CoNi alloy loaded nitrogen-doped magnetic carbon aerogel as well as preparation method and application thereof

Abstract

The invention discloses CoNi alloy loaded nitrogen-doped magnetic carbon aerogel as well as a preparation method and application thereof, according to the method, a directional freezing method, a pyrolysis method and a solvothermal method are adopted to load CoNi on biomass derived carbon aerogel in situ, and a honeycomb-like magnetic nitrogen-doped carbon aerogel composite wave-absorbing material loaded with CoNi and a preparation method of the CoNi-loaded honeycomb-like magnetic nitrogen-doped carbon aerogel composite wave-absorbing material are constructed. Through the dielectric loss of the carbon aerogel, the CoNi alloy particles in the carbon aerogel provide magnetic loss, and the dielectric-electromagnetic synergistic effect is beneficial to optimization of impedance matching of the wave-absorbing material. Meanwhile, the multiple reflection and scattering of the electromagnetic waves in the directional honeycomb structure also help the dissipation of the electromagnetic waves.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials technology, and relates to a CoNi alloy-supported nitrogen-doped magnetic carbon aerogel, its preparation method and application. Background Technology

[0002] In today's rapidly developing information age, advanced electromagnetic wave technology is widely used in numerous fields such as communications, medicine, and industry, greatly satisfying people's increasingly diverse needs and becoming a key force driving social progress. On a smaller scale, with the widespread adoption of electronic products, from everyday items like mobile phones and computers to various electronic devices in industrial production, electromagnetic waves are ubiquitous. However, the accompanying problem of electromagnetic pollution is becoming increasingly prominent, posing potential harm to the human nervous and immune systems, affecting people's health, and interfering with the normal operation of high-precision electronic equipment, reducing its performance and stability. This has become a pressing practical problem that needs to be solved. Under these circumstances, developing materials with "thin, light, wide, and strong" electromagnetic wave absorption properties has become a focus of scientific research. Such materials can effectively reduce secondary electromagnetic pollution, protecting human health and the safety of high-precision electronic equipment.

[0003] Among the current research advancements in technology, carbon aerogels stand out due to their unique structural and performance advantages. Their interconnected porous structure, high specific surface area, low density, and multifunctionality, such as thermal insulation and flame retardancy, enable them to exhibit excellent electromagnetic wave absorption performance, opening up new directions for microwave absorbing material research. In particular, biomass-derived carbon aerogels have attracted significant attention in the field of microwave absorbing materials due to the sustainable source, tunable morphology, and cost-effective preparation process of biomass raw materials. After high-temperature carbonization, biomass raw materials form a three-dimensional carbon framework rich in micropores and mesopores, possessing excellent high specific surface area and abundant defect structures. This significantly enhances dielectric polarization relaxation loss and conductivity loss effects, providing a unique precursor platform for the design of lightweight magnetic carbon-based microwave absorbing materials.

[0004] However, many problems still exist in this field. While single-carbon materials have certain advantages, they suffer from excessively high conductivity. This high conductivity forces the material to rely solely on conductive loss as a single loss mechanism, leading to impedance mismatch. In practical applications, this means that electromagnetic waves are difficult to effectively penetrate and be absorbed within the material; most electromagnetic waves are reflected at the surface, failing to meet the stringent requirements for electromagnetic wave absorption performance and limiting its application in a wider range of fields. Further research and innovation are urgently needed to find effective solutions. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a CoNi alloy-supported nitrogen-doped magnetic carbon aerogel, its preparation method, and its application. This solves the technical problem in the prior art where single carbon materials, due to their high conductivity, rely solely on a single conductive loss mechanism, leading to impedance mismatch and causing electromagnetic waves to be reflected at the surface rather than effectively absorbed, thus failing to meet the requirements for electromagnetic wave absorption performance.

