Preparation Method of Magnetic Metal-Loaded Anionic Framework Absorbing Material

Abstract

The present invention discloses a preparation method of a magnetic metal-loaded anion framework microwave absorption material. Taking cobalt ions as an example, first, the precursor MOZ-200 is synthesized through a hydrothermal autoclave, and MOZ-200 is activated by the Soxhlet extraction method or the ethanol immersion method. Then, the activated MOZ-200 is immersed in an ethanol solution of cobalt salt to introduce cobalt ions. Finally, high-temperature heat treatment is carried out under nitrogen to obtain a carbonized magnetic metal-loaded anion framework microwave absorption material. When the thickness of this material is 2.6 mm, RLmin can reach -55.9 dB at 10.64 GHz, and the bandwidth is 4.64 GHz (8.88 GHz - 13.52 GHz).

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic wave absorbing materials, and particularly relates to a preparation method of an anion framework absorbing material loaded with magnetic metal. Background Art

[0002] With the development of the intelligence of electronic products, electromagnetic radiation pollution has entered the public's view, posing a threat to the development of the military and human health. In addition to having good absorption performance for electromagnetic waves, an ideal absorbing material should also have characteristics such as light weight, high temperature resistance, and corrosion resistance. Currently, the materials used for electromagnetic wave absorption mainly include graphene, carbon nanotubes, carbon fibers, ferrites, silicon carbide, etc. The attenuation ability of these absorbing materials with a single dielectric loss or magnetic loss mechanism is limited.

[0003] As a new type of material, metal-organic framework (MOFs) materials form complexes by coordinating metal ions and organic substances. This kind of complex has a porous structure and a relatively high specific surface area. The structure of the complex can be adjusted by adjusting metal particles or changing organic ligands, and it has characteristics such as high stability, adjustable pore size, and large specific surface area, and has a very wide application prospect in the fields of adsorption, separation, and catalytic sensing. There are two absorption mechanisms in electromagnetic wave absorption, one is dielectric loss and the other is magnetic loss. Dielectric loss can be achieved by improving proton conduction, and magnetic loss can act through magnetic particles. MOFs materials can achieve the synergistic effect of dielectric loss and magnetic loss, improving the wave absorption performance of the materials. For example, Professor Cui Yuhong of Northwestern Polytechnical University synthesized bimetallic MOFs (ZIF67@ZIF8) with a core-shell structure by a one-step method, and then prepared heterogeneous trimetallic Co@ZnO / Ni@NC nanocages through the etching of Ni and vacuum carbonization. The synthesized trimetallic components after doping have a synergistic effect, optimizing the impedance matching for the structure design and hollow structure, enhancing the interfacial polarization, and thus improving the absorption performance. The RLmin of Co@ZnO / Ni@NC-60 can reach -55 dB at 8.2 GHz. Due to the characteristics of this synthesized nanocage material, such as multiple synergistic effects, multiple reflection and scattering, enhanced conduction loss ability, strong interfacial polarization and dipole polarization, and good impedance matching, it exhibits excellent electromagnetic wave absorption performance. Therefore, the present invention provides an anion framework absorbing material loaded with magnetic metal with dielectric loss and magnetic loss effects, having the synergistic effect of dielectric loss and magnetic loss, and showing excellent wave absorption performance after heat treatment. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of an anion framework absorbing material loaded with magnetic metal, which solves the problem of poor wave absorption ability of existing composite absorbing materials.

[0005] The technical solution adopted by the present invention is a preparation method of a magnetic metal-loaded anion framework microwave absorbing material, and the specific operation steps are as follows:

[0006] Step 1: Mix tetramethylammonium hydroxide, 5-methyltetrazole, zinc nitrate and terephthalic acid in N,N-dimethylformamide, add them to a reaction kettle for reaction, cool it to room temperature, filter, wash, and dry to obtain a white precursor powder A;

[0007] Step 2: Activate the precursor powder A with a mixed solution of acetonitrile and ethanol by Soxhlet extraction to obtain an activated precursor powder B;

[0008] Step 3: Immerse the precursor powder B in an ethanol solution of cobalt acetate, stir, let it stand, disperse it by ultrasonic wave, and filter to obtain a powder C;

[0009] Step 4: Calcinate the powder C in a tubular furnace to obtain a carbonized powder D, and mix the carbonized powder D with paraffin in different ratios and press it into a ring for subsequent performance testing.

