CN113265223B - Nitrogen-doped iron-carbon composite wave-absorbing material and preparation method and application thereof - Google Patents

Nitrogen-doped iron-carbon composite wave-absorbing material and preparation method and application thereof Download PDF

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CN113265223B
CN113265223B CN202110567910.8A CN202110567910A CN113265223B CN 113265223 B CN113265223 B CN 113265223B CN 202110567910 A CN202110567910 A CN 202110567910A CN 113265223 B CN113265223 B CN 113265223B
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iron
absorbing material
carbon composite
composite wave
nitrogen
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CN113265223A (en
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梁瑾
孔杰
龚旻
高本征
罗波
陈军
赵彬男
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Northwestern Polytechnical University
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Abstract

The invention discloses a nitrogen-doped iron-carbon composite wave-absorbing material as well as a preparation method and application thereof, belonging to the technical field of wave-absorbing materials, wherein the preparation method comprises the following steps: uniformly dispersing iron salt and a carbon source serving as raw materials in an aqueous solvent, and reacting at 80-100 ℃ for 4-12 hours to obtain an iron-carbon composite wave-absorbing material precursor; and (3) uniformly mixing the obtained iron-carbon composite wave-absorbing material precursor with a nitrogen source, and then preserving the heat for 1-3 hours at 700-900 ℃ in an argon-hydrogen mixed gas atmosphere to obtain a black solid crude product, wherein the crude product is subjected to post-treatment to obtain the iron-carbon composite wave-absorbing material. The invention successfully prepares the iron-carbon composite wave-absorbing material with the shape of the carbon nano-tube and strong absorption in the X wave band in situ by a simple process.

Description

Nitrogen-doped iron-carbon composite wave-absorbing material and preparation method and application thereof
Technical Field
The invention relates to the technical field of wave-absorbing materials, in particular to an iron-carbon composite wave-absorbing material based on nitrogen doping and a preparation method and application thereof.
Background
In recent years, with the rapid development of science and technology, the application of electromagnetic technology is more and more extensive, and the electromagnetic waves can not be separated from equipment such as radio wave communication, radar detection, medical treatment and the like. However, electromagnetic waves bring convenience and may generate electromagnetic pollution to the environment, which causes health hidden dangers to human bodies and reduces the negative influence of the electromagnetic waves on the normal life of human bodies, at present, two methods are mainly adopted for preventing electromagnetic wave pollution, firstly, the high conductivity of materials is utilized to generate a shielding effect to protect devices from being infected by the electromagnetic waves, but the electromagnetic pollution cannot be thoroughly solved by reflecting a large amount of electromagnetic waves. Therefore, an electromagnetic absorption mechanism is needed to be used for treating electromagnetic pollution in a specific field, and the electromagnetic pollution can be fundamentally eliminated by using the electromagnetic absorption mechanism.
Ferrite is a composite metal oxide which takes iron and other iron group metal oxides as main components, has good dielectric property and has electromagnetic loss. Hysteresis loss, eddy current loss and natural resonance, dielectric loss are the main loss sources in the low frequency band and high frequency region. Although the density is high, the absorption strength and the absorption width can be compatible with each other when the coating thickness is small. The material is low in price and wide in source, and is widely used in the fields of military affairs, darkrooms, electromagnetic protection and electromagnetic interference prevention at present. Spinel type and magnetoplumbite type are the most main research objects at present, and the difference of crystal structures causes the wave absorbing performance of the two structures to be different.
