EDC-Fe3O4 nano composite wave-absorbing material and preparation method thereof

Abstract

The invention discloses a preparation method of an EDC-Fe3O4 nano composite wave-absorbing material, which is characterized by comprising the following steps: preparing egg derived carbon with a porous structure by using an SiO2 template and taking eggs as a precursor, and then obtaining the EDC-Fe3O4 nano composite wave-absorbing material through a simple reflux calcining process. The method is simple in technological process, low in cost, environmentally friendly and good in repeatability, the minimum reflection loss (RLmin) of the obtained EDC-Fe3O4 nano-composite wave-absorbing material is-54.19 dB when the matching thickness is 2.46 mm, 99.99% of incident electromagnetic waves are effectively absorbed, the effective absorption bandwidth (EAB) of the EDC-Fe3O4 nano-composite wave-absorbing material reaches up to 5.68 GHz when the matching thickness is 2.03 mm, and broadband absorption of the electromagnetic waves is achieved. The electromagnetic wave absorbing material has excellent electromagnetic wave absorbing performance, also has the characteristics of light weight and small density, can play a good role in the field of absorbing electromagnetic wave radiation, and has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of nanomaterials and electromagnetic wave absorption, and specifically relates to a preparation method of EDC@Fe3O4 nanocomposite microwave absorption materials and a study on their electromagnetic wave absorption properties. Background Art

[0002] The development of science and technology and the wide application of wireless communication technology have brought convenience to human production and life, but at the same time have caused a large amount of electromagnetic radiation, affecting precision instruments and endangering human health. Nowadays, preparing suitable microwave absorption materials to prevent electromagnetic waves from affecting the normal operation of complex electronic devices and reducing the interference with the inherent magnetic field of the human body has become a key research issue. In recent years, to solve the problem of electromagnetic pollution, a large number of microwave absorption materials have been developed, including carbon materials, magnetic materials, polymer conductive materials, and ceramic materials. In contrast, it is a great challenge to prove good microwave absorption performance with a single electromagnetic loss mechanism. Therefore, composites with the synergistic effect of multiple loss mechanisms and well-matched impedance have become a more important goal. In addition, good structural design is also important for microwave absorption materials. A unique structure allows for multiple reflections of electromagnetic waves to form inside the absorber, thereby increasing the microwave absorption characteristics of the material.

[0003] It should be noted that single carbon materials are not magnetic, indicating that they only convert the energy of electromagnetic waves through dielectric loss. Moreover, the impedance matching of single carbon materials is poor, and electromagnetic waves are easily reflected on their surfaces and cannot enter the material interior for loss. For magnetic metal wave-absorbing materials, both pure metals and metal oxides have disadvantages such as high density, poor weather resistance and corrosion resistance, poor impedance matching, and narrow wave-absorbing frequency. Combining the characteristics of both, carbon-based magnetic composites can exhibit strong electromagnetic wave absorption performance because there is a significant synergistic or complementary behavior between carbon and magnetic materials, which can avoid single disadvantages and effectively improve the wave-absorbing performance. For example, Hou et al. used waste pomelo peel as a biomass carbon source and prepared the CoFe2O4 / C / PANI wave-absorbing material with multiple loss mechanisms through hydrothermal, carbonization, and polymerization processes, enabling the biomass carbon derived from pomelo peel to be compounded with metal oxide CoFe2O4 and polyaniline, showing excellent electromagnetic wave absorption performance. (Hou, T.Q.; Jia, Z.R.; Feng, A.L.; Zhou, Z.H.; Liu, X.H.; Lv, H.L.; Wu, G.L.. Journal of Materials Science & Technology 2021, 68: 61-69.) Another example is that Liu et al. synthesized hollow Fe3O4 microspheres encapsulated by single-walled carbon nanohorns through a simple solvothermal method. When the matching thickness of the obtained H-Fe3O4@SWCNHs composite material is 2.0 mm, the minimum reflection loss value of the composite material at 13.6 GHz is -42.2 dB, and the maximum effective absorption bandwidth value in the range of 11.8 to 18 GHz is 6.2 GHz. The excellent microwave absorption performance is mainly attributed to its unique hollow core-shell structure, optimal impedance matching, and the synergistic effect of dielectric loss and magnetic loss. (Y. Liu, J. Zhang, Q. Gao, R. Hu, Fabrication of hollow Fe3O4 microspheres encapsulated by single-walled carbon nanohorns for high-performance microwave absorption, Ceramics International 2024, 50(24): 55879-55891.)

