Iron trioxide / porous carbon hetero-composite wave-absorbing material, preparation method and application thereof

Abstract

The application relates to a ferroferric oxide / porous carbon heterogeneous composite wave-absorbing material and a preparation method and application thereof. The ferroferric oxide of the application provides high magnetic permeability and saturation magnetization, the porous carbon formed by the covalent organic framework carbon with a regular structure can provide high conductive loss, the heterogeneous interface formed by the composite material provides rich interface polarization, different element compositions provide dipole polarization, and good electromagnetic coupling enables the material to have excellent impedance matching and electromagnetic loss capacity.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave protection, and specifically relates to a ferric oxide / porous carbon heterogeneous composite microwave absorbing material, its preparation method, and its application. Background Technology

[0002] With the rapid development of electromagnetic technology, the upgrading of various electronic components has greatly improved people's quality of life and accelerated social progress. However, electromagnetic pollution caused by electromagnetic technology has become the fourth largest source of pollution, which is not only harmful to human health but also has a great impact on communication equipment, threatening communication security. Therefore, there is an urgent need for high-performance absorbing materials with the characteristics of being "thin, light, wide, and strong".

[0003] Traditional ferrite absorbers possess high permeability and saturation magnetization, resulting in extremely strong magnetic loss capabilities. Carbon-based materials exhibit excellent electrical conductivity and a high dielectric constant, demonstrating strong dielectric loss capabilities. However, these two types of materials struggle to achieve good impedance matching, and relying on a single loss mechanism often fails to achieve significant electromagnetic wave attenuation. Currently, research on heterostructure ferrite / carbon electromagnetic coupling systems with high absorption performance is limited, and research on electromagnetic performance optimization processes is not yet fully underway. There is an urgent need to develop electromagnetic coupling composite materials that are easy to prepare and have good loss performance to meet the requirements of electromagnetic protection and electromagnetic stealth. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is to provide a ferric oxide / porous carbon heterogeneous composite microwave absorbing material, its preparation method, and its application, overcoming the defects of existing microwave absorbing agents such as single loss mode, poor loss capacity, high raw material cost, and cumbersome preparation.

[0005] This invention provides a covalent organic framework material containing imine groups, wherein the structural formula of the covalent organic framework material containing imine groups is as follows:

[0006]

[0007] This invention provides a ferric oxide / imine-based covalent organic framework composite material, wherein the composite material is a combination of the imine-containing covalent organic framework material and ferrite.

[0008] The ferrite is ferric oxide modified with a silane coupling agent; wherein the mass ratio of the ferrite to the imine-containing covalent organic framework material is 1:5 to 3:1, and further, the mass ratio is 1:2 to 3:1.

[0009] Preferably, the ferric oxide / imine-based covalent organic framework composite material is composed of ferric oxide modified with a silane coupling agent and a 2,4,6-tricarboxymethyl phloroglucinol-p-phenylenediamine covalent organic framework (TpPa-1-COF), which can be denoted as Fe2O3 / COF.

[0010] The silane coupling agent is 3-aminopropyltriethoxysilane (APTES).

[0011] The method for preparing the silane coupling agent modified ferric oxide includes:

[0012] (1) Sonicate ferric oxide in ethanol for 0.5-3 hours to obtain a mixed solution; wherein the ratio of ferric oxide to ethanol is 100-1000 mg: 50-500 mL;

[0013] (2) Mix the mixture of 3-aminopropyltriethoxysilane and ethanol with the mixture in step (1) and then sonicate for 1.5 to 4 hours, centrifuge and dry to obtain silane coupling agent modified ferric oxide; wherein the volume ratio of the total amount of ethanol (the sum of ethanol in steps 1 and 2) to 3-aminopropyltriethoxysilane is 200:1 to 50:1.

[0014] In step (2), centrifugation is performed using ethanol as the washing solvent, and the complex is centrifuged at 5000-10000 r / min for 5-20 min; drying is performed at 90-160℃ for 24-72 h.

[0015] This invention provides a ferric oxide / porous carbon composite material, wherein the ferric oxide / porous carbon material is obtained by high-temperature carbonization of raw materials containing any of the aforementioned ferric oxide / imine covalent organic framework composite materials to obtain a ferric oxide / porous carbon heterostructure microwave absorbing material.

