Preparation method of FeCoNi@C / SiC-C fiber composite absorbing material

Abstract

The present invention discloses a preparation method of a FeCoNi@C / SiC-C fiber composite wave-absorbing material, which is achieved by the following technical scheme: first, polycarbosilane and refined asphalt are co-dissolved, and SiC-C fibers are prepared by spinning technology, and the SiC-C fibers are pre-treated as follows: degreasing → coarsening → sensitization → activation → reduction; then, a MOFs precursor is prepared using cobalt acetate, nickel nitrate, ferric nitrate nine hydrate, and dihydroxy terephthalic acid as raw materials; finally, the pre-treated SiC-C fibers are hydrothermally reacted with the MOFs precursor, and the FeCoNi@C / SiC-C fiber wave-absorbing material is formed by high-temperature treatment. The wave-absorbing material of the present invention has a lower dielectric constant and better impedance matching brought about by a special core / shell microstructure, so that more incident electromagnetic waves can effectively enter the interior of the material and be attenuated and absorbed, thereby obtaining a stronger and wider wave-absorbing effect.

Description

Technical Field

[0001] The present invention belongs to the field of wave-absorbing materials, and in particular relates to a method for preparing a FeCoNi@C / SiC-C fiber composite wave-absorbing material. Background Art

[0002] With the rapid development of electronic technology, electronic products radiate a large amount of electromagnetic waves of varying frequencies into space during operation, resulting in significant electromagnetic interference (EMI). To address these issues, absorbing materials are the ideal solution. Absorbing materials absorb electromagnetic wave energy incident on their surfaces and convert it into mechanical, electrical, thermal, or other forms of energy. Absorbing materials are primarily categorized as traditional and novel. Traditional absorbing materials, such as ferrite, barium titanate, metal micropowders, graphite, and silicon carbide, often suffer from shortcomings such as narrow absorption bandwidths and high density. New absorbing materials primarily include nanomaterials, chiral materials, conductive polymers, and circuit simulation absorbing materials. These materials, when combined with materials of varying properties, have significantly improved absorption bandwidth, compatibility, and strength. These materials are considered novel absorbing materials. In military applications, the United States, Russia, France, Germany, and other countries are researching nano-absorbing materials as the next generation of radar absorbing materials.

[0003] Absorbent materials have a wide range of applications. In the military, they can be used as stealth materials, such as aircraft skins and engine covers. For example, the F-117A Nighthawk stealth fighter's fuselage, wings, and vertical tail utilize extensive amounts of radar-stealing materials like fiberglass and carbon fiber. These materials redirect reflected radar waves, scattering them and making them difficult for enemy radar to detect. In civilian applications, they can be used as household safety devices around high-power radars, communications equipment, microwave heating devices, and other equipment to effectively prevent electromagnetic radiation or leakage from harming operators.

[0004] With the continuous development of radar detection technology, huge challenges have been posed to absorbing materials. There is an urgent need for multifunctional absorbing materials that combine the advantages of "thin thickness, light weight, wide frequency band, and strong absorption". However, at present, a single absorbing material cannot achieve many functions. Therefore, the research on composite absorbing materials has become a key development direction.

[0005] In the pursuit of "light weight", carbon fiber has performed excellently. Carbon fiber has the characteristics of low density, high strength, high specific modulus, high specific surface area, high electrical conductivity, good thermal conductivity and stability, making it widely used in electrode materials, adsorption materials, catalyst carriers, and absorbing materials. Carbon fiber absorbing materials have become one of the indispensable materials in modern science and technology. However, carbon fiber is a typical dielectric loss material with a high dielectric constant and very low magnetic permeability, resulting in poor electromagnetic matching. As a result, when used alone as an absorber, it generally has disadvantages such as a narrow absorption band and low absorption intensity. The magnetic permeability of carbon fiber can be improved by surface metallization or doping modification.

