Glass Physics and Chemistry最新文献

The porcelain insulator was fabricated using a sintering process with raw materials from Algeria, consisting of 45 wt % kaolin, 30 wt % feldspar, and 25 wt % quartz. ZrO₂ nanoparticles were incorporated into the raw materials in varying proportions. The powders were then milled and pressed into pellets with a diameter of 20 mm and a thickness of 2 mm. The green samples were sintered at 1200°C for 2 h, with a heating rate of 10°C/min. The influence of ZrO₂ nanoparticles on the physical and structural properties of the porcelain insulator was thoroughly examined. X-ray diffraction (XRD) analysis revealed that kaolin primarily consists of kaolinite minerals, with sufficient SiO₂ and Al₂O₃ contents, contributing to reasonable plasticity. The sintered samples exhibited key mineral phases, including mullite, quartz, and anorthite. The porcelain insulator, formulated with 45 wt % kaolin (30 wt % kaolin KT2 + 15 wt % kaolin DD3), 30 wt % feldspar, 25 wt % quartz, and 5 wt % ZrO₂ demonstrated high bulk density and minimal linear shrinkage. The addition of ZrO₂ nanoparticles notably improved the densification and enhanced the overall physical properties of the porcelain insulators.

The formation conditions and processes of the complex aluminate Dy₂SrAl₂O₇ are studied. It is established that solid-state synthesis of Dy₂SrAl₂O₇ proceeds through the formation of strontium aluminate SrAl₂O₄. At temperatures above 1200°C, active interaction begins between the intermediate compound SrAl₂O₄ and Dy₂O₃, associated with the transition of the two-dimensional nonautonomous phase SrAl₂O₄ into a liquid-like state. The thermal stability of Dy₂SrAl₂O₇ up to the temperature of incongruent melting at 1750°С is characterized for the first time. The coefficient of thermal expansion (CTE) of Dy₂SrAl₂O₇ is experimentally determined to be 8 × 10^–6 K^–1 in the temperature range of 400–1300°С. It is shown that active sintering of Dy₂SrAl₂O₇ begins at 1300°С. A change in the type of melting diagrams is shown in the Ln₂SrAl₂O₇ series, where Ln = La → Gd → Dy, Ho. A decrease in both melting temperatures and CTE values is revealed across the Ln₂SrAl₂O₇ series (Ln = La → Ho).

Bismuth-containing composite materials (CMs) with variable silver content are synthesized by impregnating porous silicate glass matrices in acidified aqueous-salt solutions of Bi(NO₃)₃·5H₂O in the presence of AgNO₃ with their subsequent heat treatment at 650 or 870°C and their luminescent properties are studied. The synthesized materials exhibit photoluminescence in a wide spectral range (220–900 nm) due to the presence of various active centers (Bi³⁺, Bi²⁺, Bi⁺ ions, bismuth dimers, bismuth active centers (BACs) associated with silicon, Ag⁺ ions, silver nanoclusters, silicon oxygen-deficient centers, =Si⁰ centers).

Multiferroic composites consisting of barium–strontium titanate and nickel ferrite have been successfully synthesized by low-temperature sintering in the form of thick films on a dielectric substrate. The crystal structure and composition of the composites were studied by X-ray diffraction and electron microscopy. The electrical and magnetic characteristics of the obtained composites were studied at microwaves. The studied samples demonstrate a dielectric permittivity from 80 to 160 and dielectric losses from 0.05 to 0.1 at a frequency of 1 GHz, as well as the ability to control the magnetization of the composite within 30% by changing the magnetization field in the range 0–2000 Oe. This is the first successful attempt to synthesize a ferroelectric/ferrite composite with both low microwave losses and magnetization controllability.

Highly dispersed mesoporous powders of the composition Gd_1 – xSr_xCo_0.5O_3 – δ (x = 0.1, 0.15, 0.2, 0.25), Gd_0.4Sr_0.1Ni_0.5O_3 – δ, and Gd_0.125La_0.125Sr_0.25Co_0.5O_3 – δ are synthesized using the method of the cocrystallization of nitrate salts. Ceramic nanomaterials of the given composition with a CSR of ~49–62 nm (1200°С), open porosity of 17–42%, and apparent density of 5–7 g/cm³ are obtained based on them. Nanopowders and ceramics in the range of 600–1200°C have a tetragonal and orthorhombic structure of the perovskite type in the Gd₂O₃‒SrO‒Co₂O_3 – δ system. It is established that in order to obtain the optimal characteristics of density and porous structure of ceramics, combined additives of polyvinyl alcohol (PVA) are required in combination with aluminum hydroxide Al(OH)₃, acting as a pore-forming and sintering additive. The solid solutions have mixed electron-ionic conductivity with transport numbers t_e = 0.92–0.99 and t_i = 0.08–0.01. Due to their physical, chemical, and electrophysical properties associated with the structural features of solid solutions, ceramic materials obtained based on them are promising for use as solid oxide cathodes for medium-temperature fuel cells.

