Metal ion doped magnetic medium cooperative core-shell structure wave-absorbing material, preparation method and application thereof

Abstract

The application discloses a kind of metal ion doped magnetic medium cooperative core-shell structure wave-absorbing material and its preparation method and application.The core layer of the wave-absorbing material described in the application is iron-based material, and the shell layer is a manganese dioxide layer doped with metal ions coated on the surface of the core layer.By using a hydrothermal method to prepare magnetite nanoparticles with uniform size, and using potassium permanganate, manganese sulfate monohydrate and metal salt as reaction raw materials, the application continues to use a hydrothermal method to grow manganese dioxide doped with metal ions on the surface of the magnetite, forming a wave-absorbing material with a core-shell structure.The wave-absorbing material prepared by the application has multiple loss mechanisms such as dielectric loss, magnetic loss, internal reflection and scattering loss, has excellent wave-absorbing performance, and has a wide absorption frequency band, good impedance matching, a simple preparation method, and is suitable for continuous industrial production.

Description

Technical Field

[0001] This invention relates to the field of composite material preparation technology, and in particular to a metal ion-doped magnetic-medium synergistic core-shell structure microwave absorbing material, its preparation method, and its application. Background Technology

[0002] With the application of electromagnetic waves in various electronic devices, while greatly facilitating people's production and daily life, it has also generated high-energy radiation and unnecessary electromagnetic interference, causing serious electromagnetic pollution. To address this electromagnetic pollution problem, the research and development of various high-performance microwave absorbing materials is of paramount importance. In the past decade or so, researchers have made tremendous efforts in designing and preparing highly efficient microwave absorbers, but they still suffer from drawbacks such as high absorption bands, high density, difficulty in industrialization, high preparation costs, and complex industrial processes, making it difficult to meet the requirements of being "strong, wide-band, thin, and lightweight."

[0003] Currently, commonly used microwave absorbing materials include dielectric loss materials such as carbon materials and MXene, as well as magnetic loss materials such as magnetic metals and ferrites. Among them, magnetite (Fe3O4) is a dual-complex electromagnetic material containing both dielectric and magnetic losses, and therefore has always been one of the most widely used microwave absorbing materials. However, the high density and narrow effective bandwidth of traditional magnetite absorbing agents limit its application. To solve this problem, ion doping is used to broaden the bandwidth, and combining it with other dielectric materials and designing unique structures can improve the density.

[0004] Manganese dioxide is characterized by stable performance, low density, and a wide variety of microstructures and crystal structures, making it a promising microwave absorbing material. It is used in conjunction with ferrites, polymers, and carbon materials, and has been the subject of much research in the field of electromagnetic wave absorption.

[0005] Patent CN108840371A discloses a method for preparing iron tetroxide / manganese dioxide composite microspheres, which exhibit a large specific surface area, good magnetic properties, and excellent electrical conductivity. At a thickness of 2.5 mm, the absorption loss (RLmin) can reach -22 dB, and the absorption bandwidth is 5.2 GHz. However, the absorption loss and absorption bandwidth cannot be simultaneously satisfied.

[0006] Therefore, it is of great significance to develop an absorbing material with excellent electromagnetic wave absorption performance, wide absorption bandwidth, and good impedance matching. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a metal ion-doped magnetic-medium synergistic core-shell structure microwave absorbing material, its preparation method, and its applications. The Fe3O4@M-Doped MnO2 nano-hybrid material prepared by this invention solves the problems of high density of iron(III) oxide and poor impedance matching of manganese dioxide. By controlling the particle size of iron(III) oxide, the morphology and crystal form of manganese dioxide, and the ion doping concentration, a special structure hybrid material is produced, exhibiting excellent microwave absorption performance, wide absorption bandwidth, good impedance matching, and a simple preparation method, making it suitable for continuous industrial production.

[0008] The technical solution of the present invention is as follows:

[0009] This invention first protects a metal ion-doped magnetic-medium synergistic core-shell structure microwave absorbing material, wherein the core layer of the microwave absorbing material is an iron-based material, and the shell layer is a metal ion-doped manganese dioxide layer covering the surface of the core layer;

[0010] In the microwave absorbing material, the mass ratio of the core layer to the shell layer is 1:1 to 2.5;

[0011] In the shell, the molar ratio of metal ions to manganese ions is 1~2:1~2.

[0012] Furthermore, the metal ions include one or more of cobalt ions and nickel ions, with cobalt ions being preferred.

