Hexagonal sheet-shaped Fe3O4 (at) FeO (at) C (at) ZnIn2S4 core-shell structure wave-absorbing material as well as preparation and application thereof

Abstract

The invention relates to a hexagonal sheet-shaped Fe3O4 (at) FeO (at) C (at) ZnIn2S4 core-shell structure wave-absorbing material as well as preparation and application thereof, the hexagonal sheet Fe2O3 with the diameter of about 12 microns is taken as a template, and a double-layer core-shell structure with a magnetic core-PDA-derived carbon middle layer-semiconductor shell is constructed through surface coating polydopamine carbonization and in-situ growth of ZnIn2S4 nanosheets. Impedance matching is effectively improved through the hexagonal sheet structure, multiple loss mechanisms such as magnetic loss, interface polarization and dipole polarization are introduced into multiple heavy components, and the electromagnetic wave absorption performance of the material is cooperatively improved. The preparation method is simple, and the product is regular in morphology and excellent in performance and has wide application prospects in the technical fields of electromagnetic protection and stealth.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing materials technology, and relates to a hexagonal sheet-like Fe3O4@FeO@C@ZnIn2S4 core-shell structure microwave absorbing material, its preparation and application. Background Technology

[0002] With the rapid development of electronic information technology, electromagnetic pollution control is becoming increasingly urgent, highlighting the growing demand for high-performance electromagnetic wave absorbing materials. An ideal absorbing material needs both strong absorption and wide bandwidth characteristics, with its core performance lying in achieving good impedance matching and efficient electromagnetic energy dissipation. Magnetic metal oxides (such as Fe3O4) are classic candidates for absorbing materials due to their inherent magnetic loss characteristics. However, their single loss mechanism and intrinsic impedance mismatch severely limit their practical application performance. To address this issue, constructing core-shell structures to introduce dielectric loss components has become a mainstream strategy. By compositing a magnetic core with a dielectric shell (such as conductive polymer PDA, semiconductor ZnIn2S4, etc.), not only can magnetic / dielectric loss be synergistically managed, but interface polarization can also be induced by the heterojunction effect, enhancing the ability to absorb electromagnetic waves. Nevertheless, existing core-shell structure materials are mostly spherical, and their isotropy limits their ability to perform multiple reflections and scattering of electromagnetic waves.

[0003] For example, Chinese patent CN201910160166.2 provides a method for preparing and applying a core-shell structured Fe3O4@C@MoS2 composite material. The preparation method includes: S1: Adding FeCl3 and NaOH to water and mixing them evenly, then placing the mixed solution into a polytetrafluoroethylene stainless steel autoclave to react and obtain uniform cubic Fe2O3 particles; S2: Adding the Fe2O3 particles obtained in S1 and dopamine hydrochloride to a tris(hydroxymethyl)aminomethane buffer solution, and stirring with a magnetic stirrer at room temperature. The reaction was stirred, and the reaction product was washed and collected by centrifugation. S3: The Fe2O3@PDA obtained in S2 was added sequentially to water along with ammonium molybdate tetrahydrate and thiourea, and stirred until homogeneous. After the reaction, the product was washed and collected by centrifugation. S4: The Fe3O4@PDA@MoS2 composite was calcined under a hydrogen-argon gas flow to obtain the Fe3O4@C@MoS2 composite material. Analysis showed that the cubic Fe2O3 template used in this patent has potential for improved impedance matching due to its geometry; simultaneously, its single Fe3O4 magnetic core is somewhat lacking in the richness of magnetic loss mechanisms. Furthermore, the high intrinsic dielectric constant of the MoS2 shell easily leads to surface impedance mismatch, increasing the risk of electromagnetic wave reflection. In addition, the effectiveness of the cubic structure in promoting multiple electromagnetic wave reflections and constructing rich interfaces also needs further optimization. Summary of the Invention

[0004] The purpose of this invention is to provide a hexagonal sheet-like Fe3O4@FeO@C@ZnIn2S4 core-shell structure microwave absorbing material, its preparation and application. The hexagonal sheet structure effectively improves impedance matching, while the multiple components introduce various loss mechanisms such as magnetic loss, interface polarization, and dipole polarization, which synergistically enhance the electromagnetic wave absorption performance of the material.

