FeCo-c-cnts-bamboo carbon composite material, and preparation method and application thereof

Abstract

The application discloses a FeCo-C-CNTs-bamboo carbon composite material and a preparation method and application thereof, and comprises the following steps: after fresh bamboo shoots are dried and crushed, the bamboo shoots are sieved and then subjected to alkali treatment and activation to obtain an activated bamboo powder carrier; FeCo-C-CNTs nanocomposite material is dispersed in an aqueous solution of a surfactant, ultrasonic treatment is performed to obtain a dispersion liquid, then the activated bamboo powder carrier is added into the dispersion liquid, stirring and adsorption are performed, and separation, washing and freeze-drying are performed to obtain a precursor composite; the precursor composite is subjected to programmed temperature heat treatment under the protection of an inert atmosphere to obtain the FeCo-C-CNTs-bamboo carbon composite material. The application realizes uniform dispersion and stable compounding of a magnetic component and carbon nanotubes, and through multi-component cooperation and multi-level structure design, the prepared material has both dielectric loss and magnetic loss mechanisms and exhibits excellent electromagnetic wave absorption performance in a wide frequency range.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing materials, and particularly relates to a FeCo-C-CNTs-bamboo charcoal composite material, its preparation method, and its application. Background Technology

[0002] With the widespread adoption of 5G communication and high-density electronic devices, electromagnetic interference and radiation issues are becoming increasingly prominent. Absorbing materials can suppress electromagnetic leakage from equipment and optimize signal transmission quality, making them crucial for ensuring communication reliability and protecting human health.

[0003] Currently, high-performance microwave absorbing materials are developing towards lightweight, broadband, and composite materials. Composite materials, represented by iron-cobalt alloys and carbon nanotubes, have significant research value. However, both iron-cobalt alloys and carbon nanotubes are high-cost nanomaterials, and their large-scale preparation processes are complex and require stringent conditions, making it difficult to meet the cost and large-scale production requirements of practical applications.

[0004] On the other hand, biomass carbon materials, due to their porous, lightweight, and renewable properties, have become ideal substrates for constructing composite microwave absorbers. Bamboo, as a typical biomass, can be carbonized to form biochar with natural multi-level pores, but its microwave absorption performance is limited. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a FeCo-C-CNTs-bamboo charcoal composite material, its preparation method and application.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A method for preparing FeCo-C-CNTs-bamboo charcoal composite material includes the following steps: (1) Fresh bamboo shoots are dried, pulverized, and sieved to obtain micron-sized bamboo powder. The micron-sized bamboo powder is then activated by alkali treatment to obtain an activated bamboo powder carrier. The moisture content of the fresh bamboo shoots is >95%. (2) The FeCo-C-CNTs nanocomposite material was dispersed in an aqueous solution of a surfactant and ultrasonically treated to obtain a dispersion. Then, the activated bamboo powder carrier was added to the dispersion, stirred and adsorbed, and separated, washed and freeze-dried to obtain the precursor complex. The mass ratio of the dispersion to the activated bamboo powder carrier was (5~10):1. (3) The precursor composite is subjected to programmed temperature rise heat treatment under inert atmosphere protection, and the FeCo-C-CNTs-bamboo charcoal composite material is obtained by passing through a dehydration stage and a carbonization stage in sequence; the temperature of the dehydration stage is controlled at 110~130℃, and the temperature of the carbonization stage is controlled at 800~1000℃.

[0007] As a further improvement, in step (1), the fresh bamboo shoots are Gui bamboo shoots, small sweet bamboo shoots, pen-shaped bamboo shoots or arrow bamboo shoots, and the drying conditions are vacuum drying at 80±5℃ for 48±2 hours, and then crushed and passed through a 200-mesh sieve.

[0008] As a further improvement, in step (1), the alkaline treatment activation specifically involves immersing the micron-sized bamboo powder in a sodium hydroxide aqueous solution with a mass concentration of 5-10%, treating it at 75±10℃ for 1-4 hours, then washing it until neutral, and drying it at 80±5℃ for 48±2 hours.

[0009] As a further improvement, in step (2), the preparation method of the FeCo-C-CNTs nanocomposite material is as follows: a horizontal tube furnace is used, and the furnace body is arranged with an evaporation zone, a reaction zone and a deposition zone in sequence along the airflow direction. The temperature of the evaporation zone is controlled at 220-250℃, the temperature of the reaction zone is set at 950-1050℃, and the temperature of the deposition zone is maintained at 400-500℃. A mixture of iron acetylacetone and cobalt acetylacetone is placed in the evaporation zone, and the substrate is placed in the deposition zone. Hydrogen is used as the carrier gas and reaction atmosphere to perform chemical vapor deposition, and FeCo-C-CNTs-bamboo charcoal composite material is obtained on the substrate.

