Cotton derived one-dimensional hollow carbon-based magnetic composite wave-absorbing material and preparation method thereof

Abstract

The application discloses a kapok-derived one-dimensional hollow carbon-based magnetic composite wave-absorbing material and a preparation method thereof, and relates to the technical field of wave-absorbing materials. The preparation method comprises the following steps: step one, removing wax on the surface of kapok fibers; step two, adding iron chloride hexahydrate and cobalt chloride hexahydrate into a mixed solvent of a part of ethylene glycol and diethylene glycol, dissolving, adding the kapok fibers pretreated in step one, and uniformly dispersing; then, adding anhydrous sodium acetate into the remaining part of the mixed solvent of ethylene glycol and diethylene glycol; mixing the two parts of the solvent, carrying out hydrothermal reaction, cooling after the hydrothermal reaction, performing suction filtration, cleaning, drying, and obtaining iron-cobalt composite kapok fibers; and step three, calcining the iron-cobalt composite kapok fibers in step two under Ar atmosphere protection. The wave-absorbing material is light and efficient, has excellent wave-absorbing performance, the kapok fiber raw material has a wide source and is cheap, and the preparation process of the wave-absorbing material is simple, pollution-free and easy to realize large-scale production.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing materials technology, and in particular to a kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material and its preparation method. Background Technology

[0002] Research on electromagnetic wave absorbing materials originated from their application in military stealth fighters and later expanded to the civilian field for protection or shielding of electronic devices. However, previous electromagnetic wave absorbing materials were mostly made from ferromagnetic materials such as ferrites. These materials have high density, resulting in a high specific gravity, which is detrimental to lightweight devices. Furthermore, these materials suffer from drawbacks such as narrow absorption range, weak absorption, and high cost. Carbon-based absorbing materials such as expanded graphite, carbon nanotubes, and graphene are complex to process and expensive. In contrast, carbon-based absorbing materials, represented by biomass carbon materials, overcome the shortcomings of metallic element electromagnetic wave absorbing materials, including high density, narrow absorption range, and weak absorption. Moreover, biomass materials are widely available, inexpensive, and their preparation process is simple and pollution-free. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a one-dimensional hollow carbon-based magnetic composite microwave absorbing material derived from kapok and its preparation method. The microwave absorbing material of the present invention is lightweight and efficient, with excellent microwave absorption performance. Kapok fiber raw material is widely available and inexpensive. Moreover, the preparation process of the microwave absorbing material is simple and pollution-free, and it is easy to realize large-scale production.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing a kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material, comprising the following steps:

[0005] Step 1: Kapok fiber pretreatment: Remove the waxy coating from the surface of the kapok fibers;

[0006] Step 2: In-situ growth of iron-cobalt particles: Add ferric chloride hexahydrate and cobalt chloride hexahydrate to a portion of a mixed solvent of ethylene glycol and diethylene glycol, dissolve them, add the pretreated kapok fibers from Step 1, and disperse evenly; then add anhydrous sodium acetate to the remaining portion of the mixed solvent of ethylene glycol and diethylene glycol; mix the two solvents and transfer them to a hydrothermal reactor for hydrothermal reaction. After the hydrothermal reaction is completed, cool, filter, wash, and dry to obtain iron-cobalt composite kapok fibers;

[0007] Step 3: Calcination: The iron-cobalt composite kapok fiber prepared above is calcined under Ar atmosphere protection to obtain a kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material.

[0008] Preferably, step one: use sodium chlorite to remove the wax on the surface of the kapok fibers.

[0009] Further preferred step 1: Kapok fiber pretreatment: Add shredded kapok to a mixed solvent of water and ethanol, add glacial acetic acid to adjust the pH value to 2-3, then add sodium chlorite, heat to react to remove the wax on the surface of the kapok, cool to room temperature, filter to remove the solution, wash with deionized water until neutral, and dry.

[0010] More preferably, in step one: the mass ratio of water to ethanol in the mixed solvent of water and ethanol is 3:1 to 1:3; the mass-volume ratio of kapok to the mixed solvent of water and ethanol is 1g:300mL to 1g:500mL; the mass ratio of sodium chlorite to kapok is 3:1 to 5:1; the heating reaction temperature is 70℃ to 90℃, and the reaction time is 4h to 6h.

[0011] Preferably, in step two: the molar ratio of ferric chloride hexahydrate to cobalt chloride hexahydrate is 2:1; the mass ratio of cobalt chloride hexahydrate to pretreated kapok fiber is 0.47g:0.3g~0.47g:1.8g.

