Physico-chemical properties and structural transformations in the synthesis of boroalumosilicate glass-crystal materials

The aim of this work is to study the areas of glass formation and metastable liquation of the pseudo-ternary system (MgO·Al2O3)-B2O3-SiO2, and study of the crystallization process of glasses of cordierite composition. The crystallization process of glasses of cordierite composition containing B2O3 by a single-stage heat treatment at 1000 oC and 1200 oC, the nature of crystallization, the thermal properties of glasses and glass crystalline materials of the system (MgO·Al2O3)-B2O3-SiO2 were studied. It revealed that during the isolation of a boron-containing solid solution, the residual glassy phase enriched with oxides of MgO and Al2O3, which lead to an increase in the thermal expansion coefficient of the glass phase. The research results provide possibility to synthesize glass-ceramics with certain thermophysical parameters by stopping further glass crystallization at the stage of formation of a certain amount and ratio of the required crystalline and glassy phases.

MICROFRAGMENTATION OF CAST MICA-CRYSTALLINE MATERIAL UNDER DYNAMIC COMPRESSION

The study aimed at assessing the prospects of using mica-crystalline material of the fluorophlogopite type (the main phase corresponds to the compound KMg3(Si3AlO10)F2) for use in the manufacture of armored products. To carry out such an assessment, the study established the features of the deformation of cast mica-crystalline material of the fluorophlogopite type under dynamic compression by the method of the split Hopkinson-Kola rod. It was revealed that the destruction of cast mica crystalline material at an average strain rate of 250-1500 s-1 occurs with the formation of finely divided fragments. The exposure rate was chosen by analogy with the well-known tests of materials of a similar purpose with a glass crystal structure. For a quantitative assessment of the fracture intensity, the fractional composition of the fracture fragments was analyzed by analyzing the images obtained by scanning electron microscopy. In the course of the analysis of the experimental data, it was found that a characteristic indicator in the analysis of the fractional composition of fracture fragments is the proportion of those whose size is from 1 to 100 μm in the total mass of fragments up to 1000 μm (larger fragments are not considered, since they are formed again as fragments destruction arising after the formation of main cracks), for the material studied, this indicator under the specified exposure conditions ranged from 83 to 87%, which, based on a comparison with similar materials used in the manufacture of elements of armored products, allows us to evaluate it as a material promising in this field of application, since in addition to the optimal indicators of fractional fracture upon impact, this material has a lower density in comparison with analogues and products from it may have a lower mass, which is a competitive advantage.

INVESTIGATION OF THE EFFECT OF OXIDE ADDITIVES ON THE PROPERTIES OF HEAT-RESISTANT GLASS-CRYSTAL COATING

Experimental compositions of coatings based on SiO2–Al2O3–MgO matrix glass and modifying additives are considered. A number of refractory metal oxides were selected as modifying additives. The influence of these additives on the properties of the coating melt, such as the spreadability and the wetting edge angle, as well as the oxidability of the resulting compositions, is studied. It was found that the experimental coating modified with aluminum oxide has the best protective properties. The introduction of modifying additives in quantities of more than 5 % is considered inappropriate.

TECHNOLOGY FOR PRODUCING COMPOSITE GLASS-CRYSTAL FACING MATERIALS BASED ON MIXED CULLET

An effective energy-saving technology for producing composite glass-crystal facing materials based on fractionated cullet of sheet and container glasses, cullet of porcelain and sodium liquid glass has been developed. The use of fine porcelain powder in the composition of composite glass-crystal facing materials in an amount of up to 10 wt is justified. % and liquid sodium glass up to 5 wt. %. It is shown that the optimal fractional composition of granulated mixed cullet is 35 wt. % fraction 0.63-0.80 mm; 35 wt. % - fractions of 0.80-1.25 mm and 30 wt. % fraction of 1.25-3.15 mm. Polytherms of viscosity of colorless, green and brown container glasses, as well as sheet glass, are calculated. The possibility of using mixed cullet for obtaining composite glass-crystal facing materials is on the basis of obtained dependencies. The chemical composition of sheet and container glasses and porcelain is studied using x-ray fluorescence analysis. Optimal charge compositions have been developed to obtain glass-crystal materials with compressive strength up to 79 MPa. The technology of obtaining composite glass-ceramic facing material includes the following technological operations: milling of glass breakage; grinding cullet of porcelain; drying of sodium liquid glass; the screening of crushed cullet on fractions; the grind of crushed cullet of China; grinding the dried sodium silicate glass; weighing the components in accordance with the developed formulations, the averaging of the graded cullet with fine porcelain; averaging the mixture of finely ground dried sodium silicate glass; stacking the mixture in a metal mold; compaction of the mixture in metal molds; heat treatment in a muffle furnace (sintering); extraction of facing tiles from molds; trimming the edges of the tiles with a diamond saw; quality control of finished products.