[0006] This invention is achieved through the following technical solution: A method for preparing CoNi alloy-supported nitrogen-doped magnetic carbon aerogel includes the following steps: S1: Add crosslinking aid to the aqueous solution of biomass precursor, stir to form biomass precursor suspension, and subject the biomass precursor suspension to directional freezing and freeze-drying treatment in sequence to obtain biomass aerogel precursor. S2: The biomass aerogel precursor is placed in a nitrogen or inert atmosphere and subjected to heat treatment to obtain biomass-derived carbon aerogel. S3: Add the reducing agent to an organic solution containing cobalt salt and nickel salt, stir evenly to obtain a metal salt solution, add the biomass-derived carbon aerogel to the metal salt solution, and carry out a vacuum solvothermal reaction to obtain the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel.

[0007] Preferably, in step S1, the ratio of the crosslinking aid to the biomass precursor is (0.2-0.5) mL:(0.2-0.5) g.

[0008] Preferably, in step S1, the ratio of biomass precursor to water in the aqueous solution of the biomass precursor is (0.2-0.5) g:(10-40) mL.

[0009] Preferably, in step S1, the freeze-drying time is 30-70 h.

[0010] Preferably, in step S2, during the heat treatment process, the heating rate is 2-10 ℃ / min, the holding time is 1-6h, and the holding temperature is 600-1000 ℃.

[0011] Preferably, in step S3, the ratio of the amount of cobalt salt, nickel salt and organic solvent is (0.1-1) g:(0.1-1) g:(20-50) mL.

[0012] Preferably, in step S3, the vacuum solvothermal reaction specifically involves: placing the biomass-derived carbon aerogel and metal salt solution in a stainless steel reactor liner and performing multiple vacuum treatments. During the vacuum treatment, the vacuum degree is 0.6-1 atmosphere, the treatment time for each treatment is 1-4 min, and the number of vacuum treatments is 1-3 times.

[0013] Preferably, in step S3, the temperature of the solvothermal reaction is 110-150℃ and the time is 2-10 h.

[0014] A CoNi alloy-supported nitrogen-doped magnetic carbon aerogel was prepared by the method described above.

[0015] The above-mentioned application of a CoNi alloy-supported nitrogen-doped magnetic carbon aerogel in the field of electromagnetic shielding.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: The purpose of this invention is to provide a CoNi alloy-loaded nitrogen-doped magnetic carbon aerogel and its preparation method. First, in step S1, a crosslinking aid is added to an aqueous solution of a biomass precursor, followed by directional freezing and freeze-drying to obtain a biomass aerogel precursor. This process constructs a honeycomb-like porous structure, providing conditions for multiple reflections and scattering of electromagnetic waves, thus contributing to electromagnetic wave dissipation. Next, in step S2, the biomass aerogel precursor is heat-treated in a nitrogen or inert atmosphere to obtain a biomass-derived carbon aerogel. Its high specific surface area and abundant defect structure enhance dielectric polarization relaxation loss. Finally, in step S3, the biomass-derived carbon aerogel is added to an organic solution containing cobalt salts, nickel salts, and a reducing agent, and a vacuum solvothermal reaction is performed to in-situ load CoNi alloy particles. These particles provide magnetic loss, which synergistically works with the dielectric loss of the carbon aerogel, optimizing impedance matching and solving the impedance matching imbalance problem caused by the excessive conductivity of single carbon materials. This allows electromagnetic waves to effectively penetrate the material and be absorbed, rather than being reflected at the surface, thereby significantly improving electromagnetic wave absorption performance and meeting stringent requirements.

[0017] Furthermore, in step S1, the ratio of the crosslinking aid to the biomass precursor is (0.2-0.5) mL:(0.2-0.5) g. This ratio allows the crosslinking aid to fully exert its effect, effectively promoting crosslinking between biomass precursor molecules, forming a stable and uniform biomass precursor suspension, providing a good foundation for subsequent directional freezing and freeze-drying processes, and helping to construct a well-structured honeycomb-like porous structure, enhancing the multiple reflections and scattering of electromagnetic waves within the material, and improving electromagnetic wave absorption performance.

