Glass Physics and Chemistry最新文献

Thermoplastic elastomers (TPEs) reinforced with detonation nanodiamonds (DNDs) based on styrene-butadiene rubber are developed. The mechanical characteristics of the reinforced compounds with different DND contents are investigated. The developed material shows a 30% increase in compressive strength compared to the unfilled composite and a 10% increase in the tensile strength of the material with the introduction of 0.1% DND.

With the help of computer methods (ToposPro software package), a combinatorial topological analysis and modeling of the self-assembly of Lu₄Te₄-oF8 (Fm-3m, V = 211.0 ų), Te₄Lu₂₈-oC32 (Cmcm, V = 908.3 ų), Lu₃(TeLu₃)Lu₂-hP9 (P-62m, V = 908.3 ų), and Lu₆₆Te₂₄-mC90 (C12/m1, V = 2467.2 ų) crystal structures are carried out. For the crystal structure of Lu₄Te₄-oF8, cluster precursors K8 = 0@Te₄Lu₄ with symmetry –43m; for Te₄Lu₂₈-oC32, tetrahedral cluster precursors K4 = 0@Lu₄ and K4 = 0@TeLu₃ with symmetry 2 and m; and for Lu₃(TeLu₃)Lu₂, cluster precursors K7 = 0@Lu₃(TeLu₃) with symmetry 3m and spacers Lu are established. For the crystal structure of Lu₆₆Te₂₄-mC90, pyramid-shaped cluster precursors K5 = 0@Lu₅ with symmetry 2, tetrahedra K4 = 0@Lu₄ with symmetry 2, tetrahedra K4 = 0@TeLu₃, and tetrahedra K4 = 0@Te₂Lu₂ are established, and rings K3 = 0@TeLu₂ are involved in the formation of supraclusters-trimers. 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.

The low-temperature heat treatment of K8 glass is carried out at temperatures of 350–500°C in alkaline melts of NaNO₃ and CsNO₃ salts in the field of gamma radiation from the ⁶⁰Co source at the dose rate of 3000 R/s and also outside the field. Under the influence of thermoradiation treatment due to the ({text{Na}}_{{{text{glass}}}}^{ + }) ↔ ({text{Cs}}_{{{text{melt}}}}^{ + }) ion-exchange diffusion, mechanical compressive stresses are created in the surface layer of the glass, which lead to the formation of a waveguide layer of the given thickness and an increase in the refractive index (RI) increment, the number of waveguide modes, and the depth of the waveguide layer.

Molecular dynamics (MD) with ReaxFF potentials is used to study the melting process of quartz and cristobalite together with the amorphous structures obtained at different stages of melting by cooling the melt. The long-term preservation of an excess of eight-membered rings inherited from the crystalline phase is found in the quartz melts, while in the cristobalite melts, the similar preservation of six-membered rings is not observed. Thus, it can be stated that the quartz melts and glasses obtained from them have structural memory, in contrast to cristobalite melts. An increase in the number of four-membered rings with increasing temperature is revealed. A number of other features of the obtained amorphous structures, which we consider as models for glasses, are discussed.

Effect of Dy₂O₃ on the properties of borotellurite glasses, (B₂O₃)_0.2–(TeO₂)_0.22 – x–(ZnO)_0.28–(Li₂O)_0.20–(WO₃)_0.10–(Dy₂O₃)_x; x = 0.01 to 0.06 has been investigated. Density increased and molar volume decreased with increase of Dy₂O₃ and they were explained in terms of composition. Glass transition temperature increased and thermal stability decreased with increase of Dy₂O₃ content. Conductivity increased and its activation energy decreased up to 0.04 mole fraction of Dy₂O₃ and behaved in opposite way for higher amounts of Dy₂O₃. These results are ascribed to network changes occurring around 0.04 mole fractions of Dy₂O₃. For the first time the effect of Dy₂O₃ on conductivity has been reflected in this fashion. Polaron hopping distance, polaron radius and Debye’s temperature were determined and discussed appropriately.

