MnFe2O4 / GO wave-absorbing aerogel with directional aperture structure and preparation method thereof

Abstract

The application discloses a MnFe2O4 / GO wave-absorbing aerogel with a directional aperture structure and a preparation method thereof, belongs to the technical field of wave-absorbing material preparation, and is characterized in that manganese ferrite (MnFe2O4) magnetic particles are uniformly loaded on the surface of graphene to obtain a graphene aerogel with a three-dimensional loose porous structure and magnetic particle assembly; the MnFe2O4 is prepared by using a low-temperature co-precipitation method, and the MnFe2O4 / GO wave-absorbing aerogel is prepared by combining directional freezing and heat treatment, and the method is mild and simple. The application improves the impedance mismatch problem of the graphene material, enhances the magnetic loss of the material, and obtains a novel porous aerogel wave-absorbing material which has both dielectric loss and magnetic loss by introducing the manganese ferrite.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of wave-absorbing material preparation, in particular to MnFe2O4 / GO wave-absorbing aerogel with a directional pore structure and a preparation method thereof. BACKGROUND

[0002] With the development of 5G communication technology, aerospace industry and anti-reconnaissance technology in the military field, people's attention on electromagnetic wave-absorbing materials is increasing, and the requirements for microwave absorbing materials are increasing. Developing new electromagnetic wave-absorbing materials with light weight, thin thickness, wide absorption frequency band and strong absorption performance has become an inevitable trend. Graphene is widely studied as an ideal candidate for realizing efficient microwave absorption due to its light weight, unique two-dimensional structure and controllable dielectric properties. However, pure graphene material is prone to cause impedance mismatch and single dissipation mechanism due to its high electrical conductivity, and its performance in absorbing electromagnetic waves is not satisfactory when used as an electromagnetic wave-absorbing material. It is difficult to meet the comprehensive requirements of "thin, light, wide and strong" for new generation wave-absorbing materials, which greatly hinders its practical application in the field of electromagnetic wave absorption.

[0003] Spinel manganese ferrite (MnFe2O4) is an important ferrite. It has been used in the field of wave-absorbing technology due to its simple synthesis, low cost, excellent chemical stability, outstanding magnetic loss characteristics and moderate saturation magnetization. It is known that multi-component design can optimize the electromagnetic attenuation characteristics of composite materials. Compared with solid wave-absorbing materials, aerogel materials have more uniform pore distribution and lower density, and have smaller effective dielectric constant, so they can realize good matching of incident electromagnetic waves in a wide frequency range. However, the traditional bulk material has high density, which is difficult to meet the requirement of light weight.

[0004] In summary, there is an urgent need in the field to develop a new wave-absorbing material with light weight, strong wave-absorbing ability and wide wave-absorbing frequency band and a directional pore structure. It is attempted to composite graphene with dielectric properties and magnetic manganese ferrite through the synergistic effect between dielectric loss and magnetic loss and the multiple interface polarization between graphene and MnFe2O4, and to design and prepare MnFe2O4 / GO aerogel with a directional pore structure, so as to enhance the microwave absorption effect and obtain a new wave-absorbing material with good microwave absorption performance. SUMMARY

[0005] The purpose of the present application is to provide a MnFe2O4 / GO wave-absorbing aerogel with a directional pore structure and a preparation method thereof. The graphene is composited with manganese ferrite, and the aerogel with a directional pore structure is obtained under certain conditions. The aerogel has the advantages of light weight, wide wave-absorbing frequency band, strong wave-absorbing ability, high porosity and simple preparation method.

[0006] To achieve the above object, the application provides a preparation method of MnFe2O4 / GO wave-absorbing aerogel with a directional pore structure, which specifically comprises the following preparation steps:

[0007] 1) A proper amount of FeCl3·6H2O and MnCl2·4H2O are weighed and dissolved in deionized water respectively to obtain FeCl3 solution and MnCl2 solution; a proper amount of polyethylene glycol is weighed and dissolved in deionized water to obtain solution A;

[0008] 2) The FeCl3 solution and the MnCl2 solution obtained in step 1) are mixed uniformly in a three-necked flask with a small amount of dilute sulfuric acid;

[0009] 3) The three-necked flask is placed in a water bath, solution A is added, stirring is carried out at a proper temperature, sodium hydroxide solution is added to adjust the pH, and then sufficient reaction is carried out to obtain solution B;

