Preparation method of foamy carbon composite wave-absorbing material and foamy carbon composite wave-absorbing material
By preparing foamed carbon composite microwave absorbing materials, the electromagnetic wave path is extended by utilizing conductive networks and porous structures, and electromagnetic waves are absorbed in a synergistic manner through magnetic loss and dielectric loss. This solves the reflection problem of carbon materials and achieves more effective electromagnetic wave absorption.
Patent Information
- Application Number
- CN202511647257.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-11
- Publication Date
- 2026-03-17
AI Technical Summary
When carbon materials are used as microwave absorbing materials, they tend to generate strong electromagnetic wave reflections, leading to secondary pollution.
The method for preparing foamed carbon composite microwave absorbing materials includes immersing nickel foam in a polyacrylonitrile solution, pre-oxidation, carbonization, acid etching, acid activation, hydrothermal reaction and heat treatment to form foamed carbon loaded with Co-Fe precursor. The conductive network and porous structure are used to extend the electromagnetic wave path, and electromagnetic waves are absorbed through the synergistic absorption of magnetic loss and dielectric loss.
It improves the electromagnetic wave absorption effect of carbon materials, broadens the absorption bandwidth, enhances the absorption capacity of electromagnetic waves, and reduces the density of the material.
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Figure CN121674027A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the technical field of wave-absorbing materials, and particularly relates to a preparation method of a foamed carbon composite wave-absorbing material and the foamed carbon composite wave-absorbing material. BACKGROUND
[0002] With the rapid development of science and technology, 5G electronic devices greatly facilitate people's daily life. However, the widespread use of electronic devices inevitably brings the problem of electromagnetic pollution, which poses a potential risk to human health and the safety of precision instruments. Using electromagnetic shielding materials and microwave absorbing materials is an effective way to solve the problem of electromagnetic pollution.
[0003] Carbon materials, especially three-dimensional porous foamed carbon materials, have the characteristics of low density, high specific surface area, adjustable electrical conductivity and stable chemical properties. However, carbon materials have too high electrical conductivity, which causes strong reflection of electromagnetic waves transmitted to the surface of the carbon material, resulting in secondary pollution. SUMMARY
[0004] The application aims to provide a preparation method of a foamed carbon composite wave-absorbing material and the foamed carbon composite wave-absorbing material, and aims to improve the problem that carbon materials are prone to strong reflection as wave-absorbing materials.
[0005] In a first aspect, the application provides a preparation method of a foamed carbon composite wave-absorbing material, which comprises the following steps: foamed nickel is immersed in a polyacrylonitrile solution to obtain a first composite; the first composite is subjected to pre-oxidation treatment to obtain a pre-oxidation product. The pre-oxidation product is subjected to carbonization treatment to obtain a carbonization product. The carbonization product is etched with an acid solution to obtain foamed carbon. The foamed carbon is subjected to acid activation treatment to obtain activated foamed carbon. A first mixed solution containing a cobalt salt, an iron salt and urea is prepared, and the activated foamed carbon is immersed in the first mixed solution to perform hydrothermal reaction, thereby obtaining foamed carbon loaded with a Co-Fe precursor. The foamed carbon loaded with the Co-Fe precursor is subjected to heat treatment to obtain a foamed carbon composite wave-absorbing material.
[0006] In some embodiments, the pre-oxidation treatment of the first composite comprises the following steps: the first composite is placed in a pre-oxidation device, the pre-oxidation device has a temperature rising speed of 8-12 ℃ / min, the pre-oxidation device is heated to a first preset temperature, and the first composite is kept at the first preset temperature for 2-4 h, and the first preset temperature is 180-240 ℃.
[0007] In some embodiments, the carbonizing treatment of the pre-oxidized product comprises: placing the pre-oxidized product in a tube furnace containing inert gas, the tube furnace has a heating rate of 8-12 °C / min, heating the tube furnace to a second preset temperature, carbonizing at the second preset temperature for 2-3 h, and the second preset temperature is 1000-1200 °C.