[0013] This invention also protects a method for preparing the aforementioned metal ion-doped magnetic-dielectric synergistic core-shell structure microwave absorbing material, comprising the following steps:

[0014] S1: Preparation of iron oxide nanoparticles;

[0015] S2: Dissolve potassium permanganate in water to obtain potassium permanganate solution; mix manganese sulfate monohydrate and metal salt and dissolve in water to obtain mixed solution I;

[0016] S3: Add the iron oxide nanoparticles prepared in step S1 to the mixed solution I in step S2, stir evenly to obtain mixed solution II, and add potassium permanganate solution while stirring to obtain mixed solution III;

[0017] S4: Transfer the mixed solution III to the reactor, react at high temperature, wash, centrifuge, and dry the precipitate to obtain Fe3O4@M-Doped MnO2 nano-hybrid material, namely, metal ion doped magnetic media synergistic core-shell structure microwave absorbing material.

[0018] Further, in step S1, the preparation method of the iron oxide nanoparticles is as follows:

[0019] Ferric chloride hexahydrate, sodium citrate, and urea were dissolved in water to obtain a mixed solution, which was placed in a reaction vessel. After the reaction, the product was magnetically separated, the supernatant was removed, and the resulting solid particles were washed and dried at 60-80°C to obtain iron oxide nanoparticles.

[0020] Furthermore, the mass-to-volume ratio of ferric chloride hexahydrate, sodium citrate, urea, and water is 3-5 g: 7-11.6 g: 2-3.4 g: 200 mL; the reaction temperature is 200-240 °C, and the reaction time is 12-18 h.

[0021] Furthermore, the particle size of the iron oxide nanoparticles is 20~60nm.

[0022] Further, in step S2, the molar volume ratio of potassium permanganate to water in the potassium permanganate solution is 2-4 mmol: 60 mL; the molar volume ratio of manganese sulfate monohydrate, metal salt, and water in the mixed solution I is 3-6 mmol: 5-10 mmol: 60 mL; the metal salt includes one or more of cobalt sulfate heptahydrate, nickel sulfate, and copper sulfate.

[0023] Further, in step S3, the mass fraction of iron oxide nanoparticles in the mixed solution II is 0.64%; the volume ratio of the mixed solution II to the potassium permanganate solution is 1~2:1.

[0024] Furthermore, in step S4, the high-temperature reaction temperature is 100~180℃ and the time is 6~12h; the drying temperature is 60~80℃ and the time is 18~24h.

[0025] This invention also protects a metal ion-doped magnetic-dielectric synergistic core-shell structure absorbing material for electromagnetic wave absorption.

[0026] The beneficial technical effects of this invention are as follows:

[0027] The Fe3O4@M-Doped MnO2 nanohybrid material prepared by this invention has excellent microwave absorption performance, wide absorption bandwidth, good impedance matching, and simple preparation method, making it suitable for continuous industrial production.

[0028] The Fe3O4@M-Doped MnO2 nano-hybrid composite microwave absorbing material prepared in this invention has a special bilayer structure, namely, Fe3O4 as the core and metal ions, especially cobalt-doped manganese dioxide, as the outermost coating layer. Since the particle size of Fe3O4, the morphology of manganese dioxide, and the doping amount of cobalt ions can all be controlled, the electromagnetic parameters can be effectively adjusted by the interaction of the material's microstructure and external morphology. Furthermore, impedance matching control is achieved by utilizing a multi-level structure synergistic absorption mechanism, resulting in excellent electromagnetic wave absorption performance.

[0029] The Fe3O4@M-Doped MnO2 nano-hybrid material prepared in this invention has multiple electromagnetic wave loss mechanisms. Fe3O4 is mainly characterized by magnetic loss, while MnO2 is mainly characterized by dielectric polarization loss. The synergistic effect of multiple loss mechanisms helps to enhance reflection loss and expand absorption bandwidth. In addition, the special double-layer core-shell structure and spiky appearance of the composite absorber help to enhance the loss capability through multiple reflections and scattering of electromagnetic waves.

[0030] The ion doping of the Fe3O4@M-Doped MnO2 nanohybrid material prepared in this invention improves the material's stability. Ion doping can modify the material's conductivity and dielectric loss by controlling its crystal structure and electronic structure, thereby further improving the material's microwave absorption performance. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of elemental analysis of the material prepared in Example 1 of the present invention.

[0032] Figure 2 The image shows the XRD pattern of the comparative example 3Fe3O4@MnO2 of this invention.

[0033] Figure 3 The image shown is the XRD pattern of iron(III) oxide (Fe3O4) for Comparative Example 1 of this invention.

[0034] Figure 4 This is a SEM image of the material prepared in Example 1 of the present invention.

