Carbon-coated Fe-Co-Ni-B magnetic micron alloy particles, and preparation method and application thereof

Abstract

The application discloses a kind of carbon-coated Fe-Co-Ni-B magnetic micron alloy particles and preparation method and application thereof, comprising the following steps: iron acetylacetonate, cobalt acetylacetonate, nickel acetylacetonate are dissolved in anhydrous ethanol, then cyclopentyl boronic acid is added and dissolved to obtain mixed solution, the mixed solution is carried out solvothermal reaction, after reaction is completed, boron-doped pre-decomposition precursor powder is obtained by post-processing;Under stirring, glucose aqueous solution is added to pre-decomposition precursor powder and mixed uniformly, so that powder surface is uniformly adsorbed and wrapped glucose solution, then dried to obtain glucose uniformly coated composite precursor;The composite precursor is carried out programmed temperature heat treatment under inert atmosphere or weak reducing atmosphere, to obtain carbon-coated Fe-Co-Ni-B magnetic micron alloy particles with core-shell structure.The application successfully prepares magnetic composite material with high saturation magnetic magnetic performance, good chemical stability and controllable magnetic performance.

Description

Technical Field

[0001] This invention belongs to the field of magnetic functional materials technology, and particularly relates to a carbon-coated Fe-Co-Ni-B magnetic micron alloy particle, its preparation method and application. Background Technology

[0002] Magnetic materials play a vital role in modern industry and technology, and the optimization and innovation of their properties are key to driving the development of fields such as electronics, power, information storage, and sensors. Among the many magnetic material systems, transition metal-based alloys (such as Fe, Co, Ni, and their multi-element alloys) have always been a research focus due to their high saturation magnetization, tunable Curie temperature, and rich dimensions of magnetic property control.

[0003] However, integrating multiple elements such as Fe, Co, and Ni into micron-sized alloy particles with uniform composition and controllable structure presents significant preparation challenges. Differences in the physicochemical properties of the elements (such as melting point, vapor pressure, and oxidation tendency) can easily lead to component segregation, phase separation, and surface oxidation during preparation. This results in the actual magnetic properties of the material (such as saturation magnetization and coercivity) deviating significantly from design expectations, and exhibiting poor batch-to-batch stability. Furthermore, micron-sized magnetic particles have a large specific surface area and poor chemical stability in environmental media, posing a severe challenge to their long-term reliability and durability.

[0004] Introducing a coating layer onto the surface of magnetic particles is an effective strategy to improve their stability and regulate their performance. Carbon materials, especially graphitic carbon with good crystallinity, are considered ideal coating materials due to their stable chemical properties, good controllable conductivity / insulation, and ability to form clear interfaces with metals. Traditional carbon coating methods (such as chemical vapor deposition) often face problems such as complex processes, high costs, and poor applicability to complex alloy compositions, making it difficult to achieve uniform, complete, and controllable carbon layer coatings with varying thickness and interface structure on the surface of micron-sized multi-element alloy particles. Inhomogeneous coating can lead to dispersion of properties between particles and poor interfacial bonding between the coating layer and the magnetic core, which not only fails to provide effective protection but may also introduce additional stress or defects, adversely affecting the overall magnetic properties of the material, such as potentially increasing the energy barrier for magnetization reversal. The conventional saturation magnetic moment of carbon-coated iron-based alloys is approximately 60 emu / g, which needs further improvement. 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 carbon-coated Fe-Co-Ni-B magnetic micron alloy particles, their 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 carbon-coated Fe-Co-Ni-B magnetic micron alloy particles includes the following steps: (1) Dissolve iron acetylacetone, cobalt acetylacetone, and nickel acetylacetone in anhydrous ethanol, then add cyclopentylboric acid and dissolve it to obtain a mixed solution. Heat the mixed solution to 150~180℃ for a solvothermal reaction. After the reaction is completed, post-processing is performed to obtain boron-doped pre-decomposition precursor powder. (2) Add glucose aqueous solution dropwise to pre-decomposed precursor powder under stirring and mix evenly so that glucose solution is uniformly adsorbed and coated on the powder surface. Then dry to obtain a composite precursor uniformly coated with glucose. (3) The composite precursor is subjected to programmed heating heat treatment in an inert atmosphere or a weak reducing atmosphere to carbonize glucose to form a carbon coating layer and graphitize it. The Fe-Co-Ni-B alloy phase is formed by carbothermal reduction to obtain carbon-coated Fe-Co-Ni-B magnetic micron alloy particles with core-shell structure.