[0018] Furthermore, in step S1, the ratio of biomass precursor to water in the aqueous solution of the biomass precursor is (0.2-0.5) g:(10-40) mL. This ratio ensures that the biomass precursor is fully dissolved and dispersed in the water to form a uniform solution, which facilitates subsequent interaction with crosslinking aids and directional freezing operations. This is beneficial for forming a high-quality biomass aerogel precursor, thereby improving the electromagnetic wave absorption performance of the final product.

[0019] Furthermore, in step S1, the freeze-drying time is 30-70 h. A suitable long freeze-drying time can fully remove the water in the biomass precursor suspension, avoid structural collapse or unevenness caused by residual water, and ensure that the biomass aerogel precursor has a complete honeycomb-like porous structure, laying the foundation for the subsequent preparation of high-performance electromagnetic wave absorbing materials.

[0020] Furthermore, in step S2, during the heat treatment process, the heating rate is 2-10 ℃ / min, the holding time is 1-6 h, and the holding temperature is 600-1000 ℃. A suitable heating rate can prevent the biomass aerogel precursor from generating internal stress due to excessively rapid heating, which could lead to structural damage. Appropriate holding time and temperature can enable the biomass to be fully carbonized, forming a biomass-derived carbon aerogel with a high specific surface area and abundant defect structure, thereby enhancing the dielectric polarization relaxation loss and conductivity loss effect and optimizing the electromagnetic wave absorption performance.

[0021] Furthermore, in step S3, the ratio of cobalt salt, nickel salt, and organic solvent is (0.1-1) g:(0.1-1) g:(20-50) mL. This ratio ensures that the cobalt salt and nickel salt are fully dissolved and dispersed in the organic solvent to form a uniform metal salt solution. This facilitates the subsequent reaction with biomass-derived carbon aerogel, uniformly loading CoNi alloy particles onto the carbon aerogel, providing stable magnetic loss, and working synergistically with the dielectric loss of the carbon aerogel to optimize impedance matching.

[0022] Furthermore, in step S3, during the vacuum solvothermal reaction, specifically: the biomass-derived carbon aerogel and the metal salt solution are placed in a stainless steel reactor liner and subjected to multiple vacuum treatments. During the vacuum treatment, the vacuum degree is 0.6-1 atmosphere, the treatment time for each treatment is 1-4 minutes, and the number of vacuum treatments is 1-3 times. Multiple vacuum treatments can effectively remove gases from the reaction system, reduce bubble generation, allow the metal salt solution to better wet the biomass-derived carbon aerogel, promote the in-situ loading of CoNi alloy particles on the carbon aerogel, improve the uniformity and stability of the loading, and enhance the magnetic loss effect.

[0023] Furthermore, in step S3, the temperature of the solvothermal reaction is 110-150℃ and the time is 2-10 h. The appropriate reaction temperature and time can enable the cobalt salt and nickel salt to fully react to generate CoNi alloy particles and firmly load them on the biomass-derived carbon aerogel, forming a stable CoNi alloy-loaded nitrogen-doped magnetic carbon aerogel structure, ensuring that the material has excellent electromagnetic wave absorption performance. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 The XRD patterns are of nitrogen-doped magnetic carbon aerogels supported on CoNi alloys prepared in Examples 3, 4 and 5 of this invention. Figure 2 This is a SEM image of the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel prepared in Example 4 of this invention. Figure 3 The images show the reflection loss diagrams of the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel prepared in Example 3 of this invention. (a) is a two-dimensional reflection loss diagram, and (b) is a contour plot of the three-dimensional reflection loss diagram.

[0026] Figure 4 The images show the reflection loss diagrams of the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel prepared in Example 4 of this invention. (a) is a two-dimensional reflection loss diagram, and (b) is a contour plot of the three-dimensional reflection loss diagram.