[0035] In the figure: (a) is a SEM image of Fe3O4@Co-Doped MnO2 nanohybrid material; (b) is a SEM image with a different magnification ratio than (a). Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0037] This invention provides a metal ion-doped magnetic dielectric synergistic core-shell structure microwave absorbing material. By preparing the core-shell structure, materials with different loss mechanisms can be combined to achieve the synergistic effect of multiple loss mechanisms. At the same time, it can provide more interfaces, increase interface loss, and improve microwave absorption performance in multiple ways.

[0038] Meanwhile, the core layer is made of iron-based material, specifically iron(III) oxide, which can achieve excellent magnetic loss. Iron(III) oxide has high magnetic permeability and magnetic saturation strength, is easy to prepare, has high chemical stability, and is a dual complex electromagnetic material containing both dielectric and magnetic losses.

[0039] In addition, the outer shell is manganese dioxide doped with metal ions. Manganese dioxide as the outer shell can provide dielectric polarization loss. The doping of metal ions, especially cobalt ions, can increase the conductivity and dielectric loss of the material. Furthermore, by controlling the amount of doped metal ions, the stability of the material structure is improved. It can also adjust the impedance matching characteristics of the material to better match the external electromagnetic field and improve the wave absorption effect.

[0040] The outer layer of the double-core-shell structure, formed by the hydrothermal synthesis of manganese dioxide, has a spiky appearance with a large specific surface area. This is beneficial for increasing the interaction between the material and electromagnetic waves, enabling multiple reflections and scattering of electromagnetic waves, further allowing for the adjustment of electromagnetic parameters and enhancing the absorption capacity of electromagnetic waves.

[0041] The material prepared by this invention combines manganese dioxide, which has the main electrical loss, and iron oxide, which has the main magnetic loss, so that the material has the characteristics of both. At the same time, it has multiple interfaces, which can further enhance the microwave absorption capability of the material.

[0042] The material prepared by this invention has an absorbent designed with a core-shell structure, which can prevent the agglomeration of manganese dioxide; at the same time, manganese dioxide is used to coat ferric oxide, thereby improving the corrosion resistance of ferric oxide.

[0043] Example 1:

[0044] The electromagnetic wave absorbing material is prepared by the following method:

[0045] (1) In a beaker, the reactants ferric chloride hexahydrate, sodium citrate, and urea were dissolved in deionized water at a mass-to-volume ratio of 3g:7g:2g:200mL. After stirring until completely dissolved, the yellow solution was transferred to a reaction vessel and reacted at 200℃ for 12h. After the reaction was completed, the product was magnetically separated, the supernatant was removed, and the resulting solid particles were washed several times with deionized water and ethanol, respectively. Then, they were placed in a vacuum oven, dried at 60℃, and collected for later use.

[0046] (2) Dissolve 0.316g of potassium permanganate in 60mL of deionized water and stir until completely dissolved. This solution is labeled as solution A or potassium permanganate solution. Dissolve 0.507g of manganese sulfate monohydrate and 2.81g of cobalt sulfate heptahydrate in 60mL of deionized water. This solution is labeled as solution B or mixed solution I. Stir until completely dissolved. Dissolve 0.385g of iron oxide nanoparticles from step (1) in solution B, with a mass fraction of 0.64%. Stir until mixed solution II is obtained. Then, slowly add solution A to mixed solution II at a volume ratio of 1:1 while stirring until homogeneous to form solution C or mixed solution III. Stir for another 30 minutes.

[0047] (3) Transfer the C solution from (2) above to a reaction vessel and react at 100°C for 6 h. Then, wash the obtained product several times with distilled water to remove unwanted soluble ions, wash, centrifuge, and dry the precipitate at 80°C for 24 h to obtain Fe3O4@Co-Doped MnO2 nano-hybrid material. Its elemental analysis is shown in [see table below]. Figure 1 SEM images of nano-hybrid materials are shown below. Figure 4 As shown.

[0048] Example 2

[0049] (1) In a beaker, the reactants ferric chloride hexahydrate, sodium citrate, and urea were dissolved in deionized water at a mass-to-volume ratio of 3g:7g:2g:200mL. After stirring until completely dissolved, the yellow solution was transferred to a reaction vessel and reacted at 200℃ for 15h. After the reaction was completed, the product was magnetically separated, the supernatant was removed, and the resulting solid particles were washed several times with deionized water and ethanol, respectively. Then, they were placed in a vacuum oven, dried at 60℃, and collected for later use.

[0050] (2) Dissolve 0.632g of potassium permanganate in 60mL of deionized water and stir until completely dissolved. This solution is labeled as solution A or potassium permanganate solution. Dissolve 1.014g of manganese sulfate monohydrate and 1.405g of cobalt sulfate heptahydrate in 60mL of deionized water. This solution is labeled as solution B or mixed solution I. Stir until completely dissolved. Dissolve 0.385g of iron oxide nanoparticles from step (1) in solution B, with a mass fraction of 0.64%. Stir until mixed solution II is obtained. Then, slowly add solution A to mixed solution II at a volume ratio of 1:1 while stirring until homogeneous to form solution C or mixed solution III. Stir for another 60 minutes.