The prior art discloses a method for preparing two Fe/C Nanofiber (CNF) electromagnetic wave absorbing materials through an electrostatic spinning-pyrolysis way, wherein CNFwater is prepared by taking water/ethanol as a solvent system, and CNFDMF is obtained by taking N, N-Dimethylformamide (DMF)/ethanol as the solvent system. However, the solvent system used in the prior art has toxicity, the solvent ratio has a large influence on the size of the product, large-scale mass production cannot be met, and meanwhile, the performance of the obtained iron-carbon composite material is poor, and the electromagnetic parameters cannot be flexibly adjusted, so that the practical application of the iron-carbon composite material is limited. Therefore, the invention provides the iron-carbon composite wave-absorbing material with excellent performance, adjustable electromagnetic parameters and based on the nitrogen-doped cementite.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides a nitrogen-doped iron-carbon composite wave-absorbing material as well as a preparation method and application thereof.
The invention relates to a nitrogen-doped iron-carbon composite wave-absorbing material, a preparation method and application thereof, which are specifically realized by the following technical scheme:
the invention aims to provide a preparation method of a nitrogen-doped iron-carbon composite wave-absorbing material, which comprises the following steps:
ferric salt and a carbon source are taken as raw materials and fully dissolved in a water solvent;
reacting the dissolved liquid at 80-100 ℃ for 4-12 hours, and drying to obtain an iron-carbon composite wave-absorbing material precursor;
and (3) uniformly mixing the obtained iron-carbon composite wave-absorbing material precursor with a nitrogen source, and then preserving the heat for 1-3 hours at 700-900 ℃ in an argon-hydrogen mixed gas atmosphere to obtain a black solid crude product, wherein the crude product is subjected to post-treatment to obtain the iron-carbon composite wave-absorbing material.
Further, the mass ratio of the iron salt to the carbon source is 1: 1-4.
Further, the mass ratio of the iron-carbon composite wave-absorbing material precursor to the nitrogen source is 1: 9-11.
Further, the ferric salt is ferric nitrate;
the carbon source is PVPK-30;
the nitrogen source is one or more of dicyandiamide, hexamethylenetetramine, urea and phenolic resin.
Further, the dosage ratio of the water solvent to the carbon source is 5-15 mL: 1g of the total weight of the composition.
Further, the volume ratio of argon to hydrogen in the mixed gas is 9: 1.
further, when the temperature is kept in the argon-hydrogen mixed gas atmosphere, the heating rate is 5-10 ℃/min.
Further, the post-treatment is to uniformly disperse the crude product in 0.1-4M hydrochloric acid, and the iron-carbon composite wave-absorbing material is obtained after heating, acid washing, refluxing, centrifuging, washing and drying; the dosage ratio of the hydrochloric acid to the crude product is 0.4L: 1 g.
The invention also aims to provide the iron-carbon composite wave-absorbing material prepared by the preparation method.
The invention also aims to provide an application of the iron-carbon composite wave-absorbing material in the aspect of absorbing electromagnetic waves.
Compared with the prior art, the invention has the following beneficial effects:
1) the preparation method has simple process, the used solvent system is nontoxic, and the preparation method accords with the concept of green synthesis, and the in-situ growth carbon nanotube wave-absorbing material can be prepared by the preparation method;
2) the frequency range of the iron-carbon composite wave-absorbing material is 2-18GHz (namely covering Ku wave band, X wave band and C wave band), and the electromagnetic parameters of the iron-carbon composite wave-absorbing material can be adjusted in a certain range through pyrolysis temperature;
3) the iron-carbon composite wave-absorbing material can form a local conductive network due to the high length-diameter ratio and the low loading of the carbon nano-tubes, ensures the wave-absorbing performance, successfully reduces the loading of the wave-absorbing agent, provides a theoretical basis for the research and development of light wave-absorbing materials, and has important academic significance and practical value.
4) The iron-carbon composite wave-absorbing material has the advantages of high carbon skeleton ordering degree, increased pore volume, increased effective dielectric constant of the wave-absorbing agent, reduced loading capacity, high anisotropy, electromagnetic energy consumption up to 99.999 percent and good wave-absorbing performance.
5) The carbon nanotube formed by the iron-carbon composite wave-absorbing material has high specific surface area, is favorable for interface polarization, has high porosity and is favorable for multiple reflection loss of electromagnetic waves, and the carbon nanotube with the length of about 350nm can absorb the electromagnetic waves to the maximum extent.