[0027] Figure 5 The images show the reflection loss diagrams of the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel prepared in Example 5 of this invention. (a) is a two-dimensional reflection loss diagram, and (b) is a contour plot of the three-dimensional reflection loss diagram.

[0028] Figure 6 Impedance matching diagram of the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel prepared in Example 4 of this invention.

[0029] Figure 7 This is an electron image of the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel prepared in Example 4 of this invention being adsorbed by a magnet. Detailed Implementation

[0030] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0031] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0032] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0033] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0034] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0035] This invention provides a method for preparing nitrogen-doped magnetic carbon aerogel supported on a CoNi alloy, comprising the following steps: S1: Add crosslinking aid to the aqueous solution of biomass precursor, stir to form biomass precursor suspension, and subject the biomass precursor suspension to directional freezing and freeze-drying treatment in sequence to obtain biomass aerogel precursor. The biomass precursor is one of cellulose, glucose, and chitosan; The crosslinking aid is either citric acid or acetic acid; The ratio of the crosslinking aid to the biomass precursor is (0.2-0.5) mL:(0.2-0.5) g; the ratio of the biomass precursor to water in the aqueous solution of the biomass precursor is (0.2-0.5) g:(10-40) mL. The freeze-drying process takes 30-70 hours. S2: The biomass aerogel precursor is placed in a nitrogen or inert atmosphere and subjected to heat treatment to obtain biomass-derived carbon aerogel. During the heat treatment process, the heating rate is 2-10 ℃ / min, the holding time is 1-6 h, and the holding temperature is 600-1000 ℃; The inert atmosphere is argon; S3: Add the reducing agent to an organic solution containing cobalt salt and nickel salt, stir evenly to obtain a metal salt solution, add the biomass-derived carbon aerogel to the metal salt solution, and carry out a vacuum solvothermal reaction to obtain the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel.

[0036] The cobalt salt is one of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt acetate tetrahydrate, and cobalt sulfate heptahydrate; the nickel salt is one of nickel nitrate hexahydrate, nickel chloride hexahydrate, nickel acetate tetrahydrate, and nickel sulfate heptahydrate; the reducing agent is at least one of sodium borohydride, sodium hypophosphite, potassium borohydride, and hydrazine hydrate. In organic solutions containing cobalt and nickel salts, the organic solvent is at least one of propylene glycol, butanediol, glycerol, and ethylene glycol. The ratio of cobalt salt, nickel salt and organic solvent used is (0.1-1) g:(0.1-1) g:(20-50) mL; The amount of reducing agent added is 2-5 mL; The vacuum solvothermal reaction is specifically carried out as follows: biomass-derived carbon aerogel and metal salt solution are placed in a stainless steel reactor liner and subjected to multiple vacuum treatments. During the vacuum treatment, the vacuum degree is 0.6-1 atmosphere, the treatment time is 1-4 min, and the number of vacuum treatments is 1-3 times; the temperature of the solvothermal reaction is 110-150℃, and the time is 2-10 h.

[0037] This invention employs directional freezing, pyrolysis, and solvothermal methods to in-situ load CoNi onto biomass-derived carbon aerogel, constructing a CoNi alloy-loaded, honeycomb-like magnetic carbon aerogel. Through the dielectric loss of the carbon aerogel, the CoNi alloy particles within it provide magnetic loss; this dielectric-electromagnetic synergy helps optimize the impedance matching of the absorbing material. Simultaneously, the multiple reflections and scattering of electromagnetic waves in the directional honeycomb structure also aid in electromagnetic wave dissipation. This invention focuses on innovation in electromagnetic wave absorbing materials, innovatively loading CoNi alloy particles in-situ onto nitrogen-doped biomass-derived carbon aerogel using directional freezing, pyrolysis, and solvothermal methods, successfully constructing a novel CoNi alloy-loaded nitrogen-doped magnetic carbon aerogel structure. In this structure, the carbon aerogel acts as a dielectric loser, while the CoNi alloy particles provide magnetic loss; the two synergistically optimize the impedance matching of the absorbing material. Simultaneously, the directional honeycomb structure promotes multiple reflections and scattering of electromagnetic waves, further contributing to electromagnetic wave dissipation. Furthermore, the fabrication process of this invention is simple, environmentally friendly, and feasible for mass production. The prepared CoNi alloy-supported nitrogen-doped magnetic carbon aerogel exhibits excellent electromagnetic wave absorption performance due to its unique advantages, and has broad application prospects in the field of military and aerospace electromagnetic wave absorption.