[0010] As a further improvement, in step (2), the surfactant is sodium dodecyl sulfate or sodium dodecylbenzene sulfonate, and its concentration in aqueous solution is 0.1-0.5 M; the concentration of the FeCo-C-CNTs nanocomposite material in dispersion is 0.5-5.0 mg / mL.

[0011] As a further improvement, in step (2), the ultrasonic treatment is carried out for 3-6 hours under the conditions of power 300-500 W and ice water bath temperature control ≤25℃.

[0012] As a further improvement, in step (2), the stirring adsorption is carried out at 300-600 rpm and 40-60℃ for 4-8 hours.

[0013] As a further improvement, in step (3), the programmed temperature rise heat treatment includes: raising the temperature to 110-130°C at a heating rate of 3-5°C / min and maintaining it at that temperature for 2-4 hours; then raising the temperature to 800-1000°C at a heating rate of 8-10°C / min and maintaining it at that temperature for 1-3 hours.

[0014] This invention provides a FeCo-C-CNTs-bamboo charcoal composite material prepared according to the aforementioned method. The composite material has a porous biochar framework in which FeCo-C nanoparticles and carbon nanotubes are uniformly distributed. The biochar framework inherits the morphology of bamboo fibers and exhibits the characteristics of dehydrated bamboo shoots. The multi-level porous structure formed during the reabsorption process.

[0015] This invention provides an application of the FeCo-C-CNTs-bamboo charcoal composite material, which is used in the field of electromagnetic wave absorption.

[0016] This invention provides a simple and structurally controllable method for preparing composite microwave absorbing materials. The method uses alkali-treated activated micron-sized bamboo powder as a biomass carrier and structural template. A pre-synthesized FeCo-C-CNTs nanocomposite material is uniformly loaded onto its surface and pores via solution adsorption, followed by high-temperature carbonization. This one-step process achieves both bamboo powder carbonization and composite material shaping. A multi-level composite structure is constructed through the adsorption-high-temperature carbonization process, ultimately yielding a multi-level FeCo-C-CNTs-C composite microwave absorbing material.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Carrier Advantages and High Adsorption Potential: This invention selects fresh, tender bamboo shoots (initial moisture content > 95%) that are naturally porous and rich in fiber as raw materials. After dehydration and drying, a highly hydrophilic micron-sized bamboo powder carrier is formed, with a water absorption rate of 3-5 times the dry powder mass. Combined with a controllable alkali treatment activation process, the specific surface area and surface active sites of the bamboo powder are significantly improved. During the adsorption process, based on the high water absorption characteristics of bamboo powder, activated bamboo powder is added to the nanocomposite dispersion at a mass ratio (FeCo-C-CNTs nanocomposite dispersion: activated bamboo powder carrier) of 5:1 to 10:1. This achieves efficient loading and complete utilization of nanomaterials within the pores of the bamboo powder, laying the foundation for the preparation of high-load composite microwave absorbing materials.

[0018] 2. Synergistic and efficient processes: A liquid-phase loading process combining surfactant-assisted ultrasonic dispersion and mechanical stirring adsorption is employed, leveraging the high water absorption and hydrophilic pores of bamboo powder to achieve uniform loading of FeCo-C-CNTs nanocomposites in the carrier. Subsequently, a one-step high-temperature carbonization process simultaneously completes biomass carbonization and composite material structure shaping. The process is simple, efficient, and exhibits good repeatability and scalability.

[0019] 3. Structural Synergy and Multiple Loss Mechanism: The prepared FeCo-C-CNTs-C composite material combines the dielectric framework of porous biochar, the magnetic loss characteristics of FeCo alloy, and the conductive network and interfacial polarization effect of CNTs. This hierarchical porous structure promotes multiple reflections and scattering of electromagnetic waves, achieving effective synergy between dielectric and magnetic losses, and significantly improving the impedance matching characteristics and broadband absorption performance of the material.

[0020] In summary, the method of this invention fully utilizes the natural porous structure, high water content, and genetic structure of bamboo shoots to achieve uniform dispersion and stable composite of magnetic components and carbon nanotubes. Through multi-component synergy and multi-level structural design, the prepared material exhibits both dielectric and magnetic loss mechanisms, demonstrating excellent electromagnetic wave absorption performance over a wide frequency range. This method is simple, controllable, and low-cost, and the resulting composite material has potential application value in the field of electromagnetic wave absorption. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The images are of fresh bamboo shoots, dried bamboo shoots and bamboo powder from Example 1, wherein: (a) fresh bamboo shoots; (b) dried bamboo shoots after complete dehydration; and (c) bamboo powder after mechanical pulverization.