6) The iron-carbon composite wave-absorbing material is light in weight and excellent in performance, and tested by Fe 3 The true density of the C/Fe/NC iron-carbon composite wave-absorbing material is only 2.18g/cm 3 Typically a lightweight material.
Drawings
FIG. 1 is an electron microscope image of the iron-carbon composite wave-absorbing material of the present invention; wherein, fig. 1(a) is an SEM spectrogram of the iron-carbon composite wave-absorbing material of example 2, and fig. 1(b) -fig. 1(d) are TEM photographs of example 2 with different dimensions;
FIG. 2 is an XPS spectrum of an iron-carbon composite wave-absorbing material of the present invention; wherein, fig. 2(a) is an XPS full spectrum of the iron-carbon composite wave-absorbing material of examples 1-3, fig. 2(b) is a C1s spectrum of the iron-carbon composite wave-absorbing material of example 2, fig. 2(C) is an N1s spectrum of the iron-carbon composite wave-absorbing material of example 2, and fig. 2(d) is an Fe2p spectrum of the iron-carbon composite wave-absorbing material of example 2;
FIG. 3 is an XRD spectrogram and a Raman spectrogram of the iron-carbon composite wave-absorbing material; wherein, fig. 3(a) is an XRD spectrogram of the iron-carbon composite wave-absorbing material of example 1, example 2 and example 3; fig. 3(b) is a Raman spectrum of the iron-carbon composite wave-absorbing materials of example 1, example 2 and example 3;
FIG. 4 shows the electromagnetic parameters of the iron-carbon composite wave-absorbing material of the present invention; wherein, fig. 4(a) shows the dielectric real parts of the iron-carbon composite wave-absorbing materials of example 1, example 2 and example 3; fig. 4(b) is a dielectric imaginary part of the iron-carbon composite wave-absorbing material in example 1, example 2 and example 3; FIG. 4(c) is the real part of the magnetic permeability of the iron-carbon composite wave-absorbing material of example 1, example 2 and example 3; fig. 4(d) is the imaginary part of the magnetic permeability of the iron-carbon composite wave-absorbing material in example 1, example 2 and example 3; FIG. 4(e) is the dielectric loss tangent of the iron-carbon composite wave-absorbing materials of example 1, example 2 and example 3; fig. 4(f) is the magnetic loss tangent of the iron-carbon composite wave-absorbing material of example 1, example 2 and example 3;
FIG. 5 is a RL drawing and a RL projection drawing of the iron-carbon composite wave-absorbing material of the invention; wherein, fig. 5(a) is an RL diagram of the iron-carbon composite wave-absorbing material of example 1; FIG. 5(b) is a RL projection view of the iron-carbon composite wave-absorbing material in example 1; FIG. 5(c) is an RL diagram of the iron-carbon composite wave-absorbing material of example 2; FIG. 5(d) is a RL projection of the iron-carbon composite wave-absorbing material in example 2; FIG. 5(c) is an RL diagram of the iron-carbon composite wave-absorbing material of example 3; fig. 5(d) is a RL projection of the iron-carbon composite wave-absorbing material in example 3.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
Example 1
The embodiment provides a preparation method of an iron-carbon composite wave-absorbing material based on nitrogen doping, which comprises the following steps:
1.5g Fe (NO) 3 ) 3 ·9H 2 Placing O and 3g of PVPK-30 into a beaker filled with 30mL of deionized water, and carrying out ultrasonic treatment in an ultrasonic cleaner until a sample is fully dissolved to obtain a brownish red liquid;
putting the uniformly dispersed liquid into a beaker, reacting for 8 hours at the temperature of 90 ℃ in an oil bath, drying until the water is completely evaporated to obtain a dark brown solid product, and grinding the dark brown solid product into powder to obtain an iron-carbon composite wave-absorbing material precursor;
weighing the precursor of the iron-carbon composite wave-absorbing material and dicyandiamide according to the mass ratio of 1:10, uniformly mixing, putting into a crucible, and adding into Ar (90%)/H 2 (10%) heating to 700 ℃ at a heating rate of 5 ℃/min under a mixed atmosphere, preserving heat for 2 hours, and cooling along with a furnace to obtain a crude product in a black solid state;
and adding 50mg of the crude product into a round-bottom flask filled with 20mL of 4MHCl, performing ultrasonic treatment at room temperature to uniformly disperse the mixture, heating and acid-washing the mixture in an oil bath at 90 ℃ for reflux for 12 hours, then performing centrifugal washing by using deionized water and ethanol to remove impurities, and drying to obtain the iron-carbon-iron-carbon composite wave-absorbing material, which is named as Fe-I.