[0007] As a further improvement, in step (1), iron acetylacetone, cobalt acetylacetone, and nickel acetylacetone are added in a Fe:Co:Ni metal molar ratio of 1:1:1.

[0008] As a further improvement, step (1) controls the amount of boron added to cyclopentylboronic acid to be 1% to 8% of the total molar amount of iron, cobalt and nickel metals.

[0009] As a further improvement, the solvothermal reaction time in step (1) is 1.5 to 3 hours.

[0010] As a further improvement, the concentration of the glucose aqueous solution in step (2) is 60~70wt%.

[0011] As a further improvement, in step (2), the mass ratio of glucose to pre-decomposed precursor powder is 1:5 to 1:15.

[0012] As a further improvement, in step (2), the glucose solution is added dropwise to the precursor powder over 1.5 hours with stirring, and stirring is continued for 30 minutes after the addition is complete.

[0013] As a further improvement, the programmed temperature rise heat treatment in step (3) includes the following three stages: The first stage involves maintaining a constant temperature of 450~500℃ for 30~60 minutes. The second stage involves maintaining a constant temperature of 600-700℃ for 1-2 hours. The third stage involves maintaining a constant temperature of 800~1000℃ for 1~3 hours.

[0014] The present invention also provides carbon-coated Fe-Co-Ni-B magnetic micron alloy particles, which are prepared by the preparation method described above. They have a core-shell structure, with the core being the Fe-Co-Ni-B multi-element magnetic alloy phase and the outer shell being a continuous and dense carbon layer.

[0015] The present invention also provides an application of the carbon-coated Fe-Co-Ni-B magnetic micron alloy particles as magnetic functional materials.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs an integrated strategy of "solventothermal synthesis of precursors - liquid-phase adsorption carbon coating - in-situ carbothermal reduction alloying". The solvothermal reaction ensures the uniform mixing and initial bonding of multiple elements such as Fe, Co, Ni, and B at the molecular / nanoscale. Glucose aqueous solution serves as the carbon source, achieving uniform coating on the surface of the ultrafine precursor powder through liquid-phase adsorption. In the subsequent programmed temperature heat treatment, a glucose carbon layer forms first, serving not only as the carbon source for subsequent reactions but also as a constraint layer for the "microreactor". The internal multi-metal-boron precursor is reduced and alloyed within the carbon layer, preventing excessive sintering and growth of metal particles and compositional segregation at high temperatures. Simultaneously, the carbon layer graphitizes at high temperatures, forming a tight interfacial bond with the alloy core. The uniform and dense carbon coating effectively improves the material's chemical stability and corrosion resistance.

[0017] This invention achieves complete and uniform carbon coating of the alloy core by optimizing the composition of multi-element alloys and the gradient carbonization process. It effectively solves the problems of difficulty in controlling the uniformity of multi-element alloy composition, easy oxidation of micron-sized particles, and poor applicability of traditional carbon coating processes to complex alloys. A magnetic composite material with high saturation magnetic properties, good chemical stability, and controllable magnetic properties has been successfully prepared, showing promising applications in soft magnetism, magnetic shielding, and other fields. Attached Figure Description

[0018] 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.