[0023] Figure 2 This is a schematic diagram of FeCo-C-CNTs powder preparation using a tube furnace.

[0024] Figure 3 This is an image of the FeCo-C-CNTs-C powder prepared in Example 1.

[0025] Figure 4 This is the XRD (X-ray diffraction) pattern of the FeCo-C-CNTs-C powder prepared in Example 1.

[0026] Figure 5 This is a TEM (transmission electron microscope) image of FeCo-C-CNTs.

[0027] Figure 6 This is a TEM (transmission electron microscope) image of FeCo-C-CNTs-C prepared in Example 1.

[0028] Figure 7 This is a two-dimensional reflection loss (RL) spectrum of FeCo-C-CNTs-C-900.

[0029] Figure 8 This is a two-dimensional reflection loss (RL) spectrum of FeCo-C-CNTs-C-1000.

[0030] Figure 9 This is a two-dimensional reflection loss (RL) spectrum of FeCo-C-CNTs-C-800.

[0031] Figure 10 This is a two-dimensional reflection loss (RL) spectrum of FeCo-C-CNTs-C-5:1.

[0032] Figure 11 This is a two-dimensional reflection loss (RL) spectrum of FeCo-C-CNTs-C-15:1.

[0033] Figure 12 This is a two-dimensional reflection loss (RL) spectrum of Comparative Example 1.

[0034] Figure 13 This is the two-dimensional reflection loss (RL) spectrum of Comparative Example 2. Detailed Implementation

[0035] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0036] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0037] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0038] The core of this invention lies in using fresh bamboo shoots with an initial moisture content exceeding 95% as raw material. After dehydration, pulverization, and alkali treatment, a micron-sized bamboo powder carrier with high specific surface area and strong hydrophilicity is obtained. Activated bamboo powder is added to a dispersion containing FeCo-C-CNTs nanomaterials at a mass ratio of 5:1 to 10:1. The high water absorption properties of bamboo powder ensure complete absorption of the dispersion, thereby achieving efficient and high-capacity loading of the nanocomposite material within the pores of the bamboo powder. The loaded precursor is then carbonized at high temperature to ultimately produce a novel multi-level composite microwave absorbing material (FeCo-C-CNTs-C) with bamboo charcoal at its core, FeCo-C-CNTs nanomaterials embedded at one end and extended in all four directions at the other end.

[0039] In some specific embodiments of the present invention, the preparation method of the FeCo-C-CNTs-bamboo charcoal composite material of the present invention includes the following steps: (1) Preparation of activated bamboo powder carrier: Fresh bamboo shoots are dried, crushed and sieved to obtain micron-sized bamboo powder. Then, the micron-sized bamboo powder is activated by alkali treatment to obtain activated bamboo powder carrier.

[0040] In some embodiments, raw material selection and drying include: selecting fresh bamboo shoots (such as Gui bamboo shoots, Hunan sweet bamboo shoots, pen-shaped bamboo shoots, or arrow bamboo shoots) with large specific surface area and rich pore structure as raw materials. The initial moisture content of the fresh bamboo shoots is >95%, and the specifications are 15-25 cm in length and 1-3 cm in diameter. They are placed in a vacuum drying oven and dried at 80±5 ℃ for 48±2 hours to completely remove free water.

[0041] Fresh bamboo shoots with a moisture content of over 95%, after specific drying processes, form micron-sized bamboo powder. This powder not only retains the multi-level pores and fibrous structure of natural bamboo, but also possesses high porosity and hydrophilicity due to its extremely high initial moisture content, giving it a solution adsorption capacity of 5-10 times its own weight. This characteristic allows it to efficiently adsorb and fix FeCo-C-CNTs dispersions, achieving uniform loading of nanomaterials on the inner and outer surfaces of the bamboo powder—a feature not found in ordinary bamboo chips or conventional porous carbon materials.

[0042] In some embodiments, pulverization and sieving include: pulverizing the dried bamboo material using a mechanical pulverizer, followed by sieving using a standard sieve to collect micron-sized dry bamboo powder that passes through a 200-mesh sieve (approximately 75 μm in diameter).