In the embodiment, dicyandiamide is used as a raw material, and electron-rich nitrogen is introduced into the material, so that the conductivity of the material can be greatly improved, and the absorption of electromagnetic waves is facilitated.
The metal iron ions of the embodiment form metal particles in the subsequent pyrolysis process, on one hand, the small-size metal particles can improve the snoke limit of the material, and on the other hand, the presence of the iron metal particles can improve the impedance matching of the material, the ferromagnetic resonance caused by the magnetic-based metal, the eddy current loss and the like can increase the absorption capacity of the material for electromagnetic waves.
Example 2
The embodiment provides a preparation method of a nitrogen-doped iron-carbon composite wave-absorbing material, which comprises the following steps of:
1.5g Fe (NO) 3 ) 3 ·9H 2 Placing O and 3g of PVPK-30 into a beaker filled with 30mL of deionized water, and carrying out ultrasonic treatment in an ultrasonic cleaner until a sample is fully dissolved to obtain a brownish red liquid;
putting the uniformly dispersed liquid into a beaker, reacting for 8 hours at the temperature of 90 ℃ in an oil bath, drying until the water is completely evaporated to obtain a dark brown solid product, and grinding the dark brown solid product into powder to obtain an iron-carbon composite wave absorbing material precursor;
weighing the precursor of the iron-carbon composite wave-absorbing material and dicyandiamide according to the mass ratio of 1:10, uniformly mixing, putting into a crucible, and adding Ar (90%)/H 2 (10%) heating to 800 ℃ at a heating rate of 5 ℃/min under a mixed atmosphere, preserving heat for 2 hours, and cooling along with a furnace to obtain a black solid crude product;
and adding 50mg of the crude product into a round-bottom flask filled with 20mL of 4MHCl, performing ultrasonic treatment at room temperature to uniformly disperse the mixture, heating and acid-washing the mixture in an oil bath at 90 ℃ for reflux for 12 hours, then performing centrifugal washing by using deionized water and ethanol to remove impurities, and drying to obtain the iron-carbon-iron-carbon composite wave-absorbing material named as Fe-II.
In the embodiment, dicyandiamide is used as a raw material, and electron-rich nitrogen is introduced into the material, so that the conductivity of the material can be greatly improved, and the absorption of electromagnetic waves is facilitated.
