Vol 43, No 2 (2017)

Modeling of the cluster self-assembly of icosahedral structure of Sc₁₂B₁₈₅C₉ (P6/mmm, hP212, V = 1641.7 Å3) boride has been performed. The suprapolyhedral cluster-precursor of the crystal structure Sc₁₂B₁₈₅C₉ containing 84 boron atoms that consists of the hexagonal antiprism apr-B12 (with the 6mm symmetry), which represents a template that links six В12 icosahedra followed by ring formation, has been determined for the first time. The symmetry and topology codes of the self-assembly of the crystal structure of nanoclusters-precursors represented by the primary chain S₃¹→ microlayer S₃²→ microframework S₃³ have been rebuilt. The assembly of the primary chain from B₈₄ clusters is characterized by their maximum possible degree of complementary binding corresponding to 18. There are 12 Sc atoms in the ring between clustersprecursors. The atoms of B (CN = 6) and C (CN = 4) bind the apr-B₁₂ polyhedra to form В₃ and С₃ rings (with two equally likely variants of their arrangement). The double distance between the centers of B84 clusters-precursors determines the value of the translation vector c = 8.954 Å. Microlayer S₃² is formed by binding parallel short chains with the participation of the Sc atoms; the B₇ and C₂ clusters are localized between the chains. The distances between the axes of the primary chains in the microlayer determine the magnitude of the translation vector a = 14.550 Å. The microframework is formed during the packing (with a shear) of microlayers according to the identical mechanism of the local binding of the primary chains. There are six equivalent primary chains in the macrocrystal structure in the local environment of the primary chain (a = b =14.550 Å). The predominant growth of monocrystals as rods and thin needles occurs on the direction of the assembly of the primary chain. The structural formula of Sc,C-boride with the precipitation of the framework- forming polyhedra and cluster structures that are formed in the voids is the following: Sc₁₂B₁₈₅C₉ = Sc₁₂[(ico-B₁₂)₁₂(apr-B₁₂)₂(B₇)₂(B₃)(C₃)(C₂)₃].

The kinetics of stepwise transformations during bulk isothermal crystallization of semiconducting AsSe_1.5Sn_x (x = 0.13, 0.20, 0.28) glasses has been studied in the temperature range of 210−310°С using ¹¹⁹Sn Mössbauer spectroscopy, XPA, and the density and microhardness measurements of the quenched specimens. The kinetics of the gross bulk crystallization of glasses have been analyzed according to the data on density measurement using the Kolmogorov–Avrami equation, which was generalized on stepwise and incomplete isothermal transformations.

The influence of nanocrystals on the optical centers of barium silicate glass has been studied experimentally. It is found that, when glass is irradiated in the thermal column of an atomic reactor or in a gammasource ⁶⁰Cо, the phase transformation of SiO₂ nanocrystals (crystoballite into tridymite) and BaO into BaO₂ and BaSiO₃ occurs, which creates a brown coloration, reduction in the microhardness, and weakening of the luminescence intensity.

The peculiarities of the formation of porous membranes based on aluminum oxide obtained by the electrochemical anodization of aluminum foil with the preset topological parameters of pores-capillares (20–220 nm) have been studied. The methods to study the membranes based on nanoporous aluminum oxide are proposed. The developed nanoporous material possesses the properties of screening IR radiation in a spectral range of 8–14 μm (corresponds to the spectral region of thermal radiation of bioobjecs). The membranes based on anodized aluminum foil provide the fulfilling the functions of channeling a high-flow helium ions with an energy of 1.5–2 MeV with the experimentally found coefficient of transmission of more than 60%.

The studies show that liquid glass, due to its high adsorption capacity and low bloating temperature, can be used to manufacture thermal insulation materials. The synthesis methods for highly porous materials by the low-temperature bloating of liquid glass and a filler were proposed for the first time. The proposed techniques contribute to the uniform bloating throughout the volume and the homogeneity of the thermal insulation material for the equipment and pipelines.

It is shown that the relaxation of the isotropic light scattering intensity by boron oxide melt, which is connected with a decrease in its magnitude after a temperature jump, is synchronized with the effect of changing the polarization state of the excitation light beam passed through the sample under investigation. The formation of macroscopic elastic stresses in the sample bulk could be one of the possible reasons for the development of the detected phenomenon.

Thin-layer glassy biopolymer matrix implants obtained as a result of the contact of lead(II) hexacyanoferrate( II) Pb₂[Fe(CN)₆] with an aqueous alkaline solution of ethanedithioamide (dithiooxamide) H₂N—C(=S)—C(=S)—NH₂ have been studied by high-resolution scanning electron microscopy. It is shown that lead (II) sulfide PbS nanoparticles with sizes of up to 50 nm are formed in accordance with the theoretical hypotheses.