[0005] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a hexagonal sheet-like Fe3O4@FeO@C@ZnIn2S4 core-shell structured microwave absorbing material, which is hexagonal sheet-like with Fe3O4@FeO as the magnetic core, polydopamine-derived carbon as the intermediate layer, and ZnIn2S4 semiconductor as the outer shell. Specifically, the microwave absorbing material uses hexagonal sheet-like Fe2O3 with a diameter of approximately 12 μm as the precursor template. From its core to its outer layer, the material consists of: a core: a magnetic Fe3O4@FeO hybrid core obtained by reducing the Fe2O3; an intermediate layer: an amorphous carbon layer formed by coating the core with PDA (polydopamine) and annealing, serving as a dielectric loss layer and a protective layer; and an outer shell layer: a ZnIn2S4 nanosheet layer coated on the carbon layer, serving as a dielectric loss and polarization loss layer. The combination of magnetic and dielectric materials, along with the advantages of the hexagonal plate-like core-shell structure, enhances the magnetic and dielectric loss capabilities of the composite material and strengthens the wave absorption capability of the hexagonal plate-like Fe3O4@FeO@C@ZnIn2S4 core-shell structure material.

[0006] In a second aspect, the present invention provides a method for preparing a hexagonal sheet-like Fe3O4@FeO@C@ZnIn2S4 core-shell structure microwave absorbing material, comprising the following steps: S1. Dissolve soluble iron salt in deionized water and stir to obtain solution A. Weigh hexadecyltrimethylammonium bromide (CTAB) and potassium hydroxide and dissolve them in deionized water to obtain solution B. Add solution A dropwise to solution B, stir, and then transfer to a reaction vessel for reaction. Wash and dry the resulting reaction product to obtain hexagonal plate-shaped Fe2O3 powder. S2. Disperse hexagonal plate-shaped Fe2O3 powder in Tris-HCl buffer solution to form a suspension, then add dopamine hydrochloride, stir the reaction, wash the product, dry it, and anneal it to obtain hexagonal plate-shaped Fe3O4@FeO@C powder. S3. Weigh out the zinc source, indium source and sulfur source and dissolve them in a mixed solution of water and glycerol. Then add the Fe3O4@FeO@C powder obtained in S2, disperse it by ultrasonication, and heat it to react to obtain Fe3O4@FeO@C@ZnIn2S4 powder, which is the target product.

[0007] Furthermore, in S1, the soluble iron salt is ferric chloride or its hydrate; The amounts of solution A and solution B added satisfy the following molar ratio: ferric chloride, hexadecyltrimethylammonium bromide, and potassium hydroxide is (14 ~ 16) mmol : (6.5 ~ 7.5) mmol : (0.8 ~ 0.9) mol. Preferably, it is 15 mmol : 6.8 mmol : 0.89 mol.

[0008] Furthermore, in S1, the reaction temperature is 220 ~ 250 ℃, preferably 240 ℃, and the time is 1 ~ 3 h, preferably 2 h.

[0009] Furthermore, in S2, the mass ratio of hexagonal plate-shaped Fe2O3 powder to dopamine hydrochloride is (0.8 ~ 1.2):(0.8 ~ 1.2), preferably 1:1. Additionally, optionally, the concentration of the Tris-HCl buffer solution is 10 mM, and the pH is 8.5.

[0010] Furthermore, in S2, the stirring reaction is carried out at room temperature for 12 to 36 hours. Annealing is carried out in a reducing atmosphere, preferably an H2 / Ar mixture. Optionally, the hydrogen component is 5%, the annealing temperature is 500-700 °C, and the time is 2-4 h. Furthermore, during annealing, the heating rate can be 4-6 °C / min, preferably 5 °C / min.

