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.

Electrochemical Formation of Oxide Films on the Titanium Alloy of Ti6Al4V in Ethylene Glycol-Water Electrolytes to Produce Bioinert Coatings and Increase the Corrosion Resistance of Medical Implants

The research data on the specific features of the formation of oxide films on the Ti6Al4V alloy in the ethylene glycol-water electrolytes have been given. The kinetic dependences obtained for the alloy allowed us to establish that the specific features of the formation of oxide films during the electrochemical oxidation of the alloy surface depend on the solution composition and the current density. For the water-to-alcohol ratio of 50:50 the kinetic dependences show the sections that correspond to the formation of the barrier oxide layer and also to the formation of the pores due to the desorption of fluoride ions and the growth of the porous portion of oxide. As the water-to- alcohol ratio is decreased the indicated peculiarities of kinetic dependences are met not so often and do not obey any regularity. The obtained data are explained by the fact that an increase in the portion of the organic component of the solution results in a decreased etching capacity of the electrolyte due to the controlled activity of fluoride ions. The anode current density value has a similar effect on the variation of kinetic dependences. Its effect is explained by that an increase in the alloy oxidation rate results in the fast formation of the surface oxide and the specific features of kinetic curves are concealed. The linear relationship between the formation time of oxide of a minimum thickness for given conditions and the current density is unavailable and it is conditioned by the chemical interaction of the oxide film with electrolyte components. The obtained research data can be used for the formation of the individual bioinert and bioactive coatings for the implants of a medical purpose or for the formation of the matrix used for the production of composite coatings.

The effect of impurities on the stability of low concentrated eco-friendly solutions of NaOCl

The synthesis of hypochlorous acid from low concentrated chloride-containing electrolytes has been studied on various oxide materials at the anode current density of 50 mA cm–2. Boron doped diamond, platinized titanium, metallic titanium doped with platinum and palladium and materials based on lead (IV) oxide modified with fluorine and surfactants turned out to be promising for the synthesis of hypochlorous acid by electrolysis. Whereas, given the stability of oxidant synthesis during cumulative electrolysis, titanium modified with platinum and palladium as well as pre-treated lead (IV) oxide containing surfactants (sodium laureth sulfate) was the best. One should additionally take into account the possibility of combined use of electrocatalysts for the synthesis of strong oxidants in the reverse current mode in flow systems, when the implementation of the gas cathode leads to the formation of hydrogen peroxide and hypochlorous acid is formed at the anode. In fact, only a metal electrocatalyst, such as titanium modified with platinum and palladium, can be a suitable material. The kinetics of hypochlorite conversion is primarily determined by the pH value of freshly prepared solutions, temperature and storage conditions. The presence of different organic and inorganic micro-impurities in the solution also affects the kinetics of the hypochlorite salt decomposition. The following micro-impurities show the most negative impact on the stability of sodium hypochlorite solutions: Co(II), Cu(II), Mg(II), Al(III), and K3[Fe(CN)6]; Ni(ІІ), Fe(III), and K4[Fe(CN)6] influence the stability to a lesser extent. The effect of chlorate on the inhibition of sodium hypochlorite activity as a disinfectant has been investigated. The presence of chlorate in the disinfectant solution involved results in the absence of bactericidal activity against S. aureus and P. aeuruginosa. The growth of pseudomonas colonies becomes more abundant with increasing chlorate content in the disinfectant.

Influence of dipinaconborates on the corrosion resistance of ST3 steel in synthetic detergent solutions

Experimental data on the effect of lithium dipynaconborates (DPKBL), sodium (DPKBN) and potassium (DPKB) on the corrosion resistance of St3 steel in 3 % aqueous solutions of Labomid-203, MS-8 and Temp-100A synthetic detergents have been obtained. By measuring the stationary potentials of steel in solutions of synthetic detergents, the optimal concentration of dipinaconborates was revealed, which is 20 g/l, at which the highest corrosion resistance of steel is achieved. Studies of the corrosion-electrochemical behavior of St3 steel in 3 % aqueous solutions of Labomid-203, MS-8 and Temp-100A detergents showed that in the presence of dipinaconborates, the anode current density, at the same potentials, is much lower, and the passivation region is larger. than in CMC solutions. It was found that the corrosioninhibiting ability of dipinaconborates in CMC solutions increases in the series DPKBL < DPKBN < DPKBK, and potassium dipinaconborate has the greatest anticorrosive property. Dipinaconborates reduce the corrosion rate of steel at a washing solution temperature of 80 °C, the degree of protection is in the range from 71.4 to 90.6 %. And the braking coefficient is from 3.6 to 10.4. By analyzing the obtained experimental data, it was concluded that dipinaconborates increase the corrosion resistance of St3 steel and can be recommended as an anticorrosive additive to synthetic detergents.

