Electromagnetic wave absorption film controlled by magnet array and preparation method thereof

Abstract

The invention discloses an electromagnetic wave absorption film controlled by a magnet array and a preparation method thereof, and belongs to the field of electromagnetic wave absorption materials.The preparation method of the electromagnetic wave absorption film controlled by the magnet array comprises the following steps that electromagnetic wave absorption powder and a thermoplastic elastomer are mixed and dispersed in an organic solvent, stirring is conducted, and the electromagnetic wave absorption film is obtained; stirring until the thermoplastic elastomer is dissolved in the organic solvent and the electromagnetic wave absorbing powder is dispersed in the thermoplastic elastomer solution, continuously stirring and cooling to obtain a magnetic composite liquid; printing a magnet array mold, and selecting a liquid tank and a leveling platform according to the magnet array mold; transferring the magnetic composite liquid into a liquid tank, ventilating and drying, and obtaining the electromagnetic wave absorption film controlled by the magnet array after the organic solvent is volatilized; the thin film material with the structural design is prepared, and the problem that bending or stretching is difficult is solved.

Description

Technical Field

[0001] The invention belongs to the field of electromagnetic wave absorbing materials, and in particular relates to an electromagnetic wave absorbing film controlled by a magnet array and a preparation method thereof. Background Art

[0002] Electromagnetic wave absorbing materials play an increasingly important role in the electronic information age and even in the upcoming "smart age". High-performance electromagnetic wave absorbing materials help humans stay away from electromagnetic wave hazards. The structural design of absorbing materials has significant advantages in improving the electromagnetic wave absorption performance, because its unique structural design injects new infinite vitality into efficient electromagnetic wave absorbing materials. The structural design of materials is mainly based on the microscopic and macroscopic perspectives, and unique structural designs can be adopted for materials of different dimensions. For zero-dimensional materials, the structural design often chooses core-shell structure and stacking; for one-dimensional materials, weaving is often the best choice; for two-dimensional materials, most of their structural design schemes are multi-layer stacking, bending, etc.; for three-dimensional materials, cutting and periodic arrangement can often play a significant role. However, for two-dimensional materials with thin film materials as the main body, the performance improvement brought by the structure constructed by multi-layer stacking and bending is often limited. Therefore, the development of a new method for preparing two-dimensional absorbing materials will help to further enhance the electromagnetic wave absorption performance of thin film absorbing materials. In order to achieve effective structural design in a limited two-dimensional space, it is advantageous to prepare electromagnetic wave absorbing films by external magnetic field control. However, in current production, the following problems exist: 1. The control results of the external magnetic field are difficult to display intuitively, making it difficult to achieve further thin film structure design. 2. Traditional thin film preparation methods are difficult to adapt to external magnetic field control, making it difficult to ensure film quality. 3. Traditional thin film structure design lacks practicality and is difficult to bend or stretch. Therefore, there is an urgent need for a method for preparing an electromagnetic wave absorbing flexible film controlled by a magnet array to solve these problems. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides an electromagnetic wave absorbing film controlled by a magnet array and a preparation method thereof.

[0004] A method for simulating the magnetic field distribution generated by a magnet array comprises the following steps:

[0005] The steady-state magnetic field solution simulation of the magnet array is carried out through the software's current-free magnetic field physics field;

[0006] The model’s boundary is set as a magnetically insulated cuboid;

[0007] The initial value of the magnetic scalar potential inside the boundary is set, and the magnetic flux is kept conserved;

[0008] A matrix of small cubes is placed in an array within the boundary, and the cube size refers to the actual magnet size;

[0009] The material inside the boundary is set to air, and the small cube matrix is ​​set to the actual magnet parameters;

[0010] Execute the simulation to get the final simulated magnetic field distribution map.

[0011] A method for preparing an electromagnetic wave absorbing film controlled by a magnet array comprises the following steps:

[0012] The electromagnetic wave absorbing powder is mixed with the thermoplastic elastomer, dispersed in an organic solvent, stirred until the thermoplastic elastomer is dissolved in the organic solvent and the electromagnetic wave absorbing powder is dispersed in the thermoplastic elastomer solution, and stirred and cooled continuously to obtain a magnetic composite liquid;

[0013] Print the magnet array mold, and select the liquid tank and leveling platform according to the magnet array mold;

[0014] According to the magnet arrangement design, the actual magnets are embedded in the magnet array mold through the simulated magnetic field distribution diagram described in claim 1;

[0015] The magnetic composite liquid is transferred to a liquid tank, dried by ventilation, and the organic solvent is evaporated to obtain an electromagnetic wave absorbing film controlled by a magnet array.

