Surface Engineering and Applied Electrochemistry最新文献

This work demonstrates that the macroscopic size effect, which consists in the influence of electrodeposition surface area on the composition and properties (microhardness and corrosion resistance) of alloy coatings prepared by induced codeposition of iron group metals with tungsten, is a particular case of this type of effects and this requires maintaining the volume current density (VCD) constant during electrodeposition. The effect is associated with the formation of surface oxy-hydroxide and hydrogenated layers. For electrodeposition of Fe–W and Co–W alloys from a citrate bath, it is established that a change in VCD at a definite value for current density of electrodeposition results in changes in the electrode potential, current efficiency, and alloy composition. Anodic dissolution of the modified surface layer allows increasing the microhardness but does not cancel the dependence of coating composition and properties on the electrode surface area.

This study presented the comparison of the electrocoagulation efficiencies for steel, aluminum, and copper electrodes for the chemical oxygen demand (COD) removal and decolorization from solutions comprising the reactive orange 16. The electrodes were used in similar couples in this research, namely, Fe (anode) to Fe (cathode), Al (anode) to Al (cathode), and Cu (anode) to Cu (cathode). The samples were analyzed using spectrophotometric techniques UV/VIS and a colorimetric method. Higher removal efficiencies for color and COD were found at the current density of 0.025 A/cm², i.e. Fe/Al/Cu electrodes gave 91, 62, and 51% in the COD removal and 93, 82, and 70% for color removal. Other parameters taken such as pH, electrolysis time, and the initial azo dye concentrations were also optimized at all of the electrodes. The decolorization and COD removal efficiencies were found decreased with increasing the initial dye concentration. Being simple and cost effective, this technique can be applicable for the treatment of real textile wastewater.

The results of a study into the electrical and optical characteristics of an overvoltage nanosecond atmospheric pressure discharge between electrodes made of a superionic conductor (SIC) (Ag₂S) in krypton are presented. The destruction of electrodes in the discharge and the introduction of Ag₂S vapor into the interelectrode gap occurred due to the microexplosions of inhomogeneities on the working surfaces of polycrystalline electrodes (the formation of ectons) in order to synthesize thin films based on this compound on the surface of a dielectric substrate mounted near the electrodes. Numerically solving the Boltzmann kinetic equation for the electron energy distribution function, the temperature and the electron density in the discharge, the specific discharge power losses for the main electronic processes, and the rate constants of the electronic processes depending on the parameter E/N for the plasma of vapor-gas mixtures based on krypton and silver sulfide have been calculated. Homogeneous thin films based on silver sulfide are synthesized on the quartz substrates by the gas-discharge method under conditions of ultraviolet assisted discharge plasma.

In this paper, we study the effect of microwave heating of liquid reagents in a closed-type beam chamber on the intensity of a chemical process in a microreactor. The heating of the reagents, which is uneven along the length of the microreactor, is shown to stimulate the development of thermocapillary convection and significantly intensifies the chemical process. The maximal velocities of thermocapillary motion developed at the interphase boundary of contacting liquids depending on the specific power of internal heat sources and the longitudinal temperature gradient is numerically estimated.

Pure nickel (Ni) coatings and nickel–vanadium pentoxide (Ni–V₂O₅) nanocomposite coatings have been developed on the mild steel substrates by the direct current (DC) and pulse current (PC) methods of electrodeposition using a sulfamate electrolyte bath by optimizing all of the suitable parameters. The surface morphology and texture characterization of pure Ni coatings and Ni–V₂O₅ nanocomposite coatings were analyzed by spectroscopic techniques such as scanning electron microscopy (SEM) equipped with an attachment for energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) spectroscopy analyses. The SEM study confirmed surface morphology of the pure Ni coating was changed by the incorporation of V₂O₅ nanoparticles in the nickel metal matrix and chemical composition of all the coatings was determined by EDS. The XRD study proved highly corrosion resistant nanocomposites show preferred orientation towards (111) plane. The corrosion rate of all the coatings was investigated in a 3.5% corrosive medium using electrochemical techniques such as Tafel extrapolation and AC impedance. The coatings developed by PC showed an enhanced corrosion resistance behavior compared to that of the coatings developed by DC. The 0.125 g/L Ni–V₂O₅ nanocomposite coating obtained by PC showed more widened semicircles with a high R_p value and a more positive shift with high corrosion resistance during the AC impedance and Tafel extrapolation analyses respectively. The coatings developed by PC showed improved microhardness compare to that of the coatings developed by DC during microhardness testing of all studied coatings.

This paper presents the theory of surface electronic states induced by a high-voltage field and considers applications of the theory of surface electrons (SEs) to electrohydrodynamic flows. Theoretical considerations are carried out within the framework of a one-electron quantum mechanical model. It is shown that SEs initiate the injection of negative charges from the cathode into a liquid dielectric containing an electron-acceptor impurity, for example, molecular iodine. The comparison of the theoretic and experimental data is satisfactory.

The results of an approximate calculation of the maximal value of the quantum number of n = n_m for the quantized standing longitudinal electron de Broglie half-waves λ_ezn/2 = l₀/n long and, accordingly, of the maximal number of n_m of the quantized zones of the longitudinal periodic localization with the length Δz_nh of the drifting free electrons in the cylindrical conductors of finite size (l₀ in length and r₀ in radius) with the axial conduction current i₀(t) of the indicated kinds and the amplitude and time parameters (ATPs) are presented, taking into account the quantum-wave nature of the electric conduction current i₀(t) of different kinds (direct, alternating, and pulse) and ATPs in the metal conductors. The results of a verification of the calculated quantum-mechanical relationship to determine the quantum number n_m confirm its validity in such areas of engineering as high-voltage high-current pulse equipment and the electrophysical processing of metals by a strong electromagnetic field and by the pressure of a large pulse current.

This article deals with reactions occurring under the action of active particles formed during the flash of a corona electric discharge between a solid electrode and the surface of a liquid—electrochemical reactions without an electrode. Reactions take place in a thin surface layer of water, where there are no electrodes, so the reactions are called electrodeless. The electrodes are used only to excite the reaction zone and do not directly participate in the reaction. The oxidation of organic compounds to carbon dioxide and water occurs in an electrodeless reaction.