CN115260988A - Composite wave-absorbing material and preparation method thereof - Google Patents
Composite wave-absorbing material and preparation method thereof Download PDFInfo
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- CN115260988A CN115260988A CN202210975882.8A CN202210975882A CN115260988A CN 115260988 A CN115260988 A CN 115260988A CN 202210975882 A CN202210975882 A CN 202210975882A CN 115260988 A CN115260988 A CN 115260988A
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Abstract
The invention discloses a composite wave-absorbing material and a preparation method thereof, wherein the composite wave-absorbing material comprises a resistive film dielectric slab and a wave-absorbing material positioned on the resistive film dielectric slab; the wave-absorbing material is a plurality of truncated cone structures arranged in a matrix form, and the diameters of the truncated cone structures are in continuous gradient change; the resistive film dielectric slab comprises a dielectric substrate and a resistive film attached to the dielectric substrate, and the wave-absorbing material is attached to one side, covered with the resistive film, of the resistive film dielectric slab. When electromagnetic waves are emitted, the composite wave-absorbing material realizes high electromagnetic wave absorption rate of the composite wave-absorbing material at 2-18 GHz (S, C, X, ku wave band) through absorption of the wave-absorbing material with the cone frustum structure arranged in a matrix form and interference resonance absorption of the electromagnetic film dielectric plate, and the reflection loss of the composite wave-absorbing material can reach below-15 dB under the bandwidth of 2-18 GHz.
Description
Technical Field
The invention relates to a wave-absorbing material, in particular to a composite wave-absorbing material and a preparation method thereof.
Background
In order to reduce electromagnetic pollution, more and more wave-absorbing materials are developed and applied, and two conditions of electromagnetic wave absorption are impedance matching and attenuation absorption respectively, wherein the impedance matching can ensure that the electromagnetic waves are efficiently incident into the wave-absorbing body, the attenuation absorption can ensure that the electromagnetic waves incident into the wave-absorbing body are lost, the impedance matching cannot ensure that the electromagnetic waves are not used for the attenuation absorption, and the graphite powder can provide efficient conductive loss due to excellent conductivity and is widely applied to the wave-absorbing materials;
huang et al, which extracts the micrometer structure of the compound eye of moth and combines carbonyl iron powder and polyurethane raw material to make the absorbing film, can achieve-10 dB absorption at 8.04-17.88 GHz (Huang L.X.; duan Y.P.; dai X.H.; zeng Y.S.; ma G.J.; liu Y.; gao S.H.; zhang W.P.; bioinspired metals: multibands Electron Electromagnetic Wave adaptive and Hydrophotic Characteristics, small 15 (2019) 1902730), but most of these applications are concentrated in the narrow absorption band of visible light and infrared Wave Duan Ju, and at the same time, after the incidence of Electromagnetic Wave, the absorbing material can still partially absorb the microwave, resulting in low absorption rate of the Electromagnetic Wave.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide a composite wave-absorbing material with wide frequency band absorption and high absorption rate, and a preparation method of the composite wave-absorbing material.
The technical scheme is as follows: the composite wave-absorbing material comprises a resistive film dielectric slab and a wave-absorbing material positioned on the resistive film dielectric slab; the wave-absorbing material is a plurality of truncated cone structures arranged in a matrix form, and the diameters of the truncated cone structures are in continuous gradient change; the resistive film dielectric slab comprises a dielectric substrate and a resistive film attached to the dielectric substrate, and the wave-absorbing material is attached to one side, covered with the resistive film, of the resistive film dielectric slab.
Furthermore, the height of each cone frustum structure is 15-20 mm, the radius of the upper bottom surface is 1.5-3.5 mm, and the radius of the lower bottom surface is 5.5-7.5 mm, in the cone frustum structures arranged in a matrix manner, the number of rows of the matrix is not less than 20, the number of columns of the matrix is not less than 20, and the horizontal distance between the central axes of the adjacent cone frustum structures is 11-15 mm.