[0016] This invention provides a ferric oxide / porous carbon composite material as a magnetoelectric coupling heterogeneous composite absorbing material for electromagnetic wave absorption.

[0017] This invention provides a method for preparing ferric oxide / porous carbon material composites, comprising:

[0018] Modified ferric oxide nanoparticles, aldehyde-containing aromatic compounds, and amino-containing aromatic compounds were mixed, and then 1,3,5-trimethylbenzene, 1,4-dioxane, and an acid solution were added. After complete dissolution, the mixture was reacted, washed, and dried to obtain a ferric oxide / imine-based covalent organic framework composite material. This composite material was then subjected to high-temperature carbonization to obtain a ferric oxide / porous carbon composite material, which is a ferric oxide / porous carbon heterostructure microwave absorbing material.

[0019] Preferably, the modified ferric oxide nanoparticles, aldehyde-containing aromatic compounds, and amino-containing aromatic compounds are mixed and placed in a Schlenk tube.

[0020] Preferably, the aldehyde-containing aromatic compound is 2,4,6-tricarboxymethyl phloroglucinol; the amino-containing aromatic compound is p-phenylenediamine; and the modified ferric oxide nanoparticles are silane coupling agent-modified ferric oxide.

[0021] Preferably, the mass ratio of the nano-ferric oxide, the aldehyde-containing aromatic compound, and the amino-containing aromatic compound is (0-10):(1-3):(1-9); more preferably, the mass ratio is (3-6):(1-2):(1-5).

[0022] Preferably, the volume ratio of 1,3,5-trimethylbenzene, 1,4-dioxane and acid solution is (1-5):(1-6):(1-3).

[0023] Preferably, the concentration of the acid solution is 1-5 mol / L; the acid solution is an aqueous solution of acetic acid.

[0024] Preferably, the reaction is carried out at 120-150°C for 48-96 hours; the vacuum drying temperature is 60-120°C and the time is 20-48 hours.

[0025] The washing process includes centrifugal washing and soaking washing.

[0026] The centrifugal washing process conditions are as follows: using tetrahydrofuran as the washing solvent, the complex is centrifuged at 5000-10000 r / min for 5-20 min; the soaking washing process conditions are as follows: soaking and washing with acetone at room temperature for 24-72 h.

[0027] Preferably, the high-temperature carbonization process parameters are: sintering temperature of 600-1000℃, heating rate of 3-6℃ / min, holding time of 1-6h, and the atmosphere used is an inert protective gas, such as N2 or Ar.

[0028] The present invention provides an electromagnetic wave absorbing device, wherein the device comprises the ferric oxide / porous carbon composite material.

[0029] The ferric oxide / porous carbon composite material of this invention can effectively absorb electromagnetic waves. The method for preparing the absorbing device is as follows: A molding method is used to fabricate the test component. To ensure uniform distribution of the prepared ferric oxide / porous carbon composite absorbing powder in paraffin wax, the paraffin wax is heated to 90°C until it is in a molten state. Then, the absorbing powder prepared in each embodiment is mixed with the molten paraffin wax (mass ratio of 5:5) and thoroughly ground. After the paraffin wax solidifies, the mixture is placed in a mold and pressed into shape. The dimensions of the cylindrical coaxial sample for electromagnetic performance testing are: inner diameter 3.04 mm, outer diameter 7 mm, and sample thickness ranging from 1 to 3 mm.

[0030] This invention provides an application of the aforementioned ferric oxide / porous carbon composite material in the field of electromagnetic wave absorption.

[0031] This invention utilizes two aromatic compounds, one containing amino groups and the other aldehyde groups, along with ferric oxide in an acidic environment. The aromatic compounds undergo dehydration and cyclization to form an imine-containing covalent organic framework material, which is then combined with ferrite to construct a ferric oxide / imine-based covalent organic framework composite material. After high-temperature carbonization, a ferric oxide / porous carbon heterostructure composite material is obtained. Using ferric oxide as the magnetic loss material and porous carbon as the dielectric loss material, the heterostructure formed by these two materials effectively modulates the impedance matching of the composite material, significantly enhancing its electromagnetic wave absorption performance and demonstrating high application value in electromagnetic radiation protection.

