A Y2O3@SiO2@PPy@MnO2 wave-absorbing composite material with a multi-layer core-shell heterogeneous ice-like frost structure and a preparation method thereof

Abstract

The application discloses a kind of multi-layer core-shell hetero ice-snow structure Y2O3@SiO2@PPy@MnO2 wave-absorbing composite material and preparation method thereof.The wave-absorbing composite material described in the application is composed of multi-layer core-shell microspheres and nanorods, and presents ice-snow structure;The multi-layer core-shell microspheres are Y2O3 as core material, and are coated with SiO2 layer and PPy layer in turn;The nanorod is MnO2.The application uses yttrium oxide as core material, uniformly coats SiO2 on its surface by Stober method, forms single-layer core-shell structure.After that, C and N elements are introduced, and a layer of PPy is coated on its surface again to form "frost branch" Y2O3@SiO2@PPy, and rod-shaped MnO2 is used as "frost branch", which strengthens interface polarization effect, constructs conductive network, and effectively improves the overall electromagnetic wave absorption efficiency.The wave-absorbing composite material solves the problem of insufficient attenuation ability of single component and narrow effective absorption bandwidth, and presents strong dielectric polarization ability.The preparation method of the application is simple, the production cost is low, and is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing materials technology, specifically to the design of a multi-layered core-shell heterogeneous frost-like Y2O3@SiO2@PPy@MnO2 microwave absorbing composite material and its preparation method. Background Technology

[0002] Currently, significant progress has been made in the research of microwave absorbing materials, with continuous improvement in technology. These materials achieve microwave absorption through mechanisms such as magnetic loss and dielectric loss. Specifically, addressing the problems of high density, narrow absorption bandwidth, and limited application range of traditional absorbing materials, the development of low-cost, lightweight, ultra-thin, high-performance, and broadband absorbing materials has become a current research hotspot.

[0003] Commonly used microwave absorbing materials include dielectric loss materials such as carbon materials, MnO2, and PPy, as well as magnetic loss materials such as magnetic metals. However, magnetic materials suffer from high density and narrow effective bandwidth, which limits their application range.

[0004] Y2O3 is an important rare earth oxide. Its unique 4f electronic structure endows it with tunable physical properties, making it suitable for manufacturing magnetic materials for microwave applications and important materials for military use. However, it cannot meet the needs of high-performance absorbing materials on its own.

[0005] SiO2 is a transmissive wave material that increases the reflection path of electromagnetic waves within the material. However, the absorption performance of SiO2 itself may be relatively limited, usually requiring combination with other absorbing materials or modification to achieve better absorption. For example, patent number CN202110516544.3 discloses a method for preparing an α-Fe2O3-doped silica nanoparticle absorbing material, but the composite material prepared by this method has not yet met the -10dB standard.

[0006] Polypyrrole (PPy) possesses a certain degree of conductivity and can generate conductive losses through interaction with electromagnetic fields, converting electromagnetic wave energy into other forms of energy such as heat. To improve the microwave absorption performance of polypyrrole-based composites, one research direction is to combine polypyrrole with other dielectric loss materials or magnetic materials. For example, patent number CN 113845880A discloses a silver nanowire@polypyrrole-ferric oxide composite microwave absorbing material and its preparation method. However, the silver nitrate used is expensive, and the composite material has a wide effective absorption bandwidth and a thick thickness, which is very unfavorable for subsequent use.

[0007] Therefore, it is of great significance to overcome the shortcomings of high density, poor absorption performance, simple loss mechanism and poor matching performance, and to prepare a new microwave absorbing material with low density, high absorption performance and effective absorption bandwidth. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a microwave absorbing composite material with a multilayered core-shell heterogeneous frost-like structure, Y2O3@SiO2@PPy@MnO2, and its preparation method. The microwave absorbing composite material prepared by this invention exhibits excellent microwave absorption performance, and the preparation method is simple and low-cost, solving the problems of poor absorption performance and limited microwave absorption frequency bands in existing microwave absorbing materials.

[0009] The technical solution of the present invention is as follows:

[0010] A microwave absorbing composite material with a multi-layered core-shell heterogeneous frost-like structure, namely Y2O3@SiO2@PPy@MnO2, is composed of multi-layered core-shell microspheres and nanorods, exhibiting a frost-like structure. The multi-layered core-shell microspheres are made of Y2O3 as the core material, sequentially coated with SiO2 layers and PPy layers. The nanorods are made of MnO2.

[0011] Furthermore, the particle size of the Y2O3 is 50-200 nm.

[0012] Furthermore, the mass ratio of Y2O3 to SiO2 is 1:1.

[0013] Furthermore, the mass ratio of Y2O3 to PPy is 7.14:1.

[0014] Furthermore, the mass ratio of Y2O3 to MnO2 is 1:3.93 to 4.07.

[0015] A method for preparing the aforementioned microwave absorbing composite material, the method comprising the following steps:

[0016] (1) Preparation of monolayer core-shell microspheres Y2O3@SiO2: Y2O3 was dispersed in a solvent at room temperature, and then TEOS was added. The monolayer core-shell microspheres Y2O3@SiO2 coated with SiO2 were prepared by the Stober method.

[0017] (2) Preparation of multilayer core-shell microspheres Y2O3@SiO2@PPy: The single-layer core-shell microspheres Y2O3@SiO2 obtained in step (1) were dispersed in deionized water, FeCl3·6H2O was added, and after mixing evenly, pyrrole monomer was added and reacted at room temperature. After treatment, multilayer core-shell microspheres Y2O3@SiO2@PPy were obtained.

[0018] (3) Preparation of Y2O3@SiO2@PPy@MnO2 microwave absorbing composite material: The multilayer core-shell microspheres Y2O3@SiO2@PPy obtained in step (2) are dispersed in deionized water, then KMnO4 is added, hydrochloric acid is added dropwise while stirring, ultrasonication is performed, and the mixture is transferred to a reaction vessel for reaction. Finally, the mixture is cooled, filtered, the filter residue is collected, washed, and dried to obtain the Y2O3@SiO2@PPy@MnO2 microwave absorbing composite material.

