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The possibility of using diatomite from the Ilyinsky deposit as an unshaped thermal insulation for open risers of castings from aluminum alloys of different alloying systems: technical aluminum A5, AK7, AMg10, VAL10 has been studied. It was found that when the continuity of the oxide film on the surface of a diatomite particle is broken, an exchange reaction occurs with the formation of a silicon transition layer. Since silicon is wetted by aluminum, the diatomite particle sinks in the melt, forming a blockage. As a criterion for the continuity of the oxide film, it is proposed to use the Pilling‒Badworth factor of the alloy components. It has been shown that a high level of the Pilling‒Badworth factor, even at a low content of the component (~ 1 %), leads to the formation of blockages. Ill. 6. Ref. 12. Tab. 1.

Исследовано влияние скорости обжига обогащенного каолина Кыштымского месторождения на свойства шамота. Спецификой каолина Кыштымского месторождения является петрографическое разнообразие исходных пород, что отрицательно сказывается на его качестве как огнеупорного сырья. Изучены пластические свойства каолина, позволяющие формовать брикет без дополнительного использования связующих, включая воду. Исследования скорости, конечной температуры обжига и длительности выдержки при конечной температуре показали, что скорость подъема температуры в процессе обжига шамота несущественно влияют на качество получаемого шамота. В то же время повышение конечной температуры обжига и выдержки существенно влияет на качество и фазовый состав шамота, закономерно снижая его водопоглощение, увеличивая выход муллита и уменьшая количество непереродившегося свободного SiO2. Установлено, что максимальная температура обжига обогащенного каолина Кыштымского месторождения на шамот составляет 1350‒1400 оС, скорость подъема температуры 35‒45 оС/мин.

На основе алюмосиликатного сырья Республики Казахстан предложена технология получения сверхплотных алюмосиликатных огнеупоров с повышенной шлакоустойчивостью для тепловых процессов утилизации фторсодержащих углеродистых отходов. Использование «керамической» технологии позволяет получать структуру с водопоглощением менее 1 % как у шамота, так и у огнеупорных изделий с разным содержанием Al2O3.

The composition and properties of two types of calcined magnesium oxide powders, differing in chemical composition, are investigated. The difference in chemical and phase composition determines the different behavior of powders during firing, which is smoothed only at a temperature of more than 1850 °C. The microstructure of the obtained briquettes differs in the amount of glass phase, the type and size of pores, as well as the size and quality of the crystals of the periclase. From the studied powders of decarbonized magnesium oxide without sintering additives, a briquette with an apparent density of at least 3,35 g/cm3 required to obtain high-quality products can be obtained only at a firing temperature of at least 1850 °C with an exposure at the final firing temperature of at least 2 hours. Ill. 2. Ref. 14. Tab. 4.

The influence of hydrothermal action on the physical and mechanical properties of ZrO2–Y2O3(3 mol%) ceramics was investigated. The properties of specimens sintered at 1350°C in air and at 1850°C in vacuum followed by oxidative annealing at 1200°C in air were compared. The characteristics of specimens sintered at 1850°C were shown to be practically unchanged after hydrothermal treatment while specimens sintered at 1350°C showed a significant drop in strength and hardness of about 40 – 50%.

The processes of obtaining ceramic microporous diaphragms based on aluminum and zirconium oxides have been studied. The diaphragm test results for long-term corrosion resistance are presented. It was shown that a ceramic material based on zirconium and aluminum oxides obtained at 1350 °C with linear shrinkage of 7,5 % has an open porosity of 49 % and a flexural strength of 48 MPa. The diaphragms obtained from this material can withstand pressure up to 1.0 MPa and can work under the conditions of electrolysis of aqueous solutions of chlorides for at least 40,000 hours.

The paper discusses the multipurpose use of technogenic and natural raw aluminous materials for extracting valuable components, while solving environmental issues. The authors analyzed the process of granulating kaolin, obtained from the Ural region, which involves the addition of aqueous sulfuric acid solution and subsequent firing of the granules. Sulfuric-acid leaching of kaolin-containing raw materials at various acid concentrations and precipitate production times was considered. A certification of the obtained aluminum hydroxide powders was performed.