[0008] In some embodiments, the acid activation treatment of the foamed carbon to obtain activated foamed carbon comprises: soaking the foamed carbon in a concentrated nitric acid solution, refluxing at a temperature of 50-70 °C for 2-4 h, and then washing and drying the acid-activated foamed carbon with deionized water to obtain the activated foamed carbon.
[0009] In some embodiments, the hydrothermal reaction of the activated foamed carbon in the first mixed solution to obtain foamed carbon loaded with Co-Fe precursors comprises: soaking the activated foamed carbon in the first mixed solution to obtain a second mixed solution, placing the second mixed solution in a high-pressure reaction kettle, placing the high-pressure reaction kettle in an oven at a temperature of 120-180 °C, heating for 4-8 h, and then washing and drying to obtain foamed carbon loaded with Co-Fe precursors.
[0010] In some embodiments, the heat treatment of the foamed carbon loaded with Co-Fe precursors to obtain a foamed carbon composite wave-absorbing material comprises: placing the foamed carbon loaded with Co-Fe precursors in a muffle furnace, heating the muffle furnace to a third preset temperature at a rate of 5-10 °C / min, and reacting at the third preset temperature for 1-2 h, and then cooling to obtain the foamed carbon composite wave-absorbing material, and the third preset temperature is 300-400 °C.
[0011] In some embodiments, the concentration of the polyacrylonitrile solution is 5-10 wt%.
[0012] In some embodiments, the concentration of the acid solution is 2-4 mol / L.
[0013] In some embodiments, the cobalt salt comprises at least one of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, and cobalt sulfate heptahydrate, and the iron salt comprises at least one of iron nitrate nonahydrate, iron chloride hexahydrate, and iron sulfate nonahydrate.
[0014] In a second aspect, the present application also provides a foamed carbon composite wave-absorbing material, which is prepared by the method of any one of the first aspect.
[0015] Differently from the prior art, the embodiment of the present application provides a preparation method of a foam carbon composite wave-absorbing material, which comprises the following steps: foam nickel is immersed in a polyacrylonitrile solution to obtain a first composite; the first composite is subjected to pre-oxidation treatment to obtain a pre-oxidation product; the pre-oxidation product is subjected to carbonization treatment to obtain a carbonization product; the carbonization product is etched by using an acid solution to obtain foam carbon; the foam carbon is subjected to acid activation treatment to obtain activated foam carbon; a first mixed solution containing a cobalt salt, an iron salt and urea is prepared, and the activated foam carbon is immersed in the first mixed solution to perform hydrothermal reaction, thereby obtaining foam carbon loaded with a Co-Fe precursor; and the foam carbon loaded with the Co-Fe precursor is subjected to heat treatment to obtain the foam carbon composite wave-absorbing material. The foam carbon has good electrical conductivity and can form an electrically conductive network, and the incident electromagnetic wave will produce conductive loss on the electrically conductive network. The foam carbon has a porous structure, which can prolong the reflection and scattering path of the electromagnetic wave in the material, increase the loss of electromagnetic wave energy, and the ferriferrous oxide cobalt has high saturation magnetization and magnetic permeability, can absorb and consume electromagnetic waves through magnetic loss, and is mutually synergistic with the dielectric loss of the foam carbon, so that the dielectric constant and the magnetic permeability of the foam carbon composite wave-absorbing material can be adjusted, the impedance mismatch can be improved, the absorption frequency band of the electromagnetic wave can be widened, and the absorption effect of the electromagnetic wave can be improved.
[0016] Additional aspects and advantages of the embodiments of the present application will be described in part in the description that follows, will be apparent through the description or can be learned from the practice of the embodiments of the present application. BRIEF DESCRIPTION OF DRAWINGS
[0017] One or more embodiments are illustrated by way of example in the figures that constitute a part of this specification, which are illustrative, and do not limit the embodiments, and elements having the same reference numerals in the figures represent similar elements.
[0018] Figure 1 A flowchart of a preparation method of a foam carbon composite wave-absorbing material is provided for some embodiments of the present application. DETAILED DESCRIPTION
[0019] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments.
[0020] In the present application, the phrase "embodiment" means that the specific features, structures or characteristics described in connection with the embodiment can be included in at least one embodiment of the present application. The appearance of this phrase at various places in the specification does not necessarily mean that it refers to the same embodiment, nor is it an independent or alternative embodiment that is not mutually exclusive with other embodiments.