[0010] 4) The solution B obtained in step 3) is repeatedly washed with deionized water until the pH is neutral to obtain solution C;

[0011] 5) A proper amount of graphene oxide is weighed, dissolved in deionized water, ultrasonically treated, and then fully stirred to obtain a brownish yellow graphene oxide solution;

[0012] 6) The solution C obtained in step 4) and the graphene oxide solution obtained in step 5) are mixed in a certain volume ratio, stirring is carried out at room temperature for 8-18 h to obtain solution D;

[0013] 7) The solution D obtained in step 6) is subjected to directional freezing and drying treatment;

[0014] 8) The MnFe2O4 / GO aerogel obtained in step 7) is placed in a tube furnace, and heat treatment is carried out under the protection of an atmosphere to obtain MnFe2O4 / GO aerogel.

[0015] Preferably, in the above preparation method of MnFe2O4 / GO wave-absorbing aerogel with a directional pore structure, the molar ratio of FeCl3·6H2O to deionized water in step 1) is 1-6:9-20, the molar ratio of MnCl2·4H2O to deionized water is 1-5:18-45, and the mass ratio of polyethylene glycol to deionized water is 3-8:100.

[0016] Preferably, in the above preparation method of MnFe2O4 / GO wave-absorbing aerogel with a directional pore structure, the temperature for reaction in step 3) is 60-100℃, the stirring time is 10-60 min, the reaction time is 1-5 h, and the pH is greater than 11.

[0017] Preferably, in the preparation method of the MnFe2O4 / GO wave-absorbing aerogel with a directional pore structure, the volume of the solution C in step 4) is 100-400 ml.

[0018] Preferably, in the preparation method of the MnFe2O4 / GO wave-absorbing aerogel with a directional pore structure, the mass ratio of graphene oxide and deionized water in step 5) is 1-10:100.

[0019] Preferably, in the preparation method of the MnFe2O4 / GO wave-absorbing aerogel with a directional pore structure, the mass ratio of the manganese ferrite in the solution C and the graphene in the graphene oxide solution in step 6) is 1-8:4-12.

[0020] Preferably, in the preparation method of the MnFe2O4 / GO wave-absorbing aerogel with a directional pore structure, the freezing temperature in step 7) is-20--90℃, the freezing time is 12-24 h, and the drying time is 12-72 h.

[0021] Preferably, in the preparation method of the MnFe2O4 / GO wave-absorbing aerogel with a directional pore structure, the protective atmosphere in step 8) is one of nitrogen and argon, the heating rate of heat treatment is 1-15℃ / min, the holding temperature is 200-700℃, and the holding time is 1-6 h.

[0022] The MnFe2O4 / GO wave-absorbing aerogel with a directional pore structure obtained by the above preparation method has the magnetic particles MnFe2O4 uniformly loaded on the surface of graphene, and the obtained graphene aerogel has a three-dimensional loose porous structure.

[0023] Therefore, the MnFe2O4 / GO wave-absorbing aerogel with a directional pore structure and the preparation method thereof have the advantages that the obtained aerogel includes graphene with a directional honeycomb pore structure connected to each other, the wrinkles on the surface of the uppermost graphene are clearly visible, and the microspherical manganese ferrite is distributed on the surface of the layered graphene. The aerogel has the characteristics of extremely light weight, can be easily supported by grass, and realizes the effect of enhancing microwave absorption through the synergistic effect between dielectric loss and magnetic loss and the multiple interface polarization between graphene and MnFe2O4.

[0024] The technical solutions of the present application are described in further detail below by means of the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The directional freezing process diagram of the MnFe2O4 / GO aerogel of Example 1.

[0026] Figure 2 The wave absorption performance diagram of the MnFe2O4 / GO aerogel sample of Example 1.

[0027] Figure 3 The SEM diagram of the MnFe2O4 / GO wave absorption aerogel sample of Example 1.

[0028] Figure 4 The wave absorption performance diagram of the MnFe2O4 / GO aerogel sample of Example 2.

[0029] Figure 5 The SEM diagram of the MnFe2O4 / GO wave absorption aerogel sample of Example 2.

[0030] Figure 6 The wave absorption performance diagram of the MnFe2O4 / GO aerogel sample of Example 3.

