Кераміка: наука і життя

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ISSN / EISSN : 25216694 / 25216708
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O.Ur. Bilousov, V.A. Sviderskyy, O.V. Myronuk
Кераміка: наука і життя pp 15-20; doi:10.26909/csl.2.2020.2

Abstract:
The results of research of porous materials on the basis of products of ceramic production - chamot as a fractionating filler are given.. The features of formation of structure of material at the use of chamot with different chemical and mineralogical compositions in the conditions of speed baking are shown. Porous ceramics for filtration and aeration is obtained by a technology based on the regulation of porosity parameters by the use of chamotte of a certain granulometric composition and special binders. However, the granulometric composition of chamotte is a necessary but not sufficient factor to optimize the properties of porous filter ceramics. Along with the granulometry of chamotte, its chemical and mineralogical composition and surface energy must be taken into account. It depends in turn on the technological properties and the firing parameters of the original clay raw material. This paper presents the results of a study of porous materials based on ceramic products - chamotte as a fractionated filler. The chemical and mineralogical composition of chamotte made of poly-mineral clay at maximum firing temperature of 950°С and of refractory clay at firing at 1320°C was analyzed. The energy state of the surface of the chamotte particles was determined with the wetting by polar and non-polar liquids (water and benzene respectively). The differences in the specific effective surface area, lyophilicity and filtration coefficients was determined. The peculiarities of the formation of the pore structure of ceramics obtained using the specified samples of chamotte in the conditions of high-speed firing in the roller oven are shown. Significant differences in the formation of open and closed pores were observed, the predominant specific proportion of open pores in the material using polymineral clay. The possibility of properties regulation of the pore structure and the energy state of the surface of the filter material when applying a mixture of chamotte varieties was experimentally confirmed.
S.A. Knyazev
Кераміка: наука і життя pp 26-30; doi:10.26909/csl.2.2020.4

Abstract:
The results of obtaining borated layers on 15H11MF high-alloy steel under equilibrium and non-equilibrium heating conditions are presented. Equilibrium conditions were achieved by slow furnace heating (with a heating rate of 0.1 oC/s), non-equilibrium – by induction heating (with a heating rate of 100 oC/s). The heating was controlled by measuring the thermoelectric power by a thermocouple welded to the surface of the sample by electric contact welding. The signal from the thermocouple was digitized by the ADC and transmitted to a computer where, at high speed, an array of data of temperature-time dependence of the process was formed. Furnace heating was carried out in a laboratory electric furnace at 1130 оС ± 5 оС, 1150 оС ± 5 оС and 1160 оС ± 5 оС. Induction heating was carried out to temperatures of 1180 oC ± 20oC, 1200 oC ± 20oC, 1220 oC ± 20oC. The possibility of significant reduction of the treatment process from 3 hours to 2 minutes due to the intensifying action in non-equilibrium conditions of structure formation is shown. Boron saturation came from the paste. Saturating paste consisted of 60% boron carbide, 30% NaF, 10% CaF2. The method of metallographic research shows not only the morphological differences of the obtained surface layers, but also established the predominant mechanism of boron diffusion into high-alloy martensitic steel. During furnace heating (1150оС), a solid boron with a thickness of up to 50 μm and a hardness of 15100 MPa is formed. At a depth of up to 150 μm, grain boundary diffusion is noticeable, which obviously dominates in the processes of boron saturation of high-alloy steels. At temperatures of 1160 oC and furnace heating under a solid layer of boride with a thickness of 110 μm, a two-phase zone is formed, which consists of boride and a solid solution with a thickness of 70 μm. This layer is more defective. Induction heating with boron saturation forms a thick (up to 200 μm) layer of coarse boride crystallites (18900 – 9270 MPa) with an eutectic structure (6440 MPa), which becomes coarser with increasing temperature from 1180 to 1220 оС. The ability to obtain solid hardened layers in a short treatment time makes boron saturation from pastes a more attractive alternative among other chemical-heat treatment technologies.
L.P. Chernyak, A. Soroka
Кераміка: наука і життя pp 21-25; doi:10.26909/csl.2.2020.3