[0016] Preferably, the electromagnetic wave absorbing powder includes one or more of iron, cobalt and nickel.

[0017] Preferably, the electromagnetic wave absorbing powder includes one or more of TPE, TPU, TPO and TPS.

[0018] Preferably, the mass ratio of the thermoplastic elastomer to the electromagnetic wave absorbing powder is 1:0.01-1:2.

[0019] Preferably, the method of dispersing the electromagnetic wave absorbing powder into the thermoplastic elastomer solution comprises one or more of ultrasonic dispersion, physical stirring and microwave digestion.

[0020] Preferably, the shape of the magnet array mold includes any one of spherical, rectangular and spindle shapes.

[0021] Preferably, the material of the liquid tank includes any one of glass or polytetrafluoroethylene.

[0022] The electromagnetic wave absorbing film controlled by the magnet array prepared by the above preparation method.

[0023] The method for simulating the magnetic field distribution generated by the magnet array is characterized in that the initial value of the magnetic scalar potential inside the boundary is set to 0 V / m.

[0024] The beneficial effects of the present invention include:

[0025] The design scheme of the present invention successfully combines computer simulation with design to achieve magnetic field control, and realizes the design and improvement of conventional film preparation methods to achieve adaptation to external magnetic field control. With thermoplastic elastomer as the matrix, a film material with structural design is prepared to solve the problem of difficulty in bending or stretching, and obtain more excellent electromagnetic wave absorption performance and structural design scheme. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 Schematic diagram of the preparation of magnetic composite liquid;

[0028] Figure 2 Designed for magnet arrangement;

[0029] Figure 3 .Visual simulation of magnetic field arrangement for magnets;

[0030] Figure 4 Designed for magnet array template;

[0031] Figure 5 This is a schematic diagram of the equipment assembly; in the figure: 1. Magnetic composite liquid; 2. Liquid tank; 3. Magnet array; 4. Leveling platform;

[0032] Figure 6 Schematic diagram of the arrangement of magnetic particles inside the film;

[0033] Figure 7 Physical demonstration of electromagnetic wave absorbing flexible film controlled by magnet array;

[0034] Figure 8 The arch method is used to test the electromagnetic wave absorption performance of (a) spaced arrangement, (b, c) strip arrangement film absorption performance;

[0035] Fig. 9 The arch method is used to test the electromagnetic wave absorption performance. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Example 1

[0038] The patent discloses a method for preparing a flexible electromagnetic wave absorbing film controlled by a magnet array, comprising the following steps:

[0039] Step 1: Mix electromagnetic wave absorbing powder prepared by mixing 390 g of carbonyl iron powder and 10 g of carbon fiber with 200 g of thermoplastic elastomer TPE, and disperse the mixture in 1000 mL of cyclohexane.

[0040] Step 2: Stirring continuously at 80° C. for 2 h to completely dissolve the thermoplastic elastomer TPE in cyclohexane, and stirring continuously to fully disperse the absorber in the thermoplastic elastomer solution.

[0041] Step 3, the mixed solution in step 2 is continuously stirred and naturally cooled to room temperature to obtain a magnetic composite liquid.

[0042] Step 4, select the size of 5x5x5 mm 3 Square magnets, printed using 3D printing technology, with a grid size of 5x5mm 2 , a grid magnet array mold with a height of 5mm and a wall thickness of 0.5mm. The mold contains 80 magnet units in length and width, and the length and width are 440mm respectively. According to the size of the mold, 440x440mm is selected 2 Liquid tank and leveling platform.

[0043] Step 5: Alternately arrange the NS poles of the magnets along the length and width directions, simulate the magnetic field distribution generated by the magnet array through COMSOL, and embed the actual magnets into the magnet array mold.

[0044] Step 6: Transfer the magnetic composite liquid in step 3 to the liquid tank, and assemble the equipment from bottom to top in the order of leveling platform, magnetic array, and liquid tank. The bottom thickness of the liquid tank is 1 mm, and two 0.5 mm glass sheets are inserted to control the distance between the liquid and the magnetic array to be 2 mm.

[0045] Step 7: Place the entire device in a ventilated place to dry for a certain period of time, wait for the organic solvent to completely evaporate, and then take out the remaining film from the liquid tank.

[0046] Example 2

[0047] The patent discloses a method for preparing a flexible electromagnetic wave absorbing film controlled by a magnet array, comprising the following steps:

[0048] Step 1: Mix 120 g of an electromagnetic wave absorbing powder prepared by mixing 5 g of silicon dioxide and 5 g of carbon nanotubes with 100 g of a thermoplastic elastomer TPU, and disperse the mixture in 500 mL of dimethyl sulfoxide.

