FeCoNi-based high-entropy alloy electromagnetic wave absorbent and preparation method thereof

Abstract

The invention relates to the technical field of preparation of electromagnetic wave absorbents, in particular to a FeCoNi-based high-entropy alloy electromagnetic wave absorbent and a preparation method thereof.The electromagnetic wave absorbent is a FexCoyNizSiuTivCrw flaky powder mixture, x is 1 mol, y is 1 mol, z is 1 mol, x is 1 mol, y is 1 mol, and z is 1 mol. In the electromagnetic wave absorbent of the sheet-like powder, the particle size of the sheet-like powder is 1t; the particle size is 40 microns, the length-diameter ratio is greater than 20, and the crystal structure of the flaky powder particle is a body-centered cubic phase or a face-centered cubic phase; in the electromagnetic wave absorbent of the sheet-like powder, the real part of the dielectric constant is lt; 20, imaginary part lt; 6, a magnetic conductivity real part gt; 2.5, an imaginary part gt; 0.6, and the resonance frequency of the absorption peak value is 0.6 GHz-3 GHz. The method has the beneficial effects that the proportion and distribution of the BCC phase and the FCC phase are well controlled, so that the peak value of the magnetic conductivity of the electromagnetic wave absorbent can be adjusted, and the use requirement of a specific frequency band is met; in addition, the preparation process is simple.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic wave absorber preparation, in particular to an FeCoNi-based high entropy alloy electromagnetic wave absorber and a preparation method thereof. Background Art

[0002] Fifth-generation (5G) networks and wireless communication technologies are rapidly developing. The electromagnetic waves generated by these technologies pose potential hazards to human health and can interfere with the normal operation of electronic devices. Long-term exposure to electromagnetic radiation can cause a range of symptoms, including vision loss, increased head temperature, elevated blood pressure, and difficulty concentrating. During normal operation, unwanted external electromagnetic radiation signals can interfere with the device, leading to serious malfunctions. Furthermore, electromagnetic radiation can pose a threat to information security, particularly by leaking sensitive information and posing serious privacy risks. Therefore, there is an urgent need for materials that can absorb and dissipate electromagnetic waves. Absorbing materials are materials that absorb incident electromagnetic waves and dissipate them as energy in other forms. In addition to excellent absorption capabilities, these materials must also possess a wide absorption bandwidth and be thin and lightweight.

[0003] High-entropy alloys (HEAs) are a special type of multi-element alloy composed of at least five or more primary elements, with no distinct primary or secondary elements. Their composition is highly uniform, with nearly equal mole fractions of all elements. Due to their unique composition and structure, HEAs possess a certain degree of corrosion resistance, offering broad potential for application in electromagnetic wave absorption. Currently, HEAs are being used as electromagnetic wave absorbers, primarily focusing on composition design, heat treatment, and lamination. These systems utilize ferromagnetic transition metals such as Fe, Co, and Ni, with the addition of Cr, Cu, and Al to adjust the effective valence electron concentration. Heat treatment is used to enhance absorption properties, and the aspect ratio of the powder can also be modified by element addition. The microstructure is primarily composed of two phases, BCC and FCC. This is currently achieved primarily through element doping and heat treatment, or by inducing a phase transition from a mixed face-centered cubic (FCC) and body-centered cubic (BCC) structure to a single BCC structure through the incorporation of metal elements. Heat treatment can also be used to induce the phase transition.

[0004] Traditional mechanical alloying methods usually mix multiple elements at once and directly form the target alloy through mechanical ball milling. This method has a relatively simple process, mature technology, and short preparation cycle. However, in this method, uneven diffusion between different elements and element segregation are relatively common, especially for elements with high melting points or low diffusion rates. In addition, the phase control ability is weak, and it is difficult to effectively avoid the formation of brittle phases and impurity phases, which limits the further optimization of material properties. Especially in the field of magnetic functional materials, traditional methods often lead to the weakening of ferromagnetic phases and limited magnetic loss performance.

[0005] To this end, the inventors adopted a new electromagnetic wave absorber and its preparation method. Not only is the preparation simple, but by controlling the preparation time, flaky powder of ideal size can be obtained. The ratio and distribution of the BBC phase (body-centered cubic phase) and FFC phase (face-centered cubic phase) can also be well controlled, thereby facilitating the adjustment of the peak magnetic permeability of the electromagnetic wave absorber - thereby meeting the requirements of use in specific frequency bands. Summary of the Invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an FeCoNi-based high-entropy alloy electromagnetic wave absorber and a preparation method thereof, which solves the technical problem that the weak phase control ability limits the further optimization of material properties, thereby leading to the weakening of ferromagnetism and the limitation of magnetic loss performance.

