Anode with the Active Layer for Electrosynthesizing Ozone in a System with Solid Polymer Electrolyte

The synthesis of catalytic coatings on porous titanium electrodes by the method of magnetron sputtering is considered. The content of dopant ions Fe³⁺ and F^– is optimized as regards the activity and stability of the PbO₂ catalyst in the reaction of ozone electrogeneration as well as the current efficiency with respect to ozone. It is shown that the best characteristics of the electrochemical ozone generator are observed on the PbO₂ catalyst doped with Fe³⁺ and F^– ions in the amount of 3–4 and 1–2 at %, respectively.     

Laser diagnostics of ultrasonic outgassing of an insulating liquid

The efficiency of hydrogen evolution from transformer oil into a vacuum and into air under normal pressure is studied for the case when the oil is exposed to focused ultrasonic radiation. The study is performed by the method of spectroscopy of biharmonic-pumping coherent anti-Stokes Raman scattering (CARS) based on stimulated Raman scattering (SRS). Ultrasonic radiation at a frequency of 1.76 MHz is excited by a spherical piezoceramic transducer mounted on the bottom of the vessel and is focused on the surface of the oil. This causes the intense stirring of the oil with the formation of a fountain. The room-temperature diffusion coefficient of hydrogen in the transformer oil, 10⁻⁷ m²/s, is found by approximating experimental data by a theoretical relationship for hydrogen evolution into air. It is shown that ultrasonic radiation with a power density of 2.2 kW/m² accelerates diffusion processes ten-to fifteen-fold.     

Isotopic selectivity of pulsed excitation of zinc atoms upon the 4s21S0 → 4p3P

The spectral dependences of the isotopic selectivity of the optical excitation of zinc atoms in the course of an efficient photochemical reaction with molecules of a reagent gas are calculated within the framework of a simple model taking into account the gas mixture flow. At a certain frequency detuning of monochromatic laser radiation, a high selectivity of isotope separation is realized at the end of the interaction region under the condition that the isotopic shifts are smaller than the Doppler broadening. __________ Translated from Optika i Spektroskopiya, Vol. 98, No. 6, 2005, pp. 869–874. Original Russian Text Copyright ? 2005 by Fateev.     

Effect of an ultralow-frequency electric field on the explosive instability threshold of ice

It is found that a weak (10³–10⁵ times lower than breakdown fields) ultralow-frequency (1<ω<1000 Hz) electric field has a strong effect on the explosive instability threshold of ice uniaxially compressed by high pressures in the temperature range 210–240 K. The explanation for the high electromechanical sensitivity of ice is based on the concept that ice undergoing structure modifications due to highly nonuniform compression is a heterogeneous system with cooperative phenomena in space-bounded sets of dipoles. The dipoles form around new-phase nuclei, defects, or air microbubbles and occupy domains with a typical size of 10⁻²–10⁻⁵ mm. When exposed to ultralow-frequency electric fields, such systems may exhibit resonant bursts of polarization, causing the ice stability to drastically drop because of dipole compression or microbreakdowns.     

Study of chemical bonding in the interhalogen complexes based on density functional theory

The density functional theory analysis was used for a number XYL complexes (XY is a dihalogen molecule and L is a Lewis base), formed between molecules I₂, ICl, IBr and pyridine. The calculated geometrical parameters, IR spectra and nuclear quadrupole interaction constants of iodine are consistent with the data of microwave spectroscopy and nuclear quadrupole resonance. The good correlation between the experimental and calculated binding energies of the inner electrons of iodine, chlorine and nitrogen atoms were found with the calculation using both Gaussian and Slater functions. The comparison of experimental and calculated changes in the electron density on the atoms upon complex formation suggested the choice of scheme for calculating the effective charge on the atoms, which allow us to interpret the experimental spectra. It is shown that the use of both calculated schemes allows us to predict the enthalpy of complex formation in close agreement with the experimental values. The energy analysis shows that in the complexes the electrostatic binding energy dominates that of covalent binding.     

