Glass Physics and Chemistry最新文献

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.

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.

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.

Using computer methods (ToposPro software package), a combinatorial-topological analysis and modeling of the self-assembly of Li₄₀P₄Ge₂₀-oP64 (V = 1082.85 ų, Pnma) and Ti₄₀P₂₄-oP64 (V = 955.14 ų, Pnma) crystalline structures is carried out. For the crystal structure of Li₄₀P₄Ge₂₀-oP64, 36 variants of the identification of cluster structures with the number of clusters N = 2, 3, and 4 are established. The self-assembly of a crystal structure with the participation of clusters-precursors K11 = 0@11(Li₅(LiGe₅)) is considered in the form of pentagonal pyramids LiGe₅ with five Li atoms located on five faces of the pyramid, rings K3 = @3(Li₂P), and Li spacer atoms. For the crystal structure of Ti₄₀P₂₄-oP64, 55 variants of the identification of cluster structures with the number of clusters N = 2, 3, 4, and 6 are established. The self-assembly of a crystal structure involving clusters-precursors in the form of six-atom double tetrahedra, K6(4a) = 0@6(Ti₄P₂), K6(4b) = 0@6 (Ti₄P₂), three-atom rings K3 = 0@3(TiP₂) and K3 = 0@3(Ti₂P), and tetrahedrons K4 = 0@4 (Ti₃P) is considered. The symmetric and topological code of the self-assembly processes of 3D Li₄₀P₄Ge₂₀-oP64 and Ti₄₀P₂₄-oP64 structures from clusters-precursors is reconstructed in the following form: primary chain → layer → framework.

The temperature dependences of the specific heat capacity of glasses based on bismuth and sodium borates, obtained by comparison under conditions of melt cooling into the environment, have been studied. An interpretation of the observed effects is given on the basis of the features of the molecular structure and the thermal mobility of its fragments. Viscosity changes of the melt and cooling rate strongly affects the temperature dependence of c_p, s/c_p max at temperatures above the glass transition temperature. The calculated specific heat of the melt increases with decreasing cooling rate, increasing viscosity and it approaches the values of the specific heat at the maximum corresponding to the temperature vitrification. Adding NaOH to borate glass affects the value and position of the maximum specific heat to a lesser extent than the Bi₂O₃ addition.

La₂O₃–SiO₂ systems are synthesized from kaolin and tetraethoxysilane. The thermal decomposition of images after freeze-drying when heated to 1000°C is studied using thermogravimetry and differential scanning calorimetry. The morphology of the samples is studied by transmission electron microscopy (TEM) and dynamic light scattering (DLS); the acid–base properties of the surface are determined by the indicator method. During the heating of samples in the temperature range of 25–600°C, endothermic effects are discovered, accompanied by weight loss. The structure of the kaolin sample is heterogeneous; nanoparticles (10 nm) of lanthanum oxide are located on the surface of microparticles (220–270 nm) of silicon oxide. The sample obtained from tetraethoxysilane has a homogeneous nanostructure with particle sizes of 5–13 nm, but is characterized by less intense sorption values at Brønsted acid sites (pK_a 1.7; 3.46) compared to the sample from kaolin. This is due to the production of the La₂O₃–SiO₂ system already in solution and the blocking of silanol groups on the surface of silicon oxide. A significant increase in specific adsorption at pK_a 9.2 for both the kaolin and tetraethoxysilane samples proves the existence of La³⁺ metal ions and OH^– hydroxyl groups on the surface of silicon oxide.