Glass Physics and Chemistry最新文献

The influence of reinforcing fillers of different structures on the physical and mechanical characteristics of thermoplastic elastomer (TPE) based on butadiene-styrene elastomer is studied with the aim of further application to additive technologies for the production of elastic materials of a complex geometry. The optimal concentrations for graphene and carbon nanotubes (CNTs) are selected to achieve the maximum reinforcement effect. It is noted that by introducing a combined filler into a polymer matrix, it is possible to obtain a synergistic effect and achieve higher physical and mechanical characteristics due to the different structure of the filler. It is shown that the use of 3D printing with nanoreinforced material allows achieving better physical and mechanical characteristics compared to the standard molding methods.

Sol-gel synthesis of precursor powders of zircon, zirconium oxide and a composite based on them is performed in two ways, i.e., by reverse precipitation and the microreactor technique in a two-step microreactor with intensively swirling flows. The results of synthesis at all stages of precursor powders (1 ‒ х)(H₂SiO₃‒ZrO(OH)₂)‒хZrO(OH)₂ were compared, i.e., after calcination at 850°C and after sintering in the 1000‒1300°C temperature range. The thermal behavior of the initial nanosized compositions has been studied by differential scanning calorimetry and thermogravimetry, and dilatometry. The thermal coefficients of linear expansion of ceramic samples were estimated. The microhardness values for the obtained ceramic composites with different prehistories and thermal conductivity results are given.

The dependence of the linear coefficients of X-ray and gamma radiation attenuation (LCRA) is studied in the energy range of quantum energies, E, from 0.2 to 3.0 MeV by optical glasses of the crown group on their density when it changes from 2.21 to 4.61 g/cm³. Both the published data on the LCRA of glasses and the data obtained in this study are used as the basis for this paper. For this, the values of the mass coefficients of radiation attenuation (MCRA) of oxides used in the production of crown glasses are calculated. It is established that the basic oxides (SiO₂, B₂O₃, P₂O₅, Na₂O, K₂O, CaO, ZnO, Al₂O₃), which are included in all types of crown glasses (LK, K, FK, TFK, BK, TK, STK) are characterized by a relatively weak dependence of MCRA on E. In contrast, the heavier oxides (PbO, Ta₂O₅, La₂O₃, BaO, CdO, Y₂O₃, ZrO₂), used to obtain BK, FK, TFK, TK, and STK glasses of certain grades, demonstrate a strong dependence of MCRA on E in the energy range from 0.2 to about 1.0 MeV, but in the region of the more high energy quanta, close to that for basic oxides. It is shown that for E values of 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, 1.0, 1.5, 2.0, and 3.0 MeV, the LCRA values for a wide range of glasses of the crown group are clearly described by linear dependencies on density, whose inclination angles decrease with the growth of E. Equations describing these straight lines are derived, which make it possible to accurately calculate the LCRA of glasses from their density. At the same time, with the E values changing from 0.2 to 0.4 (0.5) MeV, some glasses of the BK, TK, and STK types have lower LCRA values than those which would be expected if their LCRA values were located on these lines. These deviations are explained by the difference in the nomenclature and concentrations of heavy oxides in these glasses and in the glasses closest to them in density whose LCRA values fit well on the straight lines. For these glasses, at E ranging from 0.6 to 3.0 MeV, no deviations of the LCRA values from straight lines are observed.

By using the conventional melt quenching technique, the transparent glasses 55P₂O₅–35Na₂O–10Al₂O₃ (mol %) were prepared. Structural study has been investigated by using X-ray diffraction (XRD) and (EDAX) and it was found that the prepared samples were amorphous structure. Using the differential thermal analysis (DTA), the glass transition (T_g) and crystallization temperature (T_c) were determined, and the results show that the prepared glass samples exhibit thermal stability h '. Density, molar volume and oxygen packing density ensure that Al₂O₃ is incorporated in sodium phosphate glass. The dc, ac electrical conductivity and dielectric constants of the prepared glass samples have been investigated at frequency range (from 50 Hz to 5 MHz) and temperature T (from 303 to 443 K). The temperature dependence of the dc conductivity of prepared glasses follows the Arrhenius law. It was found that the values of activation energy ΔE_dc = 2.3 eV. The Cole–Cole plot was used to examine the conductivity mechanism for grain resistance. The results of the ac conductivity σ_ac and its frequency exponent (s) have been analyzed to determine the conduction mechanism. The exponent (s) has values between 0.42–0.8; consequently the (CBH) seems to be the most interesting model related to the obtained results.

SiO₂ nanoparticles modified with three bifunctional silanes—3-(trimethoxysilylpropyl) methacrylate, bis[3-(trimethoxysilyl)propyl]amine, and vinyltriethoxysilane—are obtained. Successful completion of the modification is confirmed by IR spectroscopy and scanning electron microscopy. In order to obtain coatings with increased hydrophobicity, modified SiO₂ nanoparticles are introduced into cycloaliphatic epoxy resin. To improve the physical and mechanical properties, the coating composition contains 30 wt % modified SiO₂ nanoparticles fillers are introduced: muscovite mica and titanium dioxide. It is shown that the most promising additive for obtaining hydrophobic coatings are SiO₂ nanoparticles modified by bis[3-(trimethoxysilyl)propyl]amine. When they are introduced in the epoxy-polymethylmethoxysilsesquioxane matrix in an amount of 40 wt %, the highest contact angle of wetting of 116° is observed.

