Preparation method of monatomic material for regulating electromagnetic wave absorption frequency

Abstract

The application relates to a preparation method of a material for regulating the electromagnetic wave absorption frequency of single atoms, and belongs to the electromagnetic wave absorption field. The scheme comprises the following steps: step I: synthesizing a metal organic framework M-PCN-222 by adopting a solvothermal method; step II: pyrolyzing the M-PCN-222 obtained in step I into a single atom loaded carbon-based microrod composite material; and step III: compounding the single atom loaded carbon-based microrod composite material M-N-C / ZrO2 obtained in step II with a high polymer polymer PVDF, and preparing a composite material by adopting an ultrasonic method. The scheme has the advantages of simple operation and large-scale production potential. The obtained composite wave absorbing material can not only maintain the advantages of light weight and corrosion resistance of carbon-based nanomaterials, but also overcome the shortcomings of high density, easy aggregation and narrow absorption frequency band of single ferromagnetic materials by means of uniform distribution of single atoms.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic wave absorption materials, specifically the regulation of electromagnetic wave absorption frequency through the use of single atomic species. A method for preparing a transition metal single-atom carbon-based composite material is also disclosed, including a composite material (MNC / ZrO2-PVDF) of single-atom carbon-based nanorods (MNC / ZrO2) and polyvinylidene fluoride (PVDF). This invention belongs to the field of nanomaterials. Background Art

[0002] Electromagnetic wave absorbing materials have broad application prospects in areas such as military stealth, improving the electromagnetic compatibility of electronic equipment, and aerospace. Traditional electromagnetic wave absorbing materials often suffer from fixed absorption frequencies and difficulty absorbing low-frequency signals, making them difficult to meet the demands for tunable frequency bands and high-efficiency absorption in practical applications. Therefore, the development of electromagnetic wave absorbing materials with tunable absorption frequencies has become a research hotspot.

[0003] In recent years, single-atom doping technology has provided new insights into improving the performance of electromagnetic wave absorbing materials. By doping single atoms into carbon-based nanomaterials, the number of polarization sites within the material can be increased, thereby enhancing the polarization effect, optimizing impedance matching, and improving the material's electromagnetic wave absorption capacity. At the same time, single-atom doping can also maintain the lightweight properties of carbon nanomaterials, which is crucial for maintaining the material's application advantages. However, research on single-atom regulation of electromagnetic wave absorption frequency is still in its infancy. How to achieve tunability of electromagnetic wave absorption frequency through single-atom regulation and how to improve the material's electromagnetic wave absorption efficiency remain urgent issues. Summary of the Invention

[0004] In light of this, the present invention proposes a method for regulating the electromagnetic wave absorption frequency using single atoms and an electromagnetic wave absorbing material prepared using this method. These methods aim to achieve tunable electromagnetic wave absorption frequency and improve the material's electromagnetic wave absorption efficiency. This method is simple to operate and has the potential for large-scale production. The resulting composite absorbing material retains the advantages of carbon-based nanomaterials, such as lightweight and corrosion resistance, while overcoming the shortcomings of single ferromagnetic materials, such as high density, easy aggregation, and narrow absorption bandwidth, through the uniform distribution of single atoms.

[0005] To achieve the above object, according to one aspect of the present invention, a method for preparing a composite absorbing material is provided.

[0006] The method of the present invention for preparing a material for regulating the absorption frequency of electromagnetic waves by single atoms comprises the following steps:

[0007] Step I: Synthesis of the metal-organic framework M-PCN-222 by solvothermal method;

[0008] Step II: sintering and pyrolysis of M-PCN-222 obtained in step I in an inert atmosphere into monatomic carbon-based microrod composite material, i.e. M-N-C / ZrO2 nanorod;

[0009] Step III: compounding monatomic carbon-based microrod composite material M-N-C / ZrO2 nanorod obtained in step II with high molecular polymer PVDF to prepare composite material M-N-C / ZrO2-PVDF by ultrasonic method;

[0010] Preferably, step I comprises the following steps:

[0011] Tetrakis(4-carboxyphenyl)porphyrin (H2-TCPP) and 5,10,15,20-tetrakis(4-carboxyphenyl) metal (metal M is selected from iron, cobalt and nickel) porphyrin (M-TCPP) are placed in DMF in proportion with ZrOCl2·8H2O and CF3COOH, CF3COOH is used to adjust the acidity, and after refluxing by oil bath heating; the product is separated and washed by DMF and acetone to obtain M-PCN-222.