[0011] Furthermore, in S3, the amounts of zinc source, indium source, and sulfur source added satisfy the following condition: Zn 2+ In 3+ S 2- The molar ratio is 1:2:(4-8), with Zn being preferred. 2+ In 3+ :S 2- =1:2:4. Optionally, the zinc source is ZnCl2, the indium source is InCl3 or its hydrate, and the sulfur source is C2H5NS (thioacetamide).

[0012] Furthermore, in S3, the ratio of Fe3O4@FeO@C powder to zinc source is 0.1 g: (0.1 ~ 0.4) mmol.

[0013] Furthermore, in S3, the heating reaction is carried out at a temperature of 70 ~ 90 ℃ for a time of 1 ~ 3 h.

[0014] In a second aspect, the present invention provides an application of a hexagonal sheet-like Fe3O4@FeO@C@ZnIn2S4 core-shell structure absorbing material in the field of electromagnetic protection and stealth coating.

[0015] Compared with the prior art, the preparation process of this invention is simple, and the product obtained is a multilayer core-shell structure composite material with Fe3O4@FeO magnetic core-PDA-derived carbon intermediate layer-semiconductor ZnIn2S4 shell. Its dielectric constant can be effectively adjusted according to the amount of ZnIn2S4 added, and the synergistic effect of magnetic loss and dielectric loss of the composite material can be fully utilized to effectively improve impedance matching and electromagnetic wave absorption performance. Attached Figure Description

[0016] Figure 1 The images show SEM images of different intermediate products, where ac is the SEM image of Fe2O3; d is the SEM image of Fe2O3@PDA; and e is the SEM image of Fe3O4@FeO@C.

[0017] Figure 2 SEM images of the samples prepared in Examples 1 to 3, where ac are SEM images of the samples in Examples 1, 2, and 3, respectively; and de are enlarged SEM images of the sample regions in Examples 1-3, respectively.

[0018] Figure 3 The images shown are the detection spectra of the samples prepared in Example 3, where a and b are TEM images of the samples in Example 3; c is the HRTEM image of the samples in Example 3; and df is the lattice fringe pattern of the samples in Example 3.

[0019] Figure 4 The electromagnetic parameters of the samples in Examples 1, 2, and 3 are: a) real part of dielectric constant; b) imaginary part of dielectric constant; c) real part of permeability; d) imaginary part of permeability.

[0020] Figure 5 The diagram shows the reflection loss of Examples 1-3 in the frequency range of 2.0 ~ 18.0 GHz, where a is Example 1, b is Example 2, and c is Example 3.

[0021] Figure 6 This is a SEM image of the small-sized Fe2O3 hexagonal sheet in Comparative Example 1.

[0022] Figure 7 The diagram shows the reflection loss of Comparative Examples 1-3 in the frequency range of 2.0 ~ 18.0 GHz, where a is Comparative Example 1, b is Comparative Example 2, and c is Comparative Example 3. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0025] As used herein, the terms "and / or," "or / and," and "and / or" encompass any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that, in this application, the technical solution undoubtedly includes solutions connected by "logical AND," and also undoubtedly includes solutions connected by "logical OR."

[0026] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0027] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0028] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0029] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows temperature fluctuations within the precision range controlled by the instrument, such as ±5°C, ±4°C, ±3°C, ±2°C, or ±1°C.

[0030] In this document, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0031] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0032] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0033] In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0034] Unless otherwise specified, all preparations and tests described herein took place at 25°C.

[0035] The terms “comprising,” “including,” “containing,” “having,” “comprising,” or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term “comprising” means that other steps and ingredients may be added without affecting the final result. The compositions and methods / processes of the present invention comprise, consist of, and substantially consist of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein. No distinction is made between the terms “efficacy,” “performance,” “effect,” and “potency” herein.

[0036] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0037] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but sequentially is preferred.

