Russian Journal of Physical Chemistry A最新文献

An analysis of the literature shows that all surface characteristics of dispersed systems (surface tensions, contact angles, disjoining pressure, and the properties of small systems) have ambiguous thermodynamic definitions. The second law of Clausius thermodynamics, which requires additional experimental data on the periods of relaxation of momentum, energy, and mass transfer processes, is used to eliminate this ambiguity.

Thermodynamic models of liquid and ternary solid solutions in the Ag–Al–In system are constructed on the basis of available experimental information. These models and ones of other phases of this system known in the literature are used to determine the coordinates of invariant points of the Ag–Al–In system and a projection of its liquidus surface. Polythermal cross sections of the phase diagram of this system are calculated for compositions x_Al/x_In = 4.255, x_In/x_Al = 2.096, and x_Ag/x_In = 1.064, along with isothermal cross sections at 973 and 573 K.

The authors study the experimental conditions for determining the diffusion mobility of impurities in solid bodies. Considering these conditions shows the need to continue developing the familiar Gruzin technique. In studying a large group of elements in metallic beryllium, Gladkov’s research group analyzed the effects of refining, which includes the absorption of radiation of an isotope by a sample and the dynamics of changes in the source in the process of diffusion annealing. Mathematical tools for considering these effects are developed. It is concluded that the new ways of processing the experimental results can be used in studying the diffusion characteristics of a wide range of contaminants in solid matrices.

Cobalt nanoparticles embedded in a carbon matrix were obtained by thermolysis of glucose deposited on Co₃O₄/SiO₂. The magnetic characteristics of the obtained nanoparticles were measured. This process formed single-domain (d < 20 nm) carbon-coated Co nanoparticles. The average size and the size distribution of Co nanoparticles depend on the amount of glucose used for the preparation. The use of a relatively small amount of glucose (glucose/cobalt < 1 mol/mol) leads to the formation of carbon shells enveloping Co nanoparticles, which are resistant to oxidation in air up to 200°C. In contrast, the use of a larger amount of glucose leads to the formation of an amorphous carbon layer with metal particles enclosed in it. Thus, the resulting nanoparticles are more susceptible to oxidation, and approximately half of the deposited cobalt is oxidized to CoO within a few days of exposure to air.

The authors calculate the concentration dependence of the coefficient of mass transfer and mean-root-square fluctuations of attracting molecules under sub- and supercritical conditions for different approximations of cluster variation (CV) that allow for indirect correlations. The simplest lattice structure is considered: a uniform flat face (100) that provides an exact solution to the problem of multiple bodies. A comparison is given of characteristics calculated for a series of simplest CVM basis clusters (2 × n, n = 2–5, 3 × 3, 3 × 4) and a quasi-chemical approximation (cluster 2 × 1) that reflects only the effects of direct correlations. The coefficient of mass transfer is calculated within the theory of the absolute reactions rates of nonideal reaction systems. The effects the dependence of the motion of molecules has upon attraction from the side of neighboring molecules that block an available volume for movements on root-mean-square fluctuations are discussed. It is shown that a region near (above and below) the critical point can be selected in which there is an abrupt drop in the coefficient of diffusion because of large fluctuations of the material’s density. The increased accuracy of indirect correlations expands the area of thermodynamic parameters responsible for hindering mass transfer. The concept of transcritical first-order phase transitions and its relationship to the effects of kinetic resistivity to mass transfer are discussed.

A vertical methane fountain with sand particles of different sizes is simulated under laboratory conditions. The authors determine the intensity and duration of exposure to laser radiation with wavelength λ = 1.07 µm on sand particles needed for the stable ignition of an air–methane mixture. A cinematogram is presented of the ignition of a mixture on a laboratory model. The temperature of the gas mixture’s ignition, the time needed for radiation to heat particles to this temperature, and the maximum speeds of different particle sizes in the gas flow are estimated at ∼0.1 m³/s for laboratory conditions and ∼17 m³/s for a real emergency gas well. The angular velocity of the beam’s movement that is needed to keep particles with the highest speed in the zone of the beam while igniting the air–methane mixture is determined for a safe distance from the gas fountain. The main characteristics of a possible future laser complex capable of quickly solving the problem of remotely igniting a fountain of an emergency gas well are determined.

Bicyclohexyl dehydrogenation using PtCrNi-containing catalysts supported on oxidized Sibunit carbon is studied as a key stage of hydrogen storage and evolution systems using liquid organic hydrogen carriers. It is shown that modifying platinum with nickel and chromium raises the specific activity of the catalyst considerably, relative to the evolution of hydrogen at a low content of the noble metal (0.1 wt % Pt). It is found that using an oxidized Sibunit carbon support to synthesize active supported Pt catalysts for bicyclohexyl dehydrogenation does not produce products of side reactions.

Potentiometry and calorimetry are used to study the Ni²⁺–diglycine–L-histidine system in an aqueous solution at T = 298.15 K (KNO₃). The composition and stability of the mixed ligand complex Ni(GG)(His) are defined with potentiometric measurements. The study is performed at ratios Ni : (GG + His) = 1 : 4 and 1 : 6. The concentrations of diglycine and L-histidine are in ratios of 3 : 1 and 5 : 1. The values of (log beta ) obtained at different ratios of diglycine and L-histidine agree well with one another. Thermal effects are measured in the ampoule of a mixing calorimeter with an isothermal shell, a thermistor temperature sensor, and automatic recording of the temperature/time curve. The thermal effects of mixing solutions of Ni(NO₃)₂, diglycine, and L-histidine in the ratio (c_{{{text{Ni}}}}^{0}) : (c_{{{text{GG}}}}^{0}) : (c_{{{text{His}}}}^{0}) = 1 : 3 : 1 are measured to determine the enthalpy of formation of a Ni(GG)(His) particle. The experiments are performed at ionic strengths of 0.2, 0.5, and 1.0 (mol/L). The standard thermodynamic characteristics (Δ_rH°, Δ_rG°, Δ_rS°) of the formation of a mixed-ligand complex are determined. A comparative analysis of the obtained data is performed using thermodynamic characteristics of mixed-ligand complexation in the Ni²⁺–glycine–L-histidine and Ni²⁺–triglycine–L-histidine studied earlier. Structures of forming complexes are proposed.

Studies of intermolecular interactions in butyl acetate-dibutyl phthalate and butyl acetate-dioctyl phthalate systems show that except for excess volume, deviations of properties from an ideal mixture are reduced as the temperature rises. Results indicate considerable van der Waals forces and confirm the effect the size of molecules has on the properties of binary mixtures. Experimental data on density, refractive index, viscosity, excess molar volume, and other properties are presented for systems and pure substances.

An investigation is performed of the effect the treatment of a pulsed plasma flow has on samples of two shapes (flat and cylindrical) made of structural steels (St45, 40Kh, 65G, ShKh15, 40KhN2MA). Processing is done under different conditions with varying parameters (pulse duration, capacitor bank charging voltage, and the type of working gas). Data show that after treatment, corrosion resistance increases for most of the considered grades of steel. The most effective processing parameters are established for each grade of steel.