[0031] Figure 7 The SEM diagram of the MnFe2O4 / GO wave absorption aerogel sample of Example 3. DETAILED DESCRIPTION

[0032] In order to better understand the above technical solutions, the above technical solutions will be described in detail below in combination with the description of the drawings and specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0033] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. "Plural" generally includes at least two.

[0034] It should also be noted that the terms "comprising", "including", or any other variant thereof are intended to cover non-exclusive inclusion, so that the product or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such product or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of additional identical elements in the product or device including the element.

[0035] The application provides a preparation method of MnFe2O4 / GO wave-absorbing aerogel with a directional aperture structure, wherein magnetic particles MnFe2O4 are uniformly loaded on the surface of graphene, and a three-dimensional loose porous structure of the magnetic particle assembled graphene aerogel is obtained.

[0036] Specifically, the following preparation steps are included:

[0037] 1) A proper amount of FeCl3·6H2O and MnCl2·4H2O are weighed and dissolved in deionized water respectively to obtain FeCl3 solution and MnCl2 solution; a proper amount of polyethylene glycol is weighed and dissolved in deionized water to obtain solution A;

[0038] 2) The FeCl3 solution and the MnCl2 solution obtained in step 1) are mixed uniformly in a three-necked flask with a small amount of dilute sulfuric acid;

[0039] 3) The three-necked flask is placed in a water bath, solution A is added, stirring is carried out at a proper temperature, sodium hydroxide solution is added to adjust the pH, and then sufficient reaction is carried out to obtain solution B;

[0040] 4) The solution B obtained in step 3) is repeatedly washed with deionized water until the pH is neutral to obtain solution C;

[0041] 5) A proper amount of graphene oxide is weighed, dissolved in deionized water, ultrasonically treated, and then fully stirred to obtain a brownish yellow graphene oxide solution;

[0042] 6) The solution C obtained in step 4) and the graphene oxide solution obtained in step 5) are mixed in a certain volume ratio, stirring is carried out at room temperature for 8-18 hours to obtain solution D;

[0043] 7) The solution D obtained in step 6) is subjected to directional freezing and drying treatment;

[0044] 8) The MnFe2O4 / GO aerogel obtained in step 7) is placed in a tube furnace, and heat treatment is carried out under the protection of an atmosphere to obtain MnFe2O4 / GO aerogel.

[0045] To further optimize the above technical solution, the molar ratio of FeCl3·6H2O to deionized water in step 1) is 1-6:9-20, the molar ratio of MnCl2·4H2O to deionized water is 1-5:18-45, and the mass ratio of polyethylene glycol to deionized water is 3-8:100.

[0046] To further optimize the above technical solution, the temperature for reaction in step 3) is 60-100℃, the stirring time is 10-60min, the reaction time is 1-5h, and the pH is greater than 11.

[0047] To further optimize the above technical solution, the volume of solution C in step 4) is 100-400 ml.

[0048] To further optimize the above technical solution, the mass ratio of graphene oxide and deionized water in step 5) is 1-10:100.

[0049] To further optimize the above technical solution, the mass ratio of manganese ferrite in solution C and graphene in graphene oxide solution in step 6) is 1-8:4-12.

[0050] To further optimize the above technical solution, the freezing temperature in step 7) is-20 to-90℃, the time is 12-24h, and the drying time is 12-72h.

[0051] To further optimize the above technical solution, the protective atmosphere in step 8) is one of nitrogen and argon, the heating rate of heat treatment is 1-15℃ / min, the holding temperature is 200-700℃, and the holding time is 1-6h.

[0052] The MnFe2O4 / GO wave-absorbing aerogel with a directional pore structure is obtained by the preparation method, the magnetic particles MnFe2O4 are uniformly loaded on the surface of graphene, and the obtained graphene aerogel has a three-dimensional loose porous structure.

[0053] In order to more clearly and specifically introduce the MnFe2O4 / GO wave-absorbing aerogel with a directional pore structure and the preparation method thereof provided by the embodiments of the present application, the following will be described in combination with specific embodiments.

[0054] Embodiment 1

[0055] 1) 3.957g of FeCl3·6H2O was weighed and dissolved in 50ml of deionized water, 3.957g of MnCl2·4H2O was weighed and dissolved in 25ml of deionized water. 5g of polyethylene glycol was dissolved in 50ml of deionized water to obtain solution A.