[0006] In order to make up for the shortcomings of carbon fiber's narrow absorption band and low absorption intensity, silicon carbide and magnetic metal particles have the functions of wide-band, multi-band absorption and strong wave absorption ability, and are excellent modifiers for carbon fiber. Summary of the Invention

[0007] In response to the problems of existing absorbing materials such as heavy weight, narrow frequency band and weak absorption capacity, the present invention aims to provide an absorbing material with light weight, wide frequency band and strong absorption capacity.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The present invention provides a preparation method of a FeCoNi@C / SiC-C fiber composite absorbing material, comprising the following preparation steps: Step 1: Preparation of SiC-C fiber: (1) polycarbosilane PCS and refined asphalt P are co-dissolved in an organic solvent in a certain weight ratio, and then the heat treatment system is evacuated and replaced with high-purity nitrogen, and then the temperature is raised under the protection of nitrogen to the boiling point of the solvent, and the solvent is distilled out, and after the solvent is distilled out, the solvent is heated under the protection of nitrogen. (2) the PCS-P precursor is placed in a spinning machine, filled with nitrogen for protection, heated to 130°C higher than the softening point of the raw material, and kept warm for 1 hour to fully melt and degas the PCS; then the temperature is lowered to 70°C, the melt flows through the filter screen and the spinneret, and is cooled and solidified in the air, and then the filament is wound on a take-up roller at a spinning speed of 200rpm-250rpm to obtain a raw yarn; (3) the raw yarn is stabilized and carbonized;

[0010] Step 2: SiC-C fiber pretreatment: degreasing → roughening → sensitization → activation → reduction;

[0011] Step 3: Preparation of MOFs precursor: Cobalt acetate, nickel nitrate, ferric nitrate nonahydrate, and dihydroxyterephthalic acid are dissolved in a mixture of N,N-dimethylformamide, deionized water, ethanol, and methanol using a solvothermal method. After the reaction is completed, the precursor solution is centrifuged, washed, and dried to obtain the precursor;

[0012] Step 4: The SiC-C fiber undergoes a hydrothermal reaction with the MOFs precursor, and then undergoes a high-temperature heat treatment in an inert gas to convert the MOFs into FeCoNi@C magnetic nanoparticles and deposit them on the surface of the SiC-C fiber to form a FeCoNi@C / SiC-C fiber material.

[0013] Preferably, the weight ratio of the polycarbosilane PCS to the refined asphalt P is 1:10-1:100.

[0014] Preferably, the organic solvent is xylene, and the boiling point of the solvent xylene is 140°C.

[0015] Preferably, the stabilization and carbonization treatment is to place the precursor into a tubular furnace, introduce air, and then heat it to 250°C-350°C for 4h-10h; then heat it to 1000°C-1200°C, pass nitrogen for protection, and keep it at this temperature for 1h-24h to perform carbonization treatment to obtain SiC-C fiber.

[0016] Preferably, the degreasing is performed by soaking the carbon fibers in a 20% potassium hydroxide solution at room temperature for 15 minutes, and then rinsing them with deionized water; the roughening is performed by soaking the carbon fibers in a 15% nitric acid solution for 15 minutes, and then rinsing them with deionized water; the sensitization is performed by immersing the roughened carbon fibers in a 37% hydrochloric acid solution (60 mL / L) and a SnCl2·2H2O 30 g / L sensitizing solution, stirring the carbon fibers mechanically at room temperature for 3-5 minutes, and then rinsing them with deionized water. The activation step is to immerse the sensitized carbon fiber in an activation solution of 0.5 g / L palladium chloride (PbCl2) and 10 mL / L 37% hydrochloric acid, stir it mechanically at room temperature for 3-5 minutes, and then rinse it with deionized water; the reduction step is to 10 g / L-30 g / L sodium hypophosphite, immerse the activated carbon fiber in the solution at room temperature for 1 minute, rinse it with deionized water, and then dry it in air at 60°C.

[0017] Preferably, the solvent thermal method is to raise the temperature of the mixed solution to 100° C.-300° C. for reaction, and the reaction time is 0.5 h-2 h.

[0018] Preferably, the hydrothermal reaction is to disperse the SiC-C fiber and the MOFs precursor in deionized water, raise the temperature to 200°C-350°C, and react for 1h-25h; the high-temperature heat treatment is carried out in an inert gas atmosphere, the heat treatment temperature is 500°C-900°C, and the time is 2h-4h.

[0019] Preferably, the inert gas is one of nitrogen, helium, neon, argon and krypton.

[0020] Preferably, the molar ratio of the cobalt acetate, nickel nitrate and ferric nitrate nonahydrate is 1:1:1.

[0021] Preferably, the weight ratio of the SiC-C fiber to the MOFs precursor is 20:1-50:1.

[0022] In the above technical solution, the technical effects and advantages provided by the present invention are:

[0023] (1) The present invention uses polycarbosilane and refined asphalt as raw materials, and prepares a SiC-C fiber substrate through spinning, stabilization and carbonization processes. The SiC-C fiber substrate has excellent characteristics such as light weight. At the same time, silicon carbide as a wide bandgap semiconductor material can provide excellent wave absorbing performance.