Example 3
The embodiment provides a preparation method of an iron-carbon composite wave-absorbing material based on nitrogen doping, which comprises the following steps:
1.5g Fe (NO) 3 ) 3 ·9H 2 Placing O and 3g of PVPK-30 into a beaker filled with 30mL of deionized water, and carrying out ultrasonic treatment in an ultrasonic cleaner until a sample is fully dissolved to obtain a brownish red liquid;
putting the uniformly dispersed liquid into a beaker, reacting for 8 hours at the temperature of 90 ℃ in an oil bath, drying until the water is completely evaporated to obtain a dark brown solid product, and grinding the dark brown solid product into powder to obtain an iron-carbon composite wave-absorbing material precursor;
weighing iron-carbon composite wave absorbing material with corresponding mass according to the mass ratio of 1:10The material precursor and dicyandiamide are mixed evenly and put into a crucible in Ar (90%)/H 2 (10%) heating to 900 ℃ at a heating rate of 5 ℃/min under a mixed atmosphere, preserving heat for 2 hours, and cooling along with the furnace to obtain a black solid crude product;
and adding 50mg of the crude product into a round-bottom flask filled with 20mL of 4MHCl, performing ultrasonic treatment at room temperature to uniformly disperse the mixture, heating and acid-washing the mixture in an oil bath at 90 ℃ for reflux for 12 hours, performing centrifugal washing by using deionized water and ethanol, and drying to obtain the iron-carbon-iron-carbon composite wave-absorbing material, which is named as Fe-III.
In the embodiment, dicyandiamide is used as a raw material, and electron-rich nitrogen is introduced into the material, so that the conductivity of the material can be greatly improved, and the absorption of electromagnetic waves is facilitated.
Example 4
The embodiment of the invention provides a preparation method of a nitrogen-doped iron-carbon composite wave-absorbing material, which comprises the following steps:
1.5g Fe (NO) 3 ) 3 ·9H 2 Placing O and 6g of PVPK-30 into a beaker filled with 90mL of deionized water, and carrying out ultrasonic treatment in an ultrasonic cleaner until the sample is uniformly dispersed;
putting the uniformly dispersed liquid into a beaker, reacting for 8 hours at the temperature of 80 ℃, drying the product until the water is completely evaporated, and grinding the product into powder to obtain an iron-carbon composite wave-absorbing material precursor;
weighing corresponding iron-carbon composite wave-absorbing material precursor and hexamethylenetetramine according to the mass ratio of 1:9, uniformly mixing, putting into a crucible, and adding Ar (90%)/H 2 (10%) heating to 900 ℃ at a heating rate of 10 ℃/min under a mixed atmosphere, preserving heat for 1 hour, and cooling along with the furnace to obtain a black solid product;
and adding 50mg of black product into a round bottom flask containing 20mL of 2MHCl, performing ultrasonic treatment at room temperature until the mixture is uniformly dispersed, heating and acid-washing in an oil bath at 90 ℃ for reflux for 12 hours, then performing centrifugal washing by using deionized water and ethanol, and drying to obtain the iron-carbon-iron-carbon composite wave-absorbing material.
Example 5
The embodiment of the invention provides a preparation method of a nitrogen-doped iron-carbon composite wave-absorbing material, which comprises the following steps:
1.5g of FeNO 3 ·9H 2 Placing O and 1.5g of PVPK-30 into a beaker filled with 7.5mL of deionized water, and carrying out ultrasonic treatment in an ultrasonic cleaner until the sample is uniformly dispersed;
putting the uniformly dispersed liquid into a beaker, carrying out oil bath reaction for 10 hours at the temperature of 100 ℃, drying until the water is completely evaporated, and grinding into powder to obtain an iron-carbon composite wave-absorbing material precursor, which is named as P-Fe/NC;
weighing corresponding iron-carbon composite wave-absorbing material precursor and urea according to the mass ratio of 1:9, uniformly mixing, putting into a crucible, and adding Ar (90%)/H 2 (10%) heating to 800 ℃ at a heating rate of 7 ℃/min under a mixed atmosphere, preserving heat for 3 hours, and cooling along with a furnace to obtain a black solid product;
and adding 50mg of black product into a round-bottom flask filled with 20mL of 1MHCl, performing ultrasonic treatment at room temperature until the mixture is uniformly dispersed, heating and acid-washing in an oil bath at 90 ℃ for reflux for 12 hours, and then performing centrifugal washing and drying by using deionized water and ethanol to obtain the iron-carbon-iron-carbon composite wave-absorbing material.
