Broadband wave-absorbing and heat-insulating material based on gradient impedance gradient and preparation method of broadband wave-absorbing and heat-insulating material

Abstract

The invention provides a broadband wave-absorbing thermal insulation material based on gradient impedance gradual change, which comprises a plurality of absorbing units arranged in a matrix mode, each absorbing unit comprises a thermal insulation layer, a flexible wave-absorbing substrate layer and a gradient gradual change structure distributed on the flexible wave-absorbing substrate layer, and the gradient gradual change structure comprises a plurality of wave-absorbing mechanisms. Each wave-absorbing mechanism comprises at least one flexible wave-absorbing layer, the electromagnetic parameters of the flexible wave-absorbing layers of the same wave-absorbing mechanism are the same, and the electromagnetic parameters of the flexible wave-absorbing layers of different wave-absorbing mechanisms are gradually reduced from bottom to top; the size of the flexible wave absorbing layer distributed on the heat insulation layer is gradually reduced from bottom to top. The invention also provides a preparation method of the broadband wave-absorbing and heat-insulating material. According to the invention, the reflectivity of C, X and Ku wavebands can be regulated and controlled by adjusting electromagnetic parameters and the size and thickness of the gradient structure. The device has the advantages of adjustable broadband, insensitive incident angle polarization, infrared heat insulation, long-term stability and high bearing capacity.

Description

Technical field:

[0001] The present invention belongs to the technical field of microwave-infrared compatible camouflage, and relates to a wave-absorbing heat-insulating material, and in particular to a broadband wave-absorbing heat-insulating material based on a gradient impedance gradual change and a preparation method thereof. Background technology:

[0002] The continuous innovation and development of various military reconnaissance methods are driving the expansion of electronic surveillance equipment from visible light to wider electromagnetic wave ranges such as microwave range. The emergence of multi-spectral compatible stealth technology has enabled camouflage technology to move from defense to offense, from passive to active. In particular, microwave-infrared compatible stealth technology enables military equipment to avoid danger and seamless reconnaissance signals within the beyond-visual-range range, thereby greatly improving its survivability and combat effectiveness. Among them, designing compatible camouflage materials that can simultaneously cope with microwave-infrared detection systems is the key foundation.

[0003] Traditional microwave absorbing materials have problems such as narrow bandwidth, weak carrying capacity, and short service life. Moreover, with the advancement of detection technology, the effectiveness of single-band microwave camouflage is weakening, and the demand for infrared camouflage materials is growing. Traditional metal materials with infrared camouflage characteristics exhibit significant electromagnetic wave reflectivity, making the target easy to be detected by radar systems. Therefore, how to make the electromagnetic wave characteristics of microwaves and infrared compatible and achieve multi-band camouflage is a difficult problem that needs to be solved urgently. The strategies currently developed by researchers for broadband microwave absorption mainly involve composite sandwich structures, resistive films, and metal pattern superstructures. However, the control frequency bands of these absorbing materials are limited, and there is impedance mismatch. Therefore, the present invention provides a broadband absorbing and heat-insulating material based on a gradient impedance gradient and a preparation method thereof to solve the above problems. Summary of the invention:

[0004] The purpose of the present invention is to address the deficiencies in the prior art and to provide a broadband absorbing and heat-insulating material based on a gradient impedance gradient and a preparation method thereof. The present invention aims to solve the problems of narrow absorption bandwidth of traditional materials and failure of single-band camouflage technology through an assembly strategy of a gradient structure and a heat-insulating layer, and to achieve microwave-infrared compatible camouflage.

[0005] The present invention adopts the following technical solutions:

[0006] (I) The present invention provides a broadband absorbing and heat-insulating material based on a gradient impedance gradient, which has the following characteristics: it comprises a plurality of absorbing units arranged in a matrix; each absorbing unit comprises a heat-insulating layer and a gradient gradient structure distributed on the heat-insulating layer; the gradient gradient structure comprises a plurality of absorbing mechanisms, each absorbing mechanism comprises at least one flexible absorbing layer; the flexible absorbing layers of the same absorbing mechanism have the same electromagnetic parameters; the flexible absorbing layers of different absorbing mechanisms have electromagnetic parameters that decrease from bottom to top, forming an impedance change trend; the flexible absorbing layers distributed on the heat-insulating layer decrease in size from bottom to top, corresponding to electromagnetic waves of different wavelengths.