[0012] Preferably, the total amount of H2-TCPP and M-TCPP (molar ratio of 3-4:1) is in a molar ratio of 1:(8-9) to the amount of ZrOCl2·8H2O, and the volume ratio of CF3COOH to DMF solvent is 1:20-25. The temperature range of oil bath heating reflux is 120-130℃.

[0013] After a series of proportion control, the aspect ratio of M-PCN-222 of this proportion is uniform and stable, and after sintering, suitable dielectric properties are obtained, which is conducive to the matching of magneto-dielectricity and the excellent wave absorption performance.

[0014] The open solvent thermal method directly reacts under normal pressure by using high-temperature solvent, which can reduce the requirement for experimental equipment and is easy for further industrial production. Compared with other technologies, the product has high purity, good uniformity, good dispersity and low production cost. In the present application, the precursor M-PCN-222 with stable composition is obtained by the open solvent thermal method, and the operation is simple.

[0015] Preferably, in step II: the inert atmosphere is nitrogen or argon, the sintering temperature is 700-900℃, preferably 800℃, and the sintering time is 2 hours. By simple sintering, carbon material with high dielectric is obtained, so as to optimize the matching of magneto-dielectricity and the wave absorption performance.

[0016] M-N-C / ZrO2 nanorod: monatomic N-coordinated fixed on one-dimensional carbon nanorod

[0017] Preferably, step III comprises:

[0018] (III-1): The MNC / ZrO2 nanorod material obtained in step II and PVDF are weighed in proportion, preferably the mass ratio of single-atom-loaded carbon-based microrods MNC / ZrO2 to PVDF is 1:(8-10).

[0019] (III-2): The weighed PVDF is dissolved in N,N-dimethylformamide and ultrasonically treated until a transparent mixed liquid is obtained. The weighed MNC / ZrO2 nanorod material is added to the transparent mixed liquid and mechanically stirred to obtain a black suspension. The black suspension is then subjected to solvent thermal evaporation to form a film, thereby obtaining a composite membrane MNC / ZrO2-PVDF of single-atom-loaded carbon-based microrods MNC / ZrO2 and PVDF, and the obtained composite membrane has toughness.

[0020] The present invention also relates to a composite absorbing material prepared by the method, which is a composite absorbing material (MNC / ZrO2-PVDF) composed of monoatomic carbon-based microrods (MNC / ZrO2) and polyvinylidene fluoride (PVDF). The thickness of the MNC / ZrO2-PVDF composite film is preferably 2-5 mm.

[0021] Carbon materials do not meet the requirements of dielectric magnetic matching due to their high electrical conductivity, which limits their use in the field of wave absorption. The present invention loads single atoms onto carbon-based composite materials, and by regulating the differences in the electronic coordination structure of single atoms, effectively acts on dielectric magnetic matching and optimizes wave absorption performance; it also has unique polarization center sites, good mechanical properties, high chemical stability and other properties.

[0022] This invention proposes a method for regulating electromagnetic wave absorption frequency using single atoms, and an electromagnetic wave absorbing material prepared using this method. Through single-atom doping, the electromagnetic wave absorption frequency is tunable and the material's electromagnetic wave absorption efficiency is improved. Experimental results show that the electromagnetic wave absorbing material prepared by this method exhibits excellent electromagnetic wave absorption performance in the lower frequency range, and the absorption frequency can be controlled by adjusting the type and concentration of the doping element and the synthesis conditions. This invention provides new ideas and methods for the research and development of electromagnetic wave absorbing materials and has broad application prospects.

[0023] Compared with the prior art, the materials and methods of the present invention have the following advantages:

[0024] (1) The method of the present invention adopts the open solvent method to synthesize PCN-222, obtaining uniformly dispersed microrods, which can be precipitated, separated and washed, and the operation is simple. Figure 1 .

[0025] (2) The composite absorbing material of the present invention is prepared by pyrolysis of an organic metal framework template, wherein single atoms are fixed on one-dimensional carbon nanorods through nitrogen coordination, thus solving the problem of metal agglomeration.Figure 2 .

[0026] (3) The single-atom carbon-based nanorods MNC / ZrO2 in the composite absorbing material of the present invention have a porous structure (see transmission electron microscopy Figure 2 ), which is not only convenient for regulating dielectric magnetic matching and optimizing wave absorption performance, but also has unique structural characteristics, high chemical stability and other properties.

