Biruk Y. Protection of workers from exposure to electromagnetic fields using liquid shielding materials

Biruk Y.I. Protection of workers from exposure to electromagnetic fields using liquid shielding materials. Dissertation for the degree of Doctor of Philosophy in the field of knowledge 26 – "Civil Security", specialty 263 – "Civil Security" Kyiv National University of Civil Engineering and Architecture, Kyiv, 2023. The dissertation work is dedicated to solving the scientific and practical task of improving the electromagnetic safety of workers by determining the conditions under which liquid shielding materials show their maximum effectiveness, as well as the development and implementation of liquid-based materials and technologies that effectively shield electromagnetic fields in a wide range of frequencies. The existing methods of ensuring the electromagnetic safety of workers are analyzed. It was determined that the most effective means of protecting people from electromagnetic influences is electromagnetic field shielding. The main requirements for protective materials are high coefficients of general shielding, low coefficients of reflection of electromagnetic waves, acceptable mass-dimensional parameters and suitability for facing surfaces of large areas and complex configurations. The protective properties of liquid materials against the influence of electromagnetic fields in a wide frequency range have been developed and investigated. The advantages of such mixtures are the ability to provide the necessary coefficients of absorption and reflection of electromagnetic waves. This made it possible to adjust the composition and number of layers to obtain the material parameters necessary in a specific electromagnetic environment to ensure stable operation of wireless communication devices. A study was conducted on the justification of the development of technologies. The scientific novelty of the work is that:  for the first time, the use of iron ore concentrate as a shielding substance of liquid protective mixtures based on standard paint products was substantiated. This made it possible to obtain ultrahigh-frequency electromagnetic field shielding coefficients from 1.3 to 7.9 with a weight content of iron ore concentrate of 30–60%; industrial frequency magnetic field up to 5.7; industrial frequency electric field up to 8.6;  for the first time, the manufacturing technology was substantiated, the protective properties of shielding materials of the gradient type based on liquid compositions were obtained and tested. This made it possible to obtain ultra-high frequency electromagnetic field shielding coefficients of 6.2–6.3 for a two-layer coating and 11–12 for a three-layer coating;  the methodological and technological principles of creating liquid compositions have been improved. Adding flaky graphite with a weight content of 5% to the iron ore concentrate allows to increase the shielding coefficients of the ultra-high frequency electromagnetic field by 48–50%, the industrial frequency electric field by 38–40%;  calculation methods for determining the protective properties of composite protective liquid materials have gained further development, which allows predicting the shielding coefficients depending on the amplitude-frequency characteristics of the shielded electromagnetic fields with the weight content of the shielding filler in the dielectric matrix. The practical significance of the obtained results is confirmed by patents for a useful model. Patent 149126 Ukraine IPC 2021.01, G12В 17/00, G12В 17/02 (2006.01). The method of manufacturing an electromagnetic screen with a gradient of electrophysical properties. Patent 153982 Ukraine IPC 2023.01, G12B 17/00 G12B 17/02. The method of manufacturing a gradient composite electromagnetic screen. The testing of the developed liquid materials was carried out in the certified laboratory for the study and standardization of physical factors of the production environment of the State Institution «Kundiiev Institute of Occupational Health of the National Academy of Medical Sciences of Ukraine». The test results coincide with the results of the dissertation research within the measurement error. The results of the research were implemented in the educational process at KNUCA in the teaching of physics to students of the specialty 192 "Construction and civil engineering" and the training of graduate students in the specialty 263 "Civil safety". Keywords: electromagnetic field, shielding, shielding coefficient, reflection coefficient, worker protection, liquid composite materials, electromagnetic safety.