Quaternary EuFeO3 / Eu2O3 / Fe-C aerogel wave-absorbing composite material

Abstract

The invention discloses a preparation method of a quaternary EuFeO3 / Eu2O3 / Fe-C aerogel wave-absorbing composite material, and relates to a preparation method of an aerogel wave-absorbing material. The invention aims to solve the technical problem of poor microwave absorption performance of the existing aerogel wave-absorbing material. The quaternary composite aerogel material EuFeO3 / Eu2O3 / Fe (at) C with a 3D network structure is prepared by changing the form of MOFs and taking 3d-4f-MOG / HCNT gel formed by self-assembly of metal organic gel and carbon nanotubes HCNTs with a spiral structure as a precursor. The quaternary heterogeneous interface can generate a large amount of electron transfer and abundant spin orbit interaction, and the carbon nano tube has a carbon component and a polarization center, so that the polarization loss and the conductive loss are greatly improved. In addition, the spiral structure can induce cross polarization under continuous microwave irradiation, so that the electromagnetic loss of the aerogel material is enhanced, and attenuation of electromagnetic waves is facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of aerogel wave-absorbing material. BACKGROUND

[0002] The progress of wireless communication technology has greatly promoted social progress, however, this progress is accompanied by the challenge of microwave pollution, which not only interrupts the normal operation of electronic equipment, but also poses potential risks to human health. In real life, wave-absorbing materials play an important role in improving equipment performance, health protection and privacy security by optimizing the electromagnetic environment; in national defense technology, microwave absorbing materials will play a key role in future intelligent warfare; in the military field, wave-absorbing materials are widely used in the coating of military equipment to improve combat capability by absorbing radar waves. Therefore, the research of high-performance wave-absorbing materials is of great significance.

[0003] The widely used wave-absorbing material is ferrite wave-absorbing material, however, ferrite wave-absorbing material has the problems of large density, poor corrosion resistance and complex preparation process, ferrite belongs to ceramic material, which has high hardness but large brittleness, and is easy to crack or peel off, so it is difficult to be applied in the military field. Compared with traditional wave-absorbing materials, aerogel material has low density, three-dimensional porous structure, and can adjust electromagnetic parameters and optimize impedance matching, so the microwave absorption (MA) performance of aerogel is much higher than that of traditional wave-absorbing materials.

[0004] Metal organic gel shows significant advantages in the field of wave-absorbing materials, mainly due to its unique structure adjustability, porosity and composite function characteristics. Metal organic gel has become an important candidate for new generation of wideband, strong absorption and environmentally adaptive wave-absorbing materials due to its customizable electromagnetic parameters, lightweight porous structure and multi-functional integration capability, especially suitable for stealth coating, electromagnetic shielding and other fields. Future research direction will focus on precise regulation of multi-scale structure and breakthrough in practical application.

[0005] Multi-component composite material constructs rich heterogeneous interfaces, shows enhanced interface polarization effect, effectively improves the absorption efficiency of electromagnetic wave, and shows great advantages in wave-absorbing performance. Zhu et al. prepared a new type of four-component magnetic core-shell-shell structure FeCo-Co@Fe3O4@SiO2 (FCSF), due to the polarization effect of multi-component, FCSF composite material has excellent wave-absorbing performance, when the filling ratio is 70wt%, the RL minand the effective absorption band can reach-42.8 dB and 7.3 GHz (Zhu Y, Li J, Li X, et al. Heterointerface engineering in quaternary magnetic structures for high-efficiency and thermal stable microwave absorption[J]. Journal of Alloys and Compounds, 2022, 924: 166461.).

[0006] The spiral structure of the spiral carbon nanotube produces more electromagnetic cross polarization, and exhibits good microwave absorption performance. He et al. prepared a LaFeO3 / Fe3O4 / C perovskite composite powder material with a spiral structure, and the RLmin value of the material reached-42.3 dB, and the EAB was 4.7 GHz (He X, Xiong Z, Lei C, et al. Excellent microwave absorption performance of LaFeO3 / Fe3O4 / C perovskite composites with optimized structure and impedance matching[J]. Carbon, 2023, 213: 118200.). SUMMARY

[0007] The present application is to solve the technical problem of poor microwave absorption performance of existing aerogel wave-absorbing materials, and to provide a quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material.

