Physico-chemical processes of fusion formation and sintering of high-alumina ceramic materials MgO‒CaO‒Al2 O3 ‒SiO2 systems in two-step and one-step non-sintered technology

Abstract

The content of the research is the analysis of the processes of formation and growth of the melt amount during high-alumina ceramics VK-91 firing according to the melting curves of analogs, the compositions of which are reduced to the phase diagram of the CaO‒Al2O3‒SiO2 system. The results of studies of the phase composition, microstructure and properties of fired ceramic samples obtained by single-stage and two-stage non-sintered technology are presented. The melt required for sintering high-alumina ceramics VK-91 products at a firing temperature of 1550 °C without preliminary obtaining of ceramic sinter is formed by a nonequilibrium process by dissolving α-Al2O3 in eutectic melts of ternary aluminosilicate systems including calcium and magnesium oxides. The presence of zircon (ZrO2·SiO2) in the batch leads to the formation of anorthite at high temperatures (above 1400 °C) through the product of the interaction of zircon with calcium oxide, which in some cases does not achieve its complete dissolution in the melt. According to the properties of fired ceramics, a single-stage technology for preparing the slip with organic liquids for casting the original ceramic tape is preferable. Ill. 5. Ref. 13. Tab. 7.