Lightweight special-shaped space interference electromagnetic wave material, preparation method and application

Abstract

The application belongs to the technical field of wave-absorbing materials, and discloses a light special-shaped space electromagnetic wave interference material, a preparation method and application, which is a core-shell structure and is composed of a reflection layer, a loss layer and a matching layer arranged in sequence from inside to outside. The reflection layer, the loss layer and the matching layer are all composed of a base material and a wave-absorbing material, the wave-absorbing material is doped in the base material, the base material is foamed polyurethane, the light special-shaped space electromagnetic wave interference material is in a granular shape as a whole, the density is 0.030-0.200 g / cm 3 , and the mass is 0.5-1.5 g / granule. The material has a good interference effect on electromagnetic waves from all directions in space by means of low-temperature blasting of a rocket bomb, directional sowing of a drone and an airplane.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing materials technology, and particularly relates to a lightweight, irregularly shaped spatial electromagnetic wave interference material with porous polyurethane foam as the substrate, its preparation method and application. Background Technology

[0002] With the continuous development of modern technology, electromagnetic waves are being used in more and more fields, from small household appliances such as microwave ovens and mobile phones to large electronic and electrical equipment such as mobile phone communication base stations and military detection radar.

[0003] The military's level of electronic warfare has rapidly increased, with missiles, aircraft, and satellites specifically designed for electronic countermeasures emerging one after another. These systems primarily emit multi-band electromagnetic waves from high altitudes, then receive signals to acquire location and identification information, and rapidly obtain feedback for precision strikes. In the future, electronic defense for electronic countermeasures equipment must adopt a comprehensive approach that can both weaken the effectiveness of enemy weapons and equipment and effectively protect friendly equipment from impact.

[0004] Current electromagnetic wave interference materials mainly consist of solid powder coatings applied to object surfaces or large-area plate-like layers. Their application range is relatively fixed, they cannot achieve active directional interference, and they are unsuitable for interfering with electromagnetic waves in the 500-10000m range. To solve these problems, it is necessary to design a small-volume, flexible material that can interfere with electromagnetic waves from all directions. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a lightweight, irregularly shaped composite material that can interfere with electromagnetic waves in space, and can interfere with electromagnetic waves from all directions in three-dimensional space.

[0006] The technical solution for achieving the objective of this invention is as follows:

[0007] The first aspect of this invention is to provide a lightweight, irregularly shaped spatial interference electromagnetic wave material with a core-shell structure, comprising a reflective layer, a loss layer, and a matching layer arranged sequentially from the inside out. Each of the reflective layer, loss layer, and matching layer is composed of a substrate and an absorbing material, with the absorbing material doped inside the substrate. The substrate is made of foamed polyurethane. The lightweight, irregularly shaped spatial interference electromagnetic wave material is granular in shape and has a density of 0.030-0.200 g / cm³. 3 Each capsule weighs 0.5-1.5g.

[0008] The reflector layer can reflect electromagnetic waves that are not attenuated by the loss layer back to the loss layer, while attenuating some of the electromagnetic waves.

[0009] The loss layer is used to attenuate electromagnetic waves that enter the interior of the material.

[0010] Matching layers are used to reduce the reflection of incident electromagnetic waves on the material surface, allowing them to penetrate into the material.

[0011] Furthermore, the particle shape is a regular or irregular geometric shape, such as a cube, prism, frustum, pyramid, cone, frustum, sphere, or a column with a flower or star-shaped cross-section.

[0012] Furthermore, a first interface layer is disposed between the reflective layer and the loss layer, the first interface layer being composed of one or more absorbing materials. The first interface layer forms a dense layer of absorbing materials, enhancing the composite material's ability to absorb electromagnetic waves.

[0013] Furthermore, a second interface layer is disposed between the loss layer and the matching layer. The second interface layer is composed of one or more absorbing materials. The second interface layer forms a dense layer of absorbing materials, thereby enhancing the loss of electromagnetic waves by the composite material.

[0014] Furthermore, the reflective layer has a thickness of 1-5 mm, the loss layer has a thickness of 1-5 mm, the matching layer has a thickness of 1-2 mm, the first interface layer has a thickness of 0-1 mm, and the second interface layer has a thickness of 0-1 mm.