[0051] (3) Transfer the C solution from (2) above to a reaction vessel and react at 140°C for 9 h. Then, wash the obtained product several times with distilled water to remove undesirable soluble ions, wash, centrifuge, and dry the precipitate at 80°C for 24 h to obtain Fe3O4@Co-Doped MnO2 nano-hybrid material.

[0052] Example 3

[0053] (1) In a beaker, the reactants ferric chloride hexahydrate, sodium citrate, and urea were dissolved in deionized water at a mass-to-volume ratio of 3g:7g:2g:200mL. After stirring until completely dissolved, the yellow solution was transferred to a reaction vessel and reacted at 200℃ for 18h. After the reaction was completed, the product was magnetically separated, the supernatant was removed, and the resulting solid particles were washed several times with deionized water and ethanol, respectively. Then, they were placed in a vacuum oven, dried at 60℃, and collected for later use.

[0054] (2) Dissolve 0.632g of potassium permanganate in 60mL of deionized water and stir until completely dissolved. This solution is labeled as solution A or potassium permanganate solution. Dissolve 1.014g of manganese sulfate monohydrate and 2.81g of cobalt sulfate heptahydrate in 60mL of deionized water. This solution is labeled as solution B or mixed solution I. Stir until completely dissolved. Dissolve 0.385g of iron oxide nanoparticles from step (1) in solution B, with a mass fraction of 0.64%. Stir until mixed solution II is obtained. Then, slowly add solution A to mixed solution II at a volume ratio of 1:1 while stirring until homogeneous to form solution C or mixed solution III. Stir for another 40 minutes.

[0055] (3) Transfer the C solution from (2) above to a reaction vessel and react at 180°C for 12 h. Then, wash the obtained product several times with distilled water to remove undesirable soluble ions, wash, centrifuge, and dry the precipitate at 80°C for 24 h to obtain Fe3O4@Co-Doped MnO2 nano-hybrid material.

[0056] Example 4:

[0057] (1) In a beaker, the reactants ferric chloride hexahydrate, sodium citrate, and urea were dissolved in deionized water at a mass-to-volume ratio of 5g:11.6g:3.4g:200mL. After stirring until completely dissolved, the yellow solution was transferred to a reaction vessel and reacted at 240℃ for 12h. After the reaction was completed, the product was magnetically separated, the supernatant was removed, and the resulting solid particles were washed several times with deionized water and ethanol, respectively. Then, they were placed in a vacuum oven and dried at 60℃ before being collected for later use.

[0058] (2) Dissolve 0.316g of potassium permanganate in 60mL of deionized water and stir until completely dissolved. This solution is labeled as solution A or potassium permanganate solution. Dissolve 0.507g of manganese sulfate monohydrate and 2.81g of cobalt sulfate heptahydrate in 60mL of deionized water. This solution is labeled as solution B. Stir until completely dissolved. Dissolve 0.385g of iron oxide nanoparticles from step (1) in solution B, with a mass fraction of 0.64%. Stir until homogeneous to obtain mixed solution II. Then, slowly add solution A to mixed solution II at a volume ratio of 1:1 while stirring until homogeneous to form solution C or mixed solution III. Stir for another 30 minutes.

[0059] (3) Transfer the C solution from (2) above to a reaction vessel and react at 100°C for 6 h. Then, wash the obtained product several times with distilled water to remove undesirable soluble ions, wash, centrifuge, and dry the precipitate at 80°C for 24 h to obtain Fe3O4@Co-Doped MnO2 nano-hybrid material.

[0060] Example 5

[0061] (1) In a beaker, the reactants ferric chloride hexahydrate, sodium citrate, and urea were dissolved in deionized water at a mass-to-volume ratio of 5g:11.6g:3.4g:200mL. After stirring until completely dissolved, the yellow solution was transferred to a reaction vessel and reacted at 240℃ for 15h. After the reaction was completed, the product was magnetically separated, the supernatant was removed, and the resulting solid particles were washed several times with deionized water and ethanol, respectively. Then, they were placed in a vacuum oven and dried at 60℃ before being collected for later use.

[0062] (2) Dissolve 0.632g of potassium permanganate in 60mL of deionized water and stir until completely dissolved. This solution is labeled as solution A or potassium permanganate solution. Dissolve 1.014g of manganese sulfate monohydrate and 1.405g of cobalt sulfate heptahydrate in 60mL of deionized water. This solution is labeled as solution B. Stir until completely dissolved. Dissolve 0.385g of iron oxide nanoparticles from step (1) in solution B, with a mass fraction of 0.64%. Stir until homogeneous to obtain mixed solution II. Then, slowly add solution A to mixed solution II at a volume ratio of 1:1 while stirring until homogeneous to form solution C or mixed solution III. Stir for another 30 minutes.

