Glass Physics and Chemistry最新文献

This paper presents a method for determining the degree of cristobalitization of synthetic silicon dioxide grains of special purity, obtained from tetraethoxysilane using sol-gel technology, through IR Fourier spectroscopy with the use of an attenuated total internal reflection attachment. The results of measuring the degree of cristobalitization of synthetic silicon dioxide grains of special purity produced by Perm Scientific and Production Instrument-Making Company are presented. The linear dependence of the degree of cristobalitization on the grain size of cristobalite grits is shown.

The morphology, structural features, and optical properties of zinc oxide films of various thicknesses, synthesized by thermal oxidation in an air atmosphere of polycrystalline zinc layers with a thickness of 10, 20, 40, 50, 60, and 80 nm, obtained by magnetron sputtering on glass substrates, are studied. The influence of the thickness of the initial layers and the size of zinc crystals on the characteristics of the crystal structure and properties of the resulting zinc oxide films, as well as the patterns of the approximation of its optical band gap and crystal lattice parameters to the values for bulk zinc oxide (ZnO) crystals with increasing film thickness, are analyzed.

The aim of this work is to investigate the underlying mechanisms by which the deposition current density affects the structural, mechanical and electrochemical properties of Cu–Ni–W coatings electrodeposited via direct current method. X-ray diffraction investigation indicated the formation of face-centered cubic structure with the presence of nickel–tungsten phases. Microstructural analysis revealed that coatings were uniform and compact structure without any obvious defects. Cu–Ni–W thin films were thoroughly evaluated for their mechanical, structural, and corrosion resistance properties. Nanoindentation tests were carried out to calculate the mechanical properties, which include stiffness, elastic modulus, and nanohardness. The elastic modulus of 102 GPa and the hardness value of 5.4 GPa were obtained for the film deposited at –50 mA/cm². Examination of the electrochemical Tafel plots indicated that the films deposited at higher current densities exhibited improved resistance to corrosion. The variation of I_corr values from 2.12 to 1.86 µA/cm² implied that these films have a lower susceptibility to corrosion.

This paper presents experimental results on obtaining bulk samples of Ti–Al–B₄C materials by using the method of cold gas-dynamic spraying from a mixture of monopowders in a system of separately operating dispensers, followed by heat treatment. The parameters allowing the development of effective methods for creating products by the additive method are studied and tested. It is shown practically and theoretically that metal plastic particles in the composition of a prototype blank formed by the method of cold gas-dynamic spraying can act as a sacrificial component for the formation of high-temperature borides and titanium carbides, which after heat treatment leads to strengthening of the bulk composite material in the absence of significant shrinkage, maintaining low porosity and continuity of the structure.

The effects of pH and temperature during synthesis on the pore structure and morphology of porous silica were investigated using inexpensive polyethylene glycol as a template. At a synthesis temperature of 20°C, the porous silica obtained at pH 4.0–6.0 mainly exhibited micropores, while those obtained at pH 7.0 and 8.0 developed both micropores and mesopores. At pH 7, increasing the synthesis temperature resulted in the formation of more mesopores and the production of smaller spherical porous silica particles. At pH 7 and a temperature of 60°C, spherical porous silica with a specific surface area of 654.6 m²/g and an average particle size of 0.8 µm was obtained.

Germanium is a relatively high-atomic-number material and has relatively high neutron capture cross-section values. By taking advantage of these properties, the gamma-ray and neutron shielding parameters and mechanical properties of zinc–borate–lithium glasses were determined by infusing GeO₂ concentrations from 1 to 4 mol %. The photon interaction parameters such as mass attenuation coefficient, half and tenth value layer, mean free path, effective atomic number, buildup factors, and neutron interaction parameters such as fast neutron removal cross sections were estimated using Phy-X/PSD software. It is found that effective atomic number and equivalent atomic number values increase with an increase in GeO₂ concentrations in the selected glasses, and mean free path values are lower than ordinary concrete and RS-253-G18. The effectiveness of shielding parameters such as buildup factors shows a broader distribution at lower mean free path and a narrower distribution at higher mean free path, peaking at 0.5 MeV of gamma energy. The neutron interaction parameters, such as fast neutron removal cross section values, decrease with an increase in the concentration of GeO₂ in the selected glass. The mechanical parameters, such as the elastic moduli of selected glasses, show a decrease in value with an increase in mol % of GeO₂. The relationship between elastic moduli and fast neutron removal cross section is observed for the first time.

