Flaky FeCoB alloy wave-absorbing material and preparation method thereof

Abstract

The invention discloses a flaky FeCoB alloy wave-absorbing material and a preparation method thereof, in the flaky FeCoB alloy wave-absorbing material, the molar percentage content of Fe element is 30-69%, the molar percentage content of Co element is 30-69%, the molar percentage content of B element is 1-10%, the sum of all the elements is 100%, the microstructure of the flaky FeCoB alloy wave-absorbing material is flaky particles, the particle size of the flaky particles is 3-50 [mu] m, and the thickness of the flaky particles is less than 1 [mu] m. The flaky FeCoB alloy wave-absorbing material provided by the invention has good absorption performance on electromagnetic waves in the frequency band of 2-8GHz under the condition of relatively small thickness, and the number of alloy principal elements is small, so that the production cost can be reduced, and the high magnetic loss capability of the alloy can be kept.

Description

Technical Field

[0001] This invention belongs to the field of cobalt-containing iron-based alloy technology, specifically relating to a sheet-like FeCoB alloy microwave absorbing material and its preparation method. Background Technology

[0002] Electromagnetic waves in the megahertz to gigahertz frequency band have been widely used in the communications field due to their excellent transmission performance, such as the 600MHz~3GHz electromagnetic waves used in the 5G low-frequency band. However, the resulting electromagnetic pollution not only interferes with the normal operation of electronic equipment but may also have potential impacts on human health. Therefore, accelerating the development of high-performance electromagnetic wave absorbing materials is key to solving this problem.

[0003] FeCo soft magnetic alloys possess the potential to be used in the fabrication of high-performance electromagnetic wave absorbing materials due to their high saturation magnetization and high magnetic loss capability. However, the material itself has inherent limitations such as poor impedance matching characteristics and low resonant frequency, resulting in weak electromagnetic wave absorption capabilities. Therefore, improving its impedance matching characteristics through optimizing the fabrication process and controlling the alloy composition is an effective strategy to enhance the electromagnetic wave absorption performance of FeCo soft magnetic alloys.

[0004] Currently, most studies on improving the microwave absorption performance of FeCo soft magnetic alloys focus on the 8–18 GHz frequency band, while research on improving the absorption performance in the 2–8 GHz frequency band is relatively limited. For example, CN119681271A discloses a method for preparing FeCoNiMnAl high-entropy alloy powder with microwave absorption properties, which can achieve microwave absorption in the 8–18 GHz frequency band with a thickness of 1.5 mm. The absorption is 36.71 dB, with an effective absorption bandwidth of 4.40 GHz. However, below 4 GHz, a thickness of at least 3.5 mm is required to achieve absorption performance. Furthermore, high-entropy alloys are generally prepared through mechanical alloying, which suffers from drawbacks such as low alloying degree, long processing time, high cost, and high energy consumption. Additionally, the multiple principal components in high-entropy alloys make performance control difficult, hindering large-scale production. Therefore, there is an urgent need to develop an alloy material with a simple composition and good microwave absorption performance in the 2–8 GHz range. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing a sheet-like FeCoB alloy microwave absorbing material and its preparation method. The sheet-like FeCoB alloy microwave absorbing material has a high degree of alloying and good microwave absorption performance in the 2~8GHz frequency band. It is prepared by vacuum induction melting and two ball milling methods, which has the advantages of low cost, short production cycle, low energy consumption and easy performance control.

[0006] The first aspect of this invention provides a sheet-like FeCoB alloy microwave absorbing material, wherein the molar percentage content of Fe is 30-69%, the molar percentage content of Co is 30-69%, the molar percentage content of B is 1-10%, and the sum of all elements is 100%. Its microstructure is sheet-like particles with a particle size of 3-50 μm and a thickness of less than 1 μm.

[0007] According to the above scheme, the sheet-like FeCoB alloy microwave absorbing material achieves an absorption performance of -10.84 to -42.76 dB in the 2 to 8 GHz frequency band when the thickness is 1.0 to 4.0 mm.

[0008] The second aspect of this invention provides a method for preparing the above-mentioned sheet-like FeCoB alloy microwave absorbing material, the specific steps of which are as follows: 1) Weigh out Fe blocks, Co blocks, and B blocks according to the specified proportions and set aside; 2) The Fe block, Co block and B block weighed in step 1) are subjected to induction melting, and FeCoB alloy ingots are obtained by casting. 3) After mechanically crushing the FeCoB alloy ingot obtained in step 2), the FeCoB alloy powder is obtained by ball milling once. The FeCoB alloy powder is then ball milled a second time to obtain sheet-like FeCoB alloy microwave absorbing material.