[0056] 2) The FeCl3 solution and the MnCl2 solution obtained in step 1) were mixed uniformly in a three-necked flask with a small amount of dilute sulfuric acid.

[0057] 3) The three-necked flask was placed in a water bath, solution A was added, and stirred for a period of time at 60℃. After the pH was adjusted to 11 by adding sodium hydroxide solution, it was reacted for 2h to obtain solution B.

[0058] 4) The solution B obtained in step 3) was repeatedly washed with deionized water until the pH was neutral to obtain solution C.

[0059] 5) Take 2 g of graphene oxide, dissolve in 200 ml of deionized water, ultrasonic treatment, then stir well, get brown yellow graphene oxide solution.

[0060] 6) The solution C obtained in step 4) is mixed with the graphene solution obtained in step 5) in a volume ratio of 11:100, stirred at room temperature for 8-18 h to obtain solution D.

[0061] 7) The solution D obtained in step 6) is frozen at-20 to-90℃ for 12-24 h, and dried for 12-72 h.

[0062] 8) The MnFe2O4 / GO aerogel obtained in step 7) is placed in a tube furnace and heat treated at 300℃ for 2 h under nitrogen atmosphere to obtain MnFe2O4 / GO aerogel.

[0063] The obtained MnFe2O4 / GO aerogel is doped with paraffin to prepare a coaxial ring sample (the inner diameter of the coaxial ring sample is 3 mm, and the outer diameter is 7 mm), and the electromagnetic parameters of the sample are measured by a vector network analyzer, and then the wave absorption performance of the material is calculated by CST STUDIO SUITE software. The wave absorption performance of the obtained MnFe2O4 / GO wave absorption aerogel is shown in Figure 2 As can be seen from the figure, when the thickness of the material is 2.9 mm, the minimum reflection loss at 9.46 GHz reaches-29.24 dB, and the widest effective absorption band reaches 4.72 GHz at this time, which has effective wave absorption performance. The SEM image of the MnFe2O4 / GO wave absorption aerogel sample is shown in Figure 3 .

[0064] Example 2

[0065] 1) Take 3.957 g of FeCl3·6H2O and dissolve it in 50 ml of deionized water, take 3.957 g of MnCl2·4H2O and dissolve it in 25 ml of deionized water. Take 5 g of polyethylene glycol and dissolve it in 50 ml of deionized water to obtain solution A.

[0066] 2) Mix the FeCl3 solution and MnCl2 solution obtained in step 1) in a three-necked flask with a small amount of dilute sulfuric acid.

[0067] 3) Put the three-necked flask into a water bath, add solution A, stir for a period of time at 60℃, add sodium hydroxide solution to adjust the pH to 11, and then react for 2 h to obtain solution B.

[0068] 4) Wash the solution B obtained in step 3) with deionized water until the pH is neutral to obtain solution C.

[0069] 5) Take 2 g of graphene oxide, dissolve in 200 ml of deionized water, ultrasonic treatment, then fully stirred for 8-18 h, to obtain a brownish yellow graphene oxide solution.

[0070] 6) The solution C obtained in step 4) is mixed with the graphene solution obtained in step 5) in a volume ratio of 11:50, stirred at room temperature for 12 h to obtain solution D.

[0071] 7) The solution D obtained in step 6) is frozen at -20 to -90 ℃ for 12-24 h, and dried for 12-72 h.

[0072] 8) The MnFe2O4 / GO aerogel obtained in step 7) is placed in a tube furnace and heat treated at 300 ℃ for 2 h under nitrogen atmosphere to obtain MnFe2O4 / GO aerogel.

[0073] The obtained MnFe2O4 / GO aerogel is doped with paraffin to prepare a coaxial ring sample (the inner diameter of the coaxial ring sample is 3 mm, and the outer diameter is 7 mm), and the electromagnetic parameters of the sample are measured by a vector network analyzer, and then the wave absorption performance of the material is calculated by CST STUDIO SUITE software. The wave absorption performance of the obtained MnFe2O4 / GO wave absorption aerogel is shown in Figure 4 As can be seen from the figure, when the thickness of the material is 4.9 mm, the minimum reflection loss at 9.01 GHz reaches -30.91 dB, and the widest effective absorption band reaches 4.70 GHz, which has effective wave absorption performance. The SEM image of the MnFe2O4 / GO wave absorption aerogel sample is shown in Figure 5 .

