CN115674819A - 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 at least two absorbing layers, wherein the two or more 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 reflection layer, and the square resistance value of the resistance film layer is sequentially increased according to the direction far away from the reflection layer. The broadband wave-absorbing material prepared by the invention has the characteristics of broadband absorption and efficient absorption, can realize the electromagnetic wave absorption in X (8-12 GHz) wave band and Ku (12-18 GHz) wave band respectively, can realize the full-band electromagnetic wave absorption rate 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, a radar system can realize broadband coverage on a detection target, and the requirement on a broadband structure wave-absorbing composite material is more and more urgent. The radar wave-absorbing material has to meet two conditions at the same time to realize excellent wave-absorbing performance: firstly, the surface impedance of the wave-absorbing material is matched with the wave impedance of free space so as to ensure that electromagnetic waves can enter the material; and secondly, the inside of the wave-absorbing material needs to have electric loss or magnetic loss so as to dissipate electromagnetic energy entering the wave-absorbing material.
Most of the traditional wave-absorbing structures are based on Salisbury absorbing screens, jaumman absorbers and multi-layer impedance matching wave-absorbing materials, and have the typical problems of large thickness and narrow absorbing frequency band. The main method for expanding the absorption frequency band is to increase the thickness or improve the content of the absorbent, but the broadband wave-absorbing performance under the condition of small thickness is difficult to realize due to the influence of the electromagnetic parameter dispersion characteristic or the resonance electric thickness of the material. The appearance and development of the metamaterial enable people to control the electromagnetic performance of the material from a macroscopic dimension level, so that the interaction relation between the material and electromagnetic waves is obviously influenced, and the application of the metamaterial in the electromagnetic wave absorption technology becomes a popular research direction. Compared with the traditional wave-absorbing material, the dependence of broadband wave-absorbing performance on the intrinsic electromagnetic parameter frequency 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 the realization of broadband absorption still has certain difficulty.
Disclosure of Invention
In order to overcome the technical problems of heavy wave-absorbing material and narrow absorption frequency band in the prior art, the invention provides a broadband wave-absorbing material and a preparation method thereof.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
the invention provides a broadband wave-absorbing material, which comprises a reflecting layer and at least two absorbing layers, wherein the two or more absorbing layers are sequentially overlapped on one side of the reflecting layer.
The absorbing 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 sheet resistance value of the resistance film layer is sequentially increased according to the direction far away from the reflecting layer.
The thickness of the foam core material layer is 2.5mm to 3.5mm.
The absorbing layer in the wave-absorbing material is formed by alternately overlapping the foam core material layer and the resistance film layer, and has the functions of realizing the matching of the surface impedance of the wave-absorbing material and the wave impedance of a free space by using the resistance film layer, changing the scattering characteristic of electromagnetic waves, ensuring that the electromagnetic waves enter and simultaneously perform electric loss, and dissipating the entering electromagnetic energy. The foam core material layer is arranged to mainly play a role in supporting the whole structure, transmitting waves and matching. The absorption layer sets up two-layerly or more, utilizes the resistance film layer of surface course earlier directly to carry out first absorption loss, and the surplus electromagnetic wave is further absorbed through the resistance film layer below, utilizes the reflecting plate to pass through the resistance film layer absorption once more with the electromagnetic wave that does not lose at last, reaches high-efficient absorptive effect. And the resistance film layers with different square resistance values are arranged for realizing the absorption of electromagnetic waves with different frequency bands so as to achieve the effect of broadband absorption. The square resistance value of the resistance thin 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 mainly absorbs the Ku waveband electromagnetic wave through the resistance thin film layer with large square resistance value, and then absorbs the X waveband electromagnetic wave by utilizing the resistance thin film layer with small square resistance value.
