Vol 45, No 4 (2019)

The combinatorial-topological analysis and simulation of the self-assembly of the Na₃₂Au₄₄In₂₄–oP100 (space group P bcm, a = 5.483 Å, b = 24.519 Å, c = 14.573 Å, V = 1895 ų) crystal structure are conducted by the computer-based methods (TOPOS program package). A new type of the 12-atom K12 cluster formed from doubled pentagonal pyramids—AuAu₅ and InNa₅—is established. The maximal symmetry of the K12 cluster and the primary chain of translationally bound K12 clusters correspond to the noncrystallographic 5m symmetry. The symmetry and topological codes of the Na₃₂Au₄₄In₂₄–oP100 3D structure’s self-assembly processes from the K12 nanocluster precursors are reconstructed in the following form: primary chain → microlayer → micro-framework. The primary chains of bound K12 clusters with the m symmetry are located in the direction [100], and the distance between cluster centers determines the vector’s value: a = 5.483 Å. There are four nonparallel primary chains in the primary chain’s local environment. The chains from InAu atoms and NaAu₂In₂ clusters are located in the 2D layer between the primary chains. The distance between the equivalent chains in the direction [001] determined the vector’s value: c = 14.573 Å. In the 3D framework in the direction [010], the distance between the equivalent 2D layers determined the vector’s value: b = 24.519 Å.

Emission Mössbauer spectroscopy on ^119mmSn(^119mSn), ¹¹⁹Sb(^119mSn), ^119mTe(^119mSn), ^125mTe(¹²⁵Te), ¹²⁵Sb(¹²⁵Te), ¹²⁵Sn(¹²⁵Te), and ^129mTe(¹²⁹I) isotopes is used as a method for the creation and identification of antistructural defects in Ge₂₀Te₈₀, As₃₀Te₇₀, and Ge₁₅As₄Te₈₁ vitreous alloys in forms of tin atoms in tellurium and arsenic positions, as well as tellurium atoms in germanium and arsenic positions. Tin atoms in the positions of arsenic and tellurium, and tellurium atoms in the positions of germanium and arsenic rearrange their local environment, while the symmetry of the local environment of germanium positions remains unchanged in the case of their isovalent replacement by tin atoms.

The resistance of Mo₄₀Si₄₀B₂₀ magnetron coatings to high-temperature oxidation in the 1000–1200°С temperature range is investigated. The main phases of the initial coating are high-temperature β‑MoSi₂ with a hexagonal lattice and t-MoB. The phase transition of β-MoSi₂ phase into the low-temperature tetragonal α-MoSi₂ one proceeds at 1000°С. After annealing, the main structural components of the coating are the t-MoSi₂, t-Mo₅Si₃, and t-MoB phases. The size of the formed crystallites’ of the t-MoSi₂, t‑Mo₅Si₃, and t-MoB phases increases 1.5-fold at 1000–1200°С. The coatings oxidation is studied at 1200°С in the isothermal and non-isothermal modes. After annealing on the surface, a dense oxide SiO₂ layer formed and prevented the diffusion of oxygen to the substrate and its subsequent oxidation. In the case of non-isothermal annealing, the protective oxide layer’s thickness increases 2.6–3.6-fold compared to that during isothermal holding for the same holding time.

Thin polythiophene films are electrochemically deposited onto different types of substrates. We investigate the effects the conditions of polythiophene (PT) synthesis have on the pseudocapacitive (charge accumulation) properties of fabricated electrodes and identify the optimal synthesis conditions. Composite electrodes with a polyacrylamide (PAM) sublayer modified with trifluoromethanesulfonic acid exhibit the largest specific capacity (up to 550 F g⁻¹). With a PAM sublayer, polythiophene-based electrodes exhibit lesser (by 19%) losses of the initial capacitance compared to their PAM-free counterparts. The surface morphology of electrodes fabricated using steel support is studied by scanning electron microscopy and low-temperature nitrogen adsorption.

The results of studying the structural parameters and strength characteristics of a bioactive membrane are presented. The membrane was obtained based on high-silica glass via modification with silicon polyoxomolybdate. The membrane strength characteristics were simulated under conditions of the maximum pressure of a vacuum water-jet pump of 300 kPa.

The melting (decomposition) point for AlMgB₁₄ aluminum magnesium boride containing alumomagnesium spinel as an impurity (5.5 wt %) is experimentally evaluated. The melting is accompanied by the release to the gas phase. The decomposition process covers the temperature range of (2400–2573) ± 30 K. A partial loss of Mg is observed at 2073 K. The structure and element composition of crystallized objects are also studied.