Glass Physics and Chemistry最新文献

The development of an inexpensive and environmentally friendly method for synthesis of mesoporous silica is highly desirable. In this study, mesoporous silica SBA-15 (SP-SBA-15) was synthesized using inexpensive amorphous silica powder, which is produced industrially, as the silica source. SP-SBA-15 was compared to SBA-15 (TO-SBA-15) synthesized by a conventional method using tetraethyl orthosilicate (TEOS) as the silica source. SP-SBA-15 was found to have 8.1 nm uniform mesopores arranged in a well-defined hexagonal honeycomb structure, and the mesostructure was found to be almost identical to that of TO-SBA-15. However, the specific surface area of SP-SBA-15 was found to be 525.0 m²/g, which is lower than that of TO-SBA-15. This is due to the fact that fewer micropores were formed in the SBA-15 when silica powder was used as the silica source.

Using computer methods (ToposPro software package), a combinatorial-topological analysis and modeling of the self-assembly of crystalline structures of the Ce₄Pt₁₄Si₈-oP52 (a = 19.633 Å, b = 4.036 Å, c = 11.224 Å, V = 889.4 ų) and Ce₆Pd₈Sn₁₂-oP52 (a = 27.701 Å, b = 4.614 Å, c = 9.371 Å, V = 1198.02 ų) family are carried out. For the crystal structure of Ce₄Pt₁₄Si₈-oP52, 21 variants of the allocation of cluster structures with the number of clusters N = 2 (6 variants) and 3 (9 variants), and 3 (6 variants) are established. A variant of the self-assembly of a crystal structure with the participation of clusters-precursors forming the following packing is considered: double tetrahedra K6 = 0@6 (Ce₂Pt₂Si₂) with symmetry g = –1, tetrahedra K4 = 0@4 (CePt₂Si), and rings K3 = 0@3 (Pt₂Si). For the crystal structure of Ce₆Pd₈Sn₁₂-oP52, 27 variants of the allocation of cluster structures with the number of clusters N = 2 (6 variants), 3 (11 variants), and 4 (10 variants) are established. A variant of the self-assembly of a crystal structure with the participation of clusters-precursors forming the following packing is considered: double tetrahedra K6 = 0@6 (Ce₂Pd₂Sn₂) with symmetry g = –1, rings K3 = 0@3 (CePdSn), rings K3 = 0@3 (PdSn₂), and spacer atoms Sn. The symmetry and topology code of the self-assembly processes of 3D Ce₄Pt₁₄Si₈-oP52 and Ce₆Pd₈Sn₁₂-oP52 structures are reconstructed from clusters-precursors in the following form: primary chain → layer → framework.

Scientific principles for the synthesis of precursors of nanostructured oxide systems Al₂O₃–ZrO₂–Ln_xO_y ((Ln = Dy, Nd) are developed. The features of their formation under conditions of rapid mixing of electrogenerated reagents, implemented in a diaphragm-free coaxial reactor-electrolyzer, are studied. The methods of potentiodynamic polarization curves, X-ray diffractometry, X-ray fluorescence, synchronous thermal analysis, and laser diffraction are used to study the anodic processes occurring in the electrolyzer, the morphology of particles formed in the solution and transformed during heat treatment, as well as the phase, granulometric, and elemental compositions of precursors and oxide systems. The proposed approach allows obtaining oxide systems modified with rare earth elements based on the Al₂O₃–ZrO₂ binary system, characterized by the presence of a stabilized phase of tetragonal zirconium dioxide. REE atoms present in the studied systems—Nd and Dy—stabilize t-ZrO₂ and, apparently, occupy the positions of crystal lattice nodes, isomorphically replacing Zr⁴⁺. The latter is indicated by the broadening of the corresponding reflections of X‑ray diffraction patterns. It indirectly indicates the presence of microstresses in the microcrystals of the phases. The latter can be caused by distortions of the crystal lattices of aluminum and zirconium oxides as a result of the substitution of metal atoms by REE atoms.

Glasses containing compositions of BaO–Bi₂O₃–B₂O₃–TMI (V₂O₅, MnO) were prepared and subjected to thorough analysis through differential scanning calorimetry (DSC), dielectric measurements and AC conductivity studies. The DSC investigations unveiled a noteworthy trend of an increase in TMI content correlated with a decrease in the glass transition temperature. Delving deeper into the properties of the prepared samples, the frequency dependence of dielectric constant and dielectric loss were explored. The investigation uncovered that AC conductivity experiences an augmentation at low and intermediate frequencies, plateauing at higher frequencies. Addition of TMI into the glass network induced a discernible rise in AC conductivity. Further investigation of the samples revealed a non-Debye behavior, a conclusion substantiated by the suppressed Cole–Cole plots and corroborated by electric modulus studies. Intriguingly, the addition of a minute concentration of TMI, whether it is vanadium or manganese, did not exert an influence on the relaxation time of ions. However, it exerts an impact on the dissipation energy of the samples, thus attesting to the nuanced and specific role played by TMI in modulating the electrical properties of the glass network.