[0019] Further, in step (1), the solvent is an aqueous solution of ethanol with a volume fraction of 75%; the concentration of Y2O3 in the solvent is 0.11 mol / L, the concentration of TEOS in the solvent is 0.42 mol / L, and the reaction time is 4 h.

[0020] Further, in step (2), the concentration of Y2O3@SiO2 in deionized water is 0.07 mol / L; the concentration of FeCl3·6H2O in deionized water is 0.07-0.08 mol / L; the concentration of pyrrole monomer in deionized water is 0.165 mol / L; the reaction temperature is -2 to 0℃, and the reaction time is 4 h.

[0021] Further, in step (3), the concentration of Y2O3@SiO2@PPy in deionized water is 0.01 mol / L; the concentration of KMnO4 in deionized water is 0.083 mol / L; the mass percentage concentration of hydrochloric acid is 36-38%; the volume ratio of hydrochloric acid to deionized water is 1:80 mL; the reaction temperature is 180℃; and the reaction time is 5-7 h.

[0022] The beneficial technical effects of this invention are as follows:

[0023] This invention designs a multilayer core-shell frost-like microwave absorbing composite material. The composite material prepared in this invention uses multilayer core-shell microspheres Y2O3@SiO2@PPy as "frost branches," specifically, Y2O3 as the core material, SiO2 as the middle layer, and conductive polymer PPy as the outermost core-shell layer. SiO2 is a transmissive wave material, increasing the reflection path of electromagnetic waves within the material; PPy effectively promotes eddy current effects and enhances eddy current loss. MnO2, acting as "frost branches," significantly increases its specific surface area, increasing the propagation path and scattering frequency of electromagnetic waves within the material. Compared with existing technologies, such as the NiCo2O4@PPy composite material disclosed in patent number CN 117560915 A and the MnO2 / Ti3C2 MXene composite material in patent number CN 117641872 A, the microwave absorption performance of Y2O3@SiO2@PPy in this invention is superior.

[0024] The microwave absorbing composite material of this invention uses a three-layer core-shell structure of Y2O3@SiO2@PPy as "frost branches," which not only greatly increases the number of interfaces and enhances the interfacial polarization effect, but also effectively suppresses the reflection, scattering, and transmission of electromagnetic waves by adjusting the amount of each raw material, thereby significantly improving the microwave absorption efficiency of the material. Meanwhile, the outer rod-shaped MnO2 acts as "frost branches," with the rods and the core-shell structure together constructing a complex conductive network, enhancing conductive loss and effectively improving the overall electromagnetic wave absorption efficiency. Attached Figure Description

[0025] Figure 1 The images show the FT-IR spectra of the microwave absorbing composite materials prepared in Examples 1-5, Comparative Examples 1-4, and Comparative Example 5.

[0026] In the figures: (a) are FT-IR images of the microwave absorbing composite materials prepared in Example 1, Comparative Examples 1-2 and Comparative Example 5; (b) are FT-IR images of the microwave absorbing composite materials prepared in Example 1-2, Comparative Examples 3-4 and Comparative Example 5; (c) are FT-IR images of the microwave absorbing composite materials prepared in Example 2 and Example 3-5.

[0027] Figure 2 The images show the XRD patterns of the microwave absorbing composite materials prepared in Examples 1-5, Comparative Examples 1-4, and Comparative Example 5.

[0028] In the figures: (a) are the XRD patterns of the microwave absorbing composite materials prepared in Example 1, Comparative Examples 1-2 and Comparative Example 5; (b) are the XRD patterns of the microwave absorbing composite materials prepared in Example 2, Comparative Examples 3-4 and Comparative Example 5; (c) are the XRD patterns of the microwave absorbing composite materials prepared in Examples 3-5 and Comparative Example 5.

[0029] Figure 3 The images show SEM images of the microwave absorbing composite materials prepared in Examples 1-5, Comparative Examples 1-4, and Comparative Example 5.

[0030] In the figures: (a) is the SEM image of the microwave absorbing material of Comparative Example 5 at 500 nm; (b) is the SEM image of the microwave absorbing composite material of Comparative Example 1 at 500 nm; (c) is the SEM image of the microwave absorbing composite material of Example 1 at 500 nm; (d) is the SEM image of the microwave absorbing composite material of Comparative Example 2 at 500 nm; (e) is the SEM image of the microwave absorbing composite material of Comparative Example 3 at 1 μm; (f) is the SEM image of the microwave absorbing composite material of Example 2 at 1 μm; (g) is the SEM image of the microwave absorbing composite material of Comparative Example 4 at 1 μm; (h) is the SEM image of the microwave absorbing composite material of Example 3 at 2 μm; (i) is the SEM image of the microwave absorbing composite material of Example 4 at 2 μm; (j) is the SEM image of the microwave absorbing composite material of Example 5 at 2 μm.

[0031] Figure 4 The electromagnetic parameters ε', ε" and tanδ of the microwave absorbing composite materials prepared in Examples 1-5, Comparative Examples 1-4, and Comparative Example 5 are given. ε Atlas.

[0032] In the figure: (a) is the spectrum of electromagnetic parameter ε'; (b) is the spectrum of electromagnetic parameter ε"; (c) is the spectrum of tanδ. ε Atlas.

[0033] Figure 5 The attenuation coefficient curves are shown for the microwave absorbing composite materials prepared in Examples 1-5, Comparative Examples 1-4, and Comparative Example 5.

[0034] Figure 6 The 3D reflection loss of the microwave absorbing composite materials prepared in Examples 1-5 and Comparative Examples 1-4 of the present invention and the microwave absorbing material in Comparative Example 5 at different thicknesses are shown.

[0035] In the figures: (a) 3D reflection loss of Comparative Example 5 absorbing material at different thicknesses; (b) 3D reflection loss of Comparative Example 1 absorbing composite material at different thicknesses; (c) 3D reflection loss of Example 1 absorbing composite material at different thicknesses; (d) 3D reflection loss of Comparative Example 2 absorbing composite material at different thicknesses; (e) 3D reflection loss of Comparative Example 3 absorbing composite material at different thicknesses; (f) 3D reflection loss of Example 2 absorbing composite material at different thicknesses; (g) 3D reflection loss of Comparative Example 4 absorbing composite material at different thicknesses; (h) 3D reflection loss of Example 3 absorbing composite material at different thicknesses; (i) 3D reflection loss of Example 4 absorbing composite material at different thicknesses; (j) 3D reflection loss of Example 5 absorbing composite material at different thicknesses.

