Metal-organic framework compound coated composite magnetic wave-absorbing material and preparation method thereof

Abstract

This invention discloses a composite magnetic absorbing material coated with a metal-organic framework compound and its preparation method. The material uses surface-oxidized sheet-like FeSiAl magnetic absorbing powder as the core and a MOF organic framework compound as the coating layer. The MOF organic framework compound is an iron-based framework material MIL-101 (Fe). The mass fraction of the core material is 70-80%, and the mass fraction of the coating layer material is 20-30%, with a total mass fraction of 100. The preparation method is as follows: S1: Ball milling micron-sized water-atomized FeSiAl magnetic powder to obtain sheet-like FeSiAl magnetic powder; S2: Calcination and cooling under an oxygen atmosphere to obtain the core material; S3: Dissolving the surface-oxidized sheet-like FeSiAl magnetic absorbing powder, ferric nitrate nonahydrate, and terephthalic acid in N,N-dimethylformamide (DMF), performing a hydrothermal reaction, and then cooling, filtering, washing, drying, and grinding to obtain the composite magnetic absorbing material coated with a metal-organic framework compound.

Description

Technical Field

[0001] This invention relates to the field of magnetic absorbing materials technology, specifically to a composite magnetic absorbing material coated with a metal-organic framework compound and its preparation method, and more specifically to a FeSiAl composite magnetic absorbing material coated with a metal-organic framework compound (MOF) and its preparation method. Background Technology

[0002] With the rapid development of science and technology, various electronic communication devices are constantly innovating, bringing great convenience to people's lives. However, electromagnetic pollution not only harms the human body but also interferes with the normal operation of precision electronic instruments. Therefore, electromagnetic pollution has become a problem that urgently needs to be solved. In recent years, the development of high-performance microwave absorbing materials with thin thickness, low density, wide effective absorption bandwidth, and strong absorption has become a research hotspot.

[0003] Metal-organic framework (MOF)-derived materials are a novel type of microwave absorbing material, possessing advantages such as simple synthesis process, low production cost, good thermal stability, large specific surface area, and high porosity. Furthermore, the derived porous carbon / magnetic metal particle composite materials overcome the problem of uneven magnetic particle dispersion. High-temperature calcination can produce lightweight porous carbon materials with unique microstructures, thus attracting widespread attention in the field of microwave absorption. Using MOFs as precursors and combining them with magnetic metal alloys is beneficial for synthesizing porous composite materials. These porous composite materials possess well-dispersed nanoparticles and an ordered structure, exhibiting excellent electromagnetic wave absorption performance. However, during the chemical reaction of MOFs with the soft magnetic alloy matrix, the soft magnetic alloy matrix is ​​corroded. Therefore, this invention uses oxidized FeSiAl soft magnetic alloy micropowder as the matrix and then performs in-situ composite with MOFs, protecting the magnetic metal core while improving the microwave absorption performance of the FeSiAl soft magnetic alloy micropowder material. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems by providing a composite magnetic absorbing material coated with metal-organic frameworks (MOFs) and its preparation method. This invention employs a hydrothermal method to composite FeSiAl magnetic powder with MOFs, resulting in a core-shell structured soft magnetic alloy material coated with MOFs. This structure improves the dielectric loss and optimizes the impedance matching of the material, thus significantly enhancing its microwave absorption performance.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A composite magnetic absorbing material coated with a metal-organic framework compound (MOF) consists of a core of surface-oxidized sheet-like FeSiAl magnetic absorbing powder and a coating layer of MOF organic framework compound. The MOF organic framework compound has the unit molecular formula C0. 24 H 12 ClFe3O 13 The iron-based frame material is MIL-101(Fe); the mass fraction of the core material is 70-80, the mass fraction of the cladding material is 20-30, and the sum of the mass fractions of the two is 100.

