1. Microstructure characterization of Al-alloy AW 5454 intended for ecological laser hybrid weldingMatjaž Balant, Rebeka Rudolf, 2024, review article Abstract: This article presents the microstructure characterization of Al-alloy AW 5454, which is intended for laser hybrid welding. In the first part, the procedure of laser hybrid welding is described and compared to other laser surface modification techniques. Subsequently, key methods of metallographic characterization and hardness measurements at selected locations of Al-alloy AW 5454 are presented, enabling a scientific evaluation of the obtained results. The goal of the research was to gain insight into the microstructure of Al-alloy AW 5454, which will, in the future, make it possible to determine the technological parameters of laser hybrid welding that have the greatest influence on the final microstructure and, consequently, on the properties of the weld.
Keywords: Al-alloys, laser treatment, characterization, misrostructure, hardness
Published in DKUM: 14.01.2026; Views: 0; Downloads: 1
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2. The environmental impact of using gold nanoparticles and 3HFWC in cosmetics, as determined with LCA methodologyRebeka Rudolf, Peter Majerič, Žiga Jelen, Andrej Horvat, Damjan Krajnc, 2024, original scientific article Abstract: This review provides a detailed inventory analysis of the manufacturing process of a cosmetic cream using gold nanoparticles (AuNPs) and hydroxylated fullerene water complex (3HFWC) as novel nanocomponents for cream. The inventory analysis was focused on the evaluation of the two raw materials of the nanocomponents, the consumption of electricity and water, which enabled an insight into the process flows within the production process. The data obtained from this analysis of the inventory of nanocomponents provide an insight into the potential improvements that can be made in the manufacturing process of nanocomponents, in order to reduce the environmental impact of the production of new cosmetic creams. These results will serve as the basis for the second part of the analysis, where a life cycle analysis will be carried out to assess the environmental impacts of cream production from the acquisition of raw materials to the disposal of the final product.
Keywords: life cycle analysis, gold nanoparticles, hydroxylated fullerene water complex, cosmetics, environmental impact
Published in DKUM: 13.01.2026; Views: 0; Downloads: 0
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3. Survey and challenges of dental metallic materialsKarlo Raić, Rebeka Rudolf, Vojkan Lazić, Peter Majerič, 2024, review article Abstract: The classification of dental metallic biomaterials is illustrated in depth, with a focus on dental casting alloys. Methods for creating dental prostheses as well as manufacturing shape memory alloys (SMA) Ni-Ti alloys are briefly given. The effect of surface oxide films on metallic biomaterials in the human environment is considered. In order for metal implants to interact with the human body, they need to meet certain requirements.
Keywords: dental metallic alloys, classification, creating dental prostheses, manufacturing SMA Ni-Ti Alloys, surface oxide films, requirements
Published in DKUM: 13.01.2026; Views: 0; Downloads: 0
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4. Ageing of advanced biomaterialsRebeka Rudolf, Karlo Raić, 2024, review article Abstract: The paper presents the ageing processes of advanced biomaterials. The medical profession considers ageing as a syndrome of universal, progressive, irreversible processes that take place at the molecular level (DNA, proteins, lipids) and at the organ level. Ageing is treated quite differently by the engineering profession, which considers it as wear, degradation, corrosion and deformation. In the tissue over time, changes in temperature, changes in pH value and the effect of large forces lead to changes in biomaterials, which are known in the literature as biomaterial ageing processes.
Keywords: biomaterials, ageing, mechanisms
Published in DKUM: 13.01.2026; Views: 0; Downloads: 2
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5. Evaluation of the magnetic properties of Ag-Au-Pd-Cu dental alloysLeo Gusel, Peter Majerič, Mirko Glišić, Aleksandra Kocijan, Rebeka Rudolf, 2024, original scientific article Abstract: The paper discusses four Ag-Au-Pd-Cu dental alloys, with different chemical compositions, which are used to produce fixed dental-prosthetic structures. These dental alloys must have a low level of biological risk after being implanted in the oral cavity, which means minimal release of ions from their surface, or the absence of corrosion, and, recently, the absence of ferromagnetism has been introduced as an additional requirement. The latter requirement is particularly important when magnetic resonance (MR) is used in the medical diagnosis of a patient who has an implanted fixed dental-prosthetic structure. With this technique, the internal structure of the human body is imaged using a strong magnetic field, radio waves and computer technology. Therefore, the absence of ferromagnetic, embedded biomaterials is necessary in the part of the body where medical diagnostics are performed. Microstructural investigations of four Ag-Au-Pd-Cu dental alloys (Auropal S, Auropal SE, Midor S and Midor SE) and measurements of their magnetic properties were carried out as part of the research. The results showed that Ag-Au-Pd-Cu dental alloys have a stable microstructure, which allows them to be processed later into fixed prosthetic constructions. The measurements of the magnetic properties showed that the Ag-Au-Pd-Cu dental alloys are diamagnetic.
