Preparation method of silver-doped cobalt-based boron imidazole porous carbon wave-absorbing material

Abstract

The application discloses a preparation method of silver-doped cobalt-based boron imidazole porous carbon wave-absorbing material, and synthesizes cobalt-based boron imidazole nanospheres through a hydrothermal method, loads silver on the cobalt-based boron imidazole nanospheres through a method of ultraviolet lamp reduction by taking the cobalt-based boron imidazole as a carrier, and obtains the silver-doped cobalt-based boron imidazole porous carbon wave-absorbing material. The cobalt-based boron imidazole nanospheres are prepared into cobalt-based porous carbon material through heat treatment, the dielectric loss of the material is improved due to the formation of a conductive network, and the multiple scattering and reflection of electromagnetic waves in the material are increased due to the pore structure, so that the wave-absorbing performance of the material is improved. The silver ions are reduced into silver particles through the method of ultraviolet lamp reduction, the silver is deposited on the surface of the cobalt-based porous carbon, the conductivity of the material is increased, and the dielectric loss and magnetic loss of the material are further improved.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials technology, specifically relating to a method for preparing silver-doped cobalt-based boron imidazole porous carbon absorbing materials. Background Technology

[0002] With the development of technology, various household appliances and mobile phones are becoming increasingly widespread, leading to increasingly serious electromagnetic radiation pollution. Electromagnetic radiation not only interferes with the normal operation of other instruments, causing malfunctions and signal interruptions, but it also seriously damages human health, easily triggering various diseases such as cancer and endocrine disorders. Therefore, it is urgent to develop high-performance electromagnetic wave absorbing materials to address the hazards of electromagnetic radiation. Absorbing materials can convert electromagnetic waves into heat or other forms of energy dissipation, thus effectively absorbing electromagnetic waves. Because it can fundamentally weaken electromagnetic waves, developing high-performance electromagnetic wave absorbing materials with a large effective absorption bandwidth and good stability is of great significance, which has attracted the research interest of many researchers.

[0003] Currently, the more mature microwave absorbing materials include ferrite, barium titanate, silicon carbide, graphite, and conductive fibers. While these materials are inexpensive and technologically mature, their single composition and limitations in impedance matching performance, absorption bandwidth, absorption intensity, and material quality often fail to meet requirements, severely impacting practical application performance. Therefore, to meet increasingly demanding requirements, composite microwave absorbing materials have emerged.

[0004] Metal-organic frameworks (MOFs) are porous hybrid materials that are self-assembled from metal ions and organic ligands. They can provide abundant carbon sources and enable the doping of metal nano-ions in carbon channels, thereby effectively controlling the electromagnetic properties of the materials and obtaining excellent carbon-based microwave absorbing materials. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing silver-doped cobalt-based boron imidazole porous carbon microwave absorbing materials, which solves the problems of poor impedance matching performance and weak absorption capacity of existing electromagnetic wave absorbing materials.

[0006] The technical solution adopted in this invention is a method for preparing silver-doped cobalt-based boron imidazole porous carbon microwave absorbing material. This involves synthesizing cobalt-based boron imidazole nanospheres via a hydrothermal method, using cobalt-based boron imidazole as a carrier, carbonizing it at high temperature to form cobalt-based boron imidazole porous carbon, and finally loading silver onto the cobalt-based boron imidazole porous carbon using a UV lamp reduction method to obtain the silver-doped cobalt-based boron imidazole porous carbon microwave absorbing material. The specific operation steps are as follows:

[0007] Step 1: Weigh KBH4 solid and stir thoroughly to obtain substance A; weigh 2-methylimidazole solid and stir thoroughly to obtain substance B;

[0008] Step 2: Thoroughly mix substance A and substance B from Step 1, while refluxing and stirring, and cool to room temperature to obtain blocky solid C;

[0009] Step 3: Transfer the blocky solid C from Step 2 to a stainless steel reactor lined with polytetrafluoroethylene, then add tricresyl ether, cobalt nitrate hexahydrate, 2-imidazolidine ketone, N,N-dimethylformamide, and ethanol. Heat the mixture to react, and after natural cooling, separate the product by filtration. After washing, drying, and grinding, obtain product D.