As an optional embodiment, in the broadband wave-absorbing material provided by the invention, when the absorbing layer is two layers, the sheet resistance of the second layer is increased by 442% to 967% on the basis of the sheet resistance of the first layer; when the absorption layer is three layers, the second layer is increased by 80 to 300 percent based on the sheet resistance value of the first layer, and the third layer is increased by 116 to 250 percent based on the sheet resistance value of the second layer; when the absorption layer is four layers, the second layer is increased by 25 to 233 percent based on the square resistance value of the first layer, the third layer is increased by 40 to 183 percent based on the square resistance value of the second layer, and the fourth layer is increased by 53 to 128 percent based on the square resistance value of the third layer.
As an optional implementation manner, in the broadband wave-absorbing material provided by the present invention, the resistance film layer includes a substrate layer and an ink layer, the substrate layer is connected to the foam core layer in a single absorbing layer, and the ink layer is attached to the substrate layer.
In this application, the ink layer is used for absorbing and dissipating electromagnetic waves, and the substrate layer is used for attaching the ink layer.
As an optional embodiment, in the broadband wave-absorbing material provided by the present invention, the material of the substrate layer is FR4.
As an optional implementation mode, in the broadband wave-absorbing material provided by the invention, the ink layer is provided with a periodic cross-shaped gap, the width W of the gap is 0.4-0.6 mm, and the unit period R of the periodic cross-shaped gap is 7.5-8.5 mm.
Set up periodic cross gap in this application on the printing ink layer, specifically be the cross pattern of a plurality of periodic arrangement, when preparing the printing ink layer on the substrate promptly, the cross pattern part does not set up the printing ink layer, for naked substrate. Through setting up the cross gap of specific width and specific period, changed original equivalent circuit, increased the electric capacity, changed the scattering characteristic of electromagnetic wave, realize the wave-transparent effect, utilize next layer resistance film layer to absorb behind the electromagnetic wave that will not absorb sees through, perhaps absorb behind the reflection stratum reflection to this realization is to the broadband absorption of electromagnetic wave.
The periodic cruciform slits referred to in this application are not limited to standard cruciform shapes and parting structures derived from cruciform shapes are also included in the scope of this application.
As an optional implementation mode, in the broadband wave-absorbing material provided by the invention, the thickness of the base material layer is 0.05mm to 0.1mm, the thickness of the ink layer is 0.015mm to 0.025mm, and the thickness of the wave-absorbing material is 6.5mm to 16.5mm.
The single-layer degree of backward movement of each part is limited within the range, compared with the existing wave-absorbing material, the broadband wave-absorbing material prepared by combination has the advantages that the degree of backward movement is greatly reduced, the thickness is reduced, meanwhile, multi-layer absorption is adopted, electromagnetic waves enter from the big to the small direction of the resistance value of the resistance film layer, and broadband absorption can be realized while the thickness is reduced.
As an optional implementation mode, in the broadband wave-absorbing material provided by the invention, when the absorbing layer is two layers, the square resistance values of the resistance thin film layer are 150-240 omega/\9633and1300-1600 omega/\9633; when the absorption layer is three layers, the square resistance values of the resistance film layer are respectively 150-240 omega/\9633, 450-600 omega/\9633, and 1300-1600 omega/\9633; when the absorption layer is four layers, the square resistance values of the resistance film layers are 150-240 omega/\9633, 300-500 omega/\9633, 700-850 omega/\9633and1300-1600 omega/\9633.
In the present invention, when the absorption layer is provided as two layers, the resistance value is 1300-1600 omega/9633the resistance value is 150-240 omega/9633for Ku band mainly and X band mainly; when the three layers are arranged, 1300-1600 omega/\ 9633, 450-600 omega/\ 9633for 10-18GHz, 150-240 omega/\ 9633for 10-14GHz, and 8-10GHz; in the case of four layers, 1300-1600 omega/\9633isadopted, 700-850 omega/\9633isadopted for 15-18GHz, 700-500 omega/\9633isadopted for 12-15GHz,300-500 omega/\\9633isadopted for 10-12GHz,150-240 omega/\9633isadopted for 8-10GHz.
