RU115127U1 - RADIO-ABSORBING COATING - Google Patents

Abstract

A radio-absorbing coating containing layers of aramid fabric with film heterostructures deposited on it, characterized in that the heterostructure consists of 2-8 layers of amorphous hydrogenated carbon with 3d metal nanoparticles, while the layers in the heterostructures alternate in such a way that the concentration of ferromagnetic nanoparticles in neighboring films layers was different - in one low (0-30 wt.%), in the second high (80-95 wt.%).

Description

The utility model relates to the field of radio electronics, in particular to radio-absorbing materials (RPM) intended for protection against electromagnetic radiation (EMP) in the frequency range from 2 GHz to 100 GHz.

Radar Absorbing Coating (RPP) is intended for:

- solutions to a new level of the problem of electromagnetic compatibility (EMC) in microwave devices;

- reducing the visibility of military equipment in the radio range;

- ensuring the joint operation of several radar and radio transmitting stations on the same vehicle;

- protection of biological objects from electromagnetic radiation in the microwave range;

- equipment anechoic rooms intended for scientific research or production testing.

The general requirements for such absorbing materials, hereinafter radar absorbing coatings (RPP) are to ensure a high level of attenuation of the reflected signal, a wide frequency range of operation, simplicity of design, low specific gravity and thickness of the coating.

Known electromagnetic absorbing material and the method of its manufacture, presented in the patent of Germany No. 2234175, the essence of which is to combine the shielding and heat-insulating properties in one material with the optimal ratio between its density and strength. The material is a granulate consisting of a mixture of carbon and ferrite powder and a binder in the form of glass (silica powder). The manufacturing technology of the material is ceramic; extrusion and casting are used. Absorbing properties in a wide range do not exceed 2 dB, and in a narrow range (up to 5 GHz) they reach 10 dB.

The disadvantages of this analogue include the low absorption capacity, large specific gravity per unit area, exceeding 10 kg / m ² , the complexity of the production technology due to the multicomponent composition and, as a result, uncontrolled composition.

Known electromagnetic absorbing material (RF patent No. 2168740), consisting of a mixture of 0.30-0.45 or 0-55-0.75 molar fractions of strontium titanate and 0.70-0.55 or 0.45-0.25 molar fractions, respectively, of compounds with the general formula BiMO ₃ , where M is selected from the group of elements including chromium, manganese, iron. The material has high values of the real part of the dielectric constant and high dielectric losses in the microwave region. However, the material is not elastic, for effective absorption it must have a significant thickness and can only be used in the form of tiles.

RF patent No. 2107705 describes a radio-absorbing material intended for application to various products of research, medical, domestic and other purposes. The radar absorbing material contains latex-based Elaton synthetic adhesive as a polymer binder, powdered ferrite or carbonyl iron as a magnetic filler in the following ratio of components, wt.%: Elaton synthetic adhesive based on 80-20 latex; powdered ferrite or carbonyl iron 20-80. The material is suitable for application on surfaces of various geometries, however, it has insufficient efficiency of absorption of radio waves.

Known radar absorbing material (US patent N6231794), comprising a first layer of porous elastic material, such as polyurethane, coated with a second layer of porous elastic material with conductive particles distributed therein, for example, graphite powder particles or carbon material particles mixed with metal particles. An elastic radar absorbing material has a thickness of not more than 2.5 mm, however, its mechanical strength is not high enough, which narrows its scope.

RF patent No. 2228565 describes a radar absorbing coating comprising a base of at least one layer of interwoven aramid high-modulus filaments with vacuum sprayed film of hydrogenated carbon with ferromagnetic clusters embedded in it in the following ratio, wt.%: Ferromagnetic clusters 50-80; hydrogenated carbon - the rest.

The disadvantages of this radar absorbing coating include the limitation of the operating frequency from below (from 6 GHz).

Known electromagnetic radar absorbing coating (RF patent No. 2363714) consisting of several layers of a high-modulus aramid fabric with sprayed films of ferrite interspersed with nanoscale clusters of metals Ni and Co and hydrogenated carbon interspersed with nanoscale clusters of metals Ni and Co.