[0007] Furthermore, the flexible absorbing layer is prepared by mixing an elastomer, an absorbing material and a curing agent, the mass ratio of the absorbing material to the elastomer is (1-2):(1-2), and the ratio of the elastomer to the curing agent is 10:1; the proportion of absorbing material added in the flexible absorbing layer with different electromagnetic parameters is different.

[0008] Furthermore, a flexible absorbing base layer is arranged between the thermal insulation layer and the gradient structure. The shape and plane size of the flexible absorbing base layer are the same as those of the thermal insulation layer, and the thickness is adjustable. The flexible absorbing base layer is prepared by mixing an elastomer, an absorbing material and a curing agent. The flexible absorbing base layer has the same electromagnetic parameters as the flexible absorbing layer distributed on the bottom layer.

[0009] Furthermore, the absorbing material is a magnetic absorber; the elastomer is a viscous stretchable elastomer; and the thermal insulation layer is a flexible and porous thermal insulation foam.

[0010] Furthermore, the absorbing material is a micron-level flake carbonyl iron, the diameter of which is about 6 μm; the elastomer is polydimethylsiloxane; the heat insulation layer is a 150 kg / m 3 High temperature resistant and heat insulating polyimide foam.

[0011] Furthermore, the absorption units are periodically arranged in an n×n array.

[0012] Furthermore, the cross section of the thermal insulation layer is rectangular, and the cross section of the flexible absorbing layer is circular, that is, the flexible absorbing layer has a cylindrical structure and its thickness can be adjusted; the diameter of the flexible absorbing layer is smaller than the width of the thermal insulation layer, and the diameter of each flexible absorbing layer gradually increases from top to bottom.

[0013] Furthermore, the gradient structure includes three absorbing mechanisms, wherein the absorbing mechanism distributed in the bottom layer includes two flexible absorbing layers, and the mass ratio of the absorbing material to the elastomer is 2:1; the absorbing mechanism distributed in the middle layer includes two flexible absorbing layers, and the mass ratio of the absorbing material to the elastomer is 1:1; the absorbing mechanism distributed in the upper layer includes two flexible absorbing layers, and the mass ratio of the absorbing material to the elastomer is 1:2.

[0014] Furthermore, in the flexible absorbing base layer, the mass ratio of the absorbing material to the elastomer is 2:1.

[0015] Furthermore, the heat insulation layer 4 has a length L of 45 mm, a width L of 45 mm, and a thickness (H p ) is 1-8mm; the flexible absorbing substrate layer 5 is 45mm long L, 45mm wide L, and has a thickness (H t ) is 1-3mm. Among the 6 flexible absorbing layers from bottom to top, the radius R of the first flexible absorbing layer is 20mm and the thickness is H 1 =1-2mm; the radius of the second flexible absorbing layer is 17mm and the thickness is H 0 =1-2mm; the radius of the third layer of flexible absorbing layer is 14mm and the thickness is H 0 =1-2mm; the radius of the fourth layer of flexible absorbing layer is 11mm and the thickness is H 0 =1-2mm; the radius of the fifth layer of flexible absorbing layer is 8mm and the thickness is H 0 =1-2mm; the radius of the sixth layer of flexible absorbing layer is 5mm and the thickness is H 0 =1-2mm.

[0016] (II) The present invention also provides a method for preparing the broadband wave absorbing and heat insulating material based on the gradient impedance gradual change method described above, comprising the following steps:

[0017] Step 1: Evenly mix the elastomer and the absorbing material in different proportions, and then pour them into a pre-made polytetrafluoroethylene mold, and demould them after drying to obtain multiple flexible absorbing layers;

[0018] Step 3: stacking the flexible absorbing layer on the flexible absorbing base layer according to the arrangement order, and pasting them through an elastic matrix to obtain an absorbing unit with a gradient structure;

[0019] Step 3: Arrange the absorption units in a matrix, assemble them with the thermal insulation layer, and stick them together through an elastomer matrix to obtain a broadband wave-absorbing thermal insulation material based on a gradient impedance gradient.