[0032] Beneficial effects

[0033] (1) This invention employs a novel Schiff-based reaction to synthesize a ferric oxide / imine-based covalent organic framework composite material, followed by high-temperature carbonization to synthesize a ferric oxide / porous carbon heterogeneous composite microwave absorbing material. This method provides a new approach to synthesizing high-performance electromagnetic coupling microwave absorbing materials. It utilizes aromatic compounds containing aldehyde and amino groups in an acidic environment, where the aromatic compounds dehydrate and form rings to create imine groups, constructing a covalent organic framework with a heterogeneous structure to ferric oxide. After high-temperature carbonization, the covalent organic framework becomes porous carbon, forming a ferric oxide / porous carbon heterogeneous composite microwave absorbing material.

[0034] (2) The ferric oxide of this invention provides high permeability and saturation magnetization. The porous carbon formed by carbonization of the covalent organic framework with a regular structure can provide high conductivity loss. The heterogeneous interface formed by the composite material provides rich interfacial polarization. The different elemental composition provides dipole polarization. Good electromagnetic coupling gives it excellent impedance matching and electromagnetic loss capability. The electromagnetic parameters of the absorber can be further controlled by adjusting the carbonization temperature. For example, when the mass ratio of the modified nano-ferric oxide, 2,4,6-tricarboxymethyl phloroglucinol and p-phenylenediamine in this invention is 4.28:1.31:1, the ferric oxide / porous carbon prepared by holding at 700℃ for 2h has a minimum reflection loss of -64.5dB at 15.35GHz when the thickness is 1.72mm. The absorption bandwidth of less than -10dB in the test frequency band of 2-18GHz reaches 4.92GHz.

[0035] (3) The heterostructured ferric oxide / porous carbon composite microwave absorbing material synthesized in this invention is easy to prepare, has a wide range of raw material sources, has high temperature resistance and corrosion resistance, can be used under harsh conditions, has good reproducibility and strong controllability. Attached Figure Description

[0036] Figure 1 X-ray diffraction patterns of the uncarbonized imine covalent organic framework prepared in Example 1 and the ferric oxide / imine covalent organic framework composites of Examples 2-5;

[0037] Figure 2 Fourier transform infrared spectra of the uncarbonized imine covalent organic framework prepared in Example 1 and the ferric oxide / imine covalent organic framework composites of Examples 2-5;

[0038] Figure 3 Scanning electron microscope (SEM) images of imine-based covalent organic frameworks and ferric oxide / porous carbon composite materials prepared in different embodiments; wherein (a) to (e) are SEM images of Examples 1 to 5, respectively;

[0039] Figure 4 This is an electromagnetic wave absorption characteristic diagram of the imine-based covalent organic framework prepared in Example 1;

[0040] Figure 5 The electromagnetic wave absorption characteristics of the ferric oxide / porous carbon composite material prepared in Example 2 are shown in the diagram.

[0041] Figure 6 This is an electromagnetic wave absorption characteristic diagram of the ferric oxide / porous carbon composite material prepared in Example 3;

[0042] Figure 7 The electromagnetic wave absorption characteristics of the ferric oxide / porous carbon composite material prepared in Example 4 are shown in the diagram.

[0043] Figure 8 This is an electromagnetic wave absorption characteristic diagram of the ferric oxide / porous carbon composite material prepared in Example 5. Detailed Implementation

[0044] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0045] Raw materials: 2,4,6-tricarboxymethyl phloroglucinol (Shanghai Haohong Biomedical Technology Co., Ltd.), p-phenylenediamine (Shanghai Mairui Biochemical Technology Co., Ltd.), 3-aminopropyltriethoxysilane (Shanghai Mairui Biochemical Technology Co., Ltd.), nano ferric oxide (Shanghai Aladdin Biochemical Technology Co., Ltd.), 1,3,5-trimethylbenzene (Sinopharm Chemical Reagent Co., Ltd.), 1,4-dioxane (Sinopharm Chemical Reagent Co., Ltd.), glacial acetic acid (Shanghai Lingfeng Chemical Reagent Co., Ltd.).

[0046] Instruments: Fourier transform infrared spectrometer (Thermo Scientific iD7 ATR), X-ray diffractometer (Bruke D8 Advance), field emission scanning electron microscope (Regulus 8230), vector network analyzer (R&S ZNB20).

