Results of preparing Portland cement by low-energy technology using technogenic raw materials are presented. Coal mining waste and tephritobasalt in a ratio of 1:1 are used as the clay component, and granulated lead slags are used instead of scarce pyrite cinder. Correlation of the influence of charge compositions, saturation coefficient, silicate and alumina moduli, firing regimes with chemical and

The specifics of the drying process of the lining of high-temperature units are described, in particular, the average drying rate is analyzed. The adequacy of the proposed mathematical dependencies is confirmed by comparing the results obtained by calculation, and experimental data obtained at the laboratory bench. The research results can be used to develop a schedule for heating high-temperature

The distribution of iron ions during firing of acid-resistant ceramic materials based on production waste is established using the Mössbauer effect. It is revealed that in samples containing an increased amount of iron oxide (17 – 18%) strength and frost resistance are better than in specimens containing 6 – 7 % Fe2O3. Calculation of the areas of the doublets of the spectrum showed that iron compounds

Processes for preparing ceramic microporous diaphragms based on aluminum and zirconium oxides are studied. Diaphragm test results for long-term corrosion resistance are presented. It is shown that ceramic material based on zirconium and aluminum oxides prepared at 1350°C with linear shrinkage of 75% has open porosity of 49% and ultimate strength in bending of 48 MPa. Diaphragms prepared from this material

The possible reuse of powder Al2O3 waste formed in manufacturing of ceramic refractory products by plasma spraying was studied. The powder alumina waste was found to be individual particles α- and γ-Al2O3 and their conglomerates and also included iron oxides in the form of Fe2O3 and Fe3O4. It was shown that the plasma-spraying powder waste had to be purified of Al2O3 conglomerates and iron oxides in

The urgency of the problem of shrinkage phenomena during hearth firing, contributing to joint opening and crack formation, is demonstrated. Contemporary methods and means of studying expansion/shrinkage of hearth mixes during firing are analyzed. Expansion/shrinkage of hearth mixes, differing in the ratio of the carbon component (anthracite) and artificial graphite within their composition, is investigated

The analysis of the main regularities of distribution of the material in stages of the vertical cascade makes it possible to substantiate the optimality of some important parameters of separation. It is shown that the best efficiency of separation can be attained as a result of feeding of the source material into the central part of the cascade. In this case, the number of stages should be restricted

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

We perform the analysis of the methods aimed at improving the energy efficiency of the electric modular-launch furnaces for firing of vermiculite. The first method is reduced to the analysis of the energy efficiency of the original six-module furnace with heat emitters made of U-shaped nichrome and structural transformation of the furnace unit with reinstallation of the least efficient bottom module

We present a comparative analysis of peripheral and end machining using a diamond tool and demonstrate the current interest in using modular segments for end grinding..We discuss the design characteristics of the modular segments of the tool for end grinding of hard materials: concrete, ceramics, and natural stone, and propose a preliminary classification of materials into abrasive and non-abrasive

The article explores the dust dynamics in an aspiration hood equipped with various thin mechanical shields. A differential equation of motion of dust particles is used to calculate their trajectories, and the velocity fields of the air flow are calculated by the method of boundary integral equations. The influence of different mechanical shields on the maximum diameter of dust particles is determined

A method for modeling the electric glass melting process, which allows obtaining information about the commonality of electric and thermal processes occurring in the glass mass inside an electric glass-melting furnace, has been developed. The melting tank of the furnace is made of electrically conductive chromium oxide. The study was performed by way of modeling using an EHDA integrator, which resulted

An original procedure is used to study the kinetics of surface layer structural changes of a ceramic component surface layer outside the area of contact interaction during operation. The main features of this process are established and the effect the degree of defectiveness of the initial surface layer on changes that occur is revealed.

The processes of forsterite, enstatite, and talc treatment by ammonium fluoride have been studied. The phase-formation processes occurring during firing of fluorinated minerals were studied. It was established that structural silica of the minerals reacts with ammonium hydrogen difluoride with the formation of ammonium hexafluorosilicate, sublimation of which leads to removal of structural silica from

Compositions, technology features, and the main properties of cement-free refractory concretes (CFRC) based on a silica-sol binder are considered. Concretes of high-alumina and corundum compositions of CFRC, as well as in the Al2O3–SiO2–SiC–C system predominate in this group. Improved thermal and thermomechanical properties of CFRC compared with the properties of LCRC are largely due to mullitization

