RU2529494C2 - Multi-layered composite material for protection against electromagnetic radiation - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to means for protection against electromagnetic fields of electrotechnical and electronic devices and biological objects and can be applied for creation of electromagnetic screens and echo-free chambers. Composite material for protection against electromagnetic radiation consists of polymer base with distributed in it particles of alloy of system Fe-Cu-Nb-Si-B, and is characterised by the fact that it represents multi-layered construction, each layer of which is made of said composition, and content of alloy particles in each layer constitutes 70-90 wt % and is limited by certain range of size of particles from continuous line 1-200 mcm with increase of particle dimensions in each following layer.

EFFECT: increase of working range of material frequencies from 100 MHz to 10 GHz with preservation of low values of reflection coefficient and high values of magnetic permeability.

3 cl, 1 tbl, 2 dwg, 2 ex

Description

Composite material relates to protective equipment against variable electromagnetic fields in the microwave range and can be used to ensure electromagnetic compatibility of electrical and electronic devices, create anechoic chambers for high-precision measurements, reduce the visibility of military objects, and also to protect biological objects from the negative effects of increased electromagnetic fields.

The creation of radio-absorbing screens is an important direction in the development of modern technology, they are used in various fields of human activity, including in the electronic, electrical and military industries. The frequency range of devices that require the use of radar absorbing materials is constantly increasing, and, accordingly, the requirements for such materials in the range of operating frequencies are growing while maintaining weight and overall characteristics. Often, it is also required to further reduce the weight and thickness of the material due to the miniaturization of electronic devices and the improvement of military equipment.

According to sources [1, 2], the material providing the smallest reflection coefficient of the electromagnetic wave should have both magnetic and dielectric characteristics. In the ideal case, so that the equality To _otr = 0 is fulfilled, the necessary condition is the equality ε ′ = µ ′, where ε ′ and µ ′ are the real parts of the dielectric and magnetic permeabilities of the material, respectively. This condition follows from the formulas given in the sources [1, 2]:

where w is the wave resistance of the material. If the material has a finite thickness, then the wave resistance is calculated as follows:

where ε = ε′-iε ″ is the dielectric constant of the material;

µ = µ′-iµ ″ - magnetic permeability of the material;

d is the thickness of the material;

λ is the wavelength of electromagnetic radiation.

One way to solve the problem of creating a radar absorbing material having both magnetic and dielectric properties is to obtain a composite material that includes components, each of which has one of these properties. According to the source [3], filler particles with a size from λ / 4 to λ / 2 are most effective for operation at a given frequency.

Moreover, the thickness of the material is also important to ensure effective radio absorption. According to the source [4], the material with a thickness of the order of λ / 20, where λ is the wavelength of the absorbed radiation, will possess the most effective radar absorbing properties, all other things being equal.

At present, multilayer composite radar absorbing materials based on a polymer matrix with high dielectric constant and various magnetic and electrically conductive fillers are known (5, 6, 7). However, these materials have a drawback in the form of a narrow range of operating frequencies, due to the presence of each component of the filler has its own specific resonant frequency, at which the radio absorption is most effective. And as a result, the disadvantage of a large number of different components added to the material, which complicates and increases the cost of obtaining composite material. In addition, in the patent of the Russian Federation No. 2453953 due to the alleged metal substrate included in the composition of the material, the specific gravity of the composite material increases sharply.

A composite material (8) based on a polymer matrix and particles of a nanocrystalline Fe-Si-Nb-Cu-B alloy or Co-Fe-Ni-Cu-Nb-Si-B alloy from 1 to 100 μm in size was selected as a prototype . In this invention, the absorption of electromagnetic radiation in the microwave range is carried out using one filler instead of several. The effect of absorption of radiation in a wide range of frequencies is due to different-sized filler particles.

According to the source [9], the magnetic characteristics of the powders depend to a large extent on the particle size. Ultimately, each range of the fractional composition of the powders in the resonant mode determines the protection efficiency in a certain frequency spectrum.

