ZnFe2O4-coated PPy composite microsphere as well as preparation method and application thereof
ZnFe2O4@PPy composite microspheres were prepared by spray pyrolysis and in-situ gas phase polymerization, and the surface wrinkle structure was adjusted, which solved the problem of insufficient electromagnetic wave absorption performance in the prior art, and achieved efficient electromagnetic wave absorption effect.
Patent Information
- Application Number
- CN202510548490.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-28
- Publication Date
- 2025-08-15
AI Technical Summary
It is difficult to prepare core-shell structure microspheres with excellent electromagnetic wave absorption performance, especially in regulating the surface wrinkle structure.
ZnFe2O4@PPy composite microspheres were prepared by spray pyrolysis and in-situ gas phase polymerization. The concentration of metal nitrate is adjusted to control the surface wrinkle structure, forming a highly conductive PPy shell wrapped in the ZnFe2O4 core, and optimizing impedance matching.
A wrinkled core-shell microsphere with rich specific surface area was prepared, which significantly improved the electromagnetic wave absorption performance. RLmin can reach -41dB and the effective absorption width reaches 4.1GHz.
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Figure CN120484255A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of composite material preparation, and in particular to ZnFe2O4@PPy composite microspheres and a preparation method and application thereof. Background Art
[0002] With the continuous advancement of science and technology, eliminating electromagnetic wave pollution is imperative. Therefore, designing and constructing new microwave absorbing materials with "thin thickness, lightweight, strong absorption, and wide bandwidth" has become a key research goal in the field of microwave absorption. In summary, designing core-shell absorbing materials that combine magnetic and dielectric components is one effective strategy for enhancing performance. Composite materials with core-shell structures can fully utilize the synergistic effects of the magnetic and dielectric components, greatly improving their ability to absorb incident electromagnetic waves. Summary of the Invention
[0003] The purpose of the present invention is to provide ZnFe2O4@PPy composite microspheres and a preparation method and application thereof, which overcome the shortcomings of the prior art.
[0004] In order to solve the above problems, the technical solutions adopted by the present invention are as follows:
[0005] The preparation method of ZnFe2O4@PPy composite microspheres comprises the following steps:
[0006] S1, dissolving a soluble zinc source, an iron source, and a surfactant in a solvent, and stirring to obtain a uniformly mixed solution A;
[0007] S2, pyrolyzing solution A using a spray pyrolysis device, and collecting the resulting precursor after pyrolysis;
[0008] S3, calcining the collected precursor in an air environment to obtain a ZnFe2O4 precursor;
[0009] S4, soaking the ZnFe2O4 precursor in an oxidant solution and then drying it to obtain a composite precursor; then placing the composite precursor and a pyrrole monomer in a sealed container without direct contact between the composite precursor and the pyrrole monomer, heating the sealed container to allow the pyrrole monomer to undergo a polymerization reaction, thereby obtaining ZnFe2O4@PPy composite microspheres;
[0010] The molar ratio of zinc to iron in the zinc source and the iron source is 2:1; the iron in the iron source is Fe 3+ , the zinc element in the zinc source is Zn 2+ ;
[0011] The solvent is prepared by mixing water, ethanol and N-N-dimethylformamide in a volume ratio of 1:1:1.
[0012] Furthermore, the concentration of the surfactant in the solvent is 50 mg / mL.
[0013] Furthermore, the surfactant is polyvinyl pyrrolidone.
[0014] Furthermore, during the spray pyrolysis in step S2, the inlet temperature of the spray pyrolysis device is 180° C., the outlet temperature is 90° C., and the feed rate is 1500 mL / h.
[0015] Furthermore, the calcination conditions in step S3 are: heating to 400° C. at a heating rate of 2° C. / min, and calcining at 400° C. for 5 h.
[0016] Furthermore, in step S4, the sealed container is heated to 50° C., and the polymerization reaction time is 48 h.
[0017] Furthermore, in step S4, the oxidant solution is an aqueous solution of FeCl3.