[0021] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.
[0022] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.
[0023] The technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.
[0024] Firstly, embodiments of this application provide a method for preparing a foamed carbon composite microwave absorbing material, please refer to... Figure 1 The preparation method includes the following steps: Step S1: Immerse nickel foam in a polyacrylonitrile solution to obtain a first composite. Perform a pre-oxidation treatment on the first composite to obtain a pre-oxidized product.
[0025] Nickel foam is a porous foam metal material with a three-dimensional network structure composed of an interconnected nickel framework, containing numerous randomly distributed pores. Nickel foam acts as a physical template, allowing polyacrylonitrile (PAN) solution to fully penetrate and fill these pores. During subsequent carbonization, the PAN is converted into a carbon framework, and the nickel template is then removed by etching, ultimately retaining a three-dimensional porous foam carbon structure similar to that of nickel foam.
[0026] In some embodiments, the nickel foam is cut into blocks to allow for more thorough immersion in polyacrylonitrile. For example, it can be cut into sizes such as 2cm×2cm, 2cm×3cm, 1cm×3cm, 2cm×1cm, 3cm×3cm, and 3cm×1cm.
[0027] Polyacrylonitrile (PA) is a polymer compound obtained by free radical polymerization of acrylonitrile monomer. In the embodiments of this application, PA serves as a carbon source and a precursor for the skeleton of foamed carbon. After PA is impregnated into the pores of foamed nickel, it undergoes pre-oxidation to form a stable structure, followed by high-temperature carbonization to form a conductive carbon skeleton.
[0028] In some embodiments, the concentration of the polyacrylonitrile solution is 5 wt% to 10 wt%, allowing the polyacrylonitrile to fully penetrate into the pores of the nickel foam and form a uniform filling layer within the pores. A concentration of 5 wt% to 10 wt% polyacrylonitrile results in a lower density of the prepared carbon foam, making the prepared carbon foam composite microwave absorbing material lightweight.
[0029] Pre-oxidation treatment refers to the low-temperature oxidation process performed on the precursor before high-temperature carbonization. If polyacrylonitrile, a linear polymer, is directly subjected to high-temperature carbonization, the rapid decomposition of the molecular chains leads to the formation of numerous small molecules, causing drastic structural shrinkage, cracking, and even collapse. Pre-oxidation treatment, through a gentle reaction at low temperatures, transforms the linear structure of polyacrylonitrile into a stable network structure, enabling it to withstand the subsequent high-temperature carbonization environment.
[0030] In some embodiments, the pre-oxidation treatment of the first composite includes: placing the first composite in a pre-oxidation device, wherein the heating rate of the pre-oxidation device is 8°C / min to 12°C / min, heating the pre-oxidation device to a first preset temperature, and holding it at the first preset temperature for 2h to 4h, wherein the first preset temperature is 180°C to 240°C.
[0031] Step S2: Carbonize the pre-oxidized product to obtain the carbonized product.
[0032] Step S3: Etch the carbonized product with an acid solution to obtain foamed carbon.
[0033] Carbonization is a process in which carbon-containing precursors are treated at high temperatures under the protection of an inert gas, so that non-carbon elements such as H, O, and N are removed through decomposition and volatilization, ultimately forming a solid material with carbon as the main component.
[0034] The pre-oxidized polyacrylonitrile has formed a stable network structure. Through carbonization, heteroatoms such as H, O, and N are further removed, and the carbonized product with carbon as the backbone is finally retained.
[0035] In some embodiments, carbonizing the pre-oxidized product includes: placing the pre-oxidized product in a tube furnace containing an inert gas, wherein the heating rate of the tube furnace is 8°C / min to 12°C / min, heating the tube furnace to a second preset temperature, and carbonizing at the second preset temperature for 2 to 3 hours, wherein the second preset temperature is 1000°C to 1200°C. The inert gas includes any one of nitrogen, helium, and argon.
[0036] An acid solution can react with nickel, dissolving the nickel foam template and retaining only the carbonized carbon skeleton to obtain independent three-dimensional porous carbon foam. The acid solution is hydrochloric acid with a concentration of 2 mol / L to 4 mol / L.