[0007] As an improvement to the above technical solution, in the surface-oxidized sheet-like FeSiAl magnetic absorbing powder, the mass fraction of Fe is 82, the mass fraction of Si is 10-14, and the mass fraction of Al is 4-8, with the sum of the mass fractions of the three being 100.

[0008] In addition, the present invention also provides a composite magnetic absorbing material coated with the above-mentioned metal-organic framework compound, comprising the following steps:

[0009] S1: Micron-sized water-atomized FeSiAl magnetic powder is ball-milled for 12-36 hours to obtain flake-shaped FeSiAl magnetic powder.

[0010] S2: The sheet-like FeSiAl magnetic powder prepared in step S1 is heated from room temperature to 300-600℃ at a heating rate of 2-5℃ / min under an oxygen atmosphere and calcined for 2-4 hours, and then cooled to room temperature to obtain the core material, which is a sheet-like FeSiAl magnetic microwave absorbing powder with surface oxidation.

[0011] S3: Surface-oxidized flake-shaped FeSiAl magnetic absorbing powder, ferric nitrate nonahydrate (Fe(NO3)3·9H2O), and terephthalic acid (PTA) are sequentially dissolved in N,N-dimethylformamide (DMF). After mechanical stirring until dissolved, a hydrothermal reaction is carried out. After the hydrothermal reaction is completed, the composite magnetic absorbing material coated with metal-organic framework compound is obtained by cooling, filtering, washing, drying, and grinding.

[0012] As an improvement to the above technical solution, the optimal ball milling time is 24 hours.

[0013] As an improvement to the above technical solution, in step S2, the heating rate during oxidation annealing is 5℃ / min, the oxidation annealing temperature is 600℃, and the holding time is 3 hours.

[0014] As an improvement to the above technical solution, in step S2, the oxygen introduced during the oxidation annealing process is always in a flowing state.

[0015] As an improvement to the above technical solution, in step S3, the hydrothermal reaction is carried out at 110–160°C for 12–24 hours.

[0016] As an improvement to the above technical solution, the preparation method further includes step S4, which involves detecting the electromagnetic parameters of the powder material obtained in steps S2 and S3 and calculating the reflectivity RL.

[0017] As an improvement to the above technical solution, the detection method in step S4 is as follows:

[0018] S41. Mix the powder materials obtained in steps S2 and S3 with paraffin wax in a mass ratio of 1:1 to prepare a coaxial sample with an outer diameter of 7 mm, an inner diameter of 3 mm, and a thickness of about 2.5 mm.

[0019] S42. The electromagnetic parameters of the material were tested and the reflectivity was calculated using an Agilent PNA-L5230C vector network analyzer; the complex permeability and complex permittivity of the sample were measured in the 1-18 GHz frequency band.

[0020] S43. The reflectivity RL of the single-layer absorbing material is calculated and simulated using formulas (1) and (2):

[0021]

[0022]

[0023] In the above formula, εr, μr and d are the complex permittivity, complex permeability and thickness of the absorbing material, respectively, f is the frequency of the electromagnetic wave, c is the propagation speed of the electromagnetic wave in vacuum, and j is the imaginary unit.

[0024] Compared with the prior art, the advantages and positive effects of this invention are:

[0025] The metal-organic framework compound-coated composite magnetic absorbing material of the present invention has the characteristics of a core-shell structure. Furthermore, because the metal powder is pre-coated with an oxide layer to form a sheet-like FeSiAl magnetic absorbing powder with an oxidized surface, the soft magnetic alloy matrix will not be eroded during the subsequent MOFs composite process. Therefore, the controllable preparation of highly stable MOFs composite FeSiAl soft magnetic alloy powder is achieved. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 X-ray diffraction pattern of the metal-organic framework compound-coated composite magnetic absorbing material of the present invention;

[0028] Figure 2 The image shows the morphology of the uncoated core material (control sample).

[0029] Figure 3 This is a morphology diagram of the metal-organic framework compound-coated composite magnetic absorbing material of the present invention.

