Glass Physics and Chemistry最新文献

Xerogels and powders in the ZrO₂−Y₂O₃−Yb₂O₃ system are synthesized by coprecipitation of hydroxides in a laboratory setup and in a micro-vortex jet apparatus with counterswirling flows. The effects of the initial zirconium oxynitrate concentration and synthesis conditions on the physicochemical properties of the obtained materials are revealed. Ceramics based on t-ZrO₂ are obtained, exhibiting high microhardness, elastic modulus, and coefficients of linear thermal expansion (CLTE), which makes them promising for use as thermal insulation materials.

Geopolymer matrices based on alkali-activated natural aluminosilicates—kaolinite and clinoptilolite—are obtained. Their potential application for the immobilization of radionuclides is studied using Cs⁺ as an example. The optimal kaolinite/clinoptilolite ratios are determined, enabling the production of matrices with compressive strengths of up to 40 MPa and an immobilized cesium content of up to 1.5 wt % (as Cs₂O). The leaching rate of Cs⁺ from the geopolymer matrix is estimated in aqueous and alkaline environments. It is shown that geopolymer matrices are promising materials for the disposal of radioactive waste.

The effect of replacing silicon dioxide with a combination of aluminum and barium oxides in alkali-free silicate glasses is studied. The concentration of silicon dioxide in the series of glasses studied decreases from 49 to 34 mol %, while that of aluminum oxide and barium oxide increases from 4 to 9 and from 15 to 24 mol %, respectively. The content of the remaining oxides remains constant. The elemental and phase composition of the glasses is determined using inductively coupled plasma spectroscopy, energy-dispersive spectroscopy, X-ray diffraction, and scanning electron microscopy; the thermal properties are determined using differential scanning calorimetry and dilatometry; and the structure of the glasses is determined using Raman spectroscopy and infrared spectroscopy. It is shown that replacing silicon dioxide with a mixture of aluminum and barium oxides does not lead to a noticeable change in the structure of the glass or its structure-sensitive properties, such as the coefficient of linear thermal expansion (CLTE) and glass transition temperature T_g, as well as the transition to a fluid state temperature T_f. During heat treatment of glass, crystals precipitate depending on the composition and temperature: coesite, celsian, or double barium–calcium silicate.

The recently identified intriguing room-temperature multiferroic photoactive material KBiFe₂O₅ (KBFO) has potential uses in visible light-induced photocatalysis for environmental clean-up and photovoltaics for solar energy harvesting. We adopted the addition of polymeric surfactant polyvinylpyrrolidone (PVP) via sol-gel route, to improve the magnetic and visible light induced photocatalytic properties of KBFO, and thus obtained results are reporting here. The addition of PVP had significant influence on the particle size and the morphology of the synthesized KBFO polycrystalline samples. KBFO synthesized via addition of PVP showed four time’s higher magnetization value and double rate constant when compared to KBFO obtained without addition of PVP. The improved in magnetic and photocatalytic properties of KBFO is attributed to larger surface area and regular shaped morphology. The obtained results provide deeper understanding of relation between the material processing, morphology and its influence on the physical properties.

It is shown that twisting the channels of the honeycomb catalyst carrier can significantly increase its activity in carbon monoxide oxidation. The primary catalyst support based on α-Al₂O₃ is fabricated using a 3D-printing technology developed by the authors. A catalytically active layer is formed on the surface of the primary support by impregnation to incipient wetness using a coating suspension containing copper, cobalt, and cerium oxides; finely dispersed γ-Al₂O₃; boehmite; nitric acid; and water.

Xerogels are obtained in ZrO₂–Yb₂O₃–CeO₂ system by the hydroxide co-precipitation method. Their physicochemical properties are studied. The effect of composition on phase formation in powders and ceramics based on zirconium dioxide is revealed. Ceramic materials based on c-ZrO₂ are obtained that exhibit high specific electrical conductivity, making them promising for use as electrolytes in solid oxide fuel cells (SOFC).

