Russian Journal of Physical Chemistry A最新文献

Membranes have been prepared from polysulfone and graphene oxide with mass concentrations from 0 to 0.4%. A series of experiments were conducted to study the permeability of the obtained samples at pressures of 10, 15, and 20 atm. The experimental time dependences of the permeated water volume at a constant pressure were obtained. The dependence of the membrane permeability on the graphene oxide concentration and pressure was calculated. Conclusions were drawn about the influence of graphene oxide concentration and pressure on the permeability of the samples.

In this study, experimental carry out of liquid–vapor and solid–liquid phase transitions were conducted for the ternary system {CO₂ (1) + ethanol (2) + acetaminophen (3)} at different concentrations of paracetamol in ethanol for temperatures from 313 to 333 K and pressures up to 12 MPa. Experimental high pressure phase transition data were obtained using the static method in a variable volume view cell. Experimental data were compared with the literature for systems containing acetaminophen in a saturated solution. The presence of paracetamol in the binary system {CO₂ (1) + ethanol (2)} significantly alters the behavior of the phase under the conditions of temperature and concentration studied. It was observed that in the ternary system {CO₂ (1) + ethanol (2) + acetaminophen (3)} with a saturated solution at the lowest temperature, 313 K, CO₂ acts as a cosolvent for mole fractions lower than 0.6. Thermodynamic simulations employing the Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) Equations of State (EoS) aligned the experimental results adequately. The observed minimal deviations in pressure and temperature validate the efficacy of the thermodynamic models applied in this study.

The catalytic and adsorption properties of supported mono- and bimetallic nanoparticles of the copper–silver and copper–gold systems were studied. The particle sizes were 5–9 nm. The catalytic properties of the samples were studied at 77 K in deuterium–hydrogen exchange reactions and ortho-to-para conversion of protium. A comparison of the obtained data on the catalytic properties of the samples in isotope exchange reactions in molecular hydrogen and ortho-to-para conversion of protium showed that the mono- and bimetallic nanoparticles of the systems have magnetic properties. A comparison of the activities of the mono- and bimetallic systems in the deuterium–hydrogen exchange reaction revealed a more significant synergistic effect for the copper–gold system relative to the copper–silver system, which is explained by the greater difference between the electronegativities of atoms in the systems.

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.