[0020] Beneficial effects of the present invention:

[0021] The present invention provides a broadband wave-absorbing heat-insulating material based on gradient impedance gradual change and a preparation method thereof, wherein a flexible elastomer matrix and a magnetic absorber are mixed to prepare a wave-absorbing heat-insulating structure with adjustable absorption frequency, and the electromagnetic parameters are adjusted by changing the mass mixing ratio of the elastomer matrix and the magnetic absorber to form a wave-absorbing structure with gradual impedance gradient change. At the same time, the wave-absorbing heat-insulating material of the present invention has the characteristics of broadband adjustability, thermal insulation, stability and strong bearing capacity.

[0022] Specifically, when electromagnetic waves are incident, the reflectivity of C, X and Ku bands can be regulated by adjusting the electromagnetic parameters and the size and thickness of the gradient structure, and the reflectivity of the absorbing and heat-insulating structure of the present invention can reach below -10dB in the range of 5-18GHz; at the same time, the material of the present invention exhibits the characteristic of being insensitive to the polarization of the incident angle. In addition, under an infrared heat source of 100°C, the apparent temperature of the absorbing and heat-insulating material is reduced by about 50°C, and it exhibits the characteristics of long-term stability. Description of the drawings:

[0023] Figure 1 It is a schematic diagram of the three-dimensional structure, two-dimensional top view and cross-sectional structure of the heat insulation layer and the absorption unit of the broadband wave-absorbing heat insulation material based on the gradient impedance gradual change of the present invention;

[0024] Figure 2 It is a schematic diagram of the arrangement of absorption units of the broadband wave-absorbing and heat-insulating material based on the gradient impedance gradual change type of the present invention;

[0025] Figure 3 is a reflectivity test curve diagram of embodiments 1 to 4 of the present invention;

[0026] Figure 4 are thermal infrared images of Example 1 of the present invention and Comparative Example 1 at 100° C.;

[0027] Figure 5 It is a curve diagram of apparent temperature change of Example 1 of the present invention and Comparative Example 1 within 60 minutes. Specific implementation method:

[0028] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0029] Example 1

[0030] Reference Figures 1-2 An embodiment of the present invention provides a broadband wave-absorbing heat-insulating material based on gradient impedance gradient, including 16 absorption units arranged in a matrix, the 16 absorption units are periodically arranged in a 4×4 array, each absorption unit includes a heat insulation layer 4 and a gradient gradient structure distributed on the heat insulation layer 4, and the heat insulation layer 4 of the 16 absorption units forms an integrated structure.

[0031] The gradient structure includes three groups of absorbing mechanisms distributed up and down, namely, absorbing mechanism 1, absorbing mechanism 2 and absorbing mechanism 3, and each group of absorbing mechanisms includes two flexible absorbing layers. The electromagnetic parameters of the two flexible absorbing layers of the same absorbing mechanism are the same, and the electromagnetic parameters of the flexible absorbing layers of different absorbing mechanisms decrease from bottom to top, that is, the electromagnetic parameters of the two flexible absorbing layers of absorbing mechanism 3, the two flexible absorbing layers of absorbing mechanism 2 and the two flexible absorbing layers of absorbing mechanism 1 gradually decrease, forming an impedance change trend. All flexible absorbing layers (6 flexible absorbing layers) distributed on the insulation layer 4 decrease in size from bottom to top, corresponding to electromagnetic waves of different wavelengths, such as Figure 1 shown.

[0032] As a further preferred embodiment of the present invention, the flexible absorbing layer is prepared by mixing an elastomer, an absorbing material and a curing agent, and the proportion of absorbing material added in the flexible absorbing layers with different electromagnetic parameters is different. Specifically, in this embodiment, the mass ratio of the absorbing material to the elastomer of the two flexible absorbing layers of the absorbing mechanism 3 distributed in the bottom layer is 2:1; the mass ratio of the absorbing material to the elastomer of the two flexible absorbing layers of the absorbing mechanism 2 distributed in the middle layer is 1:1; the mass ratio of the absorbing material to the elastomer of the two flexible absorbing layers of the absorbing mechanism 1 distributed in the upper layer is 1:2. The three flexible absorbing layers with different electromagnetic parameters are assembled into a gradient structure.

