The dissertation is aimed at the development of scientific foundations and concepts for obtaining radio-transparent ceramic materials based on the RO – Al2O3 – SiO2 (RO – SrО, BaО) system and researching their electrodynamic and operational properties.
The object of the study – the processes of sintering and phase formation of ceramic materials with a complex of dielectric properties capable of ensuring maximum transmission of electromagnetic waves in the radio frequency range.
The subject of the study – the physicochemical regularities of formation, properties, phase composition and structure of radiotransparent ceramic materials based on compositions of the RO-Al2O3-SiO2 system (RO = SrО, BaО) and technological parameters of manufacturing protective structures of radio engineering systems of aviation facilities.
The dissertation is dedicated to the solution of a scientific and practical problem - the creation of a technology for manufacturing nose fairings and elements of protective structures of antenna systems of aviation objects using developed radio-transparent ceramic materials that possess a set of specified functional and high operational properties.
The advantages and disadvantages of existing radio-transparent materials and the technology of manufacturing antenna fairings from them are analyzed. The most promising compounds capable of providing low dielectric properties, high heat resistance, thermal and chemical resistance are considered in detail.
Substantiates the choice of oxide compositions for obtaining celsian and slawsonite ceramics. The influence of additives MgO, Cr2O3, ZrSiO4, TiO2, CaCO3, B2O3, MoO3 and the eutectic composition Li2O : SnO2 on the processes of structure and phase formation of celsian ceramics under conditions of reduced synthesis temperature was studied. The effectiveness of the eutectic additive Li2O : SnO2 on the formation and synthesis of the celsian phase in the studied temperature range has been proven.
Optimal technological parameters for the synthesis of celsian and slawsonite (firing temperature, exposure at the maximum temperature) were determined. The rational duration of grinding synthesis products was established based on the results of research on the change in the dispersion of synthesis products during grinding. It was determined that the best indicators of physical and mechanical properties of the developed ceramic materials are obtained in conditions of isothermal aging for 4 hours at a firing temperature of 1350 °C.
The structural and phase features of the obtained ceramics were established by the methods of X-ray phase analysis and scanning electron microscopy: the obtained ceramic materials are highly homogeneous monophase densely sintered. The crystalline phase is represented by dispersed compounds of celsian or slawsonite, which provides a set of specified functional and operational properties.
The developed technologies for the production of nose fairings for the protection of aerial equipment of aviation facilities, obtained radio-transparent ceramic materials based on celsian and slawsonite with specified functional and high operational properties are presented.
Using thermodynamic analysis, the probability of the interaction of the developed ceramics with acidic (Н2SO4, HСl, HNO3) and alkaline (NaОН, Na2CO3) reagents is substantiated, and it is experimentally confirmed that radio-transparent ceramic materials based on celsian and slawsonite have increased chemical resistance to standard alkali solutions (NaОН, Na2CO3) and hydrochloric acid. Taking into account the value of the Gibbs energy, it is shown that nitric acid has a more negative effect on ceramic materials of the specified composition.
Calculations of the parameters of gas dynamics and the stress-strain state of fairings were carried out, based on the developed compositions of celsian and slavsonite ceramics, and it was shown that the fairing made of ceramics of the specified compositions will maintain its integrity in all considered temperature regimes. The melting temperature of the developed ceramics of celsian and slawsonite composition was determined experimentally.
The expediency of manufacturing parts of protective structures of radio-electronic equipment in the missile and aerospace industries according to the developed technological parameters using the obtained radio-transparent ceramic materials with consistently low dielectric and electrodynamic characteristics in the millimeter frequency range of 26-37.5 GHz has been experimentally confirmed.