[0018] The ZnFe2O4@PPy composite microspheres prepared by the above method are core-shell microspheres with a wrinkled surface structure.
[0019] Application of ZnFe2O4@PPy composite microspheres in the field of electromagnetic wave absorption materials.
[0020] Compared with the prior art, the present invention has the following advantages:
[0021] 1. The present invention prepares core-shell microspheres with a wrinkled structure. By adjusting the concentration of the added metal nitrate, the surface wrinkled structure can be effectively adjusted. Therefore, this preparation strategy shows significant superiority.
[0022] 2. Due to the large specific surface area of the wrinkled structure, the highly conductive PPy shell is tightly wrapped on the surface of the ZnFe2O4 microspheres, generating a rich wrinkled ZnFe2O4@PPy core-shell structure, which optimizes the impedance matching of the ferrite-polymer composite system. The optimized ZnFe2O4@PPy-2 microspheres have excellent electromagnetic wave absorption performance, RL min It can reach -41dB, and the effective absorption width is up to 4.1GHz. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 These are scanning electron microscope images of ZnFe2O4-1(a), ZnFe2O4-2(b), ZnFe2O4-3(c), and ZnFe2O4-4(d) in Examples 1-4 of the present invention;
[0024] Figure 2The scanning electron microscope image (a) and transmission electron microscope image (b) of ZnFe2O4-2 of Example 2, and the scanning electron microscope image (c) and transmission electron microscope image (d) of ZnFe2O4@PPy-2;
[0025] Figure 3 The scanning electron micrograph (d) of ZnFe2O4@PPy-1, the scanning electron micrograph (f) of ZnFe2O4@PPy-3, and the scanning electron micrograph (i) of ZnFe2O4@PPy-4 in Examples 1, 3, and 4;
[0026] Figure 4 The XRD patterns of ZnFe2O4@PPy-1, ZnFe2O4@PPy-2, and ZnFe2O4@PPy-3 of Examples 1-3 are shown;
[0027] Figure 5 These are the reflection loss diagrams (ac) of ZnFe2O4@PPy-1 to electromagnetic waves, the reflection loss diagrams (df) of ZnFe2O4@PPy-2 to electromagnetic waves, the reflection loss diagrams (gi) of ZnFe2O4@PPy-3 to electromagnetic waves, and the reflection loss diagrams (jl) of ZnFe2O4@PPy-4 to electromagnetic waves of Examples 1-4. DETAILED DESCRIPTION
[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.
[0029] Example 1
[0030] 1.0 mmol of Fe(NO₃)₃·9H₂O, 0.5 mmol of Zn(NO₃)₂·6H₂O, and 1.5 g of polyvinylpyrrolidone K30 were dissolved in 30 mL of a solution consisting of 10 mL of deionized water, 10 mL of anhydrous ethanol, and 10 mL of NN-dimethylformamide, with continuous stirring to obtain a homogeneous solution. The spray pyrolysis parameters were set at an inlet temperature of 180°C, an outlet temperature of 90°C, and a feed rate of 1500 mL / h. The precursor collected after spray drying was then calcined in air at 400°C for 5 hours at a heating rate of 2°C / min to obtain the ZnFe₂O₄ precursor (ZnFe₂O₄-1).
[0031] First, 0.15g of ZnFe2O4 precursor powder was immersed in 0.3mL of FeCl3 catalyst aqueous solution and dried to obtain a composite precursor. A vial containing 2mL of pyrrole monomer and another vial containing 0.15g of the composite precursor were then sealed in a Duran flask and heated at 50°C for 48h to produce wrinkled core-shell composite microspheres, ZnFe2O4@PPy-1.
[0032] Example 2
[0033] 2.0 mmol of Fe(NO₃)₃·9H₂O, 1.0 mmol of Zn(NO₃)₂·6H₂O, and 1.5 g of polyvinylpyrrolidone K30 were dissolved in 30 mL of a solution consisting of 10 mL of deionized water, 10 mL of anhydrous ethanol, and 10 mL of NN-dimethylformamide, with continuous stirring to obtain a homogeneous solution. The spray pyrolysis parameters were set at an inlet temperature of 180°C, an outlet temperature of 90°C, and a feed rate of 1500 mL / h. The precursor collected after spray drying was then calcined in air at 400°C for 5 hours at a heating rate of 2°C / min to obtain the ZnFe₂O₄ precursor (ZnFe₂O₄-2).