[0019] Figure 1 These are TEM images of carbon-coated Fe-Co-Ni-B magnetic micron alloy particles: (a) Example 1; (b) Example 2; (c) Example 3; (d) Example 4. Figure 2These are TEM images and elemental distribution maps (Fe, Co, Ni, B) of carbon-coated Fe-Co-Ni-B magnetic micron alloy particles from Example 1: (a) TEM image; (b) Fe distribution; (c) Co distribution; (d) Ni distribution; (e) B distribution. Figure 3 The XPS spectra (Fe, Co, Ni, B, C) of carbon-coated Fe-Co-Ni-B magnetic micron alloy particles in Example 1 are as follows: (a) Fe spectrum; (b) Co spectrum; (c) Ni spectrum; (d) B spectrum; (e) C spectrum. Figure 4 It is the hysteresis loop of carbon-coated Fe-Co-Ni-B magnetic micron alloy particles (Example 1). Figure 5 The hysteresis loop of carbon-coated Fe-Co-Ni-B magnetic micron alloy particles (Example 2). Figure 6 It is the hysteresis loop of carbon-coated Fe-Co-Ni-B magnetic micron alloy particles (Example 3). Figure 7 It is the hysteresis loop of carbon-coated Fe-Co-Ni-B magnetic micron alloy particles (Example 4). Detailed Implementation

[0020] 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.

[0021] 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.

[0022] 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.

[0023] In some specific embodiments of the present invention, the method for preparing carbon-coated Fe-Co-Ni-B magnetic micron alloy particles of the present invention includes the following steps: Step 1: Preparation of boron-doped precursor solution and solvothermal reaction Raw material preparation and dissolution: Under a dry environment with humidity below 30%, Fe(acac)3, Co(acac)2, and Ni(acac)2 are dissolved together in anhydrous ethanol at a Fe:Co:Ni metal molar ratio of 1:1:1, and stirred to form a homogeneous solution.

[0024] Boron source introduction: Add cyclopentylboronic acid to the above solution as a boron (B) source, and control the amount of boron added to be 1% to 8% (preferably 1% to 4%) of the total molar amount of iron, cobalt and nickel metals, and continue stirring to completely dissolve the cyclopentylboronic acid.

[0025] Solvothermal reaction: The mixed solution is heated to 150~180℃ and kept at this temperature for 1.5~3 hours to carry out the solvothermal reaction.

[0026] Precursor powder processing: After drying, pulverizing, and sieving, boron-doped pre-decomposed precursor powder with uniform composition and fine particle size is obtained. Preferably, the drying is vacuum drying at 60°C for 24 hours; the pulverizing is dry mechanical pulverizing at 100~150 rpm for 30 seconds, repeated 2~3 times; and the sieving uses a 500~800 mesh sieve.

[0027] In the solvothermal reaction, the conversion process of each raw material is as follows: Acetylacetone iron / cobalt / nickel: The organometallic complex does not completely decompose under mild solvothermal conditions, but only gradually loses some of the acetylacetone ligands, transforming into Fe, Co, and Ni multi-component composite hydroxyl oxide / weakly coordinated metal precursor clusters. This achieves uniform dispersion and doping and mutual solubility of the three metal ions at the molecular scale, laying a foundation for uniform composition in subsequent alloying.

[0028] Cyclopentylboronic acid undergoes slight dehydration condensation in weakly polar alcohol solvents and low-temperature solvothermal environments, removing some organic groups and transforming into an active boron-oxygen intermediate. This intermediate is uniformly adsorbed and bonded to the surface of metal precursor clusters, achieving atomic-level uniform doping of boron.

[0029] The homogeneous composite of metal precursors and uniform anchoring crosslinking with boron elements, followed by drying and pulverization, yields a boron-doped metal composite oxide precursor powder with uniform composition. This provides the structural and compositional prerequisites for the subsequent high-temperature carbothermal reduction to generate Fe-Co-Ni-B alloys.

[0030] Step 2: Carbon precursor coating Preparation of glucose solution: Prepare a clear glucose aqueous solution with a mass fraction of 60-70 wt% as a carbon layer precursor solution.

