Glass Physics and Chemistry最新文献

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.

This article presents the results of the interpretation and refinement of the crystal structure of an Sr_0.5Ba_0.5Bi₂O(BO₃)₂ solid solution. The distribution of cations over positions is refined, which shows that Sr is included in the smallest positions M3 and M1, Ba is in positions M1 and M2, and Bi is found in all three large cationic positions. The crystal structure of Sr_0.5Ba_0.5Bi₂O(BO₃)₂ is compared with the end members of the series of SrBi₂O(BO₃)₂ and BaBi₂O(BO₃)₂ solid solutions.

Composite materials (CMs) based on porous glass matrices activated by yttrium in the presence of copper or bismuth are synthesized. It is established that, depending on the composition, the CM samples exhibit UV, blue-green, red, and infrared luminescence due to the presence of various centers, including Bi³⁺ and Cu⁺ ions, F centers in Y₂O₃, and molecular ions ({text{O}}_{3}^{{ - 2}}) associated with cation vacancies Y³⁺.

In this paper, a new diamond–silicon carbide ceramic composite material—Ideal—is studied and its mechanical characteristics are determined. For the first time, a comprehensive determination of Poisson’s ratio, shear modulus, bulk modulus, and transverse sound velocity is carried out. Poisson’s ratio is in the region of 0.008 to 0.01, which, in turn, indicates the absolutely brittle nature of the failure of the Ideal ceramic under loading. The criteria that allow evaluating different materials used for body armor are calculated.

This article presents the results of a study of new solid solutions formed in the system of diphosphates of alkaline elements and zinc: K₂Zn₃(P₂O₇)₂–Cs₂Zn₃(P₂O₇)₂. The obtained materials are promising as matrices for creating phosphors. The formation of phases containing two alkali cations is established on samples obtained by solid-phase synthesis by X-ray phase analysis, and the results of studying their thermal stability are presented.

A single-stage centrifugation method is used for the precipitation and crystallization of a solution of a hybrid halide perovskite compound of the CH₃NH₃PbI₃ composition. The perovskite films are annealed in the temperature range of 80–140°C, during which the excess of the N-methylpyrrolidone solvent was removed by evaporation. The X-ray phase analysis of the synthesized perovskite layer is carried out. The morphology of the surface of the layers after crystallization and the transmission spectra in the optical range are studied. The experiments and research results showed that the optimal temperature regime for the formation and crystallization of lead triiodide methylammonium perovskite films is 100–110°C. The perovskite layers obtained in these processing regimes have a surface morphology with a uniform granular crystal structure and are highly uniform. Moreover, in solar cells based on perovskite-like CH₃NH₃PbI₃ structures with an annealing temperature of 100–110°C, the short-circuit currents reached 16.0 mA/cm². At the same time, at annealing temperatures of perovskite layers above 120°С, the maximum value of the short-circuit currents did not exceed 14.0 mA/cm².

The use of glass powder instead of cement as an auxiliary cementitious material can better alleviate environmental problems and energy problems. This experiment studies the influence of the fineness of glass powder and the substitution rate on the performance of mortar, to guide the actual project. The study found that with the increase of the substitution rate, the initial setting time becomes longer, the finer the fineness, the longer the initial setting time, but the difference between P-60 and P-90 decreases with the increase of the substitution rate. With the increase of substitution rate, the compressive strength of 7, 28 and 90 d increased first and then decreased. When the substitution rate was 5%, the compressive strength reached the maximum, but the 7 d compressive strength of P-30 with 5% substitution rate decreased slightly. With the increase of substitution rate, the cumulative hydration heat decreased gradually. The difference between P-60 and P-90 was not significant. Similar to the cumulative hydration heat, the hydration heat flow per gram of cement decreased gradually with the increase of substitution rate. It can be seen from nanoindentation that fineness and substitution rate have little effect on the properties of hydration products. With the increase of substitution rate, the total porosity decreases first and then increases. The porosity of glass powder mixed with P-30 is the largest, followed by P-60 and P-90, but the difference between the total porosity of P-60 and P-90 is not significant. In practical engineering, these two factors need to be considered in combination.

The data of X-ray diffraction and IR spectroscopy of synthetic aluminosilicates of the kaolinite subgroup with different degrees of crystallinity are analyzed. The samples are obtained under hydrothermal conditions in alkaline and neutral media with different durations of synthesis. It is shown that as the synthesis time increases a gradual transition of the amorphous phase to the crystalline phase is observed, which is reflected in the IR spectra by the shift of the bands related to the oscillations of the groups in the octahedral and tetrahedral grids. The first band of stretching vibrations of hydroxyl groups at 3628 cm^–1 appears after three days of hydrothermal treatment in a neutral medium, and under alkaline conditions with the same duration of treatment, two more bands are observed at 3687 and 3668 cm^–1. The detected changes in the IR spectra correspond to the appearance of the characteristic X-ray reflections of halloysite according to the XRD data. Thus, IR spectroscopy can be considered as a method for a qualitative assessment of the degree of crystallinity.

Composite materials (CMs) based on matrices of high-silica nanoporous glasses activated by silver and lanthanum are synthesized. It is established that, depending on the composition, the CM samples exhibit luminescence in the UV, violet-blue, green, red, and infrared spectral ranges due to the presence of isolated Ag⁺-ions, Ag⁺–Ag⁺ paired centers, molecular clusters (MCs) and nanoparticles (NPs) of silver, and oxygen vacancies in La₂O₃, together with various silicon defect centers.

MgO–Al₂O₃–SiO₂ (MAS) glass has widespread applications due to the excellent chemical stability and mechanical strength. Accommodation of macroscopic properties requires a systematic investigation of the microstructure of glass caused by compositional adjustment. In this work, effects of progressive replacement of MgO by Al₂O₃ or SiO₂ on glass structure and Vickers hardness were investigated. With the replacement of MgO by Al₂O₃ or SiO₂, the glass network was strengthened, as a result, the glass transition temperature was increased and the crystallization tendency was weakened. The degree of structural changes caused by substitution of SiO₂ for MgO is more significant than that of Al₂O₃ substitute for MgO. The strengthened glass network promotes the increase of Vickers hardness, and the coefficient of thermal expansion can be tailored in a large range. The results show that MAS glass maybe useful in the field of glass substrates for TFT–LCDs.