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Документ Chemical deposition of CdS films from ammoniac-thiourea solutions(Технологический центр, 2018) Pancheva, Hanna; Khrystych, Olena; Mykhailova, Evgeniia; Ivashchenko, Maryna; Pilipenko, AlexeiThis paper investigates the process of chemical deposition of CdS films from ammonia-thiourea solutions. It was established that a change in the turbidity of solution occurs in the process of chemical deposition. The results of visual observations and measurement of turbidity of solution allowed us to establish that these dependences could be used to monitor the status of the process. Visual observations correlate with the obtained dependences for turbidity and suggest that the chemical deposition of CdS includes the accumulation of colloidal-dispersed precipitate in the volume of solution, agglomeration of CdS particles, and a stationary mode of the CdS film growth at the surface of a sample. The first stage of the process is matched by a sharp increase in the turbidity of solution; the second stage is accompanied by the emergence of a maximum in the dependence. No significant change in turbidity occurs at the third stage. The observation of morphology of the resulting precipitate allowed us to establish working concentrations of reagents in solution, which ensure obtaining a high-quality CdS film with a thickness not less than 100 μm. The working concentrations of cadmium chloride, ammonia, and thiourea are, respectively, 1.8, 0.6, and 8.4 g·l⁻¹. It was assumed that the CdS formation is accompanied by the formation of thiourea. This is confirmed by data on the analysis of a working solution. An analysis of the solution revealed high concentrations of the CO₃²⁻ ions, which are a product of the thiourea decomposition. The data obtained are a preliminary stage in the development of a technology of chemical deposition of CdS films from ammonia-thiourea solutions.Документ Study of anode processes during development of the new complex thiocarbamide-citrate copper plating electrolyte(Технологический центр, 2018) Smirnova, Olha; Pilipenko, Alexei; Pancheva, Hanna; Zhelavskyi, Alexei; Rutkovska, KaterynaThe kinetics of anodic reactions occurring on copper in thiocarbamide-citrate solutions was studied. Thiocarbamide forms stable copper (I) complexes of the cationic type with a coordination number equal to unity. Citric acid ensures acid pH value of electrolyte and causes active dissolution of copper under conditions of anode polarization. The joint presence of CS(NH₂)₂ and C₆H₈O₇ in the solution contributes to the copper electrode activation under conditions of anodic polarization. Increasing the concentration of thiocarbamide leads to a drastic shift of copper dissolution potentials towards the region of negative values. Study of the kinetics of anodic behavior of copper by acquiring the voltammograms revealed the nature of the limiting stage of reaction. It is shown that the process of dissolution in a thiocarbamide-citrate electrolyte is controlled by the diffusion phase. This is confirmed by the results of graphical processing of polarization dependences in coordinates η–lg(1–ja/jd). An increase in υр within 5‒100 mV·s⁻¹ causes an increase in jd from 2.2 to 12.0 mА·cm⁻², which indicates diffusion control over the process. The process of copper dissolution proceeds under stationary mode with uniform etching of intragrain boundaries and volume of the metal's grain.Документ Study into the influence of concentration of ions of chlorine and temperature of circulating water on the corrosion stability of carbon steel and cast iron(Технологический центр, 2017) Pancheva, Hanna; Reznichenko, Ganna; Miroshnichenko, Nataliya; Sincheskul, Alexander; Pilipenko, Alexei; Loboichenko, ValentynaThe impact of the chloride ions concentration and the temperature of the circulating water on the process of corrosion destruction of carbon steel and cast iron has been investigated. It has been shown that an increase in the concentration of chloride ions causes a shift in the values of the stationary potentials of steel and cast iron to the region of negative values and reduces the passive state of these alloys. This leads to an increase in the corrosion rate of St.3 steel and CI 18-36 cast iron. The results of electrochemical studies have shown that the more reliable protective films are formed on steel than on cast iron. The limiting concentration of NaCl, at which reliable operation of equipment made from these alloys is possible, depends on the pH of the solution. At pH=7, it is about 1.2 g l⁻¹, which is about an order of magnitude less than at pH=12. When the circulating water temperature rises, the corrosion rate of steel and cast iron increases. The stationary potentials of steel and cast iron are shifted to the negative range, and the polarization of the anode process decreases. Corrosion process is limited by the rate of oxygen supply to the cathode areas.