Transport numbers of H+ and O2- in the electrochemical system (H2 + H2O),Me/BaCe0.9Nd0.1O3-α/Me,(H2 + H2O)

In the temperature range 873–1123 K, transport numbers of oxygen ions and protons are determined in the system (H₂ + H₂O), Me/BaCe_0.9Nd_0.1O_3-α/Me,(H₂ + H₂O), where Me = Ag, Au, Pt, Ni, by the emf and current methods. The determined transport numbers are independent of the determination method, the electrode material, the current direction (anodic and cathodic polarization of the electrode), polarizability of electrodes, and the partial water (hydrogen) pressure in the gas phase. This unambiguously suggests that the transport numbers refer to the solid electrolyte, and not the electrochemical system as a whole. It also follows that partial currents of the hydrogen ionization and the oxygen ion discharge are determined by the transport numbers of protons and oxygen ions in the electrolyte. At a constant temperature, their ratio is affected by neither the electrode potential nor the gas phase composition, i.e., both electrode reactions have a common limiting step (or steps). Deceased.     

SNH-Reactions of triazolo[4,3-b]- and tetrazolo[1,5-b]-1,2,4-triazines with methylene-active carbonyl compounds

Unsubstituted triazolo[4,3-b]- and tetrazolo[1,5-b]-1,2,4-triazines react with carbanions generated from dimedone and barbituric acid to give adducts of a C-nucleophile with the heterocyclic system through the C=N double bond. The adducts can be oxidized under mild conditions into products of nucleophilic hydrogen substitution. Analogous adducts with carbanions produced in the reactions of ethyl cyanoacetate and ethyl malonate with Bu^tOK proved to be unstable; in this case, the title azolotriazines immediately yield products of nucleophilic hydrogen substitution in position 7. Tautomerism of the S _N ^H products obtained is discussed.     

A simple one pot synthesis of condensed 1,2,4‐triazines by using the tandem aN‐SNipso and SNH‐SNipsa reactions

A new synthetic approach to condensed 1,2,4‐triazines based on using the tandem A_N‐S_N^ipso and S_N^H‐S_N^ipso reactions has been developed. 5‐Methoxy‐3‐penyl‐1,2,4‐triazine and its N₁‐methyl quaternary salt were found to react with C,N‐, C,O‐ and N,N'‐bifunctional nucleophiles (m‐phenylenediamine, resor‐cinol, semicarbazide and ureas) into triazacarbazoles, benzofuro[2,3‐e][1,2,4]‐triazines, and 6‐azapurine derivatives. In all cases nucleophiles attack first the unsubstituted C‐6 carbon of the triazine ring, while the final stage is replacement of the methoxy group affording cyclization products.     

Condition for Break-up of Non-Wetting Fluids in Sinusoidally Constricted Capillary Channels

Analysis of capillary-pressure distribution in single channels with sinusoidal profile shows that surface tension-driven flow in such channels is controlled by the pressure extrema at their “crests” and “troughs”. Formulating the geometric condition for the pressure in the troughs to exceed that in the crests leads to a simple criterion for the spontaneous break-up of the non-wetting fluid in the necks of the constrictions. The criterion reduces to the condition for the Plateau-Rayleigh instability as a limiting case. Similar pressure analysis is applicable to the case of a non-wetting fluid invading an open pore body. Computational-fluid-dynamics experiments have verified the validity of the break-up predicted from the capillary-pressure argument. Although the geometric criterion for the break-up is valid for small capillary numbers, it provides a common framework in which the results of various published studies of a non-wetting phase choke-off in capillary constrictions for a wide range of capillary numbers can be explained and understood.     

Kinetics of the electron beam induced crystallization of amorphous ZrO2 films obtained via ion-plasma and laser sputtering

Physics of the Solid State - The structure and electron beam induced crystallization kinetics of amorphous ZrO2 films obtained via ion-plasma and laser sputtering were compared. The studies were...     

Effect of bias voltage and nitrogen pressure on the structure and properties of vacuum-arc (Mo + Ti6%Si)N coatings

Effect of deposition conditions in reactive nitrogen atmosphere on the growth morphology, phase composition, structure, and mechanical characteristics (microhardness) of vacuum-arc multilayer coatings obtained using evaporation of the (Ti6%Si) and Mo cathodes is studied with the aid of raster electron microscopy, energy-dispersive elemental microanalysis, and microindentation. It is demonstrated that nitrogen atoms are redistributed to the region of the strongest nitride-forming element (Ti) in relatively thin layers (about 7 nm) consisting of substances with substantially different heats of formation (−336 kJ/mol for TiN and −34 kJ/mol for MoN). Such a process leads to lamination with the formation of nitride TiN and metal Mo (weaker nitride-forming element). Nitrogen–metal bonds are saturated in the layers of strong nitrideforming elements Ti(Si) when the nitrogen pressure increases from 6 × 10^–4 to 5 × 10^–3 Torr in the condensation procedure. Thus, the compound is filled with nitrogen to the stoichiometric composition and, then, the second system of layers based on molybdenum is saturated with nitrogen with the formation of the γ-Mo₂N phase. An increase in bias potential U _SP from–100 to–200 V stimulates mixing in thin layers with the formation of the (Ti, Si, Mo)N solid solution and leads to a decrease in microhardness from 37 to 32 GPa.

     

Diffusiophoresis of an aerosol particle in a binary gas mixture

The diffusion force and rate are calculated for the diffusiophoresis of a spherical particle in a binary gas mixture by solving the gas–kinetic equations. Two schemes of diffusiophoresis are considered: constant–pressure diffusion and diffusion of one mixture component through the other fixed component. The problem is solved by the integral–momentum method at arbitrary Knudsen numbers. Diffuse scattering of the gas molecules on the particle surface is assumed. The Lorentzian and Rayleigh models of a binary gas mixture are considered. The dependences of the force and rate of diffusiophoresis on the Knudsen number and the other determining parameters are analyzed. The results obtained are compared with well–known experimental data.     

Synthesis of some 5-aryl(hetaryl)tetrazoles by ultrasonication

The influence of ultrasound on the 1,3-dipolar cycloadditio of azides to organic nitriles to form of 1H-5-aryl(hetary)tetrazoles was studied. It was shown that ultrasound decreases the reaction time, and increases the yield of the desired compounds.Institute of Organic Synthesis, Ural Region Russian Academy of Sciences, Ekaterinburg, 620219. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1375–1377. Original article submitted November 1, 1994.     

The Influence of Leucanol on the Aggregative Stability of Synthetic Latexes

On the example of model systems (polystyrene latexes and copolymers of styrene with polar monomers, acrylonitrile and ethoxyethyl acrylate), the effect of sodium naphthyl formaldehyde sulfonate on the aggregative stability of synthetic latexes was analyzed. Upon reaching the limit conversion, these latexes during storage spontaneously transfer to a solid gel having a periodic colloidal crystal-like structure. It is shown that the gelation process obeys the Smoluchowski law for coagulation. An increase in the molecular weight of the polymer and in the size of the latex particles during the formation of the gel was recorded. The introduction of a NF dispersing agent neutralizes the gel effect, stabilizes the system, prevents gelation and leads to a slight increase in the molecular weight of the polymer and the degree of polydispersity of the polymers obtained. It has been suggested that stable macroradicals accumulating from the gel-effect stage and remaining in the system after completion of polymerization can be one of the reasons for the loss of aggregative stability of latexes, and incorporating the dispersing agent into the adsorption layer of polymer-monomer particles leads to the recombination of these radicals within the particle and the stabilization of latexes in the polymerization process.