Glass Physics and Chemistry最新文献

Time series of acoustic emission (AE) pulses are excited by dropping a load onto samples of ductile-brittle ZnS and ZnSe ceramics. AE activity is recorded in two frequency windows of 100–200 and 400–800 kHz. In both ceramics, low-frequency emission occurred from the moment the load is applied; the high-frequency signal appears with a time delay of 100–150 μs. Statistical analysis of the pulse series reveals a qualitative difference in emissions in the specified frequency zones. The energy distribution of pulses emitted in the 100–200 kHz range follows a random poissonian-type dependence, whereas the AE series in the 400–800 kHz range shows a correlated accumulation of microdamage. Activity in the low-frequency region appears at the initial stage of failure (plastic flow) and is attributed to dislocation glide. When the ultimate deformation is reached, a brittle accumulation of interacting microcracks occurs. The described procedure for analyzing the process of damage development under impact loading allows one to determine the transition point from the disordered degradation of the structure of ductile-brittle materials to cooperative, brittle destruction.

The results of a comparative study of the viscosity characteristics of borosilicate glasses of the Na₂O–K₂O–B₂O₃–SiO₂ system with different ratio values R = (Na₂O + K₂O)/B₂O₃ and K = SiO₂/B₂O₃ are presented. Using infrared spectroscopy, the difference in the structural role of B₂O₃ in glasses of multiboron and highly alkaline compositions, which is reflected in the nature of the change in the viscosity indices of borosilicate glasses of the Na₂O–K₂O–B₂O₃–SiO₂ system in areas with R > 1 and R < 1, is confirmed.

Highly filled (up to 55 vol %) low-viscosity (less than 3 Pa s) photocurable suspensions based on micrometer powders of barium sulfate and 1,6-hexanediol diacrylate, suitable for stereolithographic 3D printing, are produced. The 3D printing of high-resolution planar mesh structures using a digital light-emitting diode projection (DLP) is experimentally demonstrated. From the obtained composite objects, dense ceramics of a complex architecture with a hole of up to 550 µm and thin walls of up to 300 µm are produced by burning and subsequent sintering at 850°C. When studying the optical characteristics of ceramics with optically active additives, the characteristic features of both cerium ions Ce³⁺ and Eu²⁺, as well as the built-in carbon, are demonstrated.

Researchers investigated into how thickness and quenching temperature affect the mechanical and thermomechanical properties of titanium dioxide-pigmented polycarbonate. By using compression molding, specimens free of morphological effects have been generated. Dynamic mechanical analysis was used to evaluate plates with thicknesses of 0.6, 1, 2, and 3 mm under flexion, Izod impact strength, density, and tensile testing. Two distinct heat treatments annealing and second quenching were applied. The results indicate that a second quenching at 40°C for samples 3 mm thick and 35°C for samples 2 mm thick can enhance the impact strength and elongation at break, and a relationship between the mechanical, physical, and thermomechanical properties is detected. At the expense of other characteristics like elastic modulus, density, and yield stress, these properties are improved. A relaxation mode about 30°C is associated with improved impact strength and elongation at break following the second quench.

In this research, the process is presented to remove the solubility of raw materials in water instead of frittic process. Therefore a suitable glaze for single fast firing floor tile consisted of 80 wt % raw glaze and 20 wt % frit was considered. An initial batch of frittic glaze including silicate, calcite, soda, and acid boric becomes a low soluble compound first by melting and quenching in water (frittic process) and also by firing at different temperatures that firing causes the formation of low solubility phase. Then these glazes mixed with 80 wt % raw glaze. Glazes slip applied on the dried floor tile bodies and then fired in fast firing kiln. Properties of glazes (thermal expansion coefficient, T_g, micro-hardness) were compared. Also by X-ray diffraction analysis and solubility analysis proved low soluble phases formed in glaze by firing initial batch of frit at 800°C.

Synthesis of precursor powders was performed by microreactor technique in a two-step microreactor with intensively swirled reagent flows. Ceramic samples (matrices) (1 – х)ZrSiO₄‒хZrO₂ were obtained by sintering nano-sized precursor powders in the 1000–1300°C temperature range in air. X-ray phase analysis has shown that at a temperature of 1300°C, partial decomposition of zircon was observed with the formation of a silicon oxide. Their thermal behavior was studied by dilatometry, and the temperature coefficient of linear expansion was accessed. The chemical stability of the obtained ceramic matrices was evaluated by the method of prolonged leaching in distilled water, more precisely, by the release into the contact liquid of both matrix components (Zr, Si) and specially introduced radionuclides (¹³⁷Cs, ⁹⁰Sr, ¹⁵²Eu). The samples exhibited sufficiently high chemical stability, which allows us to consider them as a possible matrix material for immobilization of high-level waste.