As an optional embodiment, in the broadband wave-absorbing material provided by the invention, the density of the foam core material layer is 75 to 110kg/m 3 。
As an optional implementation mode, in the broadband wave-absorbing material provided by the invention, the wave-absorbing frequency band of the wave-absorbing material comprises 8 to 18GHz.
As an optional embodiment, in the broadband wave-absorbing material provided by the present invention, the reflectivities of the wave-absorbing material in the X band and the Ku band are less than-25 dB.
The density of the foam core material is limited to 75 to 110kg/m 3 Therefore, the characteristic of light weight of the wave-absorbing material in the application is realized.
As an optional implementation mode, in the broadband wave-absorbing material provided by the invention, the areal density of the broadband wave-absorbing material is 1.25 to 2.72kg/m 3 。
When the absorbent layer is two layers in the present invention, a 2.5mm density of 75kg/m is used 3 When the foam core material is used, the prepared wave-absorbing material has the surface density of 1.25kg/m 3 (ii) a When the absorbing layer is four layers, a 3.5mm density of 110kg/m is used 3 When the foam core material is used, the prepared wave-absorbing material has the surface density of 2.72kg/m 3 。
As an optional embodiment, in the broadband wave-absorbing material provided by the present invention, the foam core material layer is PMI foam.
As an optional implementation manner, 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.
As an optional embodiment, in the broadband wave-absorbing material provided by the present invention, the reflective layer is an aluminum alloy plate or an aluminum plate.
The second aspect of the invention provides a preparation method of the broadband wave-absorbing material, which comprises the following steps:
s1, preparing a resistance thin film layer: the carbon paste printing ink with different resistance values is prepared by mixing the high-resistance carbon paste printing ink with the resistance value of 12000-15000 omega/9633and the low-resistance carbon paste printing ink with the resistance value of 30-40 omega/9633, the carbon paste printing ink with different resistance values is printed on a substrate through a screen printing machine, and the resistance film layers with different resistance values are obtained after curing.
S2, preparing the wave-absorbing material: preparing a material for preparing the reflecting layer and a foam core material for standby, then periodically stacking the foam core material, the resistance film layer, the foam core material and the resistance film layer on one side of the prepared reflecting layer material according to the sequence of the foam core material, the resistance film layer, the foam core material and the resistance film layer, wherein the square resistance values of the resistance film layer are stacked from small to large, then coating an adhesive between the layers, and pressing by adopting a vacuum bag pressing forming process to obtain the broadband wave-absorbing material.
According to the invention, the carbon paste printing ink with different resistances can be prepared by uniformly mixing the carbon paste printing ink with high resistance and low resistance according to different required resistances in proportion.
As an optional implementation mode, in the preparation method provided by the invention, the vacuum degree of vacuum bag pressing molding in the step S2 is-0.1 Mpa to-0.05 Mpa, the temperature is 80 ℃ to 100 ℃, and the pressing time is 2-3h.
As an optional implementation mode, in the preparation method provided by the invention, the mixing ratio of the high-resistance carbon paste ink and the low-resistance carbon paste ink in the step S1 is (1-8) to (1-7).
When the absorption layer is two layers, the resistance film layer comprises a low resistance film layer and a high resistance film layer, the square resistance value of the low resistance film layer is 150-240 omega/\9633, and the square resistance value of the high resistance film layer is 1300-1600 omega/\9633.
When the sheet resistance value of the prepared resistance film layer is 150-240 omega/\ 9633h, the mixing ratio of the high-resistance carbon paste ink and the low-resistance carbon paste ink is (0.9-1.1) to (4.9-5.1).
When the square resistance value of the prepared resistance film layer is 1300-1600 omega/\ 9633h, the mixing ratio of the high-resistance carbon paste ink and the low-resistance carbon paste ink is (3.9-4.1) to (2.9-3.1).