[0036] Figure 7 The 2D reflection loss of the microwave absorbing composite materials prepared in Examples 1-5 and Comparative Examples 1-4 of the present invention and the microwave absorbing material of Comparative Example 5 at different thicknesses are shown.

[0037] In the figures: (a) is the 2D reflection loss of the absorbing material of Comparative Example 5 at different thicknesses; (b) is the 2D reflection loss of the absorbing composite material of Comparative Example 1 at different thicknesses; (c) is the 2D reflection loss of the absorbing composite material of Example 1 at different thicknesses; (d) is the 2D reflection loss of the absorbing composite material of Comparative Example 2 at different thicknesses; (e) is the 2D reflection loss of the absorbing composite material of Comparative Example 3 at different thicknesses; (f) is the 2D reflection loss of the absorbing composite material of Example 2 at different thicknesses; (g) is the 2D reflection loss of the absorbing composite material of Comparative Example 4 at different thicknesses; (h) is the 2D reflection loss of the absorbing composite material of Example 3 at different thicknesses; (i) is the 2D reflection loss of the absorbing composite material of Example 4 at different thicknesses; and (j) is the 2D reflection loss of the absorbing composite material of Example 5 at different thicknesses.

[0038] Figure 8 The images show the Cole-Cole diagrams of the microwave absorbing composite materials prepared in Examples 1-5, Comparative Examples 1-4, and Comparative Example 5.

[0039] In the figures: (a) is the Cole-Cole diagram of the microwave absorbing material of Comparative Example 5; (b) is the Cole-Cole diagram of the microwave absorbing composite material of Comparative Example 1; (c) is the Cole-Cole diagram of the microwave absorbing composite material of Example 1; (d) is the Cole-Cole diagram of the microwave absorbing composite material of Comparative Example 2; (e) is the Cole-Cole diagram of the microwave absorbing composite material of Comparative Example 3; (f) is the Cole-Cole diagram of the microwave absorbing composite material of Example 2; (g) is the Cole-Cole diagram of the microwave absorbing composite material of Comparative Example 4; (h) is the Cole-Cole diagram of the microwave absorbing composite material of Example 3; (i) is the Cole-Cole diagram of the microwave absorbing composite material of Example 4; (j) is the Cole-Cole diagram of the microwave absorbing composite material of Example 5. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0041] The yttrium oxide particles used in the following examples / comparative examples of the present invention have a particle size of 100 nm and were purchased from Zhejiang Manli Nanotechnology Co., Ltd.

[0042] Example 1

[0043] A single-layer core-shell microsphere Y2O3@SiO2 microwave absorbing composite material is prepared by the following method:

[0044] Y₂O₃ (4 g, 0.018 mol) was dispersed in 160 mL of a 75% ethanol solution at room temperature. 乙醇 V 水 =3:1), ultrasonically treated for 30 min, then 0.067 mol of TEOS (i.e., TEOS concentration of 0.42 mol / L) was added dropwise. Then, 16 mL of 25% ammonia solution was added dropwise at 240 rpm. The reaction was carried out using the Stober method for 4 h to prepare single-layer core-shell microspheres Y2O3@SiO2 coated with Y2O3. After washing with deionized water and ethanol, the microspheres were centrifuged at 10000 rpm for 5 min, the supernatant was discarded, and the centrifugation process was repeated multiple times. The residue was then collected by filtration and dried at 80℃ for 12 h to obtain pure single-layer core-shell microspheres Y2O3@SiO2 (the mass ratio of Y2O3 to SiO2 was determined to be 1:1), named YS B YS B Mix it evenly with solid paraffin at a mass ratio of 3:7, and then press it into a sample with an outer diameter of 7.00 mm, an inner diameter of 3.04 mm, and a thickness of about 2 mm using a special ring pressing mold for subsequent performance testing.

[0045] Example 2

[0046] A multi-layered core-shell structure Y2O3@SiO2@PPy microwave absorbing composite material is prepared by the following method:

[0047] (1) Preparation of monolayer core-shell microspheres Y2O3@SiO2: The preparation method in Example 1 was followed to obtain pure monolayer core-shell microspheres Y2O3@SiO2, which were named YS B .

[0048] (2) Preparation of multilayer core-shell microspheres Y2O3@SiO2@PPy: 0.014 mol of the single-layer core-shell microspheres Y2O3@SiO2 obtained in step (1) was dispersed in 200 mL of deionized water. 0.015 mol of FeCl3·6H2O was added and mixed evenly. 0.033 mol of pyrrole monomer was slowly added at 240 rpm and 0 °C for 4 h. After washing with deionized water and ethanol, the mixture was centrifuged at 8000 rpm for 10 min, and the supernatant was discarded. The centrifugation operation was repeated several times. The filter residue was collected by filtration and dried at 80 °C for 8 h to obtain multilayer core-shell microspheres Y2O3@SiO2@PPy (the mass ratio of Y2O3 to PPy was measured to be 7.14:1), named YS B P B YS B P BMix it evenly with solid paraffin at a mass ratio of 3:7, and then press it into a sample with an outer diameter of 7.00 mm, an inner diameter of 3.04 mm, and a thickness of about 2 mm using a special ring pressing mold for subsequent performance testing.

[0049] Example 3

[0050] A microwave absorbing composite material with a multilayered core-shell heterogeneous frost-like structure, Y2O3@SiO2@PPy@MnO2, is prepared by the following method:

[0051] (1) Preparation of monolayer core-shell microspheres Y2O3@SiO2: The preparation method in Example 1 was followed to obtain pure monolayer core-shell microspheres Y2O3@SiO2, which were named YS B .

[0052] (2) Preparation of multilayer core-shell microspheres Y2O3@SiO2@PPy: The preparation was carried out according to the preparation method in step (2) of Example 2 to obtain multilayer core-shell microspheres Y2O3@SiO2@PPy, named YS B P B .