[0063] (3) Transfer the C solution from (2) above to a reaction vessel and react at 140°C for 9 h. Then, wash the obtained product several times with distilled water to remove undesirable soluble ions, wash, centrifuge, and dry the precipitate at 80°C for 24 h to obtain Fe3O4@Co-Doped MnO2 nano-hybrid material.

[0064] Example 6

[0065] (1) In a beaker, the reactants ferric chloride hexahydrate, sodium citrate, and urea were dissolved in deionized water at a mass-to-volume ratio of 5g:11.6g:3.4g:200mL. After stirring until completely dissolved, the yellow solution was transferred to a reaction vessel and reacted at 240℃ for 18h. After the reaction was completed, the product was magnetically separated, the supernatant was removed, and the resulting solid particles were washed several times with deionized water and ethanol, respectively. Then, they were placed in a vacuum oven, dried at 60℃, and collected for later use.

[0066] (2) Dissolve 0.632g of potassium permanganate in 60mL of deionized water and stir until completely dissolved. This solution is labeled as solution A or potassium permanganate solution. Dissolve 1.014g of manganese sulfate monohydrate and 2.81g of cobalt sulfate heptahydrate in 60mL of deionized water. This solution is labeled as solution B or mixed solution I. Stir until completely dissolved. Dissolve 0.385g of iron oxide nanoparticles from step (1) in solution B, with a mass fraction of 0.64%. Stir until mixed solution II is obtained. Then, slowly add solution A to mixed solution II at a volume ratio of 1:1 while stirring until homogeneous to form solution C or mixed solution III. Stir for another 30 minutes.

[0067] (3) Transfer the C solution from (2) above to a reaction vessel and react at 180°C for 12 h. Then, wash the obtained product several times with distilled water to remove undesirable soluble ions, wash, centrifuge, and dry the precipitate at 80°C for 24 h to obtain Fe3O4@Co-Doped MnO2 nano-hybrid material.

[0068] Comparative Example 1:

[0069] In a beaker, ferric chloride hexahydrate, sodium citrate, and urea were dissolved in deionized water at a mass-to-volume ratio of 3 g:7 g:2 g:200 mL. The mixture was stirred until completely dissolved. The yellow solution was then transferred to a reaction vessel and reacted at 200°C for 12 hours. After the reaction, the product was magnetically separated, and the supernatant was removed. The resulting solid particles were washed several times with deionized water and ethanol, respectively, and then dried in a vacuum oven at 60°C for later use. The XRD pattern is shown below. Figure 3 .

[0070] Comparative Example 2:

[0071] In a beaker, ferric chloride hexahydrate, sodium citrate, and urea were dissolved in deionized water at a mass-to-volume ratio of 5 g: 11.6 g: 3.4 g: 200 mL. The mixture was stirred until completely dissolved. The yellow solution was then transferred to a reaction vessel and reacted at 240°C for 12 hours. After the reaction, the product was magnetically separated, and the supernatant was removed. The resulting solid particles were washed several times with deionized water and ethanol, respectively, and then dried in a vacuum oven at 60°C for later use.

[0072] Comparative Example 3:

[0073] (1) In a beaker, the reactants ferric chloride hexahydrate, sodium citrate, and urea were dissolved in deionized water at a mass-to-volume ratio of 3g:7g:2g:200mL. After stirring until completely dissolved, the mixture was transferred to a reaction vessel and reacted at 200℃ for 12 hours. After the reaction was completed, the product was magnetically separated using a magnet. The supernatant was removed, and the resulting solid particles were washed several times with deionized water and ethanol, respectively. Then, the particles were placed in a vacuum oven and dried at 60℃ before being collected for later use.

[0074] (2) Dissolve 0.316g of potassium permanganate in 60mL of deionized water and stir until completely dissolved. This solution is labeled A. Dissolve 0.507g of manganese sulfate monohydrate in 60mL of deionized water and label this solution B. Stir until completely dissolved. Based on the mass fraction of 0.64% for the iron oxide nanoparticles, dissolve 0.385g of the iron oxide nanoparticles from (1) in solution B to obtain a solution with a mass fraction of 0.64%. Stir until homogeneous. Then, slowly add solution A at a volume ratio of 1:1, stirring constantly to form solution C. Stir for another 30-60 minutes.

