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The phase composition of the powder synthesized from aqueous solutions of sodium silicate Na2SiO3 and iron sulfate FeSO4 at the molar ratio Fe/Si = 2 according to X-ray diffraction (XRD) data included hydrated sodium iron sulfate Na2Fe(SO4)2·4H2O and X-ray amorphous product with the composition represented by hydrated iron and silicon oxides. The phase composition of the powder obtained by 4-times washing of the synthesized powder in distilled water included only an X-ray amorphous product.
After firing in air in the range of 400…1200 ?C, hematite Fe2O3 and cristobalite SiO2 were found in powder samples and ceramics based on these powders. After firing at 900 ?C under graphite powder the phase composition of ceramic samples included magnetite Fe3O4, laihunite Fe4,74(SiO4)3 and fyalite Fe2SiO4. The powder prepared from the product isolated from the mother liquor included hydrated sodium iron sulfate Na2Fe(SO4)2·4H2O and sodium iron sulfate hydroxide hydrate (metasideronatrite) Na4Fe2(SO4)4(OH)2·3H2O. After heat treatment at 400 ?C, sodium iron sulfate Na3Fe(SO4)3 was the predominant phase in this powder. Powders obtained as a result of the interaction of aqueous solutions of sodium silicate and iron sulfate can be used to manufacture of high-temperature dyes and materials with magnetic properties; to create analogues of lunar or Martian regolith; and also, be of interest for research related to the development of functional (cathode) materials for Na-ion batteries.
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Currently, the use of ceramic shells for casting metal melts is quite widespread in almost most machine-building enterprises. The main method of production of ceramic molds is the method of forming them on smelted or burnt models with subsequent removal of the model material. The formation of ceramics from a ceramic suspension by a gradual build-up method requires the use of binders with a number of physico-chemical properties that ensure the quality of the prepared shells. Any binder prepared on a water basis has a rather complex composition, including several organic compounds, which causes problems of their compatibility, as well as their performance for a long time (up to a year) under conditions
of continuous mixing of sedimentation-unstable ceramic suspension, and when the composition changes due to uneven removal of components during operation. Obviously, the development of a workable binder necessarily requires in-depth study of the physico-chemical properties of the components and their combined aqueous solutions, which allows optimizing the selection of components and their concentration in binders.
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A review of oxide compositions, developed for ceramic aluminosilicate fibers -based filter elements modification for the purpose of the selective catalytic reduction of nitrogen oxides in the purification of high-temperature industrial gases, is presented. Methods for preparing the catalytic compositions and methods for their introduction into the structure of the ceramic filter elements are presented.
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The adhesive strength of the solid phase boundary in the Ge20Se80 glass–substrate (quartz glass, stainless steel, tungsten carbide) systems in the temperature range of 270…360 ?C was measured using the pull-off test for adhesion.
The maximum adhesion of chalcogenide glass among the studied structural materials is observed to stainless steel with a non-nitrided surface. The wetting and adhesion of the Ge20Se80 glass melt to structural materials in the temperature range of 370…470 ?C have been investigated. The maximum adhesion of the chalcogenide melt is observed to the surface of quartz glass, the minimum is to the surface of nitrided stainless steel.
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In this study, the influence of the quantitative content of sulfate ions at key technological stages of the synthesis of YAG:Cr ceramic powder on the optical properties of ceramics was investigated. The size and size distribution of particles, the degree of agglomeration, specific surface area, and phase composition of the ceramic powder were evaluated.
The changes in the microstructure and optical properties of the YAG:Cr ceramic material were described depending on the amount of sulfate ions used at various stages of the synthesis of ceramic powder.
It was found that the use of a solution containing 0.200 M and 0.045 M sulfate ions at the stage of precipitation or washing of the precipitate, respectively, resulted in achieving better dispersal characteristics and the highest monodispersity of precursor powders and YAG:Cr ceramic powders. Additionally, it improved the optical properties of YAG:Cr ceramics with a light transmittance value of over 81.5 %.
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The results of a study of the dielectric properties and harmonic coefficient for barium titanate ceramics obtained from
a powder with a particle size of 50 nm at different sintering temperatures are presented. It is shown that ceramics from nanopowders can be produced at lower sintering temperatures than technical ceramics with a particle size of 1 µm. Ceramics obtained at a sintering temperature of 1200 ?C have the best linear and nonlinear dielectric properties.
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Thermal insulation and composite foamed inorganic materials with a reduced thermal conductivity of 0,064…0,076 W/(m·K) have been developed on the basis of technogenic silica-containing raw materials. The influence of pore-forming and curing modifying additives on the structure, phase formation and physico-technical properties of foamed materials has been studied. It was found that the combined use of graphite and chalk leads to a decrease in the density of materials, the use of graphite and gypsum, graphite and sodium silicofluoride leads to an increase in the strength of materials.
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The article investigates the physical, mechanical and technological properties of ceramic plates in the composition of Kulatau clay and dune sands of the Tuprakkala massif located in the lower amudarya region of the Uzbekistan. Under the conditions of laboratory and semi-production tests, it was found that, from the optimal composition M-7 at a firing temperature of 1000…1050 ?C, it is possible to obtain unglazed facade tiles and floor tiles. And from the optimal composition M-9 at firing temperatures of 1000…1050 ?C, it is possible to obtain facing and facade tiles with opaque glaze.
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The effectiveness of using borate (borax) and fluoride (sodium fluoride) fluxes in the sintering of crystalline (sand) and amorphous (diatomite) silicate raw materials was considered. The change in the density and appearance of samples
with varying degrees of fluxes during their heat treatment at different temperatures was described. It was shown that
the introduction of 4 wt. % borax reduces the temperature to reach a density of 1500 kg/m3 by 100 °C, and 6 wt. % borax – by 200 °C. It was shown that the introduction of fluxes increases the amount of X-ray amorphous glass phase due
to depolymerization of the silicon-oxygen network and the formation of a low-temperature melt.
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An overview of dielectric materials with high (more than 10 000) values of relative permittivity is presented. Most of the compositions of these materials are based on systems that include ferroelectric and non-ferroelectric components,
as well as solid solutions based on them. Various approaches to increasing the dielectric permittivity of materials are considered: doping, sintering atmosphere, grinding time, sintering temperature, grain size. The effect of dopants and the synthesis method on the value of characteristics of capacitor ceramics that can be used in the low-frequency and high-frequency range is compared.
