CN116218027A - Aerogel wave-absorbing material, electromagnetic wave absorber, preparation method and application thereof - Google Patents
Aerogel wave-absorbing material, electromagnetic wave absorber, preparation method and application thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
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- C—CHEMISTRY; METALLURGY
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Abstract
The invention belongs to the technical field of electromagnetic wave absorbing materials, and particularly relates to an aerogel wave absorbing material, an electromagnetic wave absorber, a preparation method and application thereof. The invention provides an aerogel wave-absorbing material which is LaFeO with a three-dimensional porous structure 3 Modifying nitrogen-doped reduced graphene oxide aerogel, wherein the nitrogen-doped reduced graphene oxide aerogel forms a three-dimensional framework and is LaFeO 3 The nanoparticles are distributed on a three-dimensional framework. The invention realizes LaFeO for the first time 3 The method is combined with the nitrogen-doped reduced graphene oxide aerogel, realizes the application of the aerogel in the field of electromagnetic wave absorption for the first time, and has the characteristics of high absorption strength, wide absorption frequency band, light weight and the like.
Description
Technical Field
The invention belongs to the technical field of electromagnetic wave absorbing materials, and particularly relates to an aerogel wave absorbing material, an electromagnetic wave absorber, a preparation method and application thereof.
Background
The disclosure of this background section is only intended to increase the understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art already known to those of ordinary skill in the art.
In the fifth generation of communication era, wireless communication devices are developed like bamboo shoots after rain, and the human social process is accelerated. Currently, electromagnetic waves (EMW) are widely used in various devices as a medium for wireless control and information transmission of electronic devices. Meanwhile, electromagnetic radiation also becomes a serious global environmental pollution problem, forms a serious threat to human health, and is easy to induce cancers and cardiovascular diseases. In order to solve this problem, a great deal of work has been done in the research and development of high-performance electromagnetic wave absorbing materials. In addition, in order to meet the increasing practical application demands, the ideal electromagnetic wave absorbing material has the characteristics of light weight, wide frequency band, strong absorption, good chemical stability and the like.
The conventional electromagnetic wave absorbing material is mainly a carbon material. The carbon material has the characteristics of stable property, easily available raw materials and high conductivity. The high conductivity of the carbon material is beneficial to the conductivity loss, but the high conductivity is easy to cause the unbalance of impedance matching, and is not beneficial to the electromagnetic wave absorption. In addition to carbon materials, sulfides have been studied intensively in recent years in the field of electromagnetic wave absorption, which have good impedance matching characteristics, but sulfide has poor electrical conductivity loss capability and still has limited application. Graphene sheets are receiving increasing attention due to excellent electromagnetic wave absorption properties, high thermal stability and corrosion resistance. However, it still has the problems of poor dispersibility and single loss form.
In summary, the conventional electromagnetic wave absorbing material still has many problems in terms of structure, performance, and the like, and thus, it is necessary to research a new electromagnetic wave absorbing material.
Disclosure of Invention
In order to solve the defects in the prior art, the invention aims to provide an aerogel wave-absorbing material, an electromagnetic wave absorber, a preparation method and application thereof. The invention realizes LaFeO for the first time 3 Combines with nitrogen doped reduced graphene oxide aerogel, realizes the application of the aerogel in the electromagnetic wave absorption field for the first time, and has the function of absorbingHigh strength, wide absorption frequency band, light weight, etc.
In order to achieve the above object, the present invention is realized by the following technical scheme:
in a first aspect, the present invention provides an aerogel wave-absorbing material, which is LaFeO having a three-dimensional porous structure 3 Modifying nitrogen-doped reduced graphene oxide aerogel, wherein the nitrogen-doped reduced graphene oxide aerogel forms a three-dimensional framework and is LaFeO 3 The nanoparticles are distributed on a three-dimensional framework.
In a second aspect, the present invention provides a method for preparing the aerogel wave-absorbing material according to the first aspect, which comprises the following steps:
(1) Dispersing an iron source, a lanthanum source and a polymer dispersing agent in deionized water, reacting in an oil bath, and drying and calcining a product after the reaction is finished to obtain LaFeO 3 A nanoparticle;
(2) LaFeO is prepared 3 Dispersing the nano particles in a solvent to obtain a solution A, dispersing urea and graphene oxide in the solvent to obtain a solution B, dispersing the solution A in the solution B, performing solvothermal reaction, soaking after the reaction, and drying to obtain the aerogel wave-absorbing material.
