Layered compound and magnetic graphite composite microwave absorbing material and preparation method thereof

Abstract

The present application provides a layered compound and magnetic graphite composite microwave absorbing material and a preparation method thereof. The preparation method includes adding a ferric salt and a graphite material into an alcohol solution, stirring and ultrasonically treating until uniformly dispersed to obtain a first mixed solution; putting the first mixed solution into a hydrothermal reaction kettle, heating and reacting for a period of time, filtering, washing and drying after cooling to obtain a magnetic graphite material; dispersing 2-methylimidazole, a metal salt and the magnetic graphite material in deionized water, and mechanically stirring to obtain a second mixed solution; standing and aging the second mixed solution, and drying the precipitate to obtain the layered compound and magnetic graphite composite microwave absorbing material. The preparation method provided by the present application and the layered compound and magnetic graphite composite microwave absorbing material prepared thereby have good microwave absorbing characteristics, low preparation cost and will not cause environmental pollution.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing microwave absorbing materials based on graphite nanosheets. Specifically, a layered compound and magnetic graphite composite microwave absorbing material and a preparation method thereof are provided. Background Art

[0002] In recent years, novel carbon-based composite microwave absorbing materials represented by graphene have become a research hotspot in the field of preparing novel microwave absorbing materials. Graphene is a typical two-dimensional dielectric loss type microwave absorbing material, which has advantages such as low density, large surface area, extremely high dielectric properties, high thermal stability and chemical stability.

[0003] Since the microwave absorption mechanism of a single material is limited, it often cannot take into account both dielectric loss and magnetic loss, and its performance is also poor when used as a microwave absorbing material. Therefore, the currently common microwave absorbing materials are multi-component composite materials to comprehensively utilize the microwave absorption characteristics of materials with different properties. For example, magnetic metal oxides such as Fe3O4 have magnetism and can absorb electromagnetic waves through mechanisms such as hysteresis loss, eddy current loss and natural resonance effect; imidazole zeolite framework materials (ZIF) are a class of novel materials with a layered structure formed by the self-assembly of metal ions and organic imidazole esters through cross-linking interactions. ZIF materials have advantages such as good thermal stability, large specific surface area and high porosity.

[0004] However, due to the relatively complex preparation process of graphene, the cost advantage is not obvious when using it to prepare carbon-based composite microwave absorbing materials; at the same time, in the process of preparing composite microwave absorbing materials using multiple materials, if the preparation process cannot be reasonably planned, or the specific composition and ratio of the selected materials are unreasonable, it is impossible to design and prepare composite materials with complex and diverse microstructures. Not only can impedance matching not be coordinated, so that the characteristics of each material cannot be coupled with each other to play a synergistic effect, but it may even lead to a decrease in the overall performance of the prepared product and an increase in the preparation cost; in addition, the preparation of existing ZIF materials generally uses fluorides to regulate the microstructure. Since fluorides have strong corrosiveness and destructiveness, they may also cause unnecessary environmental pollution.

[0005] Therefore, there is a need to provide a preparation method with a reasonable preparation process, reasonable components and ratios to maximize the characteristics of each material and form a synergistic effect, and by regulating the micro-morphology of the prepared composite microwave absorbing material, a composite microwave absorbing material with good electromagnetic wave absorption characteristics is obtained. Summary of the Invention

[0006] The purpose of the present application is to solve the problems existing in the above-mentioned prior art, and provide a composite material of graphite nanosheets modified by a layered compound and magnetic Fe3O4 particles and a preparation method thereof, and improve the electromagnetic wave absorption characteristics of a single component of graphite nanosheets through special means of regulating the micro-morphology.

[0007] One aspect of the present application provides a method for preparing a layered compound and magnetic graphite composite absorbing material, comprising the following steps:

[0008] (1) Add a ferric salt and a graphite material into an alcohol solution, stir and ultrasonically treat until uniformly dispersed to obtain a first mixed solution;

[0009] (2) Put the first mixed solution into a hydrothermal reaction kettle, heat and react for a period of time, and after cooling, filter, wash and dry to obtain a magnetic graphite material modified with magnetic Fe3O4 particles;

[0010] (3) Disperse 2-methylimidazole, a metal salt and the magnetic graphite material in deionized water, and obtain a second mixed solution after mechanical stirring;

[0011] (4) After the second mixed solution is allowed to stand and age, take the precipitate and dry it to obtain a layered compound and magnetic graphite composite absorbing material.