The ability to tailor the bandgap in semiconductor nanostructures from the ultraviolet to visible range is imperative in various light-mediated optoelectronic applications. In this work, Zn-doped TiO₂ nanostructures were prepared and annealed at 350°C for different time intervals such as 1, 2, and 3 h to tailor the band gap. The effects of annealing time on the structural and optical properties of Zn-doped TiO₂ nanostructures were investigated. According to XRD studies, increasing the annealing time authenticates that the dislocation density in the nanostructures decreases, whereas the crystallite size increases. TEM image of the sample annealed at 350°C for 3 h shows the average grain size distribution as 12.33 ± 0.12 nm. The XPS spectrum of the nanostructures that underwent a 3 h annealing at 350°C reveals a broad peak centered at 1021.06 eV, which indicates the Zn²⁺ oxidation state of Zn atoms. The photoluminescence studies indicate that the intensity of UV-visible luminescence bands changes with a rise in annealing time. UV-visible spectroscopic analysis reveals that the band gap increases from 3.32 to 3.36 eV and then decreases to 3.25 eV when the annealing time is raised linearly. Moreover, Zn-doped TiO₂ that has been annealed at 350°C for 3 h has a red shift in the absorption edge and a reduction in the optical band gap, suggesting that it may find application in optoelectronic devices.

If we assume that two bodies are in contact and only the pressure between them changes, then the deformation of the material changes proportionally to the cube root of our pressure (Heinrich Hertz, 1884¹). The convergence of elastic bodies is proportional to the pressure to the power of 2/3, and not to the pressure to the power of one (M.S. Leibenson, 1947²). Let us point out that the dependence of the form h = const F ^2/3 or F = const h^3/2 occurs not only for balls but also when other finite bodies come into contact (L.D. Landau and E.M. Lifshitz, 1953³).

The processes of vaporization and thermodynamic properties of melts of the BaO–Al₂O₃–SiO₂ system are studied using the method of high-temperature differential mass spectrometry in the concentration range from 90 to 10 mol % BaO and molar ratio of x(Al₂O₃) : y(SiO₂), equal to 3 : 2, 1 : 1, and 1 : 2. The samples are evaporated from Knudsen effusion cells made of tungsten. The partial pressures of gaseous species, activities of condensed phase components, Gibbs energies, and excess Gibbs energies are determined. It is established that the studied system is characterized by a negative deviation from ideal behavior.

This paper presents the results of a study of the toxicity of high-silica quartzoid glasses (QGs) containing cesium, obtained on the basis of two-phase alkali borosilicate glass. It is established that the toxicity of the studied QGs in relation to Paramecium caudatum does not exceed the permissible level and varies depending on the content of alkaline ions in the QG and the time of contact of fine QG powder with water. It is assumed that the identified toxicity is associated primarily with the extraction of sodium and cesium ions into the aqueous solution.

Bioactive glasses with a composition of (80 – x)NaPO₃–xB₂O₃–5CaF₂–15MgO, where x varies from 20 to 40 mol % were prepared through the melt quench technique. To examine the amorphous characteristics of the glasses and any structural modifications, X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) analysis were conducted, respectively. The density of the fabricated glasses decreased as the B₂O₃ composition ranged from 20 to 40 mol %. Furthermore, the glasses were immersed in simulated body fluid (SBF) solution for 21 days for in vitro bioactivity studies. After this period, the development of apatite on the glass surfaces was assessed through XRD, FTIR, scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDX) technique. The EDX analysis reveals an elevation in the levels of boron and calcium in the glasses that were immersed in the SBF solution for 21 days. This increase underscores the material’s bioactivity and its potential to facilitate bone regeneration and ensure long-term stability. These findings position it as a promising material for use in applications related to bone regeneration and tissue engineering. The thermal properties of the glasses were analyzed through differential scanning calorimetry (DSC), and the glass transition temperature (T_g) was determined. Interestingly, the prepared glasses revealed the presence of a boron anomaly. By systematically varying the level of B₂O₃ to NaPO₃ substitutions in the glass system, the effect of composition on several important properties is elucidated.

Substituted apatites with a varying content of La³⁺ and Ce³⁺ ions are synthesized. The formation of substituted hydroxyapatite (La-HA, Ce-HA) is proved by XRD and IR spectroscopy. The change in the crystal lattice parameters of the synthesized phases is shown, which indicates the replacement of Ca²⁺ ions by REE ions in the hydroxyapatite structure. The presence of REE ions in solid phases is proved by ICP–AES. When studying the resorption of the synthesized samples, it is found that cation-substituted hydroxyapatites are less soluble than undoped HA.