CN115674819B - Broadband wave-absorbing material and preparation method thereof - Google Patents
Broadband wave-absorbing material and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a broadband wave-absorbing material and a preparation method thereof, wherein the broadband wave-absorbing material comprises a reflecting layer and an absorbing layer, the number of the absorbing layer is at least two, and two or more than two absorbing layers are sequentially overlapped on one side of the reflecting layer; the absorption layer comprises a foam core material layer and a resistance film layer, wherein the foam core material layer is connected with the reflection layer, and the sheet resistance of the resistance film layer is sequentially increased along the direction away from the reflection layer. The broadband wave absorbing material prepared by the invention has the characteristics of broadband absorption and high-efficiency absorption, can realize electromagnetic wave absorption in X (8-12 GHz) wave band and Ku (12-18 GHz) wave band respectively, realizes that the electromagnetic wave absorption rate of full frequency band is higher than 95% under vertical polarization and horizontal polarization, can be widely applied to stealth parts of military equipment, and has wide application scenes.
Description
Technical Field
The invention belongs to the technical field of wave-absorbing materials, and particularly relates to a broadband wave-absorbing material and a preparation method thereof.
Background
With the development of modern radar detection technology, the radar system can realize broadband coverage on a detected target, and the demand for broadband structure wave-absorbing composite materials is also more and more urgent. To achieve excellent wave absorbing performance, the radar absorbing material must satisfy two conditions simultaneously: firstly, the surface impedance of the wave-absorbing material is matched with the free space wave impedance so as to ensure that electromagnetic waves enter the material; secondly, the interior of the wave-absorbing material needs to have electrical or magnetic loss so as to dissipate electromagnetic energy entering the interior of the wave-absorbing material.
The conventional wave-absorbing structure is mostly based on a Salisbury absorbing screen, a Jaumman absorber and a multi-layer impedance matching wave-absorbing material, and typical problems are large thickness and narrow absorption band. The main method for expanding the absorption band is to increase the thickness or increase the content of the absorbent, but the absorption band is hardly realized by the electromagnetic parameter dispersion characteristic of the material or the resonance electric thickness. The advent and development of metamaterials have enabled people to control the electromagnetic properties of materials from a macroscopic scale, thereby significantly affecting the interaction relationship between the materials and electromagnetic waves, and their application in electromagnetic wave absorbing technology has become a popular research direction. Compared with the traditional wave-absorbing material, the dependence of the broadband wave-absorbing performance on the intrinsic electromagnetic parameter dispersion characteristic of the material can be eliminated, but the metamaterial realizes single-frequency or multi-frequency absorption of electromagnetic waves based on electromagnetic resonance, and certain difficulty still exists in the aim of realizing broadband absorption.
Disclosure of Invention
In order to solve the technical problems of heavy wave-absorbing material and narrow absorption frequency band in the prior art, the invention provides the broadband wave-absorbing material and the preparation method thereof, and the prepared wave-absorbing material has the characteristics of thin thickness and broadband absorption, realizes the characteristic of high-efficiency absorption in the working frequency band, can be widely applied to stealth parts of military equipment, and has wide application prospect.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
the first aspect of the present invention provides a broadband wave absorbing material, which includes a reflective layer and an absorbing layer, where the absorbing layer is at least two layers, and two or more absorbing layers are sequentially stacked on one side of the reflective layer.
The absorption layer comprises a foam core material layer and a resistance film layer, wherein the foam core material layer is connected with the reflection layer, and the sheet resistance of the resistance film layer is sequentially increased along the direction away from the reflection layer.
The thickness of the foam core material layer is 2.5 mm-3.5 mm.
The absorption layers in the wave-absorbing material are alternately overlapped with the foam core material layers and the resistance film layers, and the wave-absorbing material has the effects of realizing the matching of the surface impedance of the wave-absorbing material and the free space wave impedance by utilizing the resistance film layers, changing the scattering property of electromagnetic waves, ensuring the electromagnetic waves to enter and simultaneously carrying out electric loss and dissipating the entered electromagnetic energy. The foam core material layer is arranged to mainly play roles in supporting the whole structure, wave transmission and matching. The absorption layer is provided with two or more layers, the resistance film layer of the surface layer is firstly utilized to directly absorb loss for the first time, the rest electromagnetic waves are further absorbed through the lower resistance film layer, and finally the reflection plate is utilized to absorb the electromagnetic waves which are not lost through the resistance film layer again, so that the effect of high-efficiency absorption is achieved. And the resistor film layers with different sheet resistances are arranged and used for absorbing electromagnetic waves with different frequency bands so as to achieve the effect of broadband absorption. The sheet resistance of the resistance film layer is sequentially increased from the reflecting layer to the direction far away from the reflecting layer, namely, after the electromagnetic wave enters, the electromagnetic wave passes through the resistance film layer with large sheet resistance, and is mainly absorbed by the electromagnetic wave in the Ku wave band, and then the electromagnetic wave in the X wave band is absorbed by the resistance film layer with small sheet resistance.