[0009] According to the above scheme, the purity of Fe block, Co block and B block mentioned in step 1) is ≥99.9wt%.

[0010] According to the above scheme, the induction melting conditions for step 2) are as follows: using high-purity argon gas with a purity of 99.999 vol% as the protective atmosphere, the gas pressure is -0.1 to -0.05 MPa, the melting temperature is 1500 to 1700℃, and the melting time is 10 to 30 min.

[0011] According to the above scheme, the process conditions for step 3) of the ball milling are as follows: stainless steel balls are used as the ball milling medium, anhydrous ethanol is used as the process control agent, the ball-to-material ratio is 10:1~20:1, the mass ratio of FeCoB alloy ingot to anhydrous ethanol is 1:1~1:4, the ball milling speed is 200~400 r / min, and the ball milling time is 10~30 h.

[0012] According to the above scheme, the secondary ball milling process conditions in step 3) are as follows: stainless steel balls are used as the ball milling medium, anhydrous ethanol is used as the process control agent, the ball-to-material ratio is 10:1~20:1, the mass ratio of FeCoB alloy powder to anhydrous ethanol is 1:1~1:4, the ball milling speed is 200~400 r / min, and the ball milling time is 10~30 h.

[0013] The third aspect of this invention provides the application of the above-mentioned sheet-like FeCoB alloy microwave absorbing material in the fields of stealth materials, communications, and information security.

[0014] The FeCoB alloy prepared in this invention belongs to the magnetic loss type electromagnetic wave absorbing material, mainly attenuating electromagnetic wave energy through magnetic loss mechanisms such as eddy current loss, natural resonance loss, and exchange resonance loss. Therefore, maintaining good soft magnetic properties is crucial for improving the alloy's wave absorption performance. FeCo alloy is a typical soft magnetic material, and boron (B) is a non-ferromagnetic element. Adding boron has little impact on the soft magnetic properties of FeCo alloy, thus maintaining its excellent soft magnetic properties. Furthermore, adding an appropriate amount of boron to the FeCo alloy can, on the one hand, dissolve into the FeCo alloy lattice to form lattice defects that induce dipole polarization; on the other hand, boron forms a small amount of second-phase boron compounds with Fe or Co and is uniformly distributed in the FeCo alloy matrix, which can greatly reduce the alloy's conductivity and enhance interfacial polarization. Introducing boron into the alloy can effectively enhance its dielectric loss capability and improve its impedance matching characteristics, allowing more electromagnetic waves to penetrate into the alloy powder material and be absorbed.

[0015] This invention produces a sheet-like powder material from FeCoB alloy through two ball milling processes. According to the Snoek limit formula, the out-of-plane anisotropy field of the material after sheet milling is much larger than that of the in-plane anisotropy field, which is beneficial to improving the material's resonant frequency and permeability, thereby enhancing its magnetic loss capability. Simultaneously, the crushing and cold welding effects during ball milling introduce numerous lattice defects into the alloy crystals. These defects can act as polarization sites, inducing polarization and enhancing the alloy's dielectric loss capability. Furthermore, the microstructure formed on the surface of the sheet-like particles through ball milling increases the propagation path of electromagnetic waves within the material, further improving the alloy's wave absorption performance. Through the synergistic effect of dielectric and magnetic losses, the alloy's loss capability is improved while its impedance matching characteristics are optimized.

[0016] The beneficial effects of this invention are as follows: 1. The sheet-like FeCoB alloy microwave absorbing material provided by this invention has good absorption performance for electromagnetic waves in the 2~8GHz frequency band at a relatively thin thickness. Moreover, the small number of main alloy components and the addition of a high proportion of iron and cobalt not only reduce production costs but also help maintain the high magnetic loss capability of the alloy; 2. This invention prepares sheet-like FeCoB alloy microwave absorbing material by induction melting and two ball milling processes, which has the advantages of simple process, short production cycle, low energy consumption and low environmental pollution. Attached Figure Description

