Preparation method and application of sphere-like Fe3O4-BaTiO3 wave-absorbing material

Abstract

The invention provides a preparation method and application of a sphere-like Fe3O4-BaTiO3 wave-absorbing material. The preparation method comprises the following steps: (1) carrying out morphology finishing on Fe3O4 by taking CaF2 as a mineralizing agent to obtain sphere-like Fe3O4; and (2) by taking tetrabutyl titanate and barium acetate as a titanium source and a barium source, covering the surface of the spheroidal Fe3O4 with the BaTiO3 gel, and then introducing Ar for calcining to obtain the spheroidal Fe3O4-BaTiO3 composite wave-absorbing material. According to the preparation method, the filling performance of the material in a resin matrix is improved by performing morphology finishing on Fe3O4, and meanwhile, the surface of the sphere-like Fe3O4 is coated with a layer of BaTiO3, so that the loss mechanism of the material is enriched, the interface polarization effect is generated, and the wave-absorbing performance of the material is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave absorbing materials, and particularly relates to a preparation method and application of spherical-like Fe3O4@BaTiO3 microwave absorbing materials. Background Art

[0002] With the wide application of electronic devices, the potential hazards of electromagnetic radiation to the environment and human health have attracted increasing attention. Microwave absorbing materials can effectively absorb electromagnetic waves, reduce the leakage of electromagnetic radiation and electromagnetic interference inside or between devices. Microwave absorbing materials are usually prepared by using polymer resins as the matrix and adding microwave absorbing agents such as metal micro-powders and ferrites. As a traditional microwave absorbing material, Fe3O4 has the advantages of cheap raw materials, low specific gravity, strong antioxidant performance, etc. compared with metal micro-powders such as carbonyl iron powder, but it has inherent defects such as narrow absorption bandwidth and low absorption intensity, and cannot meet the requirements of modern electronic devices for microwave absorbing materials of "light, thin, wide, and strong".

[0003] To break through the performance bottleneck of Fe3O4 single-component microwave absorbing agents, the existing technologies mainly evolve along two technical routes: First, a composite system is constructed by introducing carbon-based materials. For example, Patent No. CN 109627488 A discloses a preparation method of a graphene composite nano-Fe3O4 radar wave absorbing material. By grinding the graphene composite nano-Fe3O4, the obtained graphene composite nano-Fe3O4 radar wave absorbing material has the characteristics of low density, thin thickness, wide frequency band, and strong electromagnetic wave absorption. However, the prominent defect of this patent is the large specific surface area and morphological differences between the used nano-Fe3O4 and two-dimensional graphene sheets. The large specific surface area results in poor dispersibility and filling performance in the resin matrix, and easy agglomeration, which will lead to poor processing performance and low yield of the finished product; the morphological differences lead to only point contact interfaces being formed during mechanical mixing, severely restricting the interfacial polarization effect. Second, the core-shell structure design is adopted to strengthen the synergistic effect. For example, Patent No. CN 113329608 A discloses a preparation method of a nano-barium titanate / tetragonal ferrite hybrid material with high microwave absorbing performance. In this method, nano-Fe3O4 particles are directly deposited in-situ on the surface of nano-BaTiO3 in a solution to form hybrid material powders, and the obtained materials strongly absorb and scatter electromagnetic waves in various frequency bands. However, the nano-barium titanate / tetragonal ferrite prepared by this patent also has small particle size and serious agglomeration, and poor dispersibility and filling performance in the resin matrix. In order to better improve the application of Fe3O4-based composite materials, this patent designs a novel spherical-like Fe3O4@BaTiO3 core-shell structure microwave absorbing material. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention aims to provide a quasi-spherical Fe3O4@BaTiO3 absorbing material, and another aim is to provide a method for preparing the quasi-spherical Fe3O4@BaTiO3 absorbing material. In the quasi-spherical Fe3O4@BaTiO3 absorbing material prepared by the present invention, BaTiO3 is evenly distributed on the surface of Fe3O4, ensuring multiple reflection paths of electromagnetic waves; in particular, the quasi-spherical morphology can reduce the surface energy, greatly improving the uniformity of its dispersion in polymer resin, and is particularly suitable for use in silicone gaskets.