[0008] The quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material of the present application is prepared by the following steps:

[0009] I. Dissolve trimesic acid in a mixture of deionized water and anhydrous ethanol to obtain solution A; the volume ratio of deionized water to anhydrous ethanol is 1:(3~4); the mass of trimesic acid to the volume of deionized water is 1g:(3mL~4mL);

[0010] mixing nine hydrated ferric nitrate, hydrated europium acetylacetone and HCNTs, and then dissolving them in deionized water to obtain solution B; the mass ratio of the nine hydrated ferric nitrate and the hydrated europium acetylacetone is 1:(1~1.2); the mass ratio of the nine hydrated ferric nitrate and the HCNTs is 7.5:(1~1.2); the mass of the HCNTs to the volume of the deionized water is 1g:(30mL~35mL);

[0011] ultrasonic treatment is performed on solution A and solution B respectively, solution A is slowly added into solution B, and then stirring and mixing are performed for 10min~12min, and then the gel is formed by static aging; the mass ratio of the trimesic acid in solution A to the HCNTs in solution B is 5:(1~1.2);

[0012] II. The gel obtained in step I is dried to obtain a FeEu-MOG / HCNT precursor; the FeEu-MOG / HCNT precursor is calcined at a high temperature of 700℃~750℃ for 2h~2.5h under the protection of a protective gas, and then the temperature is naturally reduced to room temperature to obtain a quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material.

[0013] The 3D network structure quaternary composite aerogel material EuFeO3 / Eu2O3 / Fe@C is prepared by changing the morphology of MOFs, taking the 3d-4f-MOG / HCNT gel self-assembled from the metal organic gel and the carbon nanotube HCNTs with a spiral structure as a precursor. The quaternary heterojunction can produce a large number of electron transfer and rich spin-orbit interaction, and the carbon nanotube has carbon composition and polarization center (including a defect edge and an interface), which greatly improves the polarization loss and the conductive loss. In addition, the spiral structure can induce cross polarization under continuous microwave irradiation, thereby enhancing the electromagnetic loss of the aerogel material and helping to attenuate electromagnetic waves.

[0014] The Eu ion and the HCNTs are introduced on the basis of the Fe-MOG aerogel material, the bimetallic Fe ion and the Eu ion are combined as the 3d-4f-MOG material, the ferromagnetic coupling between the 3d and 4f ions can cause a high spin ground state, the unpaired 4f electron can enhance the atomic magnetic moment caused by the electron orbit and the spin motion, the electromagnetic loss is enhanced, the dielectric loss and the electromagnetic loss are improved, the impedance matching is further optimized, and the high-efficiency microwave absorption performance is achieved.

[0015] The beneficial effects of the present application are as follows:

[0016] 1. The preparation method of the application is simple and fast, and the metal salt of Fe and Eu is combined with HCNTs and trimesic acid to prepare a FeEu-MOG / HCNT precursor for the first time, and then the uniform quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material is prepared by freeze-drying and pyrolysis;

[0017] 2. The quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material prepared by the application has excellent electromagnetic wave absorption performance, and can reach RL min -67.21 dB when the thickness is 2.78 mm; and when the matching thickness is only 2.07 mm, a 30% filling ratio in a paraffin matrix can obtain a wave-absorbing bandwidth of 6 GHz;

[0018] 3. The application has good market application prospect, low preparation cost, simple process, short cycle, and the prepared quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material has the advantages of low density, good electromagnetic wave absorption performance, good thermal stability and good chemical stability. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a real photo of the gel prepared in step one of test one;

[0020] Figure 2 It is a photo of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material prepared in step two of test one placed on a dog tail;

[0021] Figure 3 It is a PXRD graph of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material prepared in step two of test one;

[0022] Figure 4 It is a SEM graph of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material prepared in step two of test one;

[0023] Figure 5 It is a TEM graph of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material prepared in step two of test one;

[0024] Figure 6 It is a reflection loss spectrum of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material prepared in step two of test one;

[0025] Figure 7 It is a N2 adsorption-desorption isotherm of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material prepared in step two of test one;

[0026] Figure 8 3D RCS figure of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material prepared for step two of test one;

[0027] Figure 9 2D RCS figure of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material prepared for step two of test one;

[0028] Figure 10 Cole-Cole figure of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material prepared for step two of test one. DETAILED DESCRIPTION

[0029] Embodiment one: the embodiment is a preparation method of a quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material, which is specifically performed according to the following steps:

