Vol 78, No 4 (2016)

Molecular dynamics simulation of a cationic micelle having a rigid hydrophobic core and mobile cationic head groups has been performed taking into account the electronic contribution into solution polarization. As compared with an analogous micelle previously considered with no regard to the polarization effects, the latter manifest themselves as a weaker structuring of micelle crown and greater concentrating of counterions in it. Analysis of the local electric potential has indicated that the discrepancy between the data of the continual and atomistic descriptions of water remains preserved. Thus, agreement between the theory and numerical experiment cannot be achieved when describing the local electric potential with no allowance for the local character of polarization.

The kinetics of solid Fe–Cr solution formation has been studied during mechanical alloying of Fe and Cr powders taken in an atomic ratio of 80: 20. X-ray diffraction and Mössbauer spectroscopy data have been analyzed within the framework of the energetic approach. It has been established that, in this system, reaction product yield N is related to mechanical energy dose D and specific surface area S of Fe nanograin boundaries in an ideal manner: N ~ D² at S ~ D and N ~ D at S = const.

The Stokes flow field and aerosol particle deposition from flows in model filters, i.e., separate layers of granules with square and hexagonal structures, have been calculated taking into account the effect of gas slip at granule surface. Approximating formulas have been derived for granule drag forces to a flow. The efficiencies of diffusion collection of particles have been calculated in a wide range of Peclet numbers with allowance for a finite particle size and the existence of a Knudsen boundary layer, the layer thickness being comparable with the particle sizes. The applicability of the cell model to the calculation of granular filters has been discussed.

Bulk condensation in a dusty vapor–gas flow has been numerically simulated taking into account dust particle size distribution. Two types of distribution (monodisperse and lognormal) have been used. Changes in the bulk condensation process that are relevant to the dustiness of the flow have been revealed by comparing the results obtained for dust-free and dusty flows at the monodisperse dust distribution. Variations in the relative contributions of the homogeneous and heterogeneous mechanisms with variations in the flow dustiness have been considered. The effect of the root-mean-square deviation in the dust particle sizes on the bulk condensation in the dusty flow has been illustrated by comparing the data obtained for the monodisperse and lognormal distributions.

The structure-related properties of silver nanoparticles synthesized in reverse micellar solutions of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) have been studied in the processes of electrophoretic concentraton of nanoparticles, drying of concentrates, and redispersion in n-hexane and n-decane. It has been shown that the dispersity of nanoparticles and stability of organosols to aggregation remain preserved upon the replacement of a low-volatile solvent (decane) by a high-volatile solvent (hexane). The developed procedures enable one to easily regulate important technological characteristics of metal-based inkjet “nanoinks,” such as concentration and size of particles, as well as viscosity and drying rate of the inks.

A procedure has been proposed for the direct synthesis (without the use of reductants) of silver nanoparticles in an epoxy polymer matrix with the formation of novel nanocomposites. The average size of the formed nanoparticles has been shown to be about 18 nm. The polymer cross linking leads to the formation of chain aggregates of the nanoparticles. Nanocomposites containing isolated (individual) silver nanoparticles can also be obtained.

Electron microscopy, X-ray diffraction, and chromatography-mass spectrometry have been employed to investigate the reduction of solid silver caprylate in ethylene glycol with the formation of silver nanoparticles. The structural characteristics of silver nanoparticles have been studied as depending on the conditions of their synthesis, including temperature, reduction time, and silver salt concentration. It has been found that, in the studied range of parameters under the conditions, when solid silver caprylate is dispersed in ethylene glycol, the characteristics of resulting nanoparticles are almost independent of the synthesis temperature. This peculiarity is related to the fact that the formation and growth of nanoparticles occur on the surface of silver salt crystals and are accompanied by gradual dissolution thereof. In this system, ethylene glycol plays the roles of a reductant and a solvent for liquid reaction products.

Salicylic acid was intercalated into an inorganic host consisting of ZnAl/MgAl-layered double hydroxides lamella by reconstruction method. Powder X-ray diffractograms showed that the basal spacing of the layered double hydroxide bearing salicylate as the intergallery anion expanded from 7.6 and 7.8 Å in the precursors to 14.49 Å and 14.85 in ZnAl and MgAl layered double hydroxide, respectively. These values suggest that the organic molecules form bilayers in the interlayer space. Fourier transform infrared study further confirmed intercalation of salicylate into the interlayer’s of the layered double hydroxides. The thermal stability of the intercalated salicylic acid is significantly enhanced compared with the pure form before intercalation. Using the XRD results combined with a molecular simulation model, a possible representation of the salicylate anion positioning between the lamellar layers has been proposed. The in vitro drug release from intercalated material was remarkably lower than that from the corresponding physical mixture at pH 7.5. The kinetic analysis showed the importance of the diffusion through the particle in controlling the drug release rate. The obtained results show that hydrotalcite may be used to prepare modified release formulations.

The gradient density functional theory and the Carnahan–Starling model formulated for describing the contribution of hard spheres have been used to calculate the profiles of condensate density in small critical droplets formed via homogeneous nucleation, as well as in stable and critical droplets formed via heterogeneous nucleation on solid charged and neutral condensation cores of molecular sizes. The calculations performed for water and argon at different values of condensate chemical potential have yielded the heights of the activation barriers for homoand heterogeneous nucleation as functions of vapor supersaturation at preset system temperatures. The interaction of condensate molecules with a solid core has been described by the resultant potential of molecular attractive forces. In the case of a charged core, the long-range Coulomb potential of electric forces has additionally been taken into account. Dielectric permittivities have been calculated as known functions of the local density of the fluid and temperature. The radius of the equimolecular droplet surface has been chosen as a variable describing the droplet size. Dependences of the chemical potential of condensate molecules in a droplet on its size have been plotted for water and argon with allowance for the action of capillary, electrostatic, and molecular forces. It has been shown that the role of the molecular force potential in heterogeneous nucleation increases with the size of condensation cores.

The streaming potential method realized in a slit-like setup using 10^–4–10^–2 mol/L KCl solutions has been employed to study the electrosurface characteristics of poly(ethylene terephthalate) films, both initial and irradiated by heavy ions, as well as track membranes with pore sizes of 50 and 210 nm made from these films. Their ζ potentials and surface charges have been calculated. The data obtained suggest that irradiation of the polymer films by heavy ions reduce the ζ potential and surface charge. However, as a result of film etching during the preparation of the track membranes, the ζ potential and surface charge increase and exceed the corresponding values for the initial film.