The dissertation is aimed at developing chemical and material compositions and creating the physicochemical foundations of energy-saving technology for producing radio-transparent ceramic materials of cordierite and celsian composition with controlled microstructure and phase composition, which possess a set of special properties and are used for high-precision missile weapons.
The expediency of using cordierite and celsian ceramic materials for the production of radio-transparent products for high-precision missile weaponry has been substantiated. The main methods of producing glass-ceramic materials and the processes of intensifying sintering and strengthening ceramics have been described.
The choice of glass binders for ultra-high-frequency radio-transparent ceramics based on cordierite and celsian has been substantiated. Compositions of relatively low-melting glasses (melting temperature not higher than 1400°C) have been developed in the pseudo-ternary systems Li2O – Al2O3 – SiO2, MgO – Al2O3 – SiO2 and BaO – Al2O3 – SiO2 with a constant B2O3 content (10 wt. parts over 100 wt. %) for subsequent use as components in the production of densely sintered radio-transparent ceramics of cordierite and celsian compositions.
The influence of spodumene glass composition (LABS) on the sintering processes of cordierite and celsian materials, as well as the formation of crystalline phases of α-cordierite and monoclinic celsian at reduced temperatures, has been investigated. It has been established that the introduction of spodumene glass composition contributes to a decrease in the sintering temperature to 1300-1350°C, while simultaneously increasing the physicotechnical indicators. Fine-grained crystallization of the β-spodumene phase from the initial LABS glass contributes to a significant decrease in the coefficient of linear thermal expansion (CLTE) of the cordierite-based ceramic material as a whole to (12.4-17.8)∙10-7 °C-1, and the celsian-based ceramic material to (23.5-24.8)∙10-7 °C-1, which ensures high thermal stability of the ceramics up to 950°C and 900°C, respectively. The developed materials also meet the requirements for dielectric properties for use in ultra-high frequency electromagnetic fields.
The features of the reactions of cordierite formation at invariant points of the MgO – Al2O3 – SiO2 system have been studied. The only product of the reaction of the components of glasses M-1 and M-5 with sublayer components is cordierite. The correlation between the physical and technical properties of cordierite ceramics and the technological parameters of its production (sintering temperature, content of MABS glass) is established. The most rational compositions of cordierite ceramics, from the viewpoint of achieving a set of high technical and operational characteristics, are determined. These compositions contain the developed MABS glass M-1 in the amount of 30–35 wt.% and allow sintering at a low temperature of 1300°C. The combination of high physical and technical properties (zero water absorption and open porosity, σbd = 294–314 MPa, ε = 4,3, tgδ = 0,001) makes the developed cordierite ceramics suitable for use as ultra-high-frequency radio-transparent materials for aviation and missile technology, particularly for nose antenna fairings of radio-controlled missiles.
For celsian ceramics, the conditions for the formation of the phase at the eutectic points of the BaO – Al2O3 – SiO2 system have been studied. It has been found that barium orthosilicate interacts most actively with sublayer components to form the celsian phase. The introduction of BABS glass in an amount of 40-50% allows obtaining a dense sintered structure of celsian ceramics at a relatively low sintering temperature of 1400-1450°C. Celsian ceramics have thermal stability up to 700°C, refractoriness index up to 1580°C, and meets a complex of requirements imposed on radio-transparent materials (ε = 5,5; tgδ = (5–6)·10-4) in an ultra-high frequency electromagnetic field of 1010 Hz.
A technological scheme has been proposed and the technological parameters for obtaining cordierite and celsian ceramics for nose antenna fairings have been indicated. The provided technological recommendations allow the production of products at a lower cost due to a decrease in the melting temperature of the glasses used as components of the developed ceramics, a decrease in the sintering temperature and a reduction in the duration of the ceramics sintering process and will also contribute to reducing the dependence of domestic defense industry enterprises on imported component materials.
Production tests of ceramic materials were carried out at the Konstantinovsky State Scientific and Production Enterprise "Kvartsit" of the State Concern "Ukroboronprom". The test results confirmed the compliance of the developed cordierite and celsian ceramics with the requirements for use in radome fairings of radio-controlled missiles.
