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Composite sol-gel materials of the MgO–Al2O3–ZrO2–SiO2 system were synthesized and the processes of their thermal evolution and crystallization were studied. Application of sol-gel compositions of the MgO–Al2O3–ZrO2–SiO2 system to the surface of quartz ceramics leads to a significant increase in the mechanical strength of the material. The processes of thermal evolution of the sol-gel composition were studied using IR spectroscopy, X-ray diffraction, electron microscopy, and energy dispersive analysis. It was shown that the formation of the oxide composite structure of materials begins at the stage of wet gels. Treatment of quartz ceramics with composite sols followed by drying and heat treatment up to 1200°C results in modification of the surface layers of the material, which makes it possible to increase the mechanical strength of the material by more than 20%. Sol-gel modifying compositions, upon drying and subsequent heat treatment, form polycrystalline structures bonded to quartz ceramic particles and consisting of various oxide crystals. [ABSTRACT FROM AUTHOR]

In the work, the MgO–Al2O3–ZrO2–SiO2 coatings on the surface of quartz ceramics were prepared by sol-gel method. The synthesized materials were examined by X-ray phase and electron microscopic analyses. It is shown that composite gels retain an amorphous structure after thermal treatment at 600°C, and the formation and subsequent transformation of various oxide crystal phases is observed after calcination at temperatures above 900°C. The behavior of the thermal evolution of the structure of the obtained gels is generally similar to the course of structural changes occurring during glasses crystallization. [ABSTRACT FROM AUTHOR]

The effect of γ-irradiation on optical losses at a wavelength of 1.31 to 1.55 μm in multimode quartz fibers with a core doped with 20 mol % GeO2 is considered. Germanium oxygen-deficient centers in the core material are the main reason for the low radiation resistance of such optical fibers. The elimination of these defects in the MCVD preform technology reduces the radiation-induced attenuation in germanosilicate light guides to a level close to that of light guides with a pure quartz glass core. The increase in optical losses induced by radiation in the studied fibers is largely due to the contribution of Rayleigh scattering. [ABSTRACT FROM AUTHOR]

Photoactive ZnO–SnO2–Ag(AgCl) nanomaterials capable of generating chemically active single oxygen under action of UV and blue light are synthesized using a polymer–salt method. The structure and properties of these materials are studied by optical and luminescence spectroscopy, as well as by X-ray diffraction and electron microscopy analyses. It is found that the structure of the ZnO–SnO2–Ag(AgCl) materials consists of hexagonal ZnO crystals with a wurtzite structure, tetragonal SnO2 nanocrystals with a rutile structure, and Ag and AgCl crystals. The materials consist mainly of nanoparticles 50–60 nm is size. They are characterized by the ability to generate chemically active singlet oxygen and have antibacterial properties against both Gram-positive and Gram-negative bacteria. An increase in the concentration of silver in the materials enhances their antibacterial properties. [ABSTRACT FROM AUTHOR]

The problems of manufacturing nanoscale Gd2O3:Nd3+ phosphors using the liquid polymer-salt method have been considered. Within the framework of this method, the dual role of polyvinylpyrrolidone (PVP) as an organic solvent in the synthesis process has been determined. On the one hand, it stabilizes the formation of Gd2O3 crystals, preventing their uncontrolled growth and agglomeration, and on the other, it serves as a fuel during decomposition (combustion), contributing to an increase in the reaction temperature and thereby influencing the structural and emission properties of phosphors. It has been shown that successive drying of the initial homogeneous solution containing gadolinium and neodymium salts, as well as PVP, at room temperature for 24 h and heat treatment at 1000°C for 2 h make it possible to obtain high-luminescent near-infrared phosphors Gd2O3:Nd3+, whose crystals are characterized mainly by a cubic structure and an average size of about 40 nm. It has been experimentally confirmed that the developed method is suitable for modifying hollow-core antiresonant optical fibers made of silica glass with thin-film coatings based on the synthesized material and does not cause structural and phase transformation of the formed Gd2O3 crystals. It has been found out that the emission spectra of the nanoscale Gd2O3:Nd3+ phosphors obtained by the polymer-salt method at temperatures of 550 and 1000°C are identical, namely: (1) the shape of the luminescence peaks is the same for both specified heat treatment regimes regardless of intensity, (2) the main lum-inescence peak is located near 1064 nm wavelength and corresponds to the electron transition 4F3/2–4I11/2, and (3) additional luminescence peaks are located near 900 and 1340 nm wavelengths and correspond to the 4F3/2–4I9/2 and 4F3/2–4I13/2 electron transitions, respectively. [ABSTRACT FROM AUTHOR]

This paper describes the low-temperature polymer-salt synthesis of ZnO–Ag nanopowders and presents the results of studying their structure, morphology, and properties. The methods of X-ray phase analysis and electron microscopy are used to study the structure and morphology of materials. It is found that the resulting nanopowders consist of nanoparticles of about 30 nm. The experiments show that the resulting nanopowders have antibacterial activity against both gram-positive and gram-negative bacteria. [ABSTRACT FROM AUTHOR]