[0017] Figure 1 This is a scanning electron microscope image of the sheet-like FeCoB microwave absorbing alloy powder material prepared in Example 1 of the present invention; Figure 2This is a scanning electron microscope image of the sheet-like FeCoB microwave absorbing alloy powder material prepared in Example 2; Figure 3 This is a scanning electron microscope image of the sheet-like FeCoB microwave absorbing alloy powder material prepared in Example 3; Figure 4 The reflection loss curve of the sheet-like FeCoB microwave absorbing alloy powder material prepared in Example 1 is shown. Figure 5 The graph shows the reflection loss curve of the sheet-like FeCoB microwave absorbing alloy powder material prepared in Example 2. Figure 6 The image shows the reflection loss curve of the sheet-like FeCoB microwave absorbing alloy powder material prepared in Example 3. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0019] The Fe, Co, and B blocks used in the embodiments of this invention have a purity ≥ 99.9 wt%.

[0020] Example 1 A sheet-like FeCoB alloy microwave absorbing material, with the chemical formula Fe... 48.5 Co 48.5 B3, the specific steps of its preparation method are as follows: 1) According to the chemical formula Fe 48.5 Co 48.5 To determine the atomic percentage of B3, weigh out Fe, Co, and B blocks and place them in an alumina crucible. Then, place the alumina crucible in the induction coil of a vacuum induction melting furnace and place a copper mold below the crucible. Close the furnace chamber and begin melting. First, evacuate the furnace chamber and then introduce high-purity argon gas with a purity of 99.999 vol%, repeating this process 2 to 3 times. After the last evacuation, introduce high-purity argon gas until the pressure inside the chamber reaches -0.05 MPa. Then, turn on the high-frequency current switch and gradually increase the current until the raw materials in the alumina crucible begin to melt. Once the raw materials are completely molten, continue to hold at 1500℃ for 25 minutes. After melting, obtain the FeCoB alloy ingot by casting. 2) The FeCoB alloy ingot obtained from smelting is mechanically crushed and passed through a 20-mesh sieve. The resulting FeCoB alloy particles are mixed with stainless steel balls and anhydrous ethanol at a mass ratio of 1:20:2 and then placed into a 500mL stainless steel ball mill jar. The mixture is ball-milled at 300r / min for 30h. The ball-milled product is then removed, dried, and passed through a 120-mesh sieve to obtain FeCoB alloy powder. The FeCoB alloy powder is then mixed with stainless steel balls and anhydrous ethanol at a mass ratio of 1:20:2 and placed into a stainless steel ball mill jar. The mixture is ball-milled at 300r / min for 30h. The ball-milled product is then removed, dried, and passed through a 180-mesh sieve to obtain sheet-like FeCoB alloy microwave absorbing material.

[0021] The SEM image of the sheet-like FeCoB alloy microwave absorbing material prepared in this embodiment is shown below. Figure 1 As shown, the product has a microstructure of plate-like particles with a particle size of 4-50 μm and a thickness of less than 1 μm.

[0022] The sheet-like FeCoB alloy absorbing material obtained in this embodiment was mixed with paraffin wax at a mass ratio of 7:3. A coaxial ring with an outer diameter of 7.0 mm, an inner diameter of 3.0 mm, and a thickness of 3.0 mm ± 0.3 mm was then formed. Its electromagnetic parameters were measured using a vector network analyzer. The measured electromagnetic parameters were then substituted into the reflection loss calculation formula to obtain the reflection loss curve of the sheet-like FeCoB alloy absorbing material prepared in this embodiment, as shown below. Figure 4 As shown, with a thickness of 2.6 mm, an absorption of -31.53 dB is achieved at 2.8 GHz, with a maximum effective absorption bandwidth of 1.43 GHz.