[0024] (2) The SiC-C fiber substrate of the present invention is simultaneously loaded with a metal material with MOFs as a precursor liquid. Due to its relatively low dielectric constant and better impedance matching brought about by the special core / shell microstructure, the FeCoNi@C / SiC-C fiber enables more incident electromagnetic waves to effectively enter the interior of the material and be attenuated and absorbed, thereby obtaining a stronger and wider absorbing effect, which has a wide range of application value. Implementation Method

[0025] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, 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 fall equally within the scope limited by the appended claims of the application.

[0026] Example 1

[0027] The present invention provides a preparation method of a FeCoNi@C / SiC-C fiber composite absorbing material, comprising the following preparation steps: Step 1: Preparation of SiC-C fiber: (1) polycarbosilane PCS and refined asphalt P are co-dissolved in xylene in a weight ratio of 1:10, and then the heat treatment system is evacuated and replaced with high-purity nitrogen, and then the temperature is raised under the protection of nitrogen to about 140°C, the boiling point of xylene, and the xylene is distilled out. After the xylene is distilled out, the xylene is cooled to room temperature under the protection of nitrogen to obtain a PCS-P precursor; (2) the PCS-P The precursor is loaded into the spinning machine, filled with nitrogen for protection, heated to 130℃ higher than the softening point of the raw material, and kept warm for 1 hour to fully melt and degas the PCS; then the temperature is lowered to 70℃, the melt flows through the filter screen and the spinneret, and is cooled and solidified in the air. The filaments are then wound on the take-up roller at a spinning speed of 200rpm to obtain the precursor; (3) the precursor is stabilized and carbonized: the precursor is placed in a tubular furnace, air is introduced, and then the temperature is raised to 250℃ and kept warm for 4 hours; then the temperature is raised to 1000℃, nitrogen is passed for protection, and the temperature is kept warm for 6 hours, and carbonization treatment is performed to obtain SiC-C fiber.

[0028] Step 2: SiC-C fiber pretreatment: Degreasing: Soak in 20% potassium hydroxide solution at room temperature for 15 minutes, then rinse with deionized water after taking out; Roughening: Soak in 15% nitric acid solution for 15 minutes, then rinse with deionized water after taking out; Sensitization: Immerse the roughened carbon fiber in 60 mL / L 37% hydrochloric acid and 30 g / L SnCl2·2H2O sensitizing solution, use mechanical stirring, the temperature is room temperature, the time is 3 minutes, then rinse with deionized water after taking out; Activation: Immerse the sensitized carbon fiber in 0.5 g / L palladium chloride (PbCl2) and 10 mL / L 37% hydrochloric acid activation solution, use mechanical stirring, the temperature is room temperature, the time is 3 minutes, then rinse with deionized water after taking out; Reduction: Immerse the activated carbon fiber in 10 g / L sodium hypophosphite solution, the temperature is room temperature, the stirring time is 1 minute, then rinse with deionized water after taking out, and then dry in air at 60 ° C.

[0029] Step 3: Preparation of MOFs precursor: 0.177 g of cobalt acetate, 0.183 g of nickel nitrate, 0.404 g of ferric nitrate nonahydrate, and 0.18 g of dihydroxyterephthalic acid were dissolved in a mixture consisting of 100 mL of N,N-dimethylformamide, 10 mL of deionized water, 10 mL of ethanol, and 10 mL of methanol. The temperature was raised to 150°C for reaction. The reaction time was 0.5 h. After the reaction was completed, the precursor solution was centrifuged, washed, and dried to obtain the precursor.

[0030] Step 4: SiC-C fiber and MOFs precursor are taken in a weight ratio of 20:1, put into deionized water solution, heated to 200°C, and reacted for 6 hours; after drying, heat treated in a neon atmosphere at a temperature of 500°C for 2 hours to convert MOFs into FeCoNi@C magnetic nanoparticles and deposit them on the surface of SiC-C fiber to form FeCoNi@C / SiC-C fiber material.