Formation and Characterization of Dispersed Mixed Iron-titanium Oxide Systems by Electrochemical Method

Aims: Anodic polarization behavior of a combined iron-titanium electrode (two metals in electrical contact with each other) in aqueous solutions containing halide ions (F- and Cl-) was studied. Methods: he joint anodic dissolution of titanium and iron with subsequent thermal treatment makes it possible to obtain precursors of a highly dispersed mixed oxide system Fe2O3-TiO2. The phase and elemental composition and structural characteristics of obtained products were examined using X-ray diffraction and scanning electron microscopy. It has been experimentally confirmed that via changing the anode current density, hydrofluoric acid concentration in electrolyte and ratio of the working surface area of contacting metals, it is possible to effectively control the rate of anodic reactions and phase composition and morphology of anodic oxidation products for iron and titanium components in a combined electrode. Results: The main results of this study are as follows: Electrochemical method for the synthesis of complex dispersed oxide system Fe2O3-TiO2 based on joint anodic oxidation of contacting metals in aqueous media was suggested. Relationships between parameters of the electrochemical process and characteristics of the synthesized oxide system were revealed. Conclusion: By varying the parameters of the electrolysis process, it is possible to prepare complex oxyhydroxides with different ratios of iron and titanium, which makes it possible to synthesize precursors of iron titanates of preset composition and structure.

Study on Intensification Behavior of Bismuth Ions on Gold Cyanide Leaching

Gold cyanide leaching is inefficient with conventional cyanidation. Bismuth ions can improve the efficiency of gold cyanidation by intensifying gold dissolution. The electrochemical behavior, structure information, and surface product of gold anodic dissolution were studied during the intensification of bismuth ions on gold cyanide leaching. The electrochemical analysis showed that the bismuth ions can not only improve anode current density, but also make gold dissolve at a lower potential, increase the corrosion current and intensify gold anodic dissolution. The microstructure analysis showed that bismuth ions intensified the cyanide corrosion of the gold surface, causing a large number of loose honeycombs, gullies, pits, and large holes on the gold surface. The XPS, FT-IR, and Raman analysis showed that there is weak information of C≡N in the spectrum of Bi intensification contrasting to that of conventional cyanidation. Cyanide compounds may be the insoluble AuCNads, which does not deposit on the surface of gold plate after Bi intensification cyanidation. The insoluble intermediate AuCNads is likely to react promptly with CN- to form soluble Au(CN ) 2 − , making less insoluble AuCNads deposits on the gold surface. Therefore, bismuth ions can promote the dissolution of insoluble AuCNads, prevents its passivation film to cover around the gold plate, keeps cyanide good contact with gold, and finally accelerates the cyanide dissolution of gold.

Зависимость свойств вариативных градиентно-пористых структур кремния от метода формирования

A series of samples of gradient-porous silicon structures with crystallographic orientations (100) and (111) by deep anode etching was obtained. Dependences of the rate of deep anodic etching and the depth of the porous layer of the samples on the anode current density are shown. The absorption and reflection coefficients of the samples were investigated by optical spectrometry depending on their crystallographic orientation and the depth of the porous layer. The influence of water solutions on the optical properties of the samples was determined.

Influence of hard alloys CEDG modes on the size of dissolved layer

Correctly assigned technological modes of processing define the accuracy of forming, optimum mechanical and electrochemical speed of the processed material removal, quality and durability of the cutting tool as well as provide the self-sharpening conditions for the grinding wheel. The purpose of this work is to increase the efficiency of hard alloys combined electric diamond grinding (CEDG) by establishing a dependence between the amount of material removed by mechanical cutting and the depth of the layer dissolved by electrolytic processes. Achieving the stated goal allows to solve the problem of defects occurrence on the processed surface and to minimize economic expenses for machine-building production processing. The article presents the results of mathematical calculations of the parameters influence on the size of the dissolved surface layer, as well as the current dependent removal rate for hard alloys. We determine qualitative and quantitative characteristics of the hard alloy dissolved layer dependence on the mechanical and electrical parameters of CEDG, such as the depth of grinding and anode current density, and demonstrate their analytical dependence.

Simulation Study of Switching-Dependent Device Parameters of High Voltage 4H-SiC GTOs

The silicon carbide (SiC) “Super” gate turn-off thyristor (SGTO) is a viable device for high voltage and fast dI/dt switching applications. These devices are well suited for various pulsed power applications requiring high peak currents in the kilo-amp regime. The turn-on transition speed is determine by the spreading velocity, which depends on applied gate current, applied anode current density, minority carrier lifetime, and both the gate base-width and the drift region of the thyristor. The impact of device parameters on switching performance is discussed in this work.