Abstract:
The possibility of making of mineral astringent material of the low temperature «Mineral» computer program to determine the quantitative content of rock-forming minerals of silicate raw materials as factor in structure formation in technological processes of production and to achieve the specified properties of materials and products are shown. The results of calculations of the mineralogical composition of carbonate and clay raw materials are presented. Varieties of raw materials used in the chemical technology of silicates are a set of certain rock-forming minerals of known chemical composition. Determination of the quantitative content of rock-forming minerals of raw materials is possible by calculations based on the initial data of chemical and qualitative mineralogical compositions. The creation of a mathematical apparatus for processing the results of research and computer technology has increased the efficiency and efficiency of determining the quantitative content of rock-forming minerals. However, the constant increase in the number of varieties of potential raw materials makes it appropriate to improve the method of determining the quantitative mineralogical composition using computer calculations and modern software, in the direction of which the work is performed. Determining the quantitative mineralogical composition of raw materials using the computer program "Mineral" is appropriate to optimize the charge composition of masses and technological parameters of silicate production, including ceramics, glass and binders. The created program "Mineral" should be used by specialists of the building materials industry, production, research and design organizations working in the field of chemical technology of silicates, teachers and students of higher educational institutions.
V.V. Tsygoda, V.Ya. Petrovskiy
Кераміка: наука і життя pp 7-14; doi:10.26909/csl.2.2020.1

Abstract:
The possibility of reducing the thermal conductivity of silicon nitride as a basis of high-temperature electrical converters was investigated in the thesis. Also, the values of thermoelectric figure of merit and efficiency of thermoelectric current generator for the case of refractory oxygen-free composites were simulated. During the study, the dependence between the m coefficient, which determines the maximum possible efficiency of the thermoelectric generator and the ZT thermoelectric figure of merit, was determined. It was shown that the coefficient of thermal conductivity of the studied materials ranges from 1,2 to 4·106 m2/s and is characterized by a negative temperature coefficient over the entire temperature range. It was found that the thermal conductivity of Si3N4-based materials varies from 2,1 to 5,1 W/(m·K) depending on the type of sintering activator. The use of Al2O3 as an activator makes it possible to obtain a 25% lower thermal conductivity value comparing to materials with the addition of MgO. For the first time, it was proved that currently it is not possible to achieve an efficiency of 0,5hT in Si3N4-based materials used as a composite basis for high-temperature thermoelectric generators development.
Olean Fesenko, V. V. Korskanov, Volodimir Dolgoshey, E.S. Kifuk, P.P. Pogoreckiy
Кераміка: наука і життя pp 24-28; doi:10.26909/csl.1.2020.4

Abstract:
The purpose of this work was to study the specific thermal conductivity of aqueous graphene dispersions and the diluted aqueous solution of nanostructures based on graphene and Au nanoparticles, as well as to determine the temperature and concentration dependences of the specific thermal conductivity of these aqueous dispersions. The objects of study were aqueous dispersions of graphene and nanostructures based on graphene and Au nanoparticles. Graphene has characteristic dimensions of the order of 150 - 200 nm in the plane. The Au nanoparticles also have an average size of about 50 nm and a star-like shape. In dry nanocomposites, graphene is oriented parallel to the substrate plane, and nanostars are evenly distributed on the sample surface. The specific volumetric thermal conductivity values of aqueous graphene dispersions and aqueous solutions of graphene-based nanoparticles and Au nanoparticles were obtained in the temperature range from 30оC to 60оC. A slight increase in the specific thermal conductivity was found with increasing temperature. The absolute values a/v of aqueous graphene dispersions are 1.6 times higher than in three-component systems. The concentration dependences of the thermal conductivity of the two systems studied are linear. It is determined that the values of the specific thermal conductivity of dry graphene nanofillers are 1,62 times higher than the thermal conductivity of a mixture of graphene and Au nanoparticles.
Ye.Ya. Telnikov, O.G. Chernyshyn
Кераміка: наука і життя pp 13-17; doi:10.26909/csl.1.2020.2

