Vol 45, No 6 (2019)

Using computer methods (the ToposPro software package), the combinatorial-topological analysis and modeling of the self-assembly of the Na₉₉Hg₄₆₈–hP567 crystal structure are carried out with the following parameters of the hexagonal cell: a = b = 39.703 Å, c = 9.681 Å, V = 13216 ų, space group P-6, and 132 crystallographically independent atoms. Three supracluster precursors K175-A, K175-B, and K175-C composed of Na₁₈Hg₁₅₇ are identified in the form of three connected gear rings of Na-polyhedra with symmetry g = –6. The symmetry and topological code for the self-assembly of the 3D structures from the precursor nanoclusters is reconstructed. In the [001] direction, the K175 supracluster precursors are linked by Hg₆ gear rings and Na spacers to form columns. In the columns, the distance between supraclusters K175 determines the value of the translational vector modulus c = 9.681 Å. When a skeleton is formed in the local environment of a column of K175-C supraclusters (centered at a height of z = 0), six columns of alternating K175-A and K175-B supraclusters are located with an offset of 1/2 in the [001] direction. The distance between equivalent columns from K175 clusters corresponds to the value of the translation vector modules a and b.

The fundamental principles for the synthesis of a new class of materials with a controlled (periodic) interconnected structure based on triply periodic minimal surfaces are formulated. The chemical synthesis based on the reaction-diffusion Turing reaction, which enables us to fabricate periodic microstructures, is analyzed.

Based on the mass spectrometric study of chalcogenide and fullerene-chalcogenide glass (CG), as well as amorphous and crystalline carbon nitrides with general formula C_nN_m, which are similar to CG, are considered according to the type of chemical bond, their vapor composition, and the effect of the initial specimens of the synthesized materials, including those containing metal components, fullerenes, and binary and ternary chemical compounds, as well as other structural units (SUs) and structural motifs.

Glass samples with formula as Li₂O–BaO–GdF₃–SiO₂:Sm₂O₃ were fabricated by melt quenching method. Their optical, physical and luminescence properties were studied, for their potential applications in photonic device working in visible region. The Sm³⁺ ions and nearby ligands bonding nature were determined from bonding parameters (δ) that in turn were calculated from LGF absorption spectra. Oscillator strength of different absorption bands and Judd–Ofelt (JO) parameters (Ω_λ (λ = 2, 4, 6)) were measured. JO-parameters and refractive index have been used to valuate various radiative properties of Sm³⁺ ions emission transitions in prepared glasses to explore their potential application as visible lasers. Furthermore, the emission was studied by exciting the LGF glass samples with different wavelengths (λ_ex = 275, 402 nm). The orange to red ratios at different wavelengths (λ_ex = 275 nm and X-ray) were evaluated to measure the Sm³⁺-ions local disorder in the glass network. The decreasing trend in experimental decay time (τ_exp) with Sm³⁺-ion concentration increasing was observed due to energy transfer. Best fit for the prepared glass, when studied in the light of Inokuti–Hirayama model was obtained for S = 6 indicating dipole–dipole type of energy transfer. The intense visible (orange) emission, high stimulated emission cross-section (σ_e), branching ratios (β_R), radiative transition probability (A_R), and reasonable quantum efficiency were determined for transition from ⁴G_5/2 to ⁶H_7/2 in glass. This suggests Sm³⁺ doped glass shows potential use for development of devices (laser and photonic) working in visible (orange) region.

An opportunity to operate by laser-induced nonlinear optical efficiencies of Ga₂S₃–La₂S₃ glasses doped with Er³⁺ and La³⁺ ions in the visible and near-infrared spectral ranges was explored. The laser-stimulated nonlinear optical properties were studied. The observed laser power and temperature dependences of the laser-stimulated second-harmonic generation and third-harmonic generation confirm the huge role of anharmonic phonon subsystems. Due to an occurrence of local structural distortions, the efficiency of laser nonlinear optical generation has been enhanced. Simultaneous occurrence of the second and third-order nonlinear optical response may indicate on the possibility of multifunctional applications of the investigated glasses in different electronic devices.

The physicochemical properties of glasses in the 50SrO · 50B₂O₃–50SrO · 50SiO₂ join (mol %), such as density, microhardness, thermal expansion, and glass-transition temperature, are studied. Comparison with the characteristics of strontium-borosilicate glasses in other join with the constant strontium oxide content shows that the molar volume increases with an increase in the concentration of B₂O₃ and does not depend on the SrO content in the range of 50 to 35 mol %. It is determined that the glass-transition temperature decreases with the replacement of SiO₂ by B₂O₃. The concentration dependences of the microhardness, thermal expansion coefficient above the glass transition region (α_l), and the change of the thermal expansion coefficient in the glass transition region (Δα) have a maximum in the composition range rich in boron oxide.

The aim of this study was to compare the effect of different immersion protocols into various acidic media on the surface roughness of various glass ionomer-based dental restorative materials in vitro. The total number of 200 specimens were prepared from 5 different restorative material groups. Ten specimens from each group were then immersed into one of the tested beverages including; Coca-Cola, Iced-Tea, orange juice and distilled water (control). All specimens were kept in oven at 37°C for designated time periods of 1 day, 1 week, 1 month, 3 months, 6 months and 1 year and solutions were renewed weekly. Surface roughness measurements were performed at baseline and after each immersion period. The surface roughness of all glass ionomer-based restorative materials were affected by immersion with acidic media to a degree. For Glass Carbomer, there were steady increases in surface roughness in Ice Tea and orange juice (p < 0.05). The only significant increase in surface roughness of Fuji IX was found in orange juice (p < 0.05). However, the difference was not significant in coke and ice tea in comparison to distilled water (p > 0.05). When compared with distilled water, surface roughness of Chemfil Rock had increased significantly in coke and orange juice (p < 0.05). Surface roughness values of F2000 had increased significantly in coke and ice tea compared with distilled water (p < 0.05). For Dyract XP, only significant increase was found in coke compared with distilled water (p < 0.05). In conclusion, compomers were determined as the most robust materials comparing the surface roughness of the other glass ionomer based materials particularly used in pediatric dentistry. The surface degradation following immersion with acidic media is a multifactorial process, not only the pH and composition of the acidic environment, but also the type and composition of the exposed restorative material have influence on this process.

