Glass Physics and Chemistry最新文献

Information about new cesium-containing quartzoid glasses (QGs) obtained as a result of the heat treatment of high-silica porous glasses (PGs) impregnated with aqueous solutions of CsNO₃ is presented. Quartzoid glasses have been studied by SEM, X-ray diffraction, flame photometry, and energy-dispersive X‑ray spectroscopy. It has been established that the total content of cesium in the synthesized QGs increases with an increase in the concentration of the impregnating solution of cesium nitrate and an increase in the impregnation time of PGs for the selected synthesis conditions.

The features of the formation of a hidden lead-silicate insulating layer in silicon substrates are considered. To do this, ions of molecular oxygen and lead are sequentially implanted into them in an atomic ratio of 75 : 1 then annealing is carried out at a temperature of 1150°C in an environment of dry oxygen. The distribution of the implanted ions in the experimental samples is recorded by the method of secondary ion mass spectrometry. It is shown that the latent insulator is formed in the process of the spinodal decomposition of a solid solution of SiO_x–PbO_x in the form of a three-layer structure. Its middle part is silicon dioxide doped with lead ions and the side parts consist of a lead-silicate phase. A relaxation diffusion model is proposed to analyze the distribution profile of lead.

A series of Titanium-doped mesoporous bioactive glass with different Si-Ca ratios (MBG-Ti-1– MBG-Ti-5) were prepared by the sol-gel method. These materials were used to adsorb Norfloxacin (NOR) pollutant from aqueous solution. The morphology, microstructure and chemical properties of MBG-Ti-3 were characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The N₂ adsorption-desorption isotherm and pore size distribution of MBG-Ti-3 were investigated by the Brunauer–Emmett–Teller (BET) method and Barret–Joyner–Halenda (BJH) method. The specific surface of MBG-Ti-3 was 126.68 m²/g and the pore size was about 15 nm. The effect of time, initial concentration, pH and temperature on the adsorption of NOR were investigated. The maximum adsorption efficiency was 68% at 30°C, pH 8.0. Moreover, adsorption of NOR onto MBG-Ti-3 could be well fitted with the pseudo-first-order model and the pseudo-second-order model. Furthermore, adsorption was spontaneous, exothermic process of reduced entropy by analyzing thermodynamic model. Through the analysis of adsorption model, plausible adsorption mechanism was proposed. MBG-Ti-3 exhibited better adsorption efficiency after recycle 3 times. Additionally, bioactive glass was eco-friendly attribute to biological suitability which could not cause secondly pollution for aquatic environment. As an environmentally friendly adsorbent, Titanium-doped mesoporous bioactive glass showed promising potential application in NOR antibiotics removal from aquatic environment.

In this paper, the transition metal oxoborate warwickite (Fe²⁺,Mg)Fe³⁺(BO₃)O is studied for the first time by low- and high-temperature X-ray diffraction in the temperature range from 93 to 513 K. The sharply anisotropic nature of its thermal expansion is revealed. A structural interpretation of the expansion mechanism is given both in terms of the contribution of cationic and oxocentered polyhedra.

Praseodymium incorporated Na₂O–ZnO–TeO₂ (NZT) glass materials were prepared through usual melt quenching technique. The temperature of glass transition and the melting point were obtained by using thermal analyses. The amorphous and ionic nature of the prepared samples was obtained from the recorded X-ray diffraction pattern and FTIR spectra respectively. The optical band gap energy was calculated using UV-Vis absorption spectra and was observed to be decreased from 2.86 to 2.46 eV due to the increasing concentration of Pr³⁺ ions. The peaks of absorption spectra were found. The intense emission was observed from the fluorescence measurement for the emission band of Pr³⁺ doped glass materials. The doping of higher concentrations of Pr³⁺ ions enhanced the intensity of the emission peaks. The CIE chromaticity coordinates were estimated from fluorescence spectra for pure and Pr³⁺ doped glass samples to know the suitability of laser emission of these glass samples. The dielectric constant of the glass materials was observed to be independent of frequency in the large range of frequency (500 Hz to 2 MHz). The variation of conductivity of the glasses was exposed the Arrhenius mechanism of conduction with the temperature.

