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

The influence of nanosized ZrO2 and Al2O3 particles on the physicomechanical properties (elasticity modulus, flexural strength, microhardness), phase composition, and microstructure of materials based on Si–B4C–ZrB2 was studied. A borosilicate glass-forming melt that encapsulated the starting components was obtained by reactive heat treatment in air in an electric furnace [1]. Gradient materials in

The formation of the structure of lightweight materials is governed by the complicated processes running in complex three-phase systems. We study the procedure of electric heating as a control factor guaranteeing the possibility of forced lowering of the moisture content of foam masses and the acceleration of the processes of structure formation. Amodel of gas pores with force vectors is proposed.

The authors have studied the properties of thermal insulation materials obtained based on expanded vermiculite and liquid-glass binder produced by foaming with a gas-generating (foaming) agent and volumetrically solidified by reacting it with sodium fluorosilicate. The quantitative binder-to-filler ratio was determined, which allows forming the products by casting and obtain materials with various

Analysis of the mechanism of quarry waters contamination during drilling and blasting preparation of asbestos containing raw materials under the influence of industrial and natural factors is carried out that can serve as a basis for making specific technological decisions ensuring a decrease in the negative impact on the environment during the development of chrysotile asbestos deposits. The dependence

Results of a comprehensive study of the material composition and microstructure of 20 skull samples taken after blowing out AO EVRAZ NTMK blast furnace No. 6 are provided. More than 30 mineral and metal phases of different chemical classes are diagnosed in skull samples. Unlike the skull of blast furnaces of other metallurgical plants (NLMK, ZSMK), NTMK blast furnace skull has an abnormally high content

In an attempt to optimize a qualified ceramic material with enhanced and outstanding characteristics, the current work aims to study the processing of dense Si3N4 based ceramic composites by the hot pressing (HP) method. The proposed material consists of an equimolecular mixture of α- and β-Si3N4 with the addition of various amounts of MgO–Al2O3 spinel as sintering additive. Investigation of the different

The regularities of the behavior of the intensity of stresses in the surface layer of ground Al2O3–TiC ceramics under the action of force loads are established on the basis of the main concepts of computer engineering. The formation of microstructural stress concentrators on the interface of the plastically deformed layer with the original ceramics is discovered. These concentrators may serve as causes

Heat-resistant slip coatings of the ZrB2–MoSi2–SiC system on CCCM were examined for protection of aerospace technology elements from oxidation. The following compositions (mass%) were studied as coating materials: 55 ZrB2 + 25 MoSi2 + 20 SiC (ZSM25), 50 ZrB2 + 30 MoSi2 + 20 SiC (ZSM30), and 45 ZrB2 + 35 MoSi2 + 20 SiC (ZSM35). Heat-treatment modes were elaborated for the coatings. The optimal method

A porous catalytically active membrane based on α-Al2O3 was synthesized. Powdered additives of the eutectic composition of magnesium oxide and silicon carbide were added to the initial corundum filler to synthesize a membrane framework with high open porosity and physical and mechanical characteristics that was pressed at 40 – 70 MPa followed by sintering in process combustion mode. Additives of Re2O7

Comparative data are provided for synthesis of cubic boron nitride (CBN) grade Elbor in the Mg–B–N system using different catalysts in presses with a force of 25MN(DO044) during 1997 – 2009. Mechanical properties of different grades of Elbor CBN are compared with CBN powders of grades ABN (DeBeers) and CBN8 (China).

CFRC based on alumina hydraulic binders are similar with respect to hardening mechanism to low-cement refractory concretes (LCRC) and ultralow cement concretes (ULCRC). They are characterized by significant strengthening in the heat treatment temperature range 200 – 300°C and severe weakening in the range 600 – 1000°C. By introducing silica sols or microsilica into their composition it is possible

The layered cermet Al–Al2O3–Al4C3 was obtained by liquid-phase sintering under vacuum of powder blanks made of highly disperse PAP-2 industrial brand Al powder consisting of flaky particles of submicron thickness. The appearance of the liquid phase was associated with the formation of an Al/Al4C3 eutectic melt at 630°C as a result of the reaction of Al with its carbide. Lamellar nanoscale Al4C3 crystals

We establish the regularities of thermal and stressed states of the surface layer of ground Al2O3–TiC ceramics subjected to the action of thermal loads. It is shown that the role of the thermal factor in the mechanism of fracture of this layer manifests itself in the formation of unfavorable microstructural stress concentrators.