This paper presents the results of a study obtained using the developed quantitative method for determining the crystallization resistance of quartz glass produced from quartz concentrates derived from natural quartz raw materials of different origins. It is shown that the onset temperature and kinetics of quartz glass crystallization depend not only on the purity of the quartz concentrates from which the quartz glass is melted but also on the genesis of the original quartz. Glasses obtained from superquartzites of the Eastern Sayan exhibit a higher resistance to crystallization than glasses produced from granulated quartz of the Kyshtym deposit (Urals), which indicates a significant advantage of quartzites in the production of heat-resistant quartz ceramics and crucibles for growing silicon.

¹¹⁹Sn nuclear gamma-resonance spectroscopy (¹¹⁹Sn NGRS), X-ray diffraction (XRD) and long-wavelength IR spectroscopy, as well as measurements of density, microhardness, and electrical conductivity parameters of quenched samples, were used to study step-by-step kinetically coupled structural–chemical and phase transformations during bulk isothermal crystallization of As₂Se₃Sn_0.40 (7.4 at % Sn) semiconductor glass at 240°C, leading to the formation of electrically conductive, chemically resistant glass–ceramics. Analysis using the generalized Kolmogorov–Avrami equation showed that, homogeneous nucleation and two-dimensional growth of finely dispersed SnSe and SnSe₂ crystals occur at the first stage of reconstructive crystallization at a temperature of 240°C, with the predominance of the SnSe phase, which initiates heterogeneous nucleation and two-dimensional growth of crystals of the main As₂Se₃ phase at the second stage. Changes in vibrational spectra and electrical conductivity parameters at different stages of bulk crystallization of As₂Se₃Sn_0.40 glass at 240°C are discussed. The kinetics of isothermal crystallization of glass at the first stage are also studied using continuous conductometry at temperatures of 240 and 260°C.

Currently, silver nanoparticles remain one of the most prevalent substrates for surface-enhanced Raman spectroscopy (SERS), owing to their high enhancement efficiency across a broad range of excitation wavelengths. However, their practical application is limited by inherent drawbacks, including poor biocompatibility and a propensity for oxidation. To address these limitations, this study investigates the efficacy and stability of bimetallic alloy nanoparticles as alternative SERS substrates. Spherical silver–gold (Ag–Au) and gold–copper (Au–Cu) alloy nanoparticles were synthesized via laser ablation in aqueous media, a versatile technique chosen for its applicability to various compositions, unlike many conventional methods that are often material-specific. Among the synthesized alloys, the Ag–Au (2 : 1) composition demonstrated the highest SERS activity, exhibiting an enhancement factor only 1.5 times lower than that of pure silver nanoparticles. Furthermore, the Au–Cu (1 : 1) sample displayed greater enhancement efficiency at an excitation wavelength of 488 nm compared to monometallic gold or copper nanoparticles, while concurrently demonstrating superior stability. These findings indicate that bimetallic alloy nanoparticles are promising candidates for SERS applications, with their performance potentially surpassing that of their constituent pure metals.

The influence of hydrothermal synthesis conditions on the porous textural characteristics and morphology of saponite NaMg₃[AlSi₃O₁₀](OH)₂·nH₂O is studied. Saponite is synthesized by hydrothermal crystallization from a gel of the corresponding composition in the temperature range from 200 to 350°C, the duration of synthesis ranges from 2 to 12 days, at a pressure of 700 atm. The obtained samples are studied using X-ray diffraction, low-temperature nitrogen adsorption, and scanning electron microscopy. It is established that varying the synthesis conditions makes it possible to obtain saponite with different degrees of crystallinity and porosity. The morphology of the particles is also determined by the synthesis conditions and can be spongy or lamellar. The possibility of forming a spongy structure using saponite is demonstrated for the first time. The specific surface area can vary in the range from 170 to 690 m²/g.