Radio-Absorbing Materials Based on Polymer Composites and Their Application to Solving the Problems of Electromagnetic Compatibility

Abstract

Recently, designers of electronic equipment have paid special attention to the issue of electromagnetic compatibility (EMC) of devices with their own components and assemblies. This is due to the high sensitivity of semiconductor microcircuits to electromagnetic interference. This interference can be caused either by natural phenomena, such as lightning strikes, or by technical processes, such as transients in circuits during fast periodic or random switching. Either way, interference implies a sudden change in voltage or current in a circuit, which is undesirable, whether it propagates along a cable or is transmitted as an electromagnetic wave. The purpose of this article is to review the works devoted to the development, creation, and investigation of modern polymeric nanocomposite materials used for shielding electromagnetic radiation and their effective application for solving problems of electromagnetic compatibility. Additionally, the approach to design EMI shielding complex media with predetermined parameters based on investigation of various properties of possible components is shown. In the review, all polymer composites are classified according to the type of filler. The issues of the interaction of a polymer with conductive fillers, the influence of the concentration of fillers and their location inside the matrix, and the structure of the nanocomposite on the mechanisms of electromagnetic interaction are considered. Particular attention is paid to a new generation of nanocomposite materials with widely adjustable electrical and magnetic properties. A wide class of modern filled polymeric materials with dielectric and magneto-dielectric losses is considered. These materials make it possible to create effective absorbers of electromagnetic waves that provide a low level of reflection coefficient in the microwave range. The model mechanisms for shielding electromagnetic radiation are considered in the paper. A detailed review of the electro-physical properties of polymer nanocomposites is provided. Multilayer electrodynamic media containing combinations of layers of filled polymer composite materials with nanoparticles of different compositions and manufactured using a single technology will make it possible to create electrodynamic media and coatings with the required electro-physical characteristics of absorption, transmission, and reflection. Within the framework of the two-layer coating model, the difference in the effects of the interaction of electromagnetic radiation with conductive layers located on a dielectric and metal substrate is demonstrated. It is shown that in order to achieve optimal (maximum) values of reflection and absorption of electromagnetic radiation in the appropriate frequency range, it is necessary to fit the appropriate layer thicknesses, specific conductivity, and permittivity. Such approach allows designers to create new shielding materials that can effectively vary the shielding, absorbing, and matching characteristics of coatings over a wide frequency band. In general, it can be said that the development of innovative polymer composite materials for shielding electronic devices from electromagnetic interference and excessive electromagnetic background is still an important task. Its solution will ensure the safe and uninterrupted operation of modern digital electronics and can be used for other applications.

Keywords: electromagnetic compatibility; materials with controlled electro-physical characteristics; nanoparticles; polymer nanocomposites; radio-absorbing materials and coatings.

Figure 1

Interaction of an electromagnetic wave with a screen.

Figure 2

Scheme of nanoparticles stabilization inside a matrix stabilizer.

Figure 3

Scheme of a circuit for resistivity measurement. Adapted from [129] with permission.

Figure 4

Dependence of the sample Fe-03 resistance on time at various operating voltages: 1—10 V; 2—100 V; 3—1000 V. Adapted from [129] with permission.

Figure 5

Current-voltage characteristic of a metal polymer based on a polyethylene matrix with iron nanoparticles (about 20 wt. %).

Figure 6

Dependence of resistivity on molybdenum particle concentration C_Mo in a polyethylene matrix.

Figure 7

Dependence of resistivity on concentration of NiFe₂O₄ nanoparticles for tablets 0.25 mm thick (squares) and 1.5 mm thick (circles) [151].

Figure 8

Scheme of the setup for permittivity ε measurement.

Figure 9

The dependence of the permittivity ε of composite nanomaterial on the mass concentration of Mo in HPPE: 1, at a frequency of 1 kHz; 2, at a frequency of 1 MHz. Adapted from [146] with permission.

Figure 10

Dependence of dielectric permittivity ε on concentration of NiFe₂O₄ nanoparticlesat a frequency of 1 kHz (squares), 1 MHz (circles), and 1 GHz (triangles) [151].

Figure 11

Standing waves in a short-circuited waveguide (upper) and in a short-circuited waveguide with a sample located in it (lower). Adapted from [129] with permission.

Figure 12

Scheme of the setup for the study of dielectrics in the microwave range using a measuring line. Adapted from [129] with permission.

Figure 13

The scheme of inclusion of the sample.

Figure 14

The dependence of the dielectric permittivity of the samples Fe-01 (1), Fe-02 (2), and Fe-03 (3) on the operating frequency. Adapted from [129] with permission.

