Browsing by Author "Polozhaj, S. G."

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    Fusible Glass-Crystalline Binder in the Spodumene–Manganese Cordierite System
    (Ukrainian State University of Chemical Technology, Dnipro, 2024) Polozhaj, S. G.; Zaichuk, Oleksandr V.; Polozhaj, A. G.
    ENG: Low-melting glass-crystalline materials with a low temperature coefficient of linear expansion (TCLE) are widely used in various engineering fields. These materials are utilized for joints, protective coatings, additives in sintering of ceramic materials, including as matrices for high-strength dispersion-reinforced materials based on oxygen-free silicon compounds. This paper presents the results of a study on glass-crystalline materials in the pseudo-binary spodumene–manganese cordierite system. Based on experimental data, a fusibility diagram was constructed. Crystalline phases formed during the cooling of the glass melts were identified using X-ray phase analysis and their crystallization tendency was evaluated. It was found that the crystallization ability of the glasses decreases with an increasing content of manganese cordierite. The most promising, low-melting glass composition was identified, with a LiAlSi2O6:Mg2Al4Si5O18 ratio of 30:70 wt.%. The glass formation temperature for this compostion lies in the range of 1200–1250 oC, and the practical melting temperature is 1450 oC. The synthesized glass exhibits softening and intensive crystallization onset temperatures of 760 oC and 960 oC, respectively. The TCLE of the glass is 34.9⋅10–7 oC–1. The primary crystalline phase, β-spodumene, forms bundles of needle-like crystals 10–15 μm in length within the residual glass phase, reducing the material’s TCLE to 20.9⋅10–7 oC–1. The developed material shows potential as a glass-crystalline binder for producing high-strength ceramic materials (wear-resistant and impact-resistant) based on SiC and Si3N4 with reduced sintering temperatures.
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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.