[0010] The characteristics of the present invention also lie in that

[0011] In step 1, the reaction temperature is 100 °C, the reaction time is 48 h, N,N-dimethylformamide is used for washing, and the drying temperature is 60 - 680 °C.

[0012] In step 1, the molar ratio of 5-methyltetrazole, zinc nitrate and terephthalic acid is 1:1:1, and the volume ratio of tetramethylammonium hydroxide to N,N-dimethylformamide is 1:2.5.

[0013] In step 2, the activation temperature is 120 °C, the reaction time is 12 h, and the mixed solution of acetonitrile and ethanol needs to be replaced every 4 h; the activation method can be replaced by soaking in ethanol for 48 h, and the mixed solution of ethanol is replaced every 2 h.

[0014] In step 3, the molar ratio of Co:Zn is 2:1, the stirring time is 1 h, the standing time is 16 - 1.5 h, and the ultrasonic dispersion time is 10 - 6 - 15 min.

[0015] In step 4, the calcination temperature is 900 °C under nitrogen protection, and the heat preservation time is 2 h.

[0016] The synthesis principle of the key steps in the present invention:

[0017] (1) Synthesis of the precursor powder A: The Zn ion is connected with the O atom of one terephthalic acid and the N atoms of three 5-methyltetrazoles through coordination bonds to form a tetrahedral configuration. Each Zn atom is connected by 5-methyltetrazole to form a one-dimensional nanotube containing an eight-membered ring window.

[0018] (2) Activated precursor powder B: The synthesized precursor A is activated to remove the residual reactant molecules and solvent molecules in the crystal framework. The powder B obtained after activating precursor A has a larger specific surface area, which can enhance the interfacial polarization of the material and is beneficial to improving the wave absorption performance.

[0019] (3) Synthesis of powder C: The activated precursor powder B is immersed in an ethanol solution of cobalt acetate, and Co ions are introduced through electrostatic adsorption to form a bimetal-doped complex. Co particles are adsorbed in the cavities rather than on the surface of the polyhedron, which is beneficial to the formation of small-sized and uniformly dispersed cobalt nanoparticles.

[0020] (4) Synthesis of carbonized powder D: The obtained powder C is calcined by a heat treatment method under nitrogen protection to change its morphology. Co particles in-situ replace Zn particles, and at the same time, carbonization makes the surface rough, enhancing the effect of interfacial polarization, and the material is transformed into cobalt carbide / carbon material.

[0021] The beneficial effects of the present invention are as follows:

[0022] (1) The precursor of the anion framework is synthesized by a hydrothermal reaction kettle and activated by a solvent, which increases its specific surface area and is beneficial to improving the wave absorption performance. The operation method is simple, the required solvent is less, the synthesis cost is low, and the safety factor is high.

[0023] (2) The synthesized precursor powder is immersed in a cobalt solution, and cobalt ions are adsorbed into the anion framework through electrostatic action. During high-temperature carbonization, zinc ions are replaced in-situ to form cobalt nanoparticles. During the heat treatment process, Co particles are carbonized and grow cobalt carbide / carbon, making the interior rougher and improving the interfacial polarization ability, which can improve the reflection loss.