[0033] As a further preferred embodiment of the present invention, a flexible wave-absorbing substrate layer 5 is provided between the heat-insulating layer 4 and the gradient structure. Figure 1 As shown, the shape and plane size of the flexible absorbing substrate 5 are the same as those of the heat insulating layer 4, and its thickness is adjustable. The flexible absorbing substrate 5 is prepared by mixing an elastomer, an absorbing material and a curing agent. The flexible absorbing substrate 5 has the same electromagnetic parameters as the flexible absorbing layer distributed at the bottom layer, and the mass ratio of the absorbing material to the elastomer is 2:1, and the ratio of the elastomer to the curing agent is 10:1.

[0034] As a further preferred embodiment of the present invention, the heat insulation layer 4 has a rectangular cross section and a thickness (H p The flexible absorbing substrate 5 is a rectangle with the same length and width as the heat insulation layer 4, and the cross section of the flexible absorbing layer is circular, that is, the flexible absorbing layer is a cylindrical structure with a thickness (H t The diameter of the flexible wave-absorbing layer is smaller than the width of the heat-insulating layer 4, and the diameter of each flexible wave-absorbing layer increases gradually from top to bottom.

[0035] In this embodiment, Figure 1 As shown, the length L of the heat insulation layer 4 is 45 mm, the width L is 45 mm, and the thickness (H p ) is 1 mm (in other embodiments of the present invention, H pThe flexible absorbing substrate 5 has a length L of 45 mm, a width L of 45 mm, and a thickness (H t ) is 1.0mm. Among the 6 flexible absorbing layers from bottom to top, the radius R of the first flexible absorbing layer is 20mm and the thickness is H 1 =2mm; the radius of the second flexible absorbing layer is Rw (w = 3mm) and the thickness is H 0 =1mm; the radius of the third layer of flexible absorbing layer is R-2w, and the thickness is H 0 =1mm; the radius of the fourth layer of flexible absorbing layer is R-3w, and the thickness is H 0 =1mm; the radius of the fifth layer of flexible absorbing layer is R-4w, and the thickness is H 0 =1mm; the radius of the sixth flexible absorbing layer is R-5w, and the thickness is H 0 =1mm.

[0036] In this embodiment, the absorbing material is a micrometer-level flake carbonyl iron, and the diameter of the carbonyl iron is about 6 μm, and the bulk density is about 1.2 g / cm 3 The elastic body is polydimethylsiloxane. The heat insulation layer 4 is selected to have a density of 150kg / m 3 High temperature resistant and heat insulating polyimide foam.

[0037] The method for preparing a broadband wave absorbing and heat insulating material based on a gradient impedance gradual change type of the present invention comprises the following steps:

[0038] Step 1: Take different masses of flaky carbonyl iron powder, add it to the polydimethylsiloxane viscous matrix, add the curing agent, and then use an electric stirrer to mechanically stir for 30 minutes to obtain a uniformly dispersed carbonyl iron powder-elastomer mixture. The mass ratios of the carbonyl iron powder-elastomer mixture are 1:2, 1:1 and 2:1 respectively.

[0039] A carbonyl iron powder-elastomer mixture with a mass ratio of 1:2 is first poured into a pre-made polytetrafluoroethylene mold to obtain two flexible absorbing layers of the absorbing mechanism 1; after being placed in an oven at 60°C and dried for 40 minutes, a carbonyl iron powder-elastomer mixture with a mass ratio of 1:1 is continued to be poured into the mold to obtain two flexible absorbing layers of the absorbing mechanism 2; after being placed in an oven at 60°C and dried for 60 minutes, a carbonyl iron powder-elastomer mixture with a mass ratio of 2:1 is continued to be poured into the mold to obtain two flexible absorbing layers of the absorbing mechanism 3; after being completely dried, demolding is performed to obtain a gradient structure.

[0040] Step 2: Transfer the gradient structure to different thickness H t On the rectangular flexible absorbing substrate 5, the mass ratio of the carbonyl iron powder-elastomer mixture in the flexible absorbing substrate 5 is 2:1, and it is pasted by coating a thin layer of transparent elastomer matrix.

[0041] Step 3: Arrange the absorption units in a 4×4 matrix and assemble them with the bottom polyimide insulation foam layer, and connect them in the middle through a transparent elastomer matrix to obtain a gradient impedance gradient broadband wave absorbing insulation structure. After assembly, the overall length is 180mm, the width is 180mm, the overall height is between 8mm and 18mm, and the horizontal distance between the central axes of adjacent absorption unit structures is 45mm.