A single-phase material based on the complex oxide Ca2Fe2O5 doped with bismuth was synthesized by glycine-nitrate combustion. Characterization by x-ray diffractometry, helium pycnometry, scanning electron microscope, and elemental analysis showed that the material was isostructural to brownmillerite. The optimum temperature for the synthesis of the material was about 650°C and the material had thermal

A new approach is presented for processing leucoxene concentrate through vacuum silicothermal reduction of titanium and silicon oxides using commercial-grade silicon as a reducing agent. It is shown that reactions occurring during a high-temperature process are accompanied by formation of SiO gas resulting in desiliconization of leucoxene concentrate. The best desiliconization degree of 82% is achieved

Dense ceramic materials of silicon carbide with high mechanical properties are obtained by reaction sintering. The effect of different dispersed compositions of silicon carbide powders on the microstructure, grain size after sintering, and physical and mechanical properties is shown.

The results of experimental studies of the corrosion resistance of aluminum and its alloys modified with ceramic coatings based on the microarc oxidation method in some aggressive environments are presented. The mechanism of destruction of the coating is considered. Recommendations on increasing corrosion resistance are given.

Results of studies of the structural and mechanical properties of aluminum-zirconium composite ceramics with different ratios of Al2O3 (white electrofused corundum F-1000) and 3Y-TZP (tetragonal polycrystalline ZrO2 stabilized with 3.0 mol.% Y2O3) obtained by semi-dry molding followed by free sintering are presented. Introduction of a eutectic additive to the ceramic composition leads to formation

This article presents the results of studies that determine the changes in the phase composition and structure of dinas refractories under the operating conditions of coking coal. Their changes are attributed to differences in the temperatures and rates of dinas cooling/heating during the cyclic loading/unloading of coked materials, the conditions of refractory contact with an operating environment

The paper presents the results obtained for the distribution of heat flux incident upon a refractory plate of a hypersonic flight vehicle moving at space velocities at various distances from the Earth’s surface. The paper also provides the results of studying phase transitions in the near-wall boundary layer occurring during the hypersonic flow over the ablating surface. The effect of the catalytic

Anew design of suspended radiating elements is developed for heating systems of electric furnaces with moving hearth platforms and modular-trigger furnaces. The transfer of radiant energy on the surface of firing modules and on the flow of expansible vermiculite is simulated. Analytical dependencies are obtained to calculate the temperatures of radiating elements, a refractory base, a heat-insulating

To the article “Strengthening Oxide–Oxide-Free Materials by Incorporation of TiC–ZrC Solid Solutions into Their Structure during Spark Plasma Sintering of Initial Powder Mixtures under High Compression Loads,” by A. V. Hmelov, Vol. 60, No. 5, pp. 486 – 494, January, 2020

An explanation of processes occurring during preparation of high-density micro- and nanogranular ceramics without using external pressure on the basis of published data is proposed. It is well known that pore growth commences after the start of transition of open into closed pores that begins with about 30 % open porosity. It is necessary to maintain open pores to the maximum possible sintered ceramic

A new approach to the homogenization of the reaction mixture is presented consisting in the creation of glass-ceramic precursors in oxide systems containing enough components for the joint synthesis of carbides and borides mixed at the molecular level. By the joint carbothermal reduction of glass-ceramic precursors in vacuum at 1600 °C fine mixtures in B4C–SiC–MB2 systems (M—Ti, Cr, Zr) without or

An experimental study was performed to break down a sample of a by-product of the autoclave production of artificial quartz crystals using a pilot sandblasting system. The scheme and parameters of the system are provided.

The effect of cold-ramming hearth mix density on the annealed mix dynamic elastic modulus is investigated. It is shown that analysis of the elasticity modulus curves makes it possible to determine the area of optimum hearth mix compaction within which it has a mechanical property level comparable to hearth blocks.

Compositions for producing silicon-carbide materials with a nitride binder in which the initial binders were artificial ceramic binders based on silicon and silicon carbide were studied. The influence of the firing regime and binder composition on the main physicomechanical characteristics and microstructure of samples after nitriding firing was studied.

Cement matrix samples were prepared using mechanical and chemical activation of two types of granulated blast-furnace slag with a fly ash admixture. We studied the chemical, phase, and granulometric composition; specific surface area; morphology; and strength of such slags, as well as the effect of the alkali introduction method on compressive strength.

