Carbon-coated FeCo-based alloy and preparation method thereof

Abstract

The invention discloses a carbon-coated FeCo-based alloy and a preparation method thereof, and belongs to the field of electromagnetic functional materials. The preparation method comprises the following steps: drying a mixed solution prepared from Fe salt, Co salt, doped metal salt and polyvinylpyrrolidone into fluffy powder by using a spray drying method, annealing the powder, reducing the powder into a metal alloy in a thermal atmosphere, further coating a polymer on the metal surface through a polymerization reaction, and finally carrying out heat preservation and carbonization in an inert atmosphere to obtain the Fe-Co-doped metal alloy. And the FeCo-based alloy coated with the carbon is obtained. The carbon-coated FeCo-based alloy provided by the invention has excellent electromagnetic wave absorption performance due to good matching of dielectric and magnetic properties, and has a wide application prospect in the electromagnetic field.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic functional materials, specifically relating to a carbon-coated FeCo-based alloy and its preparation method. Background Technology

[0002] Iron-cobalt (FeCo) alloys are widely used in transformers, inductors, and high-frequency magnetic devices due to their high saturation magnetization, high Curie temperature, and excellent soft magnetic properties. However, traditional FeCo alloys still have many limitations in high-frequency applications. For example, under high-frequency conditions, the alloy's high conductivity leads to significant eddy current losses, reducing device efficiency. Furthermore, FeCo alloys have poor ductility and are prone to brittle fracture, limiting their application in flexible electronic devices. To improve these issues, existing technologies attempt to suppress eddy current effects and increase ductility by doping with large amounts of non-magnetic elements or employing multilayer thin-film structures; however, such methods significantly reduce the material's electromagnetic response performance. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a carbon-coated FeCo-based alloy and its preparation method.

[0004] The objective of this invention is achieved through the following technical solution: a method for preparing carbon-coated FeCo-based alloys, comprising the following steps:

[0005] Fe salt, Co salt, doped metal salt and polyvinylpyrrolidone were uniformly dissolved in water to obtain a mixed solution;

[0006] The mixed solution was spray-dried to obtain a powder sample;

[0007] The powder sample was annealed in air to obtain a metal oxide sample;

[0008] FeCo-based alloys were obtained by reducing metal oxide samples in a hot atmosphere;

[0009] FeCo-based alloys were dispersed in a mixed solution of water and ethanol. Polymer monomers were added under alkaline conditions. After the reaction was complete, the mixture was centrifuged, and the precipitate was washed and dried to obtain polymer-coated FeCo-based alloys. The mass ratio of FeCo-based alloys to the total mass of polymer monomers was 1:2.3~3.2.

[0010] The polymer-coated FeCo-based alloy was carbonized under an inert atmosphere to obtain a carbon-coated FeCo-based alloy.

[0011] Furthermore, in the mixed solution, the total concentration of Fe ions and Co ions is maintained at 0.2~1.8 mol / L, and the concentration of polyvinylpyrrolidone is maintained at 50~450 mmol / L, and the mixed solution is ultrasonically stirred until homogeneous.

[0012] Furthermore, the molar ratio of Fe ions to Co ions in the mixed solution is 1:1, and the molar ratio of doped metal ions to Fe ions or Co ions is 4% to 8 / 45; the doped metal in the doped metal salt includes one or more of Ni, Cu, Zn, Al and Mn.

[0013] Furthermore, the spray temperature of the spray drying device is set to 120~180℃, the air pump is adjusted to 100%, and the feed rate is 1~25ml / min.

[0014] Furthermore, the annealing conditions are controlled by holding the obtained powder sample at 500~700℃ for 1~10h, with a heating rate of 2~10℃ / min.

[0015] Furthermore, the annealing process is carried out using a muffle furnace, and the reduction process is carried out using a tube furnace.

[0016] Furthermore, the reduction conditions were controlled by holding the metal oxide sample at 500-700℃ in an argon-hydrogen atmosphere for 3-10 hours, with the hydrogen gas fraction being 5-50% and the heating rate being 2-10℃ / min.

[0017] Furthermore, the volume ratio of water to ethanol in the mixed solution of water and ethanol is 1:0.75~1.5; the polymerization monomers include resorcinol and formaldehyde; and the polymerization reaction time is 24~48h.