The article considers the construction of an integrated ventilation system that combines local exhaust ventilation of welders’ workplaces and general exchange ventilation of premises. Using the method of computer simulation, the air movement fields, air temperature and concentration of harmful impurities are calculated. A comparative analysis of the main types of stationary devices for local exhaust

The isothermal process of chemical vapor deposition for the densification with a SiC-matrix of organomorphic carbon-fiber preforms obtained by carbonization of compressed fibers of oxidized polyacrylonitrile is investigated. Such preforms are characterized by a high (up to 70%) porosity and uniform pore size (the reduced pore diameter ranges from several micrometers to tens of micrometers). Technological

Results of comprehensive research on the use of exhaust gases from an internal combustion engine (ICE) as the source of hot hydrocarbons instead of propane-butane or natural gas to reduce oxidative processes are presented. Introduction of hot hydrocarbons in exhaust gases from an ICE is shown to reduce significantly the redox potential of a plasma-torch plasma jet with respect to the sprayed material

Experimental studies are presented for choice of refractory concrete for a continuous casting machine tundish nozzle dispenser. Three types of refractory concrete are considered in the experiments governed by their basic thermal properties, and refractory concrete is chosen with the best performance. Nozzle dispensers are manufactured and approved under production conditions that demonstrate good results

A total thermal conductivity of a complex heat-insulating and slag-forming mixture has been calculated by accounting for the convective heat transfer component and thermal conductivity of the liquid oxide solution formed by melting the ingredients of the complex mixture. It was shown that the thermal conductivity of the complex mixture at an application temperature of 1,823 K remains at a rather low

Ceramic material taken from walls of the church of St. Mary (Spain) was studied. The elemental composition of the studied material showed an increased carbon content (15.42%), indicating that fuel was introduced into the raw material and contributed to uniform sintering and porosity formation inside the ceramic sample. Three types of pores were found most often in the studied sample: slit-shaped, isometric

The effects of Zr, Mo and Zr, Ta powder mixtures during spark-plasma sintering of compositions at pressing loading of 60 MPa in the range 1200 – 1600°C on the phase composition, microstructure, grain sizes of crystalline phases, relative density, linear shrinkage, physical-mechanical properties, and linear correlation of elasticity modulus and fracture toughness of mullite–β-SiAlON–c-BN samples are

On the basis of systematization of the results of investigation of the process of diamond grinding of Al2O3, TiC, Si3N4 –TiC, Y–TZP, and SiSiC ceramic specimens, we managed to identify some general and specific features in the structures of their surface layers. These features are used to make an adequate choice of the basic elements of microstructural model and to make some assumptions. The developed

A total complex resistance (impedance) method is used to study the electrophysical characteristics of (BeO + TiO2)-ceramics modified with TiO2 micro- and nanoparticles in an amount of 30 wt.% (BT-30). Dispersion of the actual ε′ and imaginary ε′′ components of the dielectric permittivity component and specific conductivity in the frequency range from 100 Hz to 100 MHz from room temperature to the boiling

A new modified two-module electric modular-pouring furnace with an upper heating system of heaters and an additional “zero” (non-electrified) module is considered. By eliminating the lower third firing module, a reduction of energy consumption by a third compared to the three-module prototype furnace was achieved. Suspended emitting elements, which are not only energetically more efficient than the

The main objective of this work was to explore the improved water dispersibility obtained in natural graphite after its surface treatment. The superior flowability of the aqueous suspension of an alumina-rich representative castable matrix incorporating that surface-modified graphite without prior sonication has been observed. The typical role of alumina-based thin coating on graphite has also been

We propose a concept of potential energy that describes the natural ability of foam systems to self-compaction under the complex action of electrohydrothermal force fields. The process of generation of the excess internal pressure in foam systems is studied both analytically and experimentally. The experimental data on the dynamics of temperature and pressure are obtained as a result of monitoring

The chemical composition and the amount of waste from coal preparation plants are analyzed. The main characteristics of the gasifying gas under various conditions of fuel combustion are studied. The impact of the carbon content in waste on the main characteristics of the gasification process is estimated. The analysis of the influence of various properties of the gas generated as a result of gasification

Thermodynamic modeling of phase diagrams of the FeO–MnO, MnO–MgO, MnO–Al2O3, FeO–MgO–MnO, FeO–MnO–Al2O3, and MgO–MnO–Al2O3 systems was carried out. The energy parameters of the theories of regular ionic solutions and subregular ionic solutions used in the simulation were determined. The calculation method used in this work allowed us to estimate the enthalpy (170,000 J/mol) and entropy [49.56 J/(mol·K)]

A dense composite material in the ZrB2–Si system (1400°C, air atmosphere) was obtained. The structure, phase composition, and basic physical properties (density, porosity, elastic modulus, critical stress intensity factor, Vickers hardness) of heat-resistant materials were studied.

