Glass Physics and Chemistry最新文献

Bismuth-containing composite materials (CMs) with variable yttrium oxide content are synthesized by impregnating porous silicate glass matrices in acidified aqueous-salt solutions of Bi(NO₃)₃·5H₂O in the presence of Y(NO₃)₃·6H₂O with their subsequent heat treatment at 650 or 870°C, and their luminescent properties are studied. It is found that the synthesized materials exhibit photoluminescence in a wide spectral range (230–900 nm) due to the presence of various active centers (=Si⁰, Y³⁺–({text{O}}_{3}^{{2 - }}), Si-BAC (silicon-associated bismuth active centers), radicals , Bi³⁺ and Bi²⁺ ions, Bi³⁺ pairs, silicon–oxygen defects), as well as the Bi³⁺ → Y³⁺ MMCT (metal-to-metal charge transfer) transition, as a result of which they can be considered as new promising solid-state phosphors.

This article presents the results of a study of the concentration limits of the existence of the hollandite phase in the Cs₂O–Al₂O₃–TiO₂ system. A number of samples with different ratios of cesium, aluminum, and titanium are obtained by combustion of citrate–nitrate compositions. The phase composition and microstructure of the obtained materials are studied using X-ray phase analysis and scanning electron microscopy. When studying the electrical properties, it is found that the Cs_1.16Al_1.84Ti_6.33O₁₆ (σ = 5.45 × 10^–5 S/cm at T = 750°C) has the highest specific electrical conductivity.

Using computer methods (ToposPro software package), a combinatorial-topological analysis and modeling of the self-assembly of crystal structures of the La₈Ni₄₀As₂₄–oP72 (V = 1069.3 ų, etc., Pnma group) and Ca₁₂Fe₃₂Pd₄As₂₄-oP72 (V = 1155.89 ų, etc., Pnma group) families are carried out. For the crystal structure of La₈Ni₄₀As₂₄–oP72, 79 variants are established for identifying cluster structures with the number of clusters N = 2 (1 variant), 3 (18 variants), 4 (30 variants), and 6 (30 variants). A variant of the self-assembly of a crystal structure with the participation of clusters-precursors forming the packing is considered: double tetrahedra-dimers K6(4a) = 0@6(La₂Ni₂As₂) and K6(4b) = (Ni₂As₂Ni₂) with symmetry g = –1, tetrahedra K4 = 0@4 (LaNi₂As), rings K3 = 0@3(Ni₂As), and spacer atoms Ni7 and As5. For the crystal structure of Ca₁₂Fe₃₂Pd₄As₂₄-oP72 93 variants are established of the cluster representation of a 3D atomic grid with the number of structural units equal to 2 (2 variants), 3 (15 variants), 4 (49 variants), and 6 (29 variants). A variant of self-assembly of the crystal structure of Ca₁₂Fe₃₂Pd₄As₂₄-oP72 with the participation of the clusters-precursors forming the packing is considered: double tetrahedra-dimers K6(4a) = 0@6(Ca₂Fe₂As₂) with symmetry g = –1, tetramers K12(4b) = 0@12 (CaFeFe₂As₂)2 with symmetry g = –1, tetrahedra K4 = 0@4(CaFe₂As), rings K3 = 0@3(Fe₂As), and Pd and As spacer atoms. The symmetry and topological code of the self-assembly processes of the 3D La₈Ni₄₀As₂₄–oP72 and Ca₁₂Fe₃₂Pd₄As₂₄-oP72 structures is reconstructed from clusters-precursors in the following form: primary chain → layer → framework.

This paper presents the results of determining the content of various acid-base sites (Brønsted basic, Brønsted acid, Lewis basic) on the inner surface of the pore space of high-silica porous glasses (PGs), obtained as a result of the through leaching of alkali borosilicate glass with a two-frame structure and modified by isothermal exposure at various temperatures in the range of 120–750°C. The relationship between changes in the content of the centers under consideration and the processes of hydroxylation and dehydroxylation of the PG surface is analyzed depending on the heat treatment temperature.