As an optional implementation manner, in the broadband wave absorbing material provided by the invention, when the absorbing layer is two layers, the second layer is increased by 442% to 967% based on the sheet resistance of the first layer; when the absorption layer is three layers, the second layer is increased by 80% to 300% based on the first layer sheet resistance value, and the third layer is increased by 116% to 250% based on the second layer sheet resistance value; when the absorption layer is four layers, the second layer is increased by 25% to 233% on the basis of the first layer sheet resistance, the third layer sheet resistance is increased by 40% to 183% on the basis of the second layer, and the fourth layer sheet resistance is increased by 53% to 128% on the basis of the third layer.
In an alternative embodiment, the broadband wave absorbing material provided by the invention, the resistive film layer comprises a substrate layer and an ink layer, wherein the substrate layer is connected with the foam core layer in a single absorption layer, and the ink layer is attached to the substrate layer.
The ink layer is used for absorbing and losing electromagnetic waves, and the substrate layer is used for attaching the ink layer.
In an alternative embodiment, the material of the substrate layer in the broadband wave absorbing material provided by the invention is FR4.
In an optional implementation manner, in the broadband wave absorbing material provided by the invention, the ink layer is provided with the periodic cross-shaped gap, the gap width W is 0.4-0.6 mm, and the unit period R of the periodic cross-shaped gap is 7.5-8.5 mm.
The periodic cross-shaped gaps are formed in the ink layer, and the periodic cross-shaped gaps are a plurality of periodic arranged cross-shaped patterns, namely, when the ink layer is prepared on the substrate, the cross-shaped patterns are not provided with the ink layer, and are exposed substrates. By setting the cross-shaped gap with a specific width and a specific period, the original equivalent circuit is changed, the capacitance is increased, the scattering property of electromagnetic waves is changed, the wave transmission effect is realized, the electromagnetic waves which are not absorbed are absorbed by utilizing the next resistance film layer after being transmitted, or the electromagnetic waves are absorbed after being reflected by the reflecting layer, so that the broadband absorption of the electromagnetic waves is realized.
The periodic cross-shaped slits referred to in this application are not limited to the standard cross shape, and parting structures derived from the cross shape are also included in the scope of this application.
In an optional embodiment, in the broadband wave absorbing material provided by the invention, the thickness of the substrate layer is 0.05 mm-0.1 mm, the thickness of the ink layer is 0.015 mm-0.025 mm, and the thickness of the wave absorbing material is 6.5 mm-16.5 mm.
The single-layer rear degree of each part is limited in the range, compared with the conventional wave-absorbing material, the rear degree of the broadband wave-absorbing material prepared by combining the single-layer rear degree is greatly reduced, the thickness is reduced, meanwhile, the multi-layer absorption is adopted, the electromagnetic wave is enabled to enter from the large to the small direction according to the resistance value of the resistance film layer, and the broadband absorption can be realized after the reduction.
In the broadband wave-absorbing material provided by the invention, when the number of the absorbing layers is two, the square resistance values of the resistive film layers are 150-240 Ω/≡and 1300-1600 Ω/≡respectively; when the absorption layer is three layers, the square resistance values of the resistance film layer are 150-240 Ω/≡s, 450-600 Ω/≡s and 1300-1600 Ω/≡s respectively; when the absorption layer is four layers, the sheet resistance values of the resistance film layers are 150-240 Ω/≡o, 300-500 Ω/≡o, 700-850 Ω/≡o and 1300-1600 Ω/≡o respectively.
