Today, in the field of construction, the volume of use of ceramic paving stones is growing from year to year to improve the resistance to environmental influences and the decorative properties of road surfaces of modern buildings and structures. Along with this, it is important to obtain ceramic pavers based on compositions consisting of mineral and technogenic raw materials that prevent premature wear under the influence of a salty environment in regions with high salinity. All over the world, intensive scientific research is being carried out to develop the production of ceramic paving stones and other related building materials for regions with high humidity and salinity. In research, special attention is paid to improving the process of firing ceramic mass, introducing modifying additives into the composition, developing technologies for obtaining new materials with crystalline structures and the formation of their properties.
The formation of stable connection between materials with different CTE via using femtosecond laser writing is demonstrated. The welding of phosphate glass (CTE = 120?10–7 K–7) to zinc-magnesium-alumosilicate glass-ceramics (CTE = 62?10–7 K–7) is realised. Investigation of the structural features of laser-induced welds by means of optical microscopy and Raman spectroscopy enables optimization of the laser welding process.
The results of research on the development of compositions of ceramic masses for obtaining effective heat-insulating materials and products are presented. The materials were obtained by pressing using kaolin clays, which differ both in plasticity and in fire resistance. To create a porous structure of the material, a method was used to introduce a porous filler in the form of swollen hydromica developed according to the ferruginous hydrophlogopite type in an amount of 50 wt. %. The apparent density and mechanical strength were studied depending on the pressing pressure, shrinkage during firing. The use of expanded hydromica made it possible to obtain products with a density of up to 1000 kg/m3 while maintaining thermomechanical properties up to 1050 ?C.
The aim of present work is to prepare by using the method of reactive spark plasma sintering, a ceramic material based on the high-entropy Bi–Sb-Te–Se–S system, the nominal composition of which corresponds to the BiSbTeSeS compound (all the atoms are taken in an equiatomic ratio), and to analyze the features in the microstructure and thermoelectric properties of this material. During reactive spark plasma sintering of starting Bi, Sb, Se, Te, and S powders, hexagonal and orthorhombic phases are formed in the bulk material. The hexagonal phase, which corresponds to the high-entropy compound Bi1.5Sb0.5Te1.25Se1.25S0.5, forms a continuous connected “net”. The orthorhombic phase, which corresponds to the wide-gap Sb3S2 semiconductor, fills the hollows in the net isolated from each other. The thermoelectric properties of the material being developed, which are mailnly due to the properties of the high-entropy phase, are promising enough (the maximum value of the thermoelectric figure of merit reaches ~ 0.18). Therefore, this material should be considered as a new prospect high-entropy thermoelectric.
Obtaining new ceramic and composite materials is associated with a number of difficulties, the key of which is the lack of pure initial refractory components. The presence of impurities in the powders available on the market (such as oxygen, iron, carbon, etc.) has a negative impact on the performance characteristics of the resulting materials and products from them. The paper presents the results of experimental studies on the lanthanum hexaboride powder synthesis by boron thermal reduction of lanthanum oxide in a vacuum furnace and a spark plasma sintering unit. The analysis of the obtained results showed that when the content of excess boron in the mixture is 20 wt. % by heat treatment in a vacuum furnace, a single-phase powder of lanthanum hexaboride was obtained at temperatures of 1800 – 1900 ?C. The use of the spark plasma sintering method, however, makes it possible to reduce the temperature of synthesis of a single-phase powder of lanthanum hexaboride to 1700 and 1600 ?C with an excess boron content in the charge of 10 and 20 wt. %, respectively. It is also shown that these powders are characterized by a more uniform cubic structure of lanthanum hexaboride, reflecting its crystalline structure, due to the suppression of the grain recrystallization process by reducing the temperature and time of the technological process.
The results of the research are given: the physicochemical properties of glauconite sandstones of the Changi deposit, the fractional composition, enrichment methods are determined, thermal activation is performed. The coloring properties, coverness, oil capacity of the resulting brown pigment were studied. It has been established that this glauconite sandstone can be used as a raw material for the production of coloring pigments in the construction industry and the manufacture of ceramic materials at the enterprises of Uzbekistan.
The chemical-mineralogical compositions, new formations of crystalline phases of minerals and the main properties of the ceramic mass were studied using iron-containing dust from the gas cleaning of steel-smelting furnaces of metallurgical production during sintering in the temperature range of 950 – 1100 ?C. It has been established that with the introduction of gas cleaning dust, the structure is stabilized and the sintering temperature of the ceramic shard is reduced.
The article provides a brief historical outline of the activities of the Technology of Silicates and Nanomaterials Department of the National Research Tomsk Polytechnic University which is the first technical university in the Asian part of Russia. Initially, the Laboratory of Chemical Technology of Mineral Substances, since 1929 the Silicate Technology Department, since 2007 the Technology of Silicates and Nanomaterials Department, nowdays it is one of the leading scientific and educational centers of the country for the study of silicate raw materials, the development of advanced technologies for ceramics, binders and glass materials, and the training of engineers and scientists specializing in the relevant fields. Research areas of the team embrases now the development of materials and technologies for nanostructured technical and building ceramics with enhanced functional properties, foam glass-ceramic materials, proppants for oil and gas production, biomedical ceramics, magnesian binders with increased strength and water resistance.
The effect of femtosecond laser micro-treatment in thermal and non-thermal modes on the structure of transparent glass-ceramic based on the ZnO–MgO–Al2O3–SiO2 system, characterized by increased mechanical strength and hardness, is investigated. The amorphization of nanoscale ganite (ZnAl2O4) crystals, which occurs under the irradiation of laser pulses, is confirmed by the results of electron microscopy and electron diffraction. Quantitative phase microscopy was used to evaluate changes in the refractive index in individual tracks written by a laser beam. At the repetition frequency of 10 kHz in non-thermal mode, complete amorphization of the crystal phases in volume glass-ceramic sample leads to an increase of the refractive index by the value ?n = 0.0007 in the laser processing area. The results obtained expand the potential applications of transparent glass-ceramics with increased mechanical properties and open up the possibility of forming channel waveguides in their volume by direct laserwriting.