[0042] Example 2

[0043] This embodiment is basically the same as Embodiment 1, except that:

[0044] In this embodiment, the flexible absorbing substrate 5 has a length L of 45 mm, a width L of 45 mm, and a thickness (H t ) is 1.5mm.

[0045] Example 3

[0046] This embodiment is basically the same as Embodiment 1, except that:

[0047] In this embodiment, the flexible absorbing substrate 5 has a length L of 45 mm, a width L of 45 mm, and a thickness (H t ) is 2.5mm.

[0048] Example 4

[0049] This embodiment is basically the same as Embodiment 1, except that:

[0050] In this embodiment, the flexible absorbing substrate 5 has a length L of 45 mm, a width L of 45 mm, and a thickness (H t ) is 3.0mm.

[0051] Comparative Example 1

[0052] Comparative Example 1 is substantially the same as Example 1, except that no heat insulating layer is provided in Comparative Example 1.

[0053] Performance Test:

[0054] 1. The dielectric parameter test of the broadband wave-absorbing and heat-insulating material based on the gradient impedance gradient prepared in Example 1 was carried out. The test showed that the dielectric real part ε of the two flexible wave-absorbing layers of the wave-absorbing mechanism 1 was ′ The dielectric real part ε of the two flexible absorbing layers of the absorbing mechanism 2 varies between 4.0 and 5.0. ′ The dielectric real part ε of the two flexible absorbing layers of the absorbing mechanism 3 varies between 6.4 and 7.2. ′The impedance gradient structure is formed according to the change of electromagnetic parameters, and the reflectivity of the overall absorption unit is adjusted. The present invention can adjust the electromagnetic parameters by changing the mass mixing ratio of the absorbing material and the elastomer to form an absorbing structure with a gradient impedance.

[0055] 2. The broadband wave absorbing and heat insulating structures prepared in Examples 1 to 4 were tested on a bow frame constructed by a vector network analyzer. The reflectivity curves are shown in FIG. Figure 3 As shown. Figure 3 It can be seen that at different thicknesses H t Under the condition of 1.0mm thickness, the reflectivity of the gradient structure varies between 4 and 18GHz. More specifically, as the thickness increases, the reflectivity curve gradually moves to low frequencies, with the characteristics of wide-band tunability. When the thickness is 1.0mm, the absorption bandwidth of less than -10dB covers 5-18GHz (C, X and Ku bands); at 17.14GHz, its reflectivity is -24.74dB.

[0056] 3. The broadband wave absorbing heat insulation structure prepared in Example 1 and Comparative Example 1 were photographed by a thermal infrared camera on a hot stage at 100°C, and the infrared images with and without the heat insulation foam insulation layer were compared. Figure 4 As shown. The left side is a gradient absorption structure without a thermal insulation foam layer, and the right side is a structure with a thermal insulation foam layer. It is obvious that as time changes, the apparent temperature of the structure on the left gradually increases, and the rate of temperature increase is much higher than that of the structure on the right. Figure 5 It was found that the temperature change curve on the left (SP1) reached above 70°C at 5 minutes; the temperature change curve on the right (SP2) reached about 48°C at 5 minutes, and the apparent temperature did not change significantly over time, and finally stabilized at about 50°C.

[0057] The present invention can also change the thickness of the thermal insulation foam layer (H p ) and density, absorbing unit structural parameters (R, w, H 0 etc.) to further adjust the absorption bandwidth and thermal insulation effect to meet the needs of low-frequency thermal insulation.

[0058] Due to the gradient structure design, the present invention can stimulate multiple resonances and edge diffractions, and generate more absorption peaks to expand the absorption bandwidth. At the same time, the porous foam structure with good thermal insulation performance is used to reduce the surface temperature of the object and reduce the emission of infrared radiation. Compared with traditional single-band absorption materials, the present invention introduces an elastomer matrix into a gradient gradual structure system, and realizes impedance gradual change through electromagnetic parameter adjustment, thereby achieving a broadband absorption effect. At the same time, the gradient structure of the present invention also has the characteristics of broadband adjustability, incident angle polarization insensitivity, infrared heat insulation, long-term stability and strong bearing capacity.

[0059] In the present invention, unless otherwise specified, the scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. In addition, the reagents, materials and operating procedures used herein are reagents, materials and conventional procedures widely used in the corresponding fields.