In the invention, when the absorption layers are arranged as two layers, the resistance value is 1300-1600 omega/≡and mainly aims at the Ku wave band, and the resistance value is 150-240 omega/≡and mainly aims at the X wave band; 1300-1600 Ω/≡o for 10-18GHz,450-600 Ω/≡o for 10-14GHz,150-240 Ω/≡o for 8-10GHz; at four layers 1300-1600 Ω/∈s for 15-18GHz,700-850 Ω/∈s for 12-15GHz,300-500 Ω/∈s for 10-12GHz,150-240 Ω/∈s for 8-10GHz.
As an optional implementation mode, in the broadband wave absorbing material provided by the invention, the density of the foam core material layer is 75-110 kg/m 3 。
As an optional implementation mode, in the broadband wave-absorbing material provided by the invention, a wave-absorbing frequency band of the wave-absorbing material comprises 8-18 GHz.
As an alternative embodiment, the broadband wave absorbing material provided by the invention has the reflectivity of less than-25 dB in an X wave band and a Ku wave band.
The density of the foam core material is limited to 75-110 kg/m 3 Thus, the characteristic of light weight of the wave-absorbing material is realized.
As an optional implementation mode, in the broadband wave-absorbing material provided by the invention, the surface density of the broadband wave-absorbing material is 1.25-2.72 kg/m 2 。
When the absorbent layer is two layers in the present invention, a density of 75kg/m of 2.5mm is used 3 When the foam core material is used, the surface density of the prepared wave-absorbing material is 1.25kg/m 2 The method comprises the steps of carrying out a first treatment on the surface of the When the absorbent layer is four layers, a density of 110kg/m at 3.5mm is used 3 When the foam core material is used, the surface density of the prepared wave-absorbing material is 2.72kg/m 2 。
In an optional embodiment, in the broadband wave absorbing material provided by the invention, the foam core material layer is PMI foam.
In an alternative embodiment, in the broadband wave absorbing material provided by the invention, the reflecting layer is a metal plate, and the thickness of the metal plate is 0.05-0.15mm.
In an alternative embodiment, in the broadband wave absorbing material provided by the invention, the reflecting layer is an aluminum alloy plate or an aluminum plate.
The second aspect of the present invention provides a method for preparing the broadband wave absorbing material, comprising the steps of:
s1, preparing a resistance film layer: mixing high-resistance carbon paste ink with the resistance of 12000-15000 omega/∈and low-resistance carbon paste ink with the resistance of 30-40 omega/∈s to prepare carbon paste ink with different resistance, printing the carbon paste ink with different resistance on a substrate by a screen printer, and curing to obtain a resistance film layer with different resistance.
S2, preparation of a wave-absorbing material: preparing a material for preparing a reflecting layer and a foam core material for standby, then periodically superposing the foam core material, a resistance film layer, the foam core material and the resistance film layer on one side of the prepared reflecting layer material in sequence, wherein the sheet resistance value of the resistance film layer is superposed in sequence from small to large, then coating an adhesive between the layers, and then adopting a vacuum bag pressing molding process to press to obtain the broadband wave absorbing material.
According to the invention, carbon paste ink with high resistance and low resistance can be used, and the carbon paste ink with different resistance can be prepared after being uniformly mixed according to the proportion according to different required resistance.
As an optional implementation mode, in the preparation method provided by the invention, the vacuum degree of vacuum bag compression molding in the step S2 is-0.1 Mpa to-0.05 Mpa, the temperature is 80-100 ℃, and the compression time is 2-3h.
As an optional implementation manner, in the preparation method provided by the invention, the mixing ratio of the high-resistance carbon paste ink to the low-resistance carbon paste ink in the step S1 is (1-8): 1-7.
When the absorption layers are two layers, the resistance film layer comprises a low-resistance film layer and a high-resistance film layer, the square resistance of the low-resistance film layer is 150-240 Ω/∈,/- Σ, and the square resistance of the high-resistance film layer is 1300-1600 Ω/- Σ.
When the square resistance value of the prepared resistance film layer is 150-240 omega/≡, the mixing ratio of the high-resistance carbon paste ink to the low-resistance carbon paste ink is (0.9-1.1) (4.9-5.1).
When the square resistance value of the prepared resistance film layer is 1300-1600 omega/≡, the mixing ratio of the high-resistance carbon paste ink to the low-resistance carbon paste ink is (3.9-4.1) (2.9-3.1).
When the absorption layer is three layers, the resistance film layer comprises a low-resistance film layer, a middle-resistance film layer and a high-resistance film layer, the square resistance of the low-resistance film layer is 150-240 Ω/≡s, the square resistance of the middle-resistance film layer is 450-600 Ω/≡s, and the square resistance of the high-resistance film layer is 1300-1600 Ω/≡s.
