Glass Physics and Chemistry最新文献

A new method for molecular dynamics (MD) modeling of the glass structure using a crystal structural template is proposed. The template is based on the unit cell of the crystalline phase, whose composition is qualitatively similar to the modeled glass. Using this approach and multistage MD simulation, the model of the spatial structure of grade E borosilicate glass, reproducing its physicochemical characteristics, is obtained. The proposed method enables to model the glass structure using classical MD methods with greater productivity and stability.

A technique for the experimental determination of the thermophysical characteristics of inactive aluminophosphate and borosilicate glasses by differential scanning calorimetry (DSC) is proposed and tested. The advantages of this measurement technique are shown. For glassy matrices of various compositions, the specific heat capacity and thermal conductivity coefficient are determined. The obtained experimental values make it possible to calculate the thermal conductivity values. The applicability of this method is proved by working with real samples of vitrified high-level waste to study their properties and form a database based on them.

In this work an attempt is made to study the impact of the quenching rate upon structure, hyperfine interactions, magnetic and mechanical properties of Fe₇₈Si₉B₁₃ metallic glasses. Other involved parameters in melt spinning method were kept invariant. Analytical techniques comprising X-ray diffraction, transmission Mössbauer spectrometry, vibration sample magnetometer, Vickers microhardness and differential scanning calorimetry were employed. Minor effect of quenching rate upon the macroscopic magnetic properties was detected. It was shown that notable changes in the local atomic arrangement, structure, and mechanical properties were unveiled, dominantly by represent the crystallization at the lowest quenching rate.

Blast furnace slag is produced in large quantities as a by-product in the steel manufacturing process. In this study, a method for synthesizing lead ion adsorbent with high adsorption ability was investigated by alkali activation of the blast furnace slag. A sodium hydroxide aqueous solution was used as an alkali activator, and silica was added to the aqueous solution to improve the adsorption capacity. Alkali activation of the blast furnace slag with the sodium hydroxide aqueous solution yielded lead ion adsorbent. Addition of silica to the sodium hydroxide aqueous solution further increased the lead ion adsorption capacity. Langmuir adsorption isotherms revealed that the highest maximum adsorption capacity of 1658.1 mg-Pb/g was obtained when 5 g of silica was added to 50 mL of the sodium hydroxide aqueous solution. The adsorption capacity for lead ion decreased when more than 10 g of silica was added to the sodium hydroxide aqueous solution.

The article presents the results of a study of new ceramic materials φ-Bi₈Pb₅O₁₇ obtained by pyrolysis using mannitol C₆H₁₄O₆ as a reducing fuel. The values of the band gap of the obtained compositions are determined by analyzing the diffuse reflectance spectra using the Tauc construction. They are in the range from 2.57 to 2.67 eV, which corresponds to visible light photocatalysts. The degree of degradation of methylene orange when using synthesized samples ranged from 95 to 99% when irradiated for 3 h with a fluorescent mercury lamp.

The stability of synthetic and natural zeolites in model biological media simulating the environment of the stomach (pH 1.8), blood plasma (pH 6.9), and intestines (pH 8) is studied. The effect of long-term exposure (up to 7 days) to biological media on the crystal structure of Beta, Rho, Y, and clinoptilolite zeolites is studied. The degree of degradation of the crystal structure of zeolites is controlled by X-ray phase analysis. Based on the results obtained, conclusions are drawn on the prospects for the use of synthetic and natural zeolites as drug carriers.

By using the method of coprecipitation of hydroxides in the ZrO₂–CaO–MgO system, xerogels, powders, and ceramics based on them are obtained. The effect of low temperatures during the preparation of precursors on the phase composition and physicochemical properties of the materials is studied. It is shown that the use of precipitate’s cryotreatment makes it possible to reduce the open porosity and water absorption of the ceramics.

Xerogels and powders of a solid solution based on zirconium dioxide are synthesized by the method of coprecipitation of hydroxides from aqueous solutions of salts of zirconium nitrate ZrO(NO₃)₂⋅2H₂O, aluminum Al(NO₃)₃⋅9H₂O, and cerium Ce(NO₃)₃⋅9H₂O with an aqueous 1 M solution of ammonia NH₄OH. A dense ceramic with low porosity and water absorption is obtained. The effect of the ultrasonic treatment of the precipitate and mechanical treatment of the xerogel on the physicochemical properties of the obtained materials is evaluated.

The dielectric constant (ε'), loss factor (tanδ), and ac conductivity (σ_ac) of 30 Li₂O–10CdO–(60 – x)-B₂O₃:xLn₂O₃, where (x = 0 and 1) and (Ln = Pr, Nd, Sm, and Eu) were investigated using a frequency range of 10²–10⁵ Hz and temperature ranging from 30 to 250°C in this work. The differential scanning calorimetry (DSC) technique was employed to confirm the glassy nature of the materials under study. The dielectric parameters ε', tan δ, and σ_ac rise when rare-earth ions are added to the glass matrix at any frequency or temperature. Dielectric breakdown and activation energies are lower in doped than in undoped glasses while ac current flows through them at room temperature. Rare-earth ion doping’s dielectric parameter values decrease with temperature as atomic number (Z) rises. The dielectric parameter values for the Pr³⁺ doped glass matrix is the highest. QM tunnelling model was used to describe the ac conduction behaviour of these glasses.

Using the ToposPro software package, a combinatorial-topological analysis and modeling of the self-assembly of the following crystal structures with space group I4/mcm are realized: Pu₃₁Rh₂₀-tI204: a = 11.076 Å, c = 36.933 Å, V = 4530.86 ų, Pu₂₀Os₁₂-tI32: a = 10.882 Å, c = 5.665 Å, V = 670.8 ų. (Pu₄Co)₂ (Pu₄)-tI28: a = 10.475 Å, c = 5.340 Å, V = 585.9ų. (Ti₄Ni)₂(Bi4)-tI28: a = 10.554 Å, c = 4.814 Å, V = 536.2ų, Bi₄-tI8: a = 8.518 Å, c = 4.164 Å, V = 302.15 ų. For the crystal structure of Pu₃₁Rh₂₀-tI204, 113 variants of the cluster representation of the 3D atomic network with the following number of structural units are established: 4 (14 variants), 5 (61 variants), and 6 (38 variants). A variant of the self-assembly of the crystal structure with the participation of three types of framework-forming polyhedra is considered: K15 = Pu@14(Rh₂Pu₅)₂ with symmetry –42m, double pyramids K10 = (Rh@Pu₄)₂ with symmetry 4, and octahedra K6 = 0@8(Rh₂Pu₆) with symmetry mmm and spacers Rh. For the crystal structure of Pu₂₀Os₁₂-tI32, framework-forming pyramid-shaped polyhedra K5 = 0@OsPu₄ with symmetry 4, as well as spacers Pu and Os, are defined. For the crystal structure (Ti₄Ni)₂(Bi4), frame-forming pyramids K5 = 0@Ti₄Ni and tetrahedra K4 = 0@Bi₄) are defined. For the crystal structure (Pu₄Co)₂(Pu₄)-tI28, frame-forming pyramids K5 = 0@ Pu₄Co and tetrahedra K4 = 0@Pu₄ are defined. For the crystal structure of Bi₄-tI8, frame-forming tetrahedra K4 = 0@Bi₄ are defined. The symmetric and topological code of self-assembly processes of 3D structures is reconstructed from clusters-precursors in the following form: primary chain → layer → framework.