Samples of aluminosilicate refractory after operation in the shaft and in the hearth of a coke-gas cupola were investigated; this cupola was used for smelting of cast iron with spheroidal graphite using carbon wastes from aluminium electrolysis production as a reducing agent. Use of only fluorine-containing carbon wastes as a solid fuel in cast iron production allows to utilize hazardous man-caused wastes, improves the economic performance of production and has influence on resistance of fireclay refractories. It was established that the products acquire a distinct zone features during the service, due to penetration of the components of gas and liquid phases and the effect of low-boiling components of carbon-containing wastes. Upon that, changes in the structure along the distance from the working space are complex ones in lining thickness and in concentration of volatile components in the “cold” parts of the lining. Permanent character of the mullite content in different zones of fireclay products can be traced, as well as a slight increase in the less altered zone, despite the different service conditions. Absence of alkaline and fluoride phases in the zones of refractory products in the pores and structure of the fireclay refractory was established, due to migration of these gaseous phases into the working space of the cupola with their subsequent removal with furnace gases. Additional development of mullite in certain zones of refractory was revealed, resulting by its synthesis from alumina that did not react during fireclay refractories manufacture under the mineralizing action of a fluorine compound. Use of fluorine-containing carbonaceous wastes as a solid fuel in cast iron production makes it possible to utilize hazardous man-caused wastes, improves the economic performance of production and has slight effect on resistance of aluminosilicate refractories in the conditions of a coke-gas cupola. © SIDORINA E. A., ISAGULOV A. Z., KASHCHEEV I. D., ZEMLYANOY K. G., 2022.

We present the results of investigation of the regularities of sintering and properties of corundum ceramics based on alumina with admixtures of ultradispersed powder of Al2O3(Al2O3 UDP) synthesized by the electrochemical method. It is shown that, as the firting temperature and the concentration of Al2O3 UDP increases, we observe a regular elevation of the linear shrinkage, microhardness, and ultimate strength in bending of the ceramics (the maximum values attained at 1550°C are as follows: 27.8%, 17 GPa, and 340 MPa, respectively). The introduction of Al2O3 UDP makes it possible to get an apparent density of the ceramics equal to 3.87 g/cm3 even at 1550°C.

Requirements for special-purpose alumina for the ceramic, electronic and refractory industries are considered. Analysis and comparison of acidic methods for preparing alumina from the point of view of efficiency, adaptability and production safety are provided. The risks of alumina acidic production methods are estimated. The advantage of the sulfuric acid method versions is substantiated.

The results of studies of the structure, phase composition and specific surface area of powders based on zirconium dioxide obtained by the method of thermal decomposition of a mechanical mixture of hydroxide and a stabilizing additive are presented. The forming and sintering of ceramic samples obtained from calcined powders were studied, as well as some properties of the ceramics. It has been shown that fine-grained dense high-strength ceramics with a flexural strength of 860 MPa and microhardness up to 12 – 13 GPa can be obtained from the synthesized powders.

Results are provided for thermal cycling tests of a number of highly refractory products. It is shown that periclase products from fuzed powders coated with ZrO2 are the most resistant to cyclic variable thermal loads. The structure of corundum products in the process of thermal cycling tests deteriorates significantly due to recrystallization and the formation of new phases. In order to organize the lining and test unit heat exchange fittings operating under conditions of variable loads in pulsed piston units objects made from fuzed periclase powders modified with ZrO2 are recommended.

The results of studies of the structure, phase composition and specific surface of powders based on zirconium dioxide obtained by the method of thermal decomposition of a mechanical mixture of hydroxide and a stabilizing additive are presented. The forming and sintering of ceramic samples obtained from calcined powders, some properties of ceramics were studied. It has been shown that finegrained dense high-strength ceramics with a flexural strength of 860 MPa and microhardness up to 12‒13 GPa can be obtained from the synthesized powders. Ill. 2. Ref. 12. Tab. 3.