When the square resistance value of the prepared resistance film layer is 450-600 omega/≡, the mixing ratio of the high-resistance carbon paste ink to the low-resistance carbon paste ink is (0.9-1.1).
When the absorption layer is four layers, the sheet resistance of the resistance film layer is 150-240 Ω/≡o, 300-500 Ω/≡o, 700-850 Ω/≡o and 1300-1600 Ω/≡o.
When the square resistance value of the prepared resistance film layer is 300-500 omega/≡, the mixing ratio of the high-resistance carbon paste ink to the low-resistance carbon paste ink is (1.9-2.1) (4.9-5.1).
When the square resistance value of the prepared resistance film layer is 700-850 omega/≡, the mixing ratio of the high-resistance carbon paste ink to the low-resistance carbon paste ink is (7.9-8.1) (6.9-7.1).
Compared with the prior art, the invention has the beneficial effects that:
(1) The broadband wave-absorbing material prepared by the method has the characteristics of thin thickness, broadband absorption and high-efficiency absorption, can realize electromagnetic wave absorption in an X (8-12 GHz) wave band and a Ku (12-18 GHz) wave band respectively, can realize that the full-band electromagnetic wave absorption rate is higher than 95% under vertical polarization and horizontal polarization, can be widely applied to stealth parts of military equipment, and has wide application scenes.
(2) The broadband wave-absorbing material prepared by the method has the advantages of light weight, simple preparation process, uniform and controllable molding pressure and simple molding process equipment, so that the whole process is easy to control, the uniformity of products can be effectively ensured, and the production efficiency can be greatly improved.
(3) According to the invention, the optimal impedance matching is realized by adjusting and optimizing the periodic structure and specification of the ink layer, the sheet resistance value of the ink layer and the thickness of the foam core material layer in the resistance film layer, and the efficient absorption in the 8-18GHz frequency band is further realized.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic structural view of a wave-absorbing material prepared in the present invention;
FIG. 2 is a schematic structural view of a periodic cross-shaped slit in embodiment 3;
FIG. 3 is a schematic structural view of a periodic cross-shaped slit in embodiment 2;
FIG. 4 is a graph showing the reflectance test result of the wave-absorbing material prepared in example 3;
FIG. 5 is a graph showing the reflectance test result of the wave-absorbing material prepared in example 4;
fig. 6 is a graph showing the reflectance test result of the wave-absorbing material prepared in example 2.
Reference numerals:
1. a reflective layer; 2. a foam core layer; 3. a resistive thin film layer;
31. a substrate layer; 32. an ink layer.
Detailed Description
The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments are shown, for the purpose of illustrating the invention, but the scope of the invention is not limited to the specific embodiments shown.
Unless defined otherwise, all technical and scientific terms used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the scope of the present invention.
Unless otherwise specifically indicated, the various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or may be prepared by existing methods.
Example 1
The broadband wave-absorbing material comprises a reflecting layer 1 and an absorbing layer, wherein the absorbing layer is at least two layers, and the absorbing layers of two layers or more than two layers are sequentially overlapped on one side of the reflecting layer 1, namely, the structure of arranging multiple layers of absorbing layers on the reflecting layer. The absorber layer comprises a foam core layer 2 and a resistive film layer 3, wherein the foam core layer 2 is connected to the reflective layer 1 as shown in fig. 1. The sheet resistance of the resistive film layer 3 increases in sequence in a direction away from the reflective layer 1, that is, the sheet resistance of the resistive film layer 3 in the absorption layer connected to the reflective layer 1 is the smallest, and the sheet resistance increases as it is superimposed.