[0047] The modified nano-ferric oxide is prepared as follows: 500 mg of ferric oxide is sonicated in 50 mL of ethanol for 1 h, then mixed with a mixture of 10 mL of ethanol and 300 μL of 3-aminopropyltriethoxysilane, and sonicated again for 1.5 h. After sonication, ethanol is used as the washing solvent, the composite is centrifuged at 8000 r / min for 10 min, and then dried at 100 °C for 24 h to obtain the final product.

[0048] Note: In the examples, Fe2O3 / COF refers to the modified Fe2O3.

[0049] Example 1

[0050] 2,4,6-Tricarboxymethyl phloroglucinol (63 mg, 0.30 mmol) and p-phenylenediamine (48 mg, 0.45 mmol) were mixed in a 10 mL Schlenk tube. 1,3,5-Trimethylbenzene (1.5 mL), 1,4-dioxane (1.5 mL), and an aqueous acetic acid solution (3 mol / L, 0.5 mL) were added, and the mixture was sonicated for 30 min to ensure homogeneity. The mixture was then reacted at 120 °C for 72 h. After the reaction, the mixture was centrifuged and washed three times, first with tetrahydrofuran at 8000 rpm for 5 min at room temperature, then soaked and washed with acetone at room temperature for 48 h, changing the solvent 5–6 times. Finally, it was dried in a vacuum oven at 60 °C for 24 h to obtain a pure imine-based covalent organic framework, denoted as TpPa-1-COF. Sintering was carried out at a sintering temperature of 600℃, with a heating rate of 3℃ / min and a holding time of 2h. The atmosphere used was N2, and this was denoted as COF-600-2h.

[0051] COF structural formula:

[0052] Example 2

[0053] Modified nano-ferric oxide (20.58 mg), 2,4,6-tricarboxymethyl phloroglucinol (63 mg, 0.30 mmol), and p-phenylenediamine (48 mg, 0.45 mmol) were mixed in a 10 mL Schlenk tube. 1,3,5-trimethylbenzene (1.5 mL), 1,4-dioxane (1.5 mL), and an aqueous acetic acid solution (3 mol / L, 0.5 mL) were added. The mixture was sonicated for 30 min to ensure homogeneity. The mixture was then reacted at 120 °C for 72 h. After the reaction, the mixture was centrifuged and washed three times, first with tetrahydrofuran at 8000 rpm for 5 min at room temperature, then soaked and washed with acetone at room temperature for 48 h, changing the solvent 5–6 times. Finally, it was dried in a vacuum oven at 60 °C for 24 h to obtain the ferric oxide / imine-based covalent organic framework composite material, denoted as Fe₂O₃ / COF₂ 2:9 by mass ratio. Sintering was carried out at a sintering temperature of 700℃, a heating rate of 3℃ / min, a holding time of 2h, and a N2 atmosphere to obtain a ferric oxide / porous carbon composite material, labeled as Fe2O3 / COF 2:9-700-2h.

[0054] Example 3

[0055] Modified nano-ferric oxide (72.03 mg), 2,4,6-tricarboxymethyl phloroglucinol (63 mg, 0.30 mmol), and p-phenylenediamine (48 mg, 0.45 mmol) were mixed in a 10 mL Schlenk tube. 1,3,5-trimethylbenzene (1.5 mL), 1,4-dioxane (1.5 mL), and an aqueous acetic acid solution (3 mol / L, 0.5 mL) were added, and the mixture was sonicated for 30 min to ensure homogeneity. The mixture was then reacted at 120 °C for 72 h. After the reaction, the mixture was centrifuged and washed three times, first with tetrahydrofuran at 8000 rpm for 5 min at room temperature, then soaked and washed with acetone at room temperature for 48 h, changing the solvent 5–6 times. Finally, it was dried in a vacuum oven at 60 °C for 24 h to obtain the ferric oxide / imine-based covalent organic framework composite material, denoted as Fe₂O₃ / COF₄ 3:4 by mass. Sintering was carried out at a sintering temperature of 800℃, with a heating rate of 3℃ / min and a holding time of 2h. The atmosphere used was N2, resulting in a ferric oxide / porous carbon composite material, denoted as Fe2O3 / COF 3:4-800-2h.