The diameter of the truncated cone structure is changed in a continuous gradient manner along the longitudinal direction, so that when electromagnetic waves are incident, the electromagnetic waves can be incident into the wave-absorbing material as much as possible instead of being reflected, the electromagnetic waves which do not enter the wave-absorbing material are reflected by the densely arranged truncated cone structure to form reflection loss, a good impedance matching effect is formed, and the wave-absorbing material with the truncated cone structure arranged in a matrix manner can efficiently absorb the electromagnetic waves.
Furthermore, in the resistive film dielectric plate, the resistance value of the resistive film is 145-155 omega, the dielectric constant of the dielectric substrate is 1-1.1, the thickness of the dielectric substrate is 3-5 mm, the sizes of the resistive film and the dielectric substrate are consistent, and the size of the dielectric substrate is larger than that of the wave-absorbing material with the cone frustum structure in the matrix arrangement.
The wave absorption principle of the resistive film dielectric slab is thickness interference absorption, when the first interference absorption occurs, the thickness of the resistive film dielectric slab is 1/4 of the effective wavelength, and when the thickness of the resistive film dielectric slab is 1/2 of the effective wavelength, the resistive film dielectric slab can generate strong reflection, the thickness of the resistive film is ignored, so the thickness of the dielectric substrate is not suitable to be too large; although the dielectric constant of the dielectric substrate can be increased to reduce the thickness of the resistive film dielectric plate, the absorption bandwidth is also reduced, so the dielectric constant of the dielectric substrate is not suitable to be too large.
Further, the wave-absorbing material with the cone frustum structure comprises the following components in parts by mass: 20-30 parts of conductive graphite powder and 60-90 parts of epoxy resin adhesive; the epoxy resin adhesive is used as a filling base material, and a cone frustum structure with a smooth surface is finally obtained. The resistive film in the resistive film dielectric slab is an indium tin oxide film, and the dielectric slab is foamed polypropylene.
The preparation method of the composite wave-absorbing material comprises the following steps:
(1) Obtaining structural parameters of the wave-absorbing material with the cone frustum structure through simulation design, performing modeling printing by using the structural parameters, and obtaining a silica gel mold after using silica gel to turn over the mold;
(2) Mixing conductive graphite powder with epoxy resin glue to obtain a mixture, pouring the mixture into a silica gel mold, curing and demolding at normal temperature, and demolding after curing to obtain the wave-absorbing material with the truncated cone structure arranged in a matrix form;
(3) And attaching the resistive film dielectric plate to the lower bottom surface of the wave-absorbing material, wherein the wave-absorbing material is positioned on one side of the resistive film dielectric plate covered with the resistive film, so as to obtain the composite wave-absorbing material.
The composite wave-absorbing material consists of a cone frustum structure wave-absorbing material and a resistive film dielectric slab, wherein after electromagnetic waves are incident from the upper part, part of the electromagnetic waves are attenuated and absorbed through multiple surface reflections, part of the electromagnetic waves enter the wave-absorbing material, microwaves still penetrate the wave-absorbing material after internal impedance matching and absorption, the microwave frequency of the part is lower, the resistive film dielectric slab can absorb the microwaves through interference resonance, and the absorption bandwidth of the composite wave-absorbing material is widened through the combined action of the wave-absorbing material with the cone frustum structure and the bottom resistive film dielectric slab.
Has the beneficial effects that: compared with the prior art, the invention has the remarkable advantages that: when electromagnetic waves are emitted, the composite wave-absorbing material realizes high electromagnetic wave absorption rate of the composite wave-absorbing material at 2-18 GHz (S, C, X, ku wave band) through absorption of the wave-absorbing material with the cone frustum structure arranged in a matrix form and interference resonance absorption of the electromagnetic film dielectric plate, and the reflection loss of the composite wave-absorbing material can reach below-15 dB under the bandwidth of 2-18 GHz.