[0012] Preferably, in step two, the mass ratio of ethylene glycol to diethylene glycol in the mixed solvent of ethylene glycol and diethylene glycol is 3:1 to 1:3.

[0013] Preferably, in step two: the total mass-to-volume ratio of the pretreated kapok fiber to the mixed solvent of ethylene glycol and diethylene glycol is (0.3-1.2) g: 80 mL; the total mass-to-volume ratio of anhydrous sodium acetate to the mixed solvent of ethylene glycol and diethylene glycol is (1.2-1.8) g: 80 mL; and a portion of the mixed solvent of ethylene glycol and diethylene glycol is used in equal amounts to the remaining portion of the mixed solvent of ethylene glycol and diethylene glycol.

[0014] Preferably, in step two: the hydrothermal reaction temperature is 180-220℃, and the reaction time is 6-10h; the cleaning is performed by washing twice with anhydrous ethanol and water.

[0015] Preferably, step three: calcination: the iron-cobalt composite kapok fiber from step two is placed in a tube furnace and heated to 550-800℃ at a rate of 5-10℃ / s under Ar atmosphere protection, then held at that temperature for 2-3 hours and naturally cooled to room temperature to obtain a kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material.

[0016] A kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material is prepared using the aforementioned preparation method for kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material.

[0017] The beneficial effects of adopting the above technical solution are as follows:

[0018] (1) The wave-absorbing material of the present invention is lightweight and efficient, with excellent wave-absorbing performance. The raw material of kapok fiber is widely available and inexpensive. Moreover, the preparation process of the wave-absorbing material is simple and pollution-free, and it is easy to achieve large-scale production.

[0019] (2) The absorbing material of the present invention meets the requirements of "thin, light, wide and strong". When the thickness is 2.5 mm, the absorption bandwidth is 4.5 GHz and the strongest absorption intensity is 46.5 dB.

[0020] (3) The microwave absorbing material of the present invention is composed of CoFe / C and has a morphology of one-dimensional hollow fiber with CoFe particles loaded on the fiber tube wall. The crystal form, carbon structure and magnetic properties of the composite material are characterized by XRD, Raman and VSM.

[0021] (4) The excellent electromagnetic wave absorption performance of the absorbing material of this invention originates from the in-situ growth of loose and porous nano-iron-cobalt magnetic particles on the surface of one-dimensional hollow kapok fibers during the production process. This allows the iron-cobalt magnetic particles to be uniformly composited on the tube wall of the kapok fibers. Then, the iron-cobalt composite kapok fibers are calcined under Ar atmosphere protection to achieve carbonization and graphitization of the kapok fibers, transforming the iron-cobalt composite kapok fibers into carbon-based magnetic composite absorbing materials. Thanks to the hollow tubular structure of the kapok fibers, the electromagnetic wave absorber is made lightweight. Kapok fibers come from the fruit of the kapok tree, a plant of the Bombacaceae family. Compared with the raw materials of previous electromagnetic wave absorbing materials, the source is wide and the cost is low.

[0022] (5) Compared with carbon-based microwave absorbing materials such as expanded graphite, carbon nanotubes, and graphene, the kapok fiber raw material involved in this invention is inexpensive and readily available, and the preparation process is simple and pollution-free. Furthermore, the hollow one-dimensional kapok fiber can reduce the density of the composite material, resulting in a lightweight microwave absorbing composite material. Compared with traditional magnetic microwave absorbing materials such as metal alloys, carbonyl iron powder, and ferrite powder, the iron-cobalt magnetic particles involved in this invention have a loose and porous microstructure and good magnetic properties, enabling excellent microwave absorption performance at a lower density. From the perspective of material preparation methods, the in-situ growth method and high-temperature calcination method involved in this invention are simple in process, controllable in parameters, and easy to implement for large-scale production. Attached Figure Description

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments;

[0024] Figure 1 This is the XRD diffraction pattern of the kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material obtained in Example 2 of this invention;

[0025] Figure 2 This is the Raman absorption spectrum of the kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material obtained in Example 2 of the present invention;

[0026] Figure 3 This is a room temperature hysteresis loop diagram of the kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material obtained in Example 2 of the present invention.

[0027] Figure 4 This is a diagram showing the relative permittivity of the kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material obtained in Example 2 of this invention.

