Russian Journal of Physical Chemistry A最新文献

A new variational theory of the growth of particles of a new phase in supercooled multicomponent melts is developed. The crystallization of supercooled metal melts is characterized by various nonlinear effects on the surface of a growing crystal. A new variational means of nonequilibrium thermodynamics is developed to consider such effects, based on the principle of minimum entropy production. The approach allows the growth of an embryo of a new phase to be considered by allowing for the interrelated influence of thermal and diffusion processes, along with non-stationary effects associated with deviations from the local equilibrium on the surface of the growing embryo. The transfer of components across the phase boundary is described in the form of chemical reactions. An advantage of the theory is the possibility of obtaining a generalized theoretical description of nonlinear effects on the crystal’s surface. Expressions of crystal growth are given for different types of multicomponent metal systems to demonstrate the use of the approach.

The dependence of the melting temperature and enthalpy of fusion on the characteristic size and morphology of nanoobjects consisting of UO₂ and ThO₂ was studied by the thermodynamic method. The influence of the characteristic size and morphology on the enthalpy of fusion and melting temperature of UO₂ and ThO₂ nanoobjects becomes noticeable when their characteristic size is less than 20 nm. The melting point abruptly decreases when the characteristic size of nanoparticles, nanowires, and thin films of UO₂ and ThO₂ is less than 5, 4, and 3 nm, respectively. The size effect decreases in a sequence: spherical nanoparticles–nanowires–thin films in all cases. The size effect also decreases when individual UO₂ and ThO₂ nanoparticles are combined into nanostructured nanoobjects. The results of calculations obtained in the present study are in good agreement with the results of calculations obtained by molecular dynamics and experimental data available in the literature.

Crystallographic orientation is an important factor to affect the inhibition performance of metal materials, while the influence of crystallographic orientation of the pure aluminum metal on the electrochemical noise features during inhibition process is still unclear. In the present work, the inhibition behavior of 1,5-naphthalenediol on pure aluminum with different crystallographic orientations has been investigated using electrochemical techniques as well as some surface characterizations. Electrochemical impedance spectroscopy (EIS) results indicated that the pure aluminum specimen with (111) crystallographic orientation presented the highest corrosion resistance. The value of noise resistance calculated from electrochemical potential and current noise was positively correlated to the charge transfer resistance (R_ct) from EIS results. The parameter of corrosion energy (E_c) proposed from wavelet analysis of electrochemical noise data revealed an oppositely variation trend to R_ct with different crystallographic orientations. This observation was further confirmed by the X-ray photoelectron spectroscopy measurements. Lower E_c corresponded to stronger adsorption of inhibitors and E_c can be utilized as a potential criterion to estimate the corrosion rate and eventually ascertain the effect of crystallographic orientation on the inhibition performance.

A rheological study of solvation of algal cellulose and nanocellulose in dimethylacetamide with a lithium chloride addition as one of priority direct solvents has been performed. It was established that algal cellulose in solution can form spatial structures—cationic complexes with dimethylacetamide stabilized by chlorine anions. The activation energy of this process is 29.4–42.8 kJ/mol. The concentration dependence of viscosity indicates the presence of association interactions, which are most pronounced at a cellulose/nanocellulose concentration of >1.5% in solution. It was determined by rotational viscometry that 2.0% algal cellulose/nanocellulose solutions have pseudoplastic properties. The solutions are promising raw materials for the production of nonwoven materials and hydro/aerogels for biomedical use.

Aqueous solutions of nonionic surfactants behave differently than those of ionic surfactants. Micellar properties and structural characterization of Polysorbate 80 (commonly known as Tween 80) were investigated in the presence of different additives at different temperatures (303–323 K) by using cloud point (CP), densitometry, and viscometry techniques. Nonionic surfactant shows the optimum effect when used near their CP, as the presence of additives strongly influences them. The compounds or additives that break the structure of water will increase the CP, while those that help to build the water structure show a decrease in the CP. Adding ester, urea, and carbohydrates decreases the CP of Polysorbate 80, while alcohol and thiourea show the opposite trend. Density and viscosity measurements of Polysorbate 80 in the presence of monovalent salts (NaX, X = Cl^–, Br^–, ({text{NO}}_{3}^{ - }), and salicylate) confirmed the change in molecular structure.

Quantum and molecular mechanics (QM/MM) potentials are used to calculate molecular dynamics trajectories for the EYFP protein of the green fluorescent protein family. Machine learning models are constructed to establish the relationship between the geometric parameters of the chromophore in the frame of its trajectory and the properties of its electronic excitation. It is shown that it is not enough to use only bridging bonds between the phenyl and imidazolidone fragments of the chromophore as a geometric parameter, and at least two more neighboring bonds must be added to the model. The proposed models allow determination of the dipole moment variation upon excitation with an average error of 0.11 a.u.

Thermophysical properties like densities, refractive indices, and static dielectric constants have been measured for the binary mixtures of glycerol (GY) with N,N-dimethylformamide (DMF), ethylene glycol (ELG) and formamide (FMD) over entire concentration range at 293.15 K. From experimental data various related and excess properties were determined and reported for the binary systems. The results show that, the dielectric constant decreases for GY + DMF, GY + ELG and increases for GY + FMD mixtures. The densities and refractive indices of the studied systems decrease over the entire mole fraction range at the studied temperature. From results of related and excess properties various molecular interactions, hydrogen bonding, structural effects and other possible interactions between unlike and like molecules of the binary systems were discussed.

The authors explore the electrokinetic properties and electrophoretic deposition (EPD) of non-aqueous suspensions of samarium-doped cerium dioxide Ce_0.8Sm_0.2O_1.9 (SDC) with added molecular iodine at concentrations of 0 to 1 g/L. The study reveals an inversion of zeta potential in the SDC suspension as the concentration of iodine rises. Notable cathodic deposition is observed under EPD conditions in a suspension with 10 g/L of SDC and 1 g/L of added iodine at voltages above the threshold value (6 V), despite a negative zeta potential of −5.9 mV measured electroacoustically. Findings suggest a potential interpretation related to overcompensating for the charge in the suspension, due to high concentrations of co-ions and counterions within a double electric layer (DEL).

The Gibbs energies of the transfer of the silver(I) ion from methanol (MeOH) to dimethyl sulfoxide (DMSO) and from ethanol (EtOH) to N,N-dimethylformamide (DMF) were determined by potentio-metry. Our own and literature data on the thermodynamic characteristics of the transfer of Ag⁺ from alcohols (S₁) to aprotic (S₂) solvents were summarized and analyzed. It has been established that the replacement of amphoteric solvents with aprotic ones leads to significantly increased solvation of the silver(I) ion. The enthalpy contribution to the Gibbs energy of ion transfer in the case of the replacement (S₁ → S₂) is dominant. The strengthening of solvate complexes of Ag⁺ with solvent in the case of the replacement of S₁ by S₂ is caused mainly by an increase in the electron donor-acceptor (EDA) interactions due to a decrease in the acidity of solvents.

Single phase ceramic samples of new compositions (1 − x)NaNbO₃ – хLiNbO₃ (x = 0; 0.05; 0.10; 0.15), modified with a LiF additive, are prepared through solid state reactions, and their crystal structure, microstructure and dielectric and nonlinear optical properties are studied. A drop from 108.1 to 42.8 nm of the volume-weighted crystallite size distribution function corresponding to coherent scattering regions is observed. A rise in the temperature of phase transitions and a weakening of nonlinear optical properties are revealed as the concentration of Li cations grows.