[0007] The purpose of the present invention is achieved through the following technical solutions: In the first aspect, a FeCoNi-based high entropy alloy electromagnetic wave absorber and a preparation method thereof are disclosed, wherein the electromagnetic wave absorber is Fe x Co y Ni z Si u Ti v Cr w A flake powder mixture, wherein x is 1 mol, y is 1 mol, z is 1 mol, u is 0.05 mol to 0.2 mol, v is 0.1 mol to 1 mol, and y is 0.1 mol to 0.5 mol; In the flaky powder electromagnetic wave absorber, the particle size of the flaky powder is less than 40 μm, the aspect ratio is greater than 20, and the crystal structure of the flaky powder particles includes a body-centered cubic phase and a face-centered cubic phase; In the flaky powder electromagnetic wave absorber, the real part of the dielectric constant is less than 20 and the imaginary part is less than 6, the real part of the magnetic permeability is greater than 2.5 and the imaginary part is greater than 0.6, and the resonance frequency of the absorption peak is 0.6 GHz to 3 GHz.

[0008] Furthermore, the materials of the electromagnetic wave absorber include: FeCo alloy powder, Ni single powder, Si, Ti and Cr auxiliary powders. Of course, FeNi can also be selected as alloy powder, Co as single powder, and Si, Ti and Cr as auxiliary powders as needed.

[0009] Furthermore, when preparing the electromagnetic wave absorber, the following steps are performed: first, it is determined whether the desired electromagnetic wave absorber has a body-centered cubic phase or a face-centered cubic phase crystal structure, which is referred to as the target phase crystal structure; then, alloy powder is selected as the first matrix raw material to be added; then, a crystalline material with the most similar crystal structure to the target phase is selected and added; and then the remaining powder is added for stabilization.

[0010] Furthermore, the material that is most similar to the target crystal structure can be a single powder or auxiliary powders of Si, Ti and Cr.

[0011] In a second aspect, a method for preparing a FeCoNi-based high entropy alloy electromagnetic wave absorber is also disclosed, and the preparation steps are as follows: S1. Prepare materials; Determine the crystal structure required for preparing the electromagnetic wave absorber and select the alloy powder that is most similar to the crystal structure of the electromagnetic wave absorber - FeCo / FeNi; then prepare the corresponding single powder - Ni / Co; prepare Si, Ti, and Cr powders; the particle size of each powder is less than 50μm; In the prepared powder, Fe is 1 mol, Co is 1 mol, Ni is 1 mol, Si is 0.05 mol~0.2 mol, Ti is 0.1 mol~1 mol, and Cr is 0.1 mol~0.5 mol; S2, using the sequential alloying method to grind the powder using stainless steel balls; Among them, there are two types of 304 stainless steel balls, φ10mm and φ6mm, and the number of φ10mm stainless steel balls is 1:2, and all powders and stainless steel balls are ground according to the material-ball ratio of 1:20; During grinding, first put the alloy powder into the ball mill and grind it, then put the single powder into the ball mill and grind it, and then add Si, Ti, and Cr powders in sequence and grind them. During the grinding process, 1g / ml of anhydrous ethanol needs to be added as a control agent, and the grinding is carried out at a certain speed, finally obtaining a flake powder with a particle size of <40μm. S3. After grinding, the flaky powder is dried.

[0012] Furthermore, in the above-mentioned S3, the ground powder is placed at 60° C. and dried to finally obtain flaky FeCoNi-based high entropy alloy powder.

[0013] Furthermore, in S2, the rotation speed during grinding is 350 r / min.

[0014] Furthermore, among the powders used, the element purity of the corresponding alloy powder, single powder, Si powder, Ti powder, and Cr powder is higher than 99.9%.

[0015] To facilitate understanding, the core principles of this solution are explained: In this proposal, a sequential alloying method is used to prepare electromagnetic wave absorbers. This method gradually introduces each component element in a specific order, allowing for full element diffusion and gradual optimization of the local composition at each step. It can also purposefully prioritize the formation of certain favorable phases (such as ferromagnetic phases) for fine-tuning. This process not only improves compositional uniformity but also promotes the formation of nanocrystalline, metastable, or non-equilibrium structures, significantly improving the material's magnetic and wave-absorbing properties. Furthermore, the sequential alloying method offers greater process flexibility, enabling the dynamic adjustment of formulations and processing parameters based on demand. The flexibility of compositional design is no longer limited to the elemental proportions of the material but can be extended to the crystal structure of the alloy powder.