Figure 15

The dependence of the radio absorption of the samples Fe-01 (1), Fe-02 (2), and Fe-03 (3) on the operating frequency. Adapted from [129] with permission.

Figure 16

The scheme of a tunable coaxial resonator with an end capacitive gap.

Figure 17

An equivalent scheme of a resonator used.

Figure 18

The scheme of an experimental setup for measuring ε and tanh(δ) in a coaxial resonator with an end gap.

Figure 19

Dependence of dielectric permittivity (a) and dielectric losses (b) of nanocomposites on concentration of the nanoparticles Fe, Bi, NiFe₂O₄, and Mo.

Figure 20

Electrical scheme of a vibrating magnetometer: PS is a electromagnet power supply with a polarity switch; HS is a Hall sensor; E is an electromagnet; MC are the measuring coils; AK is a coil for measuring amplitude; PM is a permanent magnet; G is a generator; SD is a synchro detector; V1 and V2 are the voltmeters; O is a sample.

Figure 21

Experimental dependencies of magnetization M on magnetic field H for a sample containing 5 mass. % γ-Fe₂O₃ in a polyethylene matrix at a temperature of 293 K. The dotted line and dotted line with dots correspond to paramagnetism and ferromagnetism, respectively. Adapted from [181] with permission.

Figure 22

Hysteresis loop of a sample containing 5 mass. % of iron-containing nanoparticles in the volume of the polyethylene matrix: the initial sample (1) and demagnetization loops for air-heated samples at (2) 29 °C, (3) 240 °C, (4) 260 °C, and (5) 195 °C.

Figure 23

Demagnetization curves of the samples (σ (emu/g); H (kOe)) (a) and dependence of σ_S (emu/g) on concentration of NiFe₂O₄ nanoparticles (b) [151].

Figure 24

Photo of the experimental setup.

Figure 25

Magnetization curves of test samples: (a) Al, curve 1 (circles); Zn, curve 2 (squares); (b) Ho₂Ti₂O₇.

Figure 26

Magnetization curves of nanocomposites of the following compositions: (1) HPPE + 10% Cu; (2) HPPE + 10% Pb; (3) HPPE + 40% CeO₂; (4) HPPE + 20% CeO₂; (5) HPPE + 40% CdS.

Figure 27

The scheme of the setup for measuring attenuation. (1) attenuator, (2) adapter, (3) incident wave DC, (4) measured object, (5) transmitted wave DC, and (6) matched load.

Figure 28

The scheme of the setup for measuring standing wave ratio: (1) attenuator, (2) adapter, (3) incident wave DC, (4) reflected wave DC, and (5) measured object (reference load).

Figure 29

Photograph of a measuring stand with a horn measuring cell.

Figure 30

Scheme of power balance in the interaction of EMR with the sample.

Figure 31

Dependence of (a) the reflection coefficients and (b) the specific radio absorption of samples on the mass concentration of iron in the composite.

Figure 32

(a) Radio absorption and (b) reflection coefficients of composite materials based on metal-containing nanoparticles.

Figure 33

Scheme of the formation of a two-layer combination of samples: (1) base sample Co-03 and (2) additional sample.

Figure 34

(a) Attenuation coefficient and (b) reflection coefficients of two-layer combinations of samples of composite materials based on metal-containing nanoparticles.

Figure 35

Dependence of specific radio absorption (1) and reflection coefficient (2) on concentration of nickel ferrite nanoparticles [151].

Figure 36

The dependences of the reflection R, transmission T, and absorption Q coefficients on the electrical conductivity of the composite layer on (a) metal substrate with electrical conductivity σ_m = 10⁷ (Ohm × m)⁻¹ and (b) ceramic substrate with ε_c = 10 at the different incident radiation frequencies of 300 GHz (dashed line), 30 GHz (solid line), and 3 GHz (dotted line).

Figure 37

The dependencies of the reflection coefficients R (solid line) and absorption coefficients Q (dotted line) on the composite layer thickness d. Composite layer on a Cu substrate (a) without an intermediate layer, (b) with dielectric (ε = 50) intermediate layer with a thickness of 5 mm, and (c) with dielectric (ε = 50) intermediate layer with a thickness of 10 mm.

Figure 38

Scheme of a three-layer composite coating in a short-circuited path. (1) and (2) are the absorbing composite layer; (3) is the underlying dielectric layer. The arrow shows the direction of an incident wave.

Figure 39

The reflection losses of various variants of three-layer coatings. As for the underlying dielectric layer with ε ≈ 4–10, the composition of the filler was varied, such as (a) no filler, (b) BaTiO₃, (c) BaTiO₃ + CG, and (d) BaTiO₃ + AMAG.