[0075] (3) Transfer the C solution from (2) above to a reaction vessel and react at 100°C for 6 hours. Then, wash the obtained solid particles several times with deionized water to remove unwanted soluble ions, wash, centrifuge, and dry the precipitate at 80°C for 24 hours to obtain Fe3O4@MnO2 nano-hybrid material. Its XRD pattern is shown in [Figure number missing]. Figure 2 .

[0076] Comparative Example 4:

[0077] (1) In a beaker, the reactants ferric chloride hexahydrate, sodium citrate, and urea were dissolved in deionized water at a mass-to-volume ratio of 3g:7g:2g:200mL. After stirring until completely dissolved, the mixture was transferred to a reaction vessel and reacted at 200℃ for 12 hours. After the reaction was completed, the product was magnetically separated using a magnet. The supernatant was removed, and the resulting solid particles were washed several times with deionized water and ethanol, respectively. Then, the particles were placed in a vacuum oven and dried at 60℃ before being collected for later use.

[0078] (2) Dissolve 0.316g of potassium permanganate in 60mL of deionized water and stir until completely dissolved. This solution is labeled A. Dissolve 0.507g of manganese sulfate monohydrate and 1.124g of cobalt sulfate heptahydrate in 60mL of deionized water. This solution is labeled B. Stir until completely dissolved. Dissolve 0.385g of iron tetroxide nanoparticles from step (1) in solution B (mass fraction 0.64%) and stir until homogeneous. Then, slowly add solution A at a volume ratio of 1:1 while stirring until homogeneous to form solution C. Stir for another 30 minutes.

[0079] (3) Transfer the C solution from (2) above to a reaction vessel and react at 100°C for 6 h. Then, wash the obtained solid particles several times with deionized water to remove undesirable soluble ions, wash, centrifuge, and dry the precipitate at 80°C for 24 h to obtain Fe3O4@Co-Doped MnO2 nano-hybrid material.

[0080] Comparative Example 5:

[0081] (1) In a beaker, the reactants ferric chloride hexahydrate, sodium citrate, and urea were dissolved in deionized water at a mass-to-volume ratio of 5g:11.6g:3.4g:200mL. After stirring until completely dissolved, the mixture was transferred to a reaction vessel and reacted at 240℃ for 12h. After the reaction, the product was magnetically separated using a magnet. The supernatant was removed, and the resulting solid particles were washed several times with deionized water and ethanol, respectively. Then, the particles were placed in a vacuum oven and dried at 60℃ before being collected for later use.

[0082] (2) Dissolve 0.237g of potassium permanganate in 60mL of deionized water and stir until completely dissolved. This solution is labeled A. Dissolve 0.507g of manganese sulfate monohydrate and 1.405g of cobalt sulfate heptahydrate in 60mL of deionized water. This solution is labeled B. Stir until completely dissolved. Dissolve 0.385g of the iron(III) oxide nanoparticles from (1) in solution B (mass fraction 0.64%) and stir until homogeneous. Then, slowly add solution A at a volume ratio of 1:1 while stirring until homogeneous to form solution C. Stir for another 30 minutes.

[0083] (3) Transfer the C solution from (2) above to a reaction vessel and react at 100°C for 6 h. Then, wash the obtained solid particles several times with deionized water to remove undesirable soluble ions, wash, centrifuge, and dry the precipitate at 80°C for 24 h to obtain Fe3O4@Co-Doped MnO2 nano-hybrid material.

[0084] Comparative Example 6:

[0085] (1) In a beaker, the reactants ferric chloride hexahydrate, sodium citrate, and urea were dissolved in deionized water at a mass-to-volume ratio of 3g:7g:2g:200mL. After stirring until completely dissolved, the yellow solution was transferred to a reaction vessel and reacted at 200℃ for 12h. After the reaction was completed, the product was magnetically separated, the supernatant was removed, and the resulting solid particles were washed several times with deionized water and ethanol, respectively. Then, they were placed in a vacuum oven, dried at 60℃, and collected for later use.

[0086] (2) Dissolve 0.845g of manganese sulfate monohydrate and 2.81g of cobalt sulfate heptahydrate in 60mL of deionized water, and label this solution as solution B or mixed solution I. Stir until completely dissolved. Dissolve 0.385g of iron oxide nanoparticles from step (1) in solution B, based on a mass fraction of 0.64%, and stir until homogeneous to obtain mixed solution II. Then, slowly add 60mL of deionized water to mixed solution II at a volume ratio of 1:1, stirring constantly to form solution C or mixed solution III. Stir for another 30min.

[0087] (3) Transfer the C solution from (2) above to a reaction vessel and react at 100°C for 6 h. Then, wash the obtained product several times with distilled water to remove undesirable soluble ions, wash, centrifuge, and dry the precipitate at 80°C for 24 h to obtain Fe3O4@Co-Doped MnO2 nano-hybrid material.