Example 6
The embodiment of the invention provides a preparation method of a nitrogen-doped iron-carbon composite wave-absorbing material, which comprises the following steps:
1.5g of FeNO 3 ·9H 2 Placing O and 3g of PVPK-30 into a beaker filled with 30mL of deionized water, and carrying out ultrasonic treatment in an ultrasonic cleaner until the sample is uniformly dispersed;
putting the uniformly dispersed liquid into a beaker, carrying out oil bath reaction for 12 hours at the temperature of 80 ℃, drying until the water is completely evaporated, and grinding into powder to obtain an iron-carbon composite wave-absorbing material precursor;
weighing corresponding iron-carbon composite wave-absorbing material precursor and phenolic resin according to the mass ratio of 1:10, uniformly mixing, putting into a crucible, and adding Ar (90%)/H 2 (10%) heating to 800 ℃ at a heating rate of 7 ℃/min under a mixed atmosphere, preserving heat for 2 hours, and cooling along with a furnace to obtain a black solid product;
and adding 50mg of black product into a round-bottom flask containing 20mL of 4MHCl, performing ultrasonic treatment at room temperature until the mixture is uniformly dispersed, heating and acid-washing in an oil bath at 90 ℃ for reflux for 12 hours, and then performing centrifugal washing and drying by using deionized water and ethanol to obtain the iron-carbon-iron-carbon composite wave-absorbing material.
Example 7
The embodiment provides an application of the iron-carbon composite wave-absorbing material prepared by the method in the aspect of absorbing electromagnetic waves.
In order to research the wave-absorbing performance of the iron-carbon composite wave-absorbing material prepared by the method, the composite wave-absorbing materials obtained in example 1, example 2 and example 3 were respectively tested in this example.
The SEM and TEM of the iron-carbon composite wave-absorbing material are as follows:
as shown in figure 1, the invention successfully prepares the in-situ grown carbon nanotube Fe with the diameter of about 30nm, the wall thickness of about 6nm and the length of 300nm by utilizing the hydrogen reduction function 3 C/Fe/NC wave absorbing agent.
In FIG. 1(a), it can be observed that the in-situ grown carbon nanotubes are intertwined inside the incompletely reacted carbonized matrix, and the top end is closed. In the reaction process, because the growth speed and the orientation are different, the carbon nanotubes have no uniform length and shape, some carbon nanotubes have smaller curvature and are similar to straight lines, and some carbon nanotubes have larger curvature and are similar to circular rings. The width and the maximum length of the carbon nano-tube are respectively 20-35 nm and 350nm, and the length-diameter ratio is about 10. The transmission electron micrograph of FIG. 1(b) shows that the carbon nanotubes have a wall thickness of about 6 nm. One end of the carbon nanotube has spindle-shaped crystal particles with different colors, and the crystal size is about 12-14 nm. The comparison result shows that the Fe content corresponds to the Fe content 3 C different close-packed crystal planes, as shown in FIG. 1(C), the interplanar spacing is 0.2nm, corresponding to the cementite (112) crystal plane. Different crystal planes of cementite are observed due to the difference of the space phase of the nano particles, the crystal plane of the crystal plane (e) in figure 1 corresponds to the crystal plane of the cementite (020), and the distance is 0.196 nm. In addition, in Fe 3 The outermost layer of the C nano-particles is coated with ordered carbon layers with the thickness and the interplanar spacing of 6nm and 0.34nm respectively. It is observed from FIG. 1(b) that the tube wall is composed mainly of ordered carbon, Fe 3 The content of the carbon skeleton ordered phase of the C/Fe/NC wave absorber is obviously higher than that of the NiO/Ni/NC wave absorber. The nano metal particles can not only inhibit skin effect, but also facilitate the realization of impedance matching. Carbon nanotubes are arranged in disorderThe microstructure is rich, which is beneficial to increasing the electromagnetic wave propagation path and enhancing the loss capability.
