METHODS AND MEANS OF INCREASING THE EFFICIENCY OF COMPOSITE MATERIALS FOR SHIELDING ELECTROMAGNETIC FIELDS

Abstract

The main principles of increasing the shielding coefficients of electromagnetic fields by composite materials are considered. It is shown that the protective properties in the low-frequency and high-frequency regions of the electromagnetic spectrum are provided by different physical mechanisms. Therefore, to ensure acceptable protective properties, it is necessary to coordinate the ratio of electrophysical and magnetic properties of materials based on compromise solutions. The main condition in the process of designing materials is to take into account the strong frequency dependence of the dielectric and magnetic permeability of filler particles. To predict the required volume content of the shielding filler in the dielectric matrix, it is possible to use the Maxwell-Garnett, Odelevsky, and Lorentz formulas. At the same time, it should be taken into account that the differences between calculated and experimental results are at least 20 %. For simultaneous effective shielding of ultra-low-frequency and ultra-high-frequency electromagnetic fields, the material must have both sufficient magnetic properties and acceptable electrical conductivity. This can be achieved by treating the original mixture containing ferromagnetic particles with a constant magnetic field of 200–300 A/m. By arranging the arrangement of shielding particles in the body of the composite, conduction circles are formed. With a shielding material content of 12–16 % by volume, a percolation effect is achieved - a sharp increase in the electrical conductivity of the material and an increase in protective properties. The amount of filler depends not only on the total volume, but also on the size of individual particles. In this way, simultaneous shielding of both the magnetic component of the industrial frequency electromagnetic field and ultrahigh and higher frequency electromagnetic fields is achieved. It is shown that it is expedient to investigate the possibility of arranging non-magnetic particles in the body of the composite by treating the initial mixture with an electric field.