[0034] First, 0.15g of ZnFe2O4 precursor powder was immersed in 0.3mL of FeCl3 catalyst aqueous solution and dried to obtain a composite precursor. A vial containing 2mL of pyrrole monomer and another vial containing 0.15g of the composite precursor were then sealed in a Duran flask and heated at 50°C for 48h to produce wrinkled core-shell composite microspheres, ZnFe2O4@PPy-2.
[0035] Example 3
[0036] 4.0 mmol of Fe(NO₃)₃·9H₂O, 2.0 mmol of Zn(NO₃)₂·6H₂O, and 1.5 g of polyvinylpyrrolidone K30 were dissolved in 30 mL of a solution consisting of 10 mL of deionized water, 10 mL of anhydrous ethanol, and 10 mL of NN-dimethylformamide, with continuous stirring to obtain a homogeneous solution. The spray pyrolysis parameters were set at an inlet temperature of 180°C, an outlet temperature of 90°C, and a feed rate of 1500 mL / h. The precursor collected after spray drying was then calcined at 400°C in air at a heating rate of 2°C / min for 5 hours to obtain the ZnFe₂O₄ precursor (ZnFe₂O₄-3).
[0037] First, 0.15g of ZnFe2O4 precursor powder was immersed in 0.3mL of FeCl3 catalyst aqueous solution and dried to obtain a composite precursor. A vial containing 2mL of pyrrole monomer and another vial containing 0.15g of the composite precursor were then sealed in a Duran flask and heated at 50°C for 48h to produce wrinkled core-shell composite microspheres, ZnFe2O4@PPy-3.
[0038] Example 4
[0039] 6.0 mmol of Fe(NO₃)₃·9H₂O, 3.0 mmol of Zn(NO₃)₂·6H₂O, and 1.5 g of polyvinylpyrrolidone K30 were dissolved in 30 mL of a solution consisting of 10 mL of deionized water, 10 mL of anhydrous ethanol, and 10 mL of NN-dimethylformamide, and stirred continuously to obtain a homogeneous solution. The spray pyrolysis parameters were set at an inlet temperature of 180°C, an outlet temperature of 90°C, and a feed rate of 1500 mL / h. The precursor collected after spray drying was then calcined at 400°C in air at a heating rate of 2°C / min for 5 hours to obtain the ZnFe₂O₄ precursor (ZnFe₂O₄-4).
[0040] First, 0.15g of ZnFe2O4 precursor powder was immersed in 0.3mL of FeCl3 catalyst aqueous solution and dried to obtain a composite precursor. A vial containing 2mL of pyrrole monomer and another vial containing 0.15g of the composite precursor were then sealed in a Duran flask and heated at 50°C for 48h to produce wrinkled core-shell composite microspheres, ZnFe2O4@PPy-4.