The increasing depletion of natural sand resources and the urgent need for sustainable construction materials underscore the significance of this study, which investigates the incorporation of waste glass sand (WGS) into concrete as an eco-friendly and cost-effective alternative. The challenge lies in achieving a balance between the structural performance of concrete and the economic and environmental advantages of utilizing recycled materials. To address this issue, river sand was partially replaced with WGS at varying proportions (0–60 wt %), and the resulting waste glass sand concrete (WGSC) was assessed for workability (slump), mechanical properties (compressive strength and elastic modulus), and economic viability (functional, cost, and value coefficients). The findings indicated that higher WGS replacement rates enhanced flowability while maintaining a stable elastic modulus. Compressive strength, measured in both cubic and prismatic forms, initially increased before declining at higher replacement levels. The functional coefficient increased initially but then decreased, whereas the cost coefficient consistently decreased. The value coefficient displayed a nonlinear trend, initially increasing, then decreasing, and subsequently rising again. A linear regression model revealed a strong correlation between the value coefficient and the WGS replacement rate. Importantly, WGS not only reduced material costs but also mitigated functional deficiencies, demonstrating its potential as a sustainable partial substitute for river sand in concrete.

Glass of the composition (mol %, as synthesized) 6Na₂O·18B₂O₃·70SiO₂·6Ni₂O₃, heat-treated at 550°C for 96 h is studied using scanning electron microscopy, and its chemical stability to an aqueous 3 M HCl solution is also studied. It is established that this glass has an interconnected phase-separated structure. The general nature of its leaching process is controlled by diffusion. Compared to iron-containing glass of a similar composition, the extraction rate of Na₂O and B₂O₃ is reduced by a factor of 2. Nickel oxide is predominantly found in the chemically unstable glass phase, most of it passing into the leaching solution. The suitability of nickel-containing phase-separated glass for producing porous glass with through porosity (~30%) is demonstrated.

Development of value-added utilization method for rice husk char (RHC) generated from rice husk gasification power plants is desirable. Amorphous porous silica was obtained by simple calcination of RHC; however, acid treatment prior to calcination improved its purity and increased its specific surface area. In the adsorption of Methylene Blue (MB) by the prepared porous silica, acid treatment enhanced its adsorption capacity and suppressed the increase in the pH of the MB solution. According to the Langmuir adsorption isotherm, the maximum adsorption capacity of the porous silica obtained by calcining acid-treated RHC at 500°C was 26.81 mg/g, which was 3.5 times higher than that of the porous silica obtained by calcining RHC at 500°C without acid treatment.

A new composite material based on thermoplastic elastomer is developed for the 3D printing of neutron-absorbing products. It is shown that the use of thermoplastic elastomer in the development of material for the 3D printing of products allows for the required neutron absorption properties to be achieved, significantly increasing the technological effectiveness of the composition and preserving its applicability in additive technologies. The concentration of boron nitride in the composite, which allows achieving the effect of absorption of neutron radiation by the material of 2.4 Å/1.2 Å (3/1) to a penetration depth of 1.4 mm, while maintaining its physical and mechanical properties, was 25%. The physical and mechanical characteristics of the developed material are not inferior to unfilled plastics: tensile strength σ_max = 8.1 MPa and tear resistance T_s = 76 N/m.

Three borosilicates with the general formula of REE₃BSi₂O₁₀ (REE = Nd, Eu, Gd) were obtained by the high-temperature solid-state synthesis and studied by powder high-temperature X-ray diffraction (HTXRD) in the temperature range from 30 up to 1050°C. The HTXRD study showed that these borosilicates (orthorhombic, Pbca space group) have similar, nearly isotropic thermal expansion in the whole temperature range; the average coefficients of thermal expansion (CTE) were: 〈α_a〉 = 9.6, 〈α_b〉 = 8.3 and 〈α_c〉 = 8.7 × 10^–6°С^–1, with (α_max – α_min) ≤ 1.2 × 10^–6°С^–1. The average volume CTE insignificantly decreases with increasing the cation size from 27.2 for Eu and 27.0 for Gd down to 25.8 × 10^–6°С^–1 for Nd compound while the unit cell volume increases with increasing the REE cation radii in the REE₃BSi₂O₁₀ series.