[0015] Preferably, the reflective layer has a thickness of 1.5-5 mm, the loss layer has a thickness of 1.5-5 mm, and the matching layer has a thickness of 1-2 mm.

[0016] More preferably, the reflective layer has a thickness of 2-4 mm, the loss layer has a thickness of 2-4 mm, and the matching layer has a thickness of 1-2 mm.

[0017] Furthermore, the substrate is a two-component rigid polyurethane foam, and the microwave absorbing material is a microwave absorbing powder material or a microwave absorbing fiber material. Preferably, the two-component rigid polyurethane foam is a mixture of isocyanate and polyether polyol or a mixture of isocyanate and polyester polyol.

[0018] Polyurethane foam has a porous structure, which on the one hand improves its impedance matching characteristics, enabling the material to transmit and absorb electromagnetic waves. On the other hand, the internal cavities and the structure between the cavities also cause scattering and reflection of electromagnetic waves, resulting in significant loss. Furthermore, polyurethane foam itself has a low density, greatly reducing the material's overall density and making lightweighting possible.

[0019] Furthermore, the microwave absorbing powder material is one or more of the following: nano-graphite powder, carbon black, flake graphite, carbon nanotubes, graphene oxide, silicon carbide, polyaniline, polypyrrole, carbonyl iron powder, iron(II,III) oxide, iron(III) oxide, cobalt MOF, nickel MOF, zinc MOF, and COFs; the microwave absorbing fiber material is one or more of the following: carbon fiber, polycrystalline iron fiber, aluminum foil, copper foil, and aluminized glass fiber.

[0020] Preferably, the absorbing material in the reflective layer is composed of 2mm carbon fiber, 4mm carbon fiber, and carbon black in a weight ratio of 0.2-0.5:0.2-0.5:0.1-0.2.

[0021] Preferably, the microwave absorbing material in the loss layer is composed of carbon fiber, carbonyl iron powder, cobalt MOF, and graphene oxide in a weight ratio of 0.1-0.5: 10-30: 0.1-0.5: 0.1-0.5.

[0022] Preferably, the absorbing material in the matching layer is composed of 2mm carbon fiber and polycrystalline iron fiber in a weight ratio of 0.01-0.05:0.01-0.05.

[0023] Preferably, the microwave absorbing material in the first interface layer is composed of flake graphite, ferric oxide and carbon black in a weight ratio of 0.5-1:0.3-0.5:0.5-1.

[0024] Preferably, the microwave absorbing material in the second interface layer is composed of flake graphite, iron oxide, and carbon black in a weight ratio of 0.5-1:0.2-0.5:0.5-1.

[0025] Further, the absorbing material in the reflective layer accounts for 0.1-0.5% of the substrate weight, preferably 0.2-0.5%, more preferably 0.3-0.4%; the absorbing material in the loss layer accounts for 10-31% of the substrate weight, preferably 15-30%, more preferably 20-25%; and the absorbing material in the matching layer accounts for 0.01-0.1% of the substrate weight, preferably 0.02-0.08%, more preferably 0.03-0.06%.

[0026] A second aspect of the present invention provides a method for preparing the above-mentioned lightweight, irregularly shaped spatial interference electromagnetic wave material, characterized by comprising the following steps:

[0027] Step 1: Mix the absorbing material and the substrate in a certain proportion, then foam and expand the mixture to solidify it. After curing, the mixture is then formed into a reflective layer, a loss layer, and a matching layer.

[0028] Step 2: A loss layer is coated on the outside of the reflective layer, and the reflective layer and the loss layer are bonded together through a first interface layer; a matching layer is coated on the outside of the loss layer, and the loss layer and the matching layer are bonded together through a second interface layer, thus forming a lightweight, irregularly shaped space interference electromagnetic wave material.

[0029] Furthermore, various microwave-absorbing powder materials are mixed by ball milling at a speed of 300-500 rpm for 30-60 minutes. The microwave-absorbing fiber materials are then ultrasonically dispersed in an organic solvent at a frequency of 50-70 Hz for 10-30 minutes.

[0030] Furthermore, the curing temperature is 80-120℃, and the curing time is 60-120 minutes. Preferably, the curing temperature is 90-110℃, and the curing time is 60-100 minutes.