[0053] (3) Take 0.0011 mol of the multilayer core-shell microspheres Y2O3@SiO2@PPy obtained in step (2) and disperse them in 120 mL of deionized water. Then add 0.01 mol of KMnO4 and dropwise add 1.5 mL of 36%–38% hydrochloric acid at 300 rpm. Sonicate for 15 min and then transfer to a stainless steel reactor lined with Teflon. React at 180℃ for 5 h. Finally, cool, filter, collect the filter residue, wash, and dry at 80℃ for 12 h to obtain the Y2O3@SiO2@PPy@MnO2 microwave absorbing composite material (the mass ratio of Y2O3 to MnO2 was measured to be 1:3.93). Name it YS B P B M A YS B P B M A Mix it evenly with solid paraffin at a mass ratio of 3:7, and then press it into a sample with an outer diameter of 7.00 mm, an inner diameter of 3.04 mm, and a thickness of about 2 mm using a special ring pressing mold for subsequent performance testing.

[0054] Example 4

[0055] A microwave absorbing composite material with a multilayered core-shell heterogeneous frost-like structure, Y2O3@SiO2@PPy@MnO2, is prepared by the following method:

[0056] (1) Preparation of monolayer core-shell microspheres Y2O3@SiO2: The preparation method in Example 1 was followed to obtain pure monolayer core-shell microspheres Y2O3@SiO2, which were named YSB .

[0057] (2) Preparation of multilayer core-shell microspheres Y2O3@SiO2@PPy: The preparation was carried out according to the preparation method in step (2) of Example 2 to obtain multilayer core-shell microspheres Y2O3@SiO2@PPy, named YS B P B .

[0058] (3) Take 0.0011 mol of the multilayer core-shell microspheres Y2O3@SiO2@PPy obtained in step (2) and disperse them in 120 mL of deionized water. Then add 0.01 mol of KMnO4 and dropwise add 1.5 mL of 36%–38% hydrochloric acid at 300 rpm. Sonicate for 15 min and then transfer to a stainless steel reactor lined with Teflon. React at 180℃ for 6 h. Finally, cool, filter, collect the filter residue, wash, and dry at 80℃ for 12 h to obtain the Y2O3@SiO2@PPy@MnO2 microwave absorbing composite material (the mass ratio of Y2O3 to MnO2 was measured to be 1:4.02). Name it YS B P B M B YS B P B M B Mix it evenly with solid paraffin at a mass ratio of 3:7, and then press it into a sample with an outer diameter of 7.00 mm, an inner diameter of 3.04 mm, and a thickness of about 2 mm using a special ring pressing mold for subsequent performance testing.

[0059] Example 5

[0060] A microwave absorbing composite material with a multilayered core-shell heterogeneous frost-like structure, Y2O3@SiO2@PPy@MnO2, is prepared by the following method:

[0061] (1) Preparation of monolayer core-shell microspheres Y2O3@SiO2: The preparation method in Example 1 was followed to obtain pure monolayer core-shell microspheres Y2O3@SiO2, which were named YS B .

[0062] (2) Preparation of multilayer core-shell microspheres Y2O3@SiO2@PPy: The preparation was carried out according to the preparation method in step (2) of Example 2 to obtain multilayer core-shell microspheres Y2O3@SiO2@PPy, named YS B P B .

[0063] (3) Take 0.0011 mol of the multilayer core-shell microspheres Y2O3@SiO2@PPy obtained in step (2) and disperse them in 120 mL of deionized water. Then add 0.01 mol of KMnO4 and dropwise add 1.5 mL of 36%–38% hydrochloric acid at 300 rpm. Sonicate for 15 min and then transfer to a stainless steel reactor lined with Teflon. React at 180℃ for 7 h. Finally, cool, filter, collect the filter residue, wash, and dry at 80℃ for 12 h to obtain the Y2O3@SiO2@PPy@MnO2 microwave absorbing composite material (the mass ratio of Y2O3 to MnO2 was measured to be 1:4.07). Name it YS B P B M C YS B P B M C Mix it evenly with solid paraffin at a mass ratio of 3:7, and then press it into a sample with an outer diameter of 7.00 mm, an inner diameter of 3.04 mm, and a thickness of about 2 mm using a special ring pressing mold for subsequent performance testing.

[0064] Comparative Example 1

[0065] A single-layer core-shell microsphere Y2O3@SiO2 microwave absorbing composite material is prepared by the following method:

[0066] Y₂O₃ (4 g, 0.018 mol) was dispersed in 160 mL of a 75% ethanol solution at room temperature. 乙醇 V 水 =3:1), ultrasonically treated for 30 min, then 0.034 mol of TEOS (i.e., TEOS concentration of 0.21 mol / L) was added dropwise. Then, 8 mL of 25% ammonia solution was added dropwise at 240 rpm. The reaction was carried out using the Stober method for 4 h to prepare single-layer core-shell microspheres Y2O3@SiO2 coated with Y2O3. After washing with deionized water and ethanol, the microspheres were centrifuged at 10000 rpm for 5 min, the supernatant was discarded, and the centrifugation process was repeated multiple times. The residue was then collected by filtration and dried at 80℃ for 12 h to obtain pure single-layer core-shell microspheres Y2O3@SiO2 (the mass ratio of Y2O3 to SiO2 was determined to be 2:1), named YS A YS A Mix it evenly with solid paraffin at a mass ratio of 3:7, and then press it into a sample with an outer diameter of 7.00 mm, an inner diameter of 3.04 mm, and a thickness of about 2 mm using a special ring pressing mold for subsequent performance testing.

[0067] Comparative Example 2

[0068] A single-layer core-shell microsphere Y2O3@SiO2 microwave absorbing composite material is prepared by the following method:

[0069] Y₂O₃ (4 g, 0.018 mol) was dispersed in 160 mL of a 75% ethanol solution at room temperature. 乙醇 V 水 =3:1), ultrasonically treated for 30 min, then 0.10 mol of TEOS (i.e., TEOS concentration of 0.63 mol / L) was added dropwise. Then, 24 mL of 25% ammonia solution was added dropwise at 240 rpm. The reaction was carried out using the Stober method for 4 h to prepare single-layer core-shell microspheres Y2O3@SiO2 coated with Y2O3. After washing with deionized water and ethanol, the microspheres were centrifuged at 10000 rpm for 5 min, the supernatant was discarded, and the centrifugation process was repeated multiple times. The residue was then collected by filtration and dried at 80℃ for 12 h to obtain pure single-layer core-shell microspheres Y2O3@SiO2 (the mass ratio of Y2O3 to SiO2 was determined to be 1:2), named YS C YS C Mix it evenly with solid paraffin at a mass ratio of 3:7, and then press it into a sample with an outer diameter of 7.00 mm, an inner diameter of 3.04 mm, and a thickness of about 2 mm using a special ring pressing mold for subsequent performance testing.