[0038] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0039] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0040] Example 1 A method for preparing CoNi alloy-supported nitrogen-doped magnetic carbon aerogel includes the following steps: (1) Dissolve 0.2 g of cellulose in 10 mL of deionized water and stir to dissolve.

[0041] (2) Add 0.2 mL of citric acid to the above solution and keep stirring to form a homogeneous solution.

[0042] (3) Transfer the above homogeneous solution into a custom mold, place the mold on a copper column in liquid nitrogen for directional freezing, and freeze-dry the frozen sample for 40 h.

[0043] (4) The obtained sample was kept at 600 °C for 1 h under nitrogen protection, with a heating rate of 5 °C / min, to obtain biomass-derived carbon aerogel.

[0044] (5) Add 3 mmol of cobalt nitrate hexahydrate and 3 mmol of nickel nitrate hexahydrate solution to 30 mL of propylene glycol. After dissolving completely, add 3 mL of sodium borohydride and stir evenly to form a dispersion solution. Then add biomass-derived carbon aerogel to the above solution and mix evenly. Then place the final solution into the liner of a stainless steel reactor for vacuum treatment. During vacuum treatment, the vacuum degree is 0.6-1 atmosphere, the treatment time is 1 min, the number of times is 1, the solvothermal reaction is 110 °C, and the reaction time is 3 h. CoNi alloy supported nitrogen-doped magnetic carbon aerogel can be obtained.

[0045] Example 2 A method for preparing CoNi alloy-supported nitrogen-doped magnetic carbon aerogel includes the following steps: (1) Dissolve 0.4 g of glucose in 30 mL of deionized water and stir to dissolve.

[0046] (2) Add 0.4 mL of citric acid to the above solution and keep stirring to form a homogeneous solution.

[0047] (3) Transfer the above homogeneous solution into a custom mold, place the mold on a copper column in liquid nitrogen for directional freezing, and freeze-dry the frozen sample for 70 h.

[0048] (4) The obtained sample was kept at 1000 °C for 2 h under nitrogen protection, with a heating rate of 10 °C / min, to obtain biomass-derived carbon aerogel.

[0049] (5) Add 5 mmol of cobalt nitrate hexahydrate and 5 mmol of nickel nitrate hexahydrate solution to 50 mL of butanediol. After dissolving completely, add 5 mL of sodium hypophosphite and stir evenly to form a dispersion solution. Then add biomass-derived carbon aerogel to the above solution and mix evenly. Then place the final solution into the liner of a stainless steel reactor for vacuum treatment. During vacuum treatment, the vacuum degree is 0.6-1 atmosphere, the treatment time is 4 min, the number of treatments is 3, the solvothermal reaction is 150 °C, and the reaction time is 10 h. CoNi alloy-supported nitrogen-doped magnetic carbon aerogel can be obtained.

[0050] Example 3 A method for preparing CoNi alloy-supported nitrogen-doped magnetic carbon aerogel includes the following steps: (1) Dissolve 0.3 g of chitosan in 15 mL of deionized water and stir to dissolve.

[0051] (2) Add 0.3 mL of acetic acid to the above solution and keep stirring to form a homogeneous solution.