[0037] Carbon foam is a lightweight, porous, foam-like carbon material with a three-dimensional network structure composed of pores and interconnected pore walls. Carbon foam serves as the structural carrier for composite microwave absorbing materials, and its inherent conductivity absorbs electromagnetic waves through dielectric loss. Inheriting the high porosity of nickel foam, carbon foam reduces the density of composite microwave absorbing materials. The porous structure also lengthens the reflection and scattering path of electromagnetic waves within the material, increasing energy loss. After carbonization, carbon foam exhibits certain resistance to acids and alkalis, as well as high temperatures, resulting in superior stability in carbon foam composite microwave absorbing materials.
[0038] Step S4: Perform acid activation treatment on the foamed carbon to obtain activated foamed carbon.
[0039] Acid activation treatment refers to surface treatment of foamed carbon with strong oxidizing acid, which further introduces a large number of hierarchical pore structures on the foamed carbon, significantly increasing the specific surface area of the foamed carbon and providing more attachment sites for the Co-Fe precursor, making the Co-Fe precursor uniformly dispersed and increasing the loading of the Co-Fe precursor. The strong oxidizing properties of concentrated nitric acid will cause an oxidation reaction on the surface of foamed carbon, introducing a large number of oxygen-containing functional groups, mainly including hydroxyl (-OH), carboxyl (-COOH) or carbonyl (C=O). These polar functional groups significantly enhance the adsorption capacity of foamed carbon for cobalt and iron ions through coordination or electrostatic attraction, reducing the aggregation of metal ions in subsequent hydrothermal reactions due to insufficient adsorption.
[0040] In some embodiments, the foamed carbon is subjected to acid activation treatment to obtain activated foamed carbon, which includes immersing the foamed carbon in a concentrated nitric acid solution, refluxing it at a temperature of 50°C to 70°C for 2 to 4 hours, washing the acid-activated foamed carbon with deionized water, and drying it to obtain activated foamed carbon.
[0041] In some embodiments, the foamed carbon is cut into blocks to allow for more thorough soaking in concentrated nitric acid. For example, it can be cut into sizes such as 2cm×2cm, 2cm×3cm, 1cm×3cm, 2cm×1cm, 3cm×3cm, and 3cm×1cm.
[0042] Step S5: Prepare a first mixed solution containing cobalt salt, iron salt and urea, immerse the activated foam carbon in the first mixed solution and carry out a hydrothermal reaction to obtain foam carbon loaded with Co-Fe precursor.
[0043] Cobalt salts can dissociate into cobalt ions (Co) in the first mixture. 2+ Iron salts can dissociate into iron ions (Fe) in the first mixture. 3+Cobalt salts, under the regulation of urea, form Co-Fe precursors. For example, cobalt salts include at least one of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, and cobalt sulfate heptahydrate. Iron salts include at least one of ferric nitrate nonahydrate, ferric chloride hexahydrate, and ferric sulfate nonahydrate.
[0044] Urea slowly hydrolyzes to produce ammonia in a hydrothermal reaction, which gradually increases the pH of the solution. This promotes the formation of hydroxide colloids from cobalt and iron ions. The hydroxide colloids can be uniformly attached to the pores and surface of the activated foam carbon, reducing particle agglomeration.
[0045] Hydrothermal reaction refers to the process of using water as the reaction medium in a closed, high-pressure reactor to create a high-temperature, high-pressure reaction environment, which promotes the dissolution, reaction, crystallization, or deposition of reactants, ultimately generating the target product on the surface and / or pores of carbon foam.
[0046] In some embodiments, the activated foamed carbon is immersed in a first mixture to undergo a hydrothermal reaction to obtain foamed carbon loaded with Co-Fe precursor. This includes: immersing the activated foamed carbon in the first mixture to obtain a second mixture; placing the second mixture in a high-pressure reactor; placing the high-pressure reactor in an oven at a temperature of 120°C to 180°C and heating for 4 to 8 hours; cooling, washing, and drying to obtain foamed carbon loaded with Co-Fe precursor. The high-pressure reactor may be a polytetrafluoroethylene-lined high-pressure reactor.