[0038] Example 1: Preparation method of hexagonal plate-shaped Fe2O3: 4.054 g FeCl3·6H2O was dissolved in 30 mL of deionized water to obtain solution C. Then, 2.487 g CTAB and 49.654 g KOH were dissolved in 30 mL of deionized water and stirred magnetically for 1 h to obtain solution D. Solution C was then slowly added dropwise to solution D, and the mixture was stirred vigorously for 2 h. The mixture was then transferred to a 100 mL polytetrafluoroethylene-lined autoclave and placed in a 240 ℃ oven for 2 h. After cooling to room temperature, the sample was washed several times with deionized water and anhydrous ethanol. The sample was then placed in a vacuum drying oven at 60 ℃ and dried overnight. Finally, it was ground to obtain large-sized purplish-black Fe2O3 powder.

[0039] Preparation method of hexagonal plate-shaped Fe3O4@FeO@C: 1.6 g of large-size Fe2O3 sample was ultrasonically dispersed in 400 mL of Tris-HCl (pH=8.5) buffer solution to form a uniform suspension. Then, 1.6 g of dopamine hydrochloride was added under magnetic stirring at 550 r / min. After continuous stirring for 24 h, the sample was washed several times with deionized water and anhydrous ethanol. The sample was placed in a vacuum drying oven at 60 ℃ and dried overnight to obtain large-size Fe2O3@PDA sample. Then, the sample was annealed at 600 ℃ for 3 h under H2 / Ar (5% volume fraction) atmosphere to finally obtain large-size Fe3O4@FeO@C sample.

[0040] Preparation method of hexagonal plate-shaped Fe3O4@FeO@C@ZnIn2S4: 0.1 mmol ZnCl2, 0.2 mmol InCl3·4H2O, and 0.4 mmol C2H5NS were weighed and dissolved in a mixed solution of 80 mL deionized water and 20 mL glycerol. The solution was magnetically stirred for 30 min. Then, 0.1 g of large-sized Fe3O4@FeO@C sample was dispersed in the above solution and sonicated for 10 min. The solution was then placed in an oil bath at 80 °C for 2 h. After cooling to room temperature, the sample was washed several times with deionized water and anhydrous ethanol. The sample was then placed in a vacuum drying oven at 60 °C and dried overnight to obtain Fe3O4@FeO@C@ZnIn2S4-0.1 mmol, named FFCZ-0.1.

[0041] Example 2: The process is largely the same as in Example 1, except that the amount of ZnIn2S4 added is adjusted to 0.2 mmol (i.e., 0.2 mmol ZnCl2, 0.4 mmol InCl3·4H2O, and 0.8 mmol C2H5NS are added respectively). Fe3O4@FeO@C@ZnIn2S4-0.2 mmol is obtained and named FFCZ-0.2.

[0042] Example 3: Compared to Example 1, most aspects are the same, except that in this example, the amount of ZnIn2S4 added is adjusted to 0.4 mmol (i.e., 0.4 mmol ZnCl2, 0.8 mmol InCl3·4H2O, and 1.6 mmol C2H5NS are added respectively). Fe3O4@FeO@C@ZnIn2S4-0.4 mmol is obtained and named FFCZ-0.4.

[0043] The microstructure of the hexagonal sheet-like Fe3O4@FeO@C@ZnIn2S4 core-shell structure microwave absorbing material in the above embodiments was characterized using scanning electron microscopy (SEM, Hitachi FE-SEM S-4800). The powder sample was ultrasonically dispersed in ethanol and then dropped onto a conductive silicon wafer and dried for testing. A series of composite material microstructure information was characterized using transmission electron microscopy (TEM, JEOL JEM-2100F). The powder sample was ultrasonically dispersed in ethanol and then dropped onto a carbon-supported copper mesh and dried for testing. The electromagnetic properties in the 2.0 ~ 18.0 GHz range were tested using an Agilent N5224B vector network analyzer. The composite material was mixed with paraffin wax, with a sample filling amount of 70%, and pressed into rings with an outer diameter of 7.0 mm and an inner diameter of 3.04 mm, with a thickness between 1 and 3 mm. The microwave absorption performance of ring samples with different thicknesses was simulated and tested using the vector network analyzer.