[0074] Example 3

[0075] 1) Take 3.957 g of FeCl3·6H2O and fully dissolve in 50 ml of deionized water, take 3.957 g of MnCl2·4H2O and fully dissolve in 25 ml of deionized water. Take 5 g of polyethylene glycol and dissolve in 50 ml of deionized water to obtain solution A.

[0076] 2) The FeCl3 solution and MnCl2 solution obtained in step 1) are mixed uniformly in a three-necked flask with a small amount of dilute sulfuric acid.

[0077] 3) The three-necked flask is placed in a water bath, solution A is added, stirred at 60 ℃ for a period of time, and then sodium hydroxide solution is added to adjust the pH to 11, and then reacted for 2 h to obtain solution B.

[0078] 4) The solution B obtained in step 3) is repeatedly washed with deionized water until the pH is neutral to obtain solution C.

[0079] 5) Take 2g of graphene oxide, dissolve in 200ml of deionized water, ultrasonic treatment, then fully stirred, to obtain a brown yellow graphene oxide solution.

[0080] 6) The solution C obtained in step 4) is mixed with the graphene solution obtained in step 5) in a volume ratio of 22:50, stirred at room temperature for 8-18h to obtain solution D.

[0081] 7) The solution D obtained in step 6) is frozen at-20 to-90℃ for 12-24h, and dried for 12-72h.

[0082] 8) The MnFe2O4 / GO aerogel obtained in step 7) is placed in a tube furnace and heat treated at 300℃ for 2h under nitrogen atmosphere to obtain MnFe2O4 / GO aerogel.

[0083] The obtained MnFe2O4 / GO aerogel doped with paraffin is prepared into a coaxial ring sample (the inner diameter of the coaxial ring sample is 3mm, and the outer diameter is 7mm), the electromagnetic parameters of the sample are measured by a vector network analyzer, and then the wave absorption performance of the material is calculated by CST STUDIO SUITE software. The wave absorption performance of the obtained MnFe2O4 / GO wave absorption aerogel is as shown in Figure 6 From the figure, it can be seen that when the thickness of the material is 2.8mm, the minimum reflection loss at 16.43GHz reaches-54.98dB, and the widest effective absorption frequency band reaches 5.87GHz, which has effective wave absorption performance. The SEM image of the MnFe2O4 / GO wave absorption aerogel sample is as shown in Figure 7

[0084] From Examples 1-3, it can be seen that the aerogels with different proportions all show significant wave absorption ability at a specific frequency, and the minimum reflection loss is less than-29dB, among which the minimum reflection loss of Example 3 can reach-54.98dB (16.43GHz, thickness 2.8mm), indicating that the material has a strong attenuation ability to electromagnetic waves. The effective absorption frequency band is more than 4.7GHz, and Example 3 can reach 5.87GHz, covering a wide microwave frequency band (such as X band, Ku band, etc.), meeting the demand of wide frequency wave absorption material.

[0085] ​By adjusting the volume ratio of MnFe2O4 precursor solution (solution C) and graphene oxide solution (11:100 for example 1, 11:50 for example 2, 22:50 for example 3), the key parameters of the wave absorption performance can be significantly affected, including: the minimum absorption peak from 9.46 GHz in example 1, to 9.01 GHz in example 2, to 16.43 GHz in example 3, covering a range from low frequency to high frequency, indicating that the wave absorption frequency band can be adjusted by ratio adjustment. The thickness range is 2.8-4.9mm, among which example 3 realizes higher frequency strong wave absorption effect at a thinner thickness (2.8mm), which embodies the lightweight advantage of the material.

[0086] SEM images Figure 3 、 5 , 7) show that aerogels with different ratios have specific microstructures, which may be porous networks or layered composite structures. Such structures are beneficial to multiple scattering and loss of electromagnetic waves, and combined with the magnetic loss of MnFe2O4 and the dielectric loss of graphene oxide, a synergistic wave absorption effect is formed.

[0087] The preparation process is realized by co-precipitation-freeze drying-heat treatment process, which has strong step repeatability, and by doping paraffin to make coaxial ring samples, it is proved that the material can be compounded with the matrix, which is suitable for actual device preparation. Heat treatment at 300℃ in nitrogen atmosphere ensures the structural stability of the material, avoids oxidation, and ensures the reliability of the wave absorption performance.