[0060] The above are only preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments, or replace some of the technical features by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A broadband wave absorbing and heat insulating material based on gradient impedance gradual change, characterized in that: It includes a plurality of absorption units arranged in a matrix; Each absorption unit includes a heat insulation layer and a gradient structure distributed on the heat insulation layer; The gradient structure includes a plurality of wave absorbing mechanisms, each of which includes at least one flexible wave absorbing layer; The electromagnetic parameters of the flexible absorbing layer of the same absorbing mechanism are the same; The electromagnetic parameters of flexible absorbing layers with different absorbing mechanisms decrease from bottom to top; The flexible wave-absorbing layers distributed on the heat-insulating layer decrease in size from bottom to top.

2. The broadband wave absorbing and heat insulating material based on gradient impedance gradual change according to claim 1 is characterized in that: The flexible absorbing layer is prepared by mixing an elastomer, an absorbing material and a curing agent, wherein the mass ratio of the absorbing material to the elastomer is (1-2):(1-2), and the ratio of the elastomer to the curing agent is 10:1; The proportion of absorbing material added in the flexible absorbing layer with different electromagnetic parameters is different.

3. The broadband wave absorbing and heat insulating material based on gradient impedance gradual change according to claim 2 is characterized in that: A flexible absorbing substrate layer is disposed between the thermal insulation layer and the gradient structure, and the shape and plane size of the flexible absorbing substrate layer are the same as those of the thermal insulation layer; The flexible absorbing substrate layer is prepared by mixing an elastomer, an absorbing material and a curing agent, and the flexible absorbing substrate layer has the same electromagnetic parameters as the flexible absorbing layer distributed on the bottom layer.

4. The broadband wave absorbing and heat insulating material based on gradient impedance gradual change according to claim 1 is characterized in that: The absorbing material is a magnetic absorber; The elastomer is a stretchable elastomer with viscosity; The heat insulating layer is a flexible and porous heat insulating foam.

5. The broadband wave absorbing and heat insulating material based on gradient impedance gradual change according to claim 4 is characterized in that: The absorbing material is micrometer-level flake carbonyl iron; The elastomer is polydimethylsiloxane; The thermal insulation layer has a density of 150 kg / m 3 Polyimide foam.

6. The broadband wave absorbing and heat insulating material based on gradient impedance gradual change according to claim 1 is characterized in that: The absorption units are periodically arranged in an n×n array.

7. The broadband wave absorbing and heat insulating material based on gradient impedance gradual change according to claim 1 is characterized in that: The cross section of the heat insulation layer is rectangular, and the cross section of the flexible wave absorbing layer is circular; The diameter of the flexible wave-absorbing layer is smaller than the width of the heat-insulating layer, and the diameter of each flexible wave-absorbing layer increases gradually from top to bottom.

8. The broadband wave absorbing and heat insulating material based on gradient impedance gradual change according to claim 2 is characterized in that: The gradient structure includes three wave absorbing mechanisms, among which: The absorbing mechanism distributed on the bottom layer includes two flexible absorbing layers, and the mass ratio of the absorbing material to the elastomer is 2:1; The absorbing mechanism distributed in the middle layer includes two flexible absorbing layers, and the mass ratio of the absorbing material to the elastomer is 1:1; The absorbing mechanism distributed in the upper layer includes two flexible absorbing layers, and the mass ratio of the absorbing material to the elastomer is 1:

2.

9. The broadband wave absorbing and heat insulating material based on gradient impedance gradual change according to claim 3 is characterized in that: In the flexible absorbing substrate layer, the mass ratio of the absorbing material to the elastomer is 2:

1.

10. The method for preparing the broadband wave absorbing and heat insulating material based on gradient impedance gradual change according to claim 3, characterized in that: The following steps are involved: Step 1: Evenly mix the elastomer and the absorbing material in different proportions, and then pour them into a pre-made polytetrafluoroethylene mold, and demould them after drying to obtain multiple flexible absorbing layers; Step 3: stacking the flexible absorbing layer on the flexible absorbing base layer according to the arrangement order, and pasting them through an elastic matrix to obtain an absorbing unit with a gradient structure; Step 3: Arrange the absorption units in a matrix, assemble them with the thermal insulation layer, and stick them together through an elastomer matrix to obtain a broadband wave-absorbing thermal insulation material based on a gradient impedance gradient.

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