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666.3.016:666.3-134.1

STRUCTURE AND PHASE FORMATION MECHANISM FOR HOLLOW SPHERES OF ALUMINUM-MAGNESIA SPINEL IN OBTAINING POWDERS BY CHEMICAL DISPERSION OF ALUMINUM-MAGNESIUM ALLOYS A. A. Vasin,1, 2 V. P. Tarasovskii,1, 3 A. V. Smirnov,1, 4 A. Yu. Omarov,1, 5 A. V. Reznichenko,1, 6 and T. Yu. Skakova1, 7 Translated from Steklo i Keramika, No. 1, pp. 3 – 9, January, 2020.

The results of an investigation of the processes underlying the formation of hollow aluminum-magnesia microspheres by chemical dispersion of magnesium-aluminum alloys with heightened content of magnesium are reported. The mechanism of the formation of microspheres and the factors determining their structural features and sizes are elaborated. It is shown that magnesium additives influence the formation of the structure of hollow microspheres and their number. The fine structure of the powders before and after heat-treatment was studied. Key words: chemical dispersion, aluminum-magnesia spinel, raw materials, powders, hollow microspheres, ceramics, highly porous materials, thermal insulation, refractories.

One of the important problems of ceramic material science is the development of a ceramic combining low-density and high-performance. A great deal of attention is now being devoted to materials containing aluminum-magnesium spinel. Aluminum-magnesium spinel counteracts the penetration and action of water, mineral acids, alkaline melts, carbon, many metals, vacuum, and metallurgical slags. In the manufacturing technology for products made from such material the spinel synthesis stage, to which a great deal of attention is devoted, is a separate technological operation. The simplification or elimination of this stage, reduction of the role of purity and dispersity of the individual raw-material components and elimination of the need for their careful matching, and the optional use of different media during heat-treatment are very promising and unsolved problems. The experience gained in the manufacture of ceramic materials shows that the problem of reducing product mass while maintaining product performance can be solved by 1 2 3 4 5 6 7

using hollow microspheres. By using such hollow microspheres it is possible to control the structure of the pore space, reduce the density, increase thermal stability, and improve the refractory and heat insulation properties of the materials. The conventional methods used to obtain sinterable powders with these characteristics are complicated, expensive, and low-tech. Today, there exist technologies for obtaining microspheres and microballoons made from Al2O3 and SiO2 but a method does not exist for obtaining microspheres or microballoons of micron and sub-micron sizes from aluminum-magnesium spinel with a large yield of the finished product. This is what determines the timeliness of the work performed by the present authors, which is devoted to the development of a fundamentally new, technologically simple, and energy-conserving scheme for producing hollow microspheres of aluminum-magnesium spinel. The main scie