[0052] (3) Transfer the above homogeneous solution into a custom mold, place the mold on a copper column in liquid nitrogen for directional freezing, and freeze-dry the frozen sample for 60 hours.

[0053] (4) The obtained sample was kept at 900 °C for 2 h under argon protection, with a heating rate of 2 °C / min, to obtain biomass-derived carbon aerogel.

[0054] (5) Add 1 mmol cobalt chloride hexahydrate and 1 mmol nickel chloride hexahydrate to 40 mL ethylene glycol. After dissolving completely, add 4 mL hydrazine hydrate and stir until a dispersion solution is formed. Then add biomass-derived carbon aerogel to the above solution and mix evenly. Then place the final solution into the liner of a stainless steel reactor for vacuum treatment. During vacuum treatment, the vacuum degree is 0.6-1 atmosphere, the treatment time is 2 min, the number of treatments is 3, the solvothermal reaction is 140 °C, and the reaction time is 6 h. CoNi alloy-supported nitrogen-doped magnetic carbon aerogel can be obtained.

[0055] Example 4 A method for preparing CoNi alloy-supported nitrogen-doped magnetic carbon aerogel includes the following steps: (1) Dissolve 0.3 g of chitosan in 15 mL of deionized water and stir to dissolve.

[0056] (2) Add 0.3 mL of acetic acid to the above solution and keep stirring to form a homogeneous solution.

[0057] (3) Transfer the above homogeneous solution into a custom mold, place the mold on a copper column in liquid nitrogen for directional freezing, and freeze-dry the frozen sample for 60 hours.

[0058] (4) The obtained sample was kept at 900 °C for 2 h under argon protection, with a heating rate of 2 °C / min, to obtain biomass-derived carbon aerogel.

[0059] (5) Add 2 mmol cobalt chloride hexahydrate and 2 mmol nickel chloride hexahydrate solutions to 40 mL ethylene glycol. After dissolving completely, add 4 mL hydrazine hydrate and stir until a dispersion is formed. Then add biomass-derived carbon aerogel to the above solution and mix evenly. Then place the final solution into the liner of a stainless steel reactor for vacuum treatment. During vacuum treatment, the vacuum degree is 0.6-1 atmosphere, the treatment time is 2 min, the number of treatments is 3, the solvothermal reaction is 140 °C, and the reaction time is 6 h. CoNi alloy-supported nitrogen-doped magnetic carbon aerogel can be obtained.

[0060] Example 5 A method for preparing CoNi alloy-supported nitrogen-doped magnetic carbon aerogel includes the following steps: (1) Dissolve 0.3 g of chitosan in 15 mL of deionized water and stir to dissolve.

[0061] (2) Add 0.3 mL of acetic acid to the above solution and keep stirring to form a homogeneous solution.

[0062] (3) Transfer the above homogeneous solution into a custom mold, place the mold on a copper column in liquid nitrogen for directional freezing, and freeze-dry the frozen sample for 60 hours.

[0063] (4) The obtained sample was kept at 900 °C for 2 h under argon protection, with a heating rate of 2 °C / min, to obtain biomass-derived carbon aerogel.

[0064] (5) Add 4 mmol of cobalt chloride hexahydrate and 4 mmol of nickel chloride hexahydrate solution to 40 mL of ethylene glycol. After dissolving completely, add 4 mL of hydrazine hydrate and stir evenly to form a dispersion solution. Then add biomass-derived carbon aerogel to the above solution and mix evenly. Then put the final solution into the liner of a stainless steel reactor for vacuum treatment. During vacuum treatment, the vacuum degree is 0.6-1 atmosphere, the treatment time is 2 min, the number of treatments is 3, the solvothermal reaction is 140 °C, and the reaction time is 6 h. CoNi alloy supported nitrogen-doped magnetic carbon aerogel can be obtained.

