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A comparative study was carried out on the possibility of controlling the average sizes of nano-sized powders of silicon dioxide and aluminum oxide obtained by electron beam evaporation, pyrogenic, liquid chemical and plasma chemical methods, by keeping them in the temperature range of 800 – 1300 ?C in an air atmosphere. The average size of the resulting particles was estimated from specific surface area measurements using the Brunauer–Emmett–Taylor (BET) adsorption method at liquid nitrogen temperature. Crystallographic parameters in the treated powders were assessed using X-ray diffraction analysis. It has been shown that by appropriate choice of temperatures and initial powder, it is possible to achieve an average particle size in the resulting powder close to a given one and a phase composition.
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Using the method of self-propagating high-temperature synthesis (SHS) SHS compositions based on the Si3N4–Yb2O3 system were obtained. Synthesis by combustion was carried out in a nitrogen atmosphere at a pressure of 4 MPa in a reactor with a volume of 30 liters. The mass of the loaded mixture was 3 kg. It has been established that the amount of ytterbium oxide in the charge affects the combustion temperature and the phase composition of the synthesis products. With an increase in the proportion of ytterbium oxide in the mixture, the content of the alpha phase decreases, and the secondary phases are represented by quaternary ytterbium-silicon oxynitride and ytterbium disilicate.
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In this work, the effect of sintering additives based on magnesium oxide (MgO) and silicon oxide (TEOS) in concentrations from 0.02 to 0.10 wt. % and 0.2 to 0.5 wt. %, respectively, was investigated on the microstructure and optical properties of ceramics of the composition Y2,82Yb0,15Er0,03Al5O12, made from powders synthesized by chemical co-deposition.
The results presented in the paper showed that the introduction of a sintering additive based on MgO into a ceramic powder does not affect its phase composition, structural and morphological characteristics. It is shown that for ceramics of the composition Y2,82Yb0,15Er0,03Al5O12, the best value of the optical transmission coefficient was achieved at a vacuum sintering temperature of 1800 °C and a concentration of sintering additives of 0.06 wt. % MgO and 0.3 wt. % TEOS.
It is shown that the sintering mechanism of ceramics Y2,82Yb0,15Er0,03Al5O12 depends on the ratio of sintering additives MgO and TEOS.
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From a cheap perlite as the basic raw material an opaque glass-crystalline material was synthesized containing nanosized crystals of wollastonite and gehlenite with an average size of 100 nm. The phase composition, microstructure and strength properties of the material were investigated. Changes in the composition and size of crystal grains caused by varying the amount of catalyst and the content of quartz in the initial mixtures make it possible to control the physico-mechanical properties of the obtained material. High strength and hardness allow using this material for protection against high-speed impact, including small arms bullets.
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The purpose of this article is to apply an integrated research approach for the reconstruction of ceramic production technology in the territory of the Kyrgyz Republic based on the results obtained by modern methods. The paper summarizes for the first time the results of the study of physical-mechanical and physical-chemical properties and an attempt is made to reveal the methods of technical analysis of ceramic artifacts.
An unified scientific approach to ceramics of various periods from the II millennium BC to the X-XII centuries, excavated in Kyrgyzstan, to determine the relationship between their microstructure and physical and mechanical properties. Ceramics technology, like no other industry, requires this kind of research due to the specifics of technical information associated with both natural and social factors.
Lack of solid knowledge in the field of ceramics technology has prevented them from obtaining important information about Kyrgyz history, culture, and economy, which is the subject of their nation-building efforts. However, a comprehensive study of the production technique, types, composition and quality of ceramics would open up completely new prospects for confirming the antiquity of Kyrgyzstan.
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Compositions of muffled glasses for the upper layer and the lower structural layer of composite glass-crystal cladding material based on phosphorus industry waste have been developed: phosphoric slag, phosphorite fines, coal dust and cullet.
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The effect of immersion in a coffee drink solution on the color stability of two CAD/CAM ceramic restorations was investigated in this in vitro study. To this end, zirconia-reinforced lithium silicate (ZLS) and lithium disilicate (LDS) glass-ceramic blocks were surface-treated using mechanical polishing and glazing techniques. In addition, their color was examined before and after immersion in a coffee solution using a spectrophotometer, and the color changes were evaluated. A two-way analysis of variance (ANOVA) was used to examine the color changes. The material type significantly influenced color changes (P < 0.001). After glazing and mechanical polishing, LDS exhibited considerably less color change in both groups than ZLS. In both types of ceramics, the glazed group experienced less color variation than the mechanically polished group. Color changes were clinically acceptable across all groups. The glazing surface treatment produced superior color stability than the mechanical polishing technique. LDS exhibited more color stability than ZLS in both surface treatments.
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The paper studies the conditions for synthesis of mullite-corundum ceramics obtained on the basis of Al2O3 and SiO2. The composition of mullite-corundum ceramics with an Al2O3 content < 80 wt.% has been determined, which ensures
the best thermomechanical compatibility with molybdenum. The possibility of obtaining a composite material based on a mullite-corundum matrix and molybdenum, as well as its use as a barrier layer at the interface of Мo–Si-containing ceramics, has been confirmed. It is established that use of barrier layer significantly reduces the likelihood of thermal stresses in the interface of the two phases. It is shown that there is a need to refine the technological parameters of the preparation of the powder Al2O3–SiO2 mixture to increase the thermochemical compatibility of molybdenum with mullite-corundum ceramics.
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In this study, LuAG:Ce ceramic powders with compositions of Lu2.98Ce0.02Al5O12 and Lu2.93Ce0.07Al5O12 were synthesized using chemical precipitation. Luminescent ceramic samples were then produced from these powders by vacuum sintering green bodies in the temperature range of 1600 – 1800 ?C. The study aimed to investigate the effect of cerium concentration and vacuum sintering temperature on the optical properties of LuAG:Ce ceramics. The spectral luminescence properties
of the LuAG:Ce ceramic samples were analyzed. Results showed that the luminescence intensity was dependent on the activator concentration and vacuum sintering temperature. Additionally, a shift in the maxima of the luminescence spectral bands of the LuAG:Ce ceramics was observed when varying the vacuum sintering temperature within the 1600 – 1800 ?C range.
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In this work, using the methods of X-ray phase, X-ray diffraction, synchronous thermal analysis, scanning electron microscopy, low-temperature adsorption-desorption of nitrogen, the process of obtaining CuO/ZnO/?-Al2O3 composites, which can be used as the main component of catalysts for large-tonnage processes for methanol production and monoxide conversion, was studied. carbon. The influence of the method of preparation, the nature and intensity of processing on the phase composition of the resulting precursors and the physicochemical properties of the resulting composites was established. The processes occurring at the stage of mechanochemical activation of a mixture of anhydrous CuO/ZnO/?-Al2O3 oxides, a mixture of oxides with ammonium carbonate and ethanedienic acid have been studied.
The optimal parameters for obtaining CuO/ZnO/?-Al2O3 composites with a developed specific surface area and porous structure have been determined.