[0044] like Figure 1 As shown in Figure ac, the Fe2O3 sample exhibits a regular hexagonal plate-like structure with a smooth surface. Statistical analysis revealed that the diameter of the hexagonal plate is approximately 12.6 μm, the side length is approximately 6.4 μm, and the thickness is approximately 2 μm. After 24 h of oxidative self-polymerization of polydopamine followed by annealing in an H2 / Ar atmosphere, the resulting Fe3O4@FeO@C material retains the basic morphology of the hexagonal plates, but the surface is coated with a layer of amorphous carbon, significantly increasing its roughness. Figure 1 d and e). Further, ZnIn2S4 nanosheets with varying contents were grown on Fe3O4@FeO@C hexagonal sheets using a hydrothermal method. The material surface was covered by stacked fine nanosheets, resulting in a smooth surface. Figure 2 af). The above results successfully constructed a multilayer core-shell composite microwave absorbing material with Fe3O4@FeO as the magnetic core, polydopamine-derived carbon as the intermediate layer, and ZnIn2S4 semiconductor as the outer shell. TEM analysis further confirmed the core-shell structure of the Fe3O4@FeO@C@ZnIn2S4-0.4 mmol sample in Example 3 ( Figure 3a) The clear lattice fringes observed in different regions confirm the successful recombination of the Fe3O4, FeO, and ZnIn2S4 multiphases. Specifically, a 0.153 nm interplanar spacing is visible in region d, which corresponds to the (220) crystal plane of FeO. The adjacent region e shows lattice fringes of 0.162 nm, which can be identified as the (511) crystal plane of Fe3O4. Meanwhile, the lattice spacings exhibited in region f are 0.182 nm and 0.312 nm, respectively, which perfectly correspond to the (0117) and (104) crystal planes of ZnIn2S4.

[0045] Figure 4 The real and imaginary parts of the complex permittivity and the real and imaginary parts of the complex permeability of the hexagonal sheet-like Fe3O4@FeO@C@ZnIn2S4 core-shell structure materials prepared in Examples 1, 2, and 3 above are used to reveal the mechanism of their excellent microwave absorption performance. The ε' and ε'' curves of the FFCZ-0.1, FFCZ-0.2, and FFCZ-0.4 composite materials generally show a trend of first increasing and then decreasing. Notably, as the loading of the ZnIn2S4 shell increases from 0.1 mmol to 0.4 mmol, the complex permittivity of the composite material shows a slight decrease. At the same time, in the 6-14 GHz frequency band, the ε' and ε'' of FFCZ-0.1, FFCZ-0.2, and FFCZ-0.4 all show a broadened relaxation peak with considerable intensity. This phenomenon indicates that the introduction of ZnIn2S4 mainly contributes to polarization relaxation loss. A heterogeneous interface is formed between the ZnIn2S4 semiconductor shell and the carbon layer, inducing interfacial polarization. Furthermore, inherent defects in ZnIn2S4 itself contribute to dipole polarization. As the ZnIn2S4 shell loading increases, the interfacial area and the number of defects increase, but this also hinders charge migration, leading to a decrease in the overall dielectric constant and an increase in relaxation loss. With increasing ZnIn2S4 content, μ′ and φ″ show a decreasing trend (…). Figure 4 (c and d). Specifically, the μ′ value at 2 GHz decreased from 1.63 (FFCZ-0.1) to 1.60 (FFCZ-0.2) and 1.58 (FFCZ-0.4), while the corresponding μ″ values ​​decreased from 0.48 and 0.47 to 0.35. This is directly related to the reduced proportion of the magnetic phase in the composite material. However, all samples maintained effective magnetic loss capability, thanks to their saturation magnetization and hexagonal plate-like core-shell structure.