In a third aspect, the present invention provides an electromagnetic wave absorber comprising the aerogel wave absorbing material of the first aspect and a binder.
In a fourth aspect, the invention provides an application of the aerogel wave absorbing material in the first aspect and/or the electromagnetic wave absorber in the third aspect in a radio communication system, a high-frequency-resistant microwave heating device, a microwave darkroom construction and a stealth technology.
The beneficial effects obtained by one or more of the technical schemes of the invention are as follows:
(1) LaFeO prepared by the invention 3 The modified nitrogen-doped reduced graphene oxide aerogel has good impedance matching characteristics and very excellent electromagnetic wave absorption performance. First, laFeO 3 The high resistance of the absorber can avoid yield effect existing at high frequency, so that electromagnetic wave energy effectively enters the absorber and impedance is effectively optimizedMatching. LaFeO 3 The electromagnetic parameters are adjustable by the cooperative coordination and the proportion adjustment of the nitrogen doped reduced graphene oxide aerogel, the impedance matching is optimized, and conditions are created for the electromagnetic waves to enter the absorber. The three-dimensional porous structure of the aerogel expands multiple reflection and scattering of incident waves, which is beneficial to electromagnetic wave attenuation. Nanometer LaFeO 3 And the composite of the aerogel further increases the multiple scattering effect of the composite material, so that electromagnetic waves can be fully absorbed. At the same time, nitrogen doped reduced oxide aerogels provide a rich defect, producing a large number of defect polarizations and dipole polarizations. Furthermore, laFeO 3 Is a p-type high resistivity semiconductor with significantly higher resistance than graphene. Due to the large difference in conductivity between the two materials, free electrons or charges can accumulate to different extents on either side of the contact interface between two phase materials having different conductivities. Electrons are exchanged between different interfaces under the excitation of an electromagnetic field or an external alternating electric field, resulting in interface polarization and electromagnetic wave attenuation. LaFeO, on the other hand 3 While small particles have small size effects and quantum size effects, which will further improve the interfacial polarization process and multiple reflection capabilities of the composite to some extent.
(2) From LaFeO 3 The real part of the dielectric constant of the modified nitrogen doped reduced graphene oxide aerogel filled electromagnetic wave absorber at high frequency (2-18 GHz) is kept to be 3.6-11.1, the imaginary part of the dielectric constant is kept to be 1.7-5.8, the minimum value of the dielectric loss tangent exceeds 0.2, the maximum value can reach 0.8, and the modified nitrogen doped reduced graphene oxide aerogel filled electromagnetic wave absorber has good impedance matching characteristics and excellent dielectric loss capacity; at a single matching thickness in the frequency band, the maximum absorption bandwidth exceeds 6.72GHz, and the maximum absorption strength can reach-64.5 dB.
(3) From LaFeO 3 The filling rate of the electromagnetic wave absorber filled with the modified nitrogen doped reduced graphene oxide aerogel is only 15-25%, which is far lower than the filling rate (more than 50%) of electromagnetic wave absorbers filled with other carbon materials, and in addition, the aerogel can meet the requirement of light weight of the electromagnetic wave absorbing material.
(4) LaFeO prepared by the invention 3 Modified nitrogen-doped reduced graphene oxide aerogel electromagnetic wave absorptionCompared with the traditional electromagnetic wave absorbing material/absorber, laFeO is utilized 3 Has the characteristics of flame retardance.