[0043] In some embodiments, alkali treatment activation includes immersing the bamboo powder in a 5-10 wt% sodium hydroxide (NaOH) aqueous solution and treating it at a constant temperature of 75±10 °C for 1-4 hours. This process aims to partially remove lignin and hemicellulose from the bamboo powder, exposing more cellulose microfibers and internal porous structures, significantly increasing its specific surface area and surface active adsorption sites such as hydroxyl groups. After treatment, vacuum filtration is performed, and the filter cake is repeatedly washed with deionized water until the filtrate is neutral (pH≈7). Subsequently, the filter cake is placed in a vacuum drying oven and dried a second time at 80±5 °C for 48±2 hours to obtain the activated bamboo powder carrier.

[0044] In some embodiments, the specific surface area of ​​the activated bamboo powder is increased to 20-35 m² / g after alkali treatment. The higher specific surface area provides more active sites and loading space, ensuring uniform and high-capacity loading of the nanocomposite material, which is crucial for constructing a continuous multi-level loss network.

[0045] (2) Loading of nanocomposite materials on bamboo powder: FeCo-C-CNTs nanocomposite materials were dispersed in an aqueous solution of surfactant, and ultrasonic treatment was performed to obtain a dispersion. The activated bamboo powder carrier was added to the dispersion, stirred and adsorbed, and then separated, washed and freeze-dried to obtain the precursor complex.

[0046] In some embodiments, the preparation of FeCo-C-CNTs (carbon nanotubes) nanocomposites includes: synthesizing FeCo-C-CNTs composite materials on a steel wire ball substrate using an organic chemical vapor deposition method (e.g., ...). Figure 2 (As shown). A horizontal tube furnace was used, with the system consisting of an evaporation zone, a reaction zone, and a deposition zone arranged sequentially along the gas flow direction. Equimolar amounts of iron acetylacetonate (Fe(acac)3) and cobalt acetylacetonate (Co(acac)2) were placed in the evaporation zone and vaporized at 220-250℃. The reaction zone temperature was set at 950-1050℃, and the deposition zone temperature was maintained at 400-500℃. Steel wool was used as the collection substrate for FeCo-C-CNTs. The distance between the evaporation zone and the reaction zone was 20-30 cm. Hydrogen was used as the carrier gas, with a total flow rate controlled at 100-200 sccm. The system pressure was maintained at 200-250 Pa, and the reaction lasted for 4-5 hours.

[0047] In this process, the gaseous precursor is transported by the carrier gas to the high-temperature reaction zone where it decomposes. The main decomposition process in the high-temperature reaction zone is as follows: Fe(acac)3 and Co(acac)2 decompose stepwise into Fe and Co atoms and (acac)· free radicals; the reaction is as follows: Fe(acac)3(g) → Fe(acac)2(g) + (acac)(g) Fe(acac)2(g) → Fe(acac)·(g) + (acac)(g) Fe(acac)·(g) → Fe (g) + (acac)·(g) Co(acac)2(g) → Co(acac)·(g) + (acac)(g) Co(acac)·(g) → Co (g) + (acac)·(g) Fe and Co atoms condense to form FeCo atomic clusters. These clusters catalyze the decomposition of (acac)· free radicals to produce carbon atoms, which then form FeCoC clusters. Subsequently, the FeCoC clusters aggregate, and the Fe and Co atoms within them form alloy nanoparticles. Simultaneously, carbon atoms precipitate and encapsulate small-sized (<10 nm) FeCo nanocores, forming FeCo-C core-shell nanoparticles. Large-diameter FeCo nanoparticles can catalyze the growth of carbon nanotubes. The FeCo-C core-shell nanoparticles adhere to the surface of the carbon nanotubes capped by the large-sized FeCo nanoparticles through strong surface adsorption, ultimately constructing a FeCo-C-CNTs composite structure, which is then deposited on a steel wool sphere.

[0048] In some embodiments, the dispersion preparation includes dispersing the FeCo-C-CNTs nanocomposite material at a concentration of 0.5-5.0 g / L in an aqueous solution of sodium dodecyl sulfate (SDS) or sodium dodecylbenzene sulfonate (SDBS) with a concentration of 0.1-0.5 M.

[0049] In some embodiments, ultrasonic dispersion includes: placing the above-mentioned mixed system in an ultrasonic cell disruptor and ultrasonically treating it for 3-6 hours under the conditions of power 300-500 W and temperature control in an ice-water bath (≤25℃) to ensure that the nanocomposite material is fully deagglomerated and forms a relatively stable and uniform suspension.