[0031] Example 2

[0032] The present invention provides a preparation method of a FeCoNi@C / SiC-C fiber composite absorbing material, comprising the following preparation steps: Step 1: Preparation of SiC-C fiber: (1) polycarbosilane PCS and refined asphalt P are co-dissolved in xylene in a weight ratio of 1:50, and then the heat treatment system is evacuated and replaced with high-purity nitrogen, and then the temperature is raised under the protection of nitrogen to about 140°C, the boiling point of xylene, and the xylene is distilled out. After the xylene is distilled out, the xylene is cooled to room temperature under the protection of nitrogen to obtain a PCS-P precursor; (2) the PCS-P precursor is The body is loaded into the spinning machine, filled with nitrogen for protection, heated to 130℃, which is higher than the softening point of the raw material, and kept warm for 1 hour to fully melt and degas the PCS; then the temperature is lowered to 70℃, the melt flows through the filter screen and the spinneret, and is cooled and solidified in the air. The filaments are then wound on the take-up roller at a spinning speed of 250rpm to obtain the precursor; (3) the precursor is stabilized and carbonized: the precursor is placed in a tubular furnace, air is introduced, and then the temperature is raised to 300℃ and kept warm for 8 hours; then the temperature is raised to 1100℃, nitrogen is passed for protection, and the temperature is kept warm for 12 hours, and carbonization treatment is performed to obtain SiC-C fiber.

[0033] Step 2: SiC-C fiber pretreatment: Degreasing: Soak in 20% potassium hydroxide solution at room temperature for 15 minutes, then rinse with deionized water after taking out; Roughening: Soak in 15% nitric acid solution for 15 minutes, then rinse with deionized water after taking out; Sensitization: Immerse the roughened carbon fiber in 60 mL / L 37% hydrochloric acid and 30 g / L SnCl2·2H2O sensitizing solution, use mechanical stirring, the temperature is room temperature, the time is 4 minutes, then rinse with deionized water after taking out; Activation: Immerse the sensitized carbon fiber in 0.5 g / L palladium chloride (PbCl2) and 10 mL / L 37% hydrochloric acid activation solution, use mechanical stirring, the temperature is room temperature, the time is 4 minutes, then rinse with deionized water after taking out; Reduction: Immerse the activated carbon fiber in 20 g / L sodium hypophosphite solution, the temperature is room temperature, the stirring time is 1 minute, then rinse with deionized water after taking out, and then dry in air at 60 ° C.

[0034] Step 3: Preparation of MOFs precursor: 0.177 g of cobalt acetate, 0.183 g of nickel nitrate, 0.404 g of ferric nitrate nonahydrate, and 0.18 g of dihydroxyterephthalic acid were dissolved in a mixture consisting of 100 mL of N,N-dimethylformamide, 10 mL of deionized water, 10 mL of ethanol, and 10 mL of methanol. The temperature was raised to 200°C for reaction. The reaction time was 1 hour. After the reaction was completed, the precursor solution was centrifuged, washed, and dried to obtain the precursor.

[0035] Step 4: SiC-C fiber and MOFs precursor were taken in a weight ratio of 40:1, put into deionized water solution, heated to 300°C, and reacted for 12 hours; after drying, heat treated in a nitrogen atmosphere at 700°C for 3 hours to convert MOFs into FeCoNi@C magnetic nanoparticles and deposited on the surface of SiC-C fiber to form FeCoNi@C / SiC-C fiber material.

[0036] Example 3

[0037] The present invention provides a preparation method of a FeCoNi@C / SiC-C fiber composite absorbing material, comprising the following preparation steps: Step 1: Preparation of SiC-C fiber: (1) polycarbosilane PCS and refined asphalt P are co-dissolved in xylene in a weight ratio of 1:100, and then the heat treatment system is evacuated and replaced with high-purity nitrogen, and then the temperature is raised under the protection of nitrogen to about 140°C, the boiling point of xylene, and the xylene is distilled out. After the xylene is distilled out, the xylene is cooled to room temperature under the protection of nitrogen to obtain a PCS-P precursor; (2) the PCS-P precursor is The body is loaded into the spinning machine, filled with nitrogen for protection, heated to 130℃ higher than the softening point of the raw material, and kept warm for 1 hour to fully melt and degas the PCS; then the temperature is lowered to 70℃, the melt flows through the filter screen and the spinneret, and is cooled and solidified in the air. The filaments are then wound on the take-up roller at a spinning speed of 200rpm to obtain the precursor; (3) the precursor is stabilized and carbonized: the precursor is placed in a tubular furnace, air is introduced, and then the temperature is raised to 350℃ and kept warm for 10 hours; then the temperature is raised to 1200℃, nitrogen is passed for protection, and the temperature is kept warm for 24 hours, and carbonization treatment is performed to obtain SiC-C fiber.