[0030] I. Dissolve trimesic acid in a mixed solution of deionized water and anhydrous ethanol to obtain solution A; the volume ratio of the deionized water to the anhydrous ethanol is 1:(3-4); the mass of the trimesic acid to the volume of the deionized water is 1g:(3mL-4mL);

[0031] Mix iron nitrate nonahydrate, europium acetylacetonate hydrate and HCNTs, and then dissolve them in deionized water to obtain solution B; the mass ratio of the iron nitrate nonahydrate to the europium acetylacetonate hydrate is 1:(1-1.2); the mass ratio of the iron nitrate nonahydrate to the HCNTs is 7.5:(1-1.2); the mass of the HCNTs to the volume of the deionized water is 1g:(30mL-35mL);

[0032] After the solution A and the solution B are respectively subjected to ultrasonic treatment, the solution A is slowly added to the solution B for stirring and mixing for 10-12 minutes, and then the mixture is left to stand to form a gel; the mass ratio of the trimesic acid in the solution A to the HCNTs in the solution B is 5:(1-1.2);

[0033] II. Dry the gel obtained in step one to obtain a FeEu-MOG / HCNT precursor; under the protection of a protective gas, the FeEu-MOG / HCNT precursor is calcined at a high temperature of 700-750°C for 2-2.5h, and then naturally cooled to room temperature to obtain a quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material.

[0034] Embodiment two: the embodiment is different from embodiment one in that the drying in step two is freeze drying for 48h. The other steps are the same as those in embodiment one.

[0035] Specific embodiment three: the difference between this embodiment and specific embodiment one or two is that the protective gas in step two is a mixed gas of H2 gas and Ar gas, wherein the volume fraction of H2 gas is 10%. The others are the same as specific embodiment one or two.

[0036] Specific embodiment four: the difference between this embodiment and any one of specific embodiments one to three is that the calcination temperature in step two is 700℃. The others are the same as any one of specific embodiments one to three.

[0037] Specific embodiment five: the difference between this embodiment and specific embodiment four is that the calcination time in step two is 2h. The others are the same as specific embodiment four.

[0038] The present application is verified by the following test:

[0039] Test one: this test is a preparation method of a quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material, specifically as follows:

[0040] I. 0.5g of trimesic acid is dissolved in a mixture of 1.5mL of deionized water and 5mL of anhydrous ethanol to obtain solution A;

[0041] 0.75g of iron nitrate nonahydrate, 0.75g of hydrated europium acetylacetone and 0.1g of HCNTs are mixed and then dissolved in 3mL of deionized water to obtain solution B;

[0042] After ultrasonic treatment of solution A and solution B respectively, solution A is slowly added to solution B and stirred and mixed for 10min, and then aged to form a gel;

[0043] II. The gel obtained in step I is freeze-dried for 48h to obtain a FeEu-MOG / HCNT precursor; the FeEu-MOG / HCNT precursor is calcined at a high temperature of 700℃ for 2h under the protection of a protective gas, and the heating rate is 2℃·min -1 Then naturally reduced to room temperature to obtain a quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material, named HEEFC-1; the protective gas is a mixed gas of H2 gas and Ar gas, wherein the volume fraction of H2 gas is 10%.

[0044] The HEEFC-1 is uniformly dispersed with paraffin wax, with the mass filling ratio of the HEEFC-1 being 30 wt%, and then the HEEFC-1 is pressed into an annular mold, and electromagnetic parameters of the HEEFC-1 are measured in the range of 2-18 GHz; through VSM and electromagnetic parameter tests and analysis and calculation of MA performance, it is found that the spiral carbon nanotube can enhance cross polarization of electromagnetic waves, and can optimize impedance matching of the material, and can widen effective absorption bandwidth (EAB) of the material at a thinner thickness.

[0045] Figure 1 A physical photograph of the gel prepared in step one of the test one can show that the gel does not fall off when the bottle is inverted, indicating that the gel is non-flowing.

[0046] Figure 2 A photograph of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material prepared in step two of the test one on a dogtail grass shows that the aerogel has an ultralow density.

[0047] Figure 3 A PXRD graph of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material prepared in step two of the test one shows that the HEEFC-1 composite material is composed of EuFeO3, Eu2O3, Fe and C. There is almost no impurity peak, indicating that the purity is high, and the product of the application is stable, which is beneficial to industrial production and popularization.

[0048] Figure 4 A high-magnification SEM graph of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material prepared in step two of the test one can show that the material is a 3D porous aerogel structure, in which spiral carbon nanotubes are interspersed.