In this work TiO₂ thin films are deposited on glass substrates by sol gel dip coating process. The effect of withdrawal speed on the properties and laser induced damage is investigated. Structural analysis showed that the TiO₂ films exhibited the amorphous phase. The film thickness, roughness and transmittance are found to be related to the withdrawal speed. AFM microscopy revealed that the layers were homogeneous, with no cracks on the sample surface. Evaluation of laser flux resistance showed that the damage threshold (LIDT) is inversely proportional to film thickness, and the damage mechanism is thermal melting.

By sintering nanosized powders in air in the range of 1000–1300°C, ceramic composites (1 – x)ZrSiO₄–xHfO₂ with low thermal conductivity are obtained. It is shown that at a temperature of 1300°C the composites are a mixture of monoclinic solid solutions of Hf_xZr_1 – xO₂ and SiO₂. For the first time, the temperature–concentration dependencies of the thermal conductivity of the obtained ceramic samples are presented. Using electron microscopy, the fracture surface of ceramic samples after sintering at 1300°C is investigated, their thermal behavior is studied using dilatometry, and the temperature coefficient of linear expansion is estimated.

Model borosilicate glasses of four compositions with different contents of the cesium–strontium fraction are synthesized. The following properties of glass are studied: melting temperature, glass density, compressive strength, homogeneity, and thermal and chemical resistance. Based on the obtained experimental data, technical requirements are developed for samples of a solidified short-lived fraction of high-level waste (HLW).

The novel polycrystalline phosphors BaBi_2 − xSm_xB₂O₇ (х = 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5), BaBi_{2 − x − 0.05}Eu_xSm_0.05B₂O₇ (х = 0.35, 0.4, 0.45) and BaBi_{2 − 0.15 − y}Eu_0.15Sm_yB₂O₇ (y = 0.05, 0.1, 0.15, 0.2, 0.3) were obtained by crystallization from a glass-ceramics. The BaBi_1.95Sm_0.05B₂O₇ and BaBi_1.7Sm_0.3B₂O₇ crystal structures were refined by single crystal X-ray diffraction data to R = 0.059 and 0.054 respectively. The distribution of the Sm³⁺ ions over cation sites was investigated, and the Sm³⁺ atoms occupy the M2 site in the Bi subposition. Thermal expansion of BaBi_1.7Sm_0.3B₂O₇ was investigated by high-temperature powder X-ray diffraction. The maximum thermal expansion is along the c axis. Such a character of the thermal expansion can be related to the preferred orientation of the BO₃ radicals located in the ab plane. Borates are thermally stable in the studied temperature range. Thermal analysis of the BaBi_1.7Sm_0.3B₂O₇ borate was performed using differential scanning calorimetry and thermogravimetry. No mass loss was observed according to thermogravimetry data. In comparison with glass ceramics BaBi₂B₂O₇, it can be concluded that activation of the crystal matrix by Sm³⁺ ions leads to an increase in the crystallization temperature from the melt from 540 to 660°C and an insignificant increase in the melting temperature from 630 to 635°C. Luminescence spectra, excitation and kinetic curves of the BaBi_2−xSm_xB₂O₇, BaBi_{2 − x − 0.05}Eu_xSm_0.05B₂O₇ and BaBi_{2 − 0.15 − y}Eu_0.15Sm_yB₂O₇ series are reported. The maximum luminescence intensity of BaBi_2 − xSm_xB₂O₇ and BaBi_{2 − 0.15 − y}Eu_0.15Sm_yB₂O₇ concentration series is observed for the x = 0.05 and x = 0.10 respectively. The novel BaBi_{2 − x − 0.05}Eu_xSm_0.05B₂O₇ and BaBi_{2 − 0.15 − y}Eu_0.15Sm_yB₂O₇ solid solutions is a promising tunable red-emitting phosphors.

Using computer methods (ToposPro software package), a combinatorial-topological analysis and modeling of the self-assembly of crystalline structures of the Ce₄Pt₁₄Si₈-oP52 (a = 19.633 Å, b = 4.036 Å, c = 11.224 Å, V = 889.4 ų) and Ce₆Pd₈Sn₁₂-oP52 (a = 27.701 Å, b = 4.614 Å, c = 9.371 Å, V = 1198.02 ų) family are carried out. For the crystal structure of Ce₄Pt₁₄Si₈-oP52, 21 variants of the allocation of cluster structures with the number of clusters N = 2 (6 variants) and 3 (9 variants), and 3 (6 variants) are established. A variant of the self-assembly of a crystal structure with the participation of clusters-precursors forming the following packing is considered: double tetrahedra K6 = 0@6 (Ce₂Pt₂Si₂) with symmetry g = –1, tetrahedra K4 = 0@4 (CePt₂Si), and rings K3 = 0@3 (Pt₂Si). For the crystal structure of Ce₆Pd₈Sn₁₂-oP52, 27 variants of the allocation of cluster structures with the number of clusters N = 2 (6 variants), 3 (11 variants), and 4 (10 variants) are established. A variant of the self-assembly of a crystal structure with the participation of clusters-precursors forming the following packing is considered: double tetrahedra K6 = 0@6 (Ce₂Pd₂Sn₂) with symmetry g = –1, rings K3 = 0@3 (CePdSn), rings K3 = 0@3 (PdSn₂), and spacer atoms Sn. The symmetry and topology code of the self-assembly processes of 3D Ce₄Pt₁₄Si₈-oP52 and Ce₆Pd₈Sn₁₂-oP52 structures are reconstructed from clusters-precursors in the following form: primary chain → layer → framework.