FSA / ZnO (at) YCo composite wave-absorbing material and preparation method thereof

Abstract

The invention discloses an FSA / ZnO (at) YCo composite wave-absorbing material and a preparation method thereof. The FSA / ZnO (at) YCo composite wave-absorbing material comprises an iron-silicon-aluminum alloy and a needle-column-shaped ZnO coating layer modified YCo alloy, the needle-column-shaped ZnO coating layer modified YCo alloy is of a core-shell structure, the core-shell structure comprises a needle-column-shaped ZnO coating layer and an internal YCo alloy, and a heterogeneous interface is arranged between the needle-column-shaped ZnO coating layer and the internal YCo alloy. By utilizing the synergistic effect between a soft magnetic alloy system FeSiAl and a YCo alloy matrix with high saturation magnetization intensity and integrating multiple loss mechanisms such as magnetic loss, dielectric loss, interface polarization and structure scattering, efficient dissipation of electromagnetic wave energy is realized, and the adaptability and stability of the composite material to a complex electromagnetic environment are also enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of electromagnetic shielding and relates to an FSA / ZnO@YCo composite absorbing material and a preparation method thereof. Background Art

[0002] With the increasing problem of electromagnetic pollution, the development of high-efficiency, lightweight, and broadband absorbing materials has become a research hotspot in materials science.

[0003] Rare earth metal and transition metal alloys (such as YCo alloy) and soft magnetic alloys (such as FeAlSi alloy) have attracted significant attention in microwave absorbing material research due to their unique magnetic and electrical conductivity properties. Rare earth elements have a rich electronic structure, while transition metals can modulate the alloy's electrical conductivity and crystal structure. The magnetic properties of YCo alloys interact with the magnetic field component of electromagnetic waves, and their electrical conductivity influences internal charge distribution and electromagnetic induction, thus impacting microwave absorption. In FeAlSi alloys, iron possesses excellent magnetic properties, while aluminum and silicon modify the crystal structure and magnetic properties. This alloy effectively concentrates and guides magnetic fields, enhancing microwave absorption.

[0004] However, whether it is a rare earth metal and transition metal alloy or a soft magnetic alloy, it is difficult for a single alloy to achieve both low-frequency and high-frequency absorption performance. This is because the interaction mechanisms between low-frequency and high-frequency electromagnetic waves and materials are different. At low frequencies, the electromagnetic wavelength is longer, and absorption is more dependent on material properties such as magnetic permeability and hysteresis loss; at high frequencies, the wavelength is shorter, and the dielectric constant, conductivity, and skin effect of the material have a more significant impact on absorption performance. The electromagnetic parameters of a single alloy are difficult to meet the optimal electromagnetic matching characteristics at both low and high frequencies, resulting in suboptimal absorption performance across the entire frequency band. Therefore, it is necessary to further optimize the electromagnetic matching characteristics of the absorbing material to improve the absorption performance so that it can perform stably in different environments. Summary of the Invention

[0005] To address the challenges of existing absorbing materials, such as difficulty balancing low- and high-frequency requirements and poor stability, the first objective of the present invention is to provide an FSA / ZnO@YCo composite absorbing material. This material, while modifying the YCo alloy through needle-coated ZnO, utilizes the unique morphology of the heterojunction interface to regulate the dielectric constant and permeability of the material, improving the composite's impedance matching and electromagnetic wave attenuation performance. Furthermore, the synergistic effect between the FeSiAl soft magnetic alloy system (with a high saturation magnetization) and the YCo alloy matrix further reduces magnetic losses, enhancing the composite's electromagnetic matching and broadband absorption performance.

[0006] A second objective of the present invention is to provide a method for preparing an FSA / ZnO@YCo composite absorber. This method forms a needle-shaped coating layer by controlling the heat treatment process, effectively suppressing the agglomeration of the coating layer and improving the microstructural stability of the material. At the same time, high-energy ball milling is used to achieve uniform mixing of the two alloy matrices. This method has the advantages of simple process and readily available raw materials.