(5) The invention initiates the synthesis of LaFeO by a simple solvothermal method 3 A method for modifying nitrogen-doped reduced graphene oxide aerogel.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
FIG. 1 shows LaFeO prepared in example 4 of the present invention 3 Modifying XRD diffraction patterns of the nitrogen-doped reduced graphene oxide aerogel and the nitrogen-doped reduced graphene oxide aerogel prepared in comparative example 1, wherein 2 theta is a diffraction angle;
FIG. 2 shows LaFeO prepared in example 4 of the present invention 3 Modifying a Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) image of the nitrogen-doped reduced graphene oxide aerogel, wherein (a) is an SEM image, (b) is an enlarged SEM image, (c) is a TEM image, (d) is a diffraction ring of a Selected Area Electron Diffraction (SAED) pattern of the TEM, and (e) is a High Resolution Transmission Electron Microscope (HRTEM) image;
FIG. 3 shows LaFeO prepared in example 4 of the present invention 3 Modifying an electromagnetic parameter test curve of the electromagnetic wave absorber filled with the nitrogen-doped reduced graphene oxide aerogel;
FIG. 4 shows LaFeO prepared in example 4 of the present invention 3 Modifying a Cole-Cole curve of the nitrogen-doped reduced graphene oxide aerogel-filled electromagnetic wave absorber;
FIG. 5 shows LaFeO prepared in example 4 of the present invention 3 A three-dimensional schematic diagram of the absorption performance of the electromagnetic wave absorber filled with the modified nitrogen-doped reduced graphene oxide aerogel;
fig. 6 is a three-dimensional schematic diagram of electromagnetic parameters and absorption performance of the nitrogen-doped reduced graphene oxide aerogel-filled electromagnetic wave absorber of comparative example 1 of the present invention.
Detailed Description
First exemplary embodiment of the inventionAn aerogel wave-absorbing material which is LaFeO with a three-dimensional porous structure 3 Modifying nitrogen-doped reduced graphene oxide aerogel, wherein the nitrogen-doped reduced graphene oxide aerogel forms a three-dimensional framework and is LaFeO 3 The nanoparticles are distributed on a three-dimensional framework.
LaFeO 3 The high resistance of the electromagnetic wave absorber can avoid yield effect existing at high frequency, so that electromagnetic wave energy effectively enters the electromagnetic wave absorber, and impedance matching is effectively optimized. LaFeO 3 The electromagnetic parameters are adjustable by the cooperative coordination and the proportion adjustment of the nitrogen doped reduced graphene oxide aerogel, the impedance matching is optimized, and conditions are created for the electromagnetic waves to enter the absorber. The three-dimensional porous structure of the aerogel expands multiple reflection and scattering of incident waves, which is beneficial to electromagnetic wave attenuation. Nanometer LaFeO 3 And the composite of the aerogel further increases the multiple scattering effect of the composite material, so that electromagnetic waves can be fully absorbed. At the same time, nitrogen doped reduced oxide aerogels provide a rich defect, producing a large number of defect polarizations and dipole polarizations. Furthermore, laFeO 3 Is a p-type high resistivity semiconductor with significantly higher resistance than graphene. Due to the large difference in conductivity between the two materials, free electrons or charges can accumulate to different extents on either side of the contact interface between two phase materials having different conductivities. Electrons are exchanged between different interfaces under the excitation of an electromagnetic field or an external alternating electric field, resulting in interface polarization and electromagnetic wave attenuation.
In one or more embodiments of this embodiment, the LaFeO 3 The nano particles are orthorhombic perovskite; the LaFeO 3 The particle size of the nano particles is less than 100nm. LaFeO 3 While small particles have small size effects and quantum size effects, which will further improve the interfacial polarization process and multiple reflection capabilities of the composite to some extent.
In one or more embodiments of this embodiment, the three-dimensional framework has a pore size of 10-20 μm.
According to a second exemplary embodiment of the present invention, a method for preparing an aerogel wave-absorbing material according to the first exemplary embodiment, includes the following steps:
(1) Dispersing an iron source, a lanthanum source and a polymer dispersing agent in deionized water, reacting in an oil bath, and drying and calcining a product after the reaction is finished to obtain LaFeO 3 A nanoparticle;
(2) LaFeO is prepared 3 Dispersing the nano particles in a solvent to obtain a solution A, dispersing urea and graphene oxide in the solvent to obtain a solution B, dispersing the solution A in the solution B, performing solvothermal reaction, soaking after the reaction, and drying to obtain the aerogel wave-absorbing material.
The invention utilizes urea as a reducing agent and a nitrogen source to regulate and control the reaction environment, and is doped with LaFeO 3 And structural defects are generated on the surface of the reduced graphene oxide. Such material structure design is beneficial to improving the defect polarization and interface polarization loss capability of the material.
In one or more examples of this embodiment, the lanthanum source is one or a mixture of two of lanthanum nitrate hexahydrate and lanthanum chloride.
In one or more examples of this embodiment, the iron source is a mixture of any one or more of ferric nitrate nonahydrate, ferric chloride, and ferric acetylacetonate.
In one or more embodiments of this embodiment, the polymeric dispersant is one of polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, polyethylene glycol.