[0018] Furthermore, the conditions for controlling carbonization include: placing the polymer-coated FeCo-based alloy in a tube furnace and holding it at 500~650℃ for 4~10h under an inert atmosphere, with the heating rate maintained at 3~10℃ / min.

[0019] The present invention also provides carbon-coated FeCo-based alloys prepared by the above method.

[0020] The beneficial effects of this invention are as follows: This invention provides a method for preparing a carbon-coated FeCo-based alloy. In this method, a good interfacial bond is achieved on the surface of the FeCo-based alloy through polymerization coating and in-situ carbonization reduction, thereby coating a dense carbon layer. This optimizes the interfacial structure of the material and achieves impedance matching of dielectric / magnetic properties. Furthermore, the addition of a small amount of dissimilar metal elements to the FeCo alloy maintains the magnetic properties while increasing dielectric polarization behavior, promoting the material's response to electromagnetic waves, and thus achieving strong absorption performance of electromagnetic waves.

[0021] The carbon-coated FeCo-based alloys prepared by this method have good structural stability and impedance matching conditions. Furthermore, the doping of different elements in the FeCo phase optimizes the electromagnetic response of the material, giving it great advantages and application potential in electromagnetic shielding and electromagnetic wave absorption. Attached Figure Description

[0022] Figure 1 SEM image of the carbon-coated FeCo-based alloy prepared in Example 1;

[0023] Figure 2 The XRD pattern of the carbon-coated FeCo-based alloy prepared in Example 1;

[0024] Figure 3 The Raman spectrum of the carbon-coated FeCo-based alloy prepared in Example 1;

[0025] Figure 4 The hysteresis loop diagram of the carbon-coated FeCo-based alloy prepared in Example 1;

[0026] Figure 5 The image shows the reflection loss curve of the carbon-coated FeCo-based alloy prepared in Example 1. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0028] This invention provides a method for preparing carbon-coated FeCo-based alloys, comprising the following steps:

[0029] (1) Dissolve Fe salt, Co salt, doped metal salt and polyvinylpyrrolidone uniformly in water to obtain a mixed solution;

[0030] Specifically, Fe salt, Co salt, doped metal salt, and polyvinylpyrrolidone are dissolved in an aqueous solution to form a mixed solution. In the mixed solution, the total concentration of Fe ions and Co ions is maintained at 0.2~1.8 mol / L, the concentration of polyvinylpyrrolidone is 50~450 mmol / L (calculated based on monomer molecular weight), the molar ratio of iron ions to cobalt ions is 1:1, and the molar ratio of doped metal ions to Fe ions or Co ions is 4%~8 / 45. The mixed solution is then ultrasonically stirred until homogeneous.

[0031] The doped metal ions in the doped metal salt include one or more of Ni, Cu, Zn, Al, and Mn.

[0032] (2) The mixed solution was spray-dried to obtain a powder sample;

[0033] Specifically, the mixed solution is spray-dried using a spray drying device to obtain a powder sample. The spray temperature of the spray drying device is set to 120~180℃, the vacuum pump is adjusted to 100%, and the feed rate is 1~25ml / min. This step refines the sample particles through spray drying, facilitating a more uniform reaction during the subsequent annealing process.

[0034] (3) Anneal the powder sample in air to obtain a metal oxide sample;

[0035] Specifically, the obtained powder sample is placed in a muffle furnace and held at 500~700℃ for 1~10h with a heating rate of 2~10℃ / min. After natural cooling, a metal oxide sample is obtained. This annealing process can remove impurities and promote crystallization.

[0036] (4) The metal oxide sample was reduced in a hot atmosphere to obtain the FeCo-based alloy;

[0037] Specifically, the metal oxide sample is placed in a tube furnace and held at 500-700℃ for 3-10 hours in an argon-hydrogen atmosphere, where the hydrogen gas fraction is 5-50% and the heating rate is 2-10℃ / min. Under the reducing atmosphere, the metal oxide is reduced by hydrogen to a metal alloy, thus obtaining the FeCo-based alloy.

