Predrag Živković

Electrodeposition of bismuth from an acidic nitrate solution on copper electrodes by use of the potentiostatic mode of electrodeposition has been investigated with the aim to define conditions for obtaining dendritic forms. Morphology and structure of Bi deposits produced at the different cathodic potentials were featured by techniques of scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS) and X-ray diffraction (XRD), and correlated with the polarization features. The Bi dendrites were formed starting from the plateau of the limiting diffusion current density, while granules were formed at the cathodic potential which preceded the plateau. The shape of dendrites changed from very compact, formed at the plateau, to highly branched, formed at cathodic potentials beyond the plateau of the limiting diffusion current density, where the current density continuously grew with the increase in the cathodic potential. Both granules and dendrites showed the forceful preferred orientation in the basal (003) crystal plane with the lowest surface energy. The performed morphological and structural analysis classified Bi into a group of so-called normal metals, characterized by high values of both the exchange current density and overpotential for hydrogen evolution reaction and by low melting points.

Cathodic electrodeposition of copper on molybdenum and stainless-steel substrates has been investigated with the aim of examining their potential to produce thin copper foils (TCFs). Copper in the form of a thin film was electrodeposited galvanostatically from the acidic sulfate electrolyte without and with an addition of suppressor/activator additives, such as chloride ions, polyethylene glycol 6000 and 3–mercapto–1–propanesulfonic acid. The cathodes and electrodeposited Cu films were characterized by SEM, AFM, and XRD techniques, while the adhesion of Cu films, as a crucial parameter in the production of Cu foils, was estimated by a lab-made prototype of a bending test machine made by applying additive technology. The adhesion parameter named “critical cycle number” (n_c), which defines the minimal number of cycles leading to a delamination (separation) of the film from the cathode was used for assessing the adhesion features of the films. The easiest delamination, i.e., the smallest n_c, showed nanocrystalline films obtained with the addition of all additives, whereupon the values were significantly smaller than the values obtained for microcrystalline films obtained without and with a partial combination of the additives. The easy delamination of the nanocrystalline films indicated that both substrates have a high potential for application in the production of TCFs.

Influence of parallel hydrogen evolution reaction (HER) on morphology of zinc electro­deposits has been investigated. Zn was electrodeposited potentiostatically from the alkaline electrolyte at overpotentials both inside and outside the plateau of the limiting diffusion current density, and scanning electron microscopy (SEM) was used to characterize the resulting deposits. Holes originating from detached hydrogen bubbles were formed among the branchy, fern-like dendrites at overpotentials outside the plateau of the limiting diffusion current density, while HER was not detected at the overpotential inside the plateau. The overpotential of electrodeposition had no significant effect on the amount of hydrogen produced (the HER current efficiency was in the 17.7-19.1 % range), but it did affect the hole size. Depending on the overpotential of the electrodeposition, the size of holes was from several to about 100 mm, including those obtained by a coalescence of neighbouring hydrogen bubbles, and decreased with the increasing overpotential. The absence of inhibition of dendritic growth in spite of a high value of evolved hydrogen was attributed to Zn, which belongs to the group of normal metals characterized by high values of both the exchange current density and the overpotential for hydrogen evolution.

The anodic oxidation of titanium implants is a practical, cost-effective method to enhance implant success, especially due to rising hypersensitivity concerns. This study investigated the electrochemical behavior, surface characteristics, and biocompatibility of anodized commercially pure titanium (cpTi, grade IV). Anodization is performed on polished, cleaned cpTi sheet samples in 1 M H₂SO₄ using a constant voltage of 15 V for 15 and 45 min. The color of the oxide layer is evaluated using the CIELab color space, while composition is analyzed by a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS). Additionally, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) are performed to identify and monitor the phase transformations of the formed titanium oxides. Corrosion measurements are performed in 9 g L⁻¹ NaCl, pH = 7.4, and show the excellent corrosion stability of the anodized samples in comparison with pure titanium. The biological response is assessed by determining mitochondrial activity and gene expression in human fibroblasts. Anodized surfaces, particularly Ti-45, promote higher mitochondrial activity and the upregulation of adhesion-related genes (N-cadherin and Vimentin) in human gingival fibroblasts, indicating improved biocompatibility and the potential for enhanced early soft tissue integration.

