For a multimode optical fiber, whose core is formed by quartz glass of the KU-1 type with a high content of hydroxyl groups, the dynamics of the reversible (recoverable) change in the optical absorption of these groups near 7200 cm–1 when the light guide is heated to 1050°C, are studied. Based on the decomposition of the absorption band into spectral components at different temperatures, assumptions are made regarding the structure of absorption centers related to the OH groups.
The influence of chemical elements in the composition of optical glasses on the quantitative characteristics of their attenuation of X-ray and gamma radiation is analyzed. The method of calculating the mass coefficients of radiation attenuation (MCRA) with quantum energy ranging from 0.2 to 3.0 MeV for oxides as glass components is proposed. The chemical elements and their oxides in the glass composition, which make the main contribution to their values of the linear coefficient of radiation attenuation (LCRA) with different quantum energies, E, are identified. In the field of quantum energies ranging from 0.2 to about 1.0 MeV, oxides such as PbO, Ta2O5, Gd2O3, La2O3, BaO, Sb2O3 (due to its low concentration, its contribution to LCRA is usually negligible), CdO, Nb2O5, ZrO2, and Y2O3 have a strong effect (in decreasing order) on the LCRA values of glasses. It is shown that in the field of E values ranging from 0.2 to about 1.0 MeV, elements (or their oxides) can be very different from each other in terms of their MCRA values, and glasses of different compositions, in terms of their LCRA values, while at E > 1.0 MeV, both the first and second coefficients change approximately equally with an increase in the energy of radiation quanta.
Using computer methods (the ToposPro software package), a combinatorial topological analysis and modeling of the self-assembly of crystal structures of Ce56Ni24Si44-mS124 (a = 34.08 Å, b = 4.245 Å, c = 21.37 Å, β = 113.52(3)°, V = 2835.14 Å3, C12/m1) and Ba10La2Si12-oP48 (a = 17.144 Å, b = 4.876 Å, c = 17.910 Å, V = 1497.46 Å3, Pnma) are carried out. For the crystal structure of Ce56Ni24Si44-mS124, 5511 variants of the cluster representation of the 3D atomic network are established with the number of structural units 5 (28 variants), 6 (943 variants), 7 (2316 variants), 8 (1704), and 9 (520 variants). The variant of the self-assembly of a crystal structure from the packing components of three types of cluster-precursors K13 = 0@13(Ce6CeNi2Si4), K4 = 0@4(Ce2NiSi), and K3 = 0@3(CeNiSi), as well as Si spacer atoms, is considered. For the crystal structure of Ba10La2Si12-oP48, 21 variants of the cluster representation of the 3D atomic network with the number of structural units of 2 and 3 are established. The variant of self-assembly of the crystal structure with the participation of cluster-precursors forming the packing K11 = 0@11(Ba5LaSi5) and Si spacer atoms is considered. The symmetry and topological code of the processes of self-assembly of 3D structures from cluster-precursors is reconstructed in the following form: primary chain → layer → framework.
Using the method of the joint crystallization of solutions of nitrate salts with ultrasonic treatment, xerogels and highly dispersed mesoporous powders of the following composition are synthesized: (CeO2)1 – x(Nd2O3)x (x = 0.02; 0.05; 0.10), Gd1 – xSrxCo0.5O3 – δ (x = 0.1, 0.15, 0.2, 0, 25), Gd0.4Sr0.1Ni0.5O3 – δ, and Gd0.125La0.125Sr0.25Co0.5O3 – δ; and based on them, nanoceramic materials with a crystalline cubic structure of the fluorite type, as well as an orthorhombic and tetragonal structure of the perovskite type with CSR ~ 55–90 nm (1300°С), respectively, are obtained. The physicochemical properties of the resulting ceramics are studied; it is revealed that it has an open porosity of 7–11% for the composition (CeO2)1 – x(Nd2O3)x and 17–42% for materials with the Gd1 – xSrxCo0.5O3 – δ, Gd0.4Sr0.1Ni0.5O3 – δ, and Gd0.125La0.125Sr0.25Co0.5O3 – δ composition. Materials based on cerium oxide predominantly have the ionic (ion transport numbers ti = 0.71–0.89 in the range 300–700°С) type of electrical conductivity due to the formation of mobile oxygen vacancies in the heterovalent substitution of Ce4+ by Nd3+; and σ700°С = 0.31 × 10–2 S/cm Solid solutions based on nickelate and lanthanum cobaltite have mixed electron-ionic conductivity, σ700°С = 0.59 × 10–1 S/cm with transfer numbers te = 0.92–0.99 and ti = 0.08–0.01. The prospects for using the obtained ceramic materials as solid oxide electrolytes and electrodes for medium-temperature fuel cells (FCs) are shown.