[0027] (4) In the composite absorbing material of the present invention, single-atom carbon-based nanorods MNC / ZrO2 are uniformly distributed in the PVDF matrix. Compared with the absorbing effect, it not only greatly improves the electromagnetic wave absorption intensity of the material, but also effectively regulates the frequency absorption band by designing the type of single atoms. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] For purposes of illustration and not limitation, the methods and materials of the present invention will now be described in accordance with preferred embodiments thereof with reference to the accompanying drawings, in which:

[0029] Figure 1 This is the SEM image of the M-PCN-222 nanorods obtained in Example 2, where ac represents Fe-PCN-222, Co-PCN-222, and Ni-PCN-222, respectively.

[0030] Figure 2 This is the TEM image of the single-atom carbon-based nanorods MNC / ZrO2 obtained in Example 2 when sintered at 800°C, where ac represents Fe-NC / ZrO2, Co-NC / ZrO2, and Ni-NC / ZrO2, respectively.

[0031] Figure 3 The single-atom carbon-based nanorods MNC / ZrO2 obtained in Example 2 were heated at 800 °C.

[0032] XRD pattern during sintering.

[0033] Figure 4 The reflection loss curves of 10.0wt% MNC / ZrO2-PVDF at different thicknesses at a sintering temperature of 700℃, where ac represents

[0034] Fe-NC / ZrO2-PVDF, Co-NC / ZrO2-PVDF, Ni-NC / ZrO2-PVDF.

[0035] Figure 5 The reflection loss curves of 10.0wt% MNC / ZrO2-PVDF at different thicknesses at a sintering temperature of 800℃, where ac represents

[0036] Fe-NC / ZrO2-PVDF, Co-NC / ZrO2-PVDF, Ni-NC / ZrO2-PVDF.

[0037] Figure 6 The reflection loss curves of 10.0wt% MNC / ZrO2-PVDF at different thicknesses at a sintering temperature of 900℃, where ac represents

[0038] Fe-NC / ZrO2-PVDF, Co-NC / ZrO2-PVDF, Ni-NC / ZrO2-PVDF.

[0039] Figure 7 Comparison of reflection loss curves of 10.0wt% MNC / ZrO2-PVDF at a sintering temperature of 800℃ and a thickness of 4mm. DETAILED DESCRIPTION

[0040] The present invention will be further described below with reference to the examples, but the present invention is not limited to the following examples.

[0041] Example 1

[0042] (1) Tetrakis(4-carboxyphenyl)porphine (H2-TCPP) and 5,10,15,20-tetrakis(4-

[0043] Carboxyphenyl) metal (metal M is selected from iron, cobalt, nickel) porphyrin (M-TCPP) is placed in DMF with ZrOCl2·8H2O and CF3COOH in proportion, and heated under reflux in an oil bath;

[0044] After the product was isolated, it was washed with DMF and acetone to obtain M-PCN-222;

[0045] The sum of H2-TCPP and M-TCPP (the molar ratio of the two is 3:1) is the same as the

[0046] The molar ratio of ZrOCl2·8H2O was 1:8.5, and the ratio of CF3COOH in DMF solvent was 1:25. The temperature range of oil bath heating reflux was 120-130°C, and the reaction was carried out for 2-3 days.

[0047] (2) Preparation of single-atom loaded carbon-based microrods MNC / ZrO2

[0048] The M-PCN-222 obtained above was subjected to high temperature treatment at 700°C for 2 h under nitrogen protection to obtain carbon-based microrods loaded with single atoms of different metals (iron, cobalt, nickel);

[0049] (3) The single-atom loaded carbon-based microrods MNC / ZrO2 and polyvinylidene fluoride PVDF were mixed in a mass ratio of 1:9 to prepare the composite absorbing material MNC / ZrO2-PVDF.

[0050] MNC / ZrO2 nanorods and PVDF were weighed at a mass ratio of 1:9, with a total mass of 0.1 g. PVDF was dissolved in 10 mL of N,N-dimethylformamide and sonicated until a transparent mixture was obtained. The MNC / ZrO2 nanorods were then dispersed in the mixture and sonicated until a black suspension was obtained. The prepared mixture was transferred to an evaporating dish and placed in a 70°C oven for 4 hours to evaporate the solvent. MNC / ZrO2-PVDF membranes (700-Fe-CN / ZrO2, 700-Co-CN / ZrO2, and 700-Ni-CN / ZrO2, corresponding to different metal M) were prepared by compression molding with thicknesses of 2 mm, 3 mm, 4 mm, and 5 mm.