[0030] Figure 4 This is a comparison chart of reflectance RL before and after coating with the metal-organic framework compound in Example 1;

[0031] Figure 5 This is a comparison chart of reflectance RL before and after coating with the metal-organic framework compound in Example 2;

[0032] Figure 6 This is a comparison chart of reflectance RL before and after coating with the metal-organic framework compound in Example 3;

[0033] Figure 7 This is a comparison chart of reflectance RL before and after coating with the metal-organic framework compound in Example 4;

[0034] Figure 8 This is a comparison chart of reflectance RL before and after coating with the metal-organic framework compound in Example 5;

[0035] Figure 9 This is a comparison chart of reflectance RL before and after coating with the metal-organic framework compound in Example 6;

[0036] Figure 10 This is a comparison chart of reflectance RL before and after coating with the metal-organic framework compound in Example 7;

[0037] Figure 11 This is a comparison chart of reflectance RL before and after coating with the metal-organic framework compound in Example 8;

[0038] Figure 12 This is a comparison chart of reflectance (RL) before and after coating with the metal-organic framework compound in Example 9. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art to all other embodiments obtained without creative effort should be included within the protection scope of the present invention.

[0040] Example 1

[0041] In this embodiment, the MOFs are MIL-101(Fe), and the unit molecular formula of MIL-101(Fe) is C0. 24 H 12 ClFe3O 13 .

[0042] This embodiment includes a composite magnetic absorbing material coated with a metal-organic framework compound. The core of the material is 80 wt% FeSiAl, and the coating layer is 20 wt% MOF organic framework compound. The mass percentages of Fe, Si, and Al are 82 wt%, 12 wt%, and 6 wt%, respectively.

[0043] This embodiment also includes a method for preparing a composite magnetic microwave absorbing material coated with a metal-organic framework compound, comprising the following steps:

[0044] Step 1: The readily available micron-sized water-atomized FeSiAl soft magnetic alloy powder is ball-milled for 24 hours to obtain flake-shaped FeSiAl soft magnetic alloy powder.

[0045] Step S2: Place the flake-shaped FeSiAl magnetic powder obtained in step S1 into a quartz tube and evacuate it in a tube furnace. Then fill it with oxygen until the gas pressure inside the quartz tube reaches atmospheric pressure. Then, keep the oxygen flowing into the quartz tube at a flow rate of 0.1 L / min. Then, raise the temperature from room temperature to 500℃ at a heating rate of 5℃ / min and calcine for 3 hours. Then, let it cool naturally to room temperature to obtain the core. The core is a flake-shaped FeSiAl magnetic microwave absorbing powder with surface oxidation.

[0046] Step S3: Hydrothermal Coating: 1g of the FeSiAl magnetic powder microwave absorbing material obtained in Step S2, 0.426g of ferric nitrate nonahydrate (Fe(NO3)3·9H2O), and 0.175g of terephthalic acid (PTA) were dissolved sequentially in 40ml of N,N-dimethylformamide (DMF). The mixture was then mechanically stirred at 320r / min for 30 minutes, and transferred to a stainless steel reactor lined with polytetrafluoroethylene. The reactor was then placed in a constant-temperature drying oven at 110℃ for 24 hours. After the reactor cooled to room temperature, the reaction product was centrifuged and washed three times with DMF and anhydrous ethanol, respectively. It was then dried in a vacuum drying oven at 60℃ for 12 hours. After grinding, flake-shaped FeSiAl composite MOFs magnetic powder was obtained. The microwave absorption performance was as follows: Figure 4 As shown.

[0047] Example 2

[0048] In this embodiment, the MOFs are MIL-101(Fe), and the unit molecular formula of MIL-101(Fe) is C0. 24 H 12 ClFe3O 13 .