[0056] Example 4

[0057] Modified nano-ferric oxide (205.80 mg), 2,4,6-tricarboxymethyl phloroglucinol (63 mg, 0.30 mmol), and p-phenylenediamine (48 mg, 0.45 mmol) were mixed in a 10 mL Schlenk tube. 1,3,5-trimethylbenzene (1.5 mL), 1,4-dioxane (1.5 mL), and an aqueous acetic acid solution (3 mol / L, 0.5 mL) were added. The mixture was sonicated for 30 min to ensure homogeneity. The mixture was then reacted at 120 °C for 72 h. After the reaction, the mixture was centrifuged and washed three times, first with tetrahydrofuran at 8000 rpm for 5 min at room temperature, then soaked and washed with acetone at room temperature for 48 h, changing the solvent 5–6 times. Finally, it was dried in a vacuum oven at 60 °C for 24 h to obtain the ferric oxide / imine-based covalent organic framework composite material, denoted as Fe₂O₃ / COF₃ 2:1 by mass ratio. Sintering was carried out at a sintering temperature of 700℃, with a heating rate of 3℃ / min and a holding time of 2h. The atmosphere used was N2, resulting in a ferric oxide / porous carbon composite material, denoted as Fe2O3 / COF2:1-700-2h.

[0058] Example 5

[0059] Modified nano-ferric oxide (308.70 mg), 2,4,6-tricarboxymethyl phloroglucinol (63 mg, 0.30 mmol), and p-phenylenediamine (48 mg, 0.45 mmol) were mixed in a 10 mL Schlenk tube. 1,3,5-trimethylbenzene (1.5 mL), 1,4-dioxane (1.5 mL), and an aqueous acetic acid solution (3 mol / L, 0.5 mL) were added. The mixture was sonicated for 30 min to ensure homogeneity. The mixture was then reacted at 120 °C for 72 h. After the reaction, the mixture was centrifuged and washed three times, first with tetrahydrofuran at 8000 rpm for 5 min at room temperature, then soaked and washed with acetone at room temperature for 48 h, changing the solvent 5–6 times. Finally, it was dried in a vacuum oven at 60 °C for 24 h to obtain the ferric oxide / imine-based covalent organic framework composite material, denoted as Fe₂O₃ / COF₃ 3:1 by mass. Sintering was carried out at a sintering temperature of 800℃, with a heating rate of 3℃ / min and a holding time of 2h. The atmosphere used was N2, resulting in a ferric oxide / porous carbon composite material, denoted as Fe2O3 / COF 3:1-800-2h.

[0060] like Figure 1 The figures shown are X-ray diffraction patterns of COF and Fe2O3 / COF composite materials prepared in different embodiments. Figure 1 It can be seen that the diffraction peak at 4.7° is the crystallization peak of the covalent organic framework, and the sharp peak corresponds to the peak of ferric oxide. With the increase of ferric oxide addition, the defects of the covalent organic framework increase, its crystallinity decreases significantly, and the peak height increases. This relatively regular covalent organic framework with a certain degree of crystallinity exhibits high conductivity and strong conductive loss after carbonization.

[0061] like Figure 2 The figures shown are Fourier transform infrared spectra of COF and Fe2O3 / COF composite materials prepared in different embodiments. Figure 2 It can be seen that 1580cm -1 1250cm -1 The characteristic peaks at these locations represent the formation of C=C and CN bonds, respectively, proving the synthesis of covalent organic frameworks.