[0031] The third aspect of the present invention is to provide the application of the above-mentioned lightweight irregular space interference electromagnetic wave material in interfering with electromagnetic waves in the air at a depth of 500-10000m, by dispersing the material in space through cryogenic explosion of rockets, drones or aircraft.

[0032] The advantages and beneficial effects of this invention are as follows:

[0033] 1. The present invention relates to a lightweight, irregularly shaped space interference electromagnetic wave material. It is lightweight, has controllable overall dimensions, and can be flexibly and diverse in shape design. It has a strong space electromagnetic wave interference capability. Unlike coating materials and plate materials that are coated over a large area, it is small in size and can be directionally dispersed in space by means of cryogenic explosion of rockets, high-altitude delivery by drones or aircraft.

[0034] 2. The material of this invention comprises material layers with different functions. Electromagnetic waves from different directions will enter each layer sequentially, thus ensuring that the material can play an effective role when dispersed in the air. The multi-layer structure improves the shortcomings of the narrow effective absorption bandwidth of single-layer absorbing materials and broadens the effective absorption bandwidth. Combining materials with absorption properties in different wavebands can expand the effective absorption bandwidth. At the same time, the types of absorbing materials in each layer can be designed to improve the absorption performance.

[0035] 3. This invention uses a two-component rigid polyurethane foam material as the matrix. Microwave-absorbing powder or microwave-absorbing fiber is added to the two-component rigid polyurethane foam raw material for foaming and curing. The preparation process is easy to control and relatively stable, which can ensure that the added microwave-absorbing powder or fiber exists in the polyurethane bubble skeleton and is fully mixed inside the polyurethane without falling off.

[0036] 4. This invention uses composite absorbing materials, which can improve the problem of the single loss mechanism of single absorbing materials. It has multiple loss mechanisms and strong loss of electromagnetic waves.

[0037] 5. The material prepared by this invention has a certain mechanical strength and is tightly bonded, and will not deform or be damaged under certain pressure. Attached Figure Description

[0038] Figure 1 Lightweight, irregularly shaped materials for interfering with electromagnetic waves in space;

[0039] Figure 2 A schematic diagram of the internal structure of a lightweight, irregularly shaped material that interferes with electromagnetic waves.

[0040] Figure 3 The interference effect of the materials prepared in Examples 1, 2, 3 and Comparative Example 1 on electromagnetic waves in the range of 2-40 GHz is shown in the figure.

[0041] In the diagram: 1 is the matching layer, 2 is the second interface layer, 3 is the loss layer, 4 is the first interface layer, and 5 is the reflection layer. Detailed Implementation

[0042] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0043] Example 1

[0044] A lightweight, irregularly shaped spatial interference electromagnetic wave material, which is obtained by composite reaction foaming of the following components in parts by mass to obtain each layer of material:

[0045] Matching layer 1: 0.05 parts of 2mm carbon fiber, 0.02 parts of polycrystalline iron fiber, and 100 parts of two-component rigid polyurethane foam;

[0046] First interface layer 4: 1 part flake graphite, 0.3 parts ferric oxide, 1 part carbon black;

[0047] Loss layer 3: 0.3 parts of 2mm carbon fiber, 20 parts of carbonyl iron powder, 0.5 parts of cobalt MOF, 0.1 parts of graphene oxide, and 100 parts of two-component rigid polyurethane foam;

[0048] Second interface layer 2: 1 part flake graphite, 0.2 parts iron oxide, 1 part carbon black;

[0049] Reflective layer 5: 0.2 parts of 2mm carbon fiber, 0.2 parts of 4mm carbon fiber, 0.1 parts of carbon black, and 100 parts of two-component rigid polyurethane foam.

[0050] The preparation method of the above-mentioned electromagnetic wave interference material includes the following steps:

[0051] (1) Flake graphite and carbon black are put into a ball mill for ball milling and mixing to obtain a uniformly mixed microwave absorbing powder. The ball mill speed is 350 rpm and the ball milling time is 30 minutes.

[0052] (2) Mix the uniformly mixed microwave absorbing powder material or microwave absorbing fiber material with the two-component rigid polyurethane foam, stir for 60 seconds, and allow it to foam, expand and solidify.

[0053] (3) Place the polyurethane composite material obtained in step (2) into an oven for curing at a curing temperature of 110°C for 60 minutes to prepare a matching layer, a loss layer and a reflective layer.