[0007] In order to achieve the above technical objectives, the present invention provides an FSA / ZnO@YCo composite absorbing material, which includes a sendustine alloy (FSA) and a YCo alloy modified with a needle-shaped ZnO coating layer; the YCo alloy modified with the needle-shaped ZnO coating layer has a core-shell structure, which includes a needle-shaped ZnO coating layer and an internal YCo alloy, and a heterogeneous interface between the needle-shaped ZnO coating layer and the internal YCo alloy.

[0008] The key innovations of the composite absorbing material of the present invention lie, on the one hand, in the special morphological design of the ZnO coating of the YCo alloy, and on the other hand, in the dielectric-magnetic synergistic loss effect formed by the two substrates. Specifically, the needle-columnar ZnO coating has a high aspect ratio and spatial orientation, which can induce multiple scattering, diffraction, and reflection during electromagnetic wave propagation, significantly extending the propagation path and residence time of the electromagnetic wave in the material, effectively improving the dissipation efficiency of electromagnetic energy. This needle-columnar morphology effectively suppresses the agglomeration of the coating and improves the stability of the material. At the same time, the significant difference in electrical conductivity and dielectric constant between the needle-columnar ZnO coating and the internal YCo alloy is utilized to produce interface polarization and interface charge accumulation effects, thereby enhancing the dielectric loss capacity of the material. At the same time, the high permeability and low coercivity of the soft magnetic FeSiAl alloy further contribute to the reduction of magnetic losses, particularly in the low-frequency range (2-6 GHz), providing good magnetic response. Hysteresis and eddy current losses: Its flaky structure generates hysteresis and eddy current losses in alternating electromagnetic fields, enhancing magnetic energy dissipation. Good electromagnetic impedance matching: Its moderate electrical and magnetic conductivity adjust the impedance matching of the entire composite system, reducing electromagnetic wave reflection and improving absorption efficiency. More importantly, the heterojunction formed by the ZnO coating and the FeSiAl flaky structure creates more microinterfaces and microelectric dipoles, producing more significant polarization hysteresis at low frequencies, thereby enhancing absorption losses.

[0009] As a preferred solution, the iron-silicon-aluminum alloy in the composite absorbing material includes Al 0.5 Fe3Si 0.5 , and their atomic percentage contents are: Fe 75 at.%, Si 12.5 at.%, Al 12.5 at.%; the YCo alloy includes Y2Co 17The two alloy systems selected in the present invention can significantly improve the material's microwave absorption performance in the low-frequency range of 2 to 6 GHz.

[0010] As a preferred solution, the mass ratio of the FeSiAl alloy to the YCo alloy modified with a needle-shaped ZnO coating is (1-6):(1-4). This mass ratio range of the present invention achieves optimal synergy between the magnetic and dielectric loss mechanisms of the two components, resulting in a composite system with enhanced microwave absorption performance in the low-frequency range of 2-6 GHz. Experimental results show that when the mass ratio of FeSiAl to ZnO@YCo is further reduced to 1:1, the material's complex dielectric constant and complex magnetic permeability reach an optimal balance, the reflection loss peak intensity is significantly enhanced, and the effective absorption bandwidth is expanded, demonstrating that this ratio has good electromagnetic parameter matching and practicality.

[0011] As a preferred solution, the thickness ratio of the needle-shaped ZnO coating layer to the YCo alloy is (0.004~0.02):1.

[0012] As a preferred embodiment, the absorbing material of the present invention exhibits dual-frequency absorption peaks within the 2-18 GHz frequency band, with reflection loss values ranging from -7.5 to -16.5 dB within the 4-6 GHz band and -9.0 to -24.8 dB within the 15-17 GHz band. This absorbing material exhibits excellent absorption capabilities for both low- and high-frequency electromagnetic waves, significantly expanding its application range and environmental adaptability. For example, it can be used as an absorbing and shielding material in the electromagnetic shielding field for consumer electronic devices and precision instrument housings or linings; in the stealth technology field for stealth coatings in aerospace, ships, and military vehicles; and in microwave communications for radomes, electromagnetic interference shielding enclosures, and other equipment.

[0013] The present invention also provides a method for preparing an FSA / ZnO@YCo composite absorbing material, which comprises dispersing YCo alloy powder in a zinc-containing solution, adding alkaline solution to form zinc hydroxide on the surface of the YCo alloy, and obtaining a precursor; heat-treating the precursor to obtain a YCo alloy modified with a needle-shaped ZnO coating layer; and mixing the YCo alloy modified with the needle-shaped ZnO coating layer with iron-aluminum-silicon alloy powder and then subjecting the mixture to high-energy ball milling to obtain the material.