[0012] Preferably, the preparation method further comprises the following steps:

[0013] (5) Calcinate the layered compound and magnetic graphite composite absorbing material in a muffle furnace to improve the absorbing performance of the material.

[0014] Furthermore, the layered compound and magnetic graphite composite absorbing material has a microscopic morphological structure with layered pores and combined iron oxides attached to the surface of the graphite material.

[0015] Preferably, the magnetic Fe3O4 particles have a solid and / or hollow spherical morphology.

[0016] Preferably, in step (1), the ferric salt is ferric nitrate and / or ferric chloride, and the graphite material is graphite nanosheets acidified with concentrated nitric acid and / or reduced graphene oxide; the thickness of the graphite nanosheets acidified with concentrated nitric acid is less than or equal to 3 nm.

[0017] Preferably, in step (1), the alcohol solution is at least one of an ethylene glycol solution, an isopropyl alcohol solution, and a mixed solution of deionized water and alcohol, wherein the volume ratio of deionized water to alcohol in the mixed solution of deionized water and alcohol is 1:20 to 1:30.

[0018] Preferably, the alcohol solution in step (1) further contains a dispersant PVP (polyvinylpyrrolidone), sodium acetate, and urea.

[0019] Preferably, in step (2), the heating temperature of the first mixed solution is 180 to 200 °C, and the time is 8 to 10 hours.

[0020] Preferably, the metal salt in step (3) is a salt containing at least one of zinc, cobalt, and nickel metal ions.

[0021] Preferably, the temperature of the calcination in step (5) is 250 - 400 °C, and the time is 0.5 - 1 hour.

[0022] Another aspect of the present application provides a layered compound and magnetic graphite composite absorbing material, which is prepared according to the preparation method of the above-mentioned layered compound and magnetic graphite composite absorbing material.

[0023] The layered compound and magnetic graphite composite absorbing material provided by the present application has at least the following beneficial effects:

[0024] In the preparation method of the composite absorbing material provided by the present application, first, a solvothermal method is used to generate a composite material of Fe3O4 microparticles and graphite nanosheets, and the Fe3O4 microparticles are made into a solid or hollow structure by adjusting the solvent formula; due to the introduction of magnetic particles, the magnetic loss performance of the composite material is improved, and the absorbing performance of the composite material is greatly enhanced.

[0025] In the preparation method of the composite absorbing material provided by the present application, the formation of a layered ZIF structure is realized through the ZIF template method, and the metal ions and organic substances are assembled and deposited by static aging to form a composite of ZIF material and Fe3O4 microparticle-modified graphite nanosheets; further, the metal ions are oxidized to metal oxides by high-temperature calcination, while the organic framework is retained to form a layered porous structure. The layered microstructure combines with iron oxide microparticles, introducing a larger specific surface area and a larger porosity, enabling the composite material to have many interfaces, enhancing the interfacial polarization, and at the same time creating more reflection and refraction interfaces, causing the electromagnetic wave to generate multiple reflections and refractions; coordinating the dielectric loss and magnetic loss to improve the absorbing performance of the composite material.

[0026] Using the above preparation process, the obtained composite absorbing material can achieve mutual coordination among multiple components, achieving a multiple coordination effect of magnetic loss and multiple interfaces, thereby enhancing the absorbing characteristics of the composite material. The synergistic effect of the multi-morphology regulation and magnetic loss of this composite material is significantly superior to that of the absorbing material with a single component of graphite nanosheets, and it does not use fluorides that are likely to cause environmental pollution, improving the safety of the preparation process. Description of the Drawings

[0027] Figure 1 It is a scanning electron microscope image of magnetic graphite nanosheets modified by magnetic Fe3O4 microparticles according to an embodiment of the present application;

[0028] Figure 2 It is a scanning electron microscope image of the layered compound and magnetic graphite composite absorbing material according to an embodiment of the present application;

[0029] Figure 3 is Figure 2 a partially enlarged view;

[0030] Figure 4 is the comparison of the microwave absorption properties of the layered compound and magnetic graphite composite microwave absorption material prepared according to Example 1 of the present application at different thicknesses;

[0031] Figure 5 is the comparison of the microwave absorption properties of the layered compound and magnetic graphite composite microwave absorption material prepared according to Example 2 of the present application at different thicknesses. Specific Embodiments

[0032] Hereinafter, the present application will be further described based on preferred embodiments with reference to the accompanying drawings.