[0070] Comparative Example 3

[0071] A multi-layered core-shell structure Y2O3@SiO2@PPy microwave absorbing composite material is prepared by the following method:

[0072] (1) Preparation of monolayer core-shell microspheres Y2O3@SiO2: The preparation method in Example 1 was followed to obtain pure monolayer core-shell microspheres Y2O3@SiO2, which were named YS B .

[0073] (2) Preparation of multilayer core-shell microspheres Y2O3@SiO2@PPy: 0.014 mol of the single-layer core-shell microspheres Y2O3@SiO2 obtained in step (1) was dispersed in 200 mL of deionized water. 0.015 mol of FeCl3·6H2O was added and mixed evenly. 0.017 mol of pyrrole monomer was slowly added at 240 rpm and 0℃ for 4 h. After washing with deionized water and ethanol, the mixture was centrifuged at 8000 rpm for 10 min, and the supernatant was discarded. The centrifugation operation was repeated several times. The filter residue was collected by filtration and dried at 80℃ for 8 h to obtain multilayer core-shell microspheres Y2O3@SiO2@PPy (the mass ratio of Y2O3 to PPy was measured to be 15.83:1), named YS B P A YS B P AMix it evenly with solid paraffin at a mass ratio of 3:7, and then press it into a sample with an outer diameter of 7.00 mm, an inner diameter of 3.04 mm, and a thickness of about 2 mm using a special ring pressing mold for subsequent performance testing.

[0074] Comparative Example 4

[0075] A multi-layered core-shell structure Y2O3@SiO2@PPy microwave absorbing composite material is prepared by the following method:

[0076] (1) Preparation of monolayer core-shell microspheres Y2O3@SiO2: The preparation method in Example 1 was followed to obtain pure monolayer core-shell microspheres Y2O3@SiO2, which were named YS B .

[0077] (2) Preparation of multilayer core-shell microspheres Y2O3@SiO2@PPy: 0.014 mol of the single-layer core-shell microspheres Y2O3@SiO2 obtained in step (1) was dispersed in 200 mL of deionized water. 0.015 mol of FeCl3·6H2O was added and mixed evenly. 0.051 mol of pyrrole monomer was slowly added at 240 rpm and 0 °C for 4 h. After washing with deionized water and ethanol, the mixture was centrifuged at 8000 rpm for 10 min, the supernatant was discarded, and the centrifugation operation was repeated several times. The filter residue was collected by filtration and dried at 80 °C for 8 h to obtain multilayer core-shell microspheres Y2O3@SiO2@PPy (the mass ratio of Y2O3 to PPy was measured to be 5.72:1), named YS B P B YS B P B Mix it evenly with solid paraffin at a mass ratio of 3:7, and then press it into a sample with an outer diameter of 7.00 mm, an inner diameter of 3.04 mm, and a thickness of about 2 mm using a special ring pressing mold for subsequent performance testing.

[0078] Comparative Example 5

[0079] The microwave absorbing material of Comparative Example 5 is Y2O3 with a particle size of 50-200nm. That is, the microwave absorbing material of this comparative example is Y2O3 that was purchased directly. Y2O3 and solid paraffin were mixed evenly at a mass ratio of 3:7, and then pressed into a sample with an outer diameter of 7.00mm, an inner diameter of 3.04mm, and a thickness of about 2mm using a special ring pressing mold for subsequent performance testing.

[0080] Comparative Example 6

[0081] A microspherical heterogeneous frost-like Y2O3@MnO2 microwave absorbing composite material, the preparation method of which is as follows:

[0082] Y₂O₃ (4 g, 0.018 mol) was dispersed in 120 mL of deionized water at room temperature and sonicated for 10 min. Then, 0.01 mol of KMnO₄ was added, followed by the dropwise addition of 1.5 mL of 36%–38% hydrochloric acid at 300 rpm. The mixture was sonicated for 15 min and then transferred to a Teflon-lined stainless steel reactor. The reactor was reacted at 180 °C for 6 h. Finally, the mixture was cooled, filtered, the residue was collected, washed, and dried at 80 °C for 12 h to obtain the Y₂O₃@MnO₂ microwave absorbing composite material, named YM. B YM B Mix it evenly with solid paraffin at a mass ratio of 3:7, and then press it into a sample with an outer diameter of 7.00 mm, an inner diameter of 3.04 mm, and a thickness of about 2 mm using a special ring pressing mold for subsequent performance testing.

[0083] Comparative Example 7

[0084] A microwave absorbing composite material with a core-shell heterogeneous frost-like structure, Y2O3@SiO2@MnO2, is prepared by the following method:

[0085] (1) Preparation of core-shell microspheres Y2O3@SiO2: The preparation method in Example 1 was followed to obtain pure monolayer core-shell microspheres Y2O3@SiO2, which were named YS B .

[0086] (2) Take 0.0016 mol of the core-shell microspheres Y2O3@SiO2 obtained in step (1) and disperse them in 120 mL of deionized water. Then add 0.01 mol of KMnO4 and dropwise add 1.5 mL of 36%–38% hydrochloric acid at 300 rpm. Sonicate for 15 min and then transfer to a stainless steel reactor lined with Teflon. React at 180℃ for 6 h. Finally, cool, filter, collect the filter residue, wash, and dry at 80℃ for 12 h to obtain the Y2O3@SiO2@MnO2 microwave absorbing composite material, named YS B M B YS B M B Mix it evenly with solid paraffin at a mass ratio of 3:7, and then press it into a sample with an outer diameter of 7.00 mm, an inner diameter of 3.04 mm, and a thickness of about 2 mm using a special ring pressing mold for subsequent performance testing.