Abstract:
The article deals with the technical parameters of thick-film heating elements, the peculiarities of their operation, as well as the scope of use in household and industrial heat-generating electrical devices. The world is constantly researching the possibility of developing heating elements without the aforementioned disadvantages of tube thermal elements, which allow more efficient use of consumed electricity, which leads to significant savings. A new type of heat to heat converter is proposed in this direction. The use of this converter - the heating element - in various industrial and household products can save up to 30% of electricity consumption. At the heart of the design of the heating element is a developed system of different properties of composite nanostructured materials - pastes. On the basis of this system of materials the technology of production of new heating elements with unique properties was created. The heating element is made by screen printing (silk screening) of special composite materials on a dielectric or metal substrate with their subsequent heat treatment. Dielectric, resistive, dielectric layers are sequentially applied to a flat substrate of any configuration, but can also be applied to cylindrical surfaces. Purposeful formation of a conductive structure in the resistive layers of thick-film heating elements and the ability to influence the properties of the nanoscale layer between the particles of the conductive phase allowed to create a group of materials, and on their basis, a series of heating elements with the properties of the technical intellect, environment. The technology for production of heating elements with self-regulation of parameters for wide values of supply voltage, thermal power, and specific heat dissipation power (surface heat flux density) has been developed. One of the significant advantages of the technology is the absence in the resistive paste of expensive and scarce precious metals and their compounds, which are part of similar pastes, offered by leading manufacturers in the world. Due to this, the cost of manufacturing such pastes is substantially lower than that of the world.
Lyudmyla Shchukina, S.L. Lihezin, Mykhailo Ryshchenko
Кераміка: наука і життя pp 18-23; doi:10.26909/csl.1.2020.3

Abstract:
The efficiency of using different oxidizing agents to intensify the burnout of the organic component of ceramic masses is investigated. The ceramic masses contained coal flotation wastes with a high carbon content as a fuel-mineral additive. Various inorganic salts, which are oxygen donors during the firing of ceramic masses and form oxidizing agents O2, NO2, N2O during their thermal decomposition, are considered. A new calculation method for determining the content of an oxidizing salt in a ceramic mixture is proposed. This method takes as a basis the amount of «effective oxygen» that released during the thermal decomposition of the oxidizing agent, but not its mass, as it was before. The method allows calculating the rational content of an oxidizing agent necessary for efficient combustion of the carbon component of fuel-mineral additives. When calculating, it is necessary to take into the composition of the organic part of the additive, its content in the ceramic mass and the degree of carbon oxidation. Calculation of the rational content of the oxidizing agent according to this method allows avoiding its excessive and economically unreasonable use. The effect of oxidizing agents and their combinations on the burnout of the carbon component and the firing properties of the masses for wall ceramics is studied. The masses contained 15 % of coal flotation waste with a carbon content of 29 %. It was found that the use of oxidizing agents accelerates the burnout of the organic part of the masses, improves the appearance and mechanical properties of ceramic samples. The use of combined oxidizing agents with different decomposition temperatures makes it possible to create an oxidizing medium in a wider temperature range. This positively effects on the mechanical properties of ceramics. The optimal combinations of oxidizing agents NH4NO3+Ca(NO3)2 і NH4NO3+NaNO3, which made it possible to obtain ceramic samples with a compressive strength 10 МПа, were determined. This mechanical strength meets the requirements of the State Standard of Ukraine B M.2.7-61: 2008 in part of ordinary brick of the M100 brand.
V.V. Glukhovskyi
Кераміка: наука і життя pp 7-12; doi:10.26909/csl.1.2020.1

