This paper presents an experimental study on the performance of shielding concrete with additives of magnetite nanoparticles. Two concretes with magnetite additives as well as one based concrete were tested. In order to achieve the high-performance concrete, all concrete mixes had a constant water/cement ratio of 0.45. In order to measure the mechanical properties, concrete samples were made in accordance with dimension such as 40 × 40 × 160 mm. But, for measurement of protective properties the concrete was made in accordance with dimension of rotary antennas such as 400 × 400 mm with a thickness of 10 mm. The nanoparticles Fe 3 O 4 were synthesized by chemical condensation method. XRD have shown the presence of cubic structure of Fe 3 O 4 spinel with crystallite size is equal to 130.0 Å. The TEM microphotograph shows that the Fe 3 O 4 nanoparticles are spherical, the range of sizes is 12-30 nm. The magnetic retardation suggests that the magnetite nanoparticles have superparamagnetic properties. This is explained by the fact that under the influence of external magnetic field, they are single-domain, in other words, they become uniformly magnetized throughout the volume. The additives of magnetite nanoparticles at a concentration of 0.5% mass have not a negative effect on flexural strength. The samples with additives of magnetite nanoparticles showed better shielding of microwave radiation in the frequency range from 0.7 GHz to 13 GHz. The maximum efficiency of suppression of electromagnetic disturbance is equal to 19.9 dB at a frequency of 1.5 GHz with a thickness of 10 mm.
The results of substantiation of the improved technology for manufacturing of the frequency-selective electromagnetic shields are presented. The improvement of this technology was ensured by the following: 1) the inclusion of elements in the form of classical Archimedes spirals, formed from foil materials, into the volume of manufactured shields to ensure the frequency-selective properties of such shields; 2) fixing the specified elements in the volume of manufactured shields by thermal pressing. The indicated features determine the main advantage of the improved technology in comparison with its analogues — lower time costs required for its implementation. The substantiation of the improved technology was implemented in the following areas: 1) setting the parameters of Spiral elements, which correspond to the maximum values of energy losses of the electromagnetic radiation interacting with them in the microwave range; 2) determination of the order of arrangement of spiral elements in the volume of the screens, which corresponds to the lowest values of electromagnetic radiation transmission and reflection coefficients in the microwave range of these shields. The substantiation implemented in the first of the indicated directions was based on the results of the analysis of the content of scientific works devoted to mathematical modeling and the study of the electromagnetic radiation of the transmission characteristics of flat spiral antennas in the microwave range. The substantiation implemented in the second of the indicated directions was based on the manufacture of experimental samples of the shields, the volume of which includes spiral elements oriented in a certain way, and further obtaining and comparative analysis of electromagnetic radiation transmission and reflection characteristics in the microwave range of these shields. Shields manufactured in accordance with substantiated improved technology seem to be promising for use in order to protect electronic devices from the effects of electromagnetic interference.
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).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.