[0047] Step S6: Heat-treat the foamed carbon loaded with Co-Fe precursor to obtain foamed carbon composite microwave absorbing material.
[0048] The Co-Fe precursor is heat-treated to transform into spinel-structured cobalt tetroxide (CoFe2O4). Cobalt tetroxide is a magnetic material with high saturation magnetization and permeability. It can absorb and dissipate electromagnetic waves through magnetic loss, and its interaction with the dielectric loss of carbon foam broadens the absorption bandwidth of electromagnetic waves.
[0049] In some embodiments, foamed carbon loaded with Co-Fe precursor is heat-treated to obtain foamed carbon composite microwave absorbing material. This includes placing the foamed carbon loaded with Co-Fe precursor in a muffle furnace, heating the muffle furnace to a third preset temperature at a rate of 5°C / min to 10°C / min, reacting at the third preset temperature for 1 h to 2 h, and then cooling to obtain the foamed carbon composite microwave absorbing material. The third preset temperature is 300°C to 400°C.
[0050] This application provides a method for preparing a foamed carbon composite microwave absorbing material. The method includes immersing nickel foam in a polyacrylonitrile solution to obtain a first composite; pre-oxidizing the first composite to obtain a pre-oxidized product; carbonizing the pre-oxidized product to obtain a carbonized product; etching the carbonized product with an acid solution to obtain foamed carbon; acid-activating the foamed carbon to obtain activated foamed carbon; preparing a first mixed solution containing cobalt salt, iron salt, and urea; immersing the activated foamed carbon in the first mixed solution for a hydrothermal reaction to obtain foamed carbon loaded with a Co-Fe precursor; and heat-treating the foamed carbon loaded with the Co-Fe precursor to obtain the foamed carbon composite microwave absorbing material. Foamed carbon has good electrical conductivity and can form a conductive network, where incident electromagnetic waves will generate conductive losses. The porous structure of foamed carbon can prolong the reflection and scattering path of electromagnetic waves within the material, increasing the energy loss of electromagnetic waves. Cobalt tetroxide has high saturation magnetization and permeability, which can absorb and consume electromagnetic waves through magnetic loss. In addition, it works synergistically with the dielectric loss of carbon foam to adjust the dielectric constant and permeability of carbon foam composite microwave absorbing materials, improve impedance mismatch, broaden the absorption bandwidth of electromagnetic waves, and improve the absorption effect of electromagnetic waves.
[0051] Secondly, embodiments of this application also provide a foamed carbon composite microwave absorbing material, including a method for preparing the foamed carbon composite microwave absorbing material as described in any embodiment of the first aspect.
[0052] The preparation method of foamed carbon composite microwave absorbing material is described below with reference to specific embodiments: Example 1 (1) The nickel foam was immersed in a 5 wt% polyacrylonitrile solution for 30 min to obtain the first composite. The first composite was pre-oxidized in a muffle furnace at 210 °C for 2 h and then naturally cooled to room temperature to obtain the pre-oxidized product. The pre-oxidized product was carbonized in a tube furnace with Ar gas introduced at 1000 °C for 2 h and then naturally cooled to room temperature to obtain the carbonized product. The carbonized product was etched in a 3 mol / L hydrochloric acid solution to obtain foamed carbon.
[0053] (2) Soak the foamed carbon in concentrated nitric acid and reflux at 60 °C for 2 h. Take out the acidified foamed carbon, wash it with deionized water until neutral, and dry it at 60 °C to obtain activated foamed carbon.
[0054] (3) Weigh 4.85 g of Co(NO3)2·6H2O and 13.47 g of Fe(NO3)3·9H2O and place them in 500 mL of deionized water. Stir thoroughly for 30 min and then add 6 g of urea. Stir thoroughly again for 30 min to obtain the first mixture. Immerse the activated foamed carbon in the first mixture and carry out a hydrothermal reaction to obtain foamed carbon loaded with Co-Fe precursor.
[0055] (4) The foamed carbon loaded with Co-Fe precursor is placed in a muffle furnace for heat treatment to obtain foamed carbon composite microwave absorbing material.
