Том 92, № 4 (2018)

The possibility of subjecting aluminum to hydrophobization and superhydrophobization (SHP) with ethanol solutions of trialkoxysilanes and stearic acid is explored. It is shown that SHP coatings are highly effective in protecting Al against atmospheric corrosion. The thicknesses of surface SHP layers are determined via X-ray photoelectron spectroscopy and ellipsometry. The protective ability of SHP coatings is determined by polarization measurements and corrosion tests in a salt fog chamber.

Thermochemical properties of liquid alloys of the Sn–Yb system are studied via calorimetry at 1110–1310 K over the ranges of concentrations 0 < x_Yb < 0.47 and 0.82 < x_Yb < 1. Considerable negative heat effects of the mixing of these alloys are identified. Activities of the components, the Gibbs energies and entropies of mixing, and the liquidus curve of the phase diagram of this system are calculated using the ideal associated solution (IAS) model and agree with data from the literature.

The temperature dependence of heat capacity C^°_p= f(T) of crystalline arsenate Mg_0.5Zr₂(AsO₄)₃ was studied by precision adiabatic vacuum and differential scanning calorimetry in the temperature range 8−670 K. The standard thermodynamic functions C^°_p(T), H°(T)–H°(0), S°(T), and G°(T)–H°(0) of the arsenate for the range from Т → 0 to 670 K and the standard formation entropy at Т = 298.15 K were calculated from the obtained experimental data. Based on the low-temperature capacity data (30–50 K) the fractal dimension D of the arsenate was determined, and the topology of its structure was characterized. The results were compared with the thermodynamic data for the structurally related crystalline phosphates M_0.5Zr₂(PO₄)₃ (M = Mg, Ca, Sr, Ba, Ni) and arsenate NaZr₂(AsO₄)₃.

The catalytic activity of natural and synthetic mordenites modified with Cu²⁺, Zn²⁺, and Pd²⁺ cations via ion exchange was studied in the oxidative conversion of n-amyl alcohol to valeric acid under the action of oxygen. It is established that the highest activity and selectivity in this reaction is exhibited by mordenite hydrothermally synthesized from kaolinite and containing 3.0 wt % Cu²⁺, 0.1 wt % Pd²⁺, and 2.0 wt % Zn²⁺. The kinetics of this catalytic reaction is studied. Based on the experimental data, a possible stepwise mechanism is proposed, and a theoretically grounded kinetic model of the process is developed.

The kinetics of hydrogenation of 4-nitro-2′-hydroxy-5′-methylazobenzene in aqueous 2-propanol solution over the skeletal nickel is investigated at different initial concentrations. It is established that the hydrogenation of 4-nitro-2′-hydroxy-5′-methylazobenzene over a skeletal nickel in azeotropic aqueous 2-propanol solution proceeds via two parallel pathways at both low and high initial concentrations. It is shown that increasing the initial concentration of the hydrogenated compound above its level of solubility raises the rate of azo group transformation in 4-nitro-2′-hydroxy-5′-methylazobenzene, while the content of 4-amino-2′- hydroxy-5′-methylazobenzene does not change in the hydrogenate and is not accumulated in the bulk of solution.

The effect the means of synthesis have on the texture, phase composition, redox properties, and catalytic activity of binary oxide systems with the composition Ce_0.5Zr_0.5O₂ are studied. The obtained samples are characterized via BET, SEM, DTA, XRD, and Raman spectroscopy. A comparative analysis is performed of the physicochemical properties of biomorphic systems Ce_0.5Zr_0.5O₂ obtained using wood sawdust and cellulose as templates and the properties of binary oxides of the same composition obtained by template-free means. The catalytic properties of the obtained oxide systems Ce_0.5Zr_0.5O₂ are studied in the reaction of carbon black oxidation. It is shown that the texture of the oxide depends on the means of synthesis. When biotemplates are used, fragile porous systems form from thin binary oxide plates containing micro-, meso-, and macropores. Oxide obtained via coprecipitation consists of dense agglomerates with pores around 30 Å in size. In supercritical water, nanoparticles of metal oxide form that are loosely agglomerated. The intermediate spaces between them act as pores more than 100 Å in size. A system of single-phase pseudocubic modification is obtained using a cellulose template. The crystal lattices of all the obtained systems contain a great many defects. It is shown that the system prepared via synthesis in supercritical water has the best oxygen-exchange properties. A comparative analysis is performed of the effect the physicochemical properties of the samples have on their activity in the catalytic oxidation of carbon black.