XPS test of iron-carbon composite wave-absorbing material
As shown in fig. 2, fig. 2(a) is a wide scan spectrum of the iron-carbon composite wave-absorbing material of examples 1 to 3, and it can be seen that C, N, O and Fe elements, which correspond to C1s, N1s, O1s and Fe2p, are all present in the iron-carbon composite wave-absorbing material of examples 1 to 3 1/2 And Fe2p 3/2 A track. The iron-carbon composite wave-absorbing material of example 2 is taken as an example to perform element narrow-scan peak-splitting fitting, and the result is shown in fig. 2 (b-d). It can be seen that: the C element can be mainly divided into four peaks, which are located at 284.6, 285.5, 286.4 and 289eV, respectively, and the contributing sources are C-C/C ═ C bond, C-O bond, C-N bond and C ═ O bond, respectively. The contribution ratios of different bonds to the total peak of C1s are 53.8%, 26.46%, 13.4% and 6.32%, and it can be seen that the contribution ratio of the C-N bond is improved to a certain extent compared with the contribution ratio of the NiO/Ni/NC iron-carbon composite wave-absorbing material processed at the same temperature, which is beneficial to improving the conductivity and dielectric parameters of the wave-absorbing agent, enhancing the loss capacity and reducing the material loading. The bonding peaks of N elements of pyrrole nitrogen, pyridine nitrogen and graphite nitrogen are respectively located at 398.3, 400.1 and 400.9eV, the relative contents are respectively 22.11%, 28.13% and 49.74%, and the content of graphite nitrogen accounts for a very high ratio. Pyrrole nitrogen and pyridine nitrogen can provide lone pair electrons for a carbon conjugated system to increase polarization, while graphite nitrogen enters a graphite carbon system through hybridization, so that the resistivity is reduced, and the conduction loss is improved. The Fe2p orbital contribution is mainly derived from Fe 3 C bonding, mainly divided into Fe2p 3/2 Satellite peaks at orbital peaks 707.2eV and 710.7eV and Fe2p 1/2 The orbital peak 720.3eV and the satellite peak at 724.3 eV.
XRD and Raman tests of iron-carbon composite wave-absorbing material
Fig. 3(a) is an XRD spectrogram of the iron-carbon composite wave-absorbing material of example 1, example 2 and example 3, and fig. 3(b) is a Raman spectrogram of the iron-carbon composite wave-absorbing material of example 1, example 2 and example 3, which shows that the iron-carbon composite wave-absorbing material of examples 1 to 3 of the present invention is successfully prepared.
The analysis of the wave absorption performance of the iron-carbon composite wave-absorbing material is shown in figures 4-5:
the invention takes the iron-carbon composite wave-absorbing material of the embodiment 1-the embodiment 3 as an example, and the electromagnetic parameters are tested, and the results are shown in fig. 4. The real part of the dielectric, the imaginary part of the dielectric, the real part of the permeability, the imaginary part of the permeability, the dielectric loss tangent and the magnetic loss tangent of the iron-carbon composite wave-absorbing materials of the examples 1 to 3 can be respectively obtained from the graphs (a) to (f) in the figures 4.
The electromagnetic parameters of the obtained iron-carbon composite wave-absorbing material of the embodiments 1 to 3 are input in MATLAB software, the fitting thickness is set to be 1-5mm, and the frequency range is set to be 2-18GHz (covering Ku wave band, X wave band and C wave band). The reflectivity diagrams of the three samples are obtained through calculation simulation, and the result is shown in fig. 5, wherein fig. 5(a) is the RL diagram of the iron-carbon composite wave-absorbing material in example 1; FIG. 5(b) is a RL projection of the iron-carbon composite wave-absorbing material in example 1; FIG. 5(c) is an RL diagram of the iron-carbon composite wave-absorbing material of example 2; FIG. 5(d) is the RL projection view of the iron-carbon composite wave-absorbing material in example 2; FIG. 5(c) is an RL diagram of the iron-carbon composite wave-absorbing material of example 3; fig. 5(d) is an RL projection diagram of the iron-carbon composite wave-absorbing material in example 3.