[0088] Comparative Example 7:

[0089] (1) In a beaker, the reactants ferric chloride hexahydrate, sodium citrate, and urea were dissolved in deionized water at a mass-to-volume ratio of 3g:7g:2g:200mL. After stirring until completely dissolved, the yellow solution was transferred to a reaction vessel and reacted at 200℃ for 12h. After the reaction was completed, the product was magnetically separated, the supernatant was removed, and the resulting solid particles were washed several times with deionized water and ethanol, respectively. Then, they were placed in a vacuum oven, dried at 60℃, and collected for later use.

[0090] (2) Dissolve 0.316g of potassium permanganate in 60mL of deionized water and stir until completely dissolved. This solution is labeled as solution A or potassium permanganate solution. Dissolve 0.507g of manganese sulfate monohydrate and 2.81g of cobalt sulfate heptahydrate in 60mL of deionized water. This solution is labeled as solution B or mixed solution I. Stir until completely dissolved. Dissolve 0.385g of iron oxide nanoparticles from step (1) in solution B, with a mass fraction of 0.64%. Stir until mixed solution II is obtained. Then, slowly add solution A to mixed solution II at a volume ratio of 1:1 while stirring until homogeneous to form solution C or mixed solution III. Stir for another 30 minutes.

[0091] (3) Transfer the C solution from (2) above to a reaction vessel and react at 220°C for 6 h. Then, wash the obtained product several times with distilled water to remove undesirable soluble ions, wash, centrifuge, and dry the precipitate at 80°C for 24 h to obtain Fe3O4@Co-Doped MnO2 nano-hybrid material.

[0092] Test example:

[0093] The materials prepared in Examples 1-6 and Comparative Examples 1-7 were mixed evenly with paraffin wax and pressed into ring-shaped samples with a thickness of 2 mm or 3 mm for performance testing. Examples 1-3 and Comparative Examples 1-3 were pressed into samples with a thickness of 2 mm, while Examples 4-6 and Comparative Examples 4-7 were pressed into samples with a thickness of 3 mm.

[0094] The absorption performance of the rings prepared from the materials described in Examples 1-6 and Comparative Examples 1-7 was tested using the coaxial method. The test results are shown in Table 1 below. The coaxial method reflects the absorption performance of a material by measuring the power of the electromagnetic wave returning after passing through it. The electromagnetic parameters of the material were measured, and then the electromagnetic wave absorption performance and impedance matching characteristics of the sample were calculated using software.

[0095] Table 1 shows the microwave absorption performance test results of the coaxial ring samples in Examples 1-6 and Comparative Examples 1-7.

[0096]

[0097] Table 1 shows that by adjusting the cobalt ion doping amount, manganese dioxide content, and temperature, manganese dioxide with different morphologies can be obtained. Similarly, by adjusting the Fe3O4 particle size, Fe3O4@Co-Doped MnO2 nano-hybrid microwave absorbers with different absorption properties can be obtained. Compared to pure iron tetroxide nanoparticles, the Fe3O4@Co-Doped MnO2 nano-hybrid microwave absorber exhibits superior microwave absorption performance, which stems from the synergistic effect of doping, the unique core-shell structure, and multiple loss mechanisms.

[0098] Furthermore, comparing Example 1 with Comparative Examples 3 and 4 reveals that the cobalt doping concentration affects the effective bandwidth and minimum reflection loss. With increasing cobalt doping concentration, the effective bandwidth (EAB) increased by 2.79 GHz, while the minimum reflection loss decreased by -14.5 dB, and the thickness decreased. Increasing the cobalt doping concentration also affects the crystal structure of manganese dioxide. 2+ Excessive conversion of α-MnO2 to δ-MnO2 can affect microwave absorption performance.

[0099] Comparative Examples 1 and 2 show that by changing the particle size of iron oxide in step 1, the particle size of iron oxide in Comparative Example 2 was slightly increased, which had a good effect on the microwave absorption performance and improved its microwave absorption performance by 11%.

[0100] By comparing Example 4 and Comparative Example 5, it can be seen that the content of manganese dioxide affects the minimum reflection loss and the effective bandwidth. As the content of manganese dioxide increases, the minimum reflection loss decreases from -29.8dB to -47.8dB, the absorption intensity increases, and the effective bandwidth (EAB) more than doubles, effectively improving the absorption performance.

[0101] By comparing Examples 1, 2, and 3 with Comparative Example 4, it can be seen that when the ratios of Fe, Mn, and Co are different, the minimum reflection loss, effective absorption bandwidth, and thickness of the Fe3O4@Co-Doped MnO2 nanohybrid material will be different, which will have a significant impact on the microwave absorption performance.