[0010] Step 4: Place product D in a ceramic boat and heat-treat it in a temperature-controlled tube furnace under a nitrogen atmosphere. Then, allow it to cool naturally to room temperature to obtain cobalt-based boron imidazole powder E.

[0011] Step 5: Dissolve powder E in deionized water and sonicate to obtain solution F; dissolve AgNO3 in deionized water and sonicate to obtain solution G; add solution G to solution F and continue sonicating to obtain mixed solution H.

[0012] Step 6: Irradiate the mixed solution H with a 365nm ultraviolet lamp, collect the product by centrifugation, and dry it to obtain silver-doped cobalt-based boron imidazole porous carbon microwave absorbing material, i.e., product I;

[0013] Step 7: Mix product I obtained in step 6 with carbon nanotubes and paraffin, press it into a ring under a specific mold, and finally test its electromagnetic wave absorption performance.

[0014] The invention is further characterized in that,

[0015] In step 1, the mass ratio of KBH4 to 2-methylimidazole is 1:5.

[0016] In step 2, the reflux stirring time is 1 to 3 hours.

[0017] In step 3, the heating temperature is 80℃~120℃, and the temperature is maintained for 72h~120h.

[0018] The heat treatment process in step 4 is as follows: heat to 800-1000℃ at a heating rate of 5-10℃ / min and hold for 2-4 hours.

[0019] In step 5, the mass ratio of AgNO3 to powder E is 0.085:1.

[0020] In step 6, the UV lamp irradiation time is 10 min to 4 h.

[0021] The beneficial effects of this invention are:

[0022] (1) Cobalt-based boron imidazole nanospheres were synthesized by hydrothermal method. Due to their extremely high specific surface area and designability, and the fact that the nanospheres contain abundant carbon and cobalt sources, they provide a basis for the next step of synthesizing porous carbon composite materials through heat treatment.

[0023] (2) Cobalt-based boron imidazole nanospheres were prepared into cobalt-based porous carbon materials by heat treatment. Due to the formation of the conductive network, the dielectric loss of the material was improved. Due to the pore structure, the electromagnetic waves were multi-scattered and reflected inside the material, which improved the absorption performance of the material. Also, due to the characteristics of multiple active sites on its surface, it provided conditions for the next step of loading silver.

[0024] (3) By using ultraviolet lamp reduction, silver ions are reduced to silver particles, and silver is deposited on the surface of cobalt-based porous carbon, which increases the conductivity of the material and further improves the dielectric loss and magnetic loss of the material. Attached Figure Description

[0025] Figure 1 This is a flowchart of the preparation method of the silver-doped cobalt-based porous carbon microwave absorbing material of the present invention.

[0026] Figure 2 This is the XRD pattern of the silver-doped cobalt-based porous carbon microwave absorbing material of the present invention.

[0027] Figure 3 This is a reflection loss diagram of the silver-doped cobalt-based porous carbon microwave absorbing material of the present invention at different thicknesses.

[0028] Figure 4 This is a diagram showing the real part of the dielectric loss of the silver-doped cobalt-based porous carbon microwave absorbing material of the present invention;

[0029] Figure 5 This is the imaginary part diagram of the dielectric loss of the silver-doped cobalt-based porous carbon microwave absorbing material of the present invention.

[0030] Figure 6 This is a diagram showing the dielectric loss tangent of the silver-doped cobalt-based porous carbon microwave absorbing material of the present invention.

[0031] Figure 7 This is a diagram showing the real part of the magnetic loss of the silver-doped cobalt-based porous carbon absorbing material of the present invention.

[0032] Figure 8 This is a diagram showing the imaginary part of the magnetic loss of the silver-doped cobalt-based porous carbon microwave absorbing material of the present invention.

[0033] Figure 9 This is a graph showing the magnetic loss tangent of the silver-doped cobalt-based porous carbon microwave absorbing material of the present invention. Detailed Implementation

[0034] The present invention provides a method for preparing silver-doped cobalt-based boron imidazole porous carbon microwave absorbing material: cobalt-based boron imidazole nanospheres are synthesized by hydrothermal method, cobalt-based boron imidazole is used as a carrier and carbonized at high temperature to form cobalt-based boron imidazole porous carbon, and finally silver is loaded onto cobalt-based boron imidazole porous carbon by ultraviolet lamp reduction method to obtain silver-doped cobalt-based boron imidazole porous carbon microwave absorbing material.