When the absorption layer is three layers, the resistance film layer comprises a low resistance value resistance film layer, a middle resistance value resistance film layer and a high resistance value resistance film layer, the square resistance value of the low resistance value resistance film layer is 150-240 omega/\9633, the square resistance value of the middle resistance value resistance film layer is 450-600 omega/\9633, and the square resistance value of the high resistance value resistance film layer is 1300-1600 omega/\9633.
When the square resistance value of the prepared resistance film layer is 450-600 omega/\ 9633, the mixing ratio of the high-resistance carbon paste ink and the low-resistance carbon paste ink is (0.9-1.1) to (0.9-1.1).
When the absorption layer is four layers, the sheet resistance values of the resistive film layer are 150-240 omega/\9633, 300-500 omega/\9633, 700-850 omega/\9633, and 1300-1600 omega/\9633.
The square resistance value of the prepared resistance film layer is 300-500 omega/\ 9633, and when the mixing ratio of the high-resistance carbon paste ink and 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/\ 9633, the mixing ratio of the high-resistance carbon paste ink and the low-resistance carbon paste ink is (7.9-8.1) to (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 invention is thin in thickness, has the characteristics of broadband absorption and efficient absorption, can realize the absorption of electromagnetic waves in X (8-12 GHz) wave bands and Ku (12-18 GHz) wave bands respectively, can realize the full-band electromagnetic wave absorption rate 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 forming pressure and simple forming 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) The invention realizes the optimal impedance matching by adjusting and optimizing the periodic structure and specification of the ink layer in the resistance film layer, the square resistance value of the ink layer and the thickness of the foam core material layer, and further realizes the high-efficiency absorption in the frequency band of 8-18 GHz.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic structural diagram of a wave-absorbing material prepared in the present invention;
FIG. 2 is a schematic view showing the structure of a periodic cross-shaped slit in example 3;
FIG. 3 is a schematic view of a structure of a periodic cross slit in example 2;
FIG. 4 is a graph of the reflectivity test results of the wave-absorbing material prepared in example 3;
FIG. 5 is a graph of the reflectivity test results of the absorbing material prepared in example 4;
FIG. 6 is a graph of the reflectivity test results 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. and (4) an ink layer.
Detailed Description
In order to facilitate understanding of the invention, the invention will be described more fully and in detail with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.
Unless otherwise defined, all terms of art 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 limit the scope of the present invention.
Unless otherwise specifically indicated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
Example 1
The application prepares a broadband absorbing material, wherein absorbing material includes reflection stratum 1 and absorbed layer, and wherein the absorbed layer is two-layer at least, and two-layer or more than two absorbed layer superpose in proper order in one side of reflection stratum 1, sets up the structure of multilayer absorbed layer on the reflection stratum promptly. The absorbent 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 figure 1. The sheet resistance value of the resistance thin film layer 3 is sequentially increased according to the direction far away from the reflecting layer 1, namely the sheet resistance value of the resistance thin film layer 3 in the absorbing layer connected with the reflecting layer 1 is the smallest, and the sheet resistance value is larger when the sheet resistance value is superposed upwards.
In the invention, the resistance film layer 3 is used for realizing the matching of the surface impedance of the wave-absorbing material and the wave impedance of free space, changing the scattering property of electromagnetic waves, ensuring that the electromagnetic waves enter and simultaneously perform electric loss, and dissipating the entering electromagnetic energy. The foam core material layer 2 mainly plays a role in supporting the whole structure, transmitting waves and matching. The two layers form an absorption layer for absorbing and losing electromagnetic waves. The absorbing layer sets up two-layer or more and foam core material layer and resistance film layer stack in turn, and the effect lies in utilizing the resistance film layer 3 of surface course earlier directly to carry out first absorption loss, and remaining electromagnetic wave is further absorbed through resistance film layer 3 below, utilizes the reflecting plate to absorb the electromagnetic wave that does not lose through resistance film layer 3 once more at last, reaches high-efficient absorptive effect. The square resistance value of the resistance thin film layer 3 is sequentially increased from the reflection layer 1 to the direction far away from the reflection layer 1, namely after the electromagnetic wave enters, the resistance thin film layer 3 with the large square resistance value firstly absorbs the Ku waveband electromagnetic wave, and then the resistance thin film layer 3 with the small square resistance value absorbs the X waveband electromagnetic wave. The resistance film layers 3 with different square resistance values are arranged and used for absorbing electromagnetic waves of different frequency bands so as to achieve the effect of broadband absorption.