Composite CeO₂–ZrO₂–Al₂O₃ (CZA) modified by selective doping with SrO was prepared by simple coprecipitation method. The characterization results reveal that the structural property of the modified sample is fundamentally different from that of undoped CZA, the doped SrO can selectively combine with Al₂O₃ and act as a stabilizer, meanwhile homogeneous CZ solid solution is formed which appears insusceptible to Al₂O₃. Consequently more lattice defects are created in CZAS, which facilitate the improvement of oxygen mobility. The UV–Vis DRS and XPS results demonstrate that after doping with SrO, the supported catalyst Pd/CZAS possesses higher surface Pd and Ce³⁺ concentrations, which consequently leads to improved reducibility and catalytic performance. Furthermore, the synergistic effect between CeO₂–ZrO₂ and SrO–Al₂O₃ helps improve the thermal stability of Pd/CZAS. As a result, after aging treatment, Pd/CZASa still maintains improved structural, textural, morphological and reduction properties along with enhanced three-way catalytic performance.

Enthalpies of dissolution of crystalline N-methylglycine in water and in aqueous potassium hydroxide solutions are determined at 298.15 K via direct calorimetry. Standard enthalpies of formation of the amino acid and products of its dissociation in aqueous solution are calculated.

The association constants in the bovine serum albumin/human serum albumin–Tween 20 system are determined in aqueous solutions at pH 3.5–8.0 by means of nonpolarized fluorescence and protein fluorescence quenching. It is found that the most efficient association of serum albumin molecules with Tween 20 micelles occurs at pH 5.0 near the isoelectric points of proteins.

The temperature dependences of specific and equivalent conductivities, viscosity, density, and crystallization temperature are determined for three 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([C_nMeIm] [Tf₂N], n = 2, 3, 4) ionic liquids saturated with water vapor at room temperature. It is established that in the area of positive temperatures, the relationship between viscosity and conductivity obeys the fractional Walden rule with exponents of 0.97, 0.92, and 0.92 for ionic liquids with ethyl-, propyl-, butylradicals, respectively. The temperature dependences of conductivity and viscosity are approximated using the Vogel–Fulcher–Tammann equation (R² > 0.999), and ideal glass transition temperatures T₀ are calculated for the investigated liquids. The obtained values of T₀ depend largely on the chosen range of temperatures. It is shown that [C₂MeIm][Tf₂N] occupies a separate position with regard to [C₃MeIm][Tf₂N] and [C₄MeIm][Tf₂N].

By “formol titrimetry” method solubilities of DL-phenylalanine (PA) in aqueous NaNO₃ solution were measured at 298.15 K. The standard Gibbs energy of PA in aqueous and aqueous NaNO₃ solution and also transfer free energy of PA was evaluated. The thermodynamic parameters: molar volume, densities, dipole moment and solvent diameter of aqueous solution of NaNO₃ have also been reported. Electrolyte effects on the solubility and relative stability of PA is guided by different types of interactions which are explained in this manuscript.

Temperature dependences of density and dynamic viscosity are obtained for the ionic liquid 1-butyl-3-methylimidazolium methyl sulfate in the temperature range of 298–328 K. Absorption bands in the IR and UV regions of the spectrum are identified and the structure of ionic liquid is characterized using the gap model.

The pair interaction potentials of the weakly bound Rb–CH₄ and Cs–CH₄ systems, which are active media of alkali metal vapor lasers with broadband diode or excimer laser pumping, were calculated by the ab initio method. The electronic problem was solved by the coupled-cluster method in the CCSD(T) version including the basis set superposition error and extrapolation to an infinite basis set. The obtained pointwise ab initio potentials were approximated by the analytical functions based on the orthogonal Chebyshev polynomial expansion with correct asymptotic behavior at the dissociation limit and then used within the framework of the molecular kinetic theory of rarefied gases to evaluate the reduced collision integrals and mutual diffusion coefficients.