[0054] (4) Cut each layer of material into a cubic shape and bond them together according to the following thicknesses to obtain a lightweight irregular spatial interference electromagnetic wave material. Matching layer: 2mm; First interface layer: 1mm; Loss layer: 3mm; Second interface layer: 1mm; Reflection layer: 2mm.

[0055] Performance Testing: Suspension Performance Testing Method: The above-mentioned lightweight, irregularly shaped spatial interference electromagnetic wave material was weighed, its dimensions were measured, its volume was calculated, and its average density was determined. Its free settling velocity was measured at the top of an electrostatic-free plexiglass tube with a diameter of 15cm and a height of 1.5m. The test results showed that the material's side length was 16mm and its density was 0.075g / cm³. 3 The free settling velocity is 2.5 m / s.

[0056] Electromagnetic interference performance testing method: Using a microwave anechoic chamber, the absorption performance of the material in the 2-40 GHz frequency range was tested using a vector network analyzer (model 3671G). The maximum reflection loss of the material was -14.4 dB in the 2-8 GHz frequency range; -13.7 dB in the 8-12 GHz frequency range; -11.9 dB in the 12-18 GHz frequency range; -14.8 dB in the 18-27 GHz frequency range; and -17.8 dB in the 27-40 GHz frequency range.

[0057] Example 2

[0058] The difference from Example 1 is that the cutting thickness of each layer of material is different: matching layer: 1mm; first interface layer: 0mm; loss layer: 5mm; second interface layer: 1mm; reflective layer: 2mm.

[0059] Performance testing:

[0060] Using the same method as in Example 1, the suspension performance and electromagnetic interference performance of the lightweight, irregularly shaped spatial interference electromagnetic wave material provided in the above examples were tested. The test results were as follows: the material's side length is 16 mm, and the average material density is 0.09 g / cm³. 3The settling velocity is 2.7 m / s. The maximum reflection loss of the material is -5 dB in the 2-8 GHz frequency range; -12.8 dB in the 8-12 GHz frequency range; -10.3 dB in the 12-18 GHz frequency range; -4.3 dB in the 18-27 GHz frequency range; and -15.3 dB in the 27-40 GHz frequency range.

[0061] Example 3

[0062] The difference from Example 1 is that the material prepared is in the shape of a hexagonal prism.

[0063] Performance testing

[0064] Using the same method as in Example 1, the suspension performance and wave absorption performance of the lightweight, irregularly shaped spatial interference electromagnetic wave material provided in the above examples were tested. The test results are as follows: the diameter of the circumscribed circle at the bottom edge of the material is 16 mm, the height at the top is 16 mm, and the average density of the material is 0.07 g / cm³. 3 The settling velocity is 2.25 m / s. The maximum reflection loss of the material is -9.4 dB in the 2-8 GHz frequency range; -6.4 dB in the 8-12 GHz frequency range; -6.5 dB in the 12-18 GHz frequency range; -9.8 dB in the 18-27 GHz frequency range; and -19.7 dB in the 27-40 GHz frequency range.

[0065] Comparative Example 1

[0066] The difference from Example 1 is that the material has only a matching layer and the size is 16mm.

[0067] Performance testing

[0068] Using the same method as in Example 1, the suspension performance and wave absorption performance of the lightweight, irregularly shaped spatial interference electromagnetic wave material provided in the comparative example were tested. The test results showed that the average material density was 0.05 g / cm³. 3 The settling velocity is 2.02 m / s. The material's reflection loss is less than -4 dB in the 2-40 GHz frequency range.

[0069] Comparative Example 2

[0070] The difference from Example 1 is that five layers of material are horizontally stacked and combined in the following order: 2mm reflective layer, 2mm first interface layer, 6mm loss layer, 2mm second interface layer, and 4mm matching layer, to form a horizontally layered material with a size of 16mm.

[0071] Performance testing

[0072] Using the same method as in Example 1, the suspension performance and wave absorption performance of the lightweight, irregularly shaped spatial interference electromagnetic wave material provided in the comparative example were tested. The test results showed that the average material density was 0.3 g / cm³. 3 The settling velocity is 2.50 m / s. The material exhibits a reflection loss of less than -3 dB in the 2-40 GHz frequency range, and its effect on electromagnetic waves incident from different directions is unstable.

