In the investigated rocks of talc stone (carbonate-chlorite-talc composition) and accompanying tremolite-chlorite rocks in the temperature range of 950-1100 ° C, the following processes occur: dehydration (talc, tremolite, chlorite), decarbonatization (dolomite, calcite, breinerite) and the formation of new crystalline phases (forsterite, enstatite, clinoenstatite, subcalcium augite) due to the decomposition of talc and tremolite. These processes, as well as the presence of an amorphous phase enriched in magnesium cations, increase the strength of the ceramic. An additional factor for increasing the strength is the larger, slightly changed grains of tremolite due to the tabular and acicular shape, which have a reinforcing effect on the structure of the ceramics. Tab. 3, ill. 2, bibliography: 10 titles.
The technology of high-temperature synthesis of NZP-structures on solar ovens has been implemented. Phase formation in the obtained systems has been studied by X-ray phase analysis. It has been established that Ca, Sr, and Ba phosphates obtained by melting are of the NZP structural type. The possibility of obtaining strong porous monophase NZP ceramic samples by traditional sintering methods has been shown experimentally. Tab. 3, ill. 1, bibliography: 6 titles.
The influence of the concentration of H 2 SO 4 , HCl, NaOH and Na 2 CO 3 on the chemical resistance of porous permeable ceramics based on electrocorundum and aluminosilicate bond. It is shown that the chemical resistance of porous ceramics of the chemical composition selected for testing depends on the type and concentration of the reagent solution taken for testing. Porous ceramics are the least chemically stable in concentrated sodium hydroxide solutions. The most chemically stable porous ceramics in solutions of soda
ash of any concentration. Porous ceramics have minimal acid resistance in a sulfuric acid solution at a concentration of 90 - 80%. Tab. 5, ill. 3, bibliography: 5 titles.
Data on the rheological behavior of samples of materials of the porcelain group at pure shear were obtained, complementing the results of dilatometric studies of shrinkage. The concept of the macromechanism of deformation along the critical regions is proposed, which explains the shear deformation in the low-temperature region, which is carried out due to the sliding of grains along the boundaries of their contacts (СЗ). The presence of a constant (with respect to the heating temperature and significant up to 1200 ° C) structural-rheological component was found, which is responsible for the dilatant behavior caused by the SZ. In the temperature regions of intense crystallization of mullite, the maximum rate of shrinkage corresponds to the maximum rate of increase in viscosity. Il. 12, bibliography: 14 titles.
Fine-dispersed powders of REE ferrites were obtained by the "wet combustion" method. The solid-phase synthesis of lanthanum-gadolinium ferrite has been studied. It has been shown that the target phase can be obtained at temperatures up to 750 ° C. Firing modes have been found that make it possible to obtain ceramics based on REE ferrites with low open porosity and relative density up to 99% of theoretical. Tab. 2, ill. 3., bibliography: 4 titles.
It is shown that the principles of directed control of the process of forming the structure of materials by modifying their compositions with eutectic additives are valid not only for ceramics based on aluminum oxide, but also for ceramic materials based on ZrO 2 . The considered approaches to the creation of energy- and resource-efficient technologies serve as a reliable basis for intensifying technological processes, reducing costs, and improving the quality of finished products. On the basis of zirconium dioxide by introducing corundum and a eutectic additive in the CaO - ZnO - Al 2 O 3 - SiO 2 system, a material with a fine crystalline structure has been developed , tensile strength in bending 800 ±; 30 MPa, with a sintering temperature of 1500 ° C, promising for use for structural purposes. Tab. 4, ill. 5, bibliography: 7 titles.
In the corundum-sillimanite form, after pouring a high-alloy alloy into it, the phase composition changes, and the chemical activity of the form increases. Investigations of the phase composition of distensillimanite after firing and after mold casting have been carried out. It is proposed to add alumina to distensillimanite and to bake the mixture at a temperature of 1643 K. This will cause the formation of mullite and have a positive effect on the quality of the mold. The new refractory powder can be used to form the facing layer of the ceramic mold. Il. 2, bibliography: 11 titles.
The sintering process of powder workpieces based on oxide ceramics is considered from the standpoint of diffusion mass transfer. In practice, two types of powders are used, differing in manufacturing methods. As a rule, the coarser-grained of them is traditionally obtained by mechanical grinding, another, characterized by a high degree of dispersion and a high content of various kinds of defects in the crystal lattice of particles, by chemical methods, such as precipitation from solutions, heterophase interaction, cryo- and plasma-chemical treatment, etc. .d. It is shown that during sintering of billets, their compaction and hardening is carried out according to various physical mechanisms. Bibliography: 14 titles.
The results of mathematical modeling of the process of ceramic molding by hot casting are presented. The calculated data describe changes in the state of aggregation of a thermoplastic slip as it cools in the forming cavity. Foundry characteristics are obtained that ensure uniform properties of a thermoplastic slip when molding ceramics by hot casting. Il. 5, bibliography: 7 titles.
The issues of thermal dissociation of silicon and iron oxides, which are part of corundum-sillimanite ceramic molds, which are used for casting with heat-resistant alloys at high temperatures, are considered. Theoretical studies have determined that the silica, which is part of the ceramic mold, has a low resistance to thermal dissociation at 1873 K. It has been established that iron oxide will intensively evaporate in the melting zone in the range at a reduced pressure of 0.65 - 1.33 Pa. This phenomenon increases the reactivity of the ceramic mold in the zone of contact with heat-resistant alloys and is one of the sources of contamination of the cast surface. Tab. 1., bibliography: 3 titles.