[0028] Figure 5 This is the complex permeability diagram of the kapok-derived one-dimensional hollow carbon-based magnetic composite absorbing material obtained in Example 2 of the present invention;

[0029] Figure 6 This is the dielectric loss tangent of the kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material obtained in Example 2 of this invention;

[0030] Figure 7 This is the magnetic loss tangent of the kapok-derived one-dimensional hollow carbon-based magnetic composite absorbing material obtained in Example 2 of the present invention;

[0031] Figure 8 This is a 3D diagram of the theoretical absorption value of the kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material obtained in Example 2 of this invention;

[0032] Figure 9 This is a microscopic morphology diagram of the kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material obtained in Example 2 of the present invention;

[0033] Figure 10 This is a microscopic morphology diagram of the kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material obtained in Example 3 of the present invention. Detailed Implementation

[0034] Example 1

[0035] Step 1: Kapok Fiber Pretreatment: Add 1g of chopped kapok fibers to 300mL of a mixture of water and ethanol (mass ratio 3:1), adjust the pH to 2.5 with 5mL of glacial acetic acid, and then add 3g of sodium chlorite. React at 80℃ for 4 hours, cool to room temperature, and wash with deionized water until neutral. Dry.

[0036] Step 2: In-situ growth of iron-cobalt particles: 1.08 g of ferric chloride hexahydrate and 0.47 g of cobalt chloride hexahydrate were added to 40 mL of a 3:1 mixture of ethylene glycol and diethylene glycol. The solution was placed in an ultrasonic cleaner to promote dissolution. 0.3 g of the kapok fibers from Step 1 were added to the above solution and dispersed evenly. Then, 1.6 g of anhydrous sodium acetate was added to another 40 mL of the same 3:1 mixture of ethylene glycol and diethylene glycol. The two solvents were mixed and quickly transferred to a 100 mL hydrothermal reactor. The reaction was carried out at 200 °C for 8 hours. After cooling, the mixture was washed twice with ethanol and water, and then dried to obtain iron-cobalt composite kapok fibers.

[0037] Step 3: Calcination: The iron-cobalt composite kapok fiber from Step 2 is placed in a tube furnace and heated to 600°C at a rate of 5°C per second under Ar atmosphere protection. It is then held at that temperature for two hours and allowed to cool naturally to room temperature to obtain a kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material.

[0038] Example 2

[0039] Step 1: Kapok Fiber Pretreatment: Add 1g of chopped kapok fibers to 300mL of a mixture of water and ethanol (mass ratio 3:1), adjust the pH to 2.5 with 5mL of glacial acetic acid, and then add 3g of sodium chlorite. React at 80℃ for 4 hours, cool to room temperature, and wash with deionized water until neutral. Dry.

[0040] Step 2: In-situ growth of iron-cobalt particles: 1.08 g of ferric chloride hexahydrate and 0.47 g of cobalt chloride hexahydrate were added to 40 mL of a 3:1 mixture of ethylene glycol and diethylene glycol. The solution was placed in an ultrasonic cleaner to promote dissolution. 0.6 g of the kapok fibers from Step 1 were added to the above solution and dispersed evenly. Then, 1.6 g of anhydrous sodium acetate was added to another 40 mL of the same 3:1 mixture of ethylene glycol and diethylene glycol. The two solvents were mixed and quickly transferred to a 100 mL hydrothermal reactor. The reaction was carried out at 200 °C for 8 hours. After cooling, the mixture was washed twice with ethanol and water, and then dried to obtain iron-cobalt composite kapok fibers.

[0041] Step 3: Calcination: The iron-cobalt composite kapok fiber from Step 2 is placed in a tube furnace and heated to 600°C at a rate of 5°C per second under Ar atmosphere protection. It is then held at that temperature for two hours and allowed to cool naturally to room temperature to obtain a kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material.

[0042] The kapok-derived one-dimensional hollow carbon-based magnetic composite absorbing material obtained in this embodiment has superior electromagnetic wave absorption performance and the advantages of being lightweight and environmentally friendly compared to other electromagnetic wave materials. Figure 8The 3D schematic diagram of the theoretical microwave absorption performance of the hollow biomass carbon material obtained in this embodiment shows that, with a material thickness of 2.5 mm, the material achieves an absorption peak of 50.6 dB at 13.9 GHz, with an absorption bandwidth of 6.8 GHz. This is higher than that of most materials reported in the literature. Figure 6 The main loss in the hollow biomass carbon material shown is dielectric loss, while magnetic loss helps optimize the impedance matching of the material. Figure 4 This is a schematic diagram illustrating the relationship between the dielectric constant and frequency of the hollow biomass carbon material obtained in this embodiment. Figure 5 This is a schematic diagram illustrating the relationship between the magnetic permeability and frequency of the hollow biomass carbon material obtained in this embodiment. Figure 6 This is a schematic diagram of the dielectric loss tangent of the hollow biomass carbon material obtained in this embodiment. Figure 9 The image shows the microstructure of the hollow biomass carbon material obtained in this embodiment. It can be observed that CoFe nanospheres grow on the surface of the hollow carbon tubes of kapok.