Anodic oxidation of titanium implants is a practical, cost-effective method to enhance implant success, especially due to rising hypersensitivity concerns. This study investigated the electrochemical behavior, surface characteristics, and biocompatibility of anodized commercially pure titanium (cpTi, grade IV). Anodization is performed on polished, cleaned cpTi sheet samples in 1 M H2SO4 using a constant voltage of 15 V for 15 and 45 min. The color of oxide layer is evaluated using CIELab color space, while composition is analyzed by Scanning Electron Microscope (SEM) equipped with Energy Dispersive Spectrometer (EDS). Additionally, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) are performed to identify and monitor phase transformations of formed titanium oxides. Corrosion measurements are performed in 9 g L–1 NaCl, pH = 7.4, and shows excellent corrosion stability of the anodized samples in comparison with pure titanium. Biological response is assessed by mitochondrial activity and gene expression of human fibroblasts. Anodized surfaces, particularly Ti-45, promoted higher mitochondrial activity and upregulation of adhesion-related genes (N-cadherin and Vimentin) in human gingival fibroblasts, indicating improved biocompatibility and potential for enhanced early soft tissue integration.

Morphology and crystal orientation of electrolytically produced dendrites of lead, tin, and zinc have been investigated with the aim of establishing any correlation between them. These three metals belong to the same group of metals from an electrochemical point of view (the group of normal metals), but to various types of crystal lattice (Pb - the face-centered cubic type, Sn - the body-centered tetragonal type, and Zn - the hexagonal closed pack type). Pb, Sn and Zn dendrites were produced potentiostatically using the correspond¬ing hydroxide electrolytes and characterized by scanning electron microscopy (morphology) and X-ray diffraction (crystal orientation) techniques. The preferred orientation of the dendritic particles was determined by applying a method based on a comparison of the peak intensity ratios. The fern-like dendrites of various degrees of branchy were obtained by the processes of electrolysis, and regardless of the type of crystal lattice, they exhibited the strong preferred orientation in crystal planes with the lowest surface energy. Based on the performed analysis, a strong correlation between the morphology and the crystal structure of dendrites belonging to the group of normal metals has been established. It is concluded that electrochemical parameters characterized by the high values of the exchange current density (the fast electrochemical processes) prevailed over crystal¬lographic characteristics of metals manifested by the belonging to a determined type of crystal lattice.

The correlation between the morphology and crystal structure of zinc dendritic particles produced by electrolysis from the alkaline electrolyte has been established. Morphology and crystal structure of Zn particles electrodeposited by the potentiostatic regime of electrolysis at overpotentials inside (−100 and −160 mV) and outside (−220, −280, and −340 mV) the plateau of the limiting diffusion current density were characterized by scanning electron microscope (SEM) and by X-ray diffraction (XRD), respectively. The particle size distribution (PSD) was performed in order to determine the dependency of the size of dendritic particles on applied electrolysis overpotential. With increasing the overpotential of electrolysis, the shape of particles changed from irregular forms denoted as precursors of dendrites to various forms of dendrites, while the size of the particles simultaneously decreased. All types of Zn dendrites exhibited the strong (002) preferred orientation, while the precursors of dendrites exhibited (101)(002) preferred orientation. The development of strong (002) preferred orientation was explained and discussed by making an analogy with the electrolytic production of lead dendrites from the concentrated nitrate electrolyte. Although zinc and lead belong to different types of crystal lattice (Pb-face-centered cubic type and Zn-hexagonal close-packed type), they have a common characteristic that is manifested by the strong preferred orientation in the crystal plane with the lowest surface energy.

This study presents an analysis of films which consist of two layers; one layer is PVDF as the matrix, along with fillers BaTiO₃ (BT), and the second is one bacterial nanocellulose (BNC) filled with Fe₃O₄. The mass fraction of BT in PVDF was 5%, and the samples were differentiated based on the duration of the mechanical activation of BT. This innovative PVDF laminate polymer with environmentally friendly fillers aligns with the concept of circular usage, resulting in a reduction in plastic content and potential improvement of the piezoelectric properties of the entire composite. This work presents new, multifunctional “green” packaging materials that potentially could be a good alternative to specific popular materials used for this purpose. The synthesis of the films was carried out using the hot press method. Tensile tests, water vapor permeability examination, and structural analyses using SEM-EDS and FTIR have been conducted. The sample PVDF/BT20/BNC/Fe₃O₄ exhibited the best barrier properties (impermeability to water vapor), while the highest tensile strength and toughness were exhibited by the PVDF/BT5/BNC/Fe₃O₄ sample.

In the search for environmentally friendly materials with a wide range of properties, polymer composites have emerged as a promising alternative due to their multifunctional properties. This study focuses on the synthesis of composite materials consisting of four components: bacterial nanocellulose (BNC) modified with magnetic Fe₃O₄, and a mixture of BaTiO₃ (BT) and polyvinylidene fluoride (PVDF). The BT powder was mechanically activated prior to mixing with PVDF. The influence of BT mechanical activation and BNC with magnetic particles on the PVDF matrix was investigated. The obtained composite films’ structural characteristics, morphology, and dielectric properties are presented. This research provides insights into the relationship between mechanical activation of the filler and structural and dielectric properties in the PVDF/BT/BNC/Fe₃O₄ system, creating the way for the development of materials with a wide range of diverse properties that support the concept of green technologies.