[0087] Comparative Example 8

[0088] A microwave absorbing composite material with a multilayered core-shell heterogeneous frost-like structure, Y2O3@SiO2@PPy@MnO2, is prepared by the following method:

[0089] (1) Preparation of monolayer core-shell microspheres Y2O3@SiO2: The preparation method in Example 1 was followed to obtain pure monolayer core-shell microspheres Y2O3@SiO2, which were named YS B .

[0090] (2) Preparation of multilayer core-shell microspheres Y2O3@SiO2@PPy: The preparation was carried out according to the preparation method in step (2) of Example 2 to obtain multilayer core-shell microspheres Y2O3@SiO2@PPy, named YS B P B .

[0091] (3) Take 0.0011 mol of the multilayer core-shell microspheres Y2O3@SiO2@PPy obtained in step (2) and disperse them in 120 mL of deionized water. Then add 0.02 mol of KMnO4 and dropwise add 3.0 mL of 36%–38% hydrochloric acid at 300 rpm. Sonicate for 15 min and then transfer to a stainless steel reactor lined with Teflon. React at 180℃ for 6 h. Finally, cool, filter, collect the filter residue, wash, and dry at 80℃ for 12 h to obtain the Y2O3@SiO2@PPy@MnO2 microwave absorbing composite material (the mass ratio of Y2O3 to MnO2 was measured to be 1:8.04). Name it YS B P B M B -2, YS B P B M B -2 and solid paraffin are mixed evenly at a mass ratio of 3:7, and then pressed into samples with an outer diameter of 7.00 mm, an inner diameter of 3.04 mm, and a thickness of about 2 mm using a special ring pressing mold for subsequent performance testing.

[0092] Test case

[0093] (1) FT-IR characterization of microwave absorbing composite materials

[0094] The microwave absorbing composite materials prepared in Examples 1-5 and Comparative Examples 1-4 of this invention, and the microwave absorbing material in Comparative Example 5, were analyzed using a Nicolet IS10 Fourier Transform Infrared Spectrometer. The results are as follows: Figure 1 As shown.

[0095] from Figure 1 As shown in Figure (a), the peak value of yttrium oxide is 553 cm⁻¹. -1 However, with SiO2 coating, this peak value weakened significantly. Meanwhile, a peak value appeared at 1075 cm⁻¹. -1 and 782cm -1 The new peaks correspond to the asymmetric and symmetric tensile vibrations of the Si-O bond, proving the synthesis and existence of SiO2.

[0096] from Figure 1 As can be seen from the results in Figure (b), the characteristic peak of polypyrrole is clearly displayed: 1557 cm⁻¹. -1 The peak corresponding to the vibration of the pyrrole ring is 1209 cm⁻¹. -1 At this point, the stretching vibration mode of the CN bond is observed, while at 1065 cm⁻¹... -1 and 934cm -1 The characteristic peak is closely related to the out-of-plane vibration of =CH, 795 cm⁻¹ -1 The peaks are attributed to the out-of-plane deformation vibrations of CH; even with changes in the doping conditions of PPy, the aforementioned characteristic peaks did not show significant shifts or disappearances, indicating that polypyrrole in YS B Uniform coating on the surface.

[0097] from Figure 1 As can be seen from the results in Figure (c), YS B P B M A YS B P B M B YS B P B M C The peak values ​​of the existence are all related to YS B P B The peak value of manganese dioxide was not observed, which may be because other peak values ​​were stronger, causing the peak value of manganese dioxide to weaken.

[0098] (2) XRD characterization of microwave absorbing composite materials

[0099] The microwave absorbing composite materials prepared in Examples 1-5 and Comparative Examples 1-4 of this invention, and the microwave absorbing material in Comparative Example 5, were analyzed using a D2 PHASER A26-X1-A2E0B2A0 X-ray diffractometer. The results are as follows: Figure 2 As shown.

[0100] from Figure 2 As can be seen from the results in Figure (a), the obvious diffraction peaks correspond to the crystal planes of Y2O3 (JCPDS NO.41-1105), indicating the high purity and good crystallinity of Y2O3. However, no obvious diffraction peaks belonging to SiO2 were observed in the XRD pattern.

[0101] from Figure 2 As can be seen from Figure (b), the multi-layered core-shell structure YS B P A YS B P B YS B P CAll exhibit strong diffraction peaks at 20.75°, 29.15°, 33.69°, 48.47° and 57.59°, which correspond to the characteristic diffraction peaks of Y2O3. The characteristic diffraction peaks of polypyrrole are almost invisible in the figure.

[0102] from Figure 2 The results in Figure (c) show that the multilayered core-shell heterogeneous frost-like structure YS B P B M A YS B P B M B YS B P B M C Strong diffraction peaks were observed at 12.7°, 18.1°, 28.8°, 37.5°, 49.8°, 52.8°, 60.2°, 69.7°, and 71.1°, all of which correspond to the characteristic diffraction peaks of MnO2, indicating the successful synthesis of MnO2.

[0103] (3) SEM characterization of microwave absorbing composite materials

[0104] The microwave absorbing composite materials prepared in Examples 1-5 and Comparative Examples 1-4 of this invention, and the microwave absorbing material in Comparative Example 5, were examined using a Hitachi SU8100 (Regulus 8100) cold field emission scanning electron microscope. The results are as follows: Figure 3 As shown.

[0105] from Figure 3 As shown in Figures (a), (b), (c), and (d), the surface structure of yttrium oxide undergoes significant changes after being coated with a layer of SiO2. The material surface becomes relatively smooth, and the particle diameter increases significantly to approximately 200-300 nm, directly reflecting the successful coating of the SiO2 layer. With increasing SiO2 content, the particle morphology becomes nearly spherical, but excessive addition leads to a certain degree of aggregation.

[0106] from Figure 3 As can be seen from Figures (e), (f), and (g), YS B The surface is uniformly covered with a polypyrrole shell, and the surface of the shell shows some protrusions. These protrusions are the flocs formed by polypyrrole during the self-polymerization process, which directly proves the successful synthesis of polypyrrole.

[0107] from Figure 3 As shown in Figures (h), (i), and (j), the morphology of the rod-shaped manganese dioxide changes significantly with increasing reaction time, specifically exhibiting an increasing diameter trend; among them, YS B P BThe key frost fork points not only effectively connect the rod-shaped manganese dioxide, but also promote the formation of frost-like structures; the rod-shaped manganese dioxide extends like tree branches, closely connected with the frost forks, and together they construct this unique structure.