Keywords: magnetic properties, noble dental alloys, characterization
Published in DKUM: 12.01.2026; Views: 0; Downloads: 0
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6. Metastable states of complex concentrated Ag–Pd–Pt–Cu–Ni alloy obtained by synthesis of nanoparticles : doctoral dissertationLidija Terzić, 2025, doctoral dissertation Abstract: Doctoral dissertation explores the synthesis and characterization of metastable states within
a novel complex concentrated noble alloy (CCNA) composed of equi-atomic portion of silver
(Ag), palladium (Pd), platinum (Pt), copper (Cu), and nickel (Ni). Completed research activities
enable the understanding of processes and reactions that were crucial in evolution of
thermodynamically metastable microstructures through production of rapidly solidified
ribbons and synthesis of nanoparticles (NP). Two techniques, namely melt spinning and
ultrasonic spray pyrolysis (USP) had been successfully used to achieve homogeneous high
entropy microstructures and were confirmed as suitable for transformation of multiphase
inhomogeneous CCNA microstructures into high entropy ones. Achieved thermodynamically
metastable microstructures enable the achievement of potential functional properties of
selected alloy due to increased surface area and optimized active centres (Ag, Pd, Pt, Cu, Ni)
for catalytic activity.
In the dissertation explained processes and reactions that occurred in the development of the
microstructure of equi-atomic Ag-Pt-Pd-Cu-Ni CCNA during rapid solidification and ultrasonic
spray pyrolysis represent an important contribution to the field of materials science.
Keywords: Complex concentrated alloys, High entropy alloys, Thermodynamically metastable microstructures, Rapid solidification, Ultrasonic spray pyrolysis.
Published in DKUM: 06.01.2026; Views: 0; Downloads: 10
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7. Corrosion behavior of nickel–titanium continuous-casted alloysMinja Miličić Lazić, Dijana Mitić, Katarina Radović, Igor Djordjević, Peter Majerič, Rebeka Rudolf, Branimir Grgur, 2024, original scientific article Abstract: Variations in the corrosion behavior of biomedical NiTi alloys in Cl− containing and acidic
environments present a problem with their biological implantation. The objective of this research
was to evaluate the synergy of the microstructure, the corrosion behavior, and the biocompatibility of
novel continuous-cast NiTi alloys and to compare them with commercial NiTi alloys. The two alloys
have a practically identical nominal chemical composition, but they differ in production technology.
The continuous casting technology involved vacuum induction melting of the basic components
and vertical continuous casting, while the commercial NiTi alloy was produced through a process of
casting, hot rolling, and forming into square shapes. The microstructure was revealed to determine
the surface area and size of grains. The corrosion of a commercial nickel–titanium alloy and one
prepared by a novel continuous casting method in acidic and chloride-containing solutions was
studied via analytical and electrochemical tests. Localized corrosion characteristics related to oxide
properties, when exposed to 9 g L−1 NaCl solution, were examined with focused ion beam analysis
and subsequent microchemical analysis of the formed corrosive products. Corrosion potential over
time and the oxide film resistance were analyzed using linear polarization measurements. To obtain
a preliminary estimate of biocompatibility, human fibroblast cells were used in indirect contact,
i.e., alloy conditioning medium. The continuous casting method resulted in a reduction in the
average grain size in comparison to the commercial sample and better corrosion stability of the
sample in an acidic environment. Also, in a solution of 9 g L−1 NaCl the commercial sample showed
high values for the corrosion current density (jcorr = 6 µA cm−2), which indicated low corrosion
resistance, while the continuous casting sample possessed much better corrosion stability and lower
values for the corrosion current density (jcorr = 0.2 µA cm−2). In line with that, elemental analysis of
the corroded surfaces showed higher Cl− ion deposition over the surface layer of the commercial
sample, suggesting local oxide breakdown. Moreover, NiTicc reached a value three times higher
for polarization resistance (Rp = 270 kΩ cm2) over time in comparison to the commercial sample
(Rp~100 kΩ cm2). Biocompatibility evaluation showed that human fibroblast cells exhibited altered
metabolic activity. An MTT assay showed that cells’ mitochondrial activity dropped below that of
control cells in the presence of both materials’ supernatants.