[0035] The present invention will be further described below with reference to specific embodiments.

[0036] Example 1:

[0037] Preparation methods of silver-doped cobalt-based boron imidazole porous carbon microwave absorbing materials, such as Figure 1 As shown, the specific operation steps are as follows:

[0038] Step 1: Weigh 1.08g of KBH4 solid and pour it into a round-bottom flask, stir thoroughly to obtain substance A; weigh 5.25g of 2-methylimidazole solid and add it to the round-bottom flask, stir thoroughly to obtain substance B;

[0039] Step 2: Mix substance A and substance B from Step 1 thoroughly, while refluxing and stirring for 1 hour, and cool to room temperature to obtain colorless blocky solid C;

[0040] Step 3: Transfer the colorless blocky solid C from Step 2 to a stainless steel reactor lined with polytetrafluoroethylene, then add tricresyl ether, cobalt nitrate hexahydrate, 2-imidazolidineone, N,N-dimethylformamide (DMF), and ethanol. Heat at 80°C for 72 hours. After natural cooling, separate the product by suction filtration. After washing, drying, and grinding, obtain the pink product D.

[0041] Step 4: Place product D in a ceramic boat and place it in a temperature-controlled tube furnace under a nitrogen atmosphere. Heat it to 800°C at a heating rate of 8°C / min, hold it at that temperature for 2 hours, and then let it cool naturally to room temperature to obtain black powder E.

[0042] Step 5: Dissolve powder E in deionized water and sonicate to obtain solution F; dissolve AgNO3 in deionized water and sonicate to obtain solution G; add solution G to solution F and continue sonicating to obtain mixed solution H.

[0043] Step 6: Irradiate the mixed solution H with a 365nm ultraviolet lamp for 10 minutes, centrifuge to collect the product, dry it, and obtain substance I.

[0044] Step 7: Mix product I obtained in step 6 with carbon nanotubes and paraffin, press it into a ring under a specific mold, and test its electromagnetic wave absorption performance.

[0045] Example 2:

[0046] Preparation methods of silver-doped cobalt-based boron imidazole porous carbon microwave absorbing materials, such as Figure 1 As shown, the specific operation steps are as follows:

[0047] Step 1: Weigh 1.08g of KBH4 solid and pour it into a round-bottom flask, stir thoroughly to obtain substance A; weigh 5.25g of 2-methylimidazole solid and add it to the round-bottom flask, stir thoroughly to obtain substance B;

[0048] Step 2: Mix substance A and substance B from Step 1 thoroughly, while refluxing and stirring for 1.5 hours, and cool to room temperature to obtain colorless blocky solid C;

[0049] Step 3: Transfer the colorless blocky solid C from Step 2 to a stainless steel reactor with a polytetrafluoroethylene liner, then add tricresyl ether, cobalt nitrate hexahydrate, 2-imidazolidineone, DMF, and ethanol. Heat at 80°C for 72 hours. After natural cooling, separate the product by suction filtration. After washing, drying, and grinding, obtain the pink product D.

[0050] Step 4: Place product D in a ceramic boat and place it in a temperature-controlled tube furnace under a nitrogen atmosphere. Heat it to 800°C at a heating rate of 8°C / min, hold it at that temperature for 2 hours, and then let it cool naturally to room temperature to obtain black powder E.

[0051] Step 5: Dissolve powder E in deionized water and sonicate to obtain solution F; dissolve AgNO3 in deionized water and sonicate to obtain solution G; add solution G to solution F and continue sonicating to obtain mixed solution H.

[0052] Step 6: Irradiate the mixed solution H with a 365nm ultraviolet lamp for 10 minutes, centrifuge to collect the product, dry it, and obtain substance I.

[0053] Step 7: Mix product I obtained in step 6 with carbon nanotubes and paraffin, press it into a ring under a specific mold, and test its electromagnetic wave absorption performance.