[0049] Figure 5 A TEM graph of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material prepared in step two of the test one shows that the material has clear interface characteristics, a crystal lattice spacing of 0.389 nm corresponds to a (110) crystal face of EuFeO3 particles, a crystal lattice spacing of 0.15 nm corresponds to a (222) crystal face of Eu2O3, and a structure spacing of 0.146 nm corresponds to a (200) crystal face of Fe particles. In addition, clear multiple heterogeneous interfaces can be seen from the image, and these heterogeneous interfaces provide rich polarization sites for interface polarization, and dielectric loss is enhanced through polarization.

[0050] Figure 6 A reflection loss graph of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite material prepared in step two of the test one can show that when the thickness is 2.78 mm, the RL of the material is -10.24 GHz. min-67.21 dB, which is better than most wave-absorbing materials; and when the thickness is 2.07 mm, the effective absorption bandwidth is 6 GHz (12 GHz-18 GHz).

[0051] Figure 7 The N2 adsorption-desorption isotherm of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite prepared in step two of Test One is shown in the figure, and it can be seen from the figure that there is an adsorption hysteresis loop when P / P0>0.4, thus showing a typical IV-type isotherm, and the specific surface area is 74.44 m 2 / g. At the same time, the hysteresis loop isotherm has no obvious saturated adsorption platform, indicating that the pore structure is less regular. Figure 7 The small graph in the figure is a pore size distribution graph, which reveals that micropores, mesopores and macropores coexist in the EuFeO3 / Eu2O3 / Fe@C aerogel material, and it is mainly mesoporous material, and the average adsorption pore is 6.13 nm.

[0052] Figure 8 The 3D RCS of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite prepared in step two of Test One, Figure 9 The 2D RCS graph of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite prepared in step two of Test One, and the maximum RCS value is 29.9 dB·m 2 , indicating that the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite has excellent radar stealth performance.

[0053] Figure 10 The Cole-Cole curve graph of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel wave-absorbing composite prepared in step two of Test One, which shows multiple polarization relaxation processes, indicating that the quaternary composite has rich interface polarization.

Claims

1. A method for preparing a quaternary EuFeO3 / Eu2O3 / Fe@C aerogel microwave absorbing composite material, characterized in that... The preparation method of the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel microwave absorbing composite material is carried out according to the following steps:

1. Dissolve pyromellitic acid in a mixture of deionized water and anhydrous ethanol to obtain solution A; the volume ratio of deionized water to anhydrous ethanol is 1:(3~4); the mass ratio of pyromellitic acid to deionized water is 1g:(3mL~4mL). Ferric nitrate nonahydrate, europium acetylacetonate hydrate, and HCNTs were mixed and dissolved together in deionized water to obtain solution B; the mass ratio of ferric nitrate nonahydrate to europium acetylacetonate hydrate was 1:(1~1.2); the mass ratio of ferric nitrate nonahydrate to HCNTs was 7.5:(1~1.2); and the mass ratio of HCNTs to deionized water was 1g:(30mL~35mL). After sonicating solutions A and B separately, solution A is slowly added to solution B and stirred for 10 to 12 minutes, then allowed to stand and age to form a gel; the mass ratio of pyromellitic acid in solution A to HCNTs in solution B is 5:(1 to 1.2).

2. The gel obtained in step 1 is dried to obtain the FeEu-MOG / HCNT precursor; under the protection of a protective gas, the FeEu-MOG / HCNT precursor is calcined at a high temperature of 700℃~750℃ for 2h~2.5h, and then naturally cooled to room temperature to obtain the quaternary EuFeO3 / Eu2O3 / Fe@C aerogel microwave absorbing composite material.

2. The quaternary EuFeO3 / Eu2O3 / Fe@C aerogel microwave absorbing composite material according to claim 1, characterized in that... The drying process in step two involves freeze drying for 48 hours.

3. The quaternary EuFeO3 / Eu2O3 / Fe@C aerogel microwave absorbing composite material according to claim 1, characterized in that... The protective gas mentioned in step two is a mixture of H2 and Ar, wherein the volume fraction of H2 is 10%.

4. The quaternary EuFeO3 / Eu2O3 / Fe@C aerogel microwave absorbing composite material according to claim 1, characterized in that... The calcination temperature in step two is 700℃.

5. The quaternary EuFeO3 / Eu2O3 / Fe@C aerogel microwave absorbing composite material according to claim 1, characterized in that... The calcination time in step two is 2 hours.

Images