[0014] The present invention first uses a heterogeneous precipitation method to in situ generate a precursor coating layer with regular morphology - zinc hydroxide on the surface of YCo alloy powder, and then realizes the transformation of the zinc hydroxide coating layer into a ZnO coating layer through heat treatment. At the same time, the temperature of the heat treatment is controlled to form the ZnO coating layer into a needle-column shape, thereby not only improving the interface uniformity and coating integrity of the coating layer and the YCo alloy, but also effectively suppressing the agglomeration of the coating layer through this special morphology, improving the stability of the material, and synergizing with the YCo alloy to enable it to exhibit dual-frequency absorption characteristics with high and low frequencies.

[0015] As a preferred solution, the amount of alkali solution added is controlled to achieve a slightly supersaturated state in the solution system, allowing heterogeneous nucleation of zinc hydroxide to form on the surface of the YCo alloy, and then the reaction is continued with stirring for at least 8 hours. This method of first forming heterogeneous nucleation of zinc hydroxide followed by continued stirring shortens the nucleation reaction time while ensuring uniformity of the coating layer.

[0016] As a preferred solution, after the reaction is completed, the obtained product needs to be separated into solid and liquid, washed and dried. Further preferably, the present invention uses water and anhydrous ethanol for washing, which is conducive to removing particle agglomerates caused by hydrogen bonds.

[0017] As a preferred embodiment, the heat treatment conditions are: a temperature of 280-300°C for 1-1.5 hours. The heat treatment temperature of the present invention has a direct impact on the morphology of the ZnO coating layer and the uniformity of the material. Within the heat treatment range selected by the present invention, the formed ZnO coating layer exhibits a structurally complete needle-columnar morphology, uniform coating, and minimal agglomeration, which is conducive to the formation of a stable heterogeneous interface structure. More preferably, the heat treatment temperature is 290-300°C.

[0018] As a preferred embodiment, the solid-to-liquid ratio of the YCo alloy powder to the zinc-containing solution is (30-40) g:200 ml, the concentration of the zinc-containing solution is 0.75-1.5 M, and the concentration of the alkali solution is 1-1.5 M. In the present invention, controlling the solid-to-liquid ratio of the YCo alloy powder to the zinc-containing solution effectively controls the thickness of the coating layer, thereby regulating the performance of the absorbing material.

[0019] As a preferred solution, the high-energy ball milling conditions are: a rotation speed of 600-1000 rpm, a time of 2-4 hours, and a ball-to-material ratio of (1-2):(1-2). Adjusting the high-energy ball milling parameters can effectively improve the interface structure and particle size distribution of the FSA / ZnO@YCo composite powder.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention combines needle-shaped ZnO coating modification with YCo and FeAlSi alloy. Through the synergistic effect of the two alloys, the electromagnetic matching characteristics of the material are optimized. Compared with the YCo composite material modified by single FSA / YCo physical blend or needle-shaped ZnO coating modification, the dielectric-magnetic synergistic loss effect is enhanced, multi-scale structural regulation is achieved, interface polarization and multiple scattering effects are achieved, and impedance matching is optimized.

[0022] (2) Compared with the needle-shaped ZnO-coated modified YCo material, the composite absorbing material of the present invention has a dual-frequency absorption peak in the 2~18GHz frequency band and exhibits better absorbing performance at the same thickness, especially forming an effective absorption range in the low frequency band of 4~6GHz, with a minimum RL value of -16.5dB, while maintaining strong absorption capacity in the medium and high frequency bands.

[0023] (3) The composite material system of the present invention achieves efficient dissipation of electromagnetic wave energy by integrating multiple loss mechanisms, including magnetic loss (YCo and FSA), dielectric loss (ZnO coating), interface polarization (multi-heterogeneous structure), and structural scattering (needle-column morphology). This rich loss mechanism not only improves the overall absorption strength but also enhances the adaptability and stability of the composite material in complex electromagnetic environments.