[0054] Example 3:

[0055] Preparation methods of silver-doped cobalt-based boron imidazole porous carbon microwave absorbing materials, such as Figure 1 As shown, the specific operation steps are as follows:

[0056] Step 1: Weigh 1.08g of KBH4 solid and pour it into a round-bottom flask, stir thoroughly to obtain substance A; weigh 5.25g of 2-methylimidazole solid and add it to the round-bottom flask, stir thoroughly to obtain substance B;

[0057] Step 2: Mix substance A and substance B from Step 1 thoroughly, while refluxing and stirring for 1 hour, and cool to room temperature to obtain colorless blocky solid C;

[0058] Step 3: Transfer the colorless blocky solid C from Step 2 to a stainless steel reactor with a polytetrafluoroethylene liner, then add tricresylbenzene, cobalt acetate dihydrate, 2-imidazolidineone, DMF, and ethanol. Heat at 90°C for 72 hours. After natural cooling, separate the product by suction filtration. After washing, drying, and grinding, obtain the pink product D.

[0059] Step 4: Place product D in a ceramic boat and place it in a temperature-controlled tube furnace under a nitrogen atmosphere. Heat it to 800°C at a heating rate of 8°C / min, hold it at that temperature for 2 hours, and then let it cool naturally to room temperature to obtain black powder E.

[0060] Step 5: Dissolve powder E in deionized water and sonicate to obtain solution F; dissolve AgNO3 in deionized water and sonicate to obtain solution G; add solution G to solution F and continue sonicating to obtain mixed solution H.

[0061] Step 6: Irradiate the mixed solution H with a 365nm ultraviolet lamp for 10 minutes, centrifuge to collect the product, dry it, and obtain substance I.

[0062] Step 7: Mix product I obtained in step 6 with carbon nanotubes and paraffin, press it into a ring under a specific mold, and test its electromagnetic wave absorption performance.

[0063] Example 4:

[0064] Preparation methods of silver-doped cobalt-based boron imidazole porous carbon microwave absorbing materials, such as Figure 1 As shown, the specific operation steps are as follows:

[0065] Step 1: Weigh 1.08g of KBH4 solid and pour it into a round-bottom flask, stir thoroughly to obtain substance A; weigh 5.25g of 2-methylimidazole solid and add it to the round-bottom flask, stir thoroughly to obtain substance B;

[0066] Step 2: Mix substance A and substance B from Step 1 thoroughly, while refluxing and stirring for 1 hour, and cool to room temperature to obtain colorless blocky solid C;

[0067] Step 3: Transfer the colorless blocky solid C from Step 2 to a stainless steel reactor with a polytetrafluoroethylene liner, then add tricresyl ether, cobalt nitrate hexahydrate, 2-imidazolidineone, DMF, and ethanol. Heat at 80°C for 72 hours. After natural cooling, separate the product by suction filtration. After washing, drying, and grinding, obtain the pink product D.

[0068] Step 4: Place product D in a ceramic boat and place it in a temperature-controlled tube furnace under a nitrogen atmosphere. Heat it to 800°C at a heating rate of 8°C / min, hold it at that temperature for 2 hours, and then let it cool naturally to room temperature to obtain black powder E.

[0069] Step 5: Dissolve powder E in deionized water and sonicate to obtain solution F; dissolve AgNO3 in deionized water and sonicate to obtain solution G; add solution G to solution F and continue sonicating to obtain mixed solution H.

[0070] Step 6: Irradiate the mixed solution H with a 365nm ultraviolet lamp for 30 minutes, centrifuge to collect the product, dry it, and obtain substance I.

[0071] Step 7: Mix product I obtained in step 6 with carbon nanotubes and paraffin, press it into a ring under a specific mold, and test its electromagnetic wave absorption performance.

[0072] Example 5:

[0073] Preparation methods of silver-doped cobalt-based boron imidazole porous carbon microwave absorbing materials, such as Figure 1 As shown, the specific operation steps are as follows:

[0074] Step 1: Weigh 1.08g of KBH4 solid and pour it into a round-bottom flask, stir thoroughly to obtain substance A; weigh 5.25g of 2-methylimidazole solid and add it to the round-bottom flask, stir thoroughly to obtain substance B;

[0075] Step 2: Mix substance A and substance B from Step 1 thoroughly, while refluxing and stirring for 1 hour, and cool to room temperature to obtain colorless blocky solid C;

[0076] Step 3: Transfer the colorless blocky solid C from Step 2 to a stainless steel reactor with a polytetrafluoroethylene liner, then add tricresyl ether, cobalt nitrate hexahydrate, 2-imidazolidineone, DMF, and ethanol. Heat at 80°C for 72 hours. After natural cooling, separate the product by suction filtration. After washing, drying, and grinding, obtain the pink product D.