Using liquid-phase methods of coprecipitation of hydroxides and cocrystallization of nitrate salts, highly dispersed powders of the (CeO₂)_1 – x(Dy₂O₃)_x (x = 0.05, 0.10, 0.15, 0.20) composition are synthesized. On their basis, ceramics, which are cubic solid solutions of the fluorite type with a coherent scattering region (CSR) of ~90 nm (1300°С) with open porosity in the range of 2–14% and apparent density of 6–7 g/cm³, are obtained. The influence of methods of synthesis and sintering additives on the physicochemical and electrophysical properties of ceramics is studied. It is established that the obtained ceramics have a predominantly ionic type of electrical conductivity (ion transport numbers t_i = 0.78–0.96 in the range of 300–700°С). Electrical conductivity in solid solutions is realized by the vacancy mechanism and reaches the value of σ_700°С = 0.43 × 10^–2 S/cm. Based on their physical and chemical properties (density, open porosity, type and mechanism of specific electrical conductivity), the obtained ceramic materials are promising as solid oxide electrolytes for medium-temperature fuel cells.

Thulium/holmium co-doped bismuth borotellurite glass have been prepared using melt quenching technique. All the prepared glasses characterized using X-ray Diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy at room temperature. There is no distinct peak in the XRD patterns over the observed range of 10° to 90°, indicating that all prepared glasses are amorphous. FTIR study reveals that the glass structure is composed of by TeO₃, TeO₄, BO₄, BO₃, BiO₃, and BiO₆ structural units. According to the bridging and non-bridging oxygen, the impact of the Ho₂O₃ addition was demonstrated by the calculated ratio of BO₄ to TeO₄ in the structural network. Bridging oxygen formation was proposed by the calculated ratio of BO₄ to TeO₄ increasing in along with the increase in Ho₂O₃ concentration (x = 0 to 1.0 mol %). Additionally, the declining ratio of BO₄ to TeO₄ (x = 1.5 to 2.5 mol %) explains the formation of non-bridging oxygen.

The synthesis of lithium lead borosilicate bismuth vanadate glasses with varying Tl₂O₃ concentrations (between 0 to 5.0 mol %) was achieved through the implementation of the melt quenching technique. A comprehensive analysis has been conducted to examine the electrical and dielectric properties over a broad spectrum of frequencies (10²–10⁶ Hz) and temperatures (303–573 K). According to the findings of conductivity studies, mixed conduction (both electronic and ionic) occurs in the produced glasses. As the concentration of Tl₂O₃ increases in the base glass, the dielectric properties, including dielectric loss, dielectric constant, and ac conduction, exhibit a decreasing trend. An increasing number of V⁵⁺ ions has been identified as being involved in the formation of networks near crystal structures of VO₅. The quantitative study of ac conductivity and dielectric property data revealed that increasing the concentration of Tl₂O₃ in the glass network increases the insulating character of the glass. In the glass structure, the migration of thallium ions to tetrahedral coordination from octahedral coordination occurs, accompanied by a de-clustering effect of these ions.

Production of porcelain tiles has been increasing rapidly with the increasing demand for both technological and aesthetic features for years. Especially tiles produced with digital applications attract much more attention. Digital glazes (glass-ceramic) can be matte or glossy features. In this study, the effect of the SiO₂/Al₂O₃ ratio on technological properties was examined by keeping other oxide ratios constant in matte glaze compositions for digital applications. Seven glass ceramic compositions were prepared and trials were carried out under industrial conditions. The microstructure was measured with the use of a SEM, phases were determined by XRD, and sintering behavior was characterized by heating microscopy. The color and gloss of glazes were measured using a spectrophotometer and a gloss meter. As the SiO₂/Al₂O₃ ratio decreased, especially the amount of anorthite crystal increased, which resulted in the formation of more matte glaze surfaces. Glaze whiteness and hardness increased due to the crystal formation. As the amount of Al₂O₃ increased, the softening and melting temperature points of the glazes also increased. It has been determined that surface properties can be modified for digital applications by changing the SiO₂/Al₂O₃ ratio.