[0038] Step 2: SiC-C fiber pretreatment: Degreasing: Soak in 20% potassium hydroxide solution at room temperature for 15 minutes, then rinse with deionized water after taking out; Roughening: Soak in 15% nitric acid solution for 15 minutes, then rinse with deionized water after taking out; Sensitization: Immerse the roughened carbon fiber in 60 mL / L 37% hydrochloric acid and 30 g / L SnCl2·2H2O sensitizing solution, use mechanical stirring, the temperature is room temperature, the time is 5 minutes, then rinse with deionized water after taking out; Activation: Immerse the sensitized carbon fiber in 0.5 g / L palladium chloride (PbCl2) and 10 mL / L 37% hydrochloric acid activation solution, use mechanical stirring, the temperature is room temperature, the time is 5 minutes, then rinse with deionized water after taking out; Reduction: Immerse the activated carbon fiber in 30 g / L sodium hypophosphite solution, the temperature is room temperature, the stirring time is 1 minute, then rinse with deionized water after taking out, and then dry in air at 60 ° C.

[0039] Step 3: Preparation of MOFs precursor: 0.177 g of cobalt acetate, 0.183 g of nickel nitrate, 0.404 g of ferric nitrate nonahydrate, and 0.18 g of dihydroxyterephthalic acid were dissolved in a mixture consisting of 100 mL of N,N-dimethylformamide, 10 mL of deionized water, 10 mL of ethanol, and 10 mL of methanol. The temperature was raised to 300°C for reaction for 2 h. After the reaction was completed, the precursor solution was centrifuged, washed, and dried to obtain the precursor.

[0040] Step 4: Take SiC-C fiber and MOFs precursor in a weight ratio of 50:1, put them into deionized water solution, heat to 350°C for 24 hours, dry, and heat treat in a nitrogen atmosphere at 900°C for 4 hours to convert MOFs into FeCoNi@C magnetic nanoparticles and deposit them on the surface of SiC-C fiber to form FeCoNi@C / SiC-C fiber material.

[0041] Comparative Example 1

[0042] This comparative example is the SiC-C fiber in Example 1 that has been carbonized.

[0043] Comparative Example 2

[0044] This comparative example is the SiC-C fiber in Example 2 that has been carbonized.

[0045] Comparative Example 3

[0046] This comparative example is the SiC-C fiber in Example 3 that has been carbonized.

[0047] The absorbing material was tested for its absorbing performance according to GJB2038-94, "Test Method for Reflectivity of Radar Absorbing Materials," using the "RAM Reflectivity Bow Test." The carbon fiber tow produced by the present invention was woven into cloth and cut into several squares larger than 180 mm. The squares were coated with epoxy resin and a curing agent, then stacked and cured under pressure to produce carbon fiber samples measuring 180 mm in length and width and 5 mm in thickness. The reflectivity was then tested within the 2-18 GHz microwave frequency range.

[0048] Table 1 Test results of the microwave absorption properties of materials obtained under different process conditions

[0049]

[0050] The test data in Table 1 demonstrates that the FeCoNi@C / SiC-C fiber absorber material of the present invention exhibits a wide absorption bandwidth. For example, in Example 1, the absorption bandwidth below -10 dB reaches 11.66 GHz, and the maximum absorption peak reaches -19.56 dB. These improvements significantly improve the absorption bandwidth compared to materials without the addition of magnetic particles.

[0051] In summary, the FeCoNi@C / SiC-C fiber material, loaded with metal particles from MOF precursors, offers excellent properties such as lightweight. Silicon carbide, as a wide-bandgap semiconductor reinforcement, provides superior microwave absorption. Furthermore, its relatively low dielectric constant and unique core / shell microstructure provide improved impedance matching, allowing more incident electromagnetic waves to effectively enter the material and be attenuated and absorbed, resulting in a stronger and broader microwave absorption effect, promising broad applications.