[0016] The present invention has the following advantages: (1) In this scheme, it is only necessary to control the ratio of the order of element addition to well control the ratio and distribution of the BCC phase and the FCC phase, thereby adjusting the peak value of the magnetic permeability of the electromagnetic wave absorber and thus meeting the requirements of use in a specific frequency band; The present invention adopts stainless steel grinding balls and controls the ball milling time to obtain ideal flaky powder. (2) The FeCoNi-based high entropy alloy electromagnetic wave absorber of the present invention does not require special preparation equipment, but only requires traditional atomization powder making equipment, a ball mill, and a tubular annealing furnace. The preparation process is simple and easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 SEM image of FeCoNi-based high entropy alloy electromagnetic wave absorber; Figure 2 XRD relationship diagram of Examples 1 and 2 and the original sample; Figure 3 The relationship between the dielectric constant and frequency of Examples 1 and 2 and the original sample; Figure 4 Graph showing the relationship between magnetic permeability and frequency for Examples 1 and 2 and the original sample; Figure 5 Reflection loss diagram of Example 1; Figure 6 Reflection loss diagram of Example 2. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following description.

[0019] Example 1 This embodiment discloses a FeCoNi-based high entropy alloy electromagnetic wave absorber and a preparation method thereof, which comprises the following steps: S1. Determine alloy formula and sequence design: First, determine the molar ratio of the FeCoNi basic elements of the absorbent, and prepare Fe 50 Co 50 alloy powder, and then sequentially adding Si, Ti and Cr, and then adding Ni powder; wherein the molar ratio of Fe, Co and Cr is 1:1:1 (selecting 1 mole of Fe, Co and Cr), and the molar ratio of Si, Ti and Cr is 0.1:0.5:0.2 (selecting 0.1 mole of Si, 0.5 mole of Ti and 0.2 mole of Cr); and the particle size of the powder of each element is less than 50 μm; S2, using the sequential alloying method to grind the powder using stainless steel balls; The ball mill was equipped with two types of 304 stainless steel balls, φ10 mm and φ6 mm, with a large ball and small ball ratio of 1:2 (i.e. φ10 mm and φ6 mm). Anhydrous ethanol was added as a process control agent at 2 g / ml, and the rotation speed was 350 r / min. The powder-to-ball ratio is 1:20 and the powder is put into the grinder in the following order: (1) the target phase is determined to be the BBC crystal structure; (2) FeCo alloy powder is selected as the matrix, the alloy powder is put into the grinder, and then auxiliary powders (i.e. Si, Cr, Ti powders) with a crystal structure similar to the target phase are added together and mechanical alloying is carried out for 15 hours; (3) then a single element powder is added - i.e. Ni powder (as a stable phase) is added and mechanical alloying is carried out for 10 hours; (3) then dried at 60°C to obtain flaky FeCoNi-based high entropy alloy powder.

[0020] It should be noted that, in this embodiment, the order of the alloys is: (FeCo)→(Si, Cr, Ti)→Ni.

[0021] Example 2 This embodiment discloses a FeCoNi-based high entropy alloy electromagnetic wave absorber and a preparation method thereof, which comprises the following steps: S1. Determine alloy formula and sequence design: First, determine the molar ratio of the FeCoNi basic elements of the absorbent, and prepare Fe 50 Co 50 Alloy powder, to which Ni powder (1 mole of each of Fe, Co, and Cr) is added, followed by Si, Ti, and Cr powders, wherein the molar ratio of Fe, Co, and Cr is 1:1:1 (1 mole of Fe, Co, and Cr is selected), and the molar ratio of Si, Ti, and Cr is 0.1:0.5:0.2 (0.1 mole of Si, 0.5 mole of Ti, and 0.2 mole of Cr is selected), respectively; and the particle size of the powder of each element is less than 50 μm; S2, using the sequential alloying method to grind the powder using stainless steel balls; The ball mill was equipped with two types of 304 stainless steel balls, φ10 mm and φ6 mm, with a large ball and small ball ratio of 1:2 (i.e. φ10 mm and φ6 mm). Anhydrous ethanol was added as a process control agent at 2 g / ml, and the rotation speed was 350 r / min. The powder-to-ball ratio is 1:20 and is put into the grinding mill in the following order: (1) the target phase is determined to be the BBC crystal structure; (2) FeCo alloy powder is selected as the matrix, the alloy powder is put into the grinding mill, and then Ni powder with a crystal structure similar to the target phase is added and mechanical alloying is carried out for 10 hours; (3) auxiliary powders (i.e. Si, Ti and Cr powders, as stable phases) are then added and mechanical alloying is carried out for 15 hours; (3) and then dried at 60°C to obtain flaky FeCoNi-based high entropy alloy powder.