[0041] The ZnFe2O4 precursor and composite microspheres in Examples 1-4 were analyzed using a scanning electron microscope, wherein the scanning electron microscope photo of the ZnFe2O4 precursor is shown in FIG. Figure 1 As shown, Examples 1-4 were successfully assembled into spherical ZnFe2O4 precursors after spray drying, and the ZnFe2O4 precursors were evenly distributed; the ZnFe2O4-2 microspheres prepared by spray pyrolysis and air annealing showed a wrinkled surface structure ( Figure 2 a), and TEM images ( Figure 2b) It was found that the microspheres have a core-shell structure. During the air calcination process, oxygen enters the spray precursor and oxidizes the zinc iron metal salt to ZnFe2O4-2, converting the carbon source PVP-K30 used to anchor the metal ions into gas molecules such as carbon dioxide and overflowing from the inside to the outside of the microspheres. Due to the different gas diffusion rates, the material shrinks unevenly, and finally forms core-shell ZnFe2O4-2 microspheres with a special wrinkled surface structure. After the ZnFe2O4-2 microspheres are treated with in-situ gas phase polymerization, it can be clearly found that the wrinkled surface of the microspheres becomes smooth and maintains the original morphology and structure, indicating that the pyrrole monomer is in-situ polymerized on the surface of the microspheres to form polypyrrole and evenly adheres to the surface of the wrinkled microspheres, thereby successfully preparing ZnFe2O4@PPy-2 wrinkled composite microspheres ( Figure 2 c). The original core-shell structure of ZnFe2O4-2 can still be maintained after in-situ gas phase polymerization. The difference is that compared with Figure 2 b, It can be clearly observed that there is a layer of attachment on the outer surface of the ZnFe2O4@PPy-2 wrinkled composite microspheres, which further shows the successful coating of polypyrrole (PPy) on the surface of ZnFe2O4-2.
[0042] The crystal structures of the ZnFe2O4 precursors and composite microspheres of Examples 1-4 were determined by XRD. Figure 4 Shown: In Figure 4 In a, the ZnFe2O4 precursor prepared by spray pyrolysis showed obvious characteristic diffraction peaks at 14.9°, 17.6°, 23.4°, 26.6° and 28.3°, which correspond to the five characteristic crystal planes (220), (311), (331), (422) and (511) of ZnFe2O4 (JPCDS: 79-1150), respectively. The overall sample obtained did not show any impurity peaks, which proved the successful preparation of ZnFe2O4. Subsequently, the surface of the ZnFe2O4 precursor was coated with polypyrrole by in-situ gas phase polymerization to obtain composite microspheres. Similarly, as Figure 4 As shown in Figure b, the XRD results of the composite microspheres showed no significant changes compared with the ZnFe2O4 precursor without PPy coating, proving that the in situ vapor phase polymerization process of PPy coating does not affect the physical phase of the ZnFe2O4 precursor.
[0043] Figure 5 The frequency-reflection loss relationship diagram of composite microspheres in the coating thickness range of 1.0-5.0mm. Figure 5 In the ac, ZnFe2O4@PPy-1 has a minimum reflection loss value (RL) of -14.0dB at 14.0GHz under the conditions of 2.0mm thickness and effective absorption bandwidth (EAB) of 5.2GHz. min). With the increase of metal salt concentration, the wrinkle degree of the material surface increases. For ZnFe2O4@PPy-2 sample with a thickness of 2.0 mm, RL min The value increases to -18.0dB, and at 3.5mm thickness, the RL at 7.4GHz min It reaches -41.0dB, and the EBA reaches 4.1GHz width. Figure 5 df shows that compared with the RL of ZnFe2O4@PPy-1 sample with the same thickness of 3.5 mm, min =-10.5dB, and its maximum absorption intensity increased by about 4 times, preliminarily proving that the microwave absorption performance of the sample can be improved as the degree of wrinkling on the surface of the material increases. When the concentration of the metal salt increases until the structure collapses into irregular blocks, such as Figure 5 As shown in gi, ZnFe2O4@PPy-3 has a RL of 2.0 mm in thickness and an EAB of 3.4 GHz. min Only -12.0dB, also at 3.5mm thickness, RL min Furthermore, we tried to increase the concentration of metal salts to explore the effect of structure on performance. Figure 5 As shown in jl, the ZnFe2O4@PPy-4 with further collapsed structure showed worse absorption performance. At a thickness of 2.0 mm, the RL was less than -8.0 dB. min This further demonstrates that both the surface wrinkling and spherical structures are crucial for the microwave absorption performance of the composite microspheres. Because ZnFe2O4@PPy-4 and ZnFe2O4@PPy-3 share significant similarities in morphology, structure, and microwave absorption, we will use ZnFe2O4@PPy-3 as the starting point for structural collapse, and will not discuss ZnFe2O4@PPy-4 in subsequent electromagnetic parameter analysis. Furthermore, while maintaining the wrinkled structure, the abundant internal space within the core-shell structure and the spherical shell surface enhance multiple reflections, further dissipating a significant amount of electromagnetic waves and contributing to improved microwave absorption performance.