The periodic cruciform slits referred to in this application are not limited to standard cruciform shapes and a parting structure derived from a cruciform shape is also within the scope of this application, as shown in figure 3.
Broadband wave absorbing materialThe thickness of the material is 6.5mm to 16.5mm, and the thickness of the base material layer is 0.05mm to 0.1mm; the thickness of the ink layer is 0.015mm to 0.025mm; the thickness of the foam core material layer is from 2.5mm to 3.5mm, and the density is from 75 to 110kg/m 3 (ii) a The thickness of the reflecting plate is 0.05mm, so that the thickness of the prepared wave-absorbing material is 6.5mm to 16.5mm, and the wave-absorbing material meets the property of thin thickness.
The surface density of the broadband wave-absorbing material is 1.25-2.37kg/m 3 So that the wave-absorbing material meets the property of light weight.
In a specific implementation process, the absorption layer can be set to be 2 to 4 layers.
When the absorption layer is four layers, the square resistance value range of the high resistance film layer positioned on the surface layer is 1300-1600 omega/\9633, the square resistance value range of the resistance film layer positioned on the middle layer is 700-850 omega/\9633, the square resistance value range of the resistance film layer positioned on the middle layer is 300-500 omega/\9633, and the square resistance value range of the low resistance film layer positioned on the lower layer is 150-240 omega/\9633.
When the absorption layer is three layers, the square resistance value range of the high resistance film layer positioned on the surface layer is 1300-1600 omega/\9633, the square resistance value range of the resistance film layer positioned on the middle layer is 450-600 omega/\9633, the square resistance value range of the low resistance film layer positioned on the lower layer is 150-240 omega/\9633.
When the absorption layer is two layers, the square resistance value range of the high resistance film layer positioned on the surface layer is 1300 to 1600 omega/9633, and the square resistance value range of the low resistance film layer positioned on the lower layer is 150 to 240 omega/9633.
Example 2
The preparation method of the broadband wave-absorbing material with four absorption layers comprises the following steps:
preparing a resistance thin film layer:
(1) A halftone was prepared according to a designed periodic cruciform derivative pattern as shown in FIG. 3, where the period R of the cells was 8.5mm, the width w =0.6mm, x1=1.0mm, y1=0.75, y2=1.4mm, and the distance between each cruciform slot was 2xgap =0.5mm.
(2) The carbon paste ink of 40 omega/\9633andthe carbon paste ink of 14000 omega/\9633aremixed according to the mass ratio of 5 to 1, stirred for 5min by a stirrer, and the substrate is placed on a screen printer to be printed to obtain a periodic resistance film primary blank with the square resistance of 150 omega/\9633andcured for 3h at 180 ℃ to obtain the first resistance film layer.
(3) The carbon paste ink of 40 omega/\9633andthe carbon paste ink of 14000 omega/\9633aremixed according to the mass ratio of 3 to 4, stirred for 5min by using a stirrer, and a substrate is placed on a screen printing machine to be printed to obtain a periodic resistance film primary blank with the square resistance value of 350 omega/\9633andcured for 3h at 180 ℃ to obtain a second resistance film layer.