However, in the patent adopted for the prototype, we can only talk about the integral effect, determined by the wide fractional composition of the particles, which does not allow the creation of composite protective materials operating in a predetermined frequency range. Therefore, a prerequisite for creating a composite protective material is its work in the resonant frequency ranges.

The technical result of the invention is to increase the operating frequency range of the composite material from 100 MHz to 10 GHz, at which most modern electronic devices, including cell phones, microprocessor systems and radar stations, operate with a reflection coefficient of not more than -10 dB.

The technical result is achieved due to the fact that the composite material for protection against electromagnetic radiation, consisting of a polymer base with particles of an alloy of the Fe-Cu-Nb-Si-B system distributed in it, in accordance with the invention, is a multilayer structure, each layer of which is made from the specified composition, and the content of alloy particles in each layer is 70-90 wt.% and is limited to a certain range of particle sizes from a continuous row of 1-200 μm with an increase in particle size in each subsequent layer.

In particular, the composite material may consist of layers AE with the following ranges of particle sizes of the alloy in each of the layers:

Layer A - 1-15 microns;

Layer B - 15-35 microns;

Layer C - 35-50 microns;

Layer B - 50-100 microns;

Layer E - 100-200 microns.

In addition, the thickness of each of the layers AE varies in the following ranges:

Layer A - 0.1-0.5 mm;

Layer B - 0.5-1.0 mm;

Layer C - 1.0-5.0 mm;

Layer D - 5.0-10.0 mm;

Layer E - 10.0-30.0 mm.

It was experimentally established that the desired effect is achieved when the content of particles in each layer, starting from 70 wt.%. When the content of particles is more than 90 wt.%, A sharp decrease in the strength of the material is observed, therefore, the optimal content of particles in each layer is 70-90 wt.%.

The use of particles with a size of 1-200 microns in the composite material allows to achieve the optimal effect, as it provides a reflection coefficient of not more than - 10 dB in the frequency range from 100 MHz to 10 GHz. A further increase in particle size leads to an increase in the total reflection coefficient of the material in this frequency range due to the plate shape of the particles.

Calculations show that to absorb electromagnetic radiation of a certain frequency, it is necessary to use a filler of a certain fractional composition.

Due to the plate-like shape, larger particles have greater reflectivity, increasing with increasing frequency, so it is necessary to place the layers in this composite material in the order of continuous increase in particle size in order to ensure maximum absorption of electromagnetic radiation in the volume of the material.

To achieve the maximum effect of absorption of electromagnetic radiation, it is also necessary to select the thickness of each layer based on the values of the radiation frequency at which the radio absorption in this layer is planned. As already noted above, the material with a thickness of the order of λ / 20 will have the best radar absorbing properties, ceteris paribus. According to this, for the material to work in the claimed frequency range, it is necessary to provide the following thicknesses of the layers of the composite material:

Layer A - 0.1-0.5 mm;

Layer B - 0.5-1.0 mm;

Layer C - 1.0-5.0 mm;

Layer D - 5.0-10.0 mm;

Layer E - 10.0-30.0 mm.

This design of the composite material allows you to control the range of operating frequencies and the absorption efficiency of electromagnetic waves by creating a multilayer composition, each layer of which, having a certain mass fraction of ferromagnetic dispersed material of a certain fraction in the dielectric matrix, allows you to absorb radiation in a resonant mode in a predetermined frequency range.

The integrated effect in the interaction of all layers of the composite with the incident electromagnetic wave, firstly, increases the absorption efficiency and, secondly, extends the range of operating frequencies.

A composite material with such a structure provides satisfactory absorption of electromagnetic waves in the frequency range from 100 MHz to 10 GHz.

Figure 1 presents a comparison of the integral effect of the filler fractional composition from 1 to 200 microns and the effects of fillers, divided into fractions of certain ranges. The fractional composition is determined experimentally for each frequency. Moreover, the integral effect is always lower than the resonance one.

Figure 2 presents a multilayer composite material consisting of layers AE, where 1 is the polymer base of the layers, 2 are particles of an alloy of the Fe-Cu-Nb-Si-B system.

AMAG-200 alloy is used as a ferromagnetic dispersed filler.