In one or more embodiments of this embodiment, the temperature of the oil bath in step (1) is 75-85 ℃ and the time of the reaction under the oil bath is 30-60min.
In one or more embodiments of this embodiment, the drying in step (1) is at a temperature of 75-85 ℃.
In one or more examples of this embodiment, the calcination in step (1) is specifically a calcination at 500 ℃ for 30min and a calcination at 900 ℃ for 3h.
In one or more embodiments of this embodiment, the solvent of solution a is a mixture of one or more of ethylene glycol, ethanol, and deionized water.
In one or more embodiments of this embodiment, the solvent of solution B is one or a mixture of two of ethanol or water.
In one or more examples of this embodiment, the concentration of graphene oxide in solution B is 3-10mg/mL and the mass ratio of urea to graphene oxide is 0.5-2.5:1.
In one or more examples of this embodiment, graphene oxide is combined with LaFeO 3 The mass ratio of the nano particles is 1.25:10-1.
In one or more embodiments of this embodiment, the solvothermal reaction is at a temperature of 160-220 ℃ for a period of 8-16 hours.
In one or more embodiments of this embodiment, the soaking solvent is ethanol or deionized water for a soaking time of 12-24 hours.
In one or more embodiments of this embodiment, the drying is freeze-drying or vacuum-drying, the freeze-drying is performed for a period of 24-48 hours, the vacuum-drying is performed at a temperature of 50-80 ℃, and the vacuum-drying is performed for a period of 16-24 hours.
In a third exemplary embodiment of the present invention, an electromagnetic wave absorber comprises the aerogel wave absorbing material according to the first exemplary embodiment and a binder.
In one or more embodiments of this embodiment, the adhesive is one of paraffin wax, epoxy resin, and polyvinylidene fluoride.
In one or more embodiments of this embodiment, the mass ratio of the adhesive to the aerogel wave-absorbing material is 15-17:1.
In one or more embodiments of this embodiment, the electromagnetic wave absorber has a fill level of aerogel wave absorbing material of between 15% and 25%.
In a fourth exemplary embodiment of the present invention, the aerogel wave absorbing material according to the first exemplary embodiment and/or the electromagnetic wave absorber according to the third exemplary embodiment are used in a radio communication system, a high-frequency-proof, microwave heating device, a microwave camera, and a stealth technology.
In order to enable those skilled in the art to more clearly understand the technical scheme of the present invention, the technical scheme of the present invention will be described in detail below with reference to specific examples and comparative examples.
Example 1
(1) 2mmol of iron acetylacetonate, 0.012mol of polyvinyl alcohol and 2mmol of lanthanum nitrate hexahydrate were dispersed in 30mL of deionized water and stirred to dissolve.
(2) And (3) carrying out oil bath on the solution obtained in the step (1) at 80 ℃ for 40min, and drying the obtained mixture at 80 ℃. Presintering at 500deg.C for 30min to remove organic components, and calcining at 900deg.C for 3 hr to obtain LaFeO 3 And (3) nanoparticles.
(3) 15mg LaFeO is taken 3 The nanoparticles were dispersed in 1mL of ethylene glycol and sonicated for 30min to give solution A. 50mg of graphene oxide and 70mg of urea were dissolved in 5ml of deionized water and sonicated for 1h to give solution B.
(4) The solution A is dispersed in the solution B, ultrasonic treatment is carried out for 1h, the obtained mixture is transferred into a steel reaction kettle with a 20mL polytetrafluoroethylene lining, and the mixture is heated for 13h at 160 ℃ to form hydrogel. Soaking the hydrogel in ethanol for 12h to remove impurities. Finally, vacuum drying at 80 ℃ for 24 hours to obtain LaFeO 3 Modifying the nitrogen-doped reduced graphene oxide aerogel.
(5) Melting solid paraffin at a temperature above 80deg.C, and mixing with LaFeO at a mass ratio of paraffin to aerogel of 4:1 3 And (3) modifying the nitrogen-doped reduced graphene oxide aerogel, rapidly and uniformly stirring, cooling to room temperature, and pressing to obtain the electromagnetic wave absorber.
Example 2
(1) 2mmol of ferric nitrate nonahydrate, 0.012mol of polyvinyl alcohol and 2mmol of lanthanum chloride were dispersed in 30mL of deionized water and stirred to dissolve.