(4) The carbon paste ink of 40 omega/\9633andthe carbon paste ink of 14000 omega/\9633aremixed according to the mass ratio of 8 to 7, stirred for 5min by a stirrer, and the substrate is placed on a screen printer to be printed to obtain a periodic resistance film primary blank with the square resistance value of 800 omega/\9633andcured for 3h at 180 ℃ to obtain a third resistance film layer.
(5) The carbon paste ink of 40 omega/\9633andthe carbon paste ink of 15000 omega/\9633aremixed according to the mass ratio of 4 to 3, stirred for 5min by a stirrer, the substrate is placed on a screen printer to be printed to obtain a periodic resistance film primary blank with the square resistance value of 1600 omega/\9633, and cured for 3h at 180 ℃ to obtain a fourth resistance film layer.
(II) preparing the wave-absorbing material:
superpose fourth resistance thin layer, fourth foam core material layer, third resistance thin layer, third foam core material layer, second resistance thin layer, second foam core material layer, first resistance thin layer, first foam core material layer and reflecting plate in order, coating epoxy glued membrane between every layer adopts vacuum bag pressure forming technology, and the technological condition is: the vacuum degree is-0.05 Mpa, the temperature is 100 ℃, and the pressing time is 3 hours, thus preparing the broadband wave-absorbing material.
The reflecting plate is an aluminum block with the thickness of 0.05mm. PMI foam with the density of 85kg/m is adopted as the foam core material layer, the dielectric constant is 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 layer is 3.0mm, and the thickness of the fourth foam core material layer is 3.5mm. The substrate of the resistance film layer is FR4, the thickness is 0.05mm, the dielectric constant is 4.3 (1 + 0.025i), the thickness of the ink layer is 0.025mm, the thickness of the bonding glue between each layer is 0.1mm, the theoretical design thickness is 12.65mm, and the prepared size is 300mmA flat plate sample with the thickness of 300mm is prepared, under the condition that the actual thickness of the foam slice has errors, the thickness of the prepared sample is 12.73mm, and the surface density is 2.2775kg/m 3 And the thickness is basically consistent with the design thickness, and the design requirement is met.
The reflectivity of the prepared sample is tested by the bow method, as shown in fig. 6, it can be seen from the figure that the reflectivity of the wave-absorbing material in this embodiment is less than-25 dB under 8 to 18ghz, the absorption band covers the whole X-band and Ku-band, and the absorption bandwidth exceeds 10GHz.
Example 3
The preparation method of the broadband wave-absorbing material with two absorption layers comprises the following steps:
preparing a resistance thin film layer:
(1) The halftone was prepared according to a designed periodic cross pattern as shown in fig. 2, in which the period R of the cells was 8mm, the width w =0.5mm of the cross grooves, and the distance between each cross groove was 2xgap =0.5mm.
(2) The carbon paste ink of 30 omega/\9633andthe carbon paste ink of 15000 omega/\9633aremixed according to the mass ratio of 5 to 1, stirred for 5min by a stirrer, the substrate is placed on a screen printer to be printed to obtain a periodic resistance film primary blank with the square resistance of 200 omega/\9633, and cured for 3h at 180 ℃ to obtain the first resistance film layer.
(3) And (2) mixing 30 omega/\9633thecarbon paste ink and 15000 omega/\9633thecarbon paste ink according to the mass ratio of 3.
(II) preparing a wave-absorbing material:
stacking a second resistance thin film layer, a second foam core material layer, a first resistance thin film layer, a first foam core material layer and a reflecting plate in sequence, coating an epoxy resin adhesive film between every two layers, and adopting a vacuum bag pressing forming process, wherein the process conditions are as follows: the vacuum degree is-0.1 Mpa, the temperature is 100 ℃, the pressing time is 2 hours, and the broadband wave-absorbing material is prepared.