[0022] It should be noted that, in this embodiment, the order of the alloys is: (FeCo) → Ni → (Si, Cr, Ti).

[0023] Test Case It should be noted that performance tests were conducted on Example 1 and Example 2, and compared with the original samples.

[0024] Specifically: the FeCoNi-based high entropy alloy electromagnetic wave absorber obtained by the above-mentioned sequential alloying method was mixed with paraffin in a ratio of 4:1, pressed into a φ7mm×φ3mm×3mm ring sample, and the electromagnetic parameters of the absorber were measured.

[0025] The experimental results are as follows Figures 1 to 6 shown.

[0026] The above embodiments merely represent preferred implementations, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art will be able to make various modifications and improvements without departing from the scope of the present invention, and these modifications and improvements are all within the scope of protection of the present invention.

Claims

1. A FeCoNi-based high entropy alloy electromagnetic wave absorber, characterized in that: The electromagnetic wave absorber is Fe x Co y Ni z Si u Ti v Cr w A mixture of flake powders, wherein x is 1 mol, y is 1 mol, and z is 1 mol; In the flaky powder electromagnetic wave absorber, the particle size of the flaky powder is less than 40 μm, the aspect ratio is greater than 20, and the crystal structure of the flaky powder particles is a body-centered cubic phase or a face-centered cubic phase; In the flaky powder electromagnetic wave absorber, the real part of the dielectric constant is less than 20 and the imaginary part is less than 6, the real part of the magnetic permeability is greater than 2.5 and the imaginary part is greater than 0.6, and the resonance frequency of the absorption peak is 0.6 GHz to 3 GHz.

2. The FeCoNi-based high entropy alloy electromagnetic wave absorber according to claim 1, characterized in that: In the electromagnetic wave absorber, u is 0.1 mol, v is 0.5 mol, and w is 0.3 mol.

3. The FeCoNi-based high entropy alloy electromagnetic wave absorber according to claim 1, characterized in that: The materials of the electromagnetic wave absorber include: FeCo alloy powder, Ni single powder, Si, Ti and Cr auxiliary powders.

4. The FeCoNi-based high entropy alloy electromagnetic wave absorber according to claim 3, characterized in that: When preparing the electromagnetic wave absorber: First, determine whether the required electromagnetic wave absorber has a body-centered cubic phase or a face-centered cubic phase crystal structure - called the target phase crystal structure; then select alloy powder as the first matrix raw material to be added, and then select the crystal material most similar to the target phase crystal structure, and then add the remaining powder as the stable phase.

5. The FeCoNi-based high entropy alloy electromagnetic wave absorber according to claim 4, characterized in that: The substance that is most similar to the target crystal structure is a single powder, or auxiliary powders of Si, Ti and Cr.

6. A method for preparing a FeCoNi-based high entropy alloy electromagnetic wave absorber, characterized in that: Used for preparing the electromagnetic wave absorber according to any one of claims 1 to 4; The preparation steps are: S1. Prepare materials; Determine the crystal structure required for preparing the electromagnetic wave absorber and select the alloy powder that is most similar to the crystal structure of the electromagnetic wave absorber - FeCo / FeNi; then prepare the corresponding single powder - Ni / Co; prepare Si, Ti, and Cr powders; the particle size of each powder is less than 50μm; In the prepared powder, Fe is 1 mol, Co is 1 mol, Ni is 1 mol, Si is 0.05 mol~0.2 mol, Ti is 0.1 mol~1 mol, and Cr is 0.1 mol~0.5 mol; S2, using the sequential alloying method to grind the powder using stainless steel balls; Among them, there are two types of 304 stainless steel balls, φ10mm and φ6mm, and the number of φ10mm stainless steel balls is 1:2, and all powders and stainless steel balls are ground according to the material-ball ratio of 1:20; During grinding, the alloy powder is first put into the ball mill and ground, then the single powder is put in and ground, and then Si, Ti, and Cr powders are added in sequence and ground. During the grinding process, 1g / ml of anhydrous ethanol needs to be added as a control agent, and the grinding is carried out at a speed of 350r / min, and finally a flake powder with a particle size of <40μm is obtained. After grinding, the flaky powder is dried.

7. The FeCoNi-based high entropy alloy electromagnetic wave absorber and preparation method thereof according to claim 6, characterized in that: After the grinding is completed, the ground powder is placed at 60° C. and dried to finally obtain flaky FeCoNi-based high entropy alloy powder.

8. The FeCoNi-based high entropy alloy electromagnetic wave absorber and preparation method thereof according to claim 6, characterized in that: Among the powders used, the element purity of the corresponding alloy powder, single powder, Si powder, Ti powder, and Cr powder is higher than 99.9%.

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