[0038] (5) Disperse the FeCo-based alloy in a mixed solution of water and ethanol, add the polymer monomer under alkaline conditions, and after the reaction is complete, centrifuge and wash and dry the precipitate to obtain the polymer-coated FeCo-based alloy (P@FeCo-based alloy).

[0039] Specifically, the FeCo-based alloy is dispersed in a mixed solution of water and ethanol at a volume ratio of 1:0.75~1.5. Polymer monomers are added under alkaline conditions. Alkaline conditions are provided by adding an alkaline substance such as ammonia. The polymer monomers undergo a phenolic polymerization reaction on the metal surface. After 24~48 hours of polymerization, the reaction is complete, forming a polymer shell on the metal surface. The resulting mixture is then centrifuged to obtain a precipitate. The precipitate is washed at least three times with water and ethanol until the supernatant is colorless after centrifugation. Finally, the centrifuged product is dried overnight in a vacuum drying oven to obtain the polymer-coated FeCo-based alloy. The polymer monomers are resorcinol and formaldehyde; the mass ratio of the FeCo-based alloy to the total mass of the polymer monomers is 1:2.3~3.2.

[0040] (6) The polymer-coated FeCo-based alloy is carbonized in an inert atmosphere to obtain a carbon-coated FeCo-based alloy (C@FeCo-based composite material).

[0041] Specifically, the polymer-coated FeCo-based alloy is placed in a tube furnace and held at 500–650 °C for 4–10 h in an inert atmosphere (Ar or N2), with a heating rate maintained at 3–10 °C / min, to obtain a carbon-coated FeCo-based alloy. Under the high-temperature inert atmosphere, the polymer shell on the metal surface is gradually carbonized, thereby shrinking on the metal surface to form a compact carbon shell.

[0042] This method utilizes spray drying to atomize and dry a homogeneous mixture containing multiple metal salts such as Fe and Co and polyvinylpyrrolidone to obtain a fluffy powder sample. Then, it is annealed in air to remove impurities and promote crystallization. Next, it is reduced to obtain an FeCo-based alloy. Further, a polymer layer is coated on the surface of the alloy through a polymerization reaction. Finally, carbonization is performed to obtain a carbon-coated FeCo-based alloy.

[0043] Based on the above preparation method, the present invention also provides a carbon-coated FeCo-based alloy, which is a magnetic / dielectric composite material with good impedance matching and electromagnetic response capabilities; due to the good matching of dielectric and magnetic properties, it has excellent electromagnetic wave absorption performance and is suitable for high-frequency electronic devices, electromagnetic shielding and absorption, sensors and new energy conversion and other fields.

[0044] Example 1: A method for preparing a carbon-coated FeCo-based alloy, comprising the following steps:

[0045] (1) Dissolve 0.1 mol FeCl3, 0.1 mol CoCl2, 2 mmol CuSO4, 2 mmol Zn(NO3)2 and 50 mmol polyvinylpyrrolidone (calculated by monomer molecular weight) in 1 L of aqueous solution, and then sonicate the solution for 30 min to obtain a homogeneous mixed solution.

[0046] (2) Place the mixed solution obtained in step (1) on the spray drying device, insert the inlet pipe into the bottom of the mixed solution, turn on the air compressor and vacuum pump, adjust the air pump to 100%, set the spray temperature to 180℃, and the feed rate to 1ml / min. When the temperature rises to the set temperature, start feeding. Finally, obtain the powder sample in the collection bottle.

[0047] (3) Place the powder sample obtained in step (2) in a muffle furnace and keep it at 500℃ for 10h with a heating rate of 5℃ / min to obtain a metal oxide sample.

[0048] (4) Place the metal oxide sample obtained in step (3) in a tube furnace and keep it at 600°C for 5 hours in an argon-hydrogen (10% H2) atmosphere. The heating rate is 5°C / min. Once the furnace temperature drops to room temperature, the FeCo-based alloy (Cu and Zn doped FeCo-based alloy) can be obtained.

[0049] (5) Add 1g of FeCo-based alloy obtained in step (4) to a mixed solution consisting of 800mL water and 600mL ethanol and stir ultrasonically for 30min. Then add 10mL ammonia (28wt.%) and 1.5g resorcinol and stir for 30min. Then add 2mL formaldehyde (37% aqueous solution) and continue stirring to allow polymerization to occur for 24h to obtain a mixed solution. Then centrifuge the mixed solution and wash it with water and ethanol at least three times until the supernatant after centrifugation is colorless. Finally, place the centrifuged product in a vacuum drying oven overnight to dry it, thus obtaining the polymer-coated FeCo-based alloy (P@FeCo-based alloy).

