VOL 96, No. 12 (2023)

The influence of the technological parameters of glass melting of the selected composition in the SrO–Al2O3–P2O5–SiO2–F system on the value of the refractive index and the amount of fluorine that remains in the glass structure after melting is investigated. The use of a joint lowering of the melting temperature and tableting of the charge leads to an increased absorption of fluorine in the glass up to 17 wt. % at the same time, the value of the refractive index decreases to nD = 1.49. It has been experimentally established that in the selected multicomponent glass for glass ionomer cements with two glass-forming oxides SiO2 and P2O5 with a high content of Al2O3, each mass percentage of fluorine reduces the refractive index ?3.5•10–4 units.

The technology of facing material based on mechanically activated cullet modified with potassium hydroxides has been developed. The phase composition, macro- and microstructure of the lining material are investigated.
It is established that the structure of the composite modified with potassium hydroxide is represented in the interstitial space by needle-like and columnar crystals of potassium silicates. The physical and mechanical characteristics of the facing material are investigated.

The influence of modification of the glasses composition of the strontium-aluminum-borosilicate system on their technological and physic-chemical properties has been studied. The introduction of two alkalis into the composition of the glass made it possible to significantly reduce the melting temperature from 1500 to 1450 °C and led to changes in the properties of the glasses. When introduced into the composition of glass up to 5 mol. %. The coefficient of thermal linear expansion of alkalis decreased from 58 to 50 (??10–7 К–1), and the refractive index nD – from 1.551 to 1.528. However, alkaline components negatively affect the hydrolytic resistance of glass, transferring them from the I to the II hydrolytic class. The solution to this problem was: 1) the use of mixed alkali effect, 2) the introduction of a small amount of highly effective radiopaque barium oxide into the composition and a significant reduction in the content of less radiopaque SrO in order to maintain high radiopacity, 3) an increase in the content of aluminum oxide, which usually leads to an increase in the chemical resistance of glass. As a result, glasses with high values of radiopacity (~550 %), light transmission (T = 90 %) and with refractive index values of nD = 1.530 and CTE = 56 (??10–7 К–1) were obtained while maintaining chemical resistance to water corresponding to the hydrolytic class.

The main industrial method for manufacturing precision metal parts with high surface finish, such as turbojet engine blades, is investment wax casting. When manufacturing a wax model, a ceramic embedded element (rod) is placed inside it to form a complex-shaped cavity designed to reduce the weight of the casting, and forming channels for the cooling system of the blades with secondary air after the rod is removed. The main technological problem in the removal of internal rods is their strength and high chemical inertness, which is why the duration of their removal and labor costs for this operation are quite large. The paper presents a study of a method for manufacturing ceramic rods with uneven strength in depth, which makes it quite easy to remove the soft core, followed by the dissolution of a stronger periphery.

It has been established that the high temperature of decomposition of amorphous Al(OH)3 makes it possible to directly sinter corundum ceramics from aluminum hydroxide, bypassing the stage of its preliminary thermal dehydration. Cold isostatic pressing at pressures of 200, 600, and 1000 MPa was used to make compacts with a density of 62, 69, and 79 % of the theoretical density. The temperature dependence of the shrinkage of compacts of amorphous Al(OH)3 as a function of the pressure of cold isostatic pressing has been studied. A region of intense shrinkage was found in the region of 1050 – 1150 ?C, which coincides both with the temperature of complete decomposition of amorphous Al(OH)3 and with the ???-Al2O3 transition.

The possibility of obtaining a new alternative source of clay raw materials for obtaining ceramic materials based on silt deposits of reservoirs, which has functional properties, is considered. The physicochemical properties of silty bottom sediments of the Tuyamuyun reservoir in Uzbekistan have been studied. It has been established that the developed ceramic masses based on the “silt-kaolin” double composition can be used for the production of ceramic materials for building purposes.

Calcium monoaluminate was synthesized using the sol-gel method and the effect of europium and neodymium oxides on the synthesis and kinetics of structure formation in the temperature range of 500 – 1000 ?С was studied
It has been established that the formation of the structure of calcium monoaluminate occurs at a temperature of 1000 ?C and with exposure for 4 hours of a xerogel obtained on the basis of a mixture of Al(NO3)3 + Ca(NO3)2 at a ratio of compounds of 2 : 1, respectively. In the sample obtained, the intermediate mineral is mayenite Ca12Al14O33. With the introduction of mineralizing europium oxide Eu2O3 in an amount of 1.5 wt. % over 100 wt. % into the Al(NO3)3 + Ca(NO3)2 composition, at a synthesis temperature of 1000 ?C, the exposure time for the maximum formation of calcium monoaluminate is reduced to 1 hour. In samples containing Nd2O3, for the maximum formation of calcium monoaluminate at the same exposure time, it is required to introduce it in an amount of 5 wt. %.

The publication presents general information about calcium zirconate and the physical/chemical properties of products based thereon. Methods for CaZrO3 production, such as solid-phase synthesis, electric arc melting, codeposition, hydrothermal synthesis etc. are studied.