This work describes the preparation of an organic-inorganic composite and the study of its characteristics. Particles of core (BaTiO₃)–shell (SiO₂–CoFe₂O₄) type were used as inorganic composite. These inorganic particles are used for the preparation of composites based on poly(vinyl alcohol) cyanoethyl ether synthesized in an external direct magnetic field. It is determined that the dielectric permittivity of the composites formed in an external magnetic field at the optimal content of the magnetic phase (concentration of CoFe₂O₄ = 20.3%) is four times as large (ε = 460 at the frequency f = 1000 Hz) as that of analogous composites formed without a magnetic field.

In an inductively coupled high-frequency discharge plasma, SiC_xN_y:H films are obtained from a mixture of hexamethylcyclotrisilazane vapor and argon at substrate temperatures of 100 to 400°C and a discharge power of 200 W. The simplest plasma components (nitrogen, cyan, silicon atoms, CH free radicals, and C₂ dimers) are determined. Some physicochemical properties of the films, including the growth rate, types of chemical bonds, refractive index, transparency interval, and contact angle, are studied. The synthesized films have a polymer-like structure.

Immobilization of europium ions in the Rho, Beta, and paulingite zeolites using ion exchange is studied in order to search for the optimal alumosilicate matrix for the development of solid-state radioluminescent light sources. The phase composition, thermal stability, moisture adsorption ability, and spectral characteristics of the specimens are studied. It is determined that Beta zeolite possesses the highest sorption capacity, high chemical and thermal stability, a significant constant capacity by water, and the highest cation-exchange characteristics regarding Eu³⁺.

A strong highly porous ceramic for endoprosthesis possessing open porosity and elasticity modulus values similar to those of bone tissue is prepared through the solid-phase sintering of specimens of the initial powders of the (ZrO₂)_0.97(Y₂O₃)_0.03 and [(ZrO₂)_0.97(Y₂O₃)_0.03]_0.8(Al₂O₃)_0.2 compositions with blowing agents. The dependence of the characteristics of the sintered ceramics on the composition of zirconium-containing powders and blowing agents is investigated.

Ceramic matrix composites for solidification and disposal of actinide-rare-earth fraction of high-level waste (HLW) were prepared by sintering of nanosized powders of 0.8LaPO₄–0.2Al₂O₃, 0.8LaPO₄–0.2Y₂O₃ and 0.8LaPO₄–0.2ZrO₂ obtained from 0.8LaPO₄ · nH₂O–0.2Al(OH)₃, 0.8LaPO₄ · nH₂O–0.2Y(OH)₃ and 0.8L-aPO₄ · nH₂O–0.2ZrO(OH)₂ precursors. These powders-precursors were synthesized via sol-gel technique. After heat treatment at 850°C powders of 0.8LaPO₄–0.2Al₂O₃, 0.8LaPO₄–0.2Y₂O₃ and 0.8LaPO₄–0.2ZrO₂ were obtained. Further powdered compositions were stepwise sintered to prepare ceramic composites which were supposed to be used as matrices for storage of HLW. Rate of La³⁺, Al³⁺, Y³⁺ and Zr⁴⁺ leaching from ceramic matrix composites in strength aqueous solutions of NaCl and Na₂SO₄ simulating underground brine typical for proposed location of HLW geological repository was estimated.

The aim of this work is to investigate the solubility enhancement of ibuprofen by formation of stable amorphous ternary system (ibuprofen, polyvinylpyrrolidon, β-cyclodextrin) compared to the binary system (ibuprofen, β-cyclodextrin). Ibuprofen was co-milled at ambient temperature in presence of PVP K30 and β‑cyclodextrin. The characterization of obtained mixtures was carried out using X-ray diffraction, infrared spectroscopy, scanning electronic microscope, differential scanning calorimetry and spectroscopy (¹H/¹³C). The dissolution test was carried out in order to evaluate the release rate profiles of ibuprofen in the prepared mixtures. A thermodynamically stable and water-soluble ternary system was obtained, the released amount of ibuprofen in the ternary system increased considerably in comparison to the pure drug. These results highlighted the effect of PVP which enhanced the aqueous solubility of the binary system ibuprofen/β-cyclodextrin in solid state by reinforcing intermolecular interactions and improving complexing abilities of β‑cyclodextrin.

The surface relief of blanks and silica glass fibers is studied by atomic force microscopy. The temperature change during free cooling is recorded using an infrared pyrometer. The results of the measurements of the roughness of the blank and fiber could indicate the effect of the cooling time of the quartz glass (QG) on the morphology of its surface.

The phenomenon of suppressing the potassium alkaline activity of Portland cement in the early stages of hydration in the presence of sodium water-soluble glass is established.

The paper is devoted to the investigation of the polymer additives’ influence on the strength properties of a sheet and to the analysis of the absorption bands related to the vibration of the groups that participated in the formation of the network of hydrogen bonds in the system: fiber–water–additive. The relation between the intensity of the absorption bands of the stretching vibration of the hydroxyl groups and the deformational vibrations of the water molecules and the functional groups with the sheet’s strength properties is presented.