[0023] Example 2 A sheet-like FeCoB alloy microwave absorbing material, with the chemical formula Fe... 47.5 Co 47.5 B5, the specific steps of its preparation method are as follows: 1) According to the chemical formula Fe 47.5 Co 47.5 To determine the atomic percentage of B5, weigh out Fe, Co, and B blocks and place them in an alumina crucible. Then, place the alumina crucible in the induction coil of a vacuum induction melting furnace and place a copper mold below the crucible. Close the furnace chamber and begin melting. First, evacuate the furnace chamber and then introduce high-purity argon gas (99.999 vol%), repeating this process 2 to 3 times. After the last evacuation, introduce high-purity argon gas until the pressure inside the chamber reaches -0.05 MPa. Then, turn on the high-frequency current switch and gradually increase the current until the raw materials in the alumina crucible begin to melt. Once the raw materials are completely molten, continue holding at 1600℃ for 20 minutes. After melting, obtain the FeCoB alloy ingot by casting. 2) The FeCoB alloy ingot obtained from smelting is mechanically crushed and passed through a 20-mesh sieve. The resulting FeCoB alloy particles are mixed with stainless steel balls and anhydrous ethanol at a mass ratio of 1:15:3 and then placed into a 500mL stainless steel ball mill jar. The mixture is ball-milled at 350r / min for 25h. The ball-milled product is then removed, dried, and passed through a 120-mesh sieve to obtain FeCoB alloy powder. The FeCoB alloy powder is then mixed with stainless steel balls and anhydrous ethanol at a mass ratio of 1:15:3 and placed into a stainless steel ball mill jar. The mixture is ball-milled at 350r / min for 25h. The ball-milled product is then removed, dried, and passed through a 180-mesh sieve to obtain sheet-like FeCoB alloy microwave absorbing material.

[0024] The SEM image of the sheet-like FeCoB alloy microwave absorbing material prepared in this embodiment is shown below. Figure 2 As shown, the product has a microstructure of plate-like particles with a particle size of 5-34 μm and a thickness of less than 1 μm.

[0025] The sheet-like FeCoB alloy absorbing material obtained in this embodiment was mixed with paraffin wax at a mass ratio of 7:3. A coaxial ring with an outer diameter of 7.0 mm, an inner diameter of 3.0 mm, and a thickness of 3.0 mm ± 0.3 mm was then formed. Its electromagnetic parameters were measured using a vector network analyzer. The measured electromagnetic parameters were then substituted into the reflection loss calculation formula to obtain the reflection loss curve of the sheet-like FeCoB alloy absorbing material prepared in this embodiment, as shown below. Figure 5 As shown, with a thickness of 2.2 mm, an absorption of -39.23 dB is achieved at 4.4 GHz, with a maximum effective absorption bandwidth of 3.37 GHz.

[0026] Example 3 A sheet-like FeCoB alloy microwave absorbing material, with the chemical formula Fe... 46.5 Co 46.5 B7, the specific steps of its preparation method are as follows: 1) According to the chemical formula Fe 46.5 Co 46.5 To determine the atomic percentage of B7, weigh out Fe, Co, and B blocks and place them in an alumina crucible. Then, place the alumina crucible in the induction coil of a vacuum induction melting furnace and place a copper mold below the crucible. Close the furnace chamber and begin melting. First, evacuate the furnace chamber and then introduce high-purity argon gas with a purity of 99.999 vol%, repeating this process 2 to 3 times. After the last evacuation, introduce high-purity argon gas until the pressure inside the chamber reaches -0.05 MPa. Then, turn on the high-frequency current switch and gradually increase the current until the raw materials in the alumina crucible begin to melt. Once the raw materials are completely molten, continue to hold at 1700℃ for 15 minutes. After melting, obtain the FeCoB alloy ingot by casting. 2) The FeCoB alloy ingot obtained from smelting is mechanically crushed and passed through a 20-mesh sieve. The resulting FeCoB alloy particles are mixed with stainless steel balls and anhydrous ethanol at a mass ratio of 1:10:4 and then placed into a 500mL stainless steel ball mill jar. The mixture is ball-milled at 400r / min for 20h. The ball-milled product is then removed, dried, and passed through a 120-mesh sieve to obtain FeCoB alloy powder. The FeCoB alloy powder is then mixed with stainless steel balls and anhydrous ethanol at a mass ratio of 1:10:4 and placed into a stainless steel ball mill jar. The mixture is ball-milled at 400r / min for 20h. The ball-milled product is then removed, dried, and passed through a 180-mesh sieve to obtain sheet-like FeCoB alloy microwave absorbing material.

[0027] The SEM image of the sheet-like FeCoB alloy microwave absorbing material prepared in this embodiment is shown below. Figure 3 As shown, the product has a microstructure of sheet-like particles with a particle size of 3~31μm and a thickness of less than 1μm.

[0028] The sheet-like FeCoB alloy absorbing material obtained in this embodiment was mixed with paraffin at a mass ratio of 7:3 to form a coaxial ring with an outer diameter of 7.0 mm, an inner diameter of 3.0 mm, and a thickness of 3.0 ± 0.3 mm. Its electromagnetic parameters were measured using a vector network analyzer, and the measured electromagnetic parameters were then substituted into the reflection loss calculation formula to obtain the reflection loss curve of the sheet-like FeCoB alloy absorbing material prepared in this embodiment, as shown below. Figure 6 As shown, with a thickness of 2.0 mm, an absorption of -42.76 dB is achieved at 5.36 GHz, with a maximum effective absorption bandwidth of 3.73 GHz.