[0033] One aspect of the present application provides a method for preparing a layered compound and magnetic graphite composite microwave absorption material, the method comprising the following steps:

[0034] (1) Add a ferric salt and a graphite material to an alcohol solution, stir and ultrasonically treat until evenly dispersed to obtain a first mixed solution;

[0035] (2) Place the first mixed solution in a hydrothermal reaction kettle, heat and react for a period of time, and after cooling, filter, wash and dry to obtain a magnetic graphite material modified with magnetic Fe3O4 particles;

[0036] (3) Disperse 2-methylimidazole, a metal salt and the magnetic graphite material in deionized water, and mechanically stir to obtain a second mixed solution;

[0037] (4) After the second mixed solution is allowed to stand and age, take the precipitate and dry it to obtain a layered compound and magnetic graphite composite microwave absorption material.

[0038] In some preferred embodiments, the preparation method further comprises step (5): calcine the layered compound and magnetic graphite composite microwave absorption material in a muffle furnace to improve the microwave absorption performance of the material.

[0039] In some preferred embodiments, the ferric salt in step (1) is a ferric salt such as ferric nitrate, ferric chloride, etc., and the graphite material is graphite nanosheets acidified with concentrated nitric acid and / or reduced graphene oxide; the thickness of the graphite nanosheets acidified with concentrated nitric acid is less than or equal to 3 nm. Acidifying the graphite nanosheets with concentrated nitric acid endows the graphite nanosheets with a rich microstructure, which is beneficial to the subsequent attachment of Fe3O4 particles and the combination with the ZIF structure.

[0040] In some preferred embodiments, the alcohol solution in step (1) is at least one of an ethylene glycol solution, an isopropyl alcohol solution, and a mixed solution of deionized water and alcohol. Among them, the volume ratio of deionized water to alcohol in the mixed solution of deionized water and alcohol is 1:20 to 1:30. When using an alcohol solvent, the generated Fe3O4 particles are in the shape of solid small balls, with uniform size, a particle size of about 500 nm, evenly distributed on the graphite nanosheets, and in good adhesion state; when using a mixed solution of alcohol and deionized water, the generated Fe3O4 particles are in the shape of hollow small balls, with uniform size, and in good adhesion to the graphite nanosheets. Figure 1 The electron microscope image of the magnetic graphite nanosheets modified with magnetic Fe3O4 particles is shown. It can be seen from the figure that spherical Fe3O4 particles are attached to the surface of the graphite nanosheets. Due to the introduction of magnetic particles, the magnetic loss performance of the composite material is improved, and the wave absorption performance of the composite material is greatly enhanced.

[0041] In some preferred embodiments, the alcohol solution in step (1) further contains a dispersant PVP (polyvinylpyrrolidone), sodium acetate, and urea.

[0042] In some preferred embodiments, the heating temperature of the first mixed solution in step (2) is 180 - 200 °C, and the time is 8 - 10 hours.

[0043] In some preferred embodiments, the metal salt in step (3) is a salt containing zinc, cobalt, or nickel metal ions, such as zinc chloride, nickel chloride, cobalt chloride, etc.

[0044] In some preferred embodiments, the calcination temperature in step (5) is 250 - 400 °C, and the time is 0.5 - 1 hour.

[0045] Another aspect of the present application provides a layered compound and magnetic graphite composite wave-absorbing material, which is prepared according to the above preparation method of the layered compound and magnetic graphite composite wave-absorbing material. Figure 2 、 Figure 3 The scanning electron microscope image and its partial enlarged view of the layered compound and magnetic graphite composite wave-absorbing material obtained by the above preparation method are respectively shown.