Ferro-chromo-manganites with compositions LaMeFeCrMnO_6.5 (Me = Li, Na, K) are synthesized via ceramic technology from La₂O₃ (special purity grade), Fe₂O₃, Cr₂O₃, Mn₂O₃, and carbonates of alkali metals (analytical grade). The individuality of the resulting compounds is confirmed via X-ray phase analysis. The heat capacity of nanosized LaMeFeCrMnO_6.5 (Me = Li, Na, K) ferro-chromo-manganites is measured via dynamic calorimetry in the temperature interval of 298.15–673 K on an IT-S-400 apparatus. The values of C°_p(T) and thermodynamic functions H°(T)–H°(298.15), S°(T), and Φ^xx(T) are calculated. The temperature dependences of the electrical capacity (C), dielectric permeability (ε) and electrical resistivity (R) studied in the temperature range of 293–483 K show that these materials are also of interest for microelectronics.

An improved way of measuring the specific surface area of carbon materials that is based on the adsorption of methylene blue is proposed. It is found that the proposed method is more accurate for microand mesoporous carbon materials than the one described in GOST (State Standard) 13144-79. It is shown that the method ensures good correlation with the measured specific electric capacitances of the materials and allows us to assess the geometric shape and average size of mesopores in an investigated carbon material.

A new mesoporous carbon containing nitrogen and copper was prepared by carbonizing a polymer obtained by blending p-phenylenediamine, copper(II) sulfate, and glyoxal. XRD and XPS showed the existence of Cu metal and Cu₂S, and XPS indicated the presence of nitrogen in the mesoporous carbon. The FT-IR spectra suggested that the material contains different functional groups, such as C=C and C=N. N₂ adsorption–desorption indicated the presence of mesopores in the material. The mesoporous carbon was used as an adsorbent to investigate the adsorption for methyl orange. Static equilibrium test results showed that the adsorption isotherm for methyl orange is in agreement with the langmuir isotherm, and the Q_m is 434 mg g^–1. Adsorption kinetics indicated that the pseudo-second order adsorption mechanism is predominant in the adsorption process.

The Nucleodur HILIC zwitterionic stationary phase was characterized by linear solvation energy relationship (LSER) analysis in the supercritical fluid chromatography mode. It was shown that the main contribution to retention is made by hydrogen bonding interactions.

The Krafft temperature (Т_Kr) of 1-alkyl-4-aza-1-azoniabicyclo[2.2.2]octane bromides (Alk = n-C_nH_{2n + 1}, n = 14, 16, 18) (D-n) and complexes of them with transition metals [Cu(II), Ni(II), Co(II), La(III)] in water is determined via conductometry and compared their corresponding acyclic analogs (alkyltrimethylammonium bromides). The dependence of the complexes’ Т_Kr on the structure of the inorganic salts and the hydrophobicity of ligands is established. It is shown that the complexation of D-n with metal nitrates and the shortening of the ligand hydrocarbon radical reduce Т_Kr.

The trans–cis- and cis–trans-isomerization of styryl derivatives of heterocyclic N-oxides in acetonitrile and ethanol is studied. The isomerization quantum yields and spectral characteristics of the cis-form of the investigated N-oxides are determined. No thermally induced cis–trans-conversion is detected.

The effects of the transfer of reaction energy to electrons and the luminescence of trapped electrons under the influence of the recombination reaction of H atoms on the surfaces of light-sum accumulating Zn₂SiO₄–Mn crystals are studied. It is established that the intensity of heterogeneous chemoluminescence (HCL) from preliminarily UV-irradiated samples is directly proportional to the accumulated light sum and governed by trapped electrons, which are responsible for the accommodation of reaction energy through the electron channel with the resulting nonadiabatic chemoelectron excitation and luminescence of a crystal.