[0004] A preparation method and application of a spherical Fe3O4@BaTiO3 absorbing material, the specific preparation steps are as follows: (1) Morphology of Fe3O4: Weigh a certain amount of irregular Fe3O4, add a certain amount of anhydrous isopropanol and CaF2, and disperse in a high-efficiency mixer. Place the dispersed Fe3O4 in an oven and dry at 150°C. Place the dried Fe3O4 in a high-temperature furnace and calcine at high temperature under Ar atmosphere to obtain spherical Fe3O4; (2) Preparation of Fe3O4@BaTiO3: Weigh a certain amount of tetrabutyl titanate and dissolve it in an appropriate amount of anhydrous ethanol, and stir it thoroughly to prepare solution A; mix a certain amount of barium acetate and acetic acid to prepare solution B; then mix solution A, solution B and a certain amount of spherical Fe3O4 prepared in step (1), add deionized water dropwise to the mixed solution at 30°C, adjust the pH value of the solution to 4.0 with acetic acid while stirring, continue stirring for 30 minutes, place the mixture in an 80°C water bath for gelation, let it stand for 24 hours and then dry to obtain a solid product, grind the solid product into powder using a planetary ball mill, and place it in a high-temperature furnace for high-temperature calcination under Ar atmosphere to obtain spherical Fe3O4@BaTiO3.

[0005] In the step (1), the irregular Fe3O4 has a particle size of 5-30 μm.

[0006] In the step (1), the mass ratios of irregular Fe3O4, anhydrous isopropanol and CaF2 are 1:0.15-0.3:0.01-0.06 respectively.

[0007] In the step (1), the rotation speed of the high-efficiency mixer is 200-700 r / min; and the dispersion time is 10-30 min.

[0008] In the step (1), the calcination temperature is 800-1100° C. and the calcination time is 6-10 hours.

[0009] In the step (2), the mass ratio of tetrabutyl titanate to anhydrous ethanol is 1:1.2-1.5.

[0010] In step (2), the mass ratio of barium acetate to acetic acid is 1:5 - 5.5.

[0011] In step (2), the mass ratio of solution A, solution B to the spherical-like Fe3O4 prepared in step (1) is 1:2.5 - 3.2:4.5 - 8.5.

[0012] In step (2), the mass ratio of the mixed solution to deionized water is 20 - 23.8:1.

[0013] In step (2), the rotation speed of the planetary ball mill is 400 - 600 r / min; the ball milling time is 20 - 35 min.

[0014] In step (2), the calcination temperature of the high-temperature furnace is 900 - 1100 °C; the calcination time is 2 - 5 h.

[0015] Advantages of the technology of the present invention: (1) For the spherical-like Fe3O4@BaTiO3 wave-absorbing material of the present invention, the spherical-like Fe3O4 is used as the core and BaTiO3 is used as the shell layer. As a magnetic loss material, Fe3O4 has a high magnetic loss ability in the radar band. As a dielectric loss material, the BaTiO3 shell layer not only enriches the loss mechanism of Fe3O4, but also the interfacial polarization effect between Fe3O4 and BaTiO3 further enhances the absorption and dissipation effect of the composite wave-absorbing material on electromagnetic wave energy. (2) The spherical-like Fe3O4@BaTiO3 wave-absorbing material of the present invention has excellent filling performance in the resin matrix. By changing the morphology of Fe3O4 from irregular to spherical-like, its specific surface area is effectively reduced, significantly improving the filling performance of the material in the resin matrix and improving the overall performance of the composite material. Description of the drawings

[0016] Figure 1 It is the scanning electron micrograph of blank example 1

[0017] Figure 2 It is the scanning electron micrograph of comparative example 1

[0018] Figure 3 It is the scanning electron micrograph of example 1 Specific implementation manners

[0019] To better understand the invention, the content of the present invention will be further clarified below in combination with implementation examples. However, the content of the present invention is not limited to the following implementation examples. Other implementation examples obtained by those skilled in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0020] Example 1 (1) Morphology modification of Fe3O4: Weigh 100 g of 5-μm irregular Fe3O4, add 15 g of anhydrous isopropanol and 1 g of CaF2, and disperse them in a high-efficiency mixer. The rotation speed of the high-efficiency mixer is set at 700 r / min for 10 min of dispersion. Place the dispersed Fe3O4 in an oven and dry it at 150 °C. Then put the dried Fe3O4 into a high-temperature furnace and calcine it at 1100 °C for 6 h in an Ar atmosphere to obtain spherical Fe3O4; (2) Preparation of Fe3O4@BaTiO3: Weigh 100 g of tetrabutyl titanate and dissolve it in 120 g of anhydrous ethanol, and make solution A after sufficient stirring; Mix 10 g of barium acetate and 50 g of acetic acid in a certain amount to make solution B; Then mix 10 g of solution A, 25 g of solution B and 45 g of the spherical Fe3O4 prepared in step (1) evenly. At 30 °C, slowly add 4 g of deionized water drop by drop to the mixed solution, adjust the pH value of the solution to 4.0 with acetic acid while stirring, continue stirring for 30 min, then place the mixture in an 80 °C water bath for gelation, let it stand for 24 h and then dry to obtain a solid product. Use a planetary ball mill to mill the solid product at 400 r / min for 20 min, then put it into a high-temperature furnace and calcine it at 1100 °C for 4 h in an Ar atmosphere to obtain spherical Fe3O4@BaTiO3.

