The conditions for producing tetragonal and cubic leucite from tetragonal analcime by hydrothermal ion exchange in an alkaline medium are identified. The process parameters are specified. A composite ceramic material based on cubic leucite is developed for the heating elements of plants for vacuum synthesis of pure inorganic compounds.Leucite KAlSi 2 O 6 belonging to the feldsparoid group is structurally close to the mineral analcime, i.e., hydrous sodium alumosilicate Na[AlSi 2 O 6 ] × H 2 O. In most cases two varieties of leucite are used in engineering: of the tetragonal and the cubic syngony. Leucite of the cubic syngony is formed in oxide systems under firing at temperatures above 605°C [1]. As the ceramic mixtures cool, it changes into the tetragonal syngony [2, 3]. The modification of the crystal lattice parameters and the CLTE causes cracking in leucitebased ceramic coatings that are extensively used for dental cement. It is established that dental cement of better quality can be obtained at temperatures of 800 -1000°C if hightemperature cubic leucite is stabilized in firing by a Cs 2 O additive [4 -7].We investigated the processes of producing cubic leucite by the ion-exchange method under hydrothermal conditions at temperatures below 200°C from presynthesized analcime and the possibility of using leucite in ceramics for electric heaters of vacuum synthesis plants.
The critical parameters of silica refractories, such as compressive strength, bulk, density, quantity of silica, microstructure and porosity were evaluated of unused and used bricks to line the crowns of glass furnaces, when the rate of corrosion of crowns were about 2 times greater. The change of these parameters, the chemical composition and formation of the microcracks in the used silica refractories material were studied. It was established that the short time at service of container glass furnace crown can be related to low quality of silica brick: high quantity of CaO and impurities, low quantity of silica, low quantity of silica, transferred to tridymite and cristobalite and formation of 5-10 μm and more than 100 μm cracks in the crown material. The main reason of corrosion high quality silica bricks used to line the crown of electrovacuum glass furnace is the multiple cyclic change of crown temperature at 1405 - 1430°C range in the initial zone of crown and at 1575 - 1605°C range in the zone of highest temperatures
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