(2) And (3) carrying out oil bath on the solution obtained in the step (1) at 80 ℃ for 40min, and drying the obtained mixture at 80 ℃. Presintering at 500deg.C for 30min to remove organic components, and calcining at 900deg.C for 3 hr to obtain LaFeO 3 And (3) nanoparticles.
(3) Taking 5mg LaFeO 3 The nanoparticles were dispersed in 1mL of ethanol and sonicated for 30min to give solution a. 50mg of graphene oxide and 80mg of urea are dissolved in 5ml of ethanol and sonicated for 1h to obtain solution B.
(4) The solution A is dispersed in the solution B, ultrasonic treatment is carried out for 1h, the obtained mixture is transferred into a steel reaction kettle with a 20mL polytetrafluoroethylene lining, and the mixture is heated for 10h at 180 ℃ to form hydrogel. Soaking the hydrogel in deionized water for 12h to remove impurities. Finally, freeze-drying for 48h to obtain LaFeO 3 Modifying the nitrogen-doped reduced graphene oxide aerogel.
(5) Melting solid paraffin at a temperature above 80deg.C, and mixing with LaFeO at a mass ratio of paraffin to aerogel of 4:1 3 And (3) modifying the nitrogen-doped reduced graphene oxide aerogel, rapidly and uniformly stirring, cooling to room temperature, and pressing to obtain the electromagnetic wave absorber.
Example 3
(1) 2mmol of ferric chloride, 0.012mol of polyvinyl alcohol and 2mmol of lanthanum nitrate hexahydrate were dispersed in 30mL of deionized water and stirred to dissolve.
(2) And (3) carrying out oil bath on the solution obtained in the step (1) at 80 ℃ for 40min, and drying the obtained mixture at 80 ℃. Presintering at 500deg.C for 30min to remove organic components, and calcining at 900deg.C for 3 hr to obtain LaFeO 3 And (3) nanoparticles.
(3) 10mg of LaFeO is taken 3 The nanoparticles were dispersed in 1mL of ethylene glycol and sonicated for 30min to give solution A. 30mg of graphene oxide and 45mg of urea are dissolved in 5ml of ethanol and sonicated for 1h to obtain solution B.
(4) The solution A is dispersed in the solution B, ultrasonic treatment is carried out for 1h, the obtained mixture is transferred into a steel reaction kettle with a 20mL polytetrafluoroethylene lining, and the mixture is heated for 10h at 190 ℃ to form hydrogel. Soaking the hydrogel in ethanol for 24h to remove impurities. Finally, vacuum drying at 80 ℃ for 20 hours to obtain LaFeO 3 Modifying the nitrogen-doped reduced graphene oxide aerogel.
(5) Melting solid paraffin at a temperature above 80deg.C, and mixing with LaFeO at a mass ratio of paraffin to aerogel of 4:1 3 And (3) modifying the nitrogen-doped reduced graphene oxide aerogel, rapidly and uniformly stirring, cooling to room temperature, and pressing to obtain the electromagnetic wave absorber.
Example 4
(1) 2mmol of ferric nitrate nonahydrate, 0.012mol of polyvinyl alcohol and 2mmol of lanthanum nitrate hexahydrate were dispersed in 30mL of deionized water and stirred to dissolve.
(2) And (3) carrying out oil bath on the solution obtained in the step (1) at 80 ℃ for 40min, and drying the obtained mixture at 80 ℃. Presintering at 500deg.C for 30min to remove organic components, and calcining at 900deg.C for 3 hr to obtain LaFeO 3 And (3) nanoparticles.
(3) 10mg of LaFeO is taken 3 The nanoparticles were dispersed in 1mL of ethylene glycol and sonicated for 30min to give solution A. 50mg of graphene oxide and 75mg of urea were dissolved in 5ml of deionized water and sonicated for 1h to give solution B.
(4) The solution A is dispersed in the solution B, ultrasonic treatment is carried out for 1h, the obtained mixture is transferred into a steel reaction kettle with a 20mL polytetrafluoroethylene lining, and the mixture is heated for 12h at 180 ℃ to form hydrogel. Soaking the hydrogel in ethanol for 24h to remove impurities. Finally, freeze-drying for 24 hours to obtain LaFeO 3 Modifying the nitrogen-doped reduced graphene oxide aerogel.
