Glass Physics and Chemistry最新文献

A method is proposed for calculating the temperature dependence of the microhardness of glass in the temperature range from absolute zero to the glass transition temperature. According to the model underlying the calculation, the glass passes into a plastic state not only under the action of temperature but also under the action of mechanical stresses above the critical value corresponding to microhardness. Therefore, under the simultaneous action of these two factors, the glass passes into a plastic state if the sum of the thermal and mechanical energy of the glass mesh exceeds the critical value. The proposed calculation method is tested on the example of organic glass and two of the most important oxide glasses for practice: fused quartz and industrial alkali-silicate glass (soda-lime-silica glass (SLSG).

The interaction of an aqueous solution of strontium nitrate with magnesium-doped potassium titanate nanotubes synthesized by coprecipitation followed by hydrothermal treatment is studied. It is found that after 2 h of exposure in the solution at room temperature, the composition with the replacement of 10 at % titanium by magnesium showed the greatest sorption capacity. The results obtained show the promise of using magnesium-doped potassium titanate nanotubes as adsorbents of strontium ions from aqueous solutions.

The scientific bases for the synthesis of precursors of nanostructured Al₂O₃–ZrO₂–M_xO_y (M = La, Y, Ce) oxide systems are developed. The features of the formation of precursors of such systems under conditions of rapid mixing of electrically generated reagents, implemented in a diaphragmless coaxial electrolyzer reactor, are studied. Using the methods of potentiodynamic polarization curves, X-ray diffractometry, X-ray fluorescence, synchronous thermal analysis, and laser diffraction, the anodic processes occurring in the electrolyzer and the morphology of particles formed in solution and transformed during heat treatment, as well as the phase, granulometric, and elemental compositions of precursors and oxide systems, are studied. The proposed approach makes it possible to obtain oxide systems modified with rare earth elements based on the Al₂O₃–ZrO₂ binary system, characterized by the presence of a tetragonal zirconium dioxide phase in them.

Using computer methods (the ToposPro software program), a combinatorial-topological analysis and modeling of the self-assembly of crystal structures of the Sr₁₂Mg₂₀Ge₂₀-oP52 (a = 21.707 Å, b = 4.483 Å, c = 18.456 Å, V = 1795.88 ų, Pnma), Sr₂LiInGe₂-oP24 (a = 7.503, b = 4.619, c = 17.473 Å, V = 605.63 ų, Pnma), and Sr₂Mg₂Ge₂-oP12 (a = 10.882 Å, c = 5.665 Å, V = 670.8 ų, Pnma) families is carried out. For the crystal structure of Sr₁₂Mg₂₀Ge₂₀-oP52, 17 variants of the cluster representation of a 3D atomic grid with 2 (5 variants), 3 (6 variants), and 4 (6 variants) structural units are established. The variant of the self-assembly involving the triple rings K3 = 0@3(SrMgGe) and K3 = 0@3(Mg₂Ge) and double tetrahedra K6 = 0@6(Sr₂Mg₂Ge₂) with symmetry –1, forming a suprapolyhedral cluster-trimer A from clusters (SrMgGe)(Sr₂Mg₂Ge₂)(SrMgGe) and the cluster trimer B from clusters (Mg₂Ge)(Sr₂Mg₂Ge₂)(Mg₂Ge), is considered. For the crystal structure (Sr₂Li)₂(InGe₂)₂-oP24, framework-forming polyhedra in the form of double tetrahedra K6 = 0@6(Sr₂Mg₂Ge₂) and triple rings K3 = 0@3(SrMgGe) are defined. For the crystal structure of Sr₂Mg₂Ge₂-oP12, the framework-forming polyhedra are defined in the form of double tetrahedra K6 = 0@6(Sr₂Mg₂Ge₂). The symmetry and topological code of the processes of self-assembly of 3D structures from clusters-precursors has been reconstructed in the following form: primary chain → layer → framework.

This study examines the features of the morphology and properties of disperse ZnO powders obtained by polymer-salt synthesis using polyvinylpyrrolidone (PVP). The processes of the thermal evolution of materials during the synthesis of powders are studied by differential thermal and thermogravimetric analysis. The crystal structure and morphology, as well as the luminescent and adsorption properties, of the synthesized nanopowders are studied by X-ray diffraction and electron microscopy analysis, as well as optical and luminescence spectroscopy. It is established that the addition of PVP reduces the size of the formed ZnO crystals and has a significant effect on the morphology, as well as the luminescent and adsorption properties, of the materials.

