Технолошки факултет [Научни радови] / Faculty of Technology [Scientific papers]

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    Ceria Particles as Efficient Dopant in the Electrodeposition of Zn-Co-CeO2 Composite Coatings with Enhanced Corrosion Resistance: The Effect of Current Density and Particle Concentration
    (MDPI, 2021) Riđošić, Marija; Bučko, Mihael; Salicio-Paz, Asier; García-Lecina, Eva; Živkovic, Ljiljana S.; Bajat, Jelena B.
    Novel Zn-Co-CeO2 protective composite coatings were deposited successfully from chloride plating solutions. Two different types of ceria sources were used and compared: commercial ceria powder and home-made ceria sol. Electrodeposition was performed by a direct current in the range of 1–8 A dm􀀀2. Two different agitation modes were used and compared, magnetic stirring and ultrasound-assisted stirring (US). The influence of magnetic stirring on the stability of the related plating baths was evaluated via a dynamic scattering method. The results pointed to better stability of the prepared ceria sol. The morphology of the composite coatings was examined by scanning electron microscopy (SEM), and particle content was determined by energy-dispersive X-ray spectroscopy (EDS). The results showed that the increase in the deposition current density was not beneficial to the coating morphology and particle content. The corrosion behavior of the Zn-Co-CeO2 composite coatings was analyzed and compared by electrochemical impedance spectroscopy and polarization resistance. The ultrasound-assisted electrodeposition at small current densities was favorable for obtaining composite coatings with enhanced corrosion stability. The protection was more effective when US was applied and, additionally, upon utilization of ceria sol as a particle source, which was revealed by higher polarization resistance and greater low-frequency impedance modulus values for sol-derived composite coatings deposited under ultrasound.
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    Morphology and growth of electrodeposited silver powder particles
    (Elsevier, 2007) Maksimović, V. M.; Pavlović, Lj. J.; Tomić, M. V.; Jović, V. D.
    The effect of overpotential pulsing and periodic current reversal on the morphology of silver powders was investigated using a scanning electron microscope (SEM). It is shown that the profile of pulses or current reversal determines the micromorphology of the electrodeposited silver particles. Generally, three forms of silver were detected: (1) dendrites, (2) equiaxial crystals (independent and/or agglomerates) and (3) rods. The shape of particle seems to be the result of an interplay between the surface energy and growth kinetics.
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    Lead and silver extraction from waste cake from hydrometallurgical zinc production
    (Serbian Chemical Society, 2008) STANOJEVIĆ, DUŠAN, D.; RAJKOVIĆ, MILOŠ, B.; TOŠKOVIĆ, DRAGAN, V.; TOMIĆ, MILANA, A.
    This paper presents the experimental results of the extraction of lead and silver from a lead-silver waste cake obtained in the process of hydrometallurgical zinc production. While controlling the pH value, the lead-silver cake was leached at a temperature close to boiling point in different concentrations of aqueous calcium chloride solutions. The experiments were performed applying different ratios between the mass of cake and the volume of the leaching agent under different durations of the process. It was concluded that at the optimal process parameters (pH 2.0-2.5; CaCl2 concentration, 3.6 mol dm-3; temperature, 95°C; solid/liquid ratio, 1:5), the leaching efficiency of lead and silver could reach the approximate value of 94 %. Applying the same optimal process parameters, the method was applied to the leaching of a lead-silver cake in a magnesium chloride solution, but with significantly lower efficiencies. The results show that leaching of lead and silver in a calcium chloride solution could be a prospective method for increasing the recovery of lead and silver during hydrometallurgical zinc production.
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    (Technical Faculty in Bor, Serbia, 2008) Mićić, V.; Lepojević, Ž.; Mandić, B.; Jotanović, M.; Tadić, G.; Tolić, A.
    The supercritical fluid extraction (SFE) by carbon dioxide (CO2) of Salvia officinalis L. was investigated. SFE by CO2 was performed at different pressure (80, 100, 150, 200 and 300 bar) and constant temperature of 40ºC (all other extraction conditions, such are flow rate, particle diameter of Salvia officinalis, extraction time were kept constant. The GC – MS method was used for determination of qualitative and quantitative composition of obtained extracts and essential oils.
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    Selective Absorption in Twolayered Optic Films
    (American Scientific Publishers, 2009) Pelemiš, S. S.; Šetrajčić, J. P.; Markoski, B. S.; Delić, N. V.; Vučenović, S. M.
    This paper summarizes theoretical investigations of changes in optical properties of smallest symmetrical nanofilm-molecular crystals due to the presence of boundaries and different boundary parameters. Using analytic and numerical calculations, the energy spectrum of excitons was found and relative permittivity of these ultrathin dielectric films was determined. The influence of boundary parameters on the occurrence of discrete (by parameters)and selective (by planes)absor ption of external electromagnetic radiation was also investigated. Because of the symmetric conditions on film boundaries, double resonant peaks appear.