(5) Melting solid paraffin at a temperature above 80deg.C, and mixing with LaFeO at a mass ratio of paraffin to aerogel of 4:1 3 And (3) modifying the nitrogen-doped reduced graphene oxide aerogel, rapidly and uniformly stirring, cooling to room temperature, and pressing to obtain the electromagnetic wave absorber.
Comparative example 1
(1) 50mg of graphene oxide and 75mg of urea were dissolved in 5ml of deionized water and sonicated for 1h to obtain a solution.
(2) The resulting solution was sonicated for 1h and transferred to a 20mL polytetrafluoroethylene-lined steel reactor and heated at 190℃for 10h to form a hydrogel. Soaking the hydrogel in ethanol solution for 24h to remove impurities. Finally, freeze-drying for 24 hours to obtain the aerogel.
(3) Melting solid paraffin at a temperature of more than 80 ℃, mixing the solid paraffin into the product in the step (2) according to the mass ratio of paraffin to aerogel of 4:1, rapidly and uniformly stirring, cooling to room temperature, and pressing to obtain the electromagnetic wave absorber.
Performance testing and evaluation:
(1) LaFeO prepared in example 4 3 XRD testing was performed on the modified nitrogen-doped reduced graphene oxide aerogel and the nitrogen-doped reduced graphene oxide aerogel described in comparative example 1, with the results shown in FIG. 1It can be seen that both show diffraction peaks at around 25 deg., corresponding to the (002) crystal plane. Here, a typical peak of graphene oxide cannot be observed, which means that graphene oxide is successfully reduced to reduced graphene oxide. Diffraction peaks at 22.6 °, 32.2 °, 39.7 °, 46.2 °, 52.0 °, 57.4 °, 67.3 °, 67.4 °, and 76.5 ° are assigned to LaFeO, respectively 3 (110), (112), (202), (220), (222), (312), (224), (400) and (332). LaFeO 3 Diffraction peaks shown by the modified nitrogen-doped reduced graphene oxide aerogel material can be successfully classified into LaFeO 3 Phase, indicating LaFeO 3 Successful doping does not occur phase change.
(2) LaFeO prepared in example 4 3 Modified nitrogen doped reduced graphene oxide aerogels were observed under SEM and TEM. As shown in FIG. 2, the SEM image of FIG. 2 (a) shows LaFeO 3 The modified nitrogen-doped reduced graphene oxide aerogel has a porous three-dimensional network, and the enlarged view of fig. 2 (b) shows that the modified nitrogen-doped reduced graphene oxide aerogel has wrinkles and a three-dimensional continuous structure, laFeO 3 The nanoparticles are distributed on graphene nanoplatelets. TEM of FIG. 2 (c) shows LaFeO 3 The particle size of the nano particles is smaller than 100nm, and the size distribution is very narrow. Because of their small size, these nanoparticles are easily agglomerated together. Diffraction rings of the Selected Area Electron Diffraction (SAED) pattern of TEM (fig. 2 (d)) indicate the crystalline nature of nitrogen doped reduced graphene oxide. Then, the SAED pattern diffraction ring corresponds to LaFeO 3 (112) Crystal face, nitrogen doped reduced graphene oxide (101) crystal face and LaFeO 3 (220) Crystal face, nitrogen doped reduced graphene oxide (110) crystal face, which is consistent with XRD results, shows the polycrystalline nature of the composite material. In addition, FIG. 2 (e) shows LaFeO 3 Modification of HRTEM images of nitrogen doped reduced graphene oxide aerogels, wherein 0.196nm corresponds to LaFeO 3 (220) Interplanar spacing of the crystal planes, 0.297nm corresponds to LaFeO 3 (112) Interplanar spacing of crystal planes.
(3) LaFeO prepared in example 4 3 Electromagnetic parameters of the absorber, which are measured by an electromagnetic wave vector network analyzer for the electromagnetic wave absorber filled with the modified nitrogen-doped reduced graphene oxide aerogel, are shown in fig. 3, and it can be seen that the absorber has moderate propertiesThe real part and the imaginary part of the dielectric constant can greatly improve the loss and attenuation capability of the absorber to electromagnetic waves.
(4) Analysis of the dielectric constants measured for the electromagnetic wave absorber of example 4 gave a Cole-Cole curve as shown in fig. 4, and it can be seen that the Cole-Cole curve of the absorber exhibited a plurality of significant semicircles, indicating that there was a polarization relaxation phenomenon in the absorber, which was advantageous for polarization loss.