The effect of natural additives on aluminosilicate sintering capacity is studied. It is demonstrated that addition of natural alkaline aluminosilicates with predicted viscosity and amount of melt makes it possible to prepare stronger ceramic materials.

This article considers an effective way of processing natural and technogenic magnesium-containing materials, which will release magnesium oxide and magnesium sulphate for the production of magnesian cement. Using this method, pure magnesium oxide, magnesium sulphate and magnesium sulfate have been obtained, the study considers the properties of magnesian cement with differeng magnesium oxide production conditions. Keywords: non-conventional magnesium containing raw materials, technogenic materials, magnesian cement, hydrochemical processing, ammonium hydrosulfate

This article considers an effective way of complex alumina-containing materials of natural or technogenic origin processing with obtaining a whole complex of raw materials: alkali-free highly active aluminum hydroxide, iron hydroxide, aluminum hydroxide, etc. In laboratory conditions the alumina raw materials behavior in the thickening, washing, filtration processes were checked. The optimal parameters of the processes were selected as a result of conducted research. Keywords: non-conventional alumina raw materials, technogenic materials, hydrochemical processing, ammonium hydrosulfate, environmental friendliness, efficiency

The possibility to produce the vibro- and self-flow lowcement periclase concretes was investigated in the article. It was shown that when the concrete mixture is prepared in conventional conditions the aggregate and the fne ground component based on the fused periclase hydrate very little if any: over three days of the concrete curing the brucite content doesn't exceed 1 %. The data received can be used as the basis for the further development of the magnesia concretes with advanced properties.Ill.1. Ref. 17. Tab. 2.

The effect of natural additives on the sintering ability of an aluminosilicate material has been investigated. It is shown that the introduction of natural alkali aluminosilicates with a predicted viscosity and amount of melt allows to obtain more durable ceramic materials.Ill.6. Ref 4. Tab. 2.

The alumina-silicate material's granular composition effect on its sintering behavior was investigated in the article. It was shown that the average particle size decreasing, the chemical and material compositions being equal, allowed to prepare stronger materials.Ill.2. Ref. 6. Tab. 4.

The effect of aluminum silicate material composition on its sintering capacity is investigated. It is shown that a reduction in average particle size with the same chemical and substance compositions makes it possible to prepare strong ceramic materials.

Results are reported on the sintering ability of pure synthetic magnesium oxide (MgO) using variously pretreated eutectic sintering additives. It was established that the sintering ability of synthetic MgO was affected by the type of precursors used to prepare both the MgO and eutectic sintering additives. The best sintering ability was observed for MgO prepared from magnesium bicarbonate. The sintering additive made of natural quartzite and technical aluminum and magnesium hydroxides was most effective.

We present the results of investigations of the process of sintering and the changes in the properties of corundum ceramics depending on the content and type of introduced highly dispersed Al2O3. The specimens are produced by the slip casting and sintered at various temperatures. It is shown that, for the other identical conditions, it is reasonable to use highly dispersed powders with spherical particles with an aim to improve the physicomechanical properties of corundum ceramics. In the production of dense ceramics, the shape of particles of highly dispersed powders does not have any significant influence on the decrease in the temperature of sintering.

Substance, chemical, grain size compositions, and properties are determined for Poletaev deposit kaolin. Results are provided for a study of the possibility of preparing a dense aluminosilicate filler for refractory and ceramic material objects. Addition of aluminosilicate material makes it possible to prepare filler with an increased Al2O3 content.

Results are provided for a study of diatomite of the Il’insk field (Sverdlovsk region) for preparation of unmolded insulation materials and their use as heat insulating materials in crucibles with molten aluminum. Use of diatomite as a heat insulating material makes it possible to reduce power consumption during holding molten aluminum in the resistance furnace crucible, prevents development of hydrogen porosity, and does not lead to melt saturation with silicon.