[0043] Example 3

[0044] Step 1: Kapok Fiber Pretreatment: Dissolve 1g of shredded kapok fibers in 300mL of a mixture of water and ethanol (3:1 mass ratio). Add 5mL of glacial acetic acid to adjust the pH to 2.5, then add 3g of sodium chlorite. React at 80℃ for 4 hours, cool to room temperature, and wash with deionized water until neutral. Dry.

[0045] Step 2: In-situ growth of iron-cobalt particles: 1.08 g of ferric chloride hexahydrate and 0.47 g of cobalt chloride hexahydrate were added to 40 mL of a 3:1 mixture of ethylene glycol and diethylene glycol. The solution was placed in an ultrasonic cleaner to promote dissolution. 1.8 g of the kapok fibers from Step 1 were added to the above solution and dispersed evenly. Then, 1.6 g of anhydrous sodium acetate was added to another 40 mL of the same 3:1 mixture of ethylene glycol and diethylene glycol. The two solvents were mixed and quickly transferred to a 100 mL hydrothermal reactor. The reaction was carried out at 200 °C for 8 hours. After cooling, the mixture was washed twice with ethanol and water, and then dried to obtain iron-cobalt composite kapok fibers.

[0046] Step 3: Calcination: The iron-cobalt composite kapok fiber from Step 2 is placed in a tube furnace and heated to 600°C at a rate of 5°C per second under Ar atmosphere protection. It is then held at that temperature for two hours and allowed to cool naturally to room temperature to obtain a kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material.

[0047] The microstructure of the kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material obtained in this embodiment is shown in the figure below. Figure 10 As shown, it can be observed that the density of CoFe nanospheres grown on the surface of hollow carbon nanotubes of kapok is lower than that in Example 2.

[0048] Example 4

[0049] Step 1: Kapok Fiber Pretreatment: Dissolve 1g of shredded kapok fibers in 300mL of a mixture of water and ethanol (3:1 mass ratio). Add 5mL of glacial acetic acid to adjust the pH to 2.5, then add 3g of sodium chlorite. React at 80℃ for 4 hours, cool to room temperature, and wash with deionized water until neutral. Dry.

[0050] Step 2: In-situ growth of iron-cobalt particles: 1.08 g of ferric chloride hexahydrate and 0.47 g of cobalt chloride hexahydrate were added to 40 mL of a 3:1 mixture of ethylene glycol and diethylene glycol. The solution was placed in an ultrasonic cleaner to promote dissolution. 0.6 g of the kapok fibers from Step 1 were added to the above solution and dispersed evenly. Then, 1.6 g of anhydrous sodium acetate was added to another 40 mL of the same 3:1 mixture of ethylene glycol and diethylene glycol. The two solvents were mixed and quickly transferred to a 100 mL hydrothermal reactor. The reaction was carried out at 200 °C for 8 hours. After cooling, the mixture was washed twice with ethanol and water, and then dried to obtain iron-cobalt composite kapok fibers.

[0051] Step 3: Calcination: The iron-cobalt composite kapok fiber from Step 2 is placed in a tube furnace and heated to 550°C at a rate of 5°C per second under Ar atmosphere protection. It is then held at that temperature for two hours and allowed to cool naturally to room temperature to obtain a kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material.

[0052] Example 5

[0053] Step 1: Kapok Fiber Pretreatment: Dissolve 1g of shredded kapok fibers in 300mL of a mixture of water and ethanol (3:1 mass ratio). Add 5mL of glacial acetic acid to adjust the pH to 2.5, then add 3g of sodium chlorite. React at 80℃ for 4 hours, cool to room temperature, and wash with deionized water until neutral. Dry.

