S.B. Bibikov, O.N. Smolnikova, M.V. Prokof’ef
The article is devoted to the studying of electrophysical properties of radioabsorbing materials of resistive type with carbon coverings on a substrate from polyurethane foam (PPU) which are applied at the decision of problems of electromagnetic compatibility. The influence of the structure of PPU and parameters of the carbon cover on the properties of conductive porous composite material has been considered.
The samples of the porous conductive composite materials have been made using a method of impregnation of PPU of the colloidal graphite water solutions preparations received at various conditions of the grinding and activation of disperse carbon particles.
The samples of porous conductive composite materials have produced by impregnating of PPU with aqueous solutions of colloid-graphite preparations which was obtained under different conditions of milling and activation of dispersed carbon particles.
The materials being investigated are described by the methods of the electronic scanning microscopy. The analysis of conditions of formation of a continuous conductive covering on a surface of pores polyurethane foam was carried out and there was shown an influence of the machining on structure carbon cover.
Measurements of the radio characteristics of flat samples of the conductive composite materials using waveguide lines and free space techniques in the microwave range have been made. In a frequencies range from 2 up to 39 GHz spectra of complex dielectric permeability of materials with the various content of a carbon phase, as well as for the samples of the conductive composite materials after additional mechanical treatment, have been received.
It is shown that the dispersion of dielectric permeability porous conductive composite materials is well described by the model of a relaxation polarization with a resistive part included parallelly. The factor of an estimation of heterogeneity of materials being investigated in the work was entered. The decreasing of the complex dielectric permeability of foam materials with a colloidal graphite cover under mechanical influence has been established.
Using the model of polarization of the porous conductive composite materials the electrophysical parameters of materials (high-frequency limit and dispersion depth of the dielectric permeability, time and spread parameter of relaxation, dc-conductivity) were determined. It was established that the thickness of a graphite cover calculated on model under discussion reaches values about 3 microns.
An example of the using of the calculated model parameters for the extrapolation of complex dielectric permeability in the expanded frequency range less than 1 GHz that allows predicting the properties and to construct the ultrawideband radioabsorbing materials.