Geometric and topological analysis of the Pd₁₁₂Co₂₀₄Al₆₈₄-cP1000 crystal structure with the sp. gr. Pa-3, a = 24.433 Å, and V = 14587.24 ų is performed using the ToposPro software package. Metal precursor clusters of crystalline structures are determined using an algorithm for decomposing structural graphs into cluster structures and by constructing a basic grid of the structure in the form of a graph whose nodes correspond to the position of the centers of precursor clusters (S_{3}^{0}.) A total of 26 906 variants of the cluster representation of a 3D atomic mesh with the number of structural units ranging from 3 to 12 are established. The self-assembly of the crystal structure from new three-layer K155(4a) = Al@Al₆Pd₈)@Pd₁₂Al₃₀@Pd₈Co₁₈Al₇₂ and bilayer precursor clusters K55(4b) = Co@Al₁₂@Co₁₂A_l30 with symmetry g = –3 is considered. In the unit cell, positions 4a are occupied by Al atoms, which are the central atoms of the 15-atom polyhedron K15(4a) = Al@Al₈Pd₆, and positions 4b are occupied by Co atoms, which are the central atoms of the 13-atom icosahedron K13(4b) = Co@Al₁₂. The symmetric and topological code of the processes of self-assembly of 3D structures from precursor clusters K155 and K55 is reconstructed as follows: primary chain → microlayer → microframework. Al atoms are established as spacers occupying voids in the 3D framework of the K155 and K55 nanoclusters.

Finely dispersed mesoporous powders of the following composition are synthesized by the method of cocrystallization of nitrate salts with ultrasonic treatment: La_1–xSr_xNiO_3–δ, La_1–xSr_xCoO_3–δ, and La_1–xSr_xFe_0.7Ni_0.3O_3–δ (x = 0.30; 0.40). Based on them, ceramic nanomaterials of the given composition with a coherent scattering region (CSR) of ~65–69 nm (1300°С) are obtained. Ceramics fired at 1300°C are single-phase and have a tetragonal and orthorhombic perovskite-type structure in the La₂O₃‒SrO‒Ni(Co,Fe)₂O_3–δ system. Solid solutions have mixed electron–ion conductivity with transfer numbers t_e = 0.98–0.90 and t_i = 0.02–0.10. Ceramics with a tetragonal perovskite-type crystal structure exhibit higher electrical conductivity than materials having an orthorhombic perovskite-type crystal structure. According to their electrophysical properties related to the structural features of solid solutions, ceramic materials obtained based on them are promising as solid oxide cathodes for average-temperature fuel cells.

The combinatorial topological analysis and modeling of self-assembly of the Pu₅₆Hg₃₅₂-cF408 (a = 21.780 Å, V = 10331.75 ų, space group F-43m) and Zr₄Pu₁₁₂-tI116 ((a = b = 18.189 Å, c = 7.857 Å, V = 2599.86 ų, space group I4₁/a) crystal structures are performed by computer methods (the ToposPro software package). The method of complete decomposition of the 3D structure graph into cluster structures was used to determine the framework-forming nanoclusters. For Pu₅₆Hg₃₅₂-cF408, 88 variants of decomposition of the 3D structure graph with the number of clusters from 2 to 6 were determined. New two-layer nanoclusters K26 = 0@Pu₄@Pu₄Hg₁₈ and K46 = 0@Hg6@Pu₄Hg₃₆ with ‑43m symmetry were found to form a 3D packing. The framework voids contain Hg₄ tetrahedral clusters and Hg spacer atoms. For Zr₄Pu₁₁₂-tI116, framework-forming nanoclusters K17 = Zr@Pu16 with -4 symmetry are installed. The framework voids contain Pu₄ tetrahedra and Pu spacer atoms.

The phase tree of the previously studied СаO–MgO–SiO₂ system was constructed. The phase tree includes three cycles. The phase tree is represented by fifteen simplices separated by fifteen stable secants. The formation of six double and four ternary compounds of congruent and incongruent melting was noted in the system. On the basis of the phase tree, taking into account the data on faceting elements, a forecast of crystallizing phases in stable secants and in phase secondary triangles was carried out. For the figurative points of the composition, corresponding to the intersections of stable and unstable secants, the chemical interaction is described on the basis of thermodynamic data. It has been shown that ternary compounds can be synthesized by several reactions.

The study of the mechanical properties of materials is of considerable fundamental and practical interest to most scientists. In this work the values of the equilibrium cell parameter, bulk modulus, its first derivative with respect to the pressure, and the speed of sound for diamond were calculated using the density functional theory (DFT) method and are 3.570 Å, 433.2 GPa, 3.71 and 17731.2 m/s. These parameters are found to be in good agreement with the experimental ones. The results of the study show that the mechanical properties of materials can be predicted with a high precision using the DFT method.