A method is developed for producing primary catalyst carriers in the form of honeycomb blocks using additive technologies. The composition of the molding slip is developed and its rheological properties are optimized. Block catalysts based on primary supports formed by 3D printing are obtained. It is shown that these products are highly productive in the process of the catalytic oxidation of CO with atmospheric oxygen and it is possible to further increase it due to the formation of channels of complex geometric shapes, which make it possible to intensify the processes of heat and mass transfer.
Anion-deficient structures based on a Sr0.5Ba0.5Co1 – xFexO3 – δ composition, synthesized from a melt in a solar oven in a flux of concentrated solar radiation with a density of 100–200 W/cm2 are studied. Briquettes in the form of tablets based on a stoichiometric mixture of carbonates and oxides of the corresponding metals (SrCO3 + BaCO3 + Co2O3 + Fe2O3) are melted in the focal zone of the great solar furnace. Melt drops flow into the water, cooling at a rate of 103 deg/s. The castings were ground to a fineness of 63 µm, dried at 400°C, and molded into tablets (samples) with a diameter of 20 mm and a height of 10 mm. Samples of the material are sintered in the temperature range 1050–1250°C. The samples are used to study the structure, water absorption, and destruction in a carbon dioxide environment. The crystal lattice of the material has a perovskite structure with the unit cell parameter a = 4.04 Å. Samples of the material show resistance to water vapor. The observed values of the structural parameters indicate that the material of composition Sr0.5Ba0.5Co0.8Fe0.2O2.78 can be used as a catalyst for the generation of hydrogen and synthesis gas through reforming and methane oxidation.
When low molecular weight ammonium polyphosphate interacts with polyethylene polyamine, thermoplastic polymers containing fractions with glass transition temperatures Tglass ≥ –95°C are obtained. Their thermal and heat resistance, as well as moisture resistance, is measured at a humidity of 40–50%. The structure and chemical scheme for the formation of interaction products are proposed.
In this work we prepared boro-telluride glass samples while varying the concentration of TeO2 (0.00, 10.00, 20.00 mol %) by melt quenching technique and study their physical, optical and luminescence properties by various characterization methods. We found that band gap lies in the 2.88–2.18 eV range, showing decreasing trend with increasing concentration of TeO2. The emission spectra shows four emission peaks under 378 nm excitation centered at 486, 545, 590 and 620 nm because of the transition from 5D4 state to 7FJ (where, J = 6, 5, 4, 3) lower levels. Whereas the intensity decreases with increasing concentration of TeO2, indicating that the non-radiative energy transfer through cross relaxation (CR) increases with increasing concentration of TeO2. The color coordinates for all studied glasses fall in green region and were (x = 0.304, y = 0.605). The CCT obtained value for all prepared glasses is 6000 K. Above study suggests that these glasses can be potentially used in green light LEDs and in other solid state lighting applications.
A series of lithium aluminosilicate glasses with the composition of 70SiO2–10Al2O3–5K2O–15Li2O–xNaCl (x = 0.5, 1.5, 2.5, 3.5 and 4.5 wt %) were prepared by the melt-quenching method. The effect of NaCl addition on mechanical properties was assessed. It was found that both the glass density and the hardness decreased with increasing content of NaCl from 0.5 to 3.5 wt %. Interestingly, Vickers hardness of the glass increased when NaCl content increased by 4.5 wt %. Raman test results show that NBO/T in the glass increases with NaCl, that is, the decrease of the degree of polymerization of the glass network due to the breaking of Si–O–Si bonds. Since the Si–O–Si covalent bond is the strongest bond in the silicate glass, the glass structure tends to be depolymerized, and the density and Vickers hardness decrease. Thus, we attribute the hardness increasing at 4.5 wt % NaCl addition to the fact that Na+ enters the network pores acting as network modifier.
The combinatorial-topological analysis and self-assembly of crystal structures of Yb72Sn46-tP118 (a = 11.076 Å, c = 36.933 Å, V = 4530.86 Å3, pr. group P4/mbm) intermetallic compounds is modeled using computer methods (the ToposPro software program). For the crystal structure of Yb72Sn46-tP118, 195 variants of a cluster representation of a 3D atomic grid with 5 (24 variants), 6 (86 variants), and 7 (85 variants) structural units are established. The variant of the fastest self-assembly involving three types of clusters-precursors forming layers of octahedra K6 = 0@6(Yb4Sn2) with symmetry g = 4/m, from polyhedra K11 = Sn@10(Yb8Sn2) with symmetry g = –1, and polyhedra K15 = Yb@14(Yb10Sn4) with symmetry g = 2 mm, as well as Yb and Sn spacer atoms, is considered. The symmetry and topological code of the processes of the self-assembly of 3D structures from clusters-precursors are reconstructed in the following form: primary chain → layer → framework.
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