Browsing by Author "Rudnieva, L. L."

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    Glass-Ceramic Binder of Cordierite Composition for Low-Temperature Sintering of High-Strength Ceramic Materials Based on Oxygen-Free Silicon Compounds
    (Ukrainian State University of Chemical Technology, Dnipro, 2024) Polozhaj, S. G.; Zaichuk, Oleksandr V.; Polozhaj, A. G.; Amelina, O. A.; Rudnieva, L. L.
    ENG: The mechanical properties of composite ceramic materials obtained based on oxygenfree silicon compounds are largely determined by the properties of the glass binder. This paper presents the results of studies aimed at determining the most fusible glass in the pseudo-binary system 2MgO⋅2Al2O3⋅5SiO2–2MnO⋅2Al2O3⋅5SiO2 with a high tendency to crystallize as a glass-ceramic binder for low-temperature sintering of high-strength ceramic materials based on oxygen-free silicon compounds. The crystallization tendency of the experimental melts decreases with an increase in in the content of manganese cordierite, as confirmed by X-ray and infrared spectroscopic studies. Based on experimental studies, a melting diagram was constructed, which was used to determine the ratio between magnesium cordierite and manganese cordierite (50:50 wt.%), ensuring a minimum melt temperature of 1275 oC. The melting point of the glass of the specified composition is 1450 oC. The synthesized glass is characterized by a softening point of 800 oC and crystallizes intensively at 1030 oC. The thermal coefficient of linear expansion of the crystallized glass samples is 20.8⋅10–7 oC –1. X-ray diffraction and electron microscopic studies have shown that the developed glass is almost completely crystallized during heat treatment for 2 hours, forming a cordierite solid solution 2(Mg,Mn)O⋅2Al2O3⋅5SiO2. The size of the cordierite phase crystals ranges from 0.5 to 3.0 µm. Due to its fusibility and high crystallization tendency, the developed glass, can be proposed as a promising glassceramic binder for the production of high-strength ceramic materials (wear and impact resistant) based on SiC and Si3N4 with reduced sintering temperatures.
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    Thermodynamic Analysis of the Reactions of Strontium Anorthite Formation during the Firing of Thermal Shock Resistance Ceramics Based on the Eutectic Glasses of the SrO–Al2O3–SiO2 Systems
    (Ukrainian State University of Chemical Technology, Dnipro, 2023) Zaichuk, Oleksandr V.; Sukhyy, Kostyantyn M.; Amelina, O. A.; Hordeieiv, Y. S.; Filonenko, D. V.; Rudnieva, L. L.; Sukha, Iryna V. ; Halushka, S. A.
    ENG: Thermal shock resistance ceramic materials must have a high degree of sintering to ensure the required mechanical strength, erosion resistance, and resistance to high-temperature oxidation. However, the search for effective ways to achieve a high degree of sintering of ceramic materials based on the SrO–Al2O3–SiO2 system at low temperatures requires a large amount of experimental research. The aim of this work is to analyze thermodynamically the reactions of strontium-anorthite phase formation at the points of triple eutectics of the SrO–Al2O3–SiO2 system under low-temperature firing conditions. The eutectic points were selected in the region of strontium anorthite crystallization and had a temperature not exceeding 14000C. It has been established that in the case of compliance with the stoichiometric ratio, the final product of the interaction of the components of eutectic glasses S-1 and S-2 with the charging components is the strontium anorthite phase. The most probable is the formation of strontium anorthite in the interaction of eutectic glass components with Al2O3∙2SiO2, which is a product of kaolinite dehydration (Al2O3∙2SiO2∙2H2O). It has been found that the compounds SrO∙SiO2 and 2SrO∙Al2O3∙SiO2 are most active in the interaction with the charging components in the direction of formation of the strontium anorthite phase than SiO2 tridymite. As a result, the sintering of strontium-anorthite compositions at a temperature of 9000C causes a significant increase in the content of the crystalline phase of strontium anorthite. The determined patterns allow making a reasonable choice of glass in the SrO–Al2O3–SiO2 system for the further manufacture of low-temperature strontium-anorthite ceramics.