(5) As shown in fig. 5, which is a three-dimensional schematic diagram of the absorption performance calculated and plotted according to the electromagnetic parameters measured in example 4, it can be seen that the absorber exhibits very good absorption performance, the maximum absorption intensity can reach-64.5 dB, and the maximum absorption bandwidth at a single matching thickness in this band exceeds 6.72GHz.
(6) For the electromagnetic wave absorber filled with the nitrogen-doped reduced graphene oxide aerogel prepared in comparative example 1, electromagnetic parameters of the absorber are measured by an electromagnetic wave vector network analyzer, and a three-dimensional schematic diagram of absorption performance is calculated and drawn, as shown in fig. 6, it can be seen that the dielectric constant of the absorber is high in imaginary part, which is not beneficial to optimization of impedance matching. The three-dimensional schematic diagram of its absorption properties demonstrates that its electromagnetic wave absorption capacity is very weak.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. An aerogel wave-absorbing material is characterized in that the aerogel wave-absorbing material is LaFeO with a three-dimensional porous structure 3 Modifying nitrogen-doped reduced graphene oxide aerogel, wherein the nitrogen-doped reduced graphene oxide aerogel forms a three-dimensional framework and is LaFeO 3 The nanoparticles are distributed on a three-dimensional framework.
2. The aerogel wave absorbing material of claim 1, wherein the LaFeO 3 The nano particles are orthorhombic perovskite; the LaFeO 3 The particle size of the nano particles is less than 100nm.
3. The aerogel wave absorbing material of claim 1, wherein the three-dimensional framework has a pore size of 10-20 μιη.
4. A method of preparing the aerogel wave absorbing material of any one of claims 1-3, comprising the steps of:
(1) Dispersing an iron source, a lanthanum source and a polymer dispersing agent in deionized water, reacting in an oil bath, and drying and calcining a product after the reaction is finished to obtain LaFeO 3 A nanoparticle;
(2) LaFeO is prepared 3 Dispersing the nano particles in a solvent to obtain a solution A, dispersing urea and graphene oxide in the solvent to obtain a solution B, dispersing the solution A in the solution B, performing solvothermal reaction, soaking after the reaction, and drying to obtain the aerogel wave-absorbing material.
5. The method of claim 4, wherein the lanthanum source is one or a mixture of lanthanum nitrate hexahydrate and lanthanum chloride;
the iron source is any one or a mixture of a plurality of ferric nitrate nonahydrate, ferric chloride and ferric acetylacetonate;
the polymer dispersing agent is one of polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone and polyethylene glycol;
the temperature of the oil bath in the step (1) is 75-85 ℃, and the reaction time under the oil bath is 30-60min;
the drying temperature in the step (1) is 75-85 ℃;
the calcination in the step (1) is specifically pre-calcination at 500 ℃ for 30min and calcination at 900 ℃ for 3h.
6. The method according to claim 4, wherein the solvent of the solution A is one or more of glycol, ethanol and deionized water;
the solvent of the solution B is one or two of ethanol and water;
the concentration of the graphene oxide in the solution B is 3-10mg/mL, and the mass ratio of urea to the graphene oxide is 0.5-2.5:1;
graphene oxide and LaFeO 3 The mass ratio of the nano particles is 1.25:10-1.
7. The process according to claim 4, wherein the solvothermal reaction is carried out at a temperature of 160 to 220℃for a period of 8 to 16 hours;
the soaking solvent is ethanol or deionized water, and the soaking time is 12-24 hours;
the drying is freeze drying or vacuum drying, the time of freeze drying is 24-48h, the temperature of vacuum drying is 50-80 ℃, and the time of vacuum drying is 16-24h.
8. An electromagnetic wave absorber comprising the aerogel wave absorbing material of any one of claims 1 to 3 and a binder.
9. The electromagnetic wave absorber according to claim 8, wherein the adhesive is one of paraffin wax, epoxy resin and polyvinylidene fluoride;
the mass ratio of the adhesive to the aerogel wave-absorbing material is 15-17:1;
the filling rate of the aerogel wave-absorbing material in the electromagnetic wave absorber is 15% -25%.
10. Use of the aerogel wave absorbing material according to any of claims 1 to 3 and/or the electromagnetic wave absorber according to any of claims 8 to 9 in radio communication systems, high frequency protection, microwave heating devices, construction of microwave darkroom, stealth technology.
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