Glass Physics and Chemistry最新文献

In this paper, we studied the Na₂O–CaO–B₂O₃–TeO₂–Sm₂O₃ (labeled as NCBT-Sm) for the physical, optical, and luminescence properties of the NCBT-Sm glasses. The XRD study confirmed the amorphous nature of the glass. The density and molar volume increase with increasing concentration of TeO₂. We found four emission peaks located at 562, 597, 644 and 706 nm corresponding to ⁴G_5/2 → ⁶H_5/2, ⁴G_5/2 → ⁶H_7/2, ⁴G_5/2 → ⁶H_9/2 and ⁴G_5/2 → ⁶H_{1 1/2} transitions respectively. The emission and absorption spectra were analyzed using the Judd–Ofelt theory to calculate various spectroscopic parameters, such as emission cross-section, radiative transition probability, branching ratios, and stimulated emission cross-section. The color coordinates of all the glass samples lie in the orange region of the Commission International de l’Eclairage (CIE) diagram. The results obtained in the present work show that these glasses may be a potential candidate for LED applications.

A two-layer superhydrophobic coating consisting of a heating and water-repellent layer is obtained. The heating layer, which is a percolation network of carbon nanotubes (CNTs), is reinforced with a polymer to improve surface adhesion, strength, and wear resistance. Epoxy resin is used as a reinforcing polymer. Various methods of organizing a heating layer from CNTs with a reinforcing polymer are considered, and the best ones are identified for creating a heating or antistatic surface. The influence of the concentration of CNTs in the polymer on the strength of the composite is studied. Different methods of introducing nanotubes in the polymer are compared to achieve the best deagglomeration of nanoparticles. The effects of functionalization of nanotubes are tested, and an increase in the coating strength with a slight increase in conductivity is revealed. The optimal concentration of Taunit-M carbon nanoparticles for strengthening ED-20 epoxy resin is found to be 0.07% for nonfunctionalized nanotubes and 0.5–0.6% for particles with –CONH₂ in groups. It is possible to achieve a superhydrophobic state of the surface: the contact angle of wetting is 152.3 ± 0.7 and the angle of the beginning of the sliding of the droplet is 1.6 ± 0.9.

Indian nuclear industries emphasize on metal fuel which shows significant advantages over ceramic fuels in fast reactor fuel cycles, where sodium is used as bonding material. The sodium discharged from rejected sodium bonded metal fuel pins is blended with uranium and plutonium metals labelled as contaminated sodium. This contaminated sodium is converted to borosilicate glass with the addition of suitable glass formers and modifiers. Pristine borosilicate glass of known composition and doped glasses were prepared with fixed Na/Si ratio by addition of (i) U₃O₈ (5 wt %) and (ii) oxides of U, Ce, Nd, and Gd (together 5 wt %) labelled as BSGU and BSGURE respectively. Thermo-physical properties of these glasses are favourable towards safe disposal however, it is essential to evaluate aqueous alteration named as chemical durability (at 363 K) before using contaminated sodium. Surface morphology and chemical durability of pristine BSG were evaluated and compared with doped BSGs. The normalized leach rate for seven days was found to be 1.8 × 10^–4, 5.5 × 10^–5, and 4.2 × 10^–5 g cm^–2 day^–1 for pristine BSG, BSGU, and BSGURE respectively. The enhancement of chemical durability on doped glasses is due to addition of dopants.

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.