[0049] Step 2: Stirring continuously at 80° C. for 4 hours to completely dissolve the thermoplastic elastomer TPU in the cyclohexanone, and stirring continuously to fully disperse the absorber in the thermoplastic elastomer solution.

[0050] Step 3, the mixed solution in step 2 is continuously stirred and naturally cooled to room temperature to obtain a magnetic composite liquid.

[0051] Step 4, select a spherical magnet with a diameter of 6mm, use 3D printing technology to print a spherical slot grid, the slot diameter is 6mm, the interval between the magnets is 1.0mm, the length and width of the mold contain 30 magnet units, and the length and width are 195mm respectively. According to the size of the mold, select 195x195 mm 2 Liquid tank and leveling platform.

[0052] Step 5: Alternately arrange the NS poles of the magnets along the long side direction and keep the polarity consistent along the wide side direction. Use COMSOL to simulate the magnetic field distribution generated by the magnet array and embed the actual magnets into the magnet array mold.

[0053] Step 6: Transfer the magnetic composite liquid in step 3 to the liquid tank, and assemble the device from bottom to top in the order of leveling platform, magnetic array, and liquid tank. The bottom thickness of the liquid tank is 0.5 mm, and the distance between the liquid and the magnetic array is controlled to be 0.5 mm.

[0054] Step 7: Place the entire device in a ventilated place to dry for a certain period of time, wait for the organic solvent to completely evaporate, and then take out the remaining film from the liquid tank.

[0055] Example 3

[0056] The patent discloses a method for preparing a flexible electromagnetic wave absorbing film controlled by a magnet array, comprising the following steps:

[0057] Step 1: Mix electromagnetic wave absorbing powder prepared by mixing 2 g of carbonyl iron powder and 0 g of carbon fiber with 200 g of thermoplastic elastomer TPE, and disperse the mixture in 1000 mL of cyclohexane.

[0058] Step 2: Stirring continuously at 80° C. for 2 h to completely dissolve the thermoplastic elastomer TPE in cyclohexane, and stirring continuously to fully disperse the absorber in the thermoplastic elastomer solution.

[0059] Step 3, the mixed solution in step 2 is continuously stirred and naturally cooled to room temperature to obtain a magnetic composite liquid.

[0060] Step 4, select the size of 5x5x5 mm 3 Square magnets, printed using 3D printing technology, with a grid size of 5x5mm 2, a grid magnet array mold with a height of 5mm and a wall thickness of 0.5mm. The mold contains 80 magnet units in length and width, and the length and width are 440mm respectively. According to the size of the mold, 440x440mm is selected 2 Liquid tank and leveling platform.

[0061] Step 5: Alternately arrange the NS poles of the magnets along the length and width directions, simulate the magnetic field distribution generated by the magnet array through COMSOL, and embed the actual magnets into the magnet array mold.

[0062] Step 6: Transfer the magnetic composite liquid in step 3 to the liquid tank, and assemble the equipment from bottom to top in the order of leveling platform, magnetic array, and liquid tank. The bottom thickness of the liquid tank is 1 mm, and two 0.5 mm glass sheets are inserted to control the distance between the liquid and the magnetic array to be 2 mm.

[0063] Step 7: Place the entire device in a ventilated place to dry for a certain period of time, wait for the organic solvent to completely evaporate, and then take out the remaining film from the liquid tank.

[0064] Example 4

[0065] The patent discloses a method for preparing a flexible electromagnetic wave absorbing film controlled by a magnet array, comprising the following steps:

[0066] Step 1: Mix the electromagnetic wave absorbing powder (wave absorber) with magnetic properties and the thermoplastic elastomer, and disperse them in a certain amount of organic solvent.

[0067] Step 2: Stirring continuously for a certain period of time at a certain temperature until the thermoplastic elastomer is dissolved in the organic solvent and the absorber is fully dispersed in the thermoplastic elastomer solution.

[0068] Step 3, the mixed solution in step 2 is continuously stirred and naturally cooled to room temperature to obtain a magnetic composite liquid.

[0069] Step 4: Select appropriate magnets, use 3D printing technology to print the magnet array mold, and select the appropriate size of the liquid tank and leveling platform according to the size and shape of the mold.

[0070] Step 5: According to the magnet arrangement design, the magnetic field distribution generated by the magnet array is simulated by COMSOL, and the actual magnets are embedded in the magnet array mold.

[0071] Step 6, transfer the magnetic composite liquid in step 3 to the liquid tank, and assemble the device from bottom to top in the order of leveling platform, magnetic array, and liquid tank.