[0052] Finally, it should be noted that the above description is only a preferred embodiment of the present invention. Under the guidance of the present invention, those skilled in the art can make various similar changes without violating the purpose and claims of the present invention, and such changes all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a FeCoNi@C / SiC-C fiber composite absorbing material, characterized in that: The method comprises the following preparation steps: Step 1: Preparation of SiC-C fiber: (1) polycarbosilane PCS and refined asphalt P are co-dissolved in an organic solvent in a certain weight ratio, wherein the weight ratio of the polycarbosilane PCS to the refined asphalt P is 1:10-1:100, and then the heat treatment system is evacuated and replaced with high-purity nitrogen, and then the temperature is raised under the protection of nitrogen to the boiling point of the solvent, and the solvent is distilled out, and after the solvent is distilled out, the solvent is cooled to room temperature under the protection of nitrogen to obtain a PCS-P precursor; (2) the PCS- The P precursor is loaded into the spinning machine, filled with nitrogen for protection, and heated to 130°C, which is higher than the softening point of the raw material, and kept warm for 1 hour to fully melt and degas the PCS; then the temperature is lowered to 70°C, and the melt flows through the filter screen and the spinneret, and is cooled and solidified in the air. The filaments are then wound on the take-up roller at a spinning speed of 200rpm-250rpm to obtain the precursor; (3) the precursor is stabilized and carbonized, and the stabilization treatment is to place the precursor in a tubular furnace, let air in, and then heat it to 250°C-350°C, and keep it warm for 4h-10h; Step 2: SiC-C fiber pretreatment: degreasing → roughening → sensitization → activation → reduction; the degreasing is to soak in a 20% potassium hydroxide solution at room temperature for 15 minutes, and then rinse with deionized water; the roughening is to soak in a 15% nitric acid solution for 15 minutes, and then rinse with deionized water; the sensitization is to immerse the roughened carbon fiber in a 37% hydrochloric acid 60mL / L, SnCl2·2H2O30g / L sensitizing solution, using mechanical stirring, the temperature is room temperature, and the time is 3min-5mi n, and rinsed with deionized water after being taken out; the activation is to immerse the sensitized carbon fiber in 0.5g / L palladium chloride (PbCl2) and 10mL / L activation solution of 37% hydrochloric acid, using mechanical stirring, the temperature is room temperature, the time is 3min-5min, and then rinsed with deionized water after being taken out; the reduction is 10g / L-30g / L sodium hypophosphite, immersing the activated carbon fiber in the solution, the temperature is room temperature, the stirring time is 1min, and then rinsed with deionized water after being taken out, and then dried in air at 60°C; Step 3: Preparation of MOFs precursor: Cobalt acetate, nickel nitrate, ferric nitrate nonahydrate, and dihydroxyterephthalic acid are dissolved in a mixture of N,N-dimethylformamide, deionized water, ethanol, and methanol using a solvothermal method. After the reaction is completed, the precursor solution is centrifuged, washed, and dried to obtain the precursor; Step 4: The SiC-C fiber undergoes a hydrothermal reaction with the MOFs precursor, and then undergoes a high-temperature heat treatment in an inert gas to convert the MOFs into FeCoNi@C magnetic nanoparticles and deposit them on the surface of the SiC-C fiber to form a FeCoNi@C / SiC-C fiber material.

2. The method for preparing the FeCoNi@C / SiC-C fiber composite absorbing material according to claim 1, characterized in that: The organic solvent is xylene, and the boiling point of the xylene solvent is 140°C.

3. The method for preparing the FeCoNi@C / SiC-C fiber composite absorbing material according to claim 1, characterized in that: The carbonization treatment is to heat the temperature to 1000-1200° C. after the stabilization treatment, pass nitrogen for protection, and keep the temperature for 1 hour to 24 hours to perform carbonization treatment to obtain SiC-C fibers.

4. The method for preparing the FeCoNi@C / SiC-C fiber composite absorbing material according to claim 1, characterized in that: The solvent thermal method is to raise the temperature of the mixed solution to 100° C.-300° C. for reaction, and the reaction time is 0.5 h-2 h.

5. The method for preparing the FeCoNi@C / SiC-C fiber composite absorbing material according to claim 1, characterized in that: The hydrothermal reaction is to disperse the SiC-C fiber and the MOFs precursor in deionized water, raise the temperature to 200°C-350°C, and react for 1h-25h; the high-temperature heat treatment is carried out in an inert gas atmosphere at a temperature of 500°C-900°C and for 2h-4h.

6. The method for preparing the FeCoNi@C / SiC-C fiber composite absorbing material according to claim 1, characterized in that: The inert gas is one of nitrogen, helium, neon, argon and krypton.

7. The method for preparing the FeCoNi@C / SiC-C fiber composite absorbing material according to claim 1, characterized in that: The molar ratio of the cobalt acetate, nickel nitrate and ferric nitrate nonahydrate is 1:1:

1.

8. The method for preparing the FeCoNi@C / SiC-C fiber composite absorbing material according to claim 1, characterized in that: The weight ratio of the SiC-C fiber to the MOFs precursor is 20:1-50:1.

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