[0046] Through Figure 2 、 Figure 3 It can be seen that the layered compound and magnetic graphite composite wave-absorbing material prepared by the above preparation method has a microscopic morphological structure with layers of pores and combined iron oxides attached to the surface of the graphite material.

[0047] Example 1

[0048] (1) Place 150 mL of ethylene glycol in a beaker and place it on a magnetic stirrer. Add sodium acetate, 1.88 g of ferric chloride hexahydrate, 0.257 g of graphite nanosheets acidified with concentrated nitric acid (thickness less than or equal to 3 nm), urea, and PVP into the ethylene glycol. After mechanical stirring, perform ultrasonic dispersion to dissolve and disperse them evenly to obtain a first mixed solution;

[0049] (2) Put the solution into a hydrothermal reaction kettle and continuously heat it at 200 °C for 8 - 10 hours. After cooling, perform suction filtration, washing, and drying to obtain a magnetic graphite material modified with magnetic Fe3O4 particles;

[0050] (3) Disperse 3.315 g of 2 - methylimidazole, 0.277 g of zinc chloride, and 0.225 g of magnetic graphite material in 150 mL of deionized water and mechanically stir for 4 - 6 hours to obtain a second mixed solution;

[0051] (4) Let the second mixed solution stand and age for 3 - 5 hours, take the precipitate and dry it to obtain a layered compound and magnetic graphite composite wave - absorbing material.

[0052] Example 2

[0053] Place the layered compound and magnetic graphite composite wave - absorbing material prepared in Example 1 in a muffle furnace at 350 °C and calcine for 0.5 hour to improve the wave - absorbing performance of the composite wave - absorbing material.

[0054] Figure 4 Shows the comparison of the wave - absorbing performance of the layered compound and magnetic graphite composite wave - absorbing material prepared in Example 1 at different thicknesses. Figure 5 Shows the comparison of the wave - absorbing performance of the layered compound and magnetic graphite composite wave - absorbing material prepared in Example 2 at different thicknesses.

[0055] Perform wave - absorbing performance testing on the composite wave - absorbing material obtained in Example 1. The result shows that the reflection loss value of the composite material is - 9.007 dB at a thickness of 6 mm. After calcining the composite wave - absorbing material obtained in Example 1 at 350 °C according to Example 2, the reflection loss value of the composite wave - absorbing material is - 41.403 dB at a thickness of 4.9 mm, and the effective wave - absorbing bandwidth below - 10 dB is 3.04 GHz at a thickness range of 5.6 - 5.9 mm. Compared with the uncalcined composite wave - absorbing material and the wave - absorbing performance of single graphite nanosheets, there is a significant improvement in the maximum reflection loss value and the effective wave - absorbing bandwidth. The above improvement in wave - absorbing performance is mainly due to the more obvious layered structure of the composite wave - absorbing material after calcination, which increases the specific surface area of the composite wave - absorbing material, increases the scattering path of electromagnetic waves, enhances interfacial polarization, and thus improves the wave - absorbing performance of the composite material; at the same time, it should be noted that the calcination temperature needs to be controlled within a reasonable range. If the calcination temperature is too high, the layered structure will collapse, weakening the wave - absorbing performance of the composite material.

[0056] Example 3

[0057] (1) Place 150 mL of isopropyl alcohol in a beaker and place it on a magnetic stirrer. Add sodium acetate, 1.88 g of iron(III) nitrate hexahydrate, 0.257 g of graphite nanosheets acidified with concentrated nitric acid, urea, and PVP into the isopropyl alcohol. After mechanical stirring, perform ultrasonic dispersion to dissolve and disperse them evenly to obtain a first mixed solution;

[0058] (2) Put the first mixed solution into a hydrothermal reaction kettle and continuously heat it at 200 °C for 8 - 10 hours. After cooling, perform suction filtration, washing, and drying to obtain a magnetic graphite material modified with magnetic Fe3O4 particles;

[0059] (3) Disperse 3.315 g of 2 - methylimidazole, 0.484 g of nickel chloride, and 0.225 g of magnetic graphite material in 150 mL of deionized water and mechanically stir for 5 hours to obtain a second mixed solution;

[0060] (4) Let the second mixed solution stand and age for 4 hours, take the precipitate and dry it to obtain a layered compound and magnetic graphite composite wave - absorbing material;

[0061] (5) Calcinate the layered compound and magnetic graphite composite wave - absorbing material in a muffle furnace at 400 °C for 0.5 hours to improve the wave - absorbing performance of the material.