[0102] In Comparative Example 6, no potassium permanganate was added. The particles prepared at this time were almost still Fe3O4. Manganese sulfate monohydrate and cobalt sulfate heptahydrate did not react, nor did they react with Fe3O4. There may be ions on the Fe3O4 surface that have not been completely removed, which has little effect on its microwave absorption performance and is similar to that of Comparative Example 1.

[0103] In Comparative Example 7, when the temperature of the high-temperature reaction was outside the defined range, the morphology of the manganese dioxide produced changed and was not entirely the same as that of manganese dioxide in Example 1. The absorption performance of Comparative Example 7 was lower than that of Example 1, possibly because the high temperature caused changes in its morphological structure, resulting in an impedance matching distance far from 1.

[0104] In summary, the Fe3O4@Co-Doped MnO2 nanohybrid material possesses multiple types of wave absorption and attenuation mechanisms, is prone to polarization at the interface, and its components can exert a synergistic effect of various electromagnetic wave loss mechanisms such as electromagnetic loss. By adjusting the complex permittivity and permeability of the material itself, the impedance matching is optimized, and its electromagnetic loss and wave absorption performance are improved, effectively meeting the requirements of "thin, light, wide, and strong".

[0105] The above description is merely a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations that are directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included within the protection scope of the present invention.

Claims

1. A metal ion-doped magnetic-dielectric synergistic core-shell structure microwave absorbing material, characterized in that, The core layer of the absorbing material is an iron-based material, and the shell layer is a metal ion-doped manganese dioxide layer covering the surface of the core layer. In the microwave absorbing material, the mass ratio of the core layer to the shell layer is 1:1 to 2.5; In the shell, the molar ratio of metal ions to manganese ions is 1~2:1~2; The microwave absorbing material is spiky in shape; The iron-based material is iron(II,III) oxide; The metal ion includes one or more of cobalt ions, nickel ions, and copper ions, denoted as M.

2. A method for preparing the metal ion-doped magnetic-dielectric synergistic core-shell structure microwave absorbing material according to claim 1, characterized in that, The preparation method includes the following steps: S1: Preparation of iron oxide nanoparticles; S2: Dissolve potassium permanganate in water to obtain potassium permanganate solution; mix manganese sulfate monohydrate and metal salt and dissolve in water to obtain mixed solution I; S3: Add the iron oxide nanoparticles prepared in step S1 to the mixed solution I in step S2, stir evenly to obtain mixed solution II, and add potassium permanganate solution while stirring to obtain mixed solution III; S4: Transfer the mixed solution Ⅲ to the reactor, react at high temperature, wash, centrifuge, and dry the precipitate to obtain Fe3O4@M-Doped MnO2 nano-hybrid material, namely, metal ion doped magnetic media synergistic core-shell structure microwave absorbing material; In step S4, the high-temperature reaction temperature is 100~180℃ and the time is 6~12h.

3. The preparation method according to claim 2, characterized in that, In step S1, the preparation method of the iron oxide nanoparticles is as follows: Ferric chloride hexahydrate, sodium citrate, and urea were dissolved in water to obtain a mixed solution, which was placed in a reaction vessel. After the reaction, the product was magnetically separated, the supernatant was removed, and the resulting solid particles were washed and dried at 60-80°C to obtain iron oxide nanoparticles.

4. The preparation method according to claim 3, characterized in that, The mass-to-volume ratio of ferric chloride hexahydrate, sodium citrate, urea, and water is 3-5 g: 7-11.6 g: 2-3.4 g: 200 mL; the reaction temperature is 200-240 °C, and the reaction time is 12-18 h.

5. The preparation method according to claim 2, characterized in that, The particle size of the iron oxide nanoparticles is 20~60nm.

6. The preparation method according to claim 2, characterized in that, In step S2, the molar volume ratio of potassium permanganate to water in the potassium permanganate solution is 2-4 mmol: 60 mL; the molar volume ratio of manganese sulfate monohydrate, metal salt, and water in the mixed solution I is 2.9-6 mmol: 5-10 mmol: 60 mL; the metal salt includes one or more of cobalt sulfate heptahydrate, nickel sulfate, and copper sulfate.

7. The preparation method according to claim 2, characterized in that, In step S3, the mass fraction of iron oxide nanoparticles in the mixed solution II is 0.64%; the volume ratio of the mixed solution II to the potassium permanganate solution is 1~2:

1.

8. The preparation method according to claim 2, characterized in that, In step S4, the drying temperature is 60~80℃ and the time is 18~24h.

9. A metal ion-doped magnetic-dielectric synergistic core-shell structure absorbing material as described in claim 1 for electromagnetic wave absorption.

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