A ceramic copper-alumina-silica catalyst (CAS-C) for dehydrogenation of cyclohexanol to cyclohexanone in the process of carbamide production was used to study the rheological and mechanical properties of the copper-containing alumina-silica plastic material depending on its composition. The provided data characterize the effect of the process and design conditions of molding the material in a screw

Results of theoretical and practical studies of the formation of functional ceramic coatings by a method of microspark oxidation in an electrolyte based on boric acid are presented. Good chemical stability of an oxide film in the borate electrolyte is noted, It is shown that treatment of an aluminum surface for 2.5 h at a current density of 5 A/dm2 leads to formation of a ceramic coating with porosity

Monoclinic zirconium dioxide compositions of formula ZrO2–Al2TiO5 containing 0, 2, and 3.5% Al2TiO5 are studied. The aim of the research is to study the effect of aluminum titanate additives on the parameters of the monoclinic zirconium dioxide crystal lattice and sintering of the resulting product. The formation of a solid solution of aluminum titanate in monoclinic zirconium dioxide is confirmed

We describe a basic framework for computer-aided engineering of polished ceramic surface layers. This framework is based on two computational models, a mathematical model, and various algorithms for steady-state and non-steady-state thermoelasticity, an automated thermal stability calculation system and methodology for calculating horizontal and vertical motion, temperature, stress, and stress intensity

Chemical and phase transformations in aWaelz process-slag – carbon system in the range 1700 – 2100 K at a pressure of 0.1 MPa are modeled. It is established that the maximum degree of iron transferred into condensed Fe3 Si is from 34.7 % at 1800 K to 99.9 % at 2100 K, and into Fe5Si3 from 47.7% at 1900 K to 45.6% at 2000 K. With a further increase in temperature iron starts to be transferred into the

The mineral and chemical compositions of the chromite raw materials of the Karelia-Kola region are studied, and physical and chemical processes for producing refractory materials from chromite concentrate are established. The phases and structure formed during drying, firing, and service are determined. The dependence of some refractory properties on their material, grain, and phase compositions is

Compact ceramic electrode materials based on the Ti–B–Fe system modified with nanosize particles of aluminum nitride (up to 15 wt.%) are prepared by SHS extrusion. The effect of additives on combustion characteristics of the system and also on structure and phase composition of the materials obtained is studied. Addition of aluminum nitride increases the content of boride and nitride phases in the

A method for assessing the structure parameters of porous ceramic materials by porosity and particle size is presented. Based on it, a physically more rigorous than the well-known Cozeny formula is obtained, a formula for determining the average (hydraulic) radius of the capillaries of permeable materials. The presented results of the calculation of the average radius of the capillaries of porous ceramics

Research has been conducted on the use of fly ash from TPP in masses based on a fireclay filler and a clay binder for the production of ceramic aluminosilicate materials for various purposes. It was found that the properties of ceramic materials depend on the clay binder:ash ratio. The regions with higher concentrations of ash in the charge and the firing temperature of samples that establish the properties

The results of analytical determination of the effect of nanotechnogenic waste – spent catalyst, on acid resistance, strength and heat resistance of acid-resistant tiles showed three main areas of structural adjustment of the material: increasing growth rate of indicators, a constant growth rate and a site with a sharply negative growth dynamics. Structural changes that improve the studied indicators

This study investigates the destruction of heat-resistant chamotte concrete of various classes: low-cement and medium-cement after exposure to thermal shocks. The influences of the addition of quartz sand (to increase alkaline resistance) and the addition of metal fiber (to reduce cracking) were also studied. Two methods were used to determine the heat resistance of concrete, according to the material

Periclase-chromite refractories are studied after operation under action of acid slags. The refractory microstructure and corrosion mechanism in fayalite melts are demonstrated. Ways of improving refractory stability are proposed.

A bucket belt conveyor with increased traction ability is proposed at the request of Kostanay Minerals JSC. A geometric diagram of the conveyor circuit for the cyclical-flow technology with the transportation of rock mass by steeply inclined conveyors in the contours of the quarry of the first stage of the Dzhetygara chrysotile deposit is given. The calculation of the geometric dimensions of individual

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.