[0024] (3) The raw materials used in this method are simple and easy to obtain, the synthesis method adopted is simple, the reproducibility is strong, and the application range is wide. Description of the Drawings

[0025] Figure 1 is the flowchart of the preparation method of the magnetic metal-loaded anion framework wave-absorbing material of the present invention;

[0026] Figure 2 is the X-ray powder diffraction comparison diagram (XRD) of the powder in the present invention;

[0027] Figure 3 is the relationship diagram between the reflection loss values (RL) of different thicknesses and frequencies of the magnetic metal-loaded anion framework wave-absorbing material of the present invention;

[0028] Figure 4 is the absorption bandwidth diagram of the magnetic metal-loaded anion framework wave-absorbing material of the present invention;

[0029] Figure 5 is the comparison chart of the real part of the loss of the magnetic metal-loaded anion framework microwave absorbing material of the present invention;

[0030] Figure 6 is the comparison chart of the imaginary part of the loss of the magnetic metal-loaded anion framework microwave absorbing material of the present invention;

[0031] Figure 7 is the comparison chart of the loss tangent of the magnetic metal-loaded anion framework microwave absorbing material of the present invention. Detailed implementation manners

[0032] The magnetic metal-loaded anion framework microwave absorbing material provided by the present invention includes a zinc template-synthesized porous carbon-based material. After the precursor is activated, magnetic metal ions are introduced through electrostatic assembly during soaking. After high-temperature heat treatment, the magnetic metal ions in-situ replace zinc ions, and after carbonization, it is mixed with paraffin in different proportions and pressed into a ring for testing the microwave absorbing performance.

[0033] The present invention will be further described below in conjunction with specific embodiments.

[0034] Example 1

[0035] The preparation method of the magnetic metal-loaded anion framework microwave absorbing material is as Figure 1 shown. Taking cobalt ions as an example, the specific operation steps are as follows:

[0036] Step 1: Mix 24 drops of tetramethylammonium hydroxide, 5-methyltetrazole, zinc nitrate, and terephthalic acid (molar ratio 1:1:1) in 60 mL of N,N-dimethylformamide, add it to a 100 mL reaction kettle and react for 48 h. Cool it to room temperature, filter, wash with N,N-dimethylformamide, and dry at 60 °C to obtain a white precursor powder A;

[0037] Step 2: Activate the precursor powder A by Soxhlet extraction with a mixed solution of acetonitrile and ethanol. The reaction temperature is 120 °C, the reaction time is 12 h, and the solution is changed every 4 h to obtain an activated precursor powder B;

[0038] Step 3: Soak the precursor powder B in an ethanol solution of cobalt acetate (Co:Zn molar ratio 2:1), stir for 1 h, stand for 1 h, ultrasonically disperse for 10 min, and filter to obtain powder C;

[0039] Step 4: Place the powder C in a tubular furnace, calcine at 900 °C for 2 h under nitrogen protection to obtain a carbonized powder D, mix it with paraffin in different proportions and press it into a ring for subsequent performance testing.

[0040] Example 2

[0041] Step 1: Mix 24 drops of tetramethylammonium hydroxide, 5-methyltetrazole, zinc nitrate, and terephthalic acid (molar ratio 1:1:1) in 60 mL of N,N-dimethylformamide, add it to a 100 mL reaction kettle, react for 48 h, cool it to room temperature, filter, wash with N,N-dimethylformamide, and dry at 70 °C to obtain white precursor powder A;

[0042] Step 2: Activate precursor powder A by Soxhlet extraction with a mixed solution of acetonitrile and ethanol. The reaction temperature is 120 °C, the reaction time is 12 h, and the solution is changed every 4 h to obtain activated precursor powder B;

[0043] Step 3: Immerse precursor powder B in an ethanol solution of cobalt nitrate (Co:Zn molar ratio 2:1), stir for 1 h, let it stand for 1 h, ultrasonically disperse for 15 min, and filter to obtain powder C

[0044] Step 4: Place powder C in a tube furnace, calcine at 900 °C for 2 h under nitrogen protection to obtain carbonized powder D, mix it with paraffin wax in different proportions and press it into a ring for subsequent performance testing.