[0056] Example 2 (1) Nickel foam was cut into 2cm×2cm blocks and then immersed in a 10wt% polyacrylonitrile solution for 30 min to obtain the first composite. The first composite was placed in a muffle furnace at a heating rate of 10℃ / min. The muffle furnace was heated to 210℃ and pre-oxidized for 2 h. After natural cooling to room temperature, the pre-oxidized product was obtained. The pre-oxidized product was placed in a tube furnace with Ar gas introduced at a heating rate of 10℃ / min. The tube furnace was heated to 1100℃ and carbonized for 2 h. After natural cooling to room temperature, the carbonized product was obtained. The carbonized product was etched in a 3 mol / L hydrochloric acid solution to obtain carbon foam.
[0057] (2) Cut the foam carbon into blocks of 2cm×2cm size, then soak the foam carbon in concentrated nitric acid and reflux at 60 °C for 2 h. Take out the acidified foam carbon, wash it with deionized water until neutral, and dry it at 60 °C to obtain activated foam carbon.
[0058] (3) Weigh 4.85 g of Co(NO3)2·6H2O and 13.47 g of Fe(NO3)3·9H2O and place them in 500 mL of deionized water. Stir thoroughly for 30 min and then add 12 g of urea. Stir thoroughly again for 30 min to obtain the first mixture. Immerse the activated foamed carbon in the first mixture to obtain the second mixture. Place the second mixture in a high-pressure reactor and place the high-pressure reactor in an oven at 180 °C. Heat the reaction for 6 h. After cooling, wash with deionized water and ethanol and dry at 60 °C to obtain foamed carbon loaded with Co-Fe precursor.
[0059] (4) The foamed carbon loaded with Co-Fe precursor was placed in a muffle furnace. The muffle furnace was heated to 350°C at a rate of 5°C / min and reacted at 350°C for 1.5h. After natural cooling, the foamed carbon composite microwave absorbing material was obtained.
[0060] Comparative Example 1 (1) Nickel foam was cut into 2cm×2cm blocks and then immersed in a 10wt% polyacrylonitrile solution for 30 min to obtain the first composite. The first composite was placed in a muffle furnace at a heating rate of 10℃ / min. The muffle furnace was heated to 210℃ and pre-oxidized for 2 h. After natural cooling to room temperature, the pre-oxidized product was obtained. The pre-oxidized product was placed in a tube furnace with Ar gas introduced at a heating rate of 10℃ / min. The tube furnace was heated to 1100℃ and carbonized for 2 h. After natural cooling to room temperature, the carbonized product was obtained. The carbonized product was etched in a 3 mol / L hydrochloric acid solution to obtain carbon foam.
[0061] (2) Cut the foam carbon into blocks of 2cm×2cm size, then soak the foam carbon in concentrated nitric acid and reflux at 60 °C for 2 h. Take out the acidified foam carbon, wash it with deionized water until neutral, and dry it at 60 °C to obtain activated foam carbon.
[0062] The microwave absorption performance of the foamed carbon composite absorbing materials prepared in Examples 1 and 2, as well as the foamed carbon prepared in Comparative Example 1, was tested. The microwave absorption performance results of different examples and comparative examples are shown in Table 1.
[0063] Table 1
[0064] According to the absorption performance test results, comparing the above embodiments and comparative examples, the foamed carbon composite absorbing material in Embodiment 1 has a thickness of only 1.8 mm, an RLmin of -44.7 dB, and an effective absorption bandwidth of 5.2 GHz. The foamed carbon composite absorbing material in Embodiment 2 has a thickness of only 2.2 mm, an RLmin of -42.5 dB, and an effective absorption bandwidth of 5.6 GHz. The foamed carbon composite absorbing material in Comparative Example 1 has a thickness of 2.5 mm, an RLmin of -25.6 dB, and an effective absorption bandwidth of 3.2 GHz. It can be seen that the foamed carbon composite absorbing materials in Embodiments 1 and 2 absorb electromagnetic waves more effectively. Compared to Comparative Example 1, the foamed carbon composite absorbing materials in Embodiments 1 and 2 contain cobalt tetroxide, which can absorb and dissipate electromagnetic waves through magnetic loss. The synergistic effect of cobalt tetroxide and foamed carbon can adjust the dielectric constant and permeability of the foamed carbon composite absorbing material, improve impedance mismatch, broaden the absorption bandwidth of electromagnetic waves, and improve the absorption effect of electromagnetic waves.