[0046] Figure 4The image shows the reflection loss of the hexagonal plate-shaped Fe3O4@FeO@C@ZnIn2S4 core-shell structure composite materials in Examples 1, 2, and 3 in the range of 2.0 to 18.0 GHz. Wherein a represents the reflection loss of FFCZ-0.1 in Example 1 within the frequency range of 2.0~18.0 GHz, it was found that at a thickness of 2.28 mm, the electromagnetic wave absorption capability can reach 56.6 dB at 8.64 GHz, with an effective absorption bandwidth of 3.28 GHz; b represents the reflection loss of FFCZ-0.2 in Example 2 within the frequency range of 2.0~18.0 GHz, it was found that at a thickness of 1.93 mm, the electromagnetic wave absorption capability can reach 53.5 dB at 13.12 GHz, with an effective absorption bandwidth of 4.82 GHz; c represents the reflection loss of FFCZ-0.4 within the frequency range of 2.0~18.0 GHz, it was found that at a thickness of 1.91 mm, the electromagnetic wave absorption capability can reach -53.9 dB at 13.2 GHz, with an effective absorption bandwidth of 5.44 GHz. In Example 3, the FFCZ-0.4 composite material exhibits the best overall performance in the material system. Although its real part of dielectric constant is not the highest, this moderate dielectric property is precisely conducive to achieving optimal impedance matching, allowing more electromagnetic waves to enter the interior of the material and be efficiently dissipated by multiple synergistic mechanisms, thereby obtaining excellent wave absorption performance.

[0047] Comparative Example 1: Compared to Example 3, most aspects are the same, except that the large-sized Fe2O3 hexagonal sheets are transformed into small-sized Fe2O3 hexagonal sheets. The specific preparation process of the small-sized Fe2O3 hexagonal sheets is as follows: Solution A was prepared by dissolving 1.352 g FeCl3·6H2O in 50 mL of anhydrous ethanol. Then, 1 g NaOH and 9.58 g KAc were dissolved in 5 mL of H2O, respectively. The solutions were ultrasonically treated to obtain solution B. Solution B was slowly added dropwise to solution A. The mixture was stirred vigorously for 1 h. The resulting solution was transferred to a 100 mL high-pressure autoclave lined with polytetrafluoroethylene (PTFE) and placed in an oven at 180 °C for 6 h. After the reaction was complete, the mixture was cooled to room temperature and washed several times with deionized water and anhydrous ethanol. The sample was then dried overnight in a vacuum drying oven at 60 °C. Finally, it was ground to obtain small-sized reddish-brown Fe2O3 powder.

[0048] Comparative Example 2: Compared to Example 3, most aspects are the same, except that the annealing process is changed to be performed after in-situ growth of ZnIn2S4 nanosheets (demonstrating the importance of specific annealing processes for the formation of three-layer composite structures and subsequent optimization of microwave absorption performance). The specific preparation process is as follows: 4.054 g of FeCl3·6H2O was dissolved in 30 mL of deionized water to obtain solution C. Then, 2.487 g of CTAB and 49.654 g of KOH were dissolved in 30 mL of deionized water, and the mixture was stirred magnetically for 1 h to obtain solution D. Solution C was then slowly added dropwise to solution D, and the mixture was stirred vigorously for 2 h. The mixture was then transferred to a 100 mL PTFE-lined autoclave and placed in a 240 ℃ oven for 2 h. After cooling to room temperature, the sample was washed several times with deionized water and anhydrous ethanol, and then placed in a 60 ℃ vacuum drying oven to dry overnight. Finally, the sample was ground to obtain large-sized purplish-black Fe2O3 powder.