[0031] Coating process: A glucose aqueous solution is slowly added dropwise to the precursor powder at a glucose to precursor powder mass ratio of 1:5 to 1:15 (this ratio ensures the formation of a complete and appropriately thick carbon coating layer), and mixed for 1 to 2 hours under stirring, allowing the glucose solution to be uniformly adsorbed and coated onto the powder surface. Preferably, the stirring speed is 200 to 400 rpm. During this process, the glucose solution uniformly wets and coats each precursor powder particle in the form of an atomization or liquid film.

[0032] Drying treatment: After the addition is complete, the mixture is dried at 70~90℃ for 6~12 hours to completely remove moisture and obtain a glucose-coated complex precursor in the form of a loose solid powder.

[0033] Step 3: In-situ carbonization and alloying heat treatment The composite precursor obtained in step two is placed in a tube furnace and subjected to programmed temperature rise heat treatment under an inert atmosphere (such as argon) or a weakly reducing atmosphere (such as an argon-hydrogen mixture). Preferably, the entire process is carried out under a flowing argon atmosphere with a gas flow rate of 100-300 sccm. A sufficient inert gas flow not only effectively isolates oxygen and prevents product oxidation, but also promptly removes gaseous byproducts generated during pyrolysis, ensuring the smooth progress of the reaction and the purity of the product.

[0034] The temperature rise process: The first stage (pyrolysis and carbonization of carbon precursor): The furnace temperature is raised from room temperature to 450-500℃ at a heating rate of 3-5℃ / min, and held at 450-500℃ for 30-60 minutes. In this stage, glucose undergoes slow pyrolysis, dehydration, and decarbonylation reactions, resulting in preliminary carbonization and the initial formation of a uniform amorphous carbon coating layer on the powder surface.

[0035] The second stage (carbothermic reduction and initial formation of alloy nuclei): The furnace temperature is increased from 450-500℃ to 600-700℃ at a heating rate of 2-3℃ / min, and held at 600-700℃ for 1-2 hours. During this intermediate temperature stage, the precursors such as acetylacetone / oxide / hydroxide coated with carbon are gradually reduced to elemental metals under the reduction action of carbon. At the same time, boron begins to diffuse into the metal lattice, and the Fe-Co-Ni-B alloy phase begins to nucleate and grow initially.

[0036] The third stage (alloy densification and carbon layer graphitization): The furnace temperature is increased from 600-700℃ to 800-1000℃ at a heating rate of 2.5-3.5℃ / min, and held at 800-1000℃ for 1-3 hours. This high-temperature stage is crucial for the full crystallization, densification, and homogenization of the alloy core. Simultaneously, the outer amorphous carbon layer undergoes structural rearrangement at high temperature, transforming into more ordered graphitic carbon, achieving moderate graphitization, and ultimately forming core-shell structured particles with a magnetic alloy core and a carbon layer shell.

[0037] Step 4: Post-processing Dispersion and sieving: The heat-treated product is ground and dispersed, then sieved to obtain the carbon-coated Fe-Co-Ni-B magnetic alloy particles. The final product is micron-sized (typically below 25 microns) core-shell structured particles.

[0038] This invention aims to solve the challenges of compositional uniformity, structural consistency, and surface stability in multi-element alloy micron-sized particles through an innovative integrated alloy synthesis and carbon coating process. The core of this method lies in: firstly, obtaining Fe-Co-Ni-B alloy micron-sized particles with the desired phase composition and microstructure through precise component ratio and synthesis path control; then, generating a uniform, dense, and well-interfacially bonded graphite carbon coating layer in situ on the surface of the alloy particles through a controllable carbon source introduction and pyrolysis process. This coating layer effectively isolates the environment and significantly enhances the oxidation and corrosion resistance of the alloy particles. More importantly, by selecting appropriate carbon layer structures and properties (such as thickness, crystallinity, and conductivity), the magnetic interactions and magnetization kinetics between particles can be influenced, thereby synergistically regulating the macroscopic magnetic properties of the composite material (such as coercivity, permeability behavior, and high-frequency magnetic response), providing an effective solution for obtaining high-performance, high-stability novel magnetic composite materials.