Methods are described for producing aluminium-magnesium spinel by solid phase synthesis using commercial alumina and caustic magnesite. It is proposed to replace commercial alumina by dust deposited in the aspiration system for an aluminum hydroxide calcination rotary furnace that makes it possible to exclude the stage of milling alumina. Methods are provided for spinel synthesis in electric arc furnaces with block melting and pouring of a charge. The effect of the MgO/Al2O3 ratio in electrically melted material on its properties, method for adding a charge to an electric furnace during melting for pouring, features and properties of spinel materials with subsequent molded object sintering, are studied.

Possibilities are considered for using discrete carbon fibers as a reinforcing element within the structure of carbon-containing refractories. Results of laboratory and pilot plant tests are provided.

The investigating results are given in the article for both the sintering and the corundum ceramics' properties change depending on the inserted highdispersed Al2O3's content and kind. The samples were prepared by means of the slurry casting and were sintered at various temperatures. It was established that all else being equal the highly-dispersed sphericalshaped powders are the most advantageous to use for the corundum ceramics' physical and mechanical properties improvement. The shape of the highlydispersed powder doesn't influence significantly on the temperature reducing while preparing of the dense ceramics. Ill. 4. Ref. 12. Tab. 2.

The material, chemical and grain compositions as well as the properties of the Poletaev' deposit's kaolin were studied. The possibility is investigated to prepare on base of this kaolin the dense aggregate for the refractory and ceramic materials production and the investigating results are given in the article. The introduction of the aluminasilicate materials allows the aggregate obtaining with the elevated Al2O3 contents. Ill. 6. Ref. 3. Tab. 6.

The change in LTEC is analyzed on heating and cooling ceramic materials of the Al2O3–ZrO2 system in the range 200 – 1500°C. The effect of structural and phase components and measurement regime (heating/cooling) on form of the relationship Δl/l 0 = f(t), and also the dependence of LTEC on composite chemical composition are established. Results obtained are discussed from the point of view of material phase composition and published data are analyzed. Data are provided for average and true LTEC values.

Results are provided for study of a series of high refractoriness objects for thermal shock resistance and determination of their actual heat capacity. It is shown that under high temperature conditions and sharply varying thermal loads good resistance develops for objects with the highest ratio of heated surface area to volume. Two-phase materials demonstrate the best thermal shock resistance. Periclase objects with a protective coating based on ZrO2 have thermal shock resistance comparable with that of zirconia objects.

Microstructure, phase composition, and physicochemical properties of domestic and imported carbon materials used in refractory concretes are studied. It is established that graphites of different origin have different surface morphology, crystal lattice structure, and wetting capacity.

The possibility is considered of using carbon fibers as a reinforcing element within the structure of periclase-carbon refractories. Laboratory and industrial test results are provided.

A simplex-lattice method is used for planning an experiment for sorting the grain size composition of high-alumina chamotte grade RASC in order to prepare mullite material. Optimum chamotte grain size composition is established proving an improvement in operating properties.

The working layer of a ladle furnace unit (LFU) lining made from periclase-graphite refractory is most strongly subjected to the effect of corrosion factors that concern thermal, mechanical, and chemical action. The strongest destructive effect on a lining is the chemical factor. This article provides results of studying the effect slag phase composition on chemical breakdown of a LFU periclase-graphite lining.

are provided for a study of the effect of different graphites GE-1 and GCh (Russian Federation), Falke 94100 and Falke 9280 (Brazil), +592 (PRC), +595 (Madagascar), and FLS 897 (Norway) on physicochemical properties of periclase- and corundum-graphite refractories. It is shown that the type of graphite affects charge properties even in the preparation stage, and object physicochemical properties.

Results are provided for a study of the microstructure, phase composition, and physicochemical properties of domestic and imported graphites for the refractory industry. It is established that graphites of different origin have a different morphological surface, crystal lattice structure, and oxidation resistance.

The properties of three samples of low-melting clays (Tyumen Oblast) were investigated for the purpose of application in the production of ceramic building brick. It was determined that the clays of the samples Nos. 1 and 3 can be used to produce No. 150 clayey, frost-resistant, face brick by the plastic molding method. Clay from sample No. 2 can be used to produce clayey, frost-resistant, face brick with the introduction of additives that improve the drying properties.