VOL 94, No. 12 (2021)

The results of synthesis of lanthanum borate glasses modified with highly polarizable cations (Nb, Ti, Zr, Ta) are described. Their crystallization properties and structural features are studied by IR spectroscopy. It was found, that in the range of compositions 25La2O3–xMnOm–(75 – x)B2O3 (M = Nb, Ta, Ti, Zr, x = 0 – 25 mol %) glass specimens with a refractive index higher than 1,8 can be obtained. It is assumed that in the studied glasses in addition to the borate network a network of M cations corner-sharing of large polyhedra is formed. That preserves ability of the melt to glass formation

The process of crystallization of mullite during the synthesis of a ceramic composite material “mullite – zirconium oxide” obtained from a two-phase gel by a method combining co-deposition and sol-gel synthesis was investigated. Powders of the ceramic composite material “mullite – ZrO2” were obtained, their heat treatment was carried out at 1150 and 1350 °C. Samples of the ceramic composite material “mullite-zirconium oxide” were made from the obtained powders by semi-dry pressing. The microstructure and phase composition of ceramics were studied

The insertion into the impregnating suspension based on hydroxyapatite powder heat-treated at 800 °C, 24 wt. % of monocalcium phosphate monohydrate powder after firing at 1200 °C leads to the formation of calcium phosphate foam ceramic based on ?-tricalcium phosphate and ?-calcium pyrophosphate. Successive application of hydroxyapatite and biomimetic apatite to calcium phosphate foam ceramic leads to an increase in strength and enrichment in a-tricalcium phosphate and hydroxyapatite. Multiphase calcium phosphate foam ceramic has a porosity of 35 - 60 %, a static strength up to 0.08 MPa, and increased bioactivity due to the biomimetic apatite layer

The effect of the anionic composition of zinc salts on the preparation of powders in the ZnO–SnO2 system by the sol-gel method has been investigated. It was determined that the synthesis and microstructure of the obtained powders depend on the activity of the acid forming the zinc salt. According to the data of X-ray phase analysis and scanning electron microscopy, the optimal raw material for obtaining zinc orthostannate is zinc sulfate

This article presents the results of a study of the process of cutting mica using ultrashort pulsed laser radia-tion of the picosecond and femtosecond ranges with a wavelength of 1030 nm. The pulses were focused by a small NA lens (NA < 0.1). Optimization of conditions for achieving large-scale processing without microcracks of submicron dimensions along the edges and walls of the cut is carried out at different pulse duration, pulse energy and scanning speed. Samples with a thickness of 0.1 – 0.2 mm were cut out, the de-sired result was achieved without visible heat-affected zones. It has been found that the use of a real-time sample surface tracking system to adjust the focal position throughout the sheet is essential when processing mica in mass production is required

In the course of the study, the possibility of using ash and slag waste from the thermal power plant of the Arctic zone as raw materials for the production of porous ecogeopolymers was studied. The assessment was carried out according to the established three main criteria: radiation activity, chemical composition of ash and slag, namely, the amount of oxides SiO2, Al2O3, CaO and the modulus of their basicity Mo. The possibility of using ash and slag from the Apatitskaya and Severodvinskaya TPPs of the Arctic zone has been established and the main technological parameters for the synthesis of porous ecogeopolymer materials on their basis have been developed

The method of determining the volume-geometric structure of a corundum slip is refined by additional calculation of the average coordination number, the specific surface of the system S0 (the surface of the unit volume of the slip), and the number of contacts between particles per unit volume of the slip. This will eliminate ambiguity in the presented structural parameters of the slip. The calculated structural parameters of the corundum slip are given

The safe treatment of radionuclide-contaminated soil in uranium tailings is of critical importance. In this work, neodymium- and cerium-contaminated soil in uranium tailings were successfully immobilized via mi-crowave sintering to form glasses with the addition of Na2CO3. The phase evolution and chemical durabil-ity of the as-prepared vitrified forms were systematically investigated using various spectroscopic and microscopic techniques. The results indicated that Nd and Ce could be fixed in glass structures, and the ultimate solid solubility of Nd and Ce reached 15 and 5 wt.%, respectively, with 20 wt.% Na2CO3 added. These samples were sintered at 1200 оС for 40 min, and the solidified samples exhibited homogeneous elemental distribution. Moreover, the sintered matrices exhibited excellent chemical durability. The normalized leaching rates of Ce and Nd after 42 days were maintained at low values (~10–6 – 10–7 gm–2 d–1)

BaTiO3 ceramics are common components of capacitors, sensors, and actuators. Recent research has focused on improving the dielectric properties of BaTiO3 by using Zr ions for B-site substitution. Additional additives can further enhance ceramic performance. In this work, BaZr0.15Ti0.85O3 (BZT) ceramics were prepared by a solid-phase reaction at various contents of added Al ions. All of the ceramic samples had a perovskite cubic phase structure. Compared with BZT ceramics without added Al2O3, the size of the grains increased considerably, and the grain size decreased slightly in accordance with increasing concentration of Al ions. Addition of Al ions considerably increased the density of the ceramics, yet excessive addition of Al ions decreased the density. The dielectric constants were relatively large when the Al ion content was 0.25 and 1.0 mol.%: 9117 and 8725 C2/(Nm2), respectively, at the Curie temperature. Compared with BZT ceramics without Al ions, the dielectric properties were greatly improved, by two different mechanisms (depending on the Al content). In accordance with increasing Al content, the hysteresis loop was narrower, the remanent polarization decreased, and the coercive electric field increased

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