[0077] Step 4: Place product D in a ceramic boat and place it in a temperature-controlled tube furnace under a nitrogen atmosphere. Heat it to 800°C at a heating rate of 10°C / min, hold it at that temperature for 3 hours, and then let it cool naturally to room temperature to obtain black powder E.

[0078] Step 5: Dissolve powder E in deionized water and sonicate to obtain solution F; dissolve AgNO3 in deionized water and sonicate to obtain solution G; add solution G to solution F and continue sonicating to obtain mixed solution H.

[0079] Step 6: Irradiate the mixed solution H with a 365nm ultraviolet lamp for 10 minutes, centrifuge to collect the product, dry it, and obtain substance I.

[0080] Step 7: Mix product I obtained in step 6 with carbon nanotubes and paraffin, press it into a ring under a specific mold, and test its electromagnetic wave absorption performance.

[0081] Figure 1This is a flowchart of the preparation method of silver-doped cobalt-based porous carbon microwave absorbing material according to the present invention; silver-doped cobalt-based porous carbon microwave absorbing material can be obtained through a six-step method.

[0082] Figure 2 The image shows the XRD pattern of the silver-doped cobalt-based porous carbon microwave absorbing material of this invention. It can be seen that after loading Ag, the cobalt-based porous carbon exhibits a peak corresponding to the Ag standard card, indicating that silver was successfully loaded onto the cobalt-based porous carbon nanoparticles.

[0083] Figure 3 The diagram shows the reflection loss of the silver-doped cobalt-based porous carbon microwave absorbing material of the present invention at different thicknesses. It can be seen that at 2.5 mm, the reflection loss of the silver-doped cobalt-based porous carbon microwave absorbing material reaches -41 dB, demonstrating good electromagnetic wave absorption performance.

[0084] Figure 4 This is a diagram showing the real part of the dielectric loss of the silver-doped cobalt-based porous carbon microwave absorbing material of the present invention. The real part of the dielectric loss represents the energy storage capacity. In the 2-11 GHz band, the real part of the dielectric loss first remains stable and then decreases. In the 11-18 GHz band, the real part of the dielectric loss gradually increases and reaches its minimum value at 11 GHz, indicating that the energy storage effect is minimal and the dissipation effect is maximum at this point.

[0085] Figure 5 This is a diagram showing the imaginary part of dielectric loss of the silver-doped cobalt-based porous carbon microwave absorbing material of the present invention. The imaginary part of dielectric loss gradually increases in the 2-11 GHz band, decreases and then increases again in the 11-18 GHz band, and reaches its maximum value at 11 GHz, indicating that the electrical dissipation effect is the greatest and the storage effect is the smallest at this point.

[0086] Figure 6 This is a diagram showing the dielectric loss tangent of the silver-doped cobalt-based porous carbon microwave absorbing material of the present invention; representing the dielectric loss capacity, compared with the magnetic loss tangent, the dielectric loss tangent is larger, indicating that the dielectric loss capacity plays a dominant role, which is related to the high conductivity of the material.

[0087] Figure 7 This is a diagram showing the real part of the magnetic loss of the silver-doped cobalt-based porous carbon microwave absorbing material of the present invention. The real part of the magnetic loss is relatively stable at 2-12 GHz and then decreases slowly. The magnetic loss increases slowly at 12-18 GHz. The imaginary part of the magnetic loss reaches its minimum value at 12 GHz, indicating that the magnetic storage effect is minimal and the dissipation effect is maximum at this point.

[0088] Figure 8 This is a diagram of the imaginary part of magnetic loss of the silver-doped cobalt-based porous carbon microwave absorbing material of the present invention. The imaginary part of magnetic loss gradually increases from 2 to 12 GHz and gradually decreases from 12 to 18 GHz. The imaginary part of magnetic loss reaches its maximum value at 12 GHz, indicating that the magnetic dissipation effect is the greatest and the storage effect is the smallest at this point.