In the invention, the resistive film layer 3 is used for realizing the matching of the surface impedance of the wave absorbing material and the free space wave impedance, changing the scattering characteristic of electromagnetic waves, ensuring the electromagnetic waves to enter and simultaneously carrying out electric loss and dissipating the entered electromagnetic energy. The foam core layer 2 mainly plays roles in supporting the whole structure, wave transmission and matching. The two components form an absorption layer for absorbing the electromagnetic wave. The absorption layer is provided with two or more layers, and the foam core material layer and the resistance film layer are alternately overlapped, so that the effect is that the resistance film layer 3 of the surface layer is utilized to directly absorb the loss for the first time, the rest electromagnetic wave is further absorbed through the lower resistance film layer 3, and finally the electromagnetic wave which is not lost is absorbed through the resistance film layer 3 again by utilizing the reflecting plate, so that the effect of high-efficiency absorption is achieved. The sheet resistance of the resistive film layer 3 increases from the reflective layer 1 to a direction away from the reflective layer 1 in sequence, namely, after electromagnetic waves enter, the electromagnetic waves pass through the resistive film layer 3 with a large sheet resistance, and are mainly absorbed by the electromagnetic waves in the Ku wave band, and then the electromagnetic waves in the X wave band are absorbed by the resistive film layer 3 with a small sheet resistance. The resistance film layers 3 with different sheet resistances are arranged and used for absorbing electromagnetic waves with different frequency bands so as to achieve the effect of broadband absorption.
The resistive film layer 3 includes a base material layer 31 and an ink layer 32, the base material layer 31 is connected with the foam core material layer 2, the ink layer 32 is attached to the base material layer 31, the ink layer 32 is used for absorbing and dissipating electromagnetic waves, and the base material layer 31 is used for attaching the ink layer 32. The ink layer 32 is provided with a periodic cross-shaped slit, as shown in fig. 2, wherein the width of the slit is 0.4-0.6 mm, and the unit period of the periodic cross-shaped slit is 7.5-8.5 mm. The ink layer 32 is provided with periodic cross-shaped gaps, in particular to a plurality of periodically arranged cross-shaped patterns, namely, when the ink layer 32 is prepared on a substrate, the cross-shaped patterns are not provided with the ink layer 32, and are exposed substrates. By setting a cross-shaped gap with a specific width and a specific period, wave-transmitting effect is realized.
The periodic cross-shaped slit referred to in the present application is not limited to a standard cross shape, and a parting structure derived from a cross shape is also included in the scope of the present application, as shown in fig. 3.
The thickness of the broadband wave absorbing material is 6.5 mm-16.5 mm, wherein the thickness of the substrate layer is 0.05 mm-0.1 mm; the thickness of the ink layer is 0.015 mm-0.025 mm; the thickness of the foam core material layer is 2.5 mm-3.5 mm, and the density is 75-110 kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the The thickness of the reflecting plate is 0.05mm, so that the thickness of the prepared wave-absorbing material is 6.5 mm-16.5 mm, and the wave-absorbing material is thin.
The surface density of the broadband wave-absorbing material is 1.25-2.37kg/m 2 The wave-absorbing material can meet the light quality.
In the implementation process, the absorption layer may be set to 2-4 layers.
When the absorption layers are four layers, the sheet resistance of the high-resistance thin film layer positioned on the surface layer ranges from 1300 to 1600 Ω/∈s, the sheet resistance of the resistance thin film layer positioned on the middle layer ranges from 700 to 850 Ω/∈s and 300 to 500 Ω/∈s, and the sheet resistance of the low-resistance thin film layer positioned on the lower layer ranges from 150 to 240 Ω/∈s.
When the absorption layer is three layers, the high-resistance thin film layer square resistance range of the surface layer is 1300-1600 Ω/∈s, the resistance thin film layer square resistance range of the middle layer is 450-600 Ω/∈s, and the low-resistance thin film layer square resistance range of the lower layer is 150-240 Ω/∈s.
When the number of the absorption layers is two, the sheet resistance of the high-resistance thin film layer positioned on the surface layer ranges from 1300 to 1600 Ω/≡c, and the sheet resistance of the low-resistance thin film layer positioned on the lower layer ranges from 150 to 240 Ω/≡c.
Examples
The preparation method of the broadband wave-absorbing material with four absorbing layers comprises the following steps:
preparation of a resistor film layer:
(1) A mesh panel was prepared according to a designed periodic cruciform derived pattern, as shown in figure 3, in which the period R of the cells was 8.5mm, the width w=0.6 mm of the cruciform channels, x1=1.0 mm, y1=0.75, y2=1.4 mm, and the distance between each cruciform channel was 2 xgap=0.5 mm.
(2) And (3) selecting 40 omega/∈18 carbon paste ink and 14000 omega/∈18 carbon paste ink, mixing according to a mass ratio of 5:1, stirring for 5min by using a stirrer, placing a substrate on a screen printer, printing to obtain a periodic resistor film primary blank with a sheet resistance value of 150 omega/∈18, and curing at 180 ℃ for 3h to obtain a first resistor film layer.