Abstract:
The mechanism of contact-condensation solidification provides the formation of a solid rocky body in the event of contact between the microparticles of a substance of amorphous or unstable crystalline structure without changing its chemical composition as a result of physical surface phenomena. Therefore, to provide stronger contacts between the particles of such binders during their condensation, it is necessary to apply external pressure (compression). The implementation of such binders is not linked to the timing of grieving. The curing process is carried out immediately at the time of contact between the particles of such binders. In the future, the strength of artificial stone increases in natural conditions and in water. The results of studies of the dependence of the pressing parameters on the basic performance of the products based on the binder contact-condensation hardening are presented. It is established that in order to maximize the effective action of pressures, which provide plastic deformation during compaction and provide the most dense packing of powder particles, there is a limit of working pressures in the range from 40 to 150 MPa. It is shown that it is convenient to use mathematical expressions (extrusion equations) when analyzing the processes occurring during extrusion, which reveal a functional relationship between the pressure and the density of the material thus obtained. With the help of the equations of pressing, for each powder or group related to the physicochemical parameters of the powders, the most economical parameters of the pressing modes can be determined. The data obtained for the compression pressure characterizing the action of plastic deformation for the test mixtures is in the pressure range from 32 MPa to 158 MPa. Increasing the pressure above leads to the transition of plastic deformation into elastic deformation, in which the seal passes due to the destruction of particles under the action of high pressures.
V. V. Korskanov, Olean Fesenko, T.V. Tsebrienko, O.P. Budnik, Volodimir Dolgoshey
Кераміка: наука і життя pp 14-20; doi:10.26909/csl.4.2019.2

Abstract:
The objects of study were water dispersions of raw graphene (hereinafter referred to as graphene-n), higher degree of purification of graphene samples (hereinafter graphene), and nanoparticles of graphene-Au nanoparticles based on them. The thermal conductivity of water graphene dispersions and water dispersions of gold graphene nanoparticles nanostructures at different temperatures and component ratios was investigated. The values ​​of effective thermal conductivity of dry nanofillers are calculated. The temperature dependences of the thermal conductivity of the nanofillers were obtained. It is found that the in-thermal conductivity of water dispersions of purified graphene is higher than the thermal conductivity of raw graphene as a result of better packing of nanoparticles in pure graphene nanofillers compared to raw. The effect of enhancement of thermal conductivity of gold nanoparticles, which is accompanied by higher absolute values of thermal conductivity of nanoparticles of graphene-nanoparticles of gold than the corresponding graphene, was revealed. At the same time, there is a significant difference in thermal conductivity between nanoparticles of graphene nanoparticles of gold. It is established that higher values of thermal conductivity of graphene-nanoparticles nanostructures of gold are the result of the reinforcing action of a gold nanoparticle substrate, which is formed as a result of joint sedimentation with graphene during the formation of nano-flakes from water solution during evaporation of water.
V.V. Glukhovskyi
Кераміка: наука і життя pp 26-30; doi:10.26909/csl.4.2019.4

Abstract:
The results of scientific research in realization of energy-intensity cellular concrete production technology of normal condition hardening are shown. Physical-mechanical and thermophysical properties of cellular concretes, which are produced by this technology, are relevant to active normative documents. In this case the produced cellular concretes are characterized with strength increasing in time in compare to autoclave hardening cellular concretes and aerated concrete. The influence of the chemical activity of the fillers on the performance of the final product has been established. According to the results of the performed researches it is established that the activity of the filler determines the kinetics of change in the time of the strength of the composition, which solidifies under normal conditions. When used as ground coal ash filler, the level of strength of porous concrete at the age of 28 days is at the level of strength of the composition with the addition of ground granulated slag (3,22 and 3,38 MPa, respectively). It is also found that, unlike autoclaved aerated concretes, the strength of aerated concretes of normal cement based on Portland cement increases over time both on binder without mineral additives and in the presence of ash, milled slag and quartz sand. The intensity of the process of gaining strength over time is determined by the activity of the mineral additive. When used as a mineral admixture of non-ground quartz sand, which, under normal curing conditions, does not interact with the curing of Portland cement, the strength of the porous concrete decreases with increasing amount of this additive in the composition. The intensity of the strength of these compositions at the age of 90 days, depending on the amount of additive, is 10 - 18%. The proposed technology for the production of cellular concrete based on Portland cement, curing under normal conditions, was implemented in industrial production. D700 concrete was selected as the base for production.
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