[0050] In some embodiments, the adsorption loading includes: under continuous mechanical stirring (300-600 rpm), slowly adding the above-obtained activated bamboo powder carrier to the above dispersion at a mass ratio (FeCo-C-CNTs nanocomposite dispersion: activated bamboo powder carrier) of 5-10:1. This ratio is set based on the significant high water absorption characteristics of dried bamboo shoots (water absorption rate can reach 5-10 times its own mass), which can ensure that the liquid phase and solid phase in the system are fully matched, thereby maximizing the adsorption potential of bamboo powder. Subsequently, adsorption is carried out continuously in a constant temperature environment of 40-60℃ for 4-8 hours. Utilizing the hydrophilic pores inside the bamboo powder and the abundant active sites on the surface, the FeCo-C-CNTs nanocomposite material is effectively absorbed or firmly attached to the surface and pore structure of the bamboo powder through physical adsorption and capillary action, realizing the complete utilization of nanomaterials. After loading, the solid product is separated and collected, and washed 2-3 times with deionized water to remove residual dispersant. Finally, the precursor complex is obtained by freeze drying, denoted as FeCoC-bamboo.

[0051] In some embodiments, the mass ratio of activated bamboo powder carrier to FeCo-C-CNTs nanocomposite material is 1~15:1, preferably 1~5:1.

[0052] This invention, through systematic combination and parameter optimization, constitutes a complete functional integrated process of "carrier activation - nanomaterial dispersion - liquid-phase adsorption": Alkali treatment activation not only removes lignin and hemicellulose, but also significantly exposes cellulose microfibers, increases specific surface area, and introduces surface hydroxyl groups, providing abundant active sites for subsequent nanomaterial adsorption. Dispersion using an aqueous surfactant solution, under ultrasonic assistance, achieves stable dispersion of FeCo-C-CNTs, avoiding agglomeration and ensuring their uniform distribution on the bamboo powder surface and within the pores. Solution adsorption loading: Utilizing the high adsorption characteristics of activated bamboo powder, through physical adsorption and capillary action, the nanocomposite material is in-situ fixed to the pores and surface of the bamboo powder, achieving a tight bond between the nanomaterial and the biomass carrier at the molecular / nanoscale. The synergistic effect of the above steps ensures a high loading rate and uniform distribution of FeCo-C-CNTs on the bamboo powder carrier, laying the foundation for the formation of a uniform composite hierarchical structure during subsequent carbonization.

[0053] (3) High-temperature carbonization to form composite microwave absorbing material: The precursor composite is subjected to programmed temperature rise heat treatment under inert atmosphere protection, and then goes through dehydration stage and carbonization stage in sequence to finally obtain FeCo-C-CNTs-C composite microwave absorbing material.

[0054] In some embodiments, the FeCoC-bamboo precursor is placed in a tubular furnace quartz boat and heat-treated under inert gas protection according to the following procedure: 1) Dehydration and pre-stabilization stage: The temperature is increased from room temperature to 110-130℃ at a rate of 3-5℃ / min, and then kept at this temperature for 2-4 hours to completely remove residual adsorbed water and some bound water.

[0055] 2) High-temperature carbonization stage: Subsequently, the temperature is increased at a rate of 8~10℃ / min to the preset final carbonization temperature (800~1000℃, preferably 880~950℃), and maintained at this temperature for 1~3 hours. During this process, components such as bamboo powder and cellulose undergo pyrolysis and carbonization, transforming into a porous biochar framework with the genetic morphology of bamboo fiber; at the same time, the supported FeCo-C-CNTs structure is further graphitized and enhanced, and tightly bonded to the biochar matrix, ultimately forming a multi-level composite microwave absorbing material of biochar, uniformly distributed FeCo-C nanoparticles and CNTs, denoted as FeCo-C-CNTs-C.

[0056] In some embodiments, the inert gas is high-purity nitrogen or argon, and the gas flow rate is 80-150 sccm. This flow rate range, combined with the system's operation at atmospheric pressure, effectively removes pyrolysis gases, maintains an inert atmosphere, and avoids the loss of precursor powder due to excessive flow rate.

[0057] This two-step heating and carbonization process is the core of achieving controllable transformation of the material structure. The dehydration stage avoids structural damage caused by the rapid evaporation of moisture at high temperatures later on; the precise control of the carbonization temperature directly determines the crystallinity, pore structure, graphitization degree, and interfacial bonding state of the FeCo-C-CNTs nanocomposite material, thereby synergistically regulating the electromagnetic parameters of the composite material.