Friction units of modern power turbines require the use of special materials with stable and low coefficients of friction under extreme conditions. Antifriction carbon-graphite materials, in particular isotropic pyrolytic carbon, are most successfully used for these purposes. Isotropic pyrolytic carbon was found to have a lower friction coefficient and wear rate than ATG-S antifriction graphite. The

The effects of Wand Mo power additives during spark-plasma sintering of compositions at compression force 60 MPa at 1200 – 1600°C on the phase composition, microstructure, crystalline-phase grain size, relative density, linear shrinkage, physicomechanical properties, and the linear correlation of the elasticity modulus and fracture toughness of mullite–ZrB2–β-SiC–TaC samples were studied. The synthesized

Results from studies on the modification of Nb–Cr–Mo–Si–B composites with Mo chalcogenides are presented. Use of MoS2 and MoSe2 as integral parts of multicomponent oxygen-free compositions was shown to have positive effects due to the formation of highly active elemental Mo species resulting from their dissociation that determined the high heat resistance of coatings formed from them.

The paper discusses the layered heat-resistant coatings for aerospace applications obtained by atmospheric plasma spraying (APS) technique. The following coating material compositions were selected, wt. %: 1 — 20(ZrO2–8Y2O3) + 80MoSi2; 2 — 10(ZrO2–8Y2O3) + 90MoSi2. As the sublayer thickness decreases and MoSi2 content increases, the strength of the coated sample becomes higher. It was established that

An original method is used to study the surface layer structure of a VOK-71 ceramic object after diamond grinding. Kinetics of changes in ceramic structure in the contact interaction area during operation are studied.

The results of studies on the preparation of titanium carbosilicide with porosities of 20, 40, and 60% are presented. Experimental samples were obtained using a pore former in the form of NaCl crystals. Sintering of porous samples at temperatures up to 1300°C was characterized using thermomechanical analysis. The pore structure was studied at the macro- and micro-levels using the method of optical

Results are provided for studies of self-sintering refractory mix preparation. New technology is proposed for their manufacture. The basis of the mixes obtained is barite-containing components (barite or witherite concentrates). Good chemical resistance, refractoriness, mechanical strength, hardness and wear resistance determine the scope of their application, i.e., manufacture of refractory products

Tetragonal solid solutions based on the TiO2–CeO2–ZrO2 system stable up to 1,350°C were obtained. A method of pH titration of the initial salt mixture was used to study the competitive hydrolysis and precipitation processes in a three-component system. The microstructure and specific surface area of the precursors after synthesis were studied. Adetailed study of precursor phase formation in the range

We present a literature survey on the operation of tundishes and the possibility of continuous casting of steels in the “open start” mode. On the basis of the results of experimental studies, we select a composition of refractory castable for the starting funnel of the metering nozzle.

We study the problem of evaluation of the influence of design of the metal receiver of a large-capacity tundish of slab continuous-casting machine on the decrease in the turbulence of flows in the case of deviation of the metal stream from the required position in the process of casting. We present the results of computer simulations of various types of deviations from the target point of input for

We present the data on the improvement of carbon cathode lining materials used in the production of aluminum by electrolysis and discuss some issues from the materials science related to the technology of production of carbon cathode materials.

Matrix systems of many types of cement-free refractory concretes (CFRC) have a certain content of highly dispersed components of silica composition, i.e., silica sols, SiO2 nanoparticles (in HCBS of different compositions), as well as fine silica (“microsilica” MS). The degree of their dispersion and hydration (lyophilic nature), determined by their specific surface, is considered. It is shown that

The results of modeling the processes of capturing harmful emissions from galvanic baths or other tanks with an open surface are presented. An approach based on a numerical determination of the concentration of contaminated substances in the working areas of the room is proposed to evaluate the effectiveness of airborne suction. The fields of air velocity and concentration of harmful vapors in the

The regime of two-phase ascending flow in which the solid phase can move in both directions is called critical. The analysis of such flow from the standpoint of statistical approach made it possible to establish key parameters characterizing such mass transfer process. The chaotizing factor and solid phase mobility are among the energy characteristics of this process. It was shown that two-phase systems

The article is devoted to the preparation of ecologically clean composites by powder metallurgy and the study of tribological properties. Tribological tests are conducted in an MMW-1 friction machine with vertical block using a “pin-on-disk” mechanism, and a steel disk as the counterbody. It is established that test specimen tribological properties remain unchanged with different loads.