(3) And (3) selecting 40 omega/∈18 carbon paste ink and 14000 omega/∈18 carbon paste ink, mixing according to a mass ratio of 3:4, stirring for 5min by using a stirrer, placing a substrate on a screen printer, printing to obtain a periodic resistor film primary blank with a sheet resistance value of 350 omega/∈18, and curing at 180 ℃ for 3h to obtain a second resistor film layer.
(4) And (3) selecting 40 omega/∈18 carbon paste ink and 14000 omega/∈18 carbon paste ink, mixing according to the mass ratio of 8:7, stirring for 5min by using a stirrer, placing a substrate on a screen printer, printing to obtain a periodic resistor film blank with the square resistance value of 800 omega/∈18, and curing at 180 ℃ for 3h to obtain a third resistor film layer.
(5) And (3) mixing 40 omega/∈18 carbon paste ink and 15000 omega/∈18 carbon paste ink according to a mass ratio of 4:3, stirring for 5min by using a stirrer, placing a substrate on a screen printer, printing to obtain a periodic resistor film primary blank with a sheet resistance value of 1600 omega/∈18, and curing at 180 ℃ for 3h to obtain a fourth resistor film layer.
(II) preparation of a wave-absorbing material:
the method comprises the steps of sequentially superposing a fourth resistance film layer, a fourth foam core material layer, a third resistance film layer, a third foam core material layer, a second resistance film layer, a second foam core material layer, a first resistance film layer, a first foam core material layer and a reflecting plate, coating an epoxy resin adhesive film between each layer, and adopting a vacuum bag pressing molding process, wherein the process conditions are as follows: the vacuum degree is-0.05 Mpa, the temperature is 100 ℃, the pressing time is 3 hours, and the broadband wave-absorbing material is prepared.
The reflecting plate is an aluminum block with the thickness of 0.05mm. The foam core material layer adopts PMI foam with the density of 85kg/m and the dielectric constant of 1.09 (1+0.0069i), the thickness of the first foam core material layer is 2.5mm, the thickness of the second foam core material layer is 2.5mm, the thickness of the third foam core material is 3.0mm, and the thickness of the fourth foam core material is 3.5mm. FR4 is adopted as a base material of the resistance film layer, the thickness is 0.05mm, the dielectric constant is 4.3 (1+0.025 i), the thickness of the ink layer is 0.025mm, the thickness of adhesive between each layer is 0.1mm, the theoretical design thickness is 12.65mm, a flat sample piece with the size of 300mmx300mm is prepared, the thickness of the prepared sample is 12.73mm under the condition that errors exist in the actual thickness of a foam slice, and the surface density is 2.2775kg/m 2 The thickness is basically consistent with the design thickness, and the design requirement is met.
As shown in FIG. 6, it can be seen that the wave-absorbing material in this embodiment has a reflectivity of less than-25 dB at 8-18GHz, and the absorption band covers the whole X-band and Ku-band, and the absorption bandwidth exceeds 10GHz.
Examples
The preparation method of the broadband wave-absorbing material with the two absorption layers comprises the following steps:
preparation of a resistor film layer:
(1) A mesh sheet was prepared according to a designed periodic cruciform pattern, as shown in fig. 2, in which the period R of the cells was 8mm, the width w=0.5 mm of the cruciform channels, and the distance between each cruciform channel was 2 xgap=0.5 mm.
(2) And (3) mixing 30 omega/∈18 carbon paste ink and 15000 omega/∈18 carbon paste ink according to a mass ratio of 5:1, stirring for 5min by using a stirrer, placing a substrate on a screen printer, printing to obtain a periodic resistor film primary blank with a sheet resistance value of 200 omega/∈18, and curing at 180 ℃ for 3h to obtain a first resistor film layer.
(3) And (3) mixing 30 omega/∈18 carbon paste ink and 15000 omega/∈18 carbon paste ink according to a mass ratio of 3:4, stirring for 5min by using a stirrer, placing a substrate on a screen printer, printing to obtain a periodic resistor film primary blank with a sheet resistance value of 1300 omega/∈18, and curing at 180 ℃ for 3h to obtain a second resistor film layer.