[0062] Example 4

[0063] (1) Place a mixed solution of 150 mL of deionized water and alcohol (where the volume ratio of deionized water to alcohol is 1:20 - 1:30) in a beaker and place it on a magnetic stirrer. Add sodium acetate, 1.88 g of iron(III) chloride hexahydrate, 0.257 g of graphite nanosheets, urea, and PVP into the mixed solution of deionized water and alcohol. After mechanical stirring, perform ultrasonic dispersion to dissolve and disperse them evenly;

[0064] (2) Put the solution into a hydrothermal reaction kettle and continuously heat it at 200 °C for 8 - 10 hours. After cooling, perform suction filtration, washing, and drying to obtain a magnetic graphite material modified with magnetic Fe3O4 particles;

[0065] (3) Disperse 3.315 g of 2 - methylimidazole, 0.484 g of cobalt chloride, and 0.225 g of magnetic graphite material in 150 mL of deionized water and mechanically stir for 5 hours to obtain a second mixed solution;

[0066] (4) Let the second mixed solution stand and age for 4 hours, take the precipitate and dry it to obtain a layered compound and magnetic graphite composite wave - absorbing material;

[0067] (5) Place the layered compound and magnetic graphite composite absorbing material in a muffle furnace at 250 °C and calcine for 0.5 hours to improve the absorbing performance of the material.

[0068] Example 5

[0069] (1) Put 145 mL of ethylene glycol and 5 mL of deionized water in a beaker, place it on a magnetic stirrer, add sodium acetate, 1.88 g of ferric chloride hexahydrate, 0.257 g of reduced graphene oxide, urea, and PVP into the ethylene glycol, mechanically stir and then ultrasonically disperse to dissolve and disperse them evenly to obtain a first mixed solution;

[0070] (2) Put the solution into a hydrothermal reaction kettle, continuously heat at 200 °C for 8 - 10 hours, after cooling, filter, wash, and dry to obtain a magnetic graphite material modified with magnetic Fe3O4 particles;

[0071] (3) Disperse 3.315 g of 2 - methylimidazole, 0.277 g of zinc chloride, and 0.225 g of magnetic graphite material in 150 mL of deionized water, mechanically stir for 5 hours to obtain a second mixed solution;

[0072] (4) Let the second mixed solution stand and age for 4 hours, take the precipitate and dry it to obtain a layered compound and magnetic graphite composite absorbing material;

[0073] (5) Place the layered compound and magnetic graphite composite absorbing material in a muffle furnace at 350 °C and calcine for 1 hour to improve the absorbing performance of the material.

[0074] Example 6

[0075] (1) Put 145 mL of ethylene glycol and 5 mL of deionized water in a beaker, place it on a magnetic stirrer, add sodium acetate, 1.88 g of ferric chloride hexahydrate, 0.257 g of graphite nanosheets, urea, and PVP into the ethylene glycol, mechanically stir and then ultrasonically disperse to dissolve and disperse them evenly to obtain a first mixed solution;

[0076] (2) Put the first mixed solution into a hydrothermal reaction kettle, continuously heat at 200 °C for 8 - 10 hours, after cooling, filter, wash, and dry to obtain a magnetic graphite material modified with magnetic Fe3O4 particles;

[0077] (3) Disperse 3.315 g of 2 - methylimidazole, 0.484 g of nickel chloride, and 0.225 g of magnetic graphite material in 150 mL of deionized water, mechanically stir for 5 hours to obtain a second mixed solution;

[0078] (4) Let the second mixed solution stand and age for 4 hours, take the precipitate and dry it to obtain a layered compound and magnetic graphite composite absorbing material;

[0079] (5) Place the layered compound and magnetic graphite composite absorbing material in a muffle furnace at 400 °C and calcine for 1 hour to improve the absorbing properties of the material.