For the first time, a new ceramic “Ideal,” a diamond-silicon carbide composite obtained in the reaction-diffusion Turing process, which makes it possible to obtain materials with the optimal set of physical and mechanical properties, is studied. An elastic-brittle fracture related to the propagation of a shock wave in a two-component system is noted. The dynamic elastic limit, determined by the properties of silicon carbide, is found to be 13.4 GPa. Its dynamic elastic limit and spall strength in the region of the elastic deformation are measured. The impact compressibility of ceramics up to a pressure of 625 GPa is determined.

A methodology is developed and ZnO nanoparticles are synthesized in porous glasses. The synthesis is carried out by impregnating silicate porous glasses in an aqueous solution of zinc nitrate and its subsequent thermolysis. The spectral and luminescent properties of the synthesized composites are studied. The ability of ZnO nanoparticles formed in porous glass to produce reactive oxygen species under UV irradiation is studied.

Nanosized yttrium–aluminum garnet (YAG) powders are synthesized in a microreactor with swirling flows by the coprecipitation of yttrium and aluminum hydroxides followed by heat treatment. The resulting mixture of hydroxides is X-ray amorphous according to X-ray phase analysis. Thermal treatment of hydroxides at 1100°C for 1 h leads to the formation of Y₃Al₅O₁₂ nanocrystals. The method we developed is technologically advanced, easily scalable, saves energy and time, and does not require labor-intensive operati-ons.

Herein, we systematically studied the thermodynamic and kinetic aspects of glass forming compositions in Ca–Mg–Cu alloy obtained by drawing the isocontour. Parameter ({{P}_{{{text{HS}}}}}) derived from the enthalpy of chemical mixing (ΔH_chem) and normalized mismatch entropy ((Delta {{S}_{sigma }}/{{k}_{{text{B}}}})) is used as a glass-forming ability (GFA) parameter. Variation of ({{P}_{{{text{HS}}}}}) with reported and calculated compositions is evaluated. Linear relation of Cu with ({{P}_{{{text{HS}}}}}) is observed, whereas inverse relation of Ca and Mg is obtained. The linear variation of ({{P}_{{{text{HS}}}}}) with a supercooled liquid region (SCLR) ((Delta {{T}_{{text{x}}}})) is studied. Inverse correlation of critical cooling rate (({{R}_{{text{C}}}})) with ({{P}_{{{text{HS}}}}}) is obtained. ({{R}_{{text{C}}}}) for predicted compositions is found close to that of reported compositions. Therefore, Cu should be added carefully with other elements to improve the GFA and reduce the cooling rate of Ca‒Mg‒Cu glassy. In this paper, an empirical correlation of (Delta {{T}_{{text{x}}}}) with ({{P}_{{{text{HS}}}}}) is proposed, and the modeled values are found to agree with the experimental values.

The results of a study of the weather resistance of protective and decorative organosilicate coatings prepared using organosilicate compositions based on polydimethylphenylsiloxane as a binder and hydrosilicates as fillers are presented. The color of the coatings varies due to the use of pigments: natural FeO_x minerals of yellow, red-brown, and brown shades of flowers. Using X-ray phase and X-ray fluorescence (XRF) analysis, it is established that the composition of minerals is primarily determined by iron oxides in the crystalline modification of hematite (α-Fe₂O₃) and goethite (α-FeO(OH)). Pigments contain a small number of impurity compounds of a number of elements that contribute to the color range of the coatings. Organosilicate coatings are exposed for 11 months in the tropical climate of two climatic zones of Vietnam (in the suburbs of Nha Trang and Ho Chi Minh City). The high corrosion resistance and color stability of the coatings are established during the entire test period. According to slight changes in the color and gloss, revealed by spectrophotometric and photoelectric methods, it is shown that higher resistance to solar radiation and other adverse climatic factors is typical for coatings with a brown pigment based on hematite; and the lowest, with a yellow pigment based on goethite.