(II) preparation of a wave-absorbing material:
sequentially superposing a second resistance film layer, a second foam core material layer, a first resistance film layer, a first foam core material layer and a reflecting plate, coating an epoxy resin adhesive film between each layer, and adopting a vacuum bag pressing molding process under the following process conditions: the vacuum degree is-0.1 Mpa, the temperature is 100 ℃, the pressing time is 2h, and the broadband wave-absorbing material is prepared.
In this embodiment, the reflective plate is made of aluminum alloy, and has a thickness of 0.1mm. The foam core material layer adopts PMI foam with the density of 75kg/m, the dielectric constant of 1.09 (1+0.0069i), the thickness of the second foam core material layer is 3.5mm, and the thickness of the first foam core material layer is 3mm. FR4 is adopted as a base material of the resistance film layer, the thickness is 0.05mm, the dielectric constant is 4.3 (1+0.025 i), the thickness of the ink layer is 0.02mm, the thickness of adhesive between each layer is 0.1mm, the theoretical design thickness is 7.14mm, a flat sample piece with the size of 300mmx300mm is prepared, the thickness of the prepared sample is 7.2mm under the condition that the actual thickness of a foam slice has errors, and the surface density is 1.34kg/m 2 The thickness is basically consistent with the design thickness, and the design requirement is met.
The reflectivity of the prepared sample piece is tested by an arch method, and as shown in fig. 4, the reflectivity of the wave-absorbing structure is less than-25 dB at 8-18 GHz.
Examples
The preparation method of the broadband wave-absorbing material with the three absorbing layers comprises the following steps:
preparation of a resistor film layer:
(1) A mesh panel was prepared according to a designed periodic cruciform derived pattern, as shown in figure 3, in which the period R of the cells was 8.3mm, the width w=0.5 mm of the cruciform channels, x1=0.9 mm, y1=0.65, y2=1.2 mm, and the distance between each cruciform channel was 2 xgap=0.5 mm.
(2) And (3) selecting 40 omega/∈18 carbon paste ink and 12000 omega/∈18 carbon paste ink, mixing according to a mass ratio of 5:1, stirring for 5min by using a stirrer, placing a substrate on a screen printer, printing to obtain a periodic resistor film primary blank with a sheet resistance value of 180 omega/∈18, and curing at 180 ℃ for 3h to obtain a first resistor film layer.
(3) Selecting 40 omega/≡carbon paste ink and 12000 omega/≡carbon paste ink according to the mass ratio of 1:1, mixing, stirring for 5min by using a stirrer, placing a base material on a screen printer, printing to obtain a periodic resistor film primary blank with the square resistance value of 530 omega/≡, and curing at 180 ℃ for 3h to obtain a second resistor film layer.
(4) And (3) mixing 40 omega/∈18 carbon paste ink and 12000 omega/∈3 carbon paste ink according to a mass ratio, stirring for 5min by using a stirrer, placing a substrate on a screen printer, printing to obtain a periodic resistor film blank with a sheet resistance value of 1450 omega/∈18, and curing at 180 ℃ for 3h to obtain a third resistor film layer.
(II) preparation of a wave-absorbing material:
sequentially superposing a third resistance film layer, a third foam core material layer, a second resistance film layer, a second foam core material layer, a first resistance film layer, a first foam core material layer and a reflecting plate, coating an epoxy resin adhesive film between each layer, and adopting a vacuum bag pressing molding process, wherein the process conditions are as follows: the vacuum degree is-0.05 Mpa, the temperature is 100 ℃, the pressing time is 3 hours, and the broadband wave-absorbing material is prepared.
The reflecting plate is an aluminum block and has the thickness of 0.1mm. The foam core material layer adopts PMI foam with the density of 110kg/m and the dielectric constant of 1.09 (1+0.0069i), and the third foam core materialThe layer thickness was 3.3mm, the second foam core layer thickness was 2.8mm, and the first foam core layer thickness was 2.5mm. FR4 is adopted as a base material of the resistance film layer, the thickness is 0.05mm, the dielectric constant is 4.3 (1+0.025 i), the thickness of the ink layer is 0.015mm, the thickness of adhesive between each layer is 0.05mm, the theoretical design thickness is 9.195mm, a flat sample piece with the size of 300mmx300mm is prepared, the thickness of the prepared sample is 9.1mm under the condition that the actual thickness of a foam slice has errors, and the surface density is 2.046kg/m 2 The thickness is basically consistent with the design thickness, and the design requirement is met.