[0021] Example 2 (1) Morphology modification of Fe3O4: Weigh 100 g of 5-μm irregular Fe3O4, add 15 g of anhydrous isopropanol and 1 g of CaF2, and disperse them in a high-efficiency mixer. The rotation speed of the high-efficiency mixer is set at 700 r / min for 10 min of dispersion. Place the dispersed Fe3O4 in an oven and dry it at 150 °C. Then put the dried Fe3O4 into a high-temperature furnace and calcine it at 800 °C for 10 h in an Ar atmosphere to obtain spherical Fe3O4; (2) Preparation of Fe3O4@BaTiO3: Weigh 100 g of tetrabutyl titanate and dissolve it in 120 g of anhydrous ethanol, and make solution A after sufficient stirring; Mix 10 g of barium acetate and 50 g of acetic acid in a certain amount to make solution B; Then mix 10 g of solution A, 25 g of solution B and 45 g of the spherical Fe3O4 prepared in step (1) evenly. At 30 °C, slowly add 4 g of deionized water drop by drop to the mixed solution, adjust the pH value of the solution to 4.0 with acetic acid while stirring, continue stirring for 30 min, then place the mixture in an 80 °C water bath for gelation, let it stand for 24 h and then dry to obtain a solid product. Use a planetary ball mill to mill the solid product at 400 r / min for 20 min, then put it into a high-temperature furnace and calcine it at 900 °C for 2 h in an Ar atmosphere to obtain spherical Fe3O4@BaTiO3.

[0022] Example 3 (1) Morphology finishing of Fe3O4: Weigh 100g of 5μm irregular Fe3O4, add 15g of anhydrous isopropanol and 4g of CaF2 and disperse in a high-efficiency mixer. Set the speed of the high-efficiency mixer to 700r / min and disperse for 10min. Place the dispersed Fe3O4 in an oven at 150℃ to dry. Place the dried Fe3O4 in a high-temperature furnace and calcine it at 1100℃ under Ar atmosphere for 6h to obtain spherical Fe3O4; (2) Preparation of Fe3O4@BaTiO3: 100 g of tetrabutyl titanate was weighed and dissolved in 120 g of anhydrous ethanol, and the mixture was stirred to prepare solution A; 10 g of barium acetate and 50 g of acetic acid were mixed in a certain amount to prepare solution B; 10 g of solution A, 32 g of solution B and 65 g of the spherical Fe3O4 prepared in step (1) were mixed evenly, 4 g of deionized water was added dropwise to the mixed solution at 30°C, and the pH value of the solution was adjusted to 4.0 with acetic acid while stirring. After stirring for 30 min, the mixture was placed in a water bath at 80°C for gelation, and dried after standing for 24 h to obtain a solid product. The solid product was ball-milled for 20 min using a planetary ball mill at 400 r / min, and then placed in a high-temperature furnace for calcination at 1100°C under Ar atmosphere for 4 h to obtain spherical Fe3O4@BaTiO3.

[0023] Comparative Example 1 The preparation method of Comparative Example 1 is similar to that of Example 1, except that the morphology of Fe3O4 is not subjected to morphological finishing. The other steps and amounts are the same as those of Example 1.

[0024] Comparative Example 2 Comparative Example 2 is a physical mixture product of Fe3O4 and BaTiO3 powders of the same specific gravity as the spherical Fe3O4@BaTiO3 product of Example 1; Comparative Example 1 is a wave absorbing and heat conducting material formed by mixing 5μm spherical Fe3O4 and 2μm BaTiO3 in a mass ratio of 7:3. The specific preparation method is as follows: 700g of spherical Fe3O4 and 300g of BaTiO3 are weighed and placed in a 10L mixer and mixed evenly, wherein the mixing speed is 250r / min and the mixing time is 10min.

[0025] Comparative Example 3 Comparative Example 3 is the spherical Fe3O4 prepared by morphological modification of Fe3O4 in step (1) of Example 1.