As can be seen from fig. 5, when the matching thickness d is 2.3mm, RLmin is-53.9 dB, the Effective Absorption Bandwidth (EAB) is 3GHz (9 to 12GHz), and the X band is covered by 71.4%. When the matching thickness d is 1.55mm, EAB is 4.3GHz and the reflection loss RL < -10dB of the material indicates that 90% of the electromagnetic wave energy of the material is consumed, compared with the iron-carbon composite wave-absorbing material of the embodiment 2, the wave-absorbing material has the best wave-absorbing performance of the three, and has the electromagnetic energy consumption of nearly 99.999%, which benefits from the fact that the carbon skeleton has high ordering degree and the pore volume is increased, so that the effective dielectric constant of the wave-absorbing agent is increased, and the key effect is played on reducing the filling amount. In addition, the high anisotropy is beneficial to forming a conductive network and is beneficial to the absorption of electromagnetic waves.
Through the test analysis, the electromagnetic parameters of the iron-carbon composite wave-absorbing material in the embodiments 1 to 3 can be adjusted within a certain range through the pyrolysis temperature. By analyzing the iron-carbon composite wave-absorbing materials of the embodiments 1 to 3, the impedance matching of the embodiment 2 is good, and the wave-absorbing performance is excellent.
The iron-carbon composite wave-absorbing material is light in weight and excellent in performance, and the true density of the iron-carbon composite wave-absorbing material is only 2.18g/cm through tests 3 Typically a lightweight material.
It is to be understood that the above-described embodiments are only some of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Claims (7)

1. A preparation method of an iron-carbon composite wave-absorbing material based on nitrogen doping is characterized by comprising the following steps:
uniformly dispersing iron salt and a carbon source serving as raw materials in an aqueous solvent, and reacting at 80-100 ℃ for 4-12 hours to obtain an iron-carbon composite wave-absorbing material precursor;
uniformly mixing the obtained iron-carbon composite wave-absorbing material precursor with a nitrogen source, and then preserving heat for 1-3 hours at 700-900 ℃ in an argon-hydrogen mixed gas atmosphere to obtain a black solid crude product, wherein the crude product is subjected to post-treatment to obtain the iron-carbon composite wave-absorbing material;
the ferric salt is ferric nitrate;
the carbon source is PVP K-30;
the nitrogen source is one of dicyandiamide, hexamethylenetetramine and urea;
the mass ratio of the ferric salt to the carbon source is 1: 1-4;
the mass ratio of the iron-carbon composite wave-absorbing material precursor to the nitrogen source is 1: 9-11.
2. The preparation method of the nitrogen-doped iron-carbon composite wave-absorbing material as claimed in claim 1, wherein the ratio of the water solvent to the carbon source is 5-15 mL: 1 g.
3. The method for preparing the nitrogen-doped iron-carbon composite wave-absorbing material according to claim 1, wherein the volume ratio of argon to hydrogen in the mixed gas is 9: 1.
4. the preparation method of the nitrogen-doped iron-carbon composite wave-absorbing material according to claim 1, wherein the heating rate is 5-10 ℃/min during heat preservation in an argon-hydrogen mixed gas atmosphere.
5. The preparation method of the nitrogen-doped iron-carbon composite wave-absorbing material as claimed in claim 1, wherein the post-treatment is to uniformly disperse the crude product in 0.1-4M hydrochloric acid, and to obtain the iron-carbon composite wave-absorbing material after heating, acid washing, refluxing, centrifuging, washing and drying.
6. An iron-carbon composite wave-absorbing material prepared by the preparation method of any one of claims 1-5.
7. The iron-carbon composite wave-absorbing material of claim 6 is applied to the aspect of absorbing electromagnetic waves.
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