[0062] like Figure 3 (a) to (e) are scanning electron microscope images of Examples 1 to 5, respectively. Figure 3 It can be seen that, Figure 3 (a) is a scanning electron microscope image of TpPa-1-COF carbide material without the addition of ferric oxide; (b) to (e) show a distinct heterogeneous structure, with nanorods and nanospheres coexisting. Furthermore, the number of nanospheres increases significantly with increasing ferric oxide content. Figure 4The image shown is an electromagnetic wave absorption characteristic image of the ferric oxide / porous carbon composite absorbing material prepared in Example 4. Figure 4 As can be seen, the preparation method of the absorbing component is as follows: the test component is made by molding. In order to make the prepared ferric oxide / porous carbon composite absorbing powder uniformly distributed in paraffin wax, the paraffin wax is heated to 90°C to make it melted. Then, the absorbing powder prepared in each embodiment is mixed with the melted paraffin wax (mass ratio of 5:5) and ground thoroughly. After the paraffin wax solidifies, the mixture is placed in a mold and pressed into shape. The dimensions of the cylindrical coaxial sample for electromagnetic performance testing are as follows: inner diameter 3.04 mm, outer diameter 7 mm, and sample thickness ranging from 1 to 3 mm. Based on the obtained electromagnetic parameters, the transmission line theorem can be applied to calculate and evaluate the electromagnetic wave absorption performance of the prepared sample. Figures 4-8 The figures show the microwave absorption properties of the materials prepared in Examples 1-5, respectively. Figure 4 It can be seen that Example 1, with a thickness of 4.00 mm, has a minimum reflection loss of -3.90 dB at 10.80 GHz. From... Figure 5 It can be seen that Example 2, with a thickness of 4.50 mm, has a minimum reflection loss of -16.38 dB at 7.04 GHz. (From...) Figure 6 It can be seen that Example 3, with a thickness of 1.50 mm, has a minimum reflection loss of -22.39 dB at 17.11 GHz. From... Figure 7 It can be seen that, in Example 4, with a thickness of 1.72 mm, there is a minimum reflection loss of -64.5 dB at 15.35 GHz, and an absorption bandwidth of less than -10 dB reaches 4.92 GHz in the test frequency band of 2-18 GHz. From Figure 8 It can be seen that Example 5, with a thickness of 5.00 mm, exhibits a minimum reflection loss of -17.34 dB at 16.60 GHz. The electromagnetic parameters were controlled by adjusting the carburization temperature and the ferric oxide content, thereby enabling the material to achieve excellent electromagnetic wave absorption performance.

Claims

1. A ferric oxide / porous carbon composite material, characterized in that, The ferric oxide / porous carbon composite material is obtained by high-temperature carbonization of ferric oxide / imine-based covalent organic framework composite material; wherein the ferric oxide / imine-based covalent organic framework composite material is a composite of an imine-containing covalent organic framework material and a ferrite; the ferrite is ferric oxide modified with a silane coupling agent; The mass ratio of ferrite to imine-containing covalent organic framework material is 1:5 to 3:

1. The structural formula of the covalent organic framework material containing imine groups is as follows:

2. A method for preparing the ferric oxide / porous carbon composite material according to claim 1, comprising: Modified ferric oxide nanoparticles, aldehyde-containing aromatic compounds, and amino-containing aromatic compounds were mixed, and then 1,3,5-trimethylbenzene, 1,4-dioxane, and an acid solution were added. The mixture was reacted, washed, and dried to obtain a ferric oxide / imine-based covalent organic framework composite material. The composite material was then subjected to high-temperature carbonization to obtain a ferric oxide / porous carbon composite material.

3. The preparation method according to claim 2, characterized in that, The aldehyde-containing aromatic compound is 2,4,6-tricarboxymethyl phloroglucinol; the amino-containing aromatic compound is p-phenylenediamine; and the modified ferric oxide nanoparticles are silane coupling agent-modified ferric oxide.

4. The preparation method according to claim 2, characterized in that, The mass ratio of the modified nano-ferric oxide, the aldehyde-containing aromatic compound, and the amino-containing aromatic compound is (3-6):(1-2):(1-5); the volume ratio of the added 1,3,5-trimethylbenzene, 1,4-dioxane, and acid solution is (1-5):(1-6):(1-3); the concentration of the acid solution is 1-5 mol / L; and the acid solution is an aqueous acetic acid solution.

5. The preparation method according to claim 2, characterized in that, The reaction is carried out at 120-150℃ for 48-96 hours; the vacuum drying temperature is 60-120℃ and the time is 20-48 hours. The high-temperature carbonization process parameters are as follows: sintering temperature is 600-1000℃, heating rate is 3-6℃ / min, holding time is 1-6h, and the atmosphere used is at least one of N2 and Ar.

6. An electromagnetic wave absorbing device, characterized in that, The device comprises the ferric oxide / porous carbon composite material as described in claim 1.

7. The application of the ferric oxide / porous carbon composite material of claim 1 in the field of electromagnetic wave absorption.

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