[0039] The key to the successful preparation of carbon-coated Fe-Co-Ni-B core-shell structures in this invention lies in the precise control of the material formation mechanism. First, based on coordination chemistry principles, a β-diketone metal complex (acetylacetonate) is selected as the precursor. Its excellent solubility ensures that Fe, Co, and Ni metal ions achieve uniform molecular-level dispersion in ethanol. Cyclopentylboronic acid is introduced as a boron source, embedding boron into the precursor network in a coordination manner, laying the foundation for subsequent uniform doping. After a solvothermal reaction, the precursor undergoes hydrolysis / alcohololysis, forming a hydroxide / basic salt complex with a metal-oxygen bond network, thereby "solidifying" the spatial distribution of multiple elements at the nanoscale. Second, a crucial step is surface engineering using glucose: by controlling the glucose solution concentration (60-70 wt%) to the precursor mass ratio (1:5~1:15), its abundant hydroxyl groups coordinate with the metal oxide surface, achieving monolayer adsorption under mechanical stirring, followed by low-temperature drying to form a uniform coating. The subsequent heat treatment process consists of three stages: The first stage (450-500℃) involves the pyrolysis and carbonization of glucose, followed by dehydration and aromatization to form an amorphous carbon matrix; the second stage (600-700℃) involves the selective reduction of internal oxides through a gas-solid reaction within the carbon layer, while boron diffuses into the metal lattice; the third stage (800-1000℃) involves solid-state diffusion of metal atoms within the carbon layer to alloy, forming a face-centered cubic or body-centered cubic Fe-Co-Ni-B solid solution, while the carbon layer undergoes spc reaction. 2Hybridization transformation forms a continuous coating layer with a graphite microcrystalline structure. Finally, the entire process is carried out under an inert atmosphere to suppress metal oxidation and over-sintering. This strategy of "precursor molecular design - interfacial coordination coating - segmented phase transition control" achieves precise control from the molecular scale to the microstructure, ultimately obtaining a core-shell structure material with high core crystallinity, tight interfacial bonding, and a continuous and complete carbon shell. Its unique "magnetic core-dielectric shell" configuration provides an ideal platform for magnetic property control. This invention ultimately yields a core-shell structured functional material that combines strong magnetism and excellent oxidation resistance.

[0040] The present invention also provides carbon-coated Fe-Co-Ni-B magnetic alloy particles, which are prepared by the method described above. The particles have a distinct core-shell structure: the core is a Fe-Co-Ni-B multi-element magnetic alloy phase, and the outer shell is a continuous and dense carbon layer. The overall particles are submicron to micron in size, have good dispersibility, and are strongly magnetic.

[0041] This invention also provides an application of the carbon-coated Fe-Co-Ni-B magnetic alloy particles as a magnetic functional material, particularly in the fields of high-performance electromagnetic wave absorption and shielding materials, microwave absorption stealth, high-frequency soft magnetic composite materials, electromagnetic protection of electronic devices, magnetic recording media, and corrosion-resistant magnetic devices.