[0065] The CoNi alloy-supported nitrogen-doped magnetic carbon aerogels prepared in Examples 1-5 all exhibit good electromagnetic wave absorption performance. The following description uses the CoNi alloy-supported nitrogen-doped magnetic carbon aerogels prepared in Examples 3, 4, and 5 as examples.

[0066] Figure 1 The images show the XRD patterns of the CoNi alloy-supported nitrogen-doped magnetic carbon aerogels prepared in Examples 3, 4, and 5 of this invention. The XRD patterns of the magnetic carbon aerogels were obtained by X-ray diffraction analysis, as shown below. Figure 1 As shown, the peaks at 44.52°, 52.04°, and 76.28° belong to the (111), (200), and (220) crystal planes, corresponding to the face-centered cubic phase of the CoNi metallic alloy. In particular, it is clearly observed that the broad peak at approximately 23° belongs to the amorphous state of biomass-derived carbon. In summary, the successful preparation of nitrogen-doped magnetic carbon aerogels supported on CoNi alloys is demonstrated.

[0067] Figure 2 The image shows a SEM image of the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel prepared in Example 4 of this invention. It is evident that the carbon aerogel, prepared via directional freezing, pyrolysis, and solvothermal methods, successfully produced a magnetic carbon aerogel with a honeycomb-like structure. Figure 2 As shown in a. And from Figure 2 Scanning at higher magnification reveals that the biomass-derived carbon material framework contains uniformly loaded magnetic CoNi alloy particles. This oriented honeycomb structure facilitates various reflections and scatterings of electromagnetic waves, and the biomass-derived carbon on it increases the material's conductivity, thereby enhancing conductivity loss.

[0068] Figure 3 The images show the reflection loss diagrams of the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel prepared in Example 3 of this invention. (a) is a two-dimensional reflection loss diagram, and (b) is a contour plot of the three-dimensional reflection loss diagram. The reflection loss was calculated based on transmission line theory by measuring the electromagnetic parameters of the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel. Figure 3As shown, CoNi alloy-supported nitrogen-doped magnetic carbon aerogels exhibit excellent electromagnetic wave absorption properties. Furthermore, according to... Figure 3 (b) It can be seen that the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel has the minimum reflection loss value of -29.8 dB at 3.53 mm and the maximum absorption bandwidth of 4.96 GHz when the matching thickness is 1.53 mm. It can be seen that the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel has achieved excellent electromagnetic wave absorption effect through structural design.

[0069] Figure 4 The images show the reflection loss diagrams of the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel prepared in Example 4 of this invention. (a) is a two-dimensional reflection loss diagram, and (b) is a contour plot of the three-dimensional reflection loss diagram. The reflection loss was calculated based on transmission line theory by measuring the electromagnetic parameters of the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel. Figure 4 As shown, CoNi alloy-supported nitrogen-doped magnetic carbon aerogels exhibit excellent electromagnetic wave absorption properties. Furthermore, according to... Figure 4 (b) It can be seen that the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel has the minimum reflection loss value of -56.67dB at 3.67mm and the maximum absorption bandwidth of 6GHz when the matching thickness is 1.74mm. It can be seen that the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel has achieved excellent electromagnetic wave absorption effect through structural design.

[0070] Figure 5 The images show the reflection loss diagrams of the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel prepared in Example 5 of this invention. (a) is a two-dimensional reflection loss diagram, and (b) is a contour plot of the three-dimensional reflection loss diagram. The reflection loss was calculated based on transmission line theory by measuring the electromagnetic parameters of the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel. Figure 5 As shown, CoNi alloy-supported nitrogen-doped magnetic carbon aerogels exhibit excellent electromagnetic wave absorption properties. Furthermore, according to... Figure 5 (b) It can be seen that the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel has the minimum reflection loss value of -39.35 dB at 1.78 mm and the maximum absorption bandwidth of 4.64 GHz when the matching thickness is 1.84 mm. It can be seen that the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel has achieved excellent electromagnetic wave absorption effect through structural design.