[0026] Blank example 1 Blank example 1 is 5 μm irregular Fe3O4.

[0027] Blank example 2 Blank Example 2 is 2μm barium titanate BaTiO3.

[0028] The microwave absorbing powder of the present invention can be used in silicone gaskets. The preparation steps of the silicone gasket are as follows: Weigh a certain amount of spherical Fe3O4@BaTiO3 and mixed silicone oil in a mass ratio of 1-6:1 and add them to a vacuum stirring and degassing machine to stir evenly to obtain a mixed base material; Place the mixed base material on a release film and set the calender thickness to 2 mm, the temperature to 150 °C, and the time to 15 min to obtain a silicone gasket. Among them, the mass ratio of 500 cP vinyl silicone oil, 0.18% side hydrogen-containing silicone oil, 3000 ppm platinum catalyst and ethynylcyclohexanol inhibitor (diluted 1:20) in the mixed silicone oil is 100:2.5-4.0:0.25-0.35:0.25-0.70.

[0029] Application Examples 1-8 The silicone microwave absorbing gaskets prepared in Examples 1-3 correspond to Application Examples 1-3, Comparative Examples 1-3 correspond to Application Examples 4-6, and Blank Examples 1-2 correspond to Application Examples 7-8. Preparation method of the silicone microwave absorbing gaskets in Application Examples 1-8: (1) Preparation of the mixed silicone oil: Weigh 100 g of 500 cP vinyl silicone oil, 3.5 g of 0.18% side hydrogen-containing silicone oil and 0.5 g of ethynylcyclohexanol inhibitor (diluted 1:20) in a plastic cup, mix them evenly, and then add 0.30 g of 3000 ppm platinum catalyst to further mix evenly to obtain the mixed silicone oil. (2) Preparation of the gasket: Weigh 30 g of the mixed silicone oil and 120 g of the microwave absorbing powder, set the rotation speed to 600 r / min in a vacuum stirring and degassing machine, and stir for 2 min to obtain a mixed base material; Place the mixed base material on a release film and set the calender thickness to 2 mm, the temperature to 150 °C, and the time to 15 min to obtain a silicone gasket.

[0030] The test methods and standards for each performance are as follows: Microwave absorbing performance test: The microwave absorbing performance is tested by the coaxial method of a vector network analyzer, and its dielectric constant and magnetic permeability are measured to calculate the reflection loss (RL) at a thickness of 2 mm. The formula is as follows, and the equipment model used is N5222B; Maximum filling amount: Continuously add the microwave absorbing material to 500 cp vinyl silicone oil, disperse it preliminarily, and then place it in a vacuum stirring and degassing machine, set the rotation speed to 600 r / min, and stir for 2 min until the colloid becomes a hard mass and it is difficult to continue filling, then the maximum filling amount can be obtained;

[0031] The preparation process of the microwave absorbing performance test sample is as follows: Cut the gasket of the application example with a mold to make a sample with an inner diameter of 3.04 mm, an outer diameter of 7.00 mm, and a thickness of 2 mm

[0032] The performance tests of the spherical Fe3O4@BaTiO3 composite absorbing materials prepared in each example are shown in Table 1.

[0033] Table 1:

[0034] In Application Examples 1-8, the spherical Fe3O4@BaTiO3 composite absorbing materials prepared in Examples 1-3 of the present invention, Comparative Examples 1-3, and Blank Examples 1-2 were respectively filled in vinyl silicone oil to test the maximum filling ratio, and silicone gaskets were prepared to test their absorbing properties. In the above table, Examples 1-3 correspond to Application Examples 1-3 in sequence, Comparative Examples 1-3 correspond to Application Examples 4-6 in sequence, and Blank Examples 1-2 correspond to Application Examples 7-8 in sequence. (1) From the scanning electron microscope images of Comparative Example 3 and Blank Example 1, it can be seen that by step (1) of Example 1, the morphology of Fe3O4 was changed from irregular to spherical. Mainly by adding CaF2 and calcining, the melting point of Fe3O4 was reduced, so that the rough positions at the edges of the powder formed a molten state preferentially, thus achieving the purpose of morphology finishing. (2) As can be seen from Table 1, the filling performance of the absorbing material in the resin matrix has a great influence on its morphology and structure. Compared with Application Example 7, the filling ratio of Application Example 6 increased by 46%; compared with Application Example 4, the filling ratio of Application Example 1 increased by 75%. This shows that the spherical morphology has a higher filling amount in the resin matrix because of its small specific surface area, high packing density, and little influence on the viscosity of the matrix resin. (3) As can be seen from Table 1, the absorbing performance of the absorbing material has a great influence on the material composite and its structure. Compared with Application Example 5, Application Example 6, and Application Example 8, the peak reflection loss of the spherical Fe3O4@BaTiO3 composite absorbing material in Application Example 1 decreased by 100%, 225%, and 73% respectively, and △W5 (the bandwidth with < -5 dB) increased by 33.3%, 100%, and 200% respectively. The core-shell structure formed by the spherical Fe3O4@BaTiO3 formed an interfacial polarization effect at the interface between Fe3O4 and BaTiO3, thus improving the absorbing performance of the material.