[0050] (6) The polymer-coated FeCo-based alloy was placed in a tube furnace and kept at 600°C for 5 hours in an argon atmosphere. The heating rate was maintained at 5°C / min. Finally, carbon-coated FeCo-based alloy (carbon-coated Cu and Zn doped FeCo alloy) was obtained.

[0051] Example 2: A method for preparing a carbon-coated FeCo-based alloy, comprising the following steps:

[0052] (1) Dissolve 0.5 mol Fe(NO3)3, 0.5 mol Co(NO3)2, 20 mmol Cu(NO3)2, 20 mmol Zn(NO3)2, 10 mmol Mn(NO3)2 and 250 mmol polyvinylpyrrolidone (calculated by monomer molecular weight) in 1 L of aqueous solution, and then sonicate the solution for 30 min to obtain a homogeneous mixed solution.

[0053] (2) Place the mixed solution obtained in step (1) on the spray drying device, insert the liquid inlet tube into the bottom of the mixed solution, turn on the air compressor and vacuum pump, adjust the air pump to 100%, set the spray temperature to 150℃, and the feeding rate to 10ml / min. When the temperature rises to the set temperature, start feeding. Finally, obtain the powder sample in the collection bottle.

[0054] (3) Place the powder sample obtained in step (2) in a muffle furnace and keep it at 600℃ for 5h with a heating rate of 10℃ / min to obtain a metal oxide sample.

[0055] (4) Place the metal oxide sample obtained in step (3) in a tube furnace and keep it at 700°C for 3 hours in an argon-hydrogen (5% H2) atmosphere. The heating rate is 10°C / min. Once the furnace temperature drops to room temperature, the FeCo-based alloy (Cu, Zn, Mn-doped FeCo-based alloy) can be obtained.

[0056] (5) Add 8g of FeCo-based alloy obtained in step (4) to a mixed solution consisting of 6L water and 5L ethanol and stir ultrasonically for 30min. Then add 100mL ammonia (28wt.%) and 17g resorcinol and stir for 30min. Then add 20mL formaldehyde (37% aqueous solution) and continue stirring to allow polymerization to occur for 30h to obtain a mixed solution. Then centrifuge the mixed solution and wash it with water and ethanol at least three times until the supernatant after centrifugation is colorless. Finally, place the centrifuged product in a vacuum drying oven overnight to dry and obtain the polymer-coated FeCo-based alloy (P@FeCo-based alloy).

[0057] (6) The polymer-coated FeCo-based alloy was placed in a tube furnace and kept at 650°C for 4 hours in an argon atmosphere. The heating rate was maintained at 10°C / min. Finally, carbon-coated FeCo-based alloy (carbon-coated Cu, Zn, Mn doped FeCo alloy) was obtained.

[0058] Example 3: A method for preparing a carbon-coated FeCo-based alloy, comprising the following steps:

[0059] (1) Dissolve 0.9 mol Fe(NO3)3, 0.9 mol Co(NO3)2, 40 mmol Cu(NO3)2, 40 mmol Zn(NO3)2, 40 mmol Mn(NO3)2, 40 mmol Al(NO3)3 and 450 mmol polyvinylpyrrolidone (calculated by monomer molecular weight) in 1 L of aqueous solution, and then sonicate the solution for 30 min to obtain a homogeneous mixed solution.

[0060] (2) Place the mixed solution obtained in step (1) on the spray drying device, insert the inlet pipe into the bottom of the mixed solution, turn on the air compressor and vacuum pump, adjust the air pump to 100%, set the spray temperature to 120℃, and the feed rate to 25ml / min. When the temperature rises to the set temperature, start feeding. Finally, obtain the powder sample in the collection bottle.

[0061] (3) Place the powder sample obtained in step (2) in a muffle furnace and keep it at 700℃ for 1h with a heating rate of 2℃ / min to obtain a metal oxide sample.