[0108] (4) Electromagnetic parameters of the absorbing composite material: ε', ε" and tanδ ε Characterization

[0109] The microwave absorbing composite materials prepared in Examples 1-5 and Comparative Examples 1-4 of this invention, and the microwave absorbing material in Comparative Example 5, were analyzed using a DR-S vector network analyzer. The electromagnetic parameters ε' (real part of dielectric constant), ε" (imaginary part of dielectric constant), and tanδ of each material were measured. ε (Dielectric loss tangent), the result is as follows Figure 4 As shown. (Given that this composite material is mainly composed of non-magnetic components Y2O3 and SiO2, the magnetic loss will not be described in detail.)

[0110] from Figure 4 The results show that the real part of the dielectric constant increases significantly after the introduction of MnO2, which indirectly increases the absorption performance; in addition, the imaginary part and the tangent of the dielectric constant both increase slightly.

[0111] (5) Attenuation coefficient curve of the absorbing composite material.

[0112] The microwave absorbing composite materials prepared in Examples 1-5 and Comparative Examples 1-4 of this invention, and the microwave absorbing material in Comparative Example 5, were used. The electromagnetic parameters of each material were detected using a DR-S vector network analyzer, and the attenuation coefficients of each material were calculated using an RL-Calculator. The results were plotted as follows: Figure 5 As shown. From Figure 5 The results show that the attenuation coefficient increased significantly after the introduction of MnO2, thereby increasing the absorption performance.

[0113] (6) Characterization of 3D and 2D reflection loss of absorbing composite material at different thicknesses

[0114] The microwave absorbing composite materials prepared in Examples 1-5 and Comparative Examples 1-4 of this invention, and the microwave absorbing material in Comparative Example 5, were used. The electromagnetic parameters of each material were measured using a DR-S vector network analyzer. The RL was calculated using an RL-Calculator. The 3D reflection loss (3D-RL) and 2D reflection loss (2D-RL) of each material at different thicknesses were plotted using Origin. The results are as follows: Figure 6 and Figure 7 As shown.

[0115] from Figure 6 Figures (a), (b), (c), and (d) and Figure 7As can be seen from figures (a), (b), (c), and (d), only YS B It meets the reflection loss standard, while YS A With YS C None of them crossed the critical threshold of -10dB, indicating relatively low electromagnetic wave absorption capability; however, YS B The limited effective absorption bandwidth restricts its application scope to some extent.

[0116] from Figure 6 Figures (e), (f), and (g) and Figure 7 As can be seen from (e), (f), and (g), with the change in the amount of pyrrole monomer added, YS B P A YS B P B YS B P C YS exhibits different absorption performance peaks. B P A It achieves excellent absorption performance of -37.8dB at 16.14GHz and a thickness of 5mm; subsequently, YS B P B By increasing the pyrrole content, a higher absorption performance of -42.3dB was achieved at 16.79GHz and a thickness of 3mm, demonstrating the positive effect of increasing the pyrrole content on performance; however, further increasing the pyrrole monomer content in YS... B P C However, the absorption performance decreased slightly to -41.3dB, indicating that there is an optimal balance between pyrrole content and absorption performance, showing a trend of first increasing and then decreasing.

[0117] from Figure 6 Figures (h), (i), and (j) and from Figure 7 As shown in Figures (h), (i), and (j), after the introduction of MnO2, the minimum value of RL gradually shifts to the low-frequency region with the increase of the thickness of the absorbing composite material, and the absorption performance of all samples is better than -10dB, meeting the standards for commercial applications. From the two-dimensional RL, it can be seen that the effective absorption bandwidth varies among different samples, and YS is clearly observed to be superior. B P B M C The narrowest, while YS B P B M B Then, while maintaining consistency with YS B P B M A While maintaining a similar bandwidth, it exhibits the highest absorption performance.

[0118] (7) Characterization of the internal structure of the microwave absorbing composite material system

[0119] The microwave absorbing composite materials prepared in Examples 1-5 and Comparative Examples 1-4 of this invention, and the microwave absorbing material in Comparative Example 5, were used. The electromagnetic parameters of each material were measured using a DR-S vector network analyzer. Cole-Cole curves for each material were plotted with ε' as the abscissa and ε" as the ordinate. The results are as follows: Figure 8 As shown. From Figure 8 The results show that the Cole-Cole curve, with its intuitive semicircular shape and straight tail, reveals the coexistence of polarization loss and conduction loss. The multiple semicircles on the curve demonstrate that multiple polarization loss processes occur in parallel. The curve exhibits significant fluctuations, revealing a large amount of polarization generated within the material. On one hand, the interface effect of the heterogeneous structure between different components in the absorbing composite inevitably induces interface polarization; on the other hand, potential structural defects within the material also become an important source of polarization loss. Both factors contribute to the material's electromagnetic response.

[0120] (8) Absorption performance test

[0121] The microwave absorbing composite materials prepared in Examples 1-5 and Comparative Examples 1-8 of this invention, as well as the microwave absorbing material in Comparative Example 5, were used to test their microwave absorption performance using the coaxial method (coaxial method: the microwave absorption performance of a material is reflected by measuring the power of the electromagnetic wave returning after the electromagnetic wave passes through it). First, the electromagnetic parameters of the materials were measured using a DR-S vector network analyzer, and then the magnetic wave absorption performance of each material was calculated using RL-Calculator software. The results are shown in Table 1.

[0122] Table 1 shows the test results of the microwave absorption performance in Examples 1-4 and Comparative Examples 1-8.

[0123] Examples / Comparative Examples Thickness (mm) EAB(GHz) RLmin(dB) Example 1 4.5 0.64 -51.95 Example 2 3 0.98 -42.36 Example 3 2.4 2.76 -38.14 Example 4 1.8 4.58 -52.05 Example 5 2 1.85 -38.99 Comparative Example 1 5 0 -1.74 Comparative Example 2 5 0 -1.69 Comparative Example 3 5 1.47 -37.93 Comparative Example 4 2.8 0.42 -41.23 Comparative Example 5 3.3 0 -7.06 Comparative Example 6 5.0 0 -3.99 Comparative Example 7 2.2 1.67 -30.13 Comparative Example 8 2.4 0.67 -46.88

[0124] As shown in Table 1, the multilayer core-shell heterogeneous frost-like structures YS prepared in Examples 3-5 of this invention... B P B M A YS B P B M B YS B P B M C Compared to comparative examples 5-8, YSPM exhibits superior microwave absorption performance, which stems from the synergistic effect of multi-component optimization and special structural design in enhancing microwave absorption performance.