[0071] Figure 6 The impedance matching diagram is shown for the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel prepared in Example 4 of this invention. Impedance matching analysis was performed on the optimal magnetic carbon aerogel to obtain its impedance matching diagram, as shown below. Figure 6 As shown, in the low-frequency range of approximately 4-6 GHz, the Z-axis rises to its peak and approaches 1, indicating good impedance matching performance in this range. Figure 7 This is an electron image showing the adsorption of a magnet by a CoNi alloy-supported nitrogen-doped magnetic carbon aerogel prepared in Example 4 of this invention. It can be clearly seen that the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel exhibits magnetism due to the presence of the CoNi alloy, and its magnetism is not destroyed during the loading of carbon nanotubes, allowing it to be easily adsorbed by a magnet.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing nitrogen-doped magnetic carbon aerogel supported on a CoNi alloy, characterized in that, Includes the following steps: S1: Add crosslinking aid to the aqueous solution of biomass precursor, stir to form biomass precursor suspension, and subject the biomass precursor suspension to directional freezing and freeze-drying treatment in sequence to obtain biomass aerogel precursor. S2: The biomass aerogel precursor is placed in a nitrogen or inert atmosphere and subjected to heat treatment to obtain biomass-derived carbon aerogel. S3: Add the reducing agent to an organic solution containing cobalt salt and nickel salt, stir evenly to obtain a metal salt solution, add the biomass-derived carbon aerogel to the metal salt solution, and carry out a vacuum solvothermal reaction to obtain the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel.

2. The method for preparing a CoNi alloy-supported nitrogen-doped magnetic carbon aerogel according to claim 1, characterized in that, In step S1, the ratio of the crosslinking aid to the biomass precursor is (0.2-0.5) mL:(0.2-0.5) g.

3. The method for preparing a CoNi alloy-supported nitrogen-doped magnetic carbon aerogel according to claim 1, characterized in that, In step S1, the ratio of biomass precursor to water in the aqueous solution of the biomass precursor is (0.2-0.5) g:(10-40) mL.

4. The method for preparing a CoNi alloy-supported nitrogen-doped magnetic carbon aerogel according to claim 1, characterized in that, In step S1, the freeze-drying process takes 30-70 hours.

5. The method for preparing a CoNi alloy-supported nitrogen-doped magnetic carbon aerogel according to claim 1, characterized in that, In step S2, during the heat treatment process, the heating rate is 2-10 ℃ / min, the holding time is 1-6 h, and the holding temperature is 600-1000 ℃.

6. The method for preparing a CoNi alloy-supported nitrogen-doped magnetic carbon aerogel according to claim 1, characterized in that, In step S3, the ratio of the amount of cobalt salt, nickel salt and organic solvent is (0.1-1) g:(0.1-1) g:(20-50) mL.

7. The method for preparing a CoNi alloy-supported nitrogen-doped magnetic carbon aerogel according to claim 1, characterized in that, In step S3, the vacuum solvothermal reaction specifically involves placing the biomass-derived carbon aerogel and metal salt solution in a stainless steel reactor liner and performing multiple vacuum treatments. During the vacuum treatment, the vacuum level is 0.6-1 atmospheres, the treatment time for each treatment is 1-4 minutes, and the number of vacuum treatments is 1-3 times.

8. The method for preparing a CoNi alloy-supported nitrogen-doped magnetic carbon aerogel according to claim 1, characterized in that, In step S3, the temperature of the solvothermal reaction is 110-150℃, and the time is 2-10 h.

9. A CoNi alloy-supported nitrogen-doped magnetic carbon aerogel, characterized in that, It is prepared by the method described in any one of claims 1 to 8.

10. The application of the CoNi alloy-supported nitrogen-doped magnetic carbon aerogel as described in claim 9 in the field of electromagnetic shielding.

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