[0062] (4) Place the metal oxide sample obtained in step (3) in a tube furnace and keep it at 500°C for 10 hours in an argon-hydrogen (50% H2) atmosphere. The heating rate is 2°C / min. Once the furnace temperature drops to room temperature, the FeCo-based alloy (Cu, Zn, Mn, Al doped FeCo-based alloy) can be obtained.

[0063] (5) Add 5g of FeCo-based alloy obtained in step (4) to a mixed solution of 2L water and 3L ethanol and stir ultrasonically for 30min. Then add 50mL ammonia (28wt.%) and 10g resorcinol and stir for 30min. Then add 15mL formaldehyde (37% aqueous solution) and continue stirring to carry out the polymerization reaction for 48h to obtain a mixed solution. Then centrifuge the mixed solution and wash it with water and ethanol at least three times until the supernatant after centrifugation is colorless. Finally, place the centrifuged product in a vacuum drying oven overnight to dry and obtain the polymer-coated FeCo-based alloy (P@FeCo-based alloy).

[0064] (6) The polymer-coated FeCo-based alloy was placed in a tube furnace and kept at 500°C for 10 hours in an argon atmosphere. The heating rate was maintained at 3°C / min. Finally, carbon-coated FeCo-based alloy (carbon-coated Cu, Zn, Mn, Al doped FeCo alloy) was obtained.

[0065] In specific implementation, compared with each embodiment, the type, quantity and ratio of metal salts added in step (1) can be changed, the amount of polyvinylpyrrolidone added can be changed, the volume of aqueous solution can be changed, and the ultrasonic stirring time can be changed; the temperature and feed rate set in step (2) can be changed; the heating temperature, holding time and heating rate in step (3) can be changed; the hydrogen content, temperature, holding time and heating rate in the reaction atmosphere in step (4) can be changed; the mass of the alloy in step (5) can be changed, the volume of water and ethanol can be changed, the amount of ammonia, resorcinol and formaldehyde can be changed, and the reaction time can be changed; the heating temperature, holding time and heating rate in step (6) can be changed; other aspects are the same as in embodiments 1 to 3.

[0066] The carbon-coated FeCo-based alloy prepared in Example 1 was tested and its performance was analyzed. The details are as follows.

[0067] Figure 1 SEM image of the carbon-coated FeCo-based alloy prepared in Example 1; from Figure 1As can be seen, the carbon-coated FeCo-based alloy prepared in Example 1 exhibits irregular blocky and agglomerated morphologies; the surface of the blocks is rough, with a porous or sponge-like structure, showing complex micro-textures; the size of these blocks is in the micrometer range, with the larger blocks having a diameter close to 40 μm, while the smaller ones are significantly smaller than this size, showing a certain size distribution range, reflecting the micro-morphology of the samples prepared in Example 1.

[0068] Figure 2 The XRD pattern of the carbon-coated FeCo-based alloy prepared in Example 1; from Figure 2 As can be seen from the data, the carbon-coated FeCo-based alloy prepared in Example 1 has three distinct diffraction peaks, corresponding to the (110), (200) and (211) crystal planes, respectively. The strongest diffraction peak appears around 45°, corresponding to the (110) crystal plane, which is one of the main diffraction characteristics of the FeCo phase, indicating that the sample prepared in Example 1 has the FeCo phase.

[0069] Figure 3 The Raman spectrum of the carbon-coated FeCo-based alloy prepared in Example 1; from Figure 3 It can be seen from this that the Raman displacement is approximately 1350 cm. -1 and 1600cm -1 There are obvious intensity peaks nearby, and the curve rises and falls relatively steeply at the peaks. Between the peaks, the intensity is relatively low and changes relatively gently, indicating that the polymer in the sample prepared in Example 1 has achieved full carbonization.

[0070] Figure 4 The hysteresis loop diagram of the carbon-coated FeCo-based alloy prepared in Example 1; from Figure 4 As can be seen, the hysteresis loop of the carbon-coated FeCo-based alloy prepared in Example 1 exhibits a typical S-shape. When the magnetic field strength gradually increases from a negative value, the magnetization begins to change slowly. Then, when the magnetic field strength approaches zero, the magnetization rises rapidly. After that, as the magnetic field strength continues to increase, the growth of the magnetization slows down and tends to saturate. When the magnetic field strength gradually decreases from a positive value, it follows a similar reverse trend. It can be seen that the sample prepared in Example 1 has typical soft magnetism.