[0024] (4) The needle-shaped ZnO coating layer of the present invention has a high aspect ratio and spatial orientation, which can induce multiple scattering, diffraction and reflection during the propagation of electromagnetic waves, significantly prolonging the propagation path and residence time of electromagnetic waves in the material, effectively improving the dissipation efficiency of electromagnetic energy, and the heterostructure interface formed between the ZnO coating layer and the YCo alloy can introduce interface polarization and interface charge accumulation effects, thereby regulating the dielectric constant and magnetic permeability of the material to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 These are the XRD patterns of the YCo powder and FeSiAl powder used in the present invention.

[0026] Figure 2 SEM images of different powder samples at different magnifications, among which, Figure 2 (a) and Figure 2 (b) YCo; Figure 2 (c) and Figure 2 (d) FeSiAl; Figure 2 (e) and Figure 2 (f) is ZnO@YCo.

[0027] Figure 3 is the energy spectrum of different powder samples, where Figure 3 (a) ~ Figure 3 (c) YCo; Figure 3(d) ~ Figure 3 (g) FeSiAl; Figure 3 (h)~ Figure 3 (l) is ZnO@YCo.

[0028] Figure 4 High-resolution XPS spectrum of ZnO@YCo.

[0029] Figure 5 The electromagnetic parameters and loss tangent values of YCo powder, FSA / YCo powder, ZnO@YCo powder and FSA / ZnO@YCo powder prepared in Example 1 are shown in FIG. Figure 5 (a) is ε′, Figure 5 (b) is ε″, Figure 5 (c) is tanδE, Figure 5 (d) is μ′, Figure 5 (e) is μ″, Figure 5 (f) is tanδM.

[0030] Figure 6 The reflection loss diagram of different powder samples under different thickness of the absorbing material coating formed is shown in Figure 2. Figure 6 (a) is YCo, Figure 6 (b) is FeSiAl / YCo, Figure 6 (c) is ZnO@YCo, Figure 6 (d) FeSiAl / ZnO@YCo prepared in Example 1. DETAILED DESCRIPTION

[0031] The following further illustrates the technical solution of the present invention in conjunction with specific examples. However, it should be noted that the scope of protection of the present invention is not limited to the enumerated embodiments. It should be noted that the embodiments shown here are for illustrative purposes only. Other embodiments that can be derived by those skilled in the art based on the core technical solution of the present invention without creative work are all within the scope of protection of the claims of this patent.

[0032] Unless otherwise specified, all raw materials, reagents, instruments and equipment involved in the present invention can be obtained through commercial channels or prepared using existing methods.

[0033] The main components of the YCo alloy and FeSiAl powder used in the examples and comparative examples of the present invention are Y2Co 17 and Al 0.5 Fe3Si 0.5 , XRD test results are shown in Figure 1 .

[0034] Example 1

[0035] A method for preparing an FSA / ZnO@YCo composite absorbing material comprises the following steps:

[0036] First, dissolve 102.24 g of zinc chloride solid in a small amount of water and stir until completely dissolved. Then transfer the solution to a 1 L volumetric flask and dilute to 1 L with deionized water to obtain a 0.75 mol / L ZnCl2 solution.

[0037] 40 g of YCo alloy powder was then dispersed in 200 mL of the aforementioned ZnCl₂ solution and ultrasonically treated for 5 minutes to form a YCo-ZnCl₂ mixed solution. While stirring the solution with a glass rod, 1.5 M NaOH solution was slowly added until the solution became slightly supersaturated. This promoted the deposition of the generated Zn(OH)₂ on the YCo alloy powder, forming heterogeneous nuclei. The beaker containing the YCo-Zn(OH)₂ solution was then stirred in a stirrer at 800 rpm for 8 hours to ensure sufficient reaction and complete coating. After stirring, the powder was separated from the mother liquor by filtration and then washed repeatedly with deionized water and anhydrous ethanol three times to remove particle agglomerates caused by hydrogen bonding. During this process, a centrifuge was used to accelerate the separation of the powder and liquid, shortening the drying time.

[0038] The washed and centrifuged composite powder was dried in a drying oven at 60°C for 24 hours, then calcined in a muffle furnace at 300°C for 1 hour and kept warm for 30 minutes to finally obtain a needle-shaped zinc oxide-coated modified YCo alloy absorber material (ZnO@YCo), wherein the grain diameter of ZnO was between 30 and 38 nm, the diameter of the YCo alloy powder was between 2 and 8 μm, and the thickness ratio of the needle-shaped ZnO coating layer to the YCo alloy was 0.02:1.