[0042] Example 1 First, the boron-doped precursor solution was prepared and a solvothermal reaction was carried out. The operation was conducted in a dry glove box at 25% humidity. 3.545 g of iron acetylacetone (Fe(acac)3) (corresponding to 10.0 mmol of Fe), 2.553 g of cobalt acetylacetone (Co(acac)2) (corresponding to 10.0 mmol of Co), and 2.569 g of nickel acetylacetone (Ni(acac)2) (corresponding to 10.0 mmol of Ni) were accurately weighed according to a Fe:Co:Ni molar ratio of 1:1:1. All raw materials were placed together in a 250 mL polytetrafluoroethylene-lined container, and 100 mL of anhydrous ethanol was added. The mixture was magnetically stirred until completely dissolved to form a homogeneous reddish-brown solution. Subsequently, 0.078 g of cyclopentylboronic acid (corresponding to 0.63 mmol of boron, approximately 2.0% of the total molar weight of the metals) was added to this solution, and stirring was continued for 30 minutes to ensure complete dissolution of the boric acid. The mixed solution was sealed in a 200 mL stainless steel reactor and placed in an oven where the temperature was increased to 160 °C at a rate of 5 °C / min and held for 2 hours for a solvothermal reaction. After the reaction, the mixture was allowed to cool naturally to room temperature. The resulting slurry was then transferred to an evaporating dish and dried in a vacuum drying oven at 60 °C for 24 hours. The dried lumps were then dry mechanically pulverized in a pulverizer at 120 rpm for 30 seconds. This process was repeated three times. Finally, the mixture was sieved through an 800-mesh standard sieve to obtain a homogeneous boron-doped pre-decomposition precursor powder.

[0043] The second step involves carbon precursor coating. A 65 wt% glucose aqueous solution was prepared as the carbon source. 10.00 g of the obtained precursor powder was accurately weighed and placed in a 250 mL three-necked flask. Under mechanical stirring at 300 rpm, a solution containing 1.00 g of glucose (approximately 1.538 g of a 65 wt% glucose aqueous solution) was slowly and uniformly added dropwise to the powder over 1.5 hours using a constant pressure dropping funnel. After the addition was complete, stirring was continued for 30 minutes to ensure uniform coating. The mixture was then transferred to a forced-air drying oven and dried at 80°C for 8 hours to obtain a glucose-coated composite precursor.

[0044] The third step involves in-situ carbonization and alloying heat treatment. The coated composite precursor powder is evenly spread in an alumina ceramic boat and placed in the isothermal zone of a tube furnace. After sealing the furnace tube, high-purity argon gas (purity ≥99.999%) is introduced at a flow rate of 200 sccm to replace the air for 30 minutes. Subsequently, under continuous argon flow (200 sccm), the temperature is increased according to the following program: first, the temperature is increased from room temperature to 480℃ at a rate of 4℃ / min and held at 480℃ for 45 minutes; then, the temperature is increased to 650℃ at a rate of 2.5℃ / min and held at 650℃ for 1.5 hours; finally, the temperature is increased to 920℃ at a rate of 3℃ / min and held at 920℃ for 2.5 hours. After the heat treatment is completed, heating is stopped, and the mixture is allowed to cool naturally to room temperature while maintaining an argon gas flow (100 sccm).

[0045] Finally, post-processing is performed. The cooled product block is lightly ground and dispersed, and then sieved using a 500-mesh standard sieve. The powder passing through the sieve is collected to obtain the final carbon-coated Fe-Co-Ni-B magnetic micron alloy particles.

[0046] Example 2 This embodiment provides a specific method for preparing carbon-coated Fe-Co-Ni-B magnetic micron alloy particles.

[0047] First, the boron-doped precursor solution was prepared and a solvothermal reaction was carried out. The operation was conducted in a dry glove box with 25% humidity. 3.545 g of iron acetylacetone (Fe(acac)3) (corresponding to 10.0 mmol of Fe), 2.553 g of cobalt acetylacetone (Co(acac)2) (corresponding to 10.0 mmol of Co), and 2.569 g of nickel acetylacetone (Ni(acac)2) (corresponding to 10.0 mmol of Ni) were accurately weighed according to a Fe:Co:Ni molar ratio of 1:1:1. All raw materials were placed together in a 250 mL polytetrafluoroethylene-lined container, and 100 mL of anhydrous ethanol was added. The mixture was magnetically stirred until completely dissolved to form a homogeneous reddish-brown solution. Subsequently, 0.039 g of cyclopentylboronic acid (corresponding to 0.315 mmol of boron, approximately 1.0% of the total molar weight of the metals) was added to this solution, and stirring was continued for 30 minutes to ensure complete dissolution of the boric acid. The experimental conditions, parameters, and operations for all subsequent steps, including solvothermal reaction, drying, pulverization, sieving, carbon coating, heat treatment, and post-treatment, were exactly the same as in Example 1.