[0004] In this patent, carbon-based materials and Fe3O4 magnetic materials are compounded, and the microwave absorption ability of the EDC@Fe3O4 nanocomposite wave-absorbing material is improved through the synergistic action of multiple loss mechanisms, giving it broad application prospects in the field of electromagnetic wave absorption. Summary of the Invention

[0005] The object of the present invention is to provide a wave-absorbing material composed of an egg-derived carbon material and iron tetroxide and a preparation method thereof, the preparation process of which is simple, efficient, low-cost and environmentally friendly. Using eggs as a precursor, porous egg-derived carbon is prepared by using a SiO2 template, and then through a simple reflux calcination process, an EDC@Fe3O4 nanocomposite wave-absorbing material is obtained. The obtained EDC@Fe3O4 nanocomposite wave-absorbing material has excellent electromagnetic wave absorption performance.

[0006] The object of the present invention is achieved by the following technical solutions:

[0007] (1) Add 0.75 g of SiO2 microspheres with a diameter of 200 nm to 50 g of well-mixed egg liquid. After ultrasonic dispersion for 1 h, use strong mechanical stirring and stir at a speed of 1500 r / min for 2 h. Then use a steamed egg cooker to steam the egg liquid and freeze-dry it for 48 h. Put the freeze-dried precursor into a tube furnace and keep it at 850 °C for 2 h in an argon atmosphere to obtain an EC@SiO2 material.

[0008] (2) Immerse the EC@SiO2 material in 3 mol / L hydrofluoric acid for 48 h, wash it by centrifugation with deionized water until neutral, and dry it to obtain three-dimensionally ordered porous egg-derived carbon (EDC).

[0009] (3) Add 0.6 g of Fe(NO3)3★9H2O and 0.6 g of urea to 200 ml of deionized water, stir and dissolve them, add 0.3 g of three-dimensionally porous egg-derived carbon material, set the reflux temperature at 120 °C for 6 h, and centrifuge to obtain a solid precursor. Dry and grind it at 60 °C, and keep the dried product at 500 °C for 6 h in an argon atmosphere to obtain an EDC@Fe3O4 nanocomposite wave-absorbing material.

[0010] The present invention uses eggs as a precursor, uses a SiO2 template to prepare porous egg-derived carbon, and then through a simple reflux calcination process, an EDC@Fe3O4 nanocomposite wave-absorbing material is obtained. The raw materials used in the present invention are green, pollution-free, low-cost, and the process is simple, efficient, highly repeatable, and easy to achieve mass production. The prepared EDC@Fe3O4 nanocomposite wave-absorbing material as an electromagnetic wave absorber has the advantages of light weight, small density, high absorption intensity, wide absorption frequency band range, small matching thickness, etc. Its minimum reflection loss can reach -54.19 dB at a matching thickness of 2.46 mm, and at the same time, the maximum effective absorption bandwidth (EAB) is 5.68 GHz at a thickness of 2.03 mm, showing excellent electromagnetic wave absorption performance. It is precisely because a single carbon material does not have good attenuation coefficient and impedance matching, so magnetic metal oxide Fe3O4 is introduced to improve its attenuation ability and impedance matching. min ) can reach -54.19 dB, and at the same time, the maximum effective absorption bandwidth (EAB) at a thickness of 2.03 mm is 5.68 GHz, showing excellent electromagnetic wave absorption performance.

[0011] (1) The porous structure of egg-derived carbon forms a conductive network inside the material, which can greatly improve the conductivity of the material, thereby enhancing the induced current induced by electromagnetic waves, enabling the material to effectively convert electromagnetic waves into heat energy.

[0012] (2) The porous structure loaded with flower-like Fe3O4 particles enables the material to form multiple reflections on electromagnetic waves, allowing electromagnetic waves to enter the material interior multiple times, improving the impedance matching of the material. Moreover, the air-material and dielectric loss-magnetic loss interfaces can provide multiple options for the energy conversion of electromagnetic waves in the material and provide an interfacial polarization effect.

[0013] (3) After high-temperature calcination, the nitrogen, oxygen, and phosphorus atoms rich in eggs are doped in the carbon, forming impurity atoms. These impurity atoms act as dipoles in the electromagnetic field, generating a polarization effect, enabling the material to have good polarization loss and effectively dissipating the energy of the electromagnetic field. In addition, the introduction of magnetic Fe3O4 particles can enable the material to generate good natural resonance loss and eddy current loss, making the dielectric loss and magnetic loss composite, and multiple loss mechanisms act simultaneously, thereby further enhancing the electromagnetic wave loss. Description of the Drawings

[0014] Figure 1 SEM image of the EC@SiO2 microwave absorbing material prepared in Specific Example 1.

[0015] Figure 2 SEM image of the EDC microwave absorbing material prepared in Specific Example 1.

[0016] Figure 3 SEM image of the EDC@Fe3O4 microwave absorbing material prepared in Specific Example 1.

[0017] Figure 4 TEM image of the EDC@Fe3O4 nanocomposite microwave absorbing material prepared in Specific Example 1.