[0089] Figure 9 This is a graph showing the magnetic loss tangent of the silver-doped cobalt-based porous carbon absorbing material of this invention; representing the capacity of magnetic loss.

[0090] This invention first prepares cobalt-based boron imidazole nanospheres via a hydrothermal method. Due to their extremely high specific surface area and designability, and the abundance of carbon and cobalt sources within the nanospheres, a foundation is laid for the subsequent synthesis of porous carbon composite materials through heat treatment. Then, cobalt-based porous carbon materials are obtained through high-temperature carbonization. The formation of a conductive network improves the dielectric loss of the material, and the porous structure increases the multiple scattering and reflection of electromagnetic waves within the material, enhancing its microwave absorption performance. Furthermore, the multiple active sites on its surface provide conditions for the subsequent loading of silver. Finally, silver-doped cobalt-based porous carbon microwave absorbing materials are obtained using a UV lamp reduction method, uniformly loading silver in situ into the pores, further increasing its conductivity. At a frequency of 12.1 GHz and a thickness of 2.5 mm, the minimum RL value is -40.1 dB.

Claims

1. A method for preparing silver-doped cobalt-based boron imidazole porous carbon microwave absorbing material, characterized in that, Cobalt-based boron imidazole nanospheres were synthesized via a hydrothermal method. Cobalt-based boron imidazole was then used as a support and carbonized at high temperature to form cobalt-based boron imidazole porous carbon. Finally, silver was loaded onto the cobalt-based boron imidazole porous carbon using a UV lamp reduction method to obtain a silver-doped cobalt-based boron imidazole porous carbon microwave absorbing material. The specific operational steps are as follows: Step 1: Weigh KBH4 solid and stir thoroughly to obtain substance A; weigh 2-methylimidazole solid and stir thoroughly to obtain substance B; The mass ratio of KBH4 to 2-methylimidazole is 1:5; Step 2: Thoroughly mix substance A and substance B after stirring in Step 1, then reflux and stir. After mixing evenly, cool to room temperature to obtain block solid C. Step 3: Transfer the blocky solid C from Step 2 to a stainless steel reactor lined with polytetrafluoroethylene, then add tricresyl ether, cobalt nitrate hexahydrate, 2-imidazolidineone, N,N-dimethylformamide, and ethanol. React at high temperature in an oven. After natural cooling, separate the product by filtration. After washing, drying, and grinding, obtain product D. Step 4: Place product D in a ceramic boat and heat-treat it in a programmable temperature-controlled tube furnace under a nitrogen atmosphere. Then, allow it to cool naturally to room temperature to obtain cobalt-based boron imidazole porous carbon powder E. The heat treatment process in step 4 is as follows: heat to 800~1000℃ at a heating rate of 5-10℃ / min, and hold for 2~4 hours; Step 5: Dissolve powder E in deionized water and sonicate to obtain solution F; dissolve AgNO3 in deionized water and sonicate to obtain solution G; add solution G to solution F and continue sonication to obtain mixed solution H; In step 5, the mass ratio of AgNO3 to powder E is 0.085:1; Step 6: Irradiate the mixed solution H with a 365nm ultraviolet lamp, collect the product by centrifugation, and dry it to obtain silver-doped cobalt-based boron imidazole porous carbon microwave absorbing material, i.e., product I; Step 7: Mix product I obtained in step 6 with carbon nanotubes and paraffin wax in different proportions, press the mixture into a mold ring, and finally test its electromagnetic wave absorption performance.

2. The method for preparing the silver-doped cobalt-based boron imidazole porous carbon microwave absorbing material according to claim 1, characterized in that, In step 2, the reflux stirring time is 1 to 3 hours.

3. The method for preparing the silver-doped cobalt-based boron imidazole porous carbon microwave absorbing material according to claim 1, characterized in that, In step 3, the heating temperature is 80℃-120℃, and the temperature is maintained for 72h~120h.

4. The method for preparing the silver-doped cobalt-based boron imidazole porous carbon microwave absorbing material according to claim 1, characterized in that, In step 6, the UV lamp irradiation time is 10 min to 4 h.

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