[0048] Example 3 This embodiment provides a specific method for preparing carbon-coated Fe-Co-Ni-B magnetic micron alloy particles.

[0049] First, the boron-doped precursor solution was prepared and a solvothermal reaction was carried out. The operation was conducted in a dry glove box with 25% humidity. 3.545 g of iron acetylacetone (Fe(acac)3) (corresponding to 10.0 mmol of Fe), 2.553 g of cobalt acetylacetone (Co(acac)2) (corresponding to 10.0 mmol of Co), and 2.569 g of nickel acetylacetone (Ni(acac)2) (corresponding to 10.0 mmol of Ni) were accurately weighed according to a Fe:Co:Ni molar ratio of 1:1:1. All raw materials were placed together in a 250 mL polytetrafluoroethylene-lined container, and 100 mL of anhydrous ethanol was added. The mixture was magnetically stirred until completely dissolved to form a homogeneous reddish-brown solution. Subsequently, 0.156 g of cyclopentylboronic acid (corresponding to 1.26 mmol of boron, approximately 4.0% of the total molar weight of the metals) was added to this solution, and stirring was continued for 30 minutes to ensure complete dissolution of the boric acid. The experimental conditions, parameters, and operations for all subsequent steps, including solvothermal reaction, drying, pulverization, sieving, carbon coating, heat treatment, and post-treatment, were exactly the same as in Example 1.

[0050] Example 4 This embodiment provides a specific method for preparing carbon-coated Fe-Co-Ni-B magnetic micron alloy particles.

[0051] First, the boron-doped precursor solution was prepared and a solvothermal reaction was carried out. The operation was conducted in a dry glove box with 25% humidity. 3.545 g of iron acetylacetone (Fe(acac)3) (corresponding to 10.0 mmol of Fe), 2.553 g of cobalt acetylacetone (Co(acac)2) (corresponding to 10.0 mmol of Co), and 2.569 g of nickel acetylacetone (Ni(acac)2) (corresponding to 10.0 mmol of Ni) were accurately weighed according to a Fe:Co:Ni molar ratio of 1:1:1. All raw materials were placed together in a 250 mL polytetrafluoroethylene-lined container, and 100 mL of anhydrous ethanol was added. The mixture was magnetically stirred until completely dissolved to form a homogeneous reddish-brown solution. Subsequently, 0.312 g of cyclopentylboronic acid (corresponding to 2.52 mmol of boron, approximately 8.0% of the total molar weight of the metals) was added to this solution, and stirring was continued for 30 minutes to ensure complete dissolution of the boric acid. The experimental conditions, parameters, and operations for all subsequent steps, including solvothermal reaction, drying, pulverization, sieving, carbon coating, heat treatment, and post-treatment, were exactly the same as in Example 1.

[0052] Figure 1 The image shows a TEM image of carbon-coated Fe-Co-Ni-B magnetic micron alloy particles, indicating that the synthesized material is granular. Figure 2 The images and elemental distribution diagrams of carbon-coated Fe-Co-Ni-B magnetic micron alloy particles from Example 1 illustrate that the synthesized material is granular and contains four elements: Fe, Co, Ni, and B. Figure 3 The XPS spectrum of carbon-coated Fe-Co-Ni-B magnetic micron alloy particles from Example 1 further illustrates that the sample contains four elements, forming an alloy structure.