A coating for a Si3N4 ceramic end mill was selected based on the analysis of the results of numerical simulation of the stress-strain behavior of its cutting edge. It was found that the TiC coating is more effective than TiN coating, and reduces the temperature and stresses of the cutting edge of the mill under the transient thermoelastic conditions. This is critical for reducing the intensity of micro-chipping

It was found that TiC coating is more effective than TiN coating, and stabilizes the temperature distribution and structural heterogeneity of stresses in the surface layer of Si3N4 ceramics adjacent to the coating. It is recommended to apply TiC coating to Si3N4 ceramic end mills intended for milling spatially challenging surfaces of nickel alloy products.

The main technological indicators and factors for improving the quality and economic efficiency of fused-cast baddeleyite-corundum refractory production are given. Materials with high corrosion resistance, glass-phase precipitation temperatures above 1450°C, and minimal tendency to precipitate defects in the molten mass could be produced by optimizing the BC-33 refractory composition while observing

The effect of cryoprocessing on stabilization of VK6 hard alloy after irradiation by 5-MeV electrons was studied. Samples of similar microstructure were selected by measuring the structurally sensitive coercivity. Irradiation of VK6 hard alloy by fast electrons increased its microhardness by 30% as compared to the original samples. The microhardness of hard alloy VK6 samples after irradiation by fast

Electric heating regimes are determined for mixture self-compaction. Three periods of change in its specific electrical resistance are noted due to the water absorption capacity of the plant supplement. The relationship between electrophysical processes and their influence on mixture compaction is described. A scheme of drying raw material according to the moisture loss rate is considered. A firing

We perform the analysis of the available empirical compaction equations for fine-fraction materials. By modeling separate stages of the process of compaction for selected groups of materials, we reveal the advantages and drawbacks restricting the fields of their possible applications. It is shown that the compaction equation proposed at the Z. Nekrasov Institute of Ferrous Metallurgy of the NAS of

On the basis of refractory bauxite and very fine quartz glass (VFQG) by means of stagewise combined wet grinding HCBS are prepared having a low moisture content and good binder properties that are achieved due to an optimum content within them of very fine particles (nano-particles and colloidal component). These HCBS are used as a matrix system in the manufacture of many forms of ceramic concrete

The influence of the deflocculant of the Russian company Polyplast-UralSib LLC on the properties of trough and self-flowing masses for lining the working surfaces of thermal units is considered. It is established that introduction of a deflocculant in an amount of 2.0 wt.% into refractory concrete masses ensures satisfactory workability of the mass and the required physical and mechanical properties

An explanation is proposed for processes that occur when producing high-density micro- and nano-granular ceramics without the use of external pressure based on the data accumulated in publications. It is well known that pore growth commences after the start transition of open into closed pores that begins with about 30% open porosity. It is necessary to maintain open pores to the maximum possible total

An explanation of processes occurring during production of high-density micro- and nanogranular ceramics without the use of external pressure is proposed on the basis of accumulated published data. It is well known that pore growth commences after the start of transition from open into closed pores, which begins with about 30% open porosity. It is necessary to maintain open pores to the maximum possible

Amethod of calculating pressure losses during pneumatic transport with the objective of choosing the most efficient operating mode, which allows reducing the consumption of compressed air, is observed. It has been found that the generally used formulas for calculating pressure losses along the path, determined as the sum of the pressure losses for pure gas and material, do not explain why the initial

The design of a device for supplying differentiable flows for cooling products with different enthalpy values is presented. An algorithm has been developed to control the system for extracting hot air from the cooling zone at the junction of the cooling and firing zones for feeding into the mixing chamber with atmospheric air and then to the dryer. At the same time, part of the selected hot air enters

A new device for moving walking machines has been proposed, which allows to reduce energy consumption for dragline movement by eliminating the friction of the support base on the ground while maintaining the step size and providing a given direction of its movement. The thermal engineering calculation for the hydraulic dragline walking mechanism is presented with the aim of using the heat generated

We study the problem of evaluation of the influence of design of the metal receiver of a large-capacity tundish of slab continuous-casting machine on the decrease in the turbulence of flows in the case of deviation of the metal stream from the required position in the process of casting. We present the results of computer simulations of various types of deviations from the target point of input for

Amethod is developed for rapid evaluation of the wear resistance of ceramic materials by changing the roughness parameter Rt. The method is tested successfully on samples of alumina ceramics made according to various production conditions. Analysis of the method provided is compared with results of ceramic material tribological tests for abrasion.