Oxygen kinetics and mechanism at electrocatalysts on the base of palladium-iron system

Binary nanodispersed carbon XC72 supported PdFe catalysts with different atomic palladium-to-iron ratios are synthesized and studied in oxygen reduction reaction in acid solution at 60 °C. The Pd:Fe ratio was well controlled by the initial concentrations of Pd and Fe in the precursor solutions. The nanoparticles were characterized by transmission electron microscopy, X-ray diffractometry and X-ray photoelectron spectroscopy. The optimum Pd:Fe ratio for this reaction was determined to be 3:1.The comparison of activities of the catalysts with component ratios equaled 3:1 and 10:1 is shown that the activities are differed from each other by 10-15 times in advantage of catalyst with lesser content of palladium. This phenomenon can be related to the different particle size of both catalysts and different distribution of particles by size discovered by TEM method. The achievement of maximum activity near the ratio of Pd:Fe = 3:1 is due to as effect of alloy-forming and the influence of binary system component ratio and synthesis conditions on dispersity degree of metallic phase nanoparticles. Under optimal conditions of precursor mixture high-temperature pyrolysis, iron produces the stabilizing effect palladium. It gives rise to obtaining the uniform and finely divided (7-8 nm) metallic particles.     

Polarization-interference micromethod for the study of mutual diffusion in polymer systems

Summary A polarization-interference technique is developed for the study of mutual diffusion that is applicable to systems covering the whole concentration range from polymer — low-molecular-weight compound systems to polymer — oligomer systems. The technique is based on variations of the refraction index within the diffusion zone and is shown to have advantages over similar ones. Its accuracy in terms of wavelength is 0.04. The polybutadiene — dioctyl phtalate system is used to illustrate how the concentration distribution of the components is calculated.     

Phase and conformational transitions in the polyvinyl chloride-butanone-2 system

Summary By studying optical densities in the visible region of the spectrum and the optical densities of infrared absorption bands, the structural and conformational states of the PVC — butanone-2 system were investigated. This system has a crystalline equilibrium and it is characterized by the formation of molecular complexes in solution. We observed two types of gel formed when the chemical equilibrium for the reaction of complexes formation is shifted by the evaporation of the solvent. It is shown that when PVC is dissolved, one type of supramolecular structure is broken down and another type is formed due to the stabilization of non-equilibrium PVC conformations by solvation.     

Phase state of polyelectrolyte complexes based on blends of acrylic copolymers

The phase state of polyelectrolyte blends based on acrylic copolymers was investigated with differential scanning calorimetry, transmission electron microscopy (TEM), and wedge microinterferometry as a function of the blend composition and ionization of polymer functional groups. A copolymer of N,N‐dimethylaminoethyl methacrylate with methyl methacrylate and butyl methacrylate was used as a polybase, a copolymer of methacrylic acid and ethyl acrylate was employed as a polyacid, and the optional plasticizer was triethyl citrate. A correlation was established between an earlier described mechanism of molecular interaction and the behavior of the glass‐transition temperature (T_g) of the polymer blends. The T_g values of the polyelectrolyte complexes in the gel phase were always higher than T_g in the sol phase. This fact implies that intermolecular cohesion dominated the free volume in the stoichiometric polyelectrolyte complexes formed in the gel phase, whereas nonstoichiometric complexes formed in the sol phase were characterized with the predominant contribution of free volume. TEM and interferograms of polyelectrolyte blends showed the signs of anisotropic ordered supramolecular structure formation. A phase‐state diagram of the polyelectrolyte blends was constructed. The stoichiometric polyelectrolyte complex was immiscible with parent polymers, forming a separate phase that became melted at elevation of temperature because of complex dissociation. Polyelectrolyte miscibility was supposed to result rather from the chemical reaction of the complex formation than from interdiffusion of the polymer components along the gradient of their concentration. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The Desorption of a Volatile Corrosion Inhibitor from Polyethylene

The kinetics of the desorption of a volatile inhibitor of atmospheric corrosion, hexamethyleneimine m-nitrobenzoate, from polyethylene film at 298–333 K was examined. The dependence of the desorption rate on concentration and the character of the inhibitor's distribution in the film was revealed. Effective diffusion coefficients of the inhibitor in polyethylene, as well as activation energy of the diffusion process, were calculated. Recommendations on the practical application of the inhibited film were offered.     

Constructing the set of program controls with probability 1 for one class of stochastic systems

The definitions of the program control for stochastic systems were traditionally constructed for the integral manifolds with time-independent equations. The presented approach takes into account the dynamism, time-to-time variability, of the invariance surface. A program control enabling the given dynamic stochastic system to remain within the given manifold was constructed, and an example was given.     

Phase Equilibrium and Morphology of High-Molecular Condensation Structures in Three- and Four-Component Systems

Protection of Metals and Physical Chemistry of Surfaces - Using the method of diffusion enrichment with a nonsolvent of polymer solutions in mixed solvents, porous structures are obtained and their...     

Structure and sorption properties of sized diacetate fibers

Lithuanian Textile Institute; Institute of Physical Chemistry, Russian Academy of Sciences. Translated from Khimicheskie Volokna, Vol. 25, No. 1, pp. 40–43, January–February, 1993.