Перегляд за Автор "Pancheva, H."
Зараз показуємо 1 - 5 з 5
Результатів на сторінці
Налаштування сортування
Документ Carbon Steel (St.3) Corrosion Caused by the Circulating Water Flow(Kyiv National University of Technologies and Design, 2018) Pilipenko, A. I.; Pancheva, H.; Khrystych, E. V.; Smirnova, O. L.Документ Electrochemical oxidation of VT6 titanium alloy in oxalic acid solutions(2020) Pilipenko, A.; Maizelis, A.; Pancheva, H.; Zhelavskaya, Yu. A.The influence of the electrolysis parameters on the process of VT6 titanium alloy oxidizing in oxalic acid solutions is presented. It is shown that the nature of cell voltage-time curves for the alloy samples depends on the current density used. The interference-colored oxide films are formed on the surface of the alloy at the anodic current density above 0.5 A∙dm⁻². The maximal thickness and the oxide film color are determined by the cell voltage and do not depend on other electrolysis parameters. The results of oxidation in oxalic and sulfuric acids solutions made it possible to establish the similarity of cell voltage-time dependencies and the time of oxide film formation with maximal thickness for these electrolysis conditions.Документ Examining the efficiency of electrochemical purification of storm wastewater at machine building enterprises(PC Tесhnology сеntеr, 2018) Maksimenko, O.; Pancheva, H.; Madzhd, S.; Pysanko, Y.; Briankin, O.; Tykhomyrova, T.; Hrebeniuk, T.We have examined the composition of polluted storm water discharged from the territory of a machine building enterprise. It was established that the territory was unevenly polluted, with the surface wastewater from the area adjacent to the production shops dominated by ions of copper, to 1.1 mg/dm³; zinc, to 2.0 mg/dm³; nickel, to 1.6 mg/dm³; chromium, to 0.93 mg/dm³, and lead, to 5.0 mg/dm³. It was found that the removal of metals’ ions during electrocoagulation treatment is significantly influenced by the following factors: a flow rate of the wastewater sent for purification; duration of wastewater settling upon electrocoagulation, and current density during electrolysis. We have defined optimal parameters for the wastewater treatment process. Based on experimental research, we have built graphic dependences of purification effectiveness on current density and water settling time. The optimal parameters were determined for the wastewater treatment process, which ensure sufficiently high efficiency of water purification from heavy metals’ ions (to match the values for discharge standards) at an acceptable amount of electricity. It was established that the best conditions for deposition of nickel and lead are a current density of 50 A/m³ and a time of settling after electrocoagulation of 9 hours. The optimal conditions for depositing copper and zinc are 12 hours, and it is possible to lower the concentration of chromium to safe concentrations at a current density of 10 A/m³ and a time of settling of 4 hours. It was revealed that the effectiveness of purification from metals’ ions increases significantly with an increase in the current density and settling time; in addition, the efficiency of settling is 1.4‒3 times higher than the increase in current density. It is shown that prolonging the time of settling might not always compensate for the decrease in current density during electrocoagulation, which requires selecting the optimal balance of all factors. The experimental data that we acquired are necessary to calculate the technological process parameters. By applying a method of fullfactor experiment, we have constructed mathematical models of the process, which include the dependence of response (the residual concentration) on the aboveenumerated factors. The proposed models could make it possible to control the process of electrocoagulation by influencing those factors on which the efficiency of purification depends.Документ Formation of oxide fuels on VT6 alloy in the conditions of anodial polarization in solutions H₂SO₄(Технологический центр, 2018) Pilipenko, Alexei; Pancheva, H.; Deineka, V.; Vorozhbiyan, R.; Chyrkina, M.Наведенi результати дослідження процесу електрохімічного оксидування титанового сплаву ВТ6 у розчинах H₂SO₄. Показано, що характер залежностей формовки зразків сплаву залежить вiд величини густини струму. При j<0,5 А.дмˉ² суцiльна оксидна плiвка на поверхнi сплаву не утворюється i задане значення напруги не досягається. При j>0,5 А.дмˉ² на поверхнi сплаву утворюється суцiльна оксидна плівка та спостерігається лiнiйна характер залежностей. Плiвки, одержанi в цих умовах, вiдносяться до інтерференційно-забарвлених. Гранична товщина плівки визначається заданою величиною U i не залежить вiд iнших параметрiв електролiзу. Для ряду однакових значень U залежнiсть τ–j має лiнiйну форму. Колір оксидної плiвки визначається значенням напруги i не залежить від густини струму та концентрацiї електролiту. Встановлена вiдповiднiсть кольору плiвки i величини U в діапазоні значень 10-100 В. Ефект пояснюється тим, що утворення плівки при анодній поляризації відбувається в умовах наявності градієнта потенціалу, величина якого для титану постiйна. Збільшення заданої величини U призводить до пропорційного збільшення максимальної товщини оксиду, яка визначає колір її забарвлення. Результати дослідження з визначення впливу параметрів електролізу на характеристики оксидних плівок дозволили обґрунтувати режим отримання плівок TiO₂ на поверхнi сплаву ВТ6. Отримані данi є передумовою для розробки технології електрохімічного оксидування титанових імплантатів для надання їх поверхнi функцiональних властивостей.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.