VOL 72, No. 2 (1999)

The adequacy of the previously developed mathematical model of the glass tube annealing process has been experimentally proved. The refinement of this model in relation to the annealing of building glass blocks by taking into account the influence of barometric rarefaction inside the air cavity of the product on the process of occurrence and distribution of stresses in the product, and also experimentally proved the adequacy of the modified model. Il. 2, bibliography: 7 titles.

Discrete thermomagnetic analysis allows one to identify the mineral composition of free iron compounds: goethite and hematite (as a result of heating in a reducing environment), iron carbonate and siderite (as a result of heating in an oxidizing environment). New informative criteria were used - the reducing and oxidizing ability of free iron compounds. A classification of clay-containing materials used in the ceramic industry into three groups in accordance with the gradation of the reducing ability of free iron compounds is proposed. Tab. 1, ill. 4, bibliography: 7 titles.

Abstract — Polymorphic transitions in oxides controlled by diffusion proceeding by the vacancy mechanism are considered. To ensure the neutrality of the total electric current arising during the movement of ions, a certain ratio of vacancies in cation and oxygen is required. Since oxides usually have an excess of oxygen vacancies at high temperatures, a further increase in their concentration due to the introduction of appropriate additives slows down diffusion, prevents the polymorphic transition, and stabilizes the phase. The introduction of additives leading to an increase in the concentration of vacancies in the cation, on the contrary, accelerates diffusion and promotes the polymorphic transition. Bibliography: 10 titles.

Ceramic pigments with diopside and anorthite structures based on natural wollastonite have been obtained. It has been shown that the reactions of the synthesis of the diopside structure proceed in a multistage manner, with the formation of intermediate products. For a more complete phase formation of the anorthite structure, mineralizer additives are required. The resulting pigments have a bright color and can be used to decorate porcelain-faience and majolica products. Tab. 5, ill. 2, bibliography: 4 titles.

Zinc oxide ceramics used for the manufacture of varistors are considered. The most probable mechanism of the non-ohmic behavior of a material with various alloying additions under the action of an electric field is discussed. Il. 3, bibliography: 15 titles.

On the basis of a comprehensive study of the physicochemical properties and behavior during firing of quartz-pyrophyllite raw materials, the suitability of its use in the composition of porcelain masses as a substitute for quartz and partially for kaolin is shown. The resulting household porcelain has a low firing temperature (1280 - 1300 ° C) and has good physical and mechanical properties. Tab. 1, ill. 2, bibliography: 6 titles.

It is shown that to assess the physicomechanical characteristics of foam and biporous materials, it is necessary to determine the threshold concentration of the conductive component, which depends on the elongation of the solid phase particles and the ratio of its average size to the size of macropores. Calculations of the thermal conductivity of foamed corundum and the strength of foamed gypsum have been carried out. The proposed method makes it possible to take into account the porosity of the matrix phase and obtain results that are in good agreement with the experimental values. The considered approach is recommended for evaluating the conductivity and strength of foams in engineering calculations. Tab. 1, ill. 3, bibliography: 9 titles.

Compositions of slab masses using local clay and metallurgical slag have been investigated. The optimal composition of the mass of floor tiles was determined by the method of mathematical planning. The combined introduction of slag and cullet ensured a decrease in the firing temperature to 1050 ° C. Tab. 2, ill. 3, bibliography: 3 titles.

Possible approaches to solving the problem of reproducibility of the quality of products made of ceramic materials are analyzed. It is indicated that only statistical methods are used for this purpose is insufficiently effective. A program of stages of the study of the object under study is proposed, which ends with the creation of a mathematical model of the physicochemical processes of ceramic synthesis. Bibliography: 5 titles.

The use of feldspar rock (orthofira) and feldspar wastes of JSC "Molybdenum" (overburden pegmatites and "tails" obtained after ore processing) in the compositions of ceramic masses has been investigated. The dependence of sintering and phase formation on the type and amount of feldspar component and the amount of cullet in the charge has been established. A diagram has been developed for selecting the composition of ceramic masses with the required degree of sintering. The properties and phase composition of tiles with an optimal amount of feldspar components have been investigated. Tab. 4, ill. 2, bibliography: 3 titles.