[0045] Example 3

[0046] Step 1: Mix 24 drops of tetramethylammonium hydroxide, 5-methyltetrazole, zinc nitrate, and terephthalic acid (molar ratio 1:1:1) in 60 mL of N,N-dimethylformamide, add it to a 100 mL reaction kettle, react for 48 h, cool it to room temperature, filter, wash with N,N-dimethylformamide, and dry at 60 °C to obtain white precursor powder A;

[0047] Step 2: Immerse precursor powder A in an ethanol solution for activation. The reaction time is 48 h, and the solution is changed every 2 h to obtain activated precursor powder B;

[0048] Step 3: Immerse precursor powder B in an ethanol solution of manganese chloride (Co:Zn molar ratio 2:1), stir for 1 h, let it stand for 1 h, ultrasonically disperse for 10 min, and filter to obtain powder C

[0049] Step 4: Place powder C in a tube furnace, calcine at 900 °C for 2 h under nitrogen protection to obtain carbonized powder D, mix it with paraffin wax in different proportions and press it into a ring for subsequent performance testing.

[0050] Example 4:

[0051] Step 1: Mix 24 drops of tetramethylammonium hydroxide, 5-methyltetrazole, zinc nitrate, and terephthalic acid (molar ratio 1:1:1) in 60 mL of N,N-dimethylformamide, add it to a 100 mL reaction kettle, react for 48 h, cool it to room temperature, filter, wash with N,N-dimethylformamide, and dry at 60 °C to obtain white precursor powder A;

[0052] Step 2: Activate precursor powder A using a Soxhlet extraction method with a mixed solution of acetonitrile and ethanol. The reaction temperature is 120 °C, the reaction time is 12 h, and the solution is changed every 4 h to obtain activated precursor powder B;

[0053] Step 3: Immerse precursor powder B in an ethanol solution of nickel chloride (Co:Zn molar ratio 2:1), stir for 1.5 h, let it stand for 1.5 h, perform ultrasonic dispersion for 15 min, and filter to obtain powder C;

[0054] Step 4: Place powder C in a tubular furnace, calcine it at 900 °C for 2 h under nitrogen protection to obtain carbonized powder D, mix it with paraffin wax in different proportions and press it into rings for subsequent performance testing.

[0055] Example 5:

[0056] Step 1: Mix 2 drops of tetramethylammonium hydroxide, 5-methyltetrazole, zinc nitrate, and terephthalic acid (molar ratio 1:1:1) in 5 mL of N,N-dimethylformamide, add it to a 10 mL reaction kettle, react for 48 h, cool it to room temperature, filter, wash with N,N-dimethylformamide, and dry at 80 °C to obtain white precursor powder A;

[0057] Step 2: Immerse precursor powder A in an ethanol solution for activation. The reaction time is 48 h, and the solution is changed every 2 h to obtain activated precursor powder B;

[0058] Step 3: Immerse precursor powder B in an ethanol solution of copper sulfate (Co:Zn molar ratio 2:1), stir for 1 h, let it stand for 1 h, perform ultrasonic dispersion for 10 min, and filter to obtain powder C;

[0059] Step 4: Place powder C in a tubular furnace, calcine it at 900 °C for 2 h under nitrogen protection to obtain carbonized powder D, mix it with paraffin wax in different proportions and press it into rings for subsequent performance testing.

[0060] Detailed description of the drawings:

[0061] As Figure 2In the present invention, for the X-ray powder diffraction comparison chart (XRD) of the powder, the peak positions in powders A, B, and C are basically the same, indicating that the main structure has not changed. The structure change of the carbonized powder D is due to the in-situ replacement of magnetic metal in the heat-treated carbonized powder D, and the acting main body has changed.

[0062] As Figure 3 is the relationship diagram between the reflection loss value (RL) and frequency of the magnetic metal-loaded anion framework absorbing material of the present invention with different thicknesses. Usually, when RL < -10 dB, it indicates that 90% of the incident electromagnetic waves are absorbed. The RLmin of the magnetic metal-loaded anion framework absorbing material provided by the present invention can reach -55.9 dB at 10.64 GHz, indicating its good absorbing performance.