Drawings
FIG. 1 shows the basic electromagnetic parameters of the simulation of example 1;
FIG. 2 is a simulation model of the wave-absorbing material with a truncated cone structure in example 1;
FIG. 3 is a structural view of a resistive film dielectric slab;
FIG. 4 is a physical diagram of the composite wave-absorbing material in example 1;
FIG. 5 is a reflection loss chart of the wave-absorbing material of example 1;
FIG. 6 is a reflection loss chart of the wave-absorbing material in comparative example 1;
FIG. 7 shows the wave-absorbing of comparative example 2 reflection loss plot of material.
Detailed Description
Example 1
The preparation method of the composite wave-absorbing material comprises the following steps:
(1) Simulation design: mixing 25 parts by mass of conductive graphite powder and 75 parts by mass of paraffin, measuring electromagnetic parameters of the conductive graphite powder by a coaxial method, and introducing the electromagnetic parameters into simulation software for design to obtain structural parameters of the wave-absorbing material with the cone frustum structure arranged in a matrix form: the height h =17mm of each conical frustum structure, the radius phi 1 of the upper bottom surface is =3.5mm, the radius phi 2 of the lower bottom surface is phi 2=7.5mm, the number of rows of the matrix is 20, the number of columns is 20, the integral length of the wave-absorbing material is 300mm, and the integral width is 300mm;
(2) Preparing a mould: manufacturing a truncated cone structure in simulation software by using 3D printing, and turning over a silica gel mold to obtain a silica gel mold;
(3) Preparing a wave-absorbing material: adding 25 parts by mass of conductive graphite powder into 75 parts by mass of epoxy resin adhesive, uniformly stirring at 28 ℃, pouring into a silica gel mold, vibrating out air, drying at 80 ℃, curing and demolding to obtain the wave-absorbing material with the cone frustum structure arranged in a matrix form;
(4) And attaching an indium tin oxide resistive film with the resistance value of 150 omega to a foamed polypropylene dielectric substrate with the thickness of 5mm to obtain a resistive film dielectric plate, wherein the resistive film is the same as the dielectric substrate in size, the length of the resistive film dielectric plate is 350mm, and the width of the resistive film dielectric plate is 350mm, and attaching the wave-absorbing material to one side, covered with the resistive film, of the resistive film dielectric plate to obtain the composite wave-absorbing material.
Comparative example 1
The comparative example 1 is a wave-absorbing material in a flat plate structure, the length of the wave-absorbing material is 300mm, the width of the wave-absorbing material is 300mm, the thickness of the wave-absorbing material is 15mm, and the composition and the preparation method of the wave-absorbing material are the same as those in the step (3) of the example 1.
Comparative example 2
The only difference between the comparative example 2 and the example 1 is that the comparative example 2 is the wave absorbing material with the cone frustum structure arranged in a matrix without the resistive film dielectric slab, that is, the step (4) in the example 1 is not included, and the rest preparation methods are completely the same as those in the example 1.
FIG. 1 shows the electromagnetic parameters of the conductive graphite powder and paraffin mixture of example 1, and it can be seen from FIG. 1 that, in the frequency range of 2-18 GHz, the real dielectric part of the composite varies in the range of 8-12 GHz, the imaginary dielectric part is between 3-6, and both gradually decrease with the increase of frequency, which indicates that the composite is of conductivity and dielectric loss type, and the dielectric loss is about 0.3, which indicates that the composite is suitable for being used as an absorbent of wave-absorbing materials.
FIG. 2 is a region of the change in the size of the periodic structure unit of the frustum simulation model of example 1, and it can be seen from FIG. 2 that the height h = 15-20 mm of the truncated cone has a radius of the upper baseФ 1 = 1.5-3.5 mm, radius of lower bottom surface phi 2 And the wave absorbing performance is best when the thickness is 5.5-7.5 mm.