Claims

1. A method for preparing a spherical Fe3O4@BaTiO3 absorbing material, the specific preparation steps are as follows: (1) Morphology of Fe3O4: Weigh a certain amount of irregular Fe3O4, add a certain amount of anhydrous isopropanol and CaF2, and disperse in a high-efficiency mixer; place the evenly dispersed mixed solution in an oven and dry at 150°C; place the dried solid powder in a high-temperature furnace and calcine at high temperature under Ar atmosphere to obtain spherical Fe3O4; (2) Preparation of Fe3O4@BaTiO3: Weigh a certain amount of tetrabutyl titanate and dissolve it in an appropriate amount of anhydrous ethanol, and stir it thoroughly to prepare solution A; mix a certain amount of barium acetate and acetic acid to prepare solution B; then mix solution A, solution B and a certain amount of spherical Fe3O4 prepared in step (1), add deionized water dropwise to the mixed solution at 30°C, adjust the pH value of the solution to 4.0 with acetic acid while stirring, continue stirring for 30 minutes, place the mixture in an 80°C water bath for gelation, let it stand for 24 hours and then dry to obtain a solid product, grind the solid product into powder using a planetary ball mill, and place it in a high-temperature furnace for high-temperature calcination under Ar atmosphere to obtain spherical Fe3O4@BaTiO3.

2. The preparation method of a spherical-like Fe3O4@BaTiO3 wave-absorbing material according to claim 1, characterized in that, In the step (1), the irregular Fe3O4 has a particle size of D50=5-30 μm.

3. The preparation method of a spherical-like Fe3O4@BaTiO3 wave-absorbing material according to claim 1, characterized in that, In the step (1), the mass ratios of irregular Fe3O4, anhydrous isopropanol and CaF2 are 1:0.15-0.3:0.01-0.06 respectively.

4. The preparation method of a spherical-like Fe3O4@BaTiO3 wave-absorbing material according to claim 1, characterized in that, In the step (1), the rotation speed of the high-efficiency mixer is 200-700 r / min; and the dispersion time is 10-30 min.

5. The preparation method of a spherical-like Fe3O4@BaTiO3 wave-absorbing material according to claim 1, characterized in that, In the step (1), the calcination temperature of the high temperature furnace is 800-1100° C. and the calcination time is 6-10 hours.

6. The preparation method of a quasi-spherical Fe3O4@BaTiO3 wave-absorbing material according to claim 1, characterized in that, In the step (2), the mass ratio of tetrabutyl titanate to anhydrous ethanol is 1:1.2-1.

5.

7. The preparation method of a spherical-like Fe3O4@BaTiO3 wave-absorbing material according to claim 1, characterized in that, In the step (2), the mass ratio of barium acetate to acetic acid is 1:5-5.

5.

8. The preparation method of a kind of spherical Fe3O4@BaTiO3 microwave absorbing material according to claim 1, characterized in that, In the step (2), the mass ratio of solution A, solution B and the spherical Fe3O4 obtained in the step (1) is 1:2.5-3.2:4.5-8.

5.

9. The preparation method of a spherical-like Fe3O4@BaTiO3 wave-absorbing material according to claim 1, characterized in that, In the step (2), the mass ratio of the mixed solution to deionized water is 20-23.8:

1.

10. The preparation method of a spherical-like Fe3O4@BaTiO3 wave-absorbing material according to claim 1, characterized in that, In the step (2), the rotation speed of the planetary ball mill is 400-600 r / min; and the ball milling time is 20-35 min.

11. The preparation method of a kind of spherical Fe3O4@BaTiO3 microwave absorbing material according to claim 1, characterized in that, In the step (2), the calcination temperature of the high temperature furnace is 900-1100° C. and the calcination time is 2-5 hours.

12. The preparation method of a kind of spherical Fe3O4@BaTiO3 wave-absorbing material according to any one of claims 1-11, characterized in that, The wave-absorbing powder is suitable for organic silicon gaskets.

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