Browsing by Author "Popova A.K."

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    TEMPERATURE EFFECT ON THE ELECTROCHEMICAL IMPEDANCE SPECTRA IN PRESENCE OF QUATERNARY AMMONIUM BROMIDES IN ACID MEDIA
    (2023-01-01) Popova A.K.; Vasilev A.A.
    The inhibitive properties of two quaternary ammonium bromides are studied in respect to mild steel corrosion in 1 M HCl in the temperature range of 30°C - 60oC. Both compounds are synthesized for this particular purpose and are investigated as inhibitors for the first time. Their inhibitive properties are verified by two methods - those of the alternating current method of the electrochemical impedance spectroscopy (EIS) and the direct current method of the polarization resistance (Rp-method). It is found that the temperature affects the frequency dispersion of the interface impedance in presence of both compounds. Two structural models are advanced describing the impedance data. They present the processes at mild steel/1 M HCl + an inhibitor interface at various temperature values. The quantitative analysis of the electrochemical impedance spectra is based on the physical model of electrochemical corrosion with hydrogen depolarization controlled by a charge transfer step. The double layer capacitance is modeled by a frequency distributed element Constant Phase Element (CPE). The adsorption capacitance is also modeled by CPE. The values of the electrochemical parameters referring to both inhibitors in the temperature interval studied are calculated on the ground of the models derived. The values of the resistances obtained by EIS method are compared to those of the polarization resistance RDCp. A very good coincidence is observed. The inhibitive effect of the compounds studied is estimated. A tendency of increase of the protective effect with temperature increase is observed. Both compounds have very good and similar protective properties. Those of the oxazole compound are slightly better.
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    THE STUDY OF MANGANESE PHOSPHATE MATERIALS BASED ON ENRICHMENT WASTES
    (2022-01-01) Raimbekova A.S.; Kapralova V.I.; Popova A.K.; Kubekova S.N.
    The work highlights the study on chemical and phase composition of stripping waste and manganese ore tailings at Zhairem deposit. It was shown that the overburden rocks have a complex mineral composition and contain 14.6 wt. % manganese in (Mn2O3)3MnSiO3 in braunite form. Enrichment tailings are represented mainly by 76.4 wt. % calcite and contain 2.4 wt. % of braunite. On the basis of manganese ore concentration wastes in the temperature range of 200°C – 800°C, phosphate materials were synthesized due to an acid-thermal method. Alongside, their composition and aqueous solubility were studied as well. It was shown that the product synthesized at 200°C contains mainly acidic and medium diphosphates of calcium, silicon and manganese (III) monophosphate. The mentioned product has a high aqueous solubility of 92.4 %. Increasing the synthesis temperature to 400°C and 600°C grows the depth of phosphate anion dehydration process, and results in the formation of poorly soluble calcium polyphosphates Ca(PO3)2 and trivalent manganese Mn(PO3)3that partially turn into a glassy state at 800°C.