Oxygen Reactions at the Interface of Nonstoichiometric Fluorides LaF3 and CeF3 with Chemically Modified Electrodes

The oxygen reaction at the interface LaF₃(CeF₃)|electrode,O₂(g) is studied in air on Pt and C electrodes and electrodes modified by supported oxides of Co, Sr, and/or La on C, Si, or Pt substrates. The experimental methods used are voltammetry with a linear potential change and stripping voltammetry and cyclic voltammetry. The voltammetric response is dependent on the nature of solid electrolyte and electrode, the balance between the substrate and active agent, and on the conditions of thermal treatment of electrodes. Mobile oxygen forms are discovered at interfaces CeF₃|C (Co _x O _y ), ₂ ([C] : [Co] = 1 : 10, 1 : 20); CeF₃|C (Co _x O _y ), ₂([C] : [Co] = 1 : 10); and CeF₃|Pt (Co _x O _y ), O₂([Pt] : [Co] = 1 : 40). The peak current I _pa in the anodic curves increases with extending the limit of cathodic potential scan E _rc. The peak current I _pc in the cathodic curves increases with extending the limit of anodic potential scan E _ra.     

A synergistic approach to the polydispersity of polymers

A scheme for calculating polydispersity coefficients of polymers during chain propagation in living polymerization is proposed on the basis of the synergistic approach (the master equation) with allowance for fluctuations in the number of free radicals at the stage of initiation. The molecular-mass-distribution function of living chains is calculated. The form of this function is shown to be dependent on the ratio between the constants of the elementary stages of chain initiation and propagation.     

Galvanostatic investigation of electrochemical processes at the LaF<Subscript>3</Subscript>/M (M: Ag,Bi) interface

The electrochemical processes at the interface between solid fluorine-conducting electrolyte LaF₃(Eu²⁺ 0.8 mol %) and silver or bismuth electrodes in the two-electrode cell with nonpolarizable reference electrode are studied using the galvanostatic method. The anodic galvanostatic transients of LaF₃: Eu²⁺/Ag and LaF₃: Eu²⁺/Bi interfaces are linearized on the log(η ? η_max), vs. t coordinates, i.e. the rate of LaF₃|MF _n |M electrode formation is limited by slow surface diffusion of metal adions. The initial portions of cathodic galvanostatic transients in the range of solid-electrolyte lanthanum reduction are approximated by the linear dependence of η on log(1 ? √t/τ). The plots of logI vs. 1/η are linear both for the lanthanum reduction and for silver and bismuth oxidation involving mobile fluoride ion of solid electrolyte, which is typical for two-dimensional growth of new phase.     

Electronic theory of irradiation-induced disoerdering and annealing in semiconductors

A new model of irradiation-induced disordering of semiconductors is proposed. According to this model, the disordered regions capable of self-annealing are stabilized by self-localized electronic excitations (electrons, holes, excitons). Pulsed annealing of these regions occurs through recombination of the electronic stoppers and dispersal of disordered regions thus takes place. This model agrees well with the experiments on amorphisation and laser pulse annealing. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 67–72, April 2006.     

Peculiarities of radiation-induced defect formation in nanocrystals embedded in a solid matrix

The modification of basic radiation-physics effects (elastic defect formation and amorphization) in nanoclusters placed in a solid matrix compared to the same processes in single crystals is considered theoretically. We introduce a diffusion model of defect formation and study the influence of the nanocluster-matrix interface on the displacement energy. Based on the percolation treatment, we show a significant change in the critical nanocluster amorphization dose compared to the case of a crystal. The influence of various types of irradiation on the amorphization processes is considered. Judgments about the variety of radiation-physics effects in nanoobjects are expressed.     

Cluster-clathrate structure of water in the Ising model

We use the Ising model to study cluster formation in water. An analysis shows that the correlation length is several times larger than the size of water molecules. The developed method gives a satisfactory estimate for the melting temperature of ice.     

Electrochemical Behavior of the LaF3:Eu2+/Me Interface (Me = Sm,Ce, Gd,V, Ag)

The electrochemical behavior of the LaF₃ : Eu²⁺| interface (Me = Sm, Ce, Gd, V, Ag) is studied using stripping voltammetry. Current–voltage curves for cells Ag, AgCl|KCl and KF|LaF₃ : Eu²⁺|Sm (or Ce) may be viewed as background curves for analyzing solid-phase reactions with other metallic electrodes. The substrate material is found to affect properties of interfaces LaF₃ : Eu²⁺/Gd (or V), which are characterized either by solid-phase reactions involving the fluoride ion of a solid electrolyte or by reactions involving oxygen. Regularities, obtained for silver in contact with LaF₃ : Eu²⁺, link electrochemical signals of the reaction of the silver fluoride formation with the contact area.