[0049] This embodiment includes a composite magnetic absorbing material coated with a metal-organic framework compound. The core of the material is 75 wt% FeSiAl, and the coating layer is 25 wt% MOFs organic framework compound. The mass percentages of Fe, Si, and Al are 82 wt%, 12 wt%, and 6 wt%, respectively. Other aspects are the same as in Example 1. The resulting composite magnetic absorbing material coated with a metal-organic framework compound exhibits the following absorption performance: Figure 5 As shown.

[0050] Example 3

[0051] In this embodiment, the MOFs are MIL-101(Fe), and the unit molecular formula of MIL-101(Fe) is C0. 24 H 12 ClFe3O 13 .

[0052] This embodiment includes a composite magnetic absorbing material coated with a metal-organic framework compound. The core of the material is 70 wt% FeSiAl, and the coating layer is 30 wt% MOFs organic framework compound. The mass percentages of Fe, Si, and Al are 82 wt%, 12 wt%, and 6 wt%, respectively. Other aspects are the same as in Example 1. The resulting composite magnetic absorbing material coated with a metal-organic framework compound exhibits the following absorption performance: Figure 6 As shown.

[0053] Example 4

[0054] In this embodiment, the MOFs are MIL-101(Fe), and the unit molecular formula of MIL-101(Fe) is C0. 24 H 12 ClFe3O 13 .

[0055] This embodiment includes a composite magnetic absorbing material coated with a metal-organic framework compound. The core of the material is 80 wt% FeSiAl, and the coating layer is 20 wt% MOFs organic framework compound. The mass percentages of Fe, Si, and Al are 82 wt%, 10 wt%, and 8 wt%, respectively. Other aspects are the same as in Example 1. The resulting composite magnetic absorbing material coated with a metal-organic framework compound exhibits the following absorption performance: Figure 7 As shown.

[0056] Example 5

[0057] In this embodiment, the MOFs are MIL-101(Fe), and the unit molecular formula of MIL-101(Fe) is C0. 24 H 12 ClFe3O 13 .

[0058] This embodiment includes a composite magnetic absorbing material coated with a metal-organic framework compound. The core of the material is 75 wt% FeSiAl, and the coating layer is 25 wt% MOFs organic framework compound. The mass percentages of Fe, Si, and Al are 82 wt%, 10 wt%, and 8 wt%, respectively. Other aspects are the same as in Example 1. The resulting composite magnetic absorbing material coated with a metal-organic framework compound exhibits the following absorption performance: Figure 8 As shown.

[0059] Example 6

[0060] In this embodiment, the MOFs are MIL-101(Fe), and the unit molecular formula of MIL-101(Fe) is C0. 24 H 12 ClFe3O 13 .

[0061] This embodiment includes a composite magnetic absorbing material coated with a metal-organic framework compound. The core of the material is 70 wt% FeSiAl, and the coating layer is 30 wt% MOFs organic framework compound. The mass percentages of Fe, Si, and Al are 82 wt%, 10 wt%, and 8 wt%, respectively. Other aspects are the same as in Example 1. The resulting composite magnetic absorbing material coated with a metal-organic framework compound exhibits the following absorption performance: Figure 9 As shown.

[0062] Example 7

[0063] In this embodiment, the MOFs are MIL-101(Fe), and the unit molecular formula of MIL-101(Fe) is C0. 24 H 12 ClFe3O 13 .

[0064] This embodiment includes a composite magnetic absorbing material coated with a metal-organic framework compound. The core of the material is 80 wt% FeSiAl, and the coating layer is 20 wt% MOFs organic framework compound. The mass percentages of Fe, Si, and Al are 82 wt%, 14 wt%, and 4 wt%, respectively. Other aspects are the same as in Example 1. The resulting composite magnetic absorbing material coated with a metal-organic framework compound exhibits the following absorption performance: Figure 10 As shown.

[0065] Example 8

[0066] In this embodiment, the MOFs are MIL-101(Fe), and the unit molecular formula of MIL-101(Fe) is C0. 24 H 12 ClFe3O 13 .