[0018] Figure 5 XRD comparison chart of the EDC and EDC@Fe3O4 nanocomposite materials prepared in Specific Example 1.

[0019] Figure 6 Raman chart of the EDC@Fe3O4 nanocomposite microwave absorbing material prepared in Specific Example 1.

[0020] Figure 7 Hysteresis loop chart of the EDC@Fe3O4 nanocomposite microwave absorbing material prepared in Specific Example 1.

[0021] Figure 8 XPS chart of the EDC@Fe3O4 nanocomposite microwave absorbing material prepared in Specific Example 1.

[0022] Figure 9 Reflection loss diagram of the EDC nano-composite wave-absorbing material prepared in Specific Example 1.

[0023] Figure 10 Reflection loss diagram of the EDC@Fe3O4 nano-composite wave-absorbing material prepared in Specific Example 1. Specific implementation manners

[0024] The following further elaborates on the present invention in conjunction with specific implementation schemes, but these examples do not limit the scope of the present invention in any way.

[0025] Example 1

[0026] A preparation method of an EDC@Fe3O4 nano-composite wave-absorbing material includes the following operations:

[0027] (1) Add 0.75 g of SiO2 microspheres with a diameter of 200 nm to 50 g of well-mixed egg liquid. After ultrasonic dispersion for 1 h, use strong mechanical stirring and stir at a speed of 1500 r / min for 2 h. Then use a steamed egg cooker to steam the egg liquid and freeze-dry it for 48 h. Put the freeze-dried precursor into a tubular furnace and keep it at 850 °C for 2 h under an argon atmosphere to obtain the EC@SiO2 material.

[0028] (2) Immerse the EC@SiO2 material in 3 mol / L hydrofluoric acid for 48 h, wash it by centrifugation with deionized water until neutral, and dry it to obtain three-dimensional ordered porous egg-derived carbon (EDC). Add 0.6 g of Fe(NO3)★9H2O and 0.6 g of urea to 200 ml of deionized water, stir and dissolve them, add 0.3 g of the three-dimensional porous egg-derived carbon material, set the reflux temperature at 120 °C for 6 h, and centrifuge to obtain a solid precursor. Dry it at 60 °C, and keep the dried product at 500 °C for 6 h under an argon atmosphere to obtain the EDC@Fe3O4 nano-composite wave-absorbing material.

[0029] On the basis of obtaining egg-derived carbon, by adding SiO2 microspheres, a large number of pores are created in the egg-derived carbon, as Figure 1 shown to construct the EC@SiO2 nano-composite material. It can be seen from the SEM image that there are a large number of SiO2 microspheres with a diameter of 200 nm. After removing the SiO2 template microspheres by HF, three-dimensional ordered porous egg-derived carbon ( Figure 2 ) is obtained. It can be seen from the figure that a large number of pores with a diameter of about 200 nm appear, and these pores are relatively evenly distributed without agglomeration. Figure 3This is the SEM image of EDC@Fe3O4 loaded with Fe3O4 magnetic material after reflux. It can be seen that there is no significant change after loading Fe3O4, indicating that the loading process does not damage the basic structural framework of the porous carbon. Fe3O4 can be loaded on the porous carbon without affecting the overall structure, realizing functional modification without changing the main morphological characteristics of the substrate material. Figure 4 This is the TEM image of the EDC@Fe3O4 sample obtained at a magnification of 1 micron. A large number of pores show a porous foam-like structure, and the pores remain independent of each other, enabling the carbon to form a good network. Inside the pores of the porous material, flower-like Fe3O4 particles are filled. The loading distribution of Fe3O4 particles will generate a rich interfacial polarization phenomenon.

[0030] The phase characterization of the EDC and EDC@Fe3O4 nano-absorbents was carried out by X-ray diffraction, as Figure 5 shown. The XRD patterns of the two samples both have a similar wide diffraction peak at around 26°, which corresponds to the (002) crystal plane of egg-derived carbon (JCPDS 41-1487). Since EDC is a pure carbon material, the (002) peak is stronger. The carbon peak of EDC@Fe3O4 is lower in intensity and wider, indicating lower carbon crystallinity. In addition, diffraction peaks appear at 30.09°, 35.42°, 43.05°, 56.94° and 62.51° in the EDC@Fe3O4 sample. These diffraction peaks correspond to the (220), (311), (400), (511) and (440) crystal planes of magnetite Fe3O4 (JCPDS19-0629). It can be seen that these diffraction peaks are higher in intensity and sharper, indicating good crystallinity of the Fe3O4 particles after high-temperature calcination.