Glass formation in the As–Se–SbBr₃ system is studied. Glasses are synthesized by melting a batch of As, Se, and SbBr₃ at a temperature of 700°C. The density of the glasses and optical absorption in the IR region of the spectrum are measured. The glass transition and crystallization temperatures are determined using differential thermal analysis (DTA). The structure of the glasses is studied using Raman spectroscopy. It is proposed that antimony bromide enters the glass as isolated molecules, without exchanging bromine with arsenic selenide. The studied glasses are promising for the production of low-melting IR adhesives, lenses, and windows for various IR optoelectronic devices using the precise pressing method.

Communities of microfouling agents on polymethylacrylate plates (control) coated with antifouling enamel Bioplast-52 and experimental compositions containing ZnO–FeZnO, CuO–FeCuO, ZnTi₂O₄–ZnO, ZnTi₂O₄–TiO₂, and Ag–TiO₂ nanoparticles (NPs) are studied in the coastal water area of Sevastopol (Black Sea) in the period from August 30, 2022 to September 19, 2022. Sampling was carried out on days 3, 13, and 20. A comparative analysis of communities of microfouling formed on the studied coatings is carried out. A total of 72 taxa of organisms of different systematic groups are found on the surfaces: bacteria, fungi (33), and algae (38). The number of taxa on the coatings varied from 34 (Bioplast-52) to 49 (NP ZnTi₂O₄–TiO₂). According to the time of exposure, the number of taxa in the communities varied from 43 (3rd day) to 55 (20th day). The ratio of the final fouling biomass to the biomass formed on the 3rd day of exposure ranged from factors of 1.6 (ZnO–FeZnO NPs) to 24 (Ag–TiO₂ NPs). The index of the antifouling efficiency of the coatings (I_ef, %) was calculated. The best test result was obtained for a coating consisting of ZnTi₂O₄–ZnO NPs (I_ef = 63.78%). In the early autumn period, in the coastal zone of Sevastopol, compositions with CuO–FeCuO and Ag–TiO₂ NPs (efficiency indices of –36.01 and –43.18%) showed themselves to be unpromising.

The results of a study of the influence of the thickness of porous glass (PG) plates modified with zinc oxide on its photocatalytic properties and ability to photogenerate oxygen in aqueous media are presented.

Their small size, surface effects and tunneling allow the use of nanomaterials in applications such as catalysis, sensors and a lot of other fields. Fe₃O₄ is one of the main oxides used in nanotechnology due to its excellent photoelectromagnetic properties. In this paper, the polygonal Fe₃O₄ nanoparticles were prepared through high temperature synthesis method. Then, silica coating via Stöber method was applied to obtain a nanomaterial having uniform particles. The prepared Fe₃O₄ had good crystal form and ultra-high saturation magnetization, up to 134.2 emg/g. Fe₃O₄ prepared by dodecyl trimethyl ammonium bromide (DTAB) template method allows easy silica coating: the obtained Fe₃O₄@SiO₂ particles showed a good core-shell structure and corrosion resistance making them very promising in biological applications.

Self-cleaning materials played an important role in our daily life, but there remained some critical challenges such as complex fabrications, non-transparency, and poor long-term stability, which limited their applications. In this paper, acid-base silica sol and alkali-based silica sol were prepared by sol-gel method, with ethyl orthosilicate as the precursor. The two silica sols were mixed by different proportions. The mixed silica sol was evenly coated on the surface of the pretreated glass slide, and then modified by the low surface energy substance HDTMS and QX-18 fluorocarbon nanocoating, and finally prepared a hydrophobic and wear-resistant transparent coating. The surface topography of the coating was analyzed, and its acid and alkali resistance, wear resistance, self-cleaning performance and other properties were tested. The results showed that the optimal volume ratio of acid-base mixed sol was acid silica sol : alkaline silica sol = 3 : 7. The hydrophobic coating had good wear resistance, transparency, self-cleaning and acid resistance, but poor alkaline resistance.

The acid–base properties of the surface of SiO₂ and Al₂O₃ nanoparticles obtained by various methods are characterized by the adsorption of acid–base indicators and dynamic pH-metry. The effects of the applied synthetic approaches (including liquid phase and plasma-chemical processes, as well as electric explosion) on the functional composition of the studied materials (predominance of Lewis or Brønsted acid or basic sites with different pK_a values) and properties of suspensions prepared using the synthesized nanopowders are studied.