[0067] This embodiment includes a composite magnetic absorbing material coated with a metal-organic framework compound. The core of the material is 75 wt% FeSiAl, and the coating layer is 25 wt% MOFs organic framework compound. The mass percentages of Fe, Si, and Al are 82 wt%, 14 wt%, and 4 wt%, respectively. Other aspects are the same as in Example 1. The resulting composite magnetic absorbing material coated with a metal-organic framework compound exhibits the following absorption performance: Figure 11 As shown.

[0068] Example 9

[0069] In this embodiment, the MOFs are MIL-101(Fe), and the unit molecular formula of MIL-101(Fe) is C0. 24 H 12 ClFe3O 13 .

[0070] This embodiment includes a composite magnetic absorbing material coated with a metal-organic framework compound. The core of the material is 70 wt% FeSiAl, and the coating layer is 30 wt% MOFs organic framework compound. The mass percentages of Fe, Si, and Al are 82 wt%, 14 wt%, and 4 wt%, respectively. Other aspects are the same as in Example 1. The resulting composite magnetic absorbing material coated with a metal-organic framework compound exhibits the following absorption performance: Figure 12 As shown.

[0071] Experimental results:

[0072] The phase composition of the powder absorbing material obtained in step S4 was characterized using a PANalytical-Empyrean X-ray diffractometer, and the results are as follows: Figure 1 As shown.

[0073] The morphology of the powder absorbing materials obtained in steps S2 and S3 was characterized using a Thermo Scientific Apreo 2SEM high-performance field emission scanning electron microscope. The results are as follows: Figure 2 , Figure 3 As shown.

[0074] The electromagnetic parameters of the material were tested and the reflectivity was calculated using an Agilent PNA-L5230C vector network analyzer. The powder materials obtained in steps S2 and S3 were mixed with paraffin wax at a mass ratio of 1:1 to prepare coaxial samples with outer and inner diameters of 7 mm and 3 mm respectively, and a thickness of approximately 2.5 mm. The complex permeability and complex permittivity of the samples were measured in the 1-18 GHz frequency band. The reflectivity RL of the single-layer absorbing material was calculated and simulated using formulas (1) and (2):

[0075]

[0076]

[0077] In the above formula, ε r μ r d and d represent the complex permittivity, complex permeability, and thickness of the absorbing material, respectively; f is the frequency of the electromagnetic wave; c is the propagation speed of the electromagnetic wave in a vacuum; and j is the imaginary unit.

[0078] The absorption performance of Examples 1-9 corresponds sequentially. Figures 4-12 The minimum optimal reflectivity RL is shown in Table 1:

[0079] Table 1: Optimal reflectance values ​​of materials prepared in Examples 1-9

[0080]

[0081] In summary, the reflectivity of the composite magnetic absorbing material coated with a metal-organic framework compound prepared by this invention is greatly optimized. Because the metal powder is pre-coated with an oxide layer after oxidative heat treatment to form a sheet-like FeSiAl magnetic absorbing powder with an oxidized surface, the soft magnetic alloy matrix is ​​not corroded during the subsequent in-situ composite with MOFs, thus improving the material's stability and corrosion resistance. This is more beneficial for its practical applications and industrial production requirements, and therefore has good development prospects and application value.

Claims

1. A composite magnetic microwave absorbing material coated with a metal-organic framework compound, characterized in that: The core is a sheet-like FeSiAl magnetic absorbing powder with surface oxidation, and the coating is a MOF (Metal-Organic Framework) compound. The MOF compound has the molecular formula C 24 H 12 ClFe3O 13 The iron-based framework material MIL-101 (Fe) consists of a core material comprising 70–80 parts by mass, a cladding material comprising 20–30 parts by mass, and a total of 100 parts by mass. The surface-oxidized sheet-like FeSiAl magnetic absorbing powder comprises 82 parts by mass of Fe, 10–14 parts by mass of Si, and 4–8 parts by mass of Al, with a total of 100 parts by mass of all three.

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