[0049] 1.6 g of large-size Fe2O3 sample was ultrasonically dispersed in 400 mL of Tris-HCl (pH=8.5) buffer solution to form a homogeneous suspension. Then, 1.6 g of dopamine hydrochloride was added under magnetic stirring at 550 r / min. After continuous stirring for 24 h, the sample was washed several times with deionized water and anhydrous ethanol. The sample was then placed in a vacuum drying oven at 60 ℃ and dried overnight to obtain large-size Fe2O3@PDA sample.

[0050] 0.4 mmol ZnCl2, 0.8 mmol InCl3·4H2O, and 1.6 mmol C2H5NS were weighed and dissolved in a mixed solution of 80 mL deionized water and 20 mL glycerol. The solution was magnetically stirred for 30 min. Then, 0.1 g of large-size Fe2O3@PDA sample was dispersed in the above solution and sonicated for 10 min. The sample was then placed in an oil bath at 80 °C for 2 h. After cooling to room temperature, the sample was washed several times with deionized water and anhydrous ethanol. The sample was then placed in a vacuum drying oven at 60 °C and dried overnight. Finally, the sample was annealed at 600 °C for 3 h under a H2 / Ar (5% by volume) atmosphere.

[0051] Comparative Example 3: Compared with Example 3, most aspects are the same, except that the ZnIn2S4 shell is replaced with a MoS2 shell to reflect the importance and special nature of ZnIn2S4 in the present invention. The specific preparation process of the MoS2 shell is as follows: 0.06 g of thiourea, 0.03 g of sodium molybdate dihydrate, and 0.03 g of glucose were weighed and dissolved in 30 mL of deionized water. The mixture was magnetically stirred for 10 min. Then, 0.1 g of large-size Fe3O4@FeO@C sample was dispersed in the above solution and sonicated for 30 min. The mixed solution was transferred to a 50 mL polytetrafluoroethylene-lined autoclave and placed in a 200 ℃ oven for 20 h. After cooling to room temperature, the sample was washed several times with deionized water and anhydrous ethanol. The sample was then placed in a vacuum drying oven at 60 ℃ and dried overnight. Finally, it was ground to obtain Fe3O4@FeO@C@MoS2 powder.

[0052] like Figure 6 As shown, the average thickness, side length, and diameter of the small-sized Fe2O3 hexagonal flakes are 0.36 μm, 2.96 μm, and 5.46 μm, respectively; while the corresponding dimensions of the large-sized Fe2O3 hexagonal flakes increase to 1.99 μm, 6.36 μm, and 12.55 μm, respectively. This significant size difference affects the microwave absorption properties of its composite material. Figure 7 As shown in Figure a, the small-sized Fe3O4@FeO@C@ZnIn2S4 hexagonal composite material in Comparative Example 1 can achieve an electromagnetic wave absorption capability of 39.2 dB at 17.12 GHz, with an effective absorption bandwidth of 1.52 GHz.

[0053] The annealing process was changed to be performed after in-situ growth of ZnIn2S4 nanosheets, highlighting the importance of specific annealing processes for the formation of three-layer composite structures and subsequent optimization of microwave absorption performance. Figure 7 As shown in Figure b, the composite material in Comparative Example 2 can achieve an electromagnetic wave absorption capability of -19.8 dB at 16 GHz, with an effective absorption bandwidth of 1.76 GHz.

[0054] The ZnIn2S4 shell is replaced with a MoS2 shell to highlight the importance and uniqueness of ZnIn2S4 in the present invention, such as... Figure 7 As shown in Figure c, the composite material in Comparative Example 3 can achieve an electromagnetic wave absorption capability of 31.1 dB at 14.48 GHz, with an effective absorption bandwidth of 4.8 GHz.

[0055] Compared with Comparative Examples 1, 2 and 3, the composite material prepared by the present invention exhibits significant advantages in wave absorption performance, specifically a wider effective absorption bandwidth and a stronger reflection loss value.

[0056] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A hexagonal sheet-like Fe3O4@FeO@C@ZnIn2S4 core-shell structure microwave absorbing material, characterized in that, It is hexagonal in shape, with Fe3O4@FeO as the magnetic core, polydopamine-derived carbon as the intermediate layer, and ZnIn2S4 semiconductor as the outer shell.