[0051] The obtained MNC / ZrO2-PVDF membrane was pressed into sheets by hot pressing and the absorption test was performed by coaxial method. Figure 4 As shown in the figure, when the sintering temperature is 700℃, the composite material of different metal single atoms has a certain wave absorption ability, the electromagnetic wave absorption frequency is concentrated in the 8-12GHz band, and the reflection loss intensity is higher than -30dB. The result is not very ideal, so the pyrolysis temperature is increased.

[0052] Example 2

[0053] (1) Tetrakis(4-carboxyphenyl)porphine (H2-TCPP) and 5,10,15,20-tetrakis(4-

[0054] Carboxyphenyl) metal (metal M is selected from iron, cobalt, nickel) porphyrin (M-TCPP) is placed in DMF with ZrOCl2·8H2O and CF3COOH in proportion, and heated under reflux in an oil bath;

[0055] After the product was isolated, it was washed with DMF and acetone to obtain M-PCN-222;

[0056] The sum of H2-TCPP and M-TCPP (the molar ratio of the two is 3:1) is the same as the

[0057] The molar ratio of ZrOCl2·8H2O was 1:8.5, and the ratio of CF3COOH in DMF solvent was 1:25. The temperature range of oil bath heating reflux was 120-130°C, and the reaction was carried out for 2-3 days.

[0058] (2) Preparation of single-atom loaded carbon-based microrods MNC / ZrO2

[0059] The M-PCN-222 obtained above was subjected to high-temperature treatment at 800°C for 2 h under nitrogen protection to obtain carbon-based microrods loaded with single atoms of different metals (iron, cobalt, nickel);

[0060] (3) The single-atom loaded carbon-based microrods MNC / ZrO2 and polyvinylidene fluoride PVDF were mixed in a mass ratio of 1:9 to prepare the composite absorbing material MNC / ZrO2-PVDF.

[0061] MNC / ZrO2 nanorods and PVDF were weighed at a mass ratio of 1:9, with a total mass of 0.1 g. PVDF was dissolved in 10 mL of N,N-dimethylformamide and sonicated until a transparent mixture was obtained. The MNC / ZrO2 nanorods were then dispersed in the mixture and sonicated until a black suspension was obtained. The prepared mixture was transferred to an evaporating dish and placed in a 70°C oven for 4 hours to evaporate the solvent. MNC / ZrO2-PVDF membranes (800-Fe-CN / ZrO2, 800-Co-CN / ZrO2, and 800-Ni-CN / ZrO2, corresponding to different metal M) were prepared by compression molding with thicknesses of 2 mm, 3 mm, 4 mm, and 5 mm.

[0062] The obtained MNC / ZrO2-PVDF membrane was pressed into sheets by hot pressing and the absorption test was performed by coaxial method. Figure 5 As shown in the figure, when the sintering temperature is 800℃, due to the impedance matching principle, the composite materials of different metal single atoms have a relatively ideal absorbing ability, and their optimal reflection loss intensity is lower than -40dB.

[0063] Example 3

[0064] (1) Tetrakis(4-carboxyphenyl)porphine (H2-TCPP) and 5,10,15,20-tetrakis(4-

[0065] Carboxyphenyl) metal (metal M is selected from iron, cobalt, nickel) porphyrin (M-TCPP) is placed in DMF with ZrOCl2·8H2O and CF3COOH in proportion, and heated under reflux in an oil bath;

[0066] After the product was isolated, it was washed with DMF and acetone to obtain M-PCN-222;

[0067] The sum of H2-TCPP and M-TCPP (the molar ratio of the two is 3:1) is the same as the

[0068] The molar ratio of ZrOCl2·8H2O was 1:8.5, and the ratio of CF3COOH in DMF solvent was 1:25. The temperature range of oil bath heating reflux was 120-130°C, and the reaction was carried out for 2-3 days.

[0069] (2) Preparation of single-atom loaded carbon-based microrods MNC / ZrO2

[0070] The M-PCN-222 obtained above was subjected to high temperature treatment at 900°C for 2 h under nitrogen protection to obtain carbon-based microrods loaded with single atoms of different metals (iron, cobalt, nickel);

[0071] (3) The single-atom loaded carbon-based microrods MNC / ZrO2 and polyvinylidene fluoride PVDF were mixed in a mass ratio of 1:9 to prepare the composite absorbing material MNC / ZrO2-PVDF.