[0080] Example 7

[0081] (1) Put 145 mL of ethylene glycol and 5 mL of deionized water in a beaker and place it on a magnetic stirrer. Add sodium acetate, 1.88 g of ferric chloride hexahydrate, 0.257 g of graphite nanosheets, urea, and PVP to the ethylene glycol. After mechanical stirring, ultrasonically disperse to dissolve and disperse evenly to obtain a first mixed solution.

[0082] (2) Put the first mixed solution into a hydrothermal reaction kettle and continuously heat at 200 °C for 8 - 10 hours. After cooling, filter, wash, and dry to obtain a magnetic graphite material modified with magnetic Fe3O4 particles.

[0083] (3) Disperse 3.315 g of 2-methylimidazole, 0.484 g of cobalt chloride, and 0.225 g of magnetic graphite material in 150 mL of deionized water and mechanically stir for 5 hours to obtain a second mixed solution.

[0084] (4) Let the second mixed solution stand and age for 4 hours, take the precipitate and dry it to obtain a layered compound and magnetic graphite composite absorbing material.

[0085] (5) Place the layered compound and magnetic graphite composite absorbing material in a muffle furnace at 250 °C and calcine for 1 hour to improve the absorbing properties of the material.

[0086] The specific embodiments of the present application have been introduced in detail above. For those skilled in the art of this technology, without departing from the principle of the present application, several improvements and modifications can still be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. Preparation method of layered compound and magnetic graphite composite wave-absorbing material, characterized in that, It includes the following steps: (1) Add ferric salt and graphite material into an alcohol solution, stir and ultrasonically treat until evenly dispersed to obtain a first mixed solution; (2) Put the first mixed solution into a hydrothermal reactor, heat and react for a period of time, after cooling, filter, wash and dry to obtain a magnetic graphite material modified with magnetic Fe3O4 particles; (3) Disperse 2-methylimidazole, metal salt and the magnetic graphite material in deionized water, and obtain a second mixed solution after mechanical stirring; (4) After the second mixed solution is allowed to stand and age, take the precipitate and dry it to obtain a layered compound and magnetic graphite composite absorbing material; (5) Calcinate the layered compound and magnetic graphite composite absorbing material in a muffle furnace to improve the absorbing performance of the material; In step (1), the graphite material is graphite nanosheets acidified with concentrated nitric acid.

2. The preparation method of the layered compound and magnetic graphite composite absorbing material according to claim 1, characterized in that: The layered compound and magnetic graphite composite absorbing material has a microscopic morphological structure with layered pores and combined iron oxides attached to the surface of the graphite material.

3. The preparation method of the layered compound and magnetic graphite composite absorbing material according to claim 1, characterized in that: The magnetic Fe3O4 particles have a solid and / or hollow spherical morphology.

4. The preparation method of the layered compound and magnetic graphite composite absorbing material according to claim 1, characterized in that: In step (1), the ferric salt is ferric nitrate and / or ferric chloride; The thickness of the graphite nanosheets acidified with concentrated nitric acid is less than or equal to 3 nm.

5. The preparation method of the layered compound and magnetic graphite composite absorbing material according to claim 1, characterized in that: In step (1), the alcohol solution is at least one of ethylene glycol solution, isopropyl alcohol solution and a mixed solution of deionized water and alcohol, wherein the volume ratio of deionized water to alcohol in the mixed solution of deionized water and alcohol is 1:20 to 1:

30.

6. The preparation method of the layered compound and magnetic graphite composite absorbing material according to claim 1, characterized in that: In step (2), the heating temperature of the first mixed solution is 180-200 °C and the time is 8-10 hours.

7. The preparation method of the layered compound and magnetic graphite composite absorbing material according to claim 1, characterized in that: In step (3), the metal salt is a salt containing at least one of zinc, cobalt and nickel metal ions.

8. The preparation method of the layered compound and magnetic graphite composite absorbing material according to claim 1, characterized in that: In step (5), the calcination temperature is 250-400 °C and the time is 0.5-1 hour.

9. A layered compound and magnetic graphite composite absorbing material, characterized in that: The layered compound and magnetic graphite composite absorbing material is prepared according to the preparation method of the layered compound and magnetic graphite composite absorbing material described in any one of claims 1 to 8.

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