Glass Physics and Chemistry最新文献

In this study, high-temperature composite materials based on reactively sintered silicon carbide modified with a molybdenum bond are obtained. The microstructure, phase composition, and physico-mechanical properties of the formed composites are determined. It is experimentally shown that molybdenum in the process of reaction sintering forms a stable MoSi₂ phase with a silicon melt in the volume of the sintered ceramic material. It is shown that the numerical parameters of lacunarity and chaos allow us to evaluate the homogeneity of the material structure in a direct relationship with the variation of the technological modes of ceramic synthesis. The resulting composites are characterized by a density of about 3.02–3.16 g/cm³ and a bending strength of about 180–220 MPa.

This article presents the results of studies of 15 low-melting borosilicate glasses of different compositions using the simplex-based method of mathematical planning. For each glass, the melting temperature and uniformity, as well as the rate and degree of leaching are determined in accordance with GOST (State Standard) R 52126–2003 [1] and NP-019-2015 [2]. Mathematical models are built based on the data obtained. As a result of the research, the most promising area for further research and development of the composition of borosilicate glass for a removable small-sized melter designed by Mayak Production Association is identified.

This paper studies the morphological and structural changes that occur during the graphitization of synthetic diamond powder (with highly faceted edges) and micropowder during heat treatment in air at temperatures up to 1000°C and in a vacuum at temperatures up to 1600°C. The most developed facets of the original diamond crystals are the octahedral {111} and cubic {100} faces. It is established that graphitization begins from the vertices and edges of crystals. {111} faces are more susceptible to graphitization than {100} faces. The morphological analysis of graphitized diamond AC160 in air helps us to study the kinetics of graphitization: the growth of dendritic graphite crystals and the formation of “graphitization pits” on the surface of diamond facets. It is shown for the first time that graphite of different shapes is formed on different diamond faces at different rates; thus, on the {111} faces graphite forms and grows in the form of triangles, and on the {100} faces, in the form of squares. At a high temperature, the volumetric graphitization of diamond particles is observed, accompanied by their destruction, mainly in the growth stages.

The crystal structure and thermal behavior of Rb₃SO₄F a new compound is studied by in situ single-crystal X-ray diffraction analysis in a wide temperature range. The compound is stable up to a temperature of 377(10)°C and does not undergo phase transitions during heating. Calculation of the coefficients of the thermal expansion tensor showed that the structure expands strongly anisotropically: the maximum thermal expansion is observed in the ab plane, while the minimum is parallel to the [001] direction, which is closely correlated to changes in bond lengths and angles in the anion-centered FRb₆ octahedron.

The PbO–BaO–B₂O₃–SiO₂ system is studied using solid-state synthesis and melt crystallization methods and attempts are made to obtain samples of the maleevite (BaB₂Si₂O₈)—lead maleevite (PbB₂Si₂O₈) series. Due to the strong tendency of Pb-containing borosilicate materials to form glass, a lead-enriched analogue of maleevite is not obtained. In the study, a new lead borate Pb₂B₆O₁₁ (sp. gr. P–1, a = 6.582(1) Å, b = 6.593(1) Å, c = 11.310(2) Å, α = 98.29(1)°, β = 90.65(1)°, γ = 119.10(2)°, V = 422.4(1) ų) and a series of solid solutions (Ba_{1 – x}Pb_x)₃B₆Si₂O₁₆ (x = 0.2, 0.4, 0.6) are synthesized and characterized for the first time. The layered compound Pb₂B₆O₁₁ has a new structural type, while the solid solution (Ba_{1 – x}Pb_x)₃B₆Si₂O₁₆ is a structural analogue of the previously known Ba₃B₆Si₂O₁₆.

Ce-, Nd-, and Er-containing glasses based on the PbO–SiO₂ binary system are synthesized. The process of mass crystallization for the production of glass-crystalline (ceramic glass) materials as a result of their heat treatment at different temperatures is studied. Compositions of glass ceramics with the indicated crystallization nucleators are developed. It is established that a glass-crystalline material with improved physicochemical properties has been synthesized at relatively low crystallization temperatures (750°C).

The dependence of the ζ-surface potential of synthetic aluminosilicates with a montmorillonite structure of systematically varying Na_2x(Al_{2(1 – x)},Mg_2x)Si₄O₁₀(OH)₂·nH₂O composition, where 0.1 ≤ x ≤ 0.9, on the chemical composition of the samples and the pH of the environment is studied. The influence of the degree of isomorphic substitution of magnesium atoms by aluminum on the nature of the change of the ζ‑potential is shown. An increase in the degree of isomorphic substitution and an increase in the pH of the medium is accompanied by an increase in the negative charge of the sample surface. The results obtained make it possible to select the optimal compositions of aluminosilicate sorbents for the extraction of differently charged ions from aqueous solutions with different pH values and for use as carriers of drugs.

The effect of ultrasound energy on hydrothermal synthesis of metal borates and on the characteristic features of synthesized copper borates was investigated. In ultrasonic-assisted hydrothermal synthesis, the reaction parameters such as boron source, reaction temperature and time were optimized. The synthesis was achieved in the modest conditions of 60°C—2.5 min and 70°C—15 min for the boron sources borax and tincalconite, respectively. The obtained phases were identified as the compound of copper borate (Cu(BO₂)₂) with the powder diffraction file no. 00-001-0472. The reaction yields were also increased from 48 to 75% with modification of experimental procedure. The observed characteristic stretchings in spectral analyses proved the functional groups of three and four coordinated boron to oxygen bands. In the morphological analyses, less agglomerates were observed at the samples produced by using the boron source of borax than tincalconite. The results exhibited the beneficial effects of probable usage of the ultrasound energy on both the practical synthesis and the increase of characteristics.

The current study aims to synthesize radiation-shielding glass materials by adding MgO in different ratios. The melt quenching technique was used to produce the MgO doped glasses. XRD examination verified the produced MgO cubic phase. Glass samples were examined for their various physical properties and gamma radiation shielding abilities. The density of obtained samples rises with MgO concentration, from 2.647 to 2.744 g cm^–3. Experimental measurements of the MgO adding glasses’ LAC, HVL, TVL, MFP, and MAC values were made for gamma-ray energies of 384, 1173, and 1333 keV. For gamma rays with energy of 384, 1173, and 1333 keV, existing glasses displayed a decreasing behavior in the half value layer with an increase in MgO additive, whereas it caused an increase in behavior in the linear absorption coefficient and mass attenuation coefficient values. These findings suggest that current glasses hold promise for use in radiation shielding.

A methodology for selecting glasses for constructing observation radiation-shielding windows (ORSWs) with a high attenuation multiplicity of photon ionizing radiation, acceptable transmittance, and an increased effective refractive index is proposed, which is based on taking into account the influence of the elemental composition of the glasses on their characteristics of X-ray and gamma radiation attenuation. It is suggested that it is advisable to design different types of ORSWs: for the energy ranges from 1.0 to 3.0 MeV and from 0.2 to 1.0 MeV, respectively. Two acceptable versions for ORSWs are proposed: a crown-flint version based on a pair of TKN1–TF200 glasses or a pure crown one on the base of TKN1 glass.