In this embodiment, the reflective plate is made of aluminum alloy materialThe thickness is 0.1mm. PMI foam with the density of 75kg/m and the dielectric constant of 1.09 (1 + 0.0069i) is adopted as the foam core material layer, the thickness of the second foam core material layer is 3.5mm, and the thickness of the first foam core material layer is 3mm. The substrate of the resistance film layer is FR4, the thickness of the substrate is 0.05mm, the dielectric constant of the substrate is 4.3 (1 + 0.025i), the thickness of the ink layer is 0.02mm, the thickness of the adhesive between every two layers is 0.1mm, the theoretical design thickness is 7.14mm, a flat plate sample piece with the size of 300mmx300mm is prepared, under the condition that the actual thickness of a foam slice has errors, the thickness of the prepared sample piece is 7.2mm, and the areal density of the sample piece is 1.34kg/m 3 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 a bow method, as shown in figure 4, the reflectivity of the wave-absorbing structure is less than-25 dB at 8 to 18GHz.
Example 4
The preparation method of the broadband wave-absorbing material with three absorption layers comprises the following steps:
preparing a resistance thin film layer:
(1) The halftone was prepared according to a designed periodic cruciform derivative pattern, as shown in FIG. 3, where the unit period R was 8.3mm, the width w =0.5mm, x1=0.9mm, y1=0.65, y2=1.2mm, and the distance between each cruciform slot was 2xgap =0.5mm.
(2) The carbon paste ink of 40 omega/\9633ismixed with the carbon paste ink of 12000 omega/\9633ina mass ratio of 5.
(3) Selecting 40 omega/\ 9633the carbon paste ink and 12000 omega/\ 9633the carbon paste ink according to the mass ratio of 1:1, stirring for 5min by using a stirrer, placing the substrate on a screen printer, printing to obtain a periodic resistance film blank with the square resistance of 530 omega/\9633, and curing for 3h at 180 ℃ to obtain a second resistance film layer.
(4) The carbon paste ink of 40 omega/\9633ismixed with the carbon paste ink of 12000 omega/\9633ina mass ratio of 4.
(II) preparing a wave-absorbing material:
superpose third resistance thin layer, third foam core material layer, second resistance thin layer, second foam core material layer, first resistance thin layer, first foam core material layer and reflecting plate according to the order, and coating epoxy glued membrane adopts vacuum bag pressure forming technology between every layer, and the process conditions is: the vacuum degree is-0.05 Mpa, the temperature is 100 ℃, and the pressing time is 3 hours, thus preparing the broadband wave-absorbing material.
The reflecting plate is an aluminum block with the thickness of 0.1mm. PMI foam with the density of 110kg/m and the dielectric constant of 1.09 (1 + 0.0069i) is adopted as the foam core material layer, the thickness of the third foam core material layer is 3.3mm, the thickness of the second foam core material layer is 2.8mm, and the thickness of the first foam core material layer is 2.5mm. The substrate of the resistance film layer is FR4, the thickness of the substrate is 0.05mm, the dielectric constant of the substrate is 4.3 (1 + 0.025i), the thickness of the ink layer is 0.015mm, the thickness of the adhesive between every two layers is 0.05mm, the theoretical design thickness is 9.195mm, a flat plate sample piece with the size of 300mmx300mm is prepared, under the condition that the actual thickness of a foam slice has errors, the thickness of the prepared sample piece is 9.1mm, and the areal density of the sample piece is 2.046kg/m 3 The thickness is basically consistent with the design thickness, and the design requirement is met.
The reflectivity of the prepared sample is tested by the bow method, as shown in fig. 5, it can be seen from the figure that the reflectivity of the wave-absorbing material in this embodiment is less than-25 dB under 8 to 18ghz, the absorption band covers the whole X-band and Ku-band, and the absorption bandwidth exceeds 10GHz.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and is not intended to limit the practice of the invention to these embodiments. For those skilled in the art to which the invention pertains, numerous simple deductions or substitutions may be made without departing from the spirit of the invention, which shall be deemed to belong to the scope of the invention.