Документ Establishing the patterns in the formation of oxide films on the alloy Ti6Al4V in carbonic acid solutions(Технологический центр, 2018) Ivashchenko, Maryna; Smirnova, Olha; Kyselova, Svitlana; Avina, Svetlana; Sincheskul, Alexander; Pilipenko, AlexeiThis paper reports results of studying the features of the formation of thin interference-colored oxide films on the alloy Ti6Al4V alloy in solutions of carboxylic acids. It has been established that a change in voltage on the cell corresponding to the molding dependence of the alloy depends on the anodic current density. At current densities <0.5 A∙dm⁻², a continuous oxide film is not formed at the alloy surface and the assigned voltage value is not reached. An increase in current density to values higher than 0.5 A∙dm⁻² predetermines a linear change in voltage over time with followed by reaching the assigned magnitude U. The maximum film thickness for these conditions is defined by the voltage magnitude and does not depend on the electrolysis mode. Color of the oxide film is defined by the specified value for the molding voltage and does not depend on current density, nature and concentration of carboxylic acid. A match between the molding dependences of oxidation obtained in different electrolytes suggests that the formation of oxide proceeds in line with the same mechanism. The obtained data are explained by the fact that the formation of oxide under the galvanic static mode takes place under conditions of the presence of a constant potential gradient in the oxide film. An increase in the voltage magnitude applied to the cell predetermines a proportional increase in the maximum oxide thickness, since it leads to an increase in the amount of electricity passed through the cell and a corresponding increase in the mass of the oxidized metal. Results of the study into determining the effect of the nature of carboxylic acid on the formation process of an oxide film on the alloy Ti6Al4V using the method of electrochemical oxidation have demonstrated that the nature of the electrolyte does not affect the characteristics of its formation. The obtained data allow us to suggest that the choice of an electrolyte for the development of a technology for electrochemical oxidation of titanium implants should be based on the results of studying the functional properties of the obtained coatings.Документ Design of the modified oxide-nickel electrode with improved electrical characteristics(Технологический центр, 2017) Sincheskul, Alexander; Pancheva, Hanna; Loboichenko, Valentyna; Avina, Svetlana; Khrystych, Olena; Pilipenko, AlexeiThe influence of lithium hydroxide was examined on the characteristic features of charge and discharge and electrical parameters of the sintered oxide-nickel electrode in a solution of potassium hydroxide. It is shown that the introduction of LiON to the composition of electrolyte does not lead to a change in the specificity of charge and discharge processes of the electrode. The experimental work conducted allowed us to establish dependences that connect the magnitude of analytical concentration of the Li⁺ ions to specific capacity and capacity output of the electrode. The results obtained show that an increase in the content of Li⁺ ions in the electrolyte from 1 to 100 g·l⁻¹ causes a growth of the electrode’s specific capacity from 0.79 (А·h)·cm⁻² to 1.84 (А·h)·cm⁻². It is optimal to introduce LiOH to the electrolyte in the amount of 30‒50 g·l⁻¹. It was established that the magnitude of specific capacity of the oxide-nickel electrode depends on the number of charge-discharge cycles and increases with an increase in the number, which is related to the slow character of the course of mass transfer processes in the volume of active mass of the electrode.Документ The study of inhibiting structural material corrosion in water recycling systems by sodium hydroxide(Технологический центр, 2017) Pilipenko, Alexei; Pancheva, H.; Reznichenko, G.; Mirgorod, O.; Miroshnichenko, N.; Sincheskul, A.Influence of sodium hydroxide on the rate and nature of corrosion of St3 carbon steel and SCh 18-36 grey cast iron in highly mineralized recycling water was studied. The nature of the corrosion damage was determined and the weight index of corrosion of these alloys was calculated. By means of polarization measurements, the electrochemical indices of anodic processes on steel and cast iron were determined. The effect of the circulating water pH on behavior of steel and cast iron under anodic polarization has been studied by cyclic voltammetry. It has been shown that the effective impact of pH on characteristics of the anode processes occured at pH≥11.4. At these pH values, the metal steady-state potential shifted to a region of positive values which was an indication of inhibition of the anodic process itself. At pH≥11.4, the pitting potential significantly shifted to the positive side: the process of healing pits was faster than their formation. It has been established that steel and especially cast iron tend to pass into a passive state at pH> 10. The corrosion rate values did not exceed this index for the studied alloys in distilled water and were in the range of acceptable values. Thus, it is possible to effectively inhibit the rate of steel and cast iron corrosion, especially in the waterline zone by shifting the pH of the circulating water to the alkaline region. As a result of the conducted studies, optimal working conditions for iron alloys as the most technically important structural materials for designing closed cycles of circulating water supply systems have been established.