[0073] Comparative Example 3

[0074] The difference from Example 1 is that the material has only a reflective layer and a loss layer, and the size is 16mm.

[0075] Performance testing

[0076] Using the same method as in Example 1, the suspension performance and wave absorption performance of the lightweight, irregularly shaped spatial interference electromagnetic wave material provided in the comparative example were tested. The test results showed that the average material density was 0.06 g / cm³. 3 The settling velocity is 2 m / s. The material's reflection loss is less than -6 dB in the 2-40 GHz frequency range.

[0077] Comparative Example 4

[0078] The difference from Example 1 is that the material has only a reflective layer and a matching layer, and the size is 16mm.

[0079] Performance testing

[0080] Using the same method as in Example 1, the suspension performance and wave absorption performance of the lightweight, irregularly shaped spatial interference electromagnetic wave material provided in the comparative example were tested. The test results showed that the average material density was 0.06 g / cm³. 3 The settling velocity is 2 m / s. The material's reflection loss is less than -6 dB in the 2-40 GHz frequency range.

[0081] Comparative Example 5

[0082] The difference from Example 1 is that the material has only a loss layer and a matching layer, and the size is 16mm.

[0083] Performance testing

[0084] Using the same method as in Example 1, the suspension performance and wave absorption performance of the lightweight, irregularly shaped spatial interference electromagnetic wave material provided in the comparative example were tested. The test results showed that the average material density was 0.055 g / cm³. 3 The settling velocity is 2.2 m / s. The material's reflection loss is less than -4.5 dB in the 2-40 GHz frequency range.

[0085] Comparative Example 6

[0086] The difference from Example 1 is that the absorbing material components of the matching layer and the loss layer are interchanged.

[0087] Performance testing

[0088] Using the same method as in Example 1, the suspension performance and wave absorption performance of the lightweight, irregularly shaped spatial interference electromagnetic wave material provided in the comparative example were tested. The test results showed that the average material density was 0.09 g / cm³. 3 The settling velocity is 2.7 m / s. The material's reflection loss is less than -10 dB in the 2-40 GHz frequency range.

[0089] Comparative Example 7

[0090] The difference from Example 1 is that the absorbing material components of the matching layer and the reflective layer are interchanged.

[0091] Performance testing

[0092] Using the same method as in Example 1, the suspension performance and wave absorption performance of the lightweight, irregularly shaped spatial interference electromagnetic wave material provided in the comparative example were tested. The test results showed that the average material density was 0.07 g / cm³. 3 The settling velocity is 2.5 m / s. The material's reflection loss is less than -8 dB in the 2-40 GHz frequency range.

[0093] Comparative Example 8

[0094] The difference from Example 1 is that the absorbing material composition of the loss layer and the reflective layer are interchanged.

[0095] Performance testing

[0096] Using the same method as in Example 1, the suspension performance and wave absorption performance of the lightweight, irregularly shaped spatial interference electromagnetic wave material provided in the comparative example were tested. The test results showed that the average material density was 0.04 g / cm³. 3 The settling velocity is 1.98 m / s. The material exhibits a reflection loss of less than -12 dB in the 2-40 GHz frequency range. However, the effective reflection loss bandwidth is less than 5 GHz.

[0097] This invention provides a lightweight, irregularly shaped spatial interference electromagnetic wave material. Figures 1-3 This displays the material's appearance, internal structure, and wave-absorbing effect:

[0098] Figure 1 Schematic diagrams of lightweight, irregularly shaped materials that interfere with electromagnetic waves in space, showing different appearances. Figure 1 It can be seen that the material of this invention can be made into different shapes such as cubes, frustums, cylinders, hexagonal prisms, flower shapes, pyramidal shapes, stars, spheres, cones, and triangular pyramids.

[0099] Figure 2 This is a schematic diagram of a lightweight, irregularly shaped spatial electromagnetic wave interference material with a five-layer cubic structure (one matching layer, one reflecting layer, one loss layer, and two interface layers). Figure 2 As can be seen, taking the cube shape as an example, the internal five-layer structure is sandwiched, with each layer enclosing the other. This allows it to have a certain interference effect on electromagnetic waves from any direction.