[0058] During the high-temperature carbonization process, the rich porous structure formed by the dehydration-reabsorption cycle of bamboo powder with an initial moisture content >95% provides an optimized spatial configuration and interfacial environment for the full adsorption of FeCo-C-CNTs nanocomposites. The main components of bamboo powder (cellulose and hemicellulose) undergo pyrolysis, aromatization, and graphitization, forming a highly porous biochar framework. Simultaneously, the FeCo-C-CNTs nanocomposites supported on it undergo further heat treatment, resulting in increased graphitization of the carbon coating layer and carbon nanotubes, and enhanced crystallinity of the FeCo alloy particles. The biochar and nanocomposites are tightly coupled through physical embedding and chemical bonding, constructing a stable composite system.

[0059] The FeCo-C-CNTs-C composite microwave absorbing material of the present invention has a porous biochar framework, in which FeCo-C nanoparticles and carbon nanotubes are uniformly distributed; the biochar framework inherits the morphology of bamboo fiber and has a multi-level porous structure formed by the dehydration-reabsorption process due to the high water content of bamboo powder.

[0060] In the final FeCo-C-CNTs-C composite material, the porous biochar framework provides a lightweight matrix and dielectric loss, the FeCo alloy particles contribute magnetic loss, and the carbon nanotube network constructs efficient conductive channels and induces interfacial polarization effects. These three elements work synergistically to construct a multi-level composite absorber structure that combines good impedance matching with multiple attenuation mechanisms.

[0061] The FeCo-C-CNTs-C composite microwave absorbing material of this invention possesses a unique bifunctional nanounit multilevel composite structure. Porous biochar derived from bamboo powder forms a continuous three-dimensional framework; FeCo-C nanoparticles are embedded within it as magnetic functional units; and carbon nanotubes intertwine to form a conductive network, connecting and penetrating the entire framework. This special structure, through the synergy of dielectric loss, magnetic loss, and structural loss, lays a solid foundation for efficient microwave absorption.

[0062] The preparation process of the FeCo-C-CNTs nanocomposite material in the following examples is as follows: A horizontal tube furnace with an inner diameter of 60 mm and a length of 110 cm was used. The distance between the evaporation zone and the reaction zone was set to 25 cm, and the distance between the reaction zone and the deposition zone was set to 20 cm.

[0063] Ferric acetylacetone and cobalt acetylacetone were mixed evenly at a 1:1 molar ratio and placed in a quartz boat, which was then placed in the evaporation zone of a tube furnace. A 0.2g steel wool ball was placed in the deposition zone. The evaporation zone temperature was set to 250℃, the reaction zone temperature to 1000℃, and the deposition zone temperature to 450℃. Hydrogen gas was introduced into the system as a carrier gas, with a total flow rate controlled at 150 sccm. The vacuum pump system was turned on to maintain and stabilize the internal pressure at 200 Pa. The reaction was carried out under the above conditions for 4 hours. After the reaction was completed, the mixture was allowed to cool naturally to room temperature under a hydrogen atmosphere. Figure 5 This is a TEM image of the obtained FeCo-C-CNTs.

[0064] Example 1: Preparation of composite absorbing materials (1) Pretreatment of bamboo powder carrier: Fresh bamboo shoots (moisture content > 95%) were dried at 80±5 ℃ for 48 hours, then pulverized by a high-speed pulverizer and passed through a 200-mesh standard sieve to obtain micron-sized bamboo powder. Figure 1 The images are of fresh bamboo shoots, dried bamboo shoots and bamboo powder from Example 1, wherein: (a) fresh bamboo shoots; (b) dried bamboo shoots after complete dehydration; and (c) bamboo powder after mechanical pulverization.

[0065] Weigh 50 grams of bamboo powder and immerse it in 500 ml of an 8 wt% sodium hydroxide (NaOH) solution. Maintain the solution at an 80°C water bath with constant stirring for 2 hours. After treatment, perform vacuum filtration and wash repeatedly with deionized water until the filtrate is neutral (pH≈7). Place the resulting solid in a vacuum drying oven and dry at 80°C for 48 hours to obtain activated bamboo powder.

[0066] (2) Loading of nanocomposite materials: 10 g of FeCo-C-CNTs nanocomposite materials were weighed and dispersed in 2 liters of 0.3 M sodium dodecylbenzenesulfonate (SDBS) aqueous solution. The mixture was placed in an ultrasonic cell disruptor and ultrasonically treated for 4 hours at 400 W power and ice-water bath temperature control (≤25℃) to obtain a uniformly dispersed suspension.