2. The preparation method of the hexagonal sheet-like Fe3O4@FeO@C@ZnIn2S4 core-shell structure microwave absorbing material as described in claim 1, characterized in that, Includes the following steps: S1. Dissolve soluble iron salt in deionized water and stir to obtain solution A. Weigh hexadecyltrimethylammonium bromide and potassium hydroxide and dissolve them in deionized water to obtain solution B. Add solution A dropwise to solution B, stir, and then transfer to a reaction vessel for reaction. Wash and dry the resulting reaction product to obtain hexagonal plate-shaped Fe2O3 powder. S2. Disperse hexagonal plate-shaped Fe2O3 powder in Tris-HCl buffer solution to form a suspension, then add dopamine hydrochloride, stir the reaction, wash the product, dry it, and anneal it to obtain hexagonal plate-shaped Fe3O4@FeO@C powder. S3. Weigh out the zinc source, indium source and sulfur source and dissolve them in a mixed solution of water and glycerol. Then add the Fe3O4@FeO@C powder obtained in S2, disperse it by ultrasonication, and heat it to react to obtain Fe3O4@FeO@C@ZnIn2S4 powder, which is the target product.

3. The method for preparing a hexagonal sheet-like Fe3O4@FeO@C@ZnIn2S4 core-shell structure microwave absorbing material according to claim 2, characterized in that, In S1, the soluble iron salt is ferric chloride or its hydrate; The amounts of solution A and solution B added satisfy the following: the molar ratio of ferric chloride, hexadecyltrimethylammonium bromide, and potassium hydroxide is (14 ~ 16) mmol : (6.5 ~ 7.5) mmol : (0.8 ~ 0.9) mol.

4. The method for preparing a hexagonal sheet-like Fe3O4@FeO@C@ZnIn2S4 core-shell structure microwave absorbing material according to claim 2, characterized in that, In S1, the reaction temperature is 220~250 ℃ and the time is 1~3h.

5. The method for preparing a hexagonal sheet-like Fe3O4@FeO@C@ZnIn2S4 core-shell structure microwave absorbing material according to claim 2, characterized in that, In S2, the mass ratio of hexagonal plate-shaped Fe2O3 powder to dopamine hydrochloride is (0.8 ~ 1.2): (0.8 ~ 1.2).

6. The method for preparing a hexagonal sheet-like Fe3O4@FeO@C@ZnIn2S4 core-shell structure microwave absorbing material according to claim 2, characterized in that, In S2, the stirring reaction is carried out at room temperature for 12 to 36 hours; annealing is carried out under a reducing atmosphere at a temperature of 500 to 700 °C for 2 to 4 hours.

7. The method for preparing a hexagonal sheet-like Fe3O4@FeO@C@ZnIn2S4 core-shell structure microwave absorbing material according to claim 2, characterized in that, In S3, the amounts of zinc source, indium source, and sulfur source added satisfy the following condition: Zn 2+ In 3+ S 2- The molar ratio is 1:2:(4~8).

8. The method for preparing a hexagonal sheet-like Fe3O4@FeO@C@ZnIn2S4 core-shell structure microwave absorbing material according to claim 2, characterized in that, In S3, the ratio of Fe3O4@FeO@C powder to zinc source is 0.1 g: (0.1 ~ 0.4) mmol.

9. The method for preparing a hexagonal sheet-like Fe3O4@FeO@C@ZnIn2S4 core-shell structure microwave absorbing material according to claim 2, characterized in that, In S3, the heating reaction is carried out at a temperature of 70 ~ 90 ℃ for 1 ~ 3 h.

10. The application of the hexagonal sheet-like Fe3O4@FeO@C@ZnIn2S4 core-shell structure absorbing material as described in claim 1 in the field of electromagnetic protection and stealth coating.

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