VOL 95, No. 4 (2022)

The glass-crystalline ceramic materials in SiO2–Al2O3–RO (RO–MgO, SrO, BaO and their combinations) systems have been synthesized by the sol-gel method. The factors influencing on the sol-gel formation process are revealed. The effect
of the composition and temperature-time modes of heat treatment on the crystallization properties of gels, phase transformations, phase composition, granulometry and shape of the resulting particles has been studied. The nature of phase transformations in powders is revealed depending on the temperature-time conditions of heat treatment. It is shown
that the dominant crystalline phases, depending on the composition, are anorthites or their solid solutions, their formation temperatures have been established: hexagonal celsian is formed at a temperature of 1350 °C, monoclinic strontium
anorthite – at 1400 °C, cordierite – at 1450 °C. The influence of pressing and heat treatment conditions on the physic-mechanical, dielectric and thermal properties of the obtained materials is investigated.
The synthesized glass-ceramics with low dielectric constant and dielectric loss tangent, high deformation temperatures (above 1500 °C) is a promising replacement for the spodumene-eucryptite and cordierite sitalls currently used as radio-transparent materials, the disadvantage of which is insufficiently high operating temperatures (not higher 900 – 1100 °C).

Effect of quartz tubes crystallization on quality of blanks from quartz ceramics of radio engineering appointment is investigated. The analysis of effect of a way of tubes samples preparation for resistance test to crystallization is carried out.
Assessment of effect of impurity mass fraction in quartz concentrates on crystallization of tubes at incoming control, and also on existence of crystal phases in products and on the properties of products controlled in production from quartz ceramics is carried out.

The article describes the mechanisms of formation of the structure of low-temperature porcelain with the use of new non-traditional raw materials. As a result of the research, it was found that the formation of the structure of the experimental porcelain materials is completed at lower firing temperatures (1220 – 1250 °C). The phase composition of the synthesized porcelain consists mainly of crystals of mullite, quartz, cristobalite and the vitreous phase filling the gaps between the crystals.

Dense and porous thermal-insulating ceramic materials were obtained from the flotation tailings of coal sludge of the processing plant of Inta town. The thermal behavior, changes in the phase and chemical composition during firing in the temperature range from 800 to 1280 °C were studied. During firing, carbonates dissociated, magnetite oxidized, kaolinite amorphized, layers in layered silicates compressed, at 1100 °C cristobalite and spinel were formed, at 1150 °C – mullite, the content of the amorphous phase increased. Dense ceramic materials were obtained at firing temperatures of 800 – 1150 °C, and porous materials at temperatures 1200 – 1280 °C. The physical, mechanical and technical characteristics of the obtained ceramic materials were studied. Porous ceramics, sintered at 1280 °C, belongs to the class of heat-insulating materials with increased thermal conductivity.

In the production of aircraft parts by precision casting in ceramic molds, the key parameters are the uniformity of the composition and strength of ceramic molds associated with the technology of their manufacture. The technologically optimal strength of ceramics can be achieved using the technology of re-impregnation of a ceramic product with a binder, but in this case problems arise with the isotropy of the mechanical properties of the products. The paper presents the results of research and development of methods for regulating the uniformity of impregnation of ceramic samples with a secondary binder.

Three batches of unidirectional basalt fiber-reinforced plastic were fabricated as plates, and continued tests were performed under load at room temperature and in a closed desiccator at a 99 % moisture for 365 days. The moisture absorption
of the unconstrained specimens in the desiccator was not above 0.20 – 0.23 %. The residual mechanical properties
of the specimens that had been held in the desiccator for 365 days were measured after being dried, and the ultimate strain was found to increase by 10 – 15 %, the elastic modulus by 14 – 21 %, the strength by 19 – 21 %, and the glass transition temperature by 5 – 8 °С.

The possibility of obtaining inorganic block heat-insulating foams based on silica and ash-containing man-made waste is considered. The influence of modifying additives and technological modes on the structure and basic technical properties of foam silicates has been determined. As a result of the studies, the optimal content of ash waste was established in the amount of 5 – 15 %. The obtained foam silicates are characterized by physical and technical properties: density 0,36 – 0,45 g/cm3, strength 2,8 – 5,2 MPa, thermal conductivity 0,089 – 0,106 W/(m?K) and water absorption 14 – 22 %.