FIG. 5 is a test chart of the wave-absorbing performance of the wave-absorbing material prepared in example 1, and it can be seen from FIG. 5 that within 2-18 GHz, the bandwidth of electromagnetic wave absorption reaching-15 dB is 16GHz, which realizes the effect of broadband absorption, and the wave-absorbing material has three resonance peaks in total at low, medium and high frequencies, which is seen as the common action of various loss mechanisms and embodies the results of the common action of the structure and the material and the microwave absorption.
FIG. 6 is a reflection loss graph of the wave-absorbing material with the plate structure in the comparative example 1, and as can be seen from FIG. 6, the reflection loss of the wave-absorbing material in the comparative example 1 in the electromagnetic wave frequency band of 2-18 GHz is less than that of the wave-absorbing material in the example 1, so that the wave-absorbing performance of the wave-absorbing material with the plate structure is poor compared with that of the wave-absorbing material with the cone frustum structure.
FIG. 7 is a reflection loss diagram of the wave-absorbing material with a truncated cone structure in comparative example 2 without the added resistive film dielectric slab, and it can be seen that the low-frequency band (2-6 GHz range) microwave absorption performance is obviously inferior to that of the composite wave-absorbing material with the added resistive film dielectric slab.
Claims (8)
1. A composite wave-absorbing material is characterized in that: the wave-absorbing material comprises a resistive film dielectric slab and a wave-absorbing material positioned on the resistive film dielectric slab; the wave-absorbing material is a plurality of truncated cone structures arranged in a matrix form, and the diameters of the truncated cone structures are in continuous gradient change; the resistive film dielectric plate comprises a dielectric substrate and a resistive film attached to the dielectric substrate, and the wave absorbing material is attached to one side, covered with the resistive film, of the resistive film dielectric plate.
2. The composite wave-absorbing material of claim 1, wherein: the height of each cone frustum structure is 15-20 mm, the radius of the upper bottom surface is 1.5-3.5 mm, and the radius of the lower bottom surface is 5.5-7.5 mm.
3. The composite wave-absorbing material of claim 1, wherein: in the cone frustum structure arranged in a matrix manner, the number of rows of the matrix is not less than 20, and the number of columns of the matrix is not less than 20.
4. The composite wave-absorbing material of claim 1, wherein: the horizontal distance between the central axes of the adjacent cone frustum structures is 11-15 mm.
5. The composite wave-absorbing material of claim 1, wherein: in the resistance film dielectric plate, the resistance value of the resistance film is 145-155 omega, the thickness of the dielectric substrate is 3-5 mm, and the dielectric constant of the dielectric substrate is 1-1.1.
6. The preparation method of the composite wave-absorbing material of any one of claims 1 to 5, which is characterized by comprising the following steps:
(1) Obtaining structural parameters of the wave-absorbing material with the cone frustum structure through simulation design, performing modeling printing by using the structural parameters, and obtaining a silica gel mold after using silica gel to turn over the mold;
(2) Mixing conductive graphite powder with epoxy resin glue to obtain a mixture, pouring the mixture into a silica gel mold, curing and demolding at normal temperature to obtain the wave-absorbing material with the cone frustum structure in matrix arrangement;
(3) And (3) attaching the resistive film dielectric plate to the lower bottom surface of the wave-absorbing material, wherein the wave-absorbing material is positioned on one side of the resistive film dielectric plate covered with the resistive film, and obtaining the composite wave-absorbing material after the attachment is completed.
7. The preparation method of the composite wave-absorbing material according to claim 6, characterized in that: the size of the resistive film is consistent with that of the medium substrate, and the size of the medium substrate is larger than that of the wave-absorbing material.
8. The preparation method of the composite wave-absorbing material according to claim 6, characterized in that: the mixing mass ratio of the conductive graphite powder to the epoxy resin adhesive is 1:3 to 1:5.
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