[0072] Step 7: Place the entire device in a ventilated place to dry for a certain period of time, wait for the organic solvent to completely evaporate, and then take out the remaining film from the liquid tank.

[0073] Wherein, the absorbent in step 1 should be able to be attracted by a magnet.

[0074] The operation in step 2 should ensure that the thermoplastic elastomer is completely dissolved and the absorber is completely dispersed.

[0075] Wherein, the magnetic composite liquid in step 3 should be kept at room temperature to avoid solvent volatilization.

[0076] Among them, the mold, liquid tank, leveling platform and magnet described in step 4 should be selected in groups, the leveling platform ensures the liquid level, the magnet provides the magnetic field, the mold fixes the magnet to build a stable magnetic field, the liquid tank holds the magnetic composite liquid and controls the distance between it and the magnet array.

[0077] Among them, the COMSOL simulation described in step 5 should correspond to the actual magnet arrangement.

[0078] The assembly sequence in step 6 is to avoid liquid shaking and ensure uniform film formation.

[0079] The drying in step 7 should ensure that the organic solvent is completely volatilized, and the film can be peeled off by physical means.

[0080] Comparative Example 1

[0081] The electromagnetic wave absorbing film prepared in Comparative Example 1 was not controlled by the magnet array, and the rest was the same as in Example 1.

[0082] Comparative Example 1 has an absorption peak at 16 GHz, and it is difficult for the film to achieve differentiation in different polarization directions and variability in electromagnetic wave absorption performance.

[0083] The electromagnetic wave absorption film prepared by magnet array control can achieve more excellent electromagnetic wave absorption performance. For the spaced magnetic array, the prepared film has relatively excellent electromagnetic wave absorption performance. The film constructed by the striped magnetic array can achieve the maximum effective absorption peak from -14.54dB to -19.25dB as it rotates, and the maximum effective absorption bandwidth is enhanced from 5.05Ghz to 5.6GHz.

[0084] 120g of carbonyl iron powder and 2.5g of carbon fiber were mixed with 100g of thermoplastic elastomer TPE and dispersed in 500mL of cyclohexane. Stirring was continued at 80℃ for 2h to make TPE completely dissolved in cyclohexane. Stirring was continued to make the absorber fully dispersed in the thermoplastic elastomer solution, and then cooled naturally to room temperature to obtain a magnetic composite liquid. Based on the above, a 5x5x5mm 3 A square magnet with the N and S poles represented by black and white. Figure 2Two possible magnet array arrangements are shown. One is to arrange the NS poles alternately along the long side and along the wide side squares. The other is to arrange the NS poles alternately along the long side and keep the same polarity along the wide side squares. In order to visualize the magnetic field generated by the magnet arrangement, the magnetic field above the magnet is simulated by COMSOL simulation. Figure 3 As shown in the figure, due to the change in the NS pole arrangement, the magnetic field distribution formed above is also controlled. Based on the above magnet array arrangement design, a 3D printing technology is used to print a grid size of 5x5 mm. 2 , a grid magnet array mold with a height of 5mm and a wall thickness of 0.5mm. Figure 4 As shown, the mold contains 40 magnet units, and the length and width are 220 mm respectively. According to the size of the mold, 200x200 mm is selected. 2 Liquid tank and leveling platform. Use glass to prepare a liquid tank with a wall thickness of 0.5 mm, and control the distance between the liquid tank and the magnet array to be 2 mm. Place the prepared magnetic composite liquid, the selected liquid tank, the magnet array, and the magnet array leveling platform. Figure 5 As shown, the equipment is built from bottom to top, and the whole set of equipment is placed in a ventilated place to dry for a certain period of time. After the organic solvent is completely evaporated, the remaining film is taken out from the liquid tank. An optical microscope is used to observe the particles inside the flexible electromagnetic wave absorbing film prepared by this method. By removing the carbon fiber, the regular arrangement of the magnetic particles is effectively observed under an optical microscope. Figure 3 (left) is consistent with the arrangement. Figure 3 As shown in (right), at the same magnification, the film prepared by the magnet array has a more orderly particle arrangement. Figure 7 As shown in the figure, the surface structure of the flexible electromagnetic wave absorbing film without magnetic field is consistent with the internal magnetic particle distribution, which also verifies Figure 3 Validity of simulated magnetic field distribution.

