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


ISSN 0131-9582 (Online)

A statistical analysis of the relationship of the redox ratio of the produced float glass with the technological mode of cooking, the charge content and the chemical composition of the glass was carried out. The influence of the redox ratio on the technical and economic performance of the bath furnace and the quality of the glass produced is shown.
Transparent glass-ceramics are attracting more and more attention as a material for protecting the screens of electronic devices. The paper considers the possibility of carrying out ion-exchange of transparent gahnite glass-ceramics containing a small Na2O content. The structure and properties of glass-ceramics before and after ion-exchange were studied by x-ray diffraction analysis, transmission electron microscopy, Raman spectroscopy, laser-induced breakdown spectroscopy, and Vickers hardness determination. It is shown that, under certain conditions, ion-strengthening of glass ceramics with a low content of alkali ions can lead to an increase in microhardness values.
Ceramics Ce0.9Bi0.1O2 – ? was obtained by solid-phase synthesis. It is shown that the obtained samples have a cubic fluorite structure with the space symmetry group Fm3m. The electrical properties of the Ce0.9Bi0.1O2 – ? solid solution were studied by ac impedance spectrometry. It has been established that the activation energy of electrical conductivity has two sections 0.51 eV (400 – 680 ?С) and 1.6 eV (680 – 800 ?С), the activation energy of the dielectric relaxation process was 0.88 eV.
Lead-containing perovskite of complex composition PbNaKNb2FeO9.5 (sp. gr. Pnma, a = 5.654 ± 0.003 ?, b = 7.977 ± 0.001 ?, c = 5.646 ± 0.003 ?) was synthesized for the first time by the solid-phase reaction method. The sample is characterized by a non-porous microstructure formed by randomly oriented cubic crystallites. The band gap (?2.10 eV) of a complex perovskite for a direct allowed electronic transition was calculated from the data of the diffuse reflectance spectrum. The permittivity of the sample at room temperature and a frequency of 106 Hz reaches 1365, and the dielectric loss tangent is 0.1.
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).
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.