[0100] Figure 3 The reflection loss of the materials in Embodiments 1, 2, 3, and Comparative Example 1 of this invention in the 2-40 GHz frequency range was tested in five bands (2-8 GHz, 8-12 GHz, 12-18 GHz, 18-27 GHz, and 27-40 GHz). (See attached...) Figure 3 As can be seen, the cubic structure in Example 1 exhibits good reflection loss across all five frequency bands, with a reflection loss greater than -10dB in each band and a maximum reflection loss of -17.8dB. Example 2 reduces one interface layer and adds a 5mm matching layer to maintain the same material dimensions. The settling velocities are similar, and the reflection loss is less than -5dB in the 18-27GHz frequency band. It also exhibits good reflection loss in the 2-18GHz and 27-40GHz ranges, with maximum reflection losses of -12.8GHz and -15.3dB, respectively. Example 3 maintains the same material dimensions but is fabricated as a hexagonal prism. It exhibits good reflection loss only in the 2-8GHz and 27-40GHz ranges, with a maximum reflection loss of -19.7dB, superior to the cubic structure's -17.8dB. Comparative Example 1 maintains the same material dimensions but changes the internal structure composition, using only one type of matching layer material, resulting in very low reflection loss across all five frequency bands. This demonstrates that, with the same material dimensions, a 5-layer structure exhibits a wider electromagnetic wave attenuation band, and different shapes have varying effects on electromagnetic wave interference across different frequency ranges. A single-layer structure results in poor material interference performance.

[0101] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept, and these all fall within the protection scope of the present invention.

Claims

1. Use of lightweight anisotropic spatial interference electromagnetic wave material for interference with electromagnetic waves in the air at a distance of 500-10000 m, characterised by that, The material is dispersed in space by low-temperature explosion of a rocket projectile, unmanned aerial vehicle or aircraft scattering; The light-shaped space interference electromagnetic wave material is a core-shell structure, which is composed of a reflection layer, a loss layer and a matching layer arranged from inside to outside, the reflection layer, the loss layer and the matching layer are all composed of a base material and a wave-absorbing material, the wave-absorbing material is doped in the base material, the base material is foamed polyurethane, the light-shaped space interference electromagnetic wave material is in a granular shape as a whole, the density is 0.030-0.200 g / cm 3 , and the mass is 0.5-1.5 g / grain. A first interface layer is arranged between the reflection layer and the loss layer, and the first interface layer is composed of one or more than two wave-absorbing materials; A second interface layer is arranged between the loss layer and the matching layer, and the second interface layer is composed of one or more than two wave-absorbing materials; The base material is a two-component hard foamed polyurethane, and the wave-absorbing material is a wave-absorbing powder material or a wave-absorbing fiber material; The wave-absorbing powder material is one or more than two of nano-graphite powder, carbon black, flaky graphite, carbon nanotubes, graphene oxide, silicon carbide, polyaniline, polypyrrole, carbonyl iron powder, ferroferric oxide, diiron trioxide, cobalt MOF, nickel MOF, zinc MOF, and COFs material; and the wave-absorbing fiber material is one or more than two of carbon fiber, polycrystalline iron fiber, and aluminized glass fiber. The wave-absorbing material in the reflection layer accounts for 0.1-0.5% of the weight of the base material, the wave-absorbing material in the loss layer accounts for 10-31% of the weight of the base material, and the wave-absorbing material in the matching layer accounts for 0.01-0.1% of the weight of the base material. The preparation method of the light-shaped space electromagnetic wave interference material includes the following steps: Step one, mix the wave-absorbing material and the base material according to the proportion, then foam, expand, and solidify, and then mature to form the reflection layer, the loss layer, and the matching layer; Step two, coat the loss layer outside the reflection layer, and the reflection layer and the loss layer are adhered through the first interface layer; coat the matching layer outside the loss layer, and the loss layer and the matching layer are adhered through the second interface layer, to form the light-shaped space electromagnetic wave interference material.

2. Use according to claim 1, characterized in that, The particle shape is regular or irregular geometric body.

3. Use according to claim 1, characterized in that, The thickness of the reflection layer is 1-5mm, the thickness of the loss layer is 1-5mm, the thickness of the matching layer is 1-2mm, the thickness of the first interface layer is 0-1mm excluding 0, and the thickness of the second interface layer is 0-1mm excluding 0.

Images