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The chemical and mineralogical compositions, physical and chemical characteristics and phase transformations of diabase rocks of the Uzunbulak deposit were studied. It has been shown that as a result of firing at a temperature of 1000 ?C, phase transformations occur in diabase samples, accompanied by the new formation of the minerals wollastonite, pyroxene and a small amount of high-temperature forms of quartz and cristobalite. The possibility of using this diabase rock as a raw material for producing acid-resistant materials for various purposes has been established.
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This paper presents the results of annealing synthetic quartz glass of high purity at a temperature of 250 ?C and an elevated pressure of 7 MPa in an atmosphere of molecular hydrogen. Annealing under these conditions makes it possible to increase the transmission coefficient at a wavelength of 190 nm by 2 %. The absorption of quartz glass in the range from 238 to 254 nm corresponds to defects in the structural grid of quartz glass, namely, transitions of silicon oxygen-deficient centers of the non-bridge oxygen type, which are deactivated by atomic hydrogen to form stable Si–O–H hydroxyl groups, which in turn reduces absorption in the range from 238 to 254 nm. Using IR Fourier spectroscopy, it was found that the diffusion of molecular hydrogen produces a peak in the wavenumber range from 4200 to 4100 cm–1 and corresponds to molecular hydrogen dissolved in the structural grid of quartz glass.
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The surfaces of lead-silicate glasses and non-etched blanks of microchannel plates after their mechanical processing are studied. It was found that exposure of the obtained samples in a 33 % H2O2 solution led to an increase in optical transparency with a corresponding decrease in their mass. The results obtained are explained by the removal of organic and organosilicon layers from the surface that arose during mechanical processing.
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This study demonstrates the functional advantages of reaction-sintered diamond-silicon carbide (D–SiC) ceramics for armor applications compared to conventional materials including silicon carbide, boron carbide, and alumina. The ballistic performance of reaction-sintered D–SiC ceramics was experimentally evaluated according to protection class Br4 using prototype armor panels with varying ceramic plate thicknesses (6…10 mm) mounted on ultra-high-molecular-weight polyethylene (UHMWPE) flexible backing (8…10 mm). Ballistic tests confirmed complete resistance to penetration in all tested panel configurations.
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Porous ceramic materials, including those with the addition of ?-Al2O3 of the order of 10 %, were obtained on the basis of yttrium oxide, which is inert to sintering and has cubic syngony. The characteristics of the porous structure and filtration properties of synthesized ceramics are revealed. The materials have also been tested under aggressive media (aqueous solutions of H2SO4 acid (20 wt. %) and KOH alkali (10 wt. %) and thermal cycling loads. The results of the studies have shown that the obtained materials are not subject to deformation and destruction in aggressive media. Thermal cycling tests have not revealed any degradation of the physical and mechanical characteristics of the samples. Experimental studies of the separation of solid and liquid components of suspensions on porous ceramic membranes have established the efficiency of rejection of model SiC particles with a size of D50 = 500 nm to be more than 99.9 %. The achieved performance characteristics in combination with the developed pore space of the synthesized materials allow their effective use for micro- and ultrafiltration of liquids, and catalysis processes under aggressive environments and high thermal loads.
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Presents the results of the synthesis of mullite-silica ceramics with improved electrophysical characteristics based on natural kaolinite raw materials extracted in the Orenburg region. The main attention is paid to the study of the effect of heat treatment and the degree of dispersion of the starting material on the formation of the phase composition. Methods of differential thermal analysis, modeling of thermal processes during firing, as well as X-ray phase analysis for phase identification were used for the analysis. It is shown that the choice of the optimal temperature regime and preliminary mechanical (grinding) and chemical (oxalic acid) activation make it possible to stabilize the mullite phase and reduce the maturation of residual silica. This ensures low dielectric losses in a wide frequency range, as well as increased heat resistance and thermal insulation properties of the material. The obtained samples not only meet, but also exceed the requirements of GOST 20419–83 in key parameters such as thermal conductivity and dielectric losses, which confirms their promise for use in electrical insulation structures and thermal barriers in the energy and mechanical engineering.
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The possibility of using waste from the enrichment of ferruginous quartzites of KMA and waste from vanadium production for the plasma synthesis of marblite and structural elements of a plasma glass furnace is considered. The operational parameters of marblite, such as water resistance, frost resistance, microhardness, and phase composition, have been studied. The color characteristics of marblite are determined in the CIE L*a*b* system.
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The article presents the results of a study on the development of a composition of technical ceramics for ceramic grinding bodies and the influence of dispersed oxide on its basic properties. It is shown that waste from a gas processing industry catalyst was used as an alumina-containing component. Dispersed aluminum oxide was obtained from chemical reagents by the citrate sol-gel method. It has been established that the introduction of nanodispersed aluminum oxide in an amount of 3 wt. % over 100 wt. % of the total mass improves the abrasion coefficient, acid resistance, density, and strength of the developed samples of technical ceramics.
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The article presents the results of a study devoted to the development of a laser-induced breakdown spectroscopy (LIBS) method for monitoring the homogeneity of the chemical composition of optical glasses. A quantitative method for studying lead distribution over the surface area of samples in lead-silicate glasses based on LIBS has been developed. The parameters of laser radiation action on the surface of lead-silicate glasses (pulse energy, laser pulse repetition rate, laser wavelength, delay between the pulse and registration of the analytical signal) have been optimized. The minimum step of scanning the chemical composition over the surface area of the sample has been set at 300 ?m.
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Composite ceramic materials based on SiO2–Al2O3–ZrO2 nanopowders were obtained by sintering and their properties were studied. Before sintering, the powders were subjected to mechanical activation in a planetary ball mill using zirconium dioxide balls as grinding bodies. The activated powders were pressed under pressing pressures of 50, 100, 200 and 300 MPa. Consolidation was carried out in an atmospheric high-temperature furnace at 1700 ?. The surface of the sintered bulk samples was examined using a scanning electron microscope. Elemental analysis made it possible to establish patterns in the distribution of chemical elements. It was found that in all the studied samples two phases were formed – Al6Si2O13 and ZrSiO4. The porosity of the samples was determined and the dependence of this parameter on the applied pressing pressure was established. The mechanical properties of the samples were studied using nanoindentation: indentation hardness and elastic modulus, and the bending strength limits of the studied samples were determined during Scratch testing. The crack resistance of the samples was determined by the indentation method using the Marshall-Evans relationship. The effect of the ratio of the initial components and the applied pressing pressure on the physical and mechanical properties of the resulting composite ceramics was determined.