[0072] MNC / ZrO2 nanorods and PVDF were weighed at a mass ratio of 1:9, with a total mass of 0.1g. PVDF was dissolved in 10mL of N,N-dimethylformamide and sonicated until a transparent mixture was obtained. The MNC / ZrO2 nanorods were then dispersed in the mixture and sonicated until a black suspension was obtained. The prepared mixture was transferred to an evaporating dish and placed in a 70°C oven for 4 hours to evaporate the solvent. MNC / ZrO2-PVDF membranes (900-Fe-CN / ZrO2, 900-Co-CN / ZrO2, and 900-Ni-CN / ZrO2, corresponding to different metal M) were prepared by compression molding with thicknesses of 2mm, 3mm, 4mm, and 5mm.

[0073] The obtained MNC / ZrO2-PVDF membrane was pressed into sheets by hot pressing and the absorption test was performed by coaxial method. Figure 6 As shown, when the sintering temperature is 900℃, the composite material of different metal single atoms has a certain absorption ability, but the excessively high pyrolysis temperature has a higher conductivity, resulting in impedance mismatch, which is consistent with the reflection loss results. The reflection loss intensity is higher than -25dB.

[0074] Figure 7 The best absorption performance in Example 2 was selected for comparison. When the pyrolysis temperature was 800°C and the thickness was 4mm, the composite materials prepared from different single atoms all had relatively ideal absorption performance while effectively regulating the electromagnetic wave absorption frequency of the material. Among them, the reflection loss of Fe-CN / ZrO2 at 5.01GHz was -43.87dB. As the atomic number increased, the frequencies corresponding to the reflection losses of Co-CN / ZrO2 and Ni-CN / ZrO2 gradually shifted to higher frequencies, and the electromagnetic wave absorption intensity also increased further, that is, the reflection loss decreased. The reflection loss of Co-CN / ZrO2 was -44.59dB at 5.22GHz, and the reflection loss of Ni-CN / ZrO2 was -51.10dB at 5.87GHz. The electromagnetic wave absorption frequency was effectively regulated by the type of single atom.

[0075] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may occur depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A method for preparing a material for regulating the absorption frequency of electromagnetic waves by a single atom, characterized in that: The following steps are involved: Step I: Synthesis of the metal-organic framework M-PCN-222 by solvothermal method; Step II: sintering and pyrolyzing the M-PCN-222 obtained in step I in an inert atmosphere to form a single-atom-loaded carbon-based microrod composite material, namely, MNC / ZrO2 nanorods; Step III: The single-atom-loaded carbon-based microrod composite material MNC / ZrO2 nanorod prepared in step II is compounded with a high molecular weight polymer PVDF, and the composite material MNC / ZrO2-PVDF is prepared by ultrasonic method.

2. The method according to claim 1, characterized in that Step I includes the following steps: Tetrakis(4-carboxyphenyl)porphine H2-TCPP and 5,10,15,20-tetrakis(4-carboxyphenyl) metalloporphyrin M-TCPP were placed in DMF in proportion with ZrOCl2·8H2O and CF3COOH, CF3COOH was used to adjust the acidity, and then heated under reflux in an oil bath; After the product is separated, it is washed with DMF and acetone to obtain M-PCN-222; the metal M is selected from iron, cobalt, and nickel; The molar ratio of the total of the H2-TCPP and M-TCPP to the ZrOCl2·8H2O is 1:(8-9), the molar ratio of H2-TCPP to M-TCPP is 3-4:1, and the volume ratio of CF3COOH to DMF solvent is 1:20-25; the temperature range of oil bath heating reflux is 120-130°C.

3. The method according to claim 1, characterized in that In step II: the inert atmosphere is nitrogen or argon, the sintering temperature is 700° C.-900° C., and the sintering time is 2 hours.

4. The method according to claim 3, characterized in that The sintering temperature is 800℃.

5. The method according to claim 1, characterized in that Step III includes: (III-1): The MNC / ZrO2 nanorod material obtained in step II and PVDF are weighed in proportion, and the mass ratio of single-atom-loaded carbon-based microrods MNC / ZrO2 to PVDF is 1:(8-10); (III-2): The weighed PVDF is dissolved in N,N-dimethylformamide and ultrasonically treated until a transparent mixed liquid is obtained. The weighed MNC / ZrO2 nanorod material is added to the transparent mixed liquid and mechanically stirred to obtain a black suspension. The black suspension is then subjected to solvent thermal evaporation to form a film, thereby obtaining a composite membrane MNC / ZrO2-PVDF of single-atom-loaded carbon-based microrods MNC / ZrO2 and PVDF, and the obtained composite membrane has toughness.

6. The method according to claim 5, characterized in that The thickness of the composite membrane MNC / ZrO2-PVDF is 2-5 mm.

7. An electromagnetic wave absorbing material prepared according to the method according to any one of claims 1 to 6.

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