[0125] By comparing Example 1, Comparative Examples 1-2, and Comparative Examples 5-6, it can be seen that after coating the surface of Y2O3 with SiO2, the microwave absorption performance is only that of YS. B There is an improvement, YS A and YS COther values ​​decreased, indicating that the SiO2 content does affect the absorption performance, but the effect is limited; and the effective absorption bandwidth (EAB) is very narrow, less than 1 GHz. When the Y2O3 surface is only coated with MnO2, the absorption performance is very low, reaching only -3.99 dB.

[0126] By comparing Example 2, Comparative Examples 3-4, and Comparative Example 7, it can be seen that in Comparative Example 7, without PPy, the absorption performance is only -30.13dB; after depositing a layer of PPy, YS B P B Although its absorption performance is better than YS B The absorption bandwidth (-51.95dB) is low, but its effective absorption bandwidth is improved by 0.34GHz; however, the content of PPy also affects the microwave absorption performance of the material, such as YS. B P A Although the effective absorption bandwidth has improved, the thickness is still relatively large; YS B P C The effective absorption bandwidth compared to YS B The absorption bandwidth is reduced to some extent. Therefore, this invention improves the effective absorption bandwidth of the absorbing material by optimizing the deposition amount of PPy.

[0127] By comparing Examples 2, 3-5, and Comparative Example 8, it can be seen that after the introduction of MnO2, the microwave absorption performance is better than that of YS. B P B There has been some improvement. YS B P B M A With a thickness of 2.4 mm, the absorption performance reaches -38.1 dB, and the effective absorption bandwidth is 2.87 GHz; YS B P B M B Compared to YS B P B M A The reaction time in step (3) was extended by 1 hour, YS B P B M B Its absorption performance has been improved, with the effective absorption bandwidth expanded to 4.58 GHz. YS B P B M B -2 compared to YS B P B M B When the mass of MnO2 is doubled during the preparation process, the performance reaches -46.88dB, which is higher than that of YS. B P B M A and YS B P B M C Lower than YSB P B M B However, its effective absorption bandwidth is relatively narrow. YS B P B M B It has the best absorption performance, especially in the mid-to-high frequency range, making it suitable for military radar applications.

[0128] This invention improves the microwave absorption performance by adjusting the amounts of each component in a multi-layered core-shell structure and changing the reaction conditions, thereby controlling the morphology and structure of the microwave absorbing composite material. The multi-layered core-shell Y2O3@SiO2@PPy@MnO2 microwave absorbing material provided by this invention has a stable structure, excellent microwave absorption performance, and a simple and low-cost preparation method.

[0129] 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 microwave absorbing composite material with a multilayered core-shell heterogeneous frost-like structure, characterized in that, The microwave absorbing composite material is composed of multilayer core-shell microspheres and nanorods, exhibiting a frost-like structure. The multilayer core-shell microspheres are made of Y2O3 as the core material, sequentially coated with SiO2 and PPy layers. The nanorods are made of MnO2. The mass ratio of Y₂O₃ to PPy is 7.14:1; The mass ratio of Y2O3 to MnO2 is 1:3.93~4.

07.

2. The microwave absorbing composite material according to claim 1, characterized in that, The particle size of the Y2O3 is 50-200 nm.

3. The microwave absorbing composite material according to claim 1, characterized in that, The mass ratio of Y2O3 to SiO2 is 1:

1.

4. A method for preparing the microwave absorbing composite material according to claim 1, characterized in that, The preparation method includes the following steps: (1) Preparation of monolayer core-shell microspheres Y2O3@SiO2: Y2O3 was dispersed in a solvent at room temperature, and then TEOS was added. The monolayer core-shell microspheres Y2O3@SiO2 coated with SiO2 were prepared by the Stober method. (2) Preparation of multilayer core-shell microspheres Y2O3@SiO2@PPy: The single-layer core-shell microspheres Y2O3@SiO2 obtained in step (1) were dispersed in deionized water, FeCl3·6H2O was added, and after mixing evenly, pyrrole monomer was added and reacted at room temperature. After treatment, multilayer core-shell microspheres Y2O3@SiO2@PPy were obtained. (3) Preparation of Y2O3@SiO2@PPy@MnO2 microwave absorbing composite material: The multilayer core-shell microspheres Y2O3@SiO2@PPy obtained in step (2) are dispersed in deionized water, then KMnO4 is added, hydrochloric acid is added dropwise while stirring, ultrasonication is performed, and the mixture is transferred to a reaction vessel for reaction. Finally, the mixture is cooled, filtered, the filter residue is collected, washed, and dried to obtain the Y2O3@SiO2@PPy@MnO2 microwave absorbing composite material.

5. The preparation method according to claim 4, characterized in that, In step (1), the solvent is an aqueous solution of ethanol with a volume fraction of 75%; the concentration of Y2O3 in the solvent is 0.11 mol / L, the concentration of TEOS in the solvent is 0.42 mol / L, and the reaction time is 4 h.

6. The preparation method according to claim 4, characterized in that, In step (2), the concentration of Y2O3@SiO2 in deionized water is 0.07 mol / L; the concentration of FeCl3·6H2O in deionized water is 0.07-0.08 mol / L; the concentration of pyrrole monomer in deionized water is 0.165 mol / L; the reaction temperature is -2~0 ℃, and the time is 4 h.

7. The preparation method according to claim 4, characterized in that, In step (3), the concentration of Y2O3@SiO2@PPy in deionized water is 0.0092 mol / L; the concentration of KMnO4 in deionized water is 0.083 mol / L; the mass percentage concentration of hydrochloric acid is 36~38%; the volume ratio of hydrochloric acid to deionized water is 1:80; the reaction temperature is 180℃; and the reaction time is 5~7 h.

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