[0071] Figure 5 The graph shows the reflection loss curves of the carbon-coated FeCo-based alloy prepared in Example 1 at different coating thicknesses. It can be seen that the strongest reflection loss value is around -50dB, which indicates that the sample prepared in Example 1 has a strong electromagnetic wave absorption capability.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon-coated FeCo-based alloy, characterized by, The method comprises the following steps: Fe, Co, doping metal salts and polyvinylpyrrolidone are uniformly dissolved in water to obtain a mixed solution; The mixed solution is spray dried to obtain a powder sample; The powder sample is annealed in air to obtain a metal oxide sample; The metal oxide sample is reduced in a hot atmosphere to obtain a FeCo-based alloy; The FeCo-based alloy is dispersed in a mixed solution of water and ethanol, and a polymerization monomer is added under alkaline conditions. After sufficient reaction, centrifugation is performed, and the precipitate is washed and dried to obtain a polymer-coated FeCo-based alloy. The mass ratio of the FeCo-based alloy to the total mass of the polymerization monomer is 1:2.3-3.2; The polymer-coated FeCo-based alloy is carbonized under an inert atmosphere to obtain a carbon-coated FeCo-based alloy.

2. The method of claim 1, wherein the carbon-coated FeCo-based alloy is prepared by the steps of: preparing a FeCo-based alloy; and coating the FeCo-based alloy with carbon. In the mixed solution, the total concentration of Fe ions and Co ions is maintained at 0.2-1.8 mol / L, and the concentration of polyvinylpyrrolidone is 50-450 mmol / L. The mixed solution is uniformly stirred by ultrasonic stirring.

3. The method for preparing a carbon-coated FeCo-based alloy according to claim 1, characterized in that, The molar ratio of Fe ions to Co ions in the mixed solution is 1:1, and the molar ratio of doping metal ions to Fe ions or Co ions is 4%-8 / 45. The doping metals in the doping metal salt include one or more of Ni, Cu, Zn, Al and Mn.

4. The method of claim 1, wherein the carbon-coated FeCo-based alloy is prepared by a process comprising: preparing a FeCo-based alloy; and coating the FeCo-based alloy with carbon. The spray temperature of the spray drying device is set to 120-180℃, the air pump is adjusted to 100%, and the feeding rate is 1-25 ml / min.

5. The method of claim 1, wherein the carbon-coated FeCo-based alloy is prepared by a process comprising: preparing a FeCo-based alloy; and coating the FeCo-based alloy with carbon. The annealing conditions are controlled to heat the obtained powder sample at 500-700℃ for 1-10 h, and the heating rate is 2-10℃ / min.

6. The method of claim 1, wherein the carbon-coated FeCo-based alloy is prepared by a process comprising: The annealing device is a muffle furnace, and the reduction device is a tube furnace.

7. The method of claim 1, wherein the carbon-coated FeCo-based alloy is prepared by a process comprising: preparing a FeCo-based alloy; and coating the FeCo-based alloy with carbon. The reduction conditions are controlled to heat the metal oxide sample in an argon-hydrogen atmosphere at 500-700℃ for 3-10 h, wherein the volume fraction of hydrogen is 5-50%, and the heating rate is 2-10℃ / min.

8. The method for preparing a carbon-coated FeCo-based alloy according to claim 1, characterized in that, The volume ratio of water to ethanol in the mixed solution of water and ethanol is 1:0.75-1.

5. The polymerization monomer includes resorcinol and formaldehyde. The polymerization reaction time is 24-48 h.

9. The method of claim 1, wherein the carbon-coated FeCo-based alloy is prepared by a process comprising: preparing a FeCo-based alloy; and coating the FeCo-based alloy with carbon. The carbonization conditions include placing the polymer-coated FeCo-based alloy in a tube furnace, heating at 500-650℃ for 4-10 h under an inert atmosphere, and maintaining the heating rate at 3-10℃ / min.

10. The carbon-coated FeCo-based alloy prepared by the preparation method of any one of claims 1-9.

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