[0044] It should also be noted that: the present invention uses the N5230C vector network analyzer to test the relative complex dielectric constant and magnetic permeability of the sample in the range of 2.0-18.0GHz. The process of preparing the sample includes the following steps: first, the synthesized composite microsphere sample powder is mixed with paraffin in a mass ratio of 5:5, and then heated and stirred to mix the two evenly, and the mixture is transferred to a pressure ring mold with an outer diameter of 7.0mm, an inner diameter of 3.0mm, and a thickness of about 1.8mm. Appropriate pressure is applied to compact the ring, and the test can be carried out after the ring is completely cooled. Through calculation, the reflection loss value, dielectric loss tangent value, attenuation constant and other parameters of the sample can be obtained, and then the microwave absorption performance of the material can be analyzed. The calculation formula is as follows:
[0045]
[0046] RL(dB)=-20log|Z in -1 / Z in +1|
[0047] Where Z in is the input resistance; μr and εr are the relative complex permittivity and permeability, respectively; f is the frequency of the incident electromagnetic wave; d is the thickness of the material; and c is the speed of the electromagnetic wave in a vacuum.
[0048] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.
Claims
1. A method for preparing ZnFe2O4@PPy composite microspheres, characterized in that: The following steps are involved: S1, dissolving a soluble zinc source, an iron source, and a surfactant in a solvent, and stirring to obtain a uniformly mixed solution A; S2, pyrolyzing solution A using a spray pyrolysis device, and collecting the resulting precursor after pyrolysis; S3, calcining the collected precursor in an air environment to obtain ZnFe2O4@PPy composite microspheres; S4, soaking the ZnFe2O4 precursor in an oxidant solution and then drying it to obtain a composite precursor; then placing the composite precursor and a pyrrole monomer in a sealed container without direct contact between the composite precursor and the pyrrole monomer, heating the sealed container to allow the pyrrole monomer to undergo a polymerization reaction, thereby obtaining ZnFe2O4@PPy composite microspheres; The molar ratio of zinc to iron in the zinc source and the iron source is 2:1; the iron in the iron source is Fe 3 + , the zinc element in the zinc source is Zn 2+ ; The solvent is prepared by mixing water, ethanol and N-N-dimethylformamide in a volume ratio of 1:1:
1.
2. The method for preparing ZnFe2O4@PPy composite microspheres according to claim 1, characterized in that: The concentration of the surfactant in the solvent is 50 mg / mL.
3. The method for preparing ZnFe2O4@PPy composite microspheres according to claim 1 or 2, characterized in that: The surfactant is polyvinyl pyrrolidone.
4. The method for preparing ZnFe2O4@PPy composite microspheres according to claim 1, characterized in that: During the spray pyrolysis in step S2, the inlet temperature of the spray pyrolysis device is 180° C., the outlet temperature is 90° C., and the feed rate is 1500 mL / h.
5. The method for preparing ZnFe2O4@PPy composite microspheres according to claim 1, characterized in that: The calcination conditions in step S3 are: heating to 400° C. at a heating rate of 2° C. / min and calcining at 400° C. for 5 h.
6. The method for preparing ZnFe2O4@PPy composite microspheres according to claim 1, characterized in that: In step S4, the sealed container is heated to 50° C., and the polymerization reaction time is 48 hours.
7. The method for preparing ZnFe2O4@PPy composite microspheres according to claim 1, characterized in that: In step S4, the oxidant solution is an aqueous solution of FeCl3.
8. ZnFe2O4@PPy composite microspheres, characterized in that: Prepared by the method according to any one of claims 1 to 5.
9. The ZnFe2O4@PPy composite microspheres according to claim 8, characterized in that The microspheres are core-shell microspheres with a wrinkled surface.
10. The ZnFe2O4@PPy composite microspheres according to claim 8, characterized in that Application in the field of electromagnetic wave absorbing materials.