[0088] MnFe2O4 / GO aerogel realizes excellent wave absorption performance with low reflection loss, wide effective absorption frequency band and adjustable thickness by adjusting the composite ratio of MnFe2O4 and graphene oxide, which has significant application potential in the field of microwave absorption (such as stealth materials, electromagnetic interference shielding, etc.). Among them, the ratio of example 3 (volume ratio 22:50) shows the best performance, with high attenuation ability and wide frequency characteristics, providing a direction for further optimization of the material.

[0089] Therefore, the MnFe2O4 / GO wave-absorbing aerogel with a directional pore structure and its preparation method adopt the above structure, the obtained aerogel includes graphene with a directional honeycomb pore structure connected to each other, the unique wrinkles on the surface of the uppermost graphene are clearly visible, and the microspherical manganese ferrite is distributed on the surface of the layered graphene. The aerogel has an extremely light weight and can be easily supported by a grass branch, and through the synergistic effect between dielectric loss and magnetic loss, and the multiple interface polarization between graphene and MnFe2O4, the microwave absorption effect is enhanced.

[0090] It should be pointed out finally that the above examples are only used to illustrate the technical solutions of the present application but not to limit it, and although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can still be modified or replaced equivalently, and these modifications or equivalent replacements should not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for preparing MnFe2O4 / GO wave-absorbing aerogel with a directional aperture structure, characterized in that, Specifically comprising the following preparation steps: 1) weigh an appropriate amount of FeCl3·6H2O and MnCl2·4H2O, respectively, and fully dissolve in deionized water to obtain FeCl3 solution and MnCl2 solution; weigh an appropriate amount of polyethylene glycol and dissolve in deionized water to obtain solution A; 2) mix the FeCl3 solution and MnCl2 solution obtained in step 1) uniformly in a three-necked flask with a small amount of dilute sulfuric acid; 3) place the three-necked flask in a water bath, add solution A, stir at an appropriate temperature, add sodium hydroxide solution to adjust the pH, and then fully react to obtain solution B; 4) wash the solution B obtained in step 3) with deionized water repeatedly until the pH is neutral to obtain solution C; 5) weigh an appropriate amount of graphene oxide, dissolve in deionized water, ultrasonic treatment, and then fully stir to obtain a brownish yellow graphene oxide solution; 6) mix the solution C obtained in step 4) with the graphene oxide solution obtained in step 5) according to a certain volume ratio, stir at room temperature for 8-18h to obtain solution D; 7) perform directional freezing and drying treatment on the solution D obtained in step 6); the freezing temperature is -20 to -90℃, the time is 12-24h, and the drying time is 12-72h; 8) place the MnFe2O4 / GO aerogel obtained in step 7) in a tube furnace, perform heat treatment under the protection of an atmosphere, and obtain MnFe2O4 / GO aerogel; the protective atmosphere is one of nitrogen and argon, the heating rate of heat treatment is 1-15℃ / min, the holding temperature is 200-700℃, and the holding time is 1-6h; The obtained MnFe2O4 / GO aerogel has magnetic particles MnFe2O4 uniformly loaded on the surface of graphene, and has a three-dimensional loose porous structure.

2. The preparation method of the MnFe204 / GO wave-absorbing aerogel with a directional aperture structure according to claim 1, characterized in that, In step 1), the molar ratio of FeCl3·6H2O to deionized water is 1-6:9-20, the molar ratio of MnCl2·4H2O to deionized water is 1-5:18-45, and the mass ratio of polyethylene glycol to deionized water is 3-8:

100.

3. The method according to claim 1, wherein the method is characterized in that, In step 3), the reaction temperature is 60-100℃, the stirring time is 10-60min, the reaction time is 1-5h, and the pH is greater than 11.

4. The method according to claim 1, wherein the method for preparing the MnFe204 / GO wave-absorbing aerogel with a directional aperture structure is characterized in that, In step 4), the volume of solution C is controlled to be 100-400ml.

5. The method according to claim 1, wherein the method is characterized in that, In step 5), the mass ratio of graphene oxide to deionized water is 1-10:

100.

6. The method according to claim 1, wherein the method is characterized in that, In step 6), the mass ratio of manganese ferrite in solution C to graphene in graphene oxide solution is 1-8:4-12.

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