This paper analyzes the experimental and theoretical studies of the problem of a diffuse phase transition (PTC) in a composite material xPbSe⋅(1 – x)PbSeO₃, in which x varies from 0 to 1. The decrease in stability in the virtual cubic phase of lead selenide (PbSe) is achieved by oxidizing it with atmospheric oxygen and forming a ferroelectric disordered monoclinic phase of lead selenite (PbSeO₃). The mechanism of lead selenide oxidation by air oxygen is studied by X-ray diffractometry, optical reflection in the infrared region of the spectrum, X-ray emission analysis (the chemical shift method), nuclear magnetic resonance, studies of AC and DC conductivity, differential scanning calorimetry, and other methods. The reason for the smearing of the phase transition in the xPbSe⋅(1 – x)PbSeO₃ composite, in which x varies from 0 to 1, is analyzed based on the previously obtained experimental results of its detection.

Nickel-zinc ferrites, which have pronounced ferrimagnetic and semiconductor properties, can be used as promising magnetically controlled photocatalysts for the purification of aqueous media from organic pollutants. The value of the specific surface area largely affects the photocatalytic properties of the material; therefore, the possibility of its control and variation at the stage of synthesis is of great scientific and technical interest. In this study, nanocrystalline ferrite of the Zn_0.5Ni_0.5Fe₂O₄ composition is obtained under conditions of solution combustion using various types of organic fuel as the main factor affecting the formation of the specific surface area, and subsequent heat treatment in air at a temperature of 500°C for 2 h. The crystal structure, chemical composition, and morphology of Zn_0.5Ni_0.5Fe₂O₄ are studied by methods of X‑ray phase analysis, X-ray spectral microanalysis, and scanning electron microscopy. The values of the specific surface area of the synthesized nanopowders are calculated based on the method of liquid-phase adsorption from a Methylene Blue solution and the low-temperature adsorption-desorption of nitrogen. The results of the X‑ray phase analysis show that a single-phase nanocrystalline product with a spinel structure is formed, where the average crystallite size varies within 11–23 nm and is inversely related to the value of the specific surface area, respectively, after the reaction with succinic acid (39.1 m²/g) and with glycine (20.2 m²/g). It is established that the choice of the fuel largely affects the formation of nanocrystals and the specific surface area of the samples, and the approach used makes it possible to control its values.

A model is proposed that makes it possible to calculate the temperature dependence of the microhardness of glass over the entire temperature range from the softening temperature to absolute zero. The calculation uses the temperature dependence of the glass enthalpy and the value of its microhardness at the glass transition temperature. The proposed model is tested on the example of glassy selenium. For this, the temperature dependence of the microhardness of selenium on the softening temperature up to 100 K, which is 50 K below its Debye temperature, is measured. Thus, a relationship is established between the strength and thermodynamic properties of glass.

This paper presents the results of a study of the thermal behavior of fedotovite K₂Cu₃O(SO₄)₃ and piypite K₄Cu₄O(SO₄)₄∙(Na,Cu)Cl minerals in a wide temperature range. The crystal structure of the holotype piypite specimen is refined at room temperature. The mechanisms of thermal expansion of minerals depending on the crystal structure are described.

In this study, Ba₃Lu(BO₃)₃ borate obtained by solid-phase synthesis is explored by high-temperature X-ray powder diffraction in the temperature range from 25 to 900°C. At room temperature, the compound expands slightly anisotropically (α_max/α_min = 1.2), and with an increase in temperature, the degree of anisotropy increases significantly (α_max/α_min = 6.9 at 900°C). The maximum expansion is observed along the crystallographic axis c (α_c = 10.45 × 10^–6°C^–1 at 25°C and 36.34 × 10^–6°C^–1 at 900°C), perpendicular to which the boron-oxygen triangles [BO₃] are located, and the minimum is in the plane where the triangles are located.