[0031] The Raman spectrum of the EDC@Fe3O4 nanocomposite is as Figure 6 shown. Two characteristic peaks, the D band and the G band, appear at 1335 cm -1 and 1590 cm -1 . Among them, the D peak corresponds to sp 3 hybridized carbon, which is related to disordered or defective carbon. The G peak represents the radical C-C stretching mode formed by sp 2 bonded carbon in the graphite structure, reflecting the order and symmetry of carbon in the graphite structure. Figure 7 This shows the hysteresis loop of EDC@Fe3O4 at room temperature. It can be seen from the figure that the EDC@Fe3O4 sample exhibits typical ferromagnetic properties, and the magnetization intensity is in the range of 40-60 emu / g. Figure 7The thumbnail shows the coercivity and remanent magnetization of the sample. The intersection of the hysteresis loop curve and its abscissa represents the coercivity of the material, and the intersection with the ordinate represents the remanent magnetization of the material. It can be seen from the figure that the coercivity of the EDC@Fe3O4 sample is 192.6 Oe and the remanent magnetization is 7.11 emu / g. This indicates that the material has excellent magnetization ability and stable magnetic properties, and can enhance the attenuation of electromagnetic waves through the eddy current effect.

[0032] Figure 8 The XPS curve of the EDC@Fe3O4 sample can show the elemental composition and bonding type of the sample. It can be clearly obtained that the characteristic peaks of O1s ( Figure 8 b), Fe 2p ( Figure 8 c), C1s ( Figure 8 d). Figure 8 The O1s spectrum in b can be divided into three parts. The peak positions with binding energies of 531.8 eV, 533.2 eV, and 533.9 eV are attributed to Fe-O, C=O, and C-OH respectively. Figure 8 c is the Fe 2p spectrum. The peaks with binding energies of 711.98 eV and 725.38 eV are attributed to Fe 2p3 / 2 and Fe 2p1 / 2. Figure 8 The C1s spectrum in c can be divided into three parts. The peak positions with binding energies of 284.6 eV, 285.5 eV, and 288.7 eV are attributed to C-C, C-OH, and C=O respectively.

[0033] Observation Figure 9 of the EDC microwave absorption performance test results shows that when the matching thickness is 5.42 mm, the RL min value is only -22.69 dB, and the absorption bandwidth is 2.88 GHz at a matching thickness of 5.29 mm. This indicates that the microwave absorption performance of the EDC material is poor. And it can be observed from Figure 10 that after loading Fe3O4 magnetic particles, the microwave absorption performance is significantly improved under the action of magnetic loss. For EDC@Fe3O4, at a matching thickness of 2.46 mm, the reflection loss value reaches -54.19 dB at 9.12 GHz, and the absorption bandwidth reaches 5.68 GHz at a matching thickness of 2.03 mm. This shows that loading Fe3O4 magnetic particles effectively improves the microwave absorption performance. All results indicate that the EDC@Fe3O4 nanocomposite has excellent electromagnetic wave absorption ability and a relatively thin matching thickness.

Claims

1. A method for preparing an EDC@Fe3O4 nanocomposite absorbing material, characterized in that: using eggs as precursors, using SiO2 templates to prepare porous egg-derived carbon, and then undergoing a simple reflux calcination process to obtain the EDC@Fe3O4 nanocomposite absorbing material. The composite porous absorber is prepared by a simple template method and a reflux method. The main steps are as follows: (1) Add 0.75 g of SiO2 microspheres with a diameter of 200 nm to 50 g of uniformly mixed egg liquid, disperse by ultrasonication for 1 h, and then stir at a speed of 1500 r / min for 2 h using a strong mechanical stirrer. Then, steam the egg liquid using an egg steamer and freeze-dry it for 48 h. Place the freeze-dried precursor in a tube furnace and heat it at 850 ° C for 2 h under an argon atmosphere to obtain EC@SiO2 material. (2) The EC@SiO2 material was immersed in 3 mol / L hydrofluoric acid for 48 h, washed by centrifugation with deionized water until neutral, and dried to obtain three-dimensional ordered porous egg-derived carbon (EDC). (3) Add 0.6 g of Fe(NO3)3★9H2O and 0.6 g of urea to 200 ml of deionized water and stir to dissolve, add 0.3 g of three-dimensional porous egg-derived carbon material, set the temperature at 120°C to reflux for 6 h, and centrifuge to obtain a solid precursor. Dry and grind at 60°C, and keep the dried product at 500°C for 6 h in an argon atmosphere to obtain an EDC@Fe3O4 nanocomposite absorber.

2. An EDC@Fe3O4 nanocomposite absorbing material as claimed in claim 1, characterized in that: When the matching thickness is 2.46mm, the minimum reflection loss (RL min ) is -54.19dB, which has achieved 99.99% effective absorption of the incident electromagnetic waves, and when the matching thickness is 2.03mm, its effective absorption bandwidth (EAB) is 5.68GHz, achieving broadband absorption of electromagnetic waves.

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