As shown in FIG. 5, it can be seen that the wave-absorbing material in this embodiment has a reflectivity of less than-25 dB at 8-18GHz, and the absorption band covers the whole X-band and Ku-band, and the absorption bandwidth exceeds 10GHz.
The foregoing is a further detailed description of the invention in connection with the preferred embodiments, and it is not intended that the invention be limited to the specific embodiments described. It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the spirit of the invention, and these should be considered to be within the scope of the invention.
Claims (5)
1. The broadband wave absorbing material comprises a reflecting layer and an absorbing layer, and is characterized in that the absorbing layer is at least two layers, and two or more than two absorbing layers are sequentially overlapped on one side of the reflecting layer;
the absorption layer comprises a foam core material layer and a resistance film layer, the foam core material layer is connected with the reflecting layer, and the foam core material layer, the resistance film layer, the foam core material layer and the resistance film layer are periodically overlapped on one side of the reflecting layer according to the sequence of the foam core material layer, the resistance film layer and the resistance film layer; the square resistance value of the resistance film layer is sequentially increased in a direction away from the reflecting layer; when the absorption layers are two layers, the square resistance values of the resistance film layers are 150-240 omega/≡and 1300-1600 omega/≡respectively; when the absorption layer is three layers, the square resistance values of the resistance film layer are 150-240 Ω/≡s, 450-600 Ω/≡s and 1300-1600 Ω/≡s respectively; when the absorption layer is four layers, the square resistance values of the resistance film layers are 150-240 Ω/≡o, 300-500 Ω/≡o, 700-850 Ω/≡o and 1300-1600 Ω/≡o respectively;
the resistive film layer comprises a substrate layer and an ink layer, wherein the substrate layer is connected with the foam core material layer in a single absorption layer, and the ink layer is attached to the substrate layer; the ink layer is provided with a periodic cross-shaped gap, the gap width W is 0.4-0.6 mm, and the unit period R of the periodic cross-shaped gap is 7.5-8.5 mm;
the thickness of the foam core material layer is 2.5 mm-3.5 mm; the thickness of the base material layer is 0.05-0.1 mm, the thickness of the ink layer is 0.015-0.025 mm, and the thickness of the wave absorbing material is 6.5-16.5 mm;
the wave absorption frequency band of the wave absorption material comprises 8-18GHz, and the reflectivity of the wave absorption material in the X wave band and the Ku wave band is less than-25 dB.
2. The broadband wave absorbing material according to claim 1, wherein when the absorbing layer is two layers, the second layer is increased by 442% to 967% based on the sheet resistance of the first layer; when the absorption layer is three layers, the second layer is increased by 80% to 300% based on the first layer sheet resistance value, and the third layer is increased by 116% to 250% based on the second layer sheet resistance value; when the absorption layer is four layers, the second layer is increased by 25% to 233% on the basis of the first layer sheet resistance, the third layer sheet resistance is increased by 40% to 183% on the basis of the second layer, and the fourth layer sheet resistance is increased by 53% to 128% on the basis of the third layer.
3. A method for preparing a broadband wave-absorbing material according to any one of claims 1-2, characterized by comprising the steps of:
s1, preparing a resistance film layer: mixing high-resistance carbon paste ink with the resistance of 12000-15000 omega/∈and low-resistance carbon paste ink with the resistance of 30-40 omega/∈s to prepare carbon paste ink with different resistance values, printing the carbon paste ink with different resistance values on a substrate through a screen printer to form periodic cross-shaped gaps on the substrate, and curing to obtain a resistance film layer with different resistance values;
s2, preparation of a wave-absorbing material: preparing a material for preparing a reflecting layer and a foam core material for standby, then periodically superposing the foam core material, a resistance film layer, the foam core material and the resistance film layer on one side of the prepared reflecting layer material in sequence, wherein the sheet resistance value of the resistance film layer is superposed in sequence from small to large, then coating an adhesive between the layers, and then adopting a vacuum bag pressing molding process to press to obtain the broadband wave absorbing material.
4. The method for preparing a broadband wave-absorbing material according to claim 3, wherein the vacuum degree of vacuum bag compression molding in the step S2 is-0.1 Mpa to-0.05 Mpa, the temperature is 80 ℃ to 100 ℃, and the compression time is 2 to 3 hours.
5. The method of producing a broadband wave absorbing material according to claim 3, wherein the mixing ratio of the high-resistance carbon paste ink and the low-resistance carbon paste ink in step S1 is (1-8): 1-7.
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