Powders of a predetermined fraction are obtained by high-speed grinding of an amorphous or nanocrystalline tape with a width of 20 mm and a thickness of 20-30 microns in a plant of the Desi-11 type. Sieving of powders is carried out using a classifier such as IG-6UN. The preparation of a metal-polymer mixture for each layer is carried out on special mixers according to a standard technique.

The combination of single-layer composites in a multilayer structure is carried out using special collander, providing the required mechanical strength of the composition.

Measurement of the reflection coefficient K _Neg monolayer and multilayer compositions is carried out on the installation type Agilent E8363B PNA under the typical procedure.

Examples of the implementation of the claimed invention are presented in table 1.

Table 1 Example 1 Example 2 Polymer base OPGS silicone polymer silicone polymer grade EKP-102B Layer thickness, mm BUT 0.3 ± 0.1 0.4 ± 0.1 AT 0.7 ± 0.2 0.8 ± 0.2 FROM 4 ± 1 3 ± 1 D 8 ± 1 7 ± 1 E 12 ± 1 13 ± 1 Fractional composition of the layers, microns BUT 11 ± 3 6 ± 3 AT 19 ± 3 30 ± 3 FROM 39 ± 3 45 ± 3 D 55 ± 3 90 ± 3 E 105 ± 3 190 ± 3 Mass fraction of particles in the layers, wt.% 70 90 K _neg , dB Frequency from 2 GHz to 6 GHz - no more - 13; Frequency from 500 MHz to 3 GHz - no more than - 15; Frequency from 100 MHz to 2 GHz and from 6 GHz to 10 GHz - no more than - 10. Frequency from 100 MHz to 500 MHz and from 3 GHz to 10 GHz - no more than - 10.

Information sources

1. B.Z. Katsenelenbaum. High-frequency electrodynamics. M .: Nauka, 1966

2. B.F. Alimin. "Modern developments of absorbers of electromagnetic waves and radar absorbing materials." Foreign electronics, No. 2, 1989, S. 75-82.

3. Ufimtsev P.Ya. The method of boundary waves in the physical theory of diffraction. M .: Soviet Radio, 1962, 243 p.

4. K.N. Rozanov. “A fundamental limitation on the width of the working range of radar absorbing coatings.” Radio engineering and electronics. 1999. - T. 44, No. 5. - S.526-530.

5. RF patent No. 2234176 (C2) of 08/07/2002, publ. 08/10/2004

6. RF patent No. 2453953 (C1) dated 06/14/2011, publ. 06/20/2012

7. Patent of the Republic of Kazakhstan No. 27772520 (B1) dated 12/11/1997, publ. 01/14/2000

8. RF patent №2324989 from 06/19/2006, publ. 05/20/2008 - The prototype.

9.K.M. Lim, K.A. Lee, M.C. Kim, C.G. Park ″ Complex permeability and electromagnetic wave absorption properties of amorphous alloy-epoxy composites ″ // Journal of Non-Crystalline Solids 351 (2005) 75-83.

Claims (3)

1. Composite material for protection against electromagnetic radiation, consisting of a polymer base with particles of an alloy of the Fe-Cu-Nb-Si-B system distributed in it, characterized in that it is a multilayer structure, each layer of which is made of the specified composition, and the content of alloy particles in each layer is 70-90 wt.% and is limited to a certain range of particle sizes from a continuous row of 1-200 microns with an increase in particle size in each subsequent layer. 2. The composite material according to claim 1, characterized in that the multilayer structure consists of layers AE with the following ranges of particle sizes of the alloy in each of the layers:
Layer A - 1-15 microns;
Layer B - 15-35 microns;
Layer C - 35-50 microns;
Layer D - 50-100 microns;
Layer E - 100-200 microns. 3. The composite material according to claim 2, characterized in that the thickness of each of the layers AE varies in the following ranges:
Layer A - 0.1-0.5 mm;
Layer B - 0.5-1.0 mm;
Layer C - 1.0-5.0 mm;
Layer D - 5.0-10.0 mm;
Layer E - 10.0-30.0 mm.

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