[0039] Finally, the needle-shaped zinc oxide-coated modified YCo alloy absorbing material (ZnO@YCo) was mixed with FeAlSi alloy in a mass ratio of 1:1 and then mixed using high-energy ball milling technology with a ball milling time of 2 h, a rotation speed of 600 rpm, and a ball-to-material ratio of 1:1.

[0040] Figure 2 (a) and Figure 2 (b) The microscopic morphology and size of the YCo alloy powder used in this example. The powder has an irregular shape, a diameter ranging from 2 to 8 µm, and is generally polyhedral. Figure 2 (c) and Figure 2 (d) Micromorphology and size of the FeAlSi alloy used in this example. The FeSiAl particles are flaky with a smooth surface, and the powder diameter is in the range of 11–17 µm. Figure 2 (e) and Figure 2(f) shows the microstructure and size of the ZnO@YCo alloy prepared in this example. The surface of the YCo powder is evenly coated with needle-shaped zinc oxide. In addition, the energy spectrum ( Figure 3 (i) ~ Figure 3 The presence of the ZnO coating layer was also confirmed in (l). In addition, XPS was used to determine the presence of Y and Co elements in the ZnO@YCo powder.

[0041] Depend on Figure 4 It can be seen that there is a Zn 2p at 1021.9eV in the high-resolution Zn 2p 3 / 2 The peak corresponds to the Zn-O bond in stoichiometric ZnO, which further confirms that the surface of the YCo alloy is coated with zinc oxide.

[0042] The complex dielectric constant, complex magnetic permeability and simulated reflection loss (RL) performance of YCo alloy, ZnO@YCo, FSA / ZnO@YCo prepared in this embodiment and FSA / YCo prepared in comparative example 1 were tested in the range of 2~18 GHz. The results are as follows: Figure 5 and Figure 6 The results show that: (1) FSA / ZnO@YCo composite material has a double absorption peak, its real part of magnetic permeability decreases, and its imaginary part of magnetic permeability increases by more than 50% ( Figure 5 ); (2) At 4~6GHz, the reflection loss value of FSA / ZnO@YCo composite material can reach as low as -16.5dB, which significantly improves the low-frequency absorption performance; in the high-frequency range, above 15GHz, the reflection loss value of the composite material can reach as low as -24.8dB ( Figure 6 (d)); (3) The absorption range of FSA / ZnO@YCo (RL ≤ -10 dB) covers two bands: 4~6 GHz and 15~17 GHz; (4) Compared with YCo alloy, ZnO@YCo and FSA / YCo, FSA / ZnO@YCo has obvious advantages in absorption performance.

[0043] Example 2

[0044] The only difference between this embodiment and embodiment 1 is that the needle-shaped zinc oxide-coated modified YCo alloy absorbing material (ZnO@YCo) and the FeAlSi alloy are mixed in a mass ratio of 6:4, and then mixed using high-energy ball milling technology. The ball milling time is 2 hours, the rotation speed is 600 rpm, and the ball-to-material ratio is 1:1. The remaining steps and conditions are the same, thereby obtaining a needle-shaped zinc oxide-coated modified YCo alloy absorbing material (ZnO@YCo).

[0045] At 4-6 GHz, the reflection loss value of the FSA / ZnO@YCo composite material of this embodiment can reach as low as -8.2 dB, and its low-frequency absorption performance is inferior to that of Example 1. In the high-frequency range, above 15 GHz, the reflection loss value of the composite material reaches as low as -41.6 dB.

[0046] Example 3

[0047] The only difference between this embodiment and embodiment 1 is that the amount of YCo alloy powder is changed to 30 g, and the heat treatment temperature is changed to 300 ° C and the time is changed to 1.5 h. The remaining steps and conditions are the same, and a needle-shaped zinc oxide-coated modified YCo alloy absorbing material (ZnO@YCo) is obtained.