[0067] Under continuous mechanical stirring (500 rpm), 10 g of activated bamboo powder was slowly added to the above 50 g suspension. The mixture was stirred and adsorbed in a 50°C constant temperature water bath for 6 hours to ensure the nanocomposite material was fully loaded onto the surface and pores of the bamboo powder. After adsorption, the bamboo powder swelled, and the suspension was completely absorbed by the bamboo powder. After loading was complete, the solid product was collected by centrifugation, washed three times with deionized water, and finally freeze-dried for 24 hours to obtain the precursor complex, denoted as FeCoC-bamboo.

[0068] (3) High-temperature carbonization treatment: The FeCoC-bamboo precursor was placed in a tubular furnace quartz boat and heat-treated under argon protection (flow rate 100 sccm). First, the temperature was increased to 120℃ at 5℃ / min and held for 3 hours for dehydration pretreatment. Then, the temperature was increased to 900℃ at 10℃ / min and held at this temperature for 2 hours to complete the carbonization process. The product was cooled to room temperature in an argon atmosphere to obtain the final product, denoted as FeCo-C-CNTs-C-900.

[0069] Figure 3 This is an image of the FeCo-C-CNTs-C powder prepared in Example 1. Figure 4 This is the XRD pattern of the FeCo-C-CNTs-C powder prepared in Example 1. Figure 6 This is a TEM image of the FeCo-C-CNTs-C prepared in Example 1. It can be observed that FeCo-C-CNTs are adsorbed only on the surface of bamboo charcoal, forming a tentacle-like structure that extends in all directions.

[0070] Example 2: Study on the Influence of Carbonization Temperature Keeping all conditions in steps 1-3 of Example 1 unchanged, only changing the final temperature of the carbonization process, setting it to 800℃ and 1000℃ respectively, with a holding time of 2 hours for both. The resulting products are denoted as FeCo-C-CNTs-C-800 and FeCo-C-CNTs-C-1000 respectively.

[0071] Example 3: Study on the impact of load ratio Keeping all other conditions consistent with Example 1, only changing the mass ratio of activated bamboo powder to FeCo-C-CNTs nanocomposite material in step 2: Mass ratio 5:1: Take 10 grams of activated bamboo powder and 2 grams of nanocomposite material, and the resulting product is denoted as FeCo-C-CNTs-C-5:1.

[0072] Mass ratio 15:1: Take 30 grams of activated bamboo powder and 2 grams of nanocomposite material, and the resulting product is denoted as FeCo-C-CNTs-C-15:1.

[0073] Comparative Example 1: The effect of bamboo moisture content Except for the use of mature bamboo shoots (with a moisture content of 55%), all other conditions were kept the same as in Example 1. The results showed that the adsorption rate of bamboo powder on the FeCo-C-CNTs nanomaterial solution was only 20%–30% of that when using fresh bamboo shoots, making it difficult to effectively adsorb FeCo-C-CNTs nanomaterials.

[0074] Comparative Example 2: Effect of Alkali Treatment on Activation Except for omitting the alkali treatment activation step, all other conditions are consistent with those in Example 1.

[0075] The samples from the examples and comparative examples were pressed into coaxial rings (the thickness of each sample was 2.2 mm), and their electromagnetic parameters were tested using a vector network analyzer. The reflection loss (RL) value was then calculated based on the electromagnetic parameters.

[0076] Figure 7 This is a two-dimensional reflection loss (RL) spectrum of FeCo-C-CNTs-C-900, with an effective bandwidth of 6.5 GHz and a minimum reflection loss of -42.4 dB.

[0077] Figure 8 This is a two-dimensional reflection loss (RL) spectrum of FeCo-C-CNTs-C-1000, with an effective bandwidth of 6.6 GHz and a minimum reflection loss of -26.2 dB.

[0078] Figure 9 This is a two-dimensional reflection loss (RL) spectrum of FeCo-C-CNTs-C-800.

[0079] Figure 10 It is a two-dimensional reflection loss (RL) spectrum of FeCo-C-CNTs-C-5:1, with an effective bandwidth of 2.2 GHz and a minimum reflection loss of -37.4 dB.

[0080] Figure 11 It is a two-dimensional reflection loss (RL) spectrum of FeCo-C-CNTs-C-15:1, with an effective bandwidth of 6.3 GHz and a minimum reflection loss of -18.2 dB.

[0081] Figure 12 This is a two-dimensional reflection loss (RL) spectrum of Comparative Example 1. Figure 13 This is the two-dimensional reflection loss (RL) spectrum of Comparative Example 2.