[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of this application as described above, which are not provided in detail for the sake of brevity; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.
Claims
1. A method for preparing a foamed carbon composite wave-absorbing material, characterized in that, The method comprises the following steps: immersing the foamed nickel into a polyacrylonitrile solution to obtain a first composite, and performing pre-oxidation treatment on the first composite to obtain a pre-oxidation product; performing carbonization treatment on the pre-oxidation product to obtain a carbonization product; performing etching on the carbonization product by using an acid solution to obtain foamed carbon; performing acid activation treatment on the foamed carbon to obtain activated foamed carbon; preparing a first mixed solution containing a cobalt salt, an iron salt and urea, immersing the activated foamed carbon into the first mixed solution to perform hydrothermal reaction, and obtaining foamed carbon loaded with Co-Fe precursors; performing heat treatment on the foamed carbon loaded with Co-Fe precursors to obtain a foamed carbon composite wave-absorbing material.
2. The production method according to claim 1, characterized by, The pre-oxidation treatment on the first composite comprises the following steps: placing the first composite in a pre-oxidation device, the pre-oxidation device has a temperature rising speed of 8-12 ℃ / min, the pre-oxidation device is heated to a first preset temperature, and the first composite is kept at the first preset temperature for 2-4 h, and the first preset temperature is 180-240 ℃.
3. The preparation method according to claim 1, characterized in that, The carbonization treatment on the pre-oxidation product comprises the following steps: placing the pre-oxidation product in a tube furnace containing inert gas, the tube furnace has a temperature rising speed of 8-12 ℃ / min, the tube furnace is heated to a second preset temperature, and the pre-oxidation product is carbonized at the second preset temperature for 2-3 h, and the second preset temperature is 1000-1200 ℃.
4. The method of claim 1, wherein, The acid activation treatment on the foamed carbon to obtain activated foamed carbon comprises the following steps: immersing the foamed carbon in a concentrated nitric acid solution, refluxing the foamed carbon at a temperature of 50-70 ℃ for 2-4 h, washing and drying the foamed carbon after the acid activation treatment to obtain the activated foamed carbon.
5. The preparation method according to claim 1, characterized in that, The hydrothermal reaction on the activated foamed carbon in the first mixed solution to obtain foamed carbon loaded with Co-Fe precursors comprises the following steps: immersing the activated foamed carbon in the first mixed solution to obtain a second mixed solution, placing the second mixed solution in a high-pressure reaction kettle, placing the high-pressure reaction kettle in an oven with a temperature of 120-180 ℃, heating for 4-8 h, and washing and drying after cooling to obtain foamed carbon loaded with Co-Fe precursors.
6. The method of claim 1, wherein, The heat treatment on the foamed carbon loaded with Co-Fe precursors to obtain a foamed carbon composite wave-absorbing material comprises the following steps: placing the foamed carbon loaded with Co-Fe precursors in a muffle furnace, heating the muffle furnace to a third preset temperature at a speed of 5-10 ℃ / min, and reacting at the third preset temperature for 1-2 h, and cooling to obtain the foamed carbon composite wave-absorbing material, and the third preset temperature is 300-400 ℃.
7. The production method according to any one of claims 1 to 6, characterized by, The concentration of the polyacrylonitrile solution is 5-10 wt%.
8. The production method according to any one of claims 1 to 6, characterized by, The concentration of the acid solution is 2-4 mol / L.
9. The production method according to any one of claims 1 to 6, characterized by, The cobalt salt comprises at least one of cobalt nitrate hexahydrate, cobalt chloride hexahydrate and cobalt sulfate heptahydrate; The iron salt comprises at least one of iron nitrate nonahydrate, iron chloride hexahydrate and iron sulfate nonahydrate.
10. A foamed carbon composite wave-absorbing material, characterized by, A method for preparing a foamed carbon composite wave-absorbing material as claimed in any one of claims 1 to 9.