Heterogeneous radio absorbing composite materials based on powdered charcoals for electronic devices protection from the electromagnetic radiation impact

Abstract

The results of theoretical and experimental substantiation of the technique developed by the authors for the manufacture of heterogeneous (two- or three-layer) radio absorbing composite materials based on powdered charcoals are presented. The technique is based on layer-by-layer pouring of mixtures of a gypsum binder and powdered charcoal (non-activated birch, activated birch, activated coconut) into molds in the order in which the outer (relative to the electromagnetic radiation propagation front) layer of the composite material is characterized by the lowest wave resistance, and the inner layer is characterized by the highest wave resistance. The specified order is determined by the results of the theoretical substantiation of the developed technique. In the course of its experimental substantiation, regularities for changing the electromagnetic radiation reflection and transmission coefficients values of the manufactured materials depending on the value of the radiation frequency in the range of 0.7–17.0 GHz have been established. Based on the established regularities, it was stated that the minimum value of the electromagnetic radiation reflection coefficient of the two-layer materials manufactured according to the developed and substantiated technique (thickness ~ 5.0 mm) is –12.0 ± 1.0 dB and corresponds to electromagnetic radiation frequencies of 0.8 and 2.6 GHz (it’s provided, when such materials are fixed on metal substrates). The minimum value of the electromagnetic radiation reflection coefficient of the three-layer materials (thickness ~ 10.0 mm) under the specified condition is also –12.0 ± 1.0 dB and corresponds to electromagnetic radiation frequencies of 4.5 and 6.0 GHz. The electromagnetic radiation transmission coefficient values of such materials decrease with an average step of 4.0 dB as the frequency of the radiation increases by 1.0 GHz in the range of 2.0–10.0 GHz and increase with a similar step as the frequency increases by 1.0 GHz in the range of 10.0–17.0 GHz. The minimum value is –30.0 ± 2.0 dB. The materials manufactured according to the developed and substantiated technique seem to be promising for ensuring the protection of electronic devices from the effects of electromagnetic interference (both active and passive types).