[0063] As Figure 4 is the absorption frequency bandwidth diagram of the magnetic metal-loaded anion framework absorbing material of the present invention. At frequencies of 8.88 GHz and 13.52 GHz, the reflection loss RL of the material < -10 dB, indicating that the absorption frequency bandwidth of the modified material is 4.64 GHz.

[0064] As Figure 5 is the comparison chart of the real part of the loss of the magnetic metal-loaded anion framework absorbing material of the present invention. The real part of the loss reflects the storage ability of the material for electromagnetic waves, indicating that the magnetic metal-loaded anion framework absorbing material of the present invention uses electron conduction in the low-frequency band and has good electromagnetic wave energy storage ability. In the case of magnetic conduction, the storage ability in the low-frequency band changes little compared with that in the high-frequency band. Through the comparison of dielectric energy storage and magnetic energy storage, dielectric energy storage dominates.

[0065] As Figure 6 is the comparison chart of the imaginary part of the loss of the magnetic metal-loaded anion framework absorbing material of the present invention. The imaginary part of the loss reflects the loss ability of the stored electromagnetic waves of the material, indicating that the magnetic metal-loaded anion framework absorbing material of the present invention has good dielectric loss ability in the high-frequency band. In the case of magnetic loss, the electromagnetic wave loss ability in the low-frequency band is greater than that in the high-frequency band. Through the comparison of dielectric loss and magnetic loss, the dielectric loss ability dominates.

[0066] As Figure 7 is the comparison chart of the loss tangent of the magnetic metal-loaded anion framework absorbing material of the present invention. The loss tangent value is the ratio of the imaginary part of the loss to the real part of the loss, reflecting the loss ability of the material for incident electromagnetic waves. In the range of 2618 GHz, the dielectric loss tangent is always greater than the magnetic loss tangent, and at high frequencies, the dielectric loss tangent is almost 1, indicating that the dielectric loss ability dominates in the magnetic metal-loaded anion framework absorbing material of the present invention.

Claims

1. Preparation method of magnetic metal-loaded anion framework microwave absorption material, characterized in that, The specific operation steps are as follows: Step 1: Mix tetramethylammonium hydroxide, 5-methyltetrazole, zinc nitrate, and terephthalic acid in N,N-dimethylformamide, add it to a reaction kettle for reaction, cool it to room temperature, filter, wash, and dry to obtain white precursor powder A; The molar ratio of 5-methyltetrazole, zinc nitrate, and terephthalic acid is 1:1:1, and the volume ratio of tetramethylammonium hydroxide to N,N-dimethylformamide is 1:2.5; Step 2: Activate precursor powder A with a mixed solution of acetonitrile and ethanol by Soxhlet extraction to obtain activated precursor powder B; In Step 2, the activation temperature is 120 °C, the reaction time is 12 h, and the mixed solution of acetonitrile and ethanol needs to be replaced every 4 h; the activation method can be replaced by soaking in ethanol for 48 h, and the mixed solution of ethanol is replaced every 2 h; Step 3: Immerse precursor powder B in an ethanol solution of cobalt acetate, stir, let it stand, disperse ultrasonically, and filter to obtain powder C; In Step 3, the molar ratio of Co:Zn is 2:1, the stirring time is 1 h, the standing time is 1 - 1.5 h, and the ultrasonic dispersion time is 10 - 15 min; Step 4: Calcinate powder C in a tube furnace to obtain carbonized powder D, and mix carbonized powder D with paraffin in different ratios and press it into a ring for subsequent performance testing.

2. The preparation method of the magnetic metal-loaded anion framework microwave absorption material according to claim 1, characterized in that, In Step 1, the reaction temperature is 100 °C, the reaction time is 48 h, wash with N,N-dimethylformamide, and the drying temperature is 60 - 80 °C.

3. The preparation method of the magnetic metal-loaded anion framework microwave absorption material according to claim 1, characterized in that, In Step 4, calcine at 900 °C for 2 h under nitrogen protection.

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