[0085] The electromagnetic wave absorption performance of the prepared film was tested using the arch method. Figure 8 a), the obtained film has excellent electromagnetic wave absorption performance, for the striped magnetic array ( Figure 8bc), the performance is different before and after rotating 90°. When the vertical film stripes with magnetic field polarization are changed to vertical film stripes with electric field polarization, the maximum effective absorption peak is enhanced from -14.54dB to -19.25dB, and the maximum effective absorption bandwidth is enhanced from 5.05Ghz to 5.6GHz. With another rotation of 90 degrees, the performance of the two can be converted. On the one hand, the electromagnetic wave absorbing flexible film controlled by the magnet array can achieve different responses to electromagnetic waves in different directions, that is, the anisotropy of the wave absorbing performance. On the other hand, the magnetism of the film is improved due to the presence of the magnetic array, achieving better electromagnetic wave absorption performance. Therefore, the external magnetic field constructed by the magnet array helps to improve the electromagnetic wave absorption performance for the structural control of the magnetic particles inside the film.

[0086] The mechanical properties of the film made of strip-shaped magnetic array were tested using a tensile testing machine. Fig. 9 (Left) Stripes along the vertical direction, Fig. 9 (Right) The stripes are along the horizontal direction. There are significant differences in the elongation and maximum tension of the two, mainly due to the different arrangement and orientation of the internal magnetic particles. Therefore, for the method for preparing a flexible film for electromagnetic wave absorption controlled by a magnet array proposed in this patent, it is possible to effectively combine computer simulation with design to achieve magnetic field control and intuitively display the control results of the external magnetic field. Conventional film preparation methods are designed and improved to achieve adaptation to external magnetic field control. Using thermoplastic elastomer as the matrix, a thin film material with a structural design is designed to solve the problem of difficulty in bending or stretching, and to achieve high-performance electromagnetic wave absorption.

[0087] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0088] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for simulating the magnetic field distribution generated by a magnet array, characterized in that: The following steps are involved: The steady-state magnetic field solution simulation of the magnet array is carried out through the software's current-free magnetic field physics field; The model’s boundary is set as a magnetically insulated cuboid; The initial value of the magnetic scalar potential inside the boundary is set, and the magnetic flux is kept conserved; A matrix of small cubes is placed in an array within the boundary, and the cube size refers to the actual magnet size; The material inside the boundary is set to air, and the small cube matrix is ​​set to the actual magnet parameters; Execute the simulation to get the final simulated magnetic field distribution map.

2. A method for preparing an electromagnetic wave absorbing film controlled by a magnet array, characterized in that: The following steps are involved: The electromagnetic wave absorbing powder is mixed with the thermoplastic elastomer, dispersed in an organic solvent, stirred until the thermoplastic elastomer is dissolved in the organic solvent and the electromagnetic wave absorbing powder is dispersed in the thermoplastic elastomer solution, and stirred and cooled continuously to obtain a magnetic composite liquid; Print the magnet array mold, and select the liquid tank and leveling platform according to the magnet array mold; According to the magnet arrangement design, the actual magnets are embedded in the magnet array mold through the simulated magnetic field distribution diagram described in claim 1; The magnetic composite liquid is transferred to a liquid tank, dried by ventilation, and the organic solvent is evaporated to obtain an electromagnetic wave absorbing film controlled by a magnet array.

3. The method for preparing an electromagnetic wave absorbing film controlled by a magnet array according to claim 1, characterized in that: The electromagnetic wave absorbing powder includes one or more of iron, cobalt and nickel.

4. The method for preparing an electromagnetic wave absorbing film controlled by a magnet array according to claim 1, characterized in that: The electromagnetic wave absorbing powder includes one or more of TPE, TPU, TPO and TPS.

5. The method for preparing an electromagnetic wave absorbing film controlled by a magnet array according to claim 1, characterized in that: The mass ratio of the thermoplastic elastomer to the electromagnetic wave absorbing powder is 1:0.01-1:

2.

6. The method for preparing an electromagnetic wave absorbing film controlled by a magnet array according to claim 1, characterized in that: The dispersion method of the electromagnetic wave absorbing powder into the thermoplastic elastomer solution includes one or more of ultrasonic dispersion, physical stirring and microwave digestion.

7. The method for preparing an electromagnetic wave absorbing film controlled by a magnet array according to claim 1, characterized in that: The shape of the magnet array mold includes any one of spherical, rectangular and spindle shapes.

8. The method for preparing an electromagnetic wave absorbing film controlled by a magnet array according to claim 1, characterized in that: The material of the liquid tank includes any one of glass and polytetrafluoroethylene.

9. An electromagnetic wave absorbing film controlled by a magnet array obtained by the preparation method according to claim 1 or any one of claims 3 to 8.

10. The method for simulating magnetic field distribution generated by a magnet array according to claim 2, characterized in that: The initial value of the magnetic scalar potential inside the boundary is set to 0 V / m.

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