[0082] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for preparing FeCo-C-CNTs-bamboo charcoal composite material, characterized in that, Includes the following steps: (1) Fresh bamboo shoots are dried, pulverized, and sieved to obtain micron-sized bamboo powder. The micron-sized bamboo powder is then activated by alkali treatment to obtain an activated bamboo powder carrier. The moisture content of the fresh bamboo shoots is >95%. (2) The FeCo-C-CNTs nanocomposite material was dispersed in an aqueous solution of a surfactant and ultrasonically treated to obtain a dispersion. Then, the activated bamboo powder carrier was added to the dispersion, stirred and adsorbed, and separated, washed and freeze-dried to obtain the precursor complex. The mass ratio of the dispersion to the activated bamboo powder carrier was (5~10):

1. (3) The precursor composite is subjected to programmed temperature rise heat treatment under inert atmosphere protection, and the FeCo-C-CNTs-bamboo charcoal composite material is obtained by passing through a dehydration stage and a carbonization stage in sequence; the temperature of the dehydration stage is controlled at 110~130℃, and the temperature of the carbonization stage is controlled at 800~1000℃.

2. The preparation method of the FeCo-C-CNTs-bamboo charcoal composite material according to claim 1, characterized in that, In step (1), the fresh bamboo shoots are Gui bamboo shoots, small sweet bamboo shoots, pen-shaped bamboo shoots or arrow bamboo shoots, and the drying conditions are vacuum drying at 80±5℃ for 48±2 hours, and then crushed and passed through a 200-mesh sieve.

3. The preparation method of the FeCo-C-CNTs-bamboo charcoal composite material according to claim 1, characterized in that, In step (1), the alkaline treatment activation specifically involves immersing the micron-sized bamboo powder in a sodium hydroxide aqueous solution with a mass concentration of 5-10%, treating it at 75±10℃ for 1-4 hours, then washing it until neutral, and drying it at 80±5℃ for 48±2 hours.

4. The preparation method of the FeCo-C-CNTs-bamboo charcoal composite material according to claim 1, characterized in that, In step (2), the preparation method of the FeCo-C-CNTs nanocomposite material is as follows: a horizontal tube furnace is used, and the furnace body is arranged with an evaporation zone, a reaction zone and a deposition zone in sequence along the airflow direction. The temperature of the evaporation zone is controlled at 220-250℃, the temperature of the reaction zone is set at 950-1050℃, and the temperature of the deposition zone is maintained at 400-500℃. A mixture of iron acetylacetone and cobalt acetylacetone is placed in the evaporation zone, and the substrate is placed in the deposition zone. Hydrogen is used as the carrier gas and reaction atmosphere to perform chemical vapor deposition, and FeCo-C-CNTs-bamboo charcoal composite material is obtained on the substrate.

5. The preparation method of the FeCo-C-CNTs-bamboo charcoal composite material according to claim 1, characterized in that, In step (2), the surfactant is sodium dodecyl sulfate or sodium dodecylbenzene sulfonate, and its concentration in aqueous solution is 0.1-0.5 M; the concentration of the FeCo-C-CNTs nanocomposite material in dispersion is 0.5-5.0 mg / mL.

6. The method for preparing the FeCo-C-CNTs-bamboo charcoal composite material according to claim 1, characterized in that, In step (2), the ultrasonic treatment is carried out for 3-6 hours under the conditions of power 300-500 W and ice water bath temperature control ≤25℃.

7. The method for preparing the FeCo-C-CNTs-bamboo charcoal composite material according to claim 1, characterized in that, In step (2), the stirring adsorption is carried out at 300-600 rpm and 40-60℃ for 4-8 hours.

8. The method for preparing the FeCo-C-CNTs-bamboo charcoal composite material according to claim 1, characterized in that, In step (3), the programmed temperature rise heat treatment includes: raising the temperature to 110-130°C at a heating rate of 3-5°C / min and maintaining it at that temperature for 2-4 hours; then raising the temperature to 800-1000°C at a heating rate of 8-10°C / min and maintaining it at that temperature for 1-3 hours.

9. A FeCo-C-CNTs-bamboo charcoal composite material prepared by the preparation method according to any one of claims 1 to 8, characterized in that, The composite material has a porous biochar framework in which FeCo-C nanoparticles and carbon nanotubes are uniformly distributed; the biochar framework inherits the morphology of bamboo fiber and exhibits the characteristics of dehydrated bamboo shoots. The multi-level porous structure formed during the reabsorption process.

10. The application of the FeCo-C-CNTs-bamboo charcoal composite material according to claim 9, characterized in that, It is applied to the field of electromagnetic wave absorption.

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