Using computer methods (the ToposPro software package), a combinatorial-topological analysis and modeling of the self-assembly of Li₂₈Cu₄Si₈-oP40 (a = 7.969 Å, b = 4.449 Å, c = 17.244 Å, V = 611.46 ų), La₁₂Rh₁₂Al₁₆-oP40 (a = 26.949Å, b = 4.218Å, c = 7.267 Å, V = 826.05 ų), and Ca₈Pt₁₂Sn₂₀-oP40 (a = 27.701 Å, b = 4.614 Å, c = 9.371 Å, V = 1198.02 ų) crystalline structures with the Pnma space group are carried out. For Li₂₈Cu₄Si₈-oP40, the self-assembly of the crystal structure with the participation of supraclusters-trimers from K6(4a) = 0@6(Li₄Cu₂) clusters, two clusters K6(8d) = 0@6 (CuLi₅), and Si spacer atoms is considered. For La₁₂Rh₁₂Al₁₆-oP40, the self-assemblies of the crystal structure with the participation of K3(8d) = 0@3(LaRhAl) clusters and K6(4a) = 0@6(La₂Rh₂Al₂) clusters from the linked LaRhAl clusters and K4(8d) = 0@4(LaRhAl₂) clusters are considered. For Ca₈Pt₁₂Sn₂₀-oP40, the self-assembly of the crystal structure from clusters-precursors in the form of the K6 = 0@6(CaSn₃Pt₂) double tetrahedra and K4 = 0@4(CaSn₂Pt) tetrahedra is considered. The symmetry and topological code of the processes of the self-assembly of Li₂₈Cu₄Si₈-oP40, La₁₂Rh₁₂Al₁₆-oP40, and Ca₈Pt₁₂Sn₂₀-oP40 from K3, K4, and K6 clusters-precursors are reconstructed in the following form: primary chain → layer → framework.

It is established that the ZnO–Al₂O₃ oxide coating formed on the surface of aluminosilicate fibers contains hexagonal 13-nm ZnO crystals. The obtained composites demonstrate intense generation of singlet oxygen under the influence of UV radiation. Increasing the radiation power density provided a significant increase (+60%) in the intensity of singlet oxygen generation. It is established that the application of an oxide coating significantly accelerates the processes of adsorption of the aniline blue organic dye from aqueous solutions on the surface of fibers and its photocatalytic decomposition under the influence of near-UV radiation. The kinetics of the dye adsorption process are clearly described by a pseudo-second-order kinetic equation. The application of an oxide coating on the surface of the fibers significantly accelerates the photolysis processes of the dye in the solution. The photolytic decomposition rate of the dye in solution is described by a pseudo-second-order kinetic equation.

Xerogel in the ZrO₂–Y₂O₃ system s are obtained by using the traditional method of coprecipitation of hydroxides and in a microreactor with countercurrent intensely swirling flows of reagents. Their physical and chemical properties are studied. The patterns of influence of the synthesis method on the phase composition of powders and ceramics based on zirconium dioxide are revealed. Ceramic materials with high strength characteristics, consisting of a mixture of cubic and tetragonal modifications of ZrO₂ are obtained.

Using computer methods (the ToposPro software package), combinatorial-topological analysis and modeling of the self-assembly of Y₈Rh₁₂Sn₂₀-oS40 (a = 4.387 Å, b = 26.212 Å, c = 7.155Å, V = 822.77 ų), Lu₁₆Zn₂₀Ge₂₄-oS60 (a = 4.179 Å, b = 18.368 Å, c = 15.050 Å, V = 1155.24 ų), and Ba₈Ir₁₆In₅₂-oS76 (a = 4.485 Å, b = 29.052 Å, c = 13.687 Å, V = 1783.63 ų) crystal structures with the Cmc2₁(36) space group are carried out. For Y₈Rh₁₂Sn₂₀-oS40, 18 variants for identifying cluster structures with the number of clusters N = 1 (variant 1), 2 (variant 11), and 3 (6 variants) are established. The variant of the self-assembly of a crystal structure with the participation of clusters-precursors forming the packing in the form of the K6 = 0@6(YSn₃Rh₂) and tetrahedra K4 = 0@4(YSn₂Rh) double tetrahedra is considered. For Lu₁₆Zn₂₀Ge₂₄-oS60, 66 variants are established for identifying cluster structures with the number of clusters N = 1 (1 variant), 2 (25 variants), 3 (20 variants), and 4 (20 variants). The variant of the self-assembly of a crystal structure with the participation of K3(D1) = 0@3(Lu Ge₂), K3(D2) = 0@3(Lu Zn Ge), K3(D3) = 0@3(Lu Zn Ge), K3(D4) = 0@3Lu Zn Ge), and K3(D5) = 0@3(GeZn₂) 3-atom clusters-precursors forming the packing is considered. For Ba₈Ir₁₆In₅₂-oS76, 129 variants are established of the allocation of cluster structures with the number of clusters N = 2 (36 variants) and N = 3 (103 variants). The variant of the self-assembly of a crystal structure with the participation of the clusters-precursors forming the packing is considered: K6 = 0@6(BaIn5) pentagonal pyramids, K4a = 0@4(BaRhIn2) tetrahedra and K4b = 0@4(Rh₂In2) tetrahedra, K3 = 0@4(RhIn₂) rings, and In spacer atoms. The symmetry and topological code of the self-assembly processes of the Y₈Rh₁₂Sn₂₀-oS40, Lu₁₆Zn₂₀Ge₂₄-oS60, and Ba₈Ir₁₆In₅₂-oS76 crystal structure from K3, K4, and K6 clusters-precursors in the following form is reconstructed: primary chain → layer → framework.