Electrolyte systems for primary lithium-fluorocarbon power sources and their working efficiency in a wide temperature range

New compositions of liquid organic electrolytes with working temperatures of up to–50°С were developed for low-temperature primary Li/CF _x power sources. Five different compositions of organic electrolytes with a 15-crown-5 (2 vol %) addition and without it were studied on laboratory Li/CF _x power sources. 1МLiBF₄ (LiPF₆) in an ethylene carbonate/dimethyl carbonate/methyl propionate/ethylmethyl carbonate (EC/DMC/MP/EMC) (1: 1: 1: 2) mixture and 1 М LiPF6 in an EC/DMC/EMC (1: 1: 3) mixture each with a 15-crown-5 (2 vol %) addition were found to be the best compositions of organic electrolytes with working temperatures of up to–50°С. The electrochemical tests at 20 and–50°С in the Li/CF _x system showed that the 15-crown-5 addition increased the length of the discharge plateau at–50°С three- or fourfold. The mechanisms responsible for the increase in the discharge capacity of the CF _x cathode in the presence of a crown ether addition were suggested.     

Effect of the fuel electrode composition and structure on the performance of the direct methanol fuel cell

The effect the composition and structure of the active layer of the anode exerts on the performance of the solid-polymer direct methanol fuel cell is studied experimentally. It is shown that the ohmic voltage losses in the layer and the content of the solid polymer electrolyte (SPE) play an important role. The performance of the fuel cells is the best at 20–25 vol % SPE in the layer.     

A lens without poles: A conceptual design and the possibilities of its use in the channel of scanning cyclotron beams

It is shown that using a wide aperture magnetic lens without poles provides additional possibilities for improving the efficiency of scanning the systems of cyclotron beams for the following reasons: (1) The increase in the angle of deflection and, therefore, the length of the channel is reduced. (2) There is the possibility of improving the homogeneity of irradiation due to profiling magnetic conductors. (3) It is possible to align the fall angles of ions at edges of a target. The text was submitted by the authors in English.     

Quadrupole coupling constants and isomeric Mössbauer shifts for halogen-containing gold, platinum, niobium, tantalum and antimony compounds

We have analyzed by means of Density functional theory calculations the nuclear quadrupole coupling constants of a range of gold, antimony, platinum, niobium and tantalum compounds. The geometrical parameters and halogen nuclear quadrupole coupling constants obtained by these calculations substantially corresponded to the data of microwave and nuclear quadrupole resonance spectroscopy. An analysis of the quality of the calculations that employ pseudo-potentials and all-electron basis sets for the halogen compounds was carried out. The zero order regular approximation (ZORA) method is shown to be a viable alternative for the calculation of halogen coupling constants in molecules. In addition, the ZORA model, in contrast to the pseudo-potential model, leads to realistic values of all metal nuclear quadrupole coupling constants. From Klopman’s approach, it follows that the relationship between the electrostatic bonding and covalent depends on the nature of the central atom. The results on Mössbauer chemical shifts are also in a good agreement with the coordination number of the central atom.     

Shift of the dip in the ultralow-frequency electric excitation spectrum of the Bridgman effect

The previously predicted frequency shift of the deep dip in the ultra low-frequency (ULF) electric spectrum of the excitation threshold of the Bridgman effect in crystal hydrates has been observed. The appearance of this shift, which is caused by an increase in the temperature, is demonstrated for the example of magnesium hydroxide. The magnitude of the shift estimated qualitatively for two temperature — 20°C and 180°C — in a model with ULF-selective breakdowns of gas located in microcracks is virtually identical to the experimentally obtained value. This agreement attests to the possibility that micro breakdowns are excited in crystal hydrates under the conditions of a giant increase in their ULF permittivity in the process of strongly nonuniform quasistatic compression in relatively weak ac fields (E<2kV/cm). Pis’ma Zh. éksp. Teor. Fiz. 65, No. 12, 876–880 (25 June 1997)