[0053] The hysteresis loop of the samples was tested at room temperature using a physical performance testing system (PPMS). The magnetic field scanning range was -2T to +2T, and a continuous uniform scanning mode was used. Before testing, the powder samples obtained in each embodiment were sealed in non-magnetic capsules and compacted to eliminate sample looseness and magnetic anisotropy interference. Appropriate sensitivity and sampling rate were set to ensure smooth curve acquisition and stable and reliable data.

[0054] Figure 4 It is the hysteresis loop of carbon-coated Fe-Co-Ni-B magnetic micron alloy particles (Example 1). Figure 5 The hysteresis loop of carbon-coated Fe-Co-Ni-B magnetic micron alloy particles (Example 2). Figure 6 It is the hysteresis loop of carbon-coated Fe-Co-Ni-B magnetic micron alloy particles (Example 3). Figure 7 It is the hysteresis loop of carbon-coated Fe-Co-Ni-B magnetic micron alloy particles (Example 4).

[0055] The magnetic performance parameters of each embodiment are shown in Table 1: Table 1

[0056] 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 carbon-coated Fe-Co-Ni-B magnetic micron alloy particles, characterized in that, Includes the following steps: (1) Dissolve iron acetylacetone, cobalt acetylacetone, and nickel acetylacetone in anhydrous ethanol, then add cyclopentylboric acid and dissolve it to obtain a mixed solution. Heat the mixed solution to 150~180℃ for a solvothermal reaction. After the reaction is completed, post-processing is performed to obtain boron-doped pre-decomposition precursor powder. Iron acetylacetone, cobalt acetylacetone, and nickel acetylacetone are added in a Fe:Co:Ni metal molar ratio of 1:1:

1. The amount of boron added in cyclopentylboric acid is controlled to be 1%~8% of the total molar amount of iron, cobalt, and nickel metals. (2) Add glucose aqueous solution dropwise to pre-decomposed precursor powder under stirring and mix evenly so that glucose solution is uniformly adsorbed and coated on the powder surface. Then dry to obtain a composite precursor uniformly coated with glucose. (3) The composite precursor is subjected to programmed temperature rise heat treatment in an inert atmosphere or a weak reducing atmosphere to carbonize glucose to form a carbon coating layer and graphitize it. The Fe-Co-Ni-B alloy phase is formed by carbothermal reduction to obtain carbon-coated Fe-Co-Ni-B magnetic micron alloy particles with a core-shell structure. The programmed temperature rise heat treatment includes the following three stages: The first stage involves maintaining a constant temperature of 450~500℃ for 30~60 minutes. The second stage involves maintaining a constant temperature of 600-700℃ for 1-2 hours. The third stage involves maintaining a constant temperature of 800~1000℃ for 1~3 hours.

2. The method for preparing carbon-coated Fe-Co-Ni-B magnetic micron alloy particles according to claim 1, characterized in that, The solvothermal reaction in step (1) takes 1.5 to 3 hours.

3. The method for preparing carbon-coated Fe-Co-Ni-B magnetic micron alloy particles according to claim 1, characterized in that, The concentration of the glucose aqueous solution in step (2) is 60~70wt%.

4. The method for preparing carbon-coated Fe-Co-Ni-B magnetic micron alloy particles according to claim 1, characterized in that, Step (2) The mass ratio of glucose to pre-decomposed precursor powder is 1:5 to 1:

15.

5. The method for preparing carbon-coated Fe-Co-Ni-B magnetic micron alloy particles according to claim 1, characterized in that, Step (2) Add the glucose solution dropwise to the precursor powder over 1.5 hours with stirring, and continue stirring for 30 minutes after the addition is complete.

6. A carbon-coated Fe-Co-Ni-B magnetic micron alloy particle, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 5, and has a core-shell structure, with the core being an Fe-Co-Ni-B multi-element magnetic alloy phase and the outer shell being a continuous and dense carbon layer.

7. An application of the carbon-coated Fe-Co-Ni-B magnetic micron alloy particles as described in claim 6, characterized in that, It can be used as a magnetic functional material.

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