[0054] Step 2: In-situ growth of iron-cobalt particles: 1.08 g of ferric chloride hexahydrate and 0.47 g of cobalt chloride hexahydrate were added to 40 mL of a 3:1 mixture of ethylene glycol and diethylene glycol. The solution was placed in an ultrasonic cleaner to promote dissolution. 0.6 g of the kapok fibers from Step 1 were added to the above solution and dispersed evenly. Then, 1.6 g of anhydrous sodium acetate was added to another 40 mL of the same 3:1 mixture of ethylene glycol and diethylene glycol. The two solvents were mixed and quickly transferred to a 100 mL hydrothermal reactor. The reaction was carried out at 200 °C for 8 hours. After cooling, the mixture was washed twice with ethanol and water, and then dried to obtain iron-cobalt composite kapok fibers.

[0055] Step 3: Calcination: The iron-cobalt composite kapok fiber from Step 2 is placed in a tube furnace and heated to 700°C at a rate of 5°C per second under Ar atmosphere protection. It is then held at that temperature for two hours and allowed to cool naturally to room temperature to obtain a kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material.

Claims

1. A method for preparing a kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material, characterized in that: Includes the following steps: Step 1: Kapok fiber pretreatment: Remove the waxy coating from the surface of the kapok fibers; Step 2: In-situ growth of iron-cobalt particles: Ferric chloride hexahydrate and cobalt chloride hexahydrate are added to a portion of a mixed solvent of ethylene glycol and diethylene glycol and dissolved. The pretreated kapok fibers from Step 1 are then added to form a uniformly dispersed solution. Anhydrous sodium acetate is then added to the remaining portion of the mixed solvent of ethylene glycol and diethylene glycol to form another mixed solution. The two solutions are then mixed and transferred to a hydrothermal reactor for hydrothermal reaction. After the hydrothermal reaction is completed, the mixture is cooled, filtered, washed, and dried to obtain iron-cobalt composite kapok fibers. Step 3: Calcination: The iron-cobalt composite kapok fiber prepared above is calcined under Ar atmosphere protection to obtain kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material; Step two: the molar ratio of ferric chloride hexahydrate and cobalt chloride hexahydrate is 2:1; the mass ratio of cobalt chloride hexahydrate to pretreated kapok fiber is 0.47g:0.3g - 0.47g:1.8g; the mass ratio of ethylene glycol to diethylene glycol in the mixed solvent of ethylene glycol and diethylene glycol is 3:1-1:3; Step 1: Use sodium chlorite to remove the waxy coating from the surface of the kapok fibers; Kapok fiber pretreatment: Add chopped kapok to a mixed solvent of water and ethanol, add glacial acetic acid to adjust the pH to 2-3, then add sodium chlorite, heat to react and remove the wax on the surface of the kapok, cool to room temperature, filter to remove the solution, wash with deionized water until neutral, and dry. Step 1: The mass ratio of water to ethanol in the mixed solvent of water and ethanol is 3:1 to 1:3; the mass-volume ratio of kapok to the mixed solvent of water and ethanol is 1g:300mL to 1g:500mL; the mass ratio of sodium chlorite to kapok is 3:1 to 5:1; the heating temperature is 70℃ to 90℃, and the reaction time is 4h to 6h. Step two: The mass-to-volume ratio of the pretreated kapok fiber to the mixed solvent of ethylene glycol and diethylene glycol is (0.3-1.2) g: 80 mL; the mass-to-volume ratio of the anhydrous sodium acetate to the mixed solvent of ethylene glycol and diethylene glycol is (1.2-1.8) g: 80 mL; a portion of the mixed solvent of ethylene glycol and diethylene glycol is used in equal amounts to the remaining portion of the mixed solvent of ethylene glycol and diethylene glycol.

2. The preparation method of the kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material according to claim 1, characterized in that... Step two: The hydrothermal reaction temperature is 180-220℃, and the reaction time is 6-10h; the cleaning is done by washing twice with anhydrous ethanol and water.

3. The preparation method of the kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material according to claim 1, characterized in that... Step 3: Calcination: The iron-cobalt composite kapok fiber from step 2 is placed in a tube furnace and heated to 550-800℃ at a rate of 5-10℃ / s under Ar atmosphere protection. Then, it is kept at this temperature for 2-3 hours and naturally cooled to room temperature to obtain a kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material.

4. A kapok-derived one-dimensional hollow carbon-based magnetic composite microwave absorbing material, characterized in that, The material is prepared using the method described in any one of claims 1-3 for the preparation of one-dimensional hollow carbon-based magnetic composite microwave absorbing material derived from kapok.

Images