This radio-absorbing coating is a lightweight material that meets the requirements of radio absorption of up to 10 dB in the frequency range 2-40 GHz. The material is resistant to external influences. The technology of its manufacture includes the operation of ion-plasma spraying, is successfully developed and environmentally friendly. The disadvantage of this RPM is the use in the design of ferrite films and a smaller frequency range.

The closest analogue that is selected as a prototype is the design of the RPP, presented in the patent for utility model No. 84161, priority from 12.24.2008.

The disadvantages of this RPM are the use of a large number of layers of thin films to create transparency windows, as well as a reflection coefficient modulus of less than 10 dB.

The purpose of the claimed utility model is to create a technology for the production of radar absorbing coatings with an extended frequency range (2-100 GHz) and increased absorption efficiency (≤10 dB) while reducing coating thickness (<2.5 mm) and reduced specific gravity (<1.5 kg / m ² ) by reducing the number of tissue layers.

The problem is achieved in that the radar absorbing coating consists of 2-5 layers of heterostructures deposited on aramid fiber substrates by ion-plasma magnetron sputtering bonded together with a radiolucent material. The film heterostructure consists of several layers of hydrogenated carbon films with 3d metal nanoparticles.

Heterostructures contain from 2 to 8 layers of films with a concentration gradient of amorphous hydrogenated carbon and 3d metal nanoparticles between the layers.

The content of 3d-metal particles in the film varies from 0 wt.% To 95 wt.% Depending on the spraying mode provides smooth matching of wave impedances of the layers along the coating thickness, starting from the upper layer (matching with free space), to the last absorbing layer. For this, the layers in heterostructures alternate so that the concentration of ferromagnetic clusters in the films of neighboring layers is different - in one low (0-30 wt.%), In the second high (80-95 wt.%).

The radar absorbing material is obtained by a method including vacuum sputtering of targets from graphite and 3d metals (Ni, Co) in an argon-hydrogen medium.

As a radiolucent material, an adhesive composition based on a rubber or epoxy mixture can be used.

Microwave absorption was studied in the frequency range 2-100 GHz for the case of normally incident electromagnetic (EM) radiation. The real and imaginary parts of the dielectric constant (ε ', ε' ') and the loss coefficients of the EM wave upon reflection (R) were determined: R = -10 · log (WR / W) dB, where W, WR are the powers of the incident and reflected waves, respectively . In order to absorb EM radiation by a granular structure, it is necessary to have large values of ε "and, as well as the wave impedance Z = [(µ '+ iµ' ') / (ε' + iε '')] 1/2 should be close to unity. As was established by the authors, the claimed coating has large values of ε ', ε' '.

The proposed utility model is illustrated by:

Figure 1 - design of the heterostructure

Figure 2-figure 6 - frequency dependence of the modulus of the reflection coefficient of the EM wave from the RPP, respectively given in examples 1-5.

Figure 1 shows an illustration of a thin-film heterostructure in cross section, where 1 is an intertwined aramid fiber, 2 is an amorphous hydrogenated carbon film with 3d metal particles, 3 is an amorphous hydrogenated carbon film without 3d metal particles, 4 is 3d metal nanoparticles.

Examples of execution:

Example No. 1

The radar absorbing coating was made in the form of a 4 μm thick heterostructure consisting of 8 layers of films of amorphous hydrogenated carbon with 3d metal (Ni) nanoparticles deposited on an aramid fabric substrate. The change in the concentration of 3d metal between the layers of heterostructures ranged from 0 wt.% To 95 wt.%. The deposition process was carried out with a content of 80% Ar and 20% H ₂ in the working gas at a working pressure of 10 mTorr in the chamber, an ion current density of 10 ^-1 A / cm ² , a pallet speed of 30 mm / s, and a film growth rate of 20 nm / min

The measurement results of the reflection coefficient module, specific gravity and coating thickness are presented in the table.

