, wherein: In step S2, the temperature of the pre-oxidation treatment is 200-300° C., and the treatment time is 1-3 hours.

8. The preparation method according to claim 1, wherein: In step S3, the high-temperature calcination time is 2 to 4 hours.

9. The preparation method according to claim 1, wherein: In the step S3, preferably, the calcination temperature is 700° C., the calcination time is 2 h, and the mass ratio of melamine to polyacrylonitrile fiber is 1:

3.

10. A magnetic carbon nanofiber composite material prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The microstructure of the magnetic carbon nanofiber composite material is a three-dimensional carbon nanofiber network.

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