Claims (10)
1. A 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 reflection layer, and the sheet resistance value of the resistance film layer is sequentially increased along the direction far away from the reflection layer;
the thickness of the foam core material layer is 2.5 mm-3.5 mm.
2. The broadband wave-absorbing material of claim 1, wherein when the absorbing layer is two layers, the second layer has an increase of 442% to 967% over the sheet resistance of the first layer; when the absorption layer is three layers, the second layer is increased by 80 to 300 percent based on the sheet resistance value of the first layer, and the third layer is increased by 116 to 250 percent based on the sheet resistance value of the second layer; when the absorption layer is four layers, the second layer is increased by 25 to 233 percent based on the square resistance value of the first layer, the third layer is increased by 40 to 183 percent based on the square resistance value of the second layer, and the fourth layer is increased by 53 to 128 percent based on the square resistance value of the third layer.
3. A broadband wave absorbing material according to claim 1, wherein the resistive film layer comprises a substrate layer and an ink layer, the substrate layer is connected to the foam core layer in a single absorbing layer, and the ink layer is attached to the substrate layer.
4. The broadband wave-absorbing material of claim 3, wherein a periodic cross-shaped gap is formed in the ink layer, the width W of the gap is 0.4-0.6 mm, and the unit period R of the periodic cross-shaped gap is 7.5-8.5 mm.
5. The broadband wave-absorbing material as claimed in claim 3, wherein the thickness of the substrate layer is 0.05mm to 0.1mm, the thickness of the ink layer is 0.015mm to 0.025mm, and the thickness of the wave-absorbing material is 6.5mm to 16.5mm.
6. The broadband wave-absorbing material according to claim 1, wherein when the absorbing layer is two layers, the square resistance values of the resistance film layer are 150-240 Ω/\9633and1300-1600 Ω/\9633; when the absorption layer is three layers, the square resistance values of the resistance film layer are respectively 150-240 omega/\9633, 450-600 omega/\9633, and 1300-1600 omega/\9633; when the absorption layer is four layers, the sheet resistance values of the resistive thin film layer are 150-240 omega/\9633, 300-500 omega/\9633, 700-850 omega/\9633, and 1300-1600 omega/\9633, respectively.
7. The broadband wave-absorbing material according to claim 1, wherein the wave-absorbing frequency band of the wave-absorbing material comprises 8 to 18GHz; the reflectivity of the wave-absorbing material in an X wave band and a Ku wave band is less than-25 dB.
8. The preparation method of the broadband wave-absorbing material of any one of claims 1 to 7, which is characterized by comprising the following steps:
s1, preparing a resistance thin film layer: mixing the high-resistance carbon paste ink with the resistance value of 12000-15000 omega/\9633withthe low-resistance carbon paste ink with the resistance value of 30-40 omega/\9633toprepare carbon paste inks with different resistance values, printing the carbon paste inks with different resistance values on a substrate through a screen printing machine, and curing to obtain a resistance film layer with different resistance values;
s2, preparing the wave-absorbing material: preparing a material for preparing the reflecting layer and a foam core material for standby, then periodically stacking the foam core material, the resistance film layer, the foam core material and the resistance film layer on one side of the prepared reflecting layer material according to the sequence of the foam core material, the resistance film layer, the foam core material and the resistance film layer, wherein the square resistance values of the resistance film layer are stacked from small to large, then coating an adhesive between the layers, and pressing by adopting a vacuum bag pressing forming process to obtain the broadband wave-absorbing material.
9. The preparation method of the broadband wave-absorbing material according to claim 8, wherein the vacuum pressure-molding in the step S2 is carried out under a vacuum degree of-0.1 MPa to-0.05 MPa, at a temperature of 80 ℃ to 100 ℃ and for a pressing time of 2 to 3 hours.
10. The preparation method of the broadband wave-absorbing material according to claim 8, wherein the mixing ratio of the high-resistance carbon paste ink and the low-resistance carbon paste ink in the step S1 is (1-8): 1-7).
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