Example No. 2

The radar absorbing coating was made of 2 layers of aramid fabric with heterostructures sprayed onto them, glued together with a radio-transparent material. Heterostructures with a thickness of 4 μm consisted of 8 layers of films of amorphous hydrogenated carbon with nanoparticles of 3d metal (Ni) of various compositions. The change in the concentrations of 3d metal between the layers of heterostructures varied from 1 wt.% To 95 wt.% Depending on the deposition mode. The deposition process was carried out with a content of 80% Ar and 20% H ₂ in the working gas at a working pressure of 10 mTorr in the chamber, an ion current density of 10 ^-1 A / cm ² , a pallet speed of 30 mm / s, and a film growth rate of 20 nm / min

The measurement results of the reflection coefficient module, specific gravity and coating thickness are presented in the table.

Example No. 3

The radar absorbing coating was made in the form of 2 layers of aramid fabric with heterostructures sprayed onto them, glued together with a radiolucent material. Heterostructures with a thickness of 4 μm consisted of 4 layers of films of amorphous hydrogenated carbon with nanoparticles of 3d metal (Ni) of various compositions. The change in the concentrations of 3d metal between the layers of heterostructures varied from 1 wt.% To 95 wt.% Depending on the deposition mode. The deposition process was carried out at a content of 80% Ar and 20% H ₂ in the working gas at a working pressure of 10 mTorr in the chamber, an ion current density of 10 ^-1 A / cm ² , a pallet speed of 30 mm / s, and a film growth rate of 20 nm / min

The measurement results of the reflection coefficient module, specific gravity and coating thickness are presented in the table.

Example No. 4

The radar absorbing coating was made in the form of 4 layers of aramid fabric with heterostructures sprayed onto them, glued together with a radiolucent material. Heterostructures with a thickness of 4 μm consisted of 4 layers of films of amorphous hydrogenated carbon with nanoparticles of 3d metal (Ni) of various compositions. The change in the concentrations of 3d metal between the layers of heterostructures varied from 1 wt.% To 95 wt.% Depending on the deposition mode. The deposition process was carried out at a content of 80% Ar and 20% H ₂ in the working gas at a working pressure of 10 mTorr in the chamber, an ion current density of 10 ^-1 A / cm ² , a pallet speed of 30 mm / s, and a film growth rate of 20 nm / min

The measurement results of the reflection coefficient module, specific gravity and coating thickness are presented in the table.

Example No. 5

The radar absorbing coating was made in the form of 2 layers of aramid fabric with heterostructures sprayed on them and 3 layers of aramid fabric with a single-film structure, glued together with a radio-transparent material. Heterostructures with a thickness of 4 μm consisted of 8 layers of films of amorphous hydrogenated carbon with nanoparticles of 3d metal (Ni) of various compositions. The thickness of the heterostructure is 4 μm, the film thickness of amorphous hydrogenated carbon with 3d metal (Ni) nanoparticles is 0.5 μm. The change in the concentrations of 3d metal between the layers of heterostructures varied from 0 wt.% To 95 wt.% Depending on the deposition mode. The deposition process was carried out at a content of 80% Ar and 20% H ₂ in the working gas at a working pressure of 10 mTorr in the chamber, an ion current density of 10 ^-1 A / cm ² , a pallet speed of 30 mm / s, and a film growth rate of 20 nm / min

The measurement results of the reflection coefficient module, specific gravity and coating thickness are presented in the table.

Table. The results of measurements of the modulus of reflection coefficient, thickness and reduced specific gravity Example No. Frequency Range, GHz Modulus of reflection coefficient, dB RPM thickness, mm Specific gravity, kg / m ² one 2-100 -5-18 0.2 0.2 2 2-100 -5-15 0.5 0.2 3 2-100 -8-22 0.5 0.4 four 2-100 -10-30 1,1 0.6 5 2-100 -12-30 2.1 1,0

Claims (1)

A radar absorbing coating containing layers of aramid fabric with film heterostructures deposited on it, characterized in that the heterostructure consists of 2-8 layers of amorphous hydrogenated carbon with 3d metal nanoparticles, while the layers in the heterostructures alternate so that the concentration of ferromagnetic nanoparticles in the films of neighboring layers was different - in one low (0-30 wt.%), in the second high (80-95 wt.%).