Steklo i Keramika (Glass and Ceramics). Monthly scientific, technical and industrial journal

 

ISSN 0131-9582 (Online)

VOL 96, No. 2 (2023)

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  • FEMTOSECOND-LASER WELDING OF PHOSPHATE GLASS AND ZING–MAGNESIUM–ALUMINOSILICATE GLASS-CERAMICS

    • Pages: 3-8
    • Views: 144
    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.
  • SINTERING CHARACTERISTICS AND THERMAL PROPERTIES OF POROUS CERAMICS BASED ON HYDROPHLOGOPITE AND REFRACTORY CLAYS

    • Pages: 9-18
    • Views: 176
    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.
  • FEATURES IN MICROSTRUCTURE AND THERMOELECTRIC PROPERTIES OF TWO-PHASED CERAMIC MATERIAL BASED ON HIGH-ENTROPY Bi–Sb–Te–Se–S SYSTEMS

    • Pages: 19-26
    • Views: 130
    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.
  • INVESTIGATION OF THE LANTHANUM HEXABORIDE OBTAINING PROCESSES BY THE METHOD OF BOROTHERMAL REDUCTION

    • Pages: 27-41
    • Views: 133
    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.
  • GLAUCONITIC SANDSTONES OF THE CHANGI DEPOSIT ARE A PROMISING RAW MATERIAL FOR OBTAINING GREEN AND BROWN PIGMENT

    • Pages: 42-47
    • Views: 146
    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.
  • COLLOID-CHEMICAL PROPERTIES OF KAOLIN ZHURAVLINY LOG SUSPENSIONS

    • Pages: 48-52
    • Views: 125
    Dispersion characteristics of the Zhuravliny Log kaolin, zeta potential, and apparent viscosity of its suspensions were studied. Kaolin suspensions had rather high stability due to the negative charge of particle surface. Zeta potential was described
    as a function of pH and tripolyphosphate concentration by the electrophoresis. The additive influenced the apparent viscosity of suspensions for account of pH and zeta potential increase ability. Kaolin isoelectric point was found (3.28). Kaolin suspension had a sufficiently high casting rate that might be explained by a good mineral crystallinity (Hinkley index 1.76).
  • ROAD-PURPOSE CERAMIC BRICK FOR PAVING PAVEMENTS IN THE ARAL REGIONS

    • Pages: 53-60
    • Views: 118
    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.