[0048] At 4-6 GHz, the reflection loss value of the FSA / ZnO@YCo composite material of this embodiment can reach as low as -7.5 dB, significantly improving the low-frequency absorption performance; in the high-frequency range, above 15 GHz, the reflection loss value of the composite material can reach as low as -32.6 dB.

[0049] Comparative Example 1

[0050] The only difference between this comparative example and Example 1 is that the YCo alloy powder is not coated and modified. Equal amounts of the uncoated and modified YCo alloy powder and the FeAlSi alloy are ball milled according to the ball milling conditions of Example 1 to obtain FSA / YCo.

[0051] The test results show that the RL value of the material is -8.6 dB at 4.3 GHz and -16.4 dB at 14.4 GHz.

[0052] Comparative Example 2

[0053] This comparative example differs from Example 1 in that the heat treatment temperature is 400°C; the remaining steps and conditions are identical. Test results show that the material exhibits a return loss range of -5.4 to -9.4 dB in the 4-6 GHz frequency band. The RL value at 15.92 GHz is -48.8 dB. Furthermore, as the temperature increases, the coated ZnO needle-like structure gradually disappears, affecting the absorption performance at low frequencies.

[0054] Comparative Example 3

[0055] This comparative example differs from Example 2 only in that the mass ratio of FeAlSi alloy to ZnO@YCo powder is changed from 6:4 to 7:3; all other steps and conditions remain the same. Test results show that the material exhibits a return loss range of -5.6 to -7.2 dB in the 4–6 GHz frequency band. The RL value at 16.72 GHz is -29.6 dB.

Claims

1. An FSA / ZnO@YCo composite absorbing material, characterized by: YCo alloy including Sendust alloy and needle-shaped ZnO coating modified; The YCo alloy modified by the needle-columnar ZnO coating layer has a core-shell structure. The core-shell structure includes the needle-columnar ZnO coating layer and the YCo alloy inside. A heterogeneous interface is formed between the needle-columnar ZnO coating layer and the YCo alloy inside.

2. The FSA / ZnO@YCo composite absorbing material according to claim 1, characterized in that: The Sendust alloy includes Al 0.5 Fe3Si 0.5 ; The YCo alloy includes Y2Co 17 alloy.

3. The FSA / ZnO@YCo composite absorbing material according to claim 1 or 2, characterized in that: The mass ratio of the Sendust alloy and the YCo alloy modified by the needle-shaped ZnO coating layer is (1-6): (1-4).

4. The FSA / ZnO@YCo composite absorbing material according to claim 3, characterized in that: The thickness ratio of the needle-shaped ZnO coating layer to the YCo alloy is (0.004-0.02):

1.

5. The method for preparing the FSA / ZnO@YCo composite absorbing material according to any one of claims 1 to 4, characterized in that: After dispersing YCo alloy powder in a zinc-containing solution, an alkali solution is added to form zinc hydroxide on the surface of the YCo alloy to obtain a precursor; after heat treatment of the precursor, a YCo alloy modified with a needle-shaped ZnO coating layer is obtained; The needle-shaped ZnO coating layer-modified YCo alloy is mixed with iron-aluminum-silicon alloy powder and then subjected to high-energy ball milling to obtain the alloy.

6. The method for preparing the FSA / ZnO@YCo composite absorbing material according to claim 5, characterized in that: The amount of alkali solution added is to control the alkali solution to be slightly supersaturated in the solution system, to form heterogeneous nucleation of zinc hydroxide on the surface of the YCo alloy, and then continue to stir and react for at least 8 hours.

7. The method for preparing the FSA / ZnO@YCo composite absorbing material according to claim 6, characterized in that: The heat treatment conditions are: temperature of 280-300° C. and time of 1-1.5 h.

8. The method for preparing the FSA / ZnO@YCo composite absorbing material according to claim 5, characterized in that: The solid-liquid ratio of the YCo alloy powder and the zinc-containing solution is (30-40) g:200 ml, the concentration of the zinc-containing solution is 0.75-1.5 M, and the concentration of the alkali solution is 1-1.5 M.

9. The method for preparing a FSA / ZnO@YCo composite absorbing material according to claim 7 or 8, characterized in that: The conditions of the high-energy ball milling are: a rotation speed of 600-1000 rpm, a time of 2-4 hours, and a ball-to-material ratio of (1-2): (1-2).

Images