POLARIZATION AND FREQUENCY-POLARIZATION DEPENDENCES OF THREE-PHOTON INTERBAND LINEAR-CIRCULAR DICHROISM IN SEMICONDUCTORS OF CUBIC SYMMETRY

The polarization and frequency-polarization dependences of the linear-circular dichroism and light absorption coefficients in semiconductors of cubic symmetry, caused by vertical three-photon optical transitions between the states of the spin-orbit splitting and conduction bands, are calculated. KEY WORDS: three-photon optical transitions, spin-orbit splitting band, conduction band, linear-circular dichroism, light absorption, semiconductor.

Studying the Insulating Properties of Oxide Films Obtained on the Ti6A14V Alloy in Tartaric Acid Solutions Using the Method of Electrochemical Decoration by Copper

The investigation data of the formation peculiarities of oxide films on the Ti6A14V alloy in tartaric acid solutions have been given. It is shown that the behavior of alloy forming dependences is conditioned by the anode current density. At ja < 0.5 A∙dm-2 the continuous oxide film is not formed on the alloy surface and the preset value of the final voltage on the cell is not reached. With an increase in ja > 0.5 A∙dm-2, alloy forming dependences show a linear behavior that is indicative of the formation of low porous films. In these conditions, the oxide film formation rate is in direct proportion to the value of ja. The electrochemical oxidation of Ti6A14V alloy in tartaric acid solutions results in the formation of interference-colored oxide films. The oxide film ultimate thickness and color are defined by the preset voltage and are independent of the current density and electrolyte concentration. The isolating properties of obtained films were studied by the way of the cathode polarization of oxidized specimens in the sulfate copper-plating electrolyte. The research done allows us to make a conclusion that electrochemical copper deposition is a convenient tool for the detection of defective spots in oxide films. It is shown that due to the specific features of the reduction kinetics of Cu2+ ions on the oxidized titanium it is reasonable to use for the studies the initial sections of polarization dependences that correspond to ΔE = 0.2–0.25 V. The alloy polarization dependences allow us to establish unavailability of apparent dependences between the oxidation current density, the electrolyte concentration, the cell final voltage value and the polarization that occurs during the Cu2+ ion reduction. The anodic connection of copper-coated specimens conditions the reversible dissolution of a greater portion of the specks of copper deposits. It is indicative of the electron conduction of film defects. The obtained data allow us to vary the electrolysis parameters in a wide range with no significant influence of the treatment mode of Ti6A14V alloy on the quality of oxide coatings.

КІНЕТИКА СУМІЩЕНИХ КАТОДНИХ ПРОЦЕСІВ У ВОДНОМУ РОЗЧИНІ NaCl

Investigation of the kinetics of combined cathode processes in the electrochemical synthesis of sodium hypochlorite. Intensification of the process of molecular oxygen reduction in aqueous NaCl solution to improve the electrochemical synthesis of sodium hypochlorite using a gas diffusion cathode. Investigation of the effect of the gas diffusion regime on the kinetics of cathode processes, determination of the ranges of potentials and current densities of combined cathode reactions. Cyclic voltammetry for the study of kinetic parameters of the cathode process using the MTech PGP-550M pulse potentiostat. Iodometric titration to determine the concentration of sodium hypochlorite. ranges of potentials of combined cathode processes in conditions without air supply and with air supply through a gas diffusion electrode the possibility of depolarization by air oxygen of the cathode process using the gas diffusion mode of operation of a porous graphite electrode is shown. total and partial reductions (oxygen reduction and hydrogen evolution) polarization dependences without air supply and with air supply in an aqueous solution of 3 mol/dm3 NaCl are constructed to better understand the effect of air supply on the course of combined cathode processes. The obtained polarization dependences prove that the air supply to the gas diffusion electrode leads to an increase in the limiting density of the oxygen reduction current from 2 to 8 mA/cm2, which indicates the prospect of using a gas-diffusion cathode. Changing the nature of the cathode process can significantly reduce the difference in electrode potentials, and by controlling the oxygen supply rate, ClO– can be impeded to the cathode surface. For the field of electrochemical production, it consists in improving the electrochemical synthesis of sodium hypochlorite by increasing the current efficiency and reducing specific electricity consumption. By changing the nature of the cathode process of hydrogen evolution for the reduction of oxygen brought to the cathode-electrolyte interface using a gas diffusion cathode, the problem of cathode reduction of ClО– will be solved without contamination of the final solutions of sodium hypochlorite.