[0029] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A sheet-like FeCoB alloy microwave absorbing material, characterized in that, The sheet-like FeCoB alloy microwave absorbing material has a molar percentage content of 30-69% for Fe, 30-69% for Co, and 1-10% for B, with the sum of all elements being 100%. Its microstructure consists of sheet-like particles with a particle size of 3-50 μm and a thickness of less than 1 μm.

2. The sheet-like FeCoB alloy microwave absorbing material according to claim 1, characterized in that, The sheet-like FeCoB alloy microwave absorbing material, with a thickness of 1.0~4.0 mm, achieves an absorption performance of -10.84~-42.76 dB in the 2~8 GHz frequency band.

3. The sheet-like FeCoB alloy microwave absorbing material according to claim 2, characterized in that, The chemical formula of the sheet-like FeCoB alloy microwave absorbing material is Fe. 48.5 Co 48.5 At B3, an absorption of -31.53 dB is achieved at 2.8 GHz with a thickness of 2.6 mm, and the maximum effective absorption bandwidth is 1.43 GHz; the chemical formula of the sheet-like FeCoB alloy microwave absorbing material is Fe 47.5 Co 47.5 At B5, with a thickness of 2.2 mm, an absorption of -39.23 dB is achieved at 4.4 GHz, with a maximum effective absorption bandwidth of 3.37 GHz; the chemical formula of the sheet-like FeCoB alloy microwave absorbing material is Fe 46.5 Co 46.5 At B7, an absorption of -42.76 dB is achieved at 5.36 GHz with a thickness of 2.0 mm, and the maximum effective absorption bandwidth is 3.73 GHz.

4. A method for preparing the sheet-like FeCoB alloy microwave absorbing material according to any one of claims 1-3, characterized in that, The specific steps are as follows: 1) Weigh out Fe blocks, Co blocks, and B blocks according to the specified proportions and set aside; 2) The Fe block, Co block and B block weighed in step 1) are subjected to induction melting, and FeCoB alloy ingots are obtained by casting. 3) After mechanically crushing the FeCoB alloy ingot obtained in step 2), the FeCoB alloy powder is obtained by ball milling. The FeCoB alloy powder is then ball milled a second time to obtain sheet-like FeCoB alloy microwave absorbing material.

5. The method for preparing the sheet-like FeCoB alloy microwave absorbing material according to claim 4, characterized in that, Step 1) The purity of the Fe block, Co block and B block is ≥99.9wt%.

6. The method for preparing the sheet-like FeCoB alloy microwave absorbing material according to claim 4, characterized in that, Step 2) The induction melting conditions are as follows: using high-purity argon gas with a purity of 99.999 vol% as the protective atmosphere, the gas pressure is -0.1 to -0.05 MPa, the melting temperature is 1500 to 1700℃, and the melting time is 10 to 30 min.

7. The method for preparing the sheet-like FeCoB alloy microwave absorbing material according to claim 4, characterized in that, Step 3) The ball milling process conditions are as follows: stainless steel balls are used as the ball milling medium, anhydrous ethanol is used as the process control agent, the ball-to-material ratio is 10:1~20:1, the mass ratio of FeCoB alloy ingot to anhydrous ethanol is 1:1~1:4, the ball milling speed is 200~400 r / min, and the ball milling time is 10~30 h.

8. The method for preparing the sheet-like FeCoB alloy microwave absorbing material according to claim 4, characterized in that, Step 3) The secondary ball milling process conditions are as follows: stainless steel balls are used as the ball milling medium, anhydrous ethanol is used as the process control agent, the ball-to-material ratio is 10:1~20:1, the mass ratio of FeCoB alloy powder to anhydrous ethanol is 1:1~1:4, the ball milling speed is 200~400 r / min, and the ball milling time is 10~30 h.

9. The application of the sheet-like FeCoB alloy microwave absorbing material according to any one of claims 1-3 in the field of stealth materials.

10. The application of the sheet-like FeCoB alloy microwave absorbing material according to any one of claims 1-3 in the field of communication or information security.

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