Keywords: nickel–titanium, corosion behaviour, electrochemical testing, NiTi biocompatibility
Published in DKUM: 30.06.2025; Views: 0; Downloads: 8
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8. Comparison study of four commercial SARS-CoV-2-rapid antigen tests : characterisation of the individual componentsŽiga Jelen, Ivan Anžel, Rebeka Rudolf, 2022, original scientific article Abstract: During the corona virus (COVID-19) pandemic, there was a sharp increase in the need for diagnostic tests that could detect the presence of SARS-CoV-2 virus or its antibodies quickly and reliably. An important type in the group of diagnostic tests are rapid antigen lateral flow immuno-assay (LFIA) tests, which operate on the immuno-chromatographic principle with the lateral flow of analyte. Clinical practice in the last year has shown that such diagnostic tests can be effective in preventing the spread of the SARS-CoV-2 virus.The development, and, thus, the production of the rapid antigen LFIA tests, is influenced by a number of factors that determine their sensitivity and accuracy indirectly. These factors are directly dependent on the type of antibody produced, which is formed as an immune response when infected with the virus. The production of the rapid antigen LFIA tests is associated with the appropriate selection of basic components that determine the type and quality of these tests. The basic components include: substrates and membranes, antigens, antibody labels and compatible buffers. The correct choice of membranes and their materials is crucial to compiling an effective rapid antigen LFIA test. This study therefore presents a comparative analysis of four commercially available SARS-CoV-2-rapid LFIA tests using state-of-the-art characterisation techniques scanning electron microscopy (SEM), inductively coupled plasma-optical emission spectrometry (ICP-OES), environmental scanning electron microscope / energy-dispersive X-ray spectroscopy (ESEM/EDX), Fourier-transform infrared spectroscopy / attenuated total reflection (FTIR/ATR) for the individual components. The obtained results were the starting point for the development and assembling of our own rapid antigen LFIA test based on gold nanoparticles as antibody labels.
Keywords: hitri antigenski testi, komponente, karakterizacija, analize, rapid antigen test, components, characterisation, analysis
Published in DKUM: 26.03.2025; Views: 0; Downloads: 7
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9. Unraveling the antibiofilm activity of a new nanogold resin for dentures and epithesisVera Ivanović, Danica Popović Antić, Sanja Petrović, Rebeka Rudolf, Peter Majerič, Miloš Lazarević, Igor Djordjević, Vojkan Lazić, Milena Radunović, 2022, original scientific article Abstract: Dentures and epitheses are mostly made from poly(methyl methacrylate) (PMMA), which
does not show antimicrobial properties. They present reservoirs of microorganisms grown in
biofilms. The aim of this study is to prepare a PMMA enriched with gold nanoparticles (AuNPs)-
PMMA/AuNPs and the examination of its physical, mechanical and antimicrobial properties. The
AuNPS were synthetized from HAuCl4 using the ultrasonic spray pyrolysis method with lyophilization. The PMMA/AuNP samples were compared to PMMA samples. Density was measured by
pycnometer. Microhardness was evaluated using the Vickers hardness test. Monomicrobial biofilm
formation (Streptococcus mitis, Candida albicans, Staphylococcus aureus and Escherichia coli) was measured by colony-forming units (CFUs) and MTT test and visualized by SEM. AuNP release was
measured indirectly (the CFUs of the medium around the sample). The density and microhardness
of the PMMA/AuNPs were similar to those of the PMMA. CFU and MTT values for the biofilms
formed on the PMMA for each of the tested species were higher than those of the biofilms formed on
the PMMA/AuNPs. The CFUs of the medium around the sample were similar for both materials.
PMMA/AuNPs showed a significant reduction in the monomicrobial biofilms of all tested species.
AuNPs are not released from PMMA/AuNPs. Density, indirect measurement of residual monomer
and dentures weight were similar between PMMA and PMMA/AuNPs. Microhardness, as a measure
of the wear resistance, was also similar between tested discs.
Keywords: PMMA, gold nanoparticles (AuNPs), biofilm, antibiofilm effect
Published in DKUM: 24.03.2025; Views: 0; Downloads: 8
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10. A nonlinear probabilistic pitting corrosion model of Ni–Ti alloy immersed in shallow seawaterŠpiro Ivošević, Gyöngyi Vastag, Nataša Kovač, Peter Majerič, Rebeka Rudolf, 2022, original scientific article Abstract: The degradation of metal materials in a marine environment represents the consequence
of the electrochemical corrosion of metals under the influence of the environment. The application
of new materials in the maritime industry requires experimental, real-world research on the form
of corrosive damage and the intensity of the corrosion. This paper analyses the pitting corrosion of
a rod-shaped nickel–titanium (Ni–Ti) alloy that was produced by means of the continuous casting
method. In total, three samples were posted in a real seawater environment and analysed after 6,
12, and 18 months. Pits were detected on the Ni–Ti alloy after 18 months of exposure to the marine
environment. The database on pitting corrosion was created by measuring depth in mm, which was
performed by means of a nonlinear method, and by the generation of an artificial database of a total
of 120, gauged in critical pit areas. The data were obtained by the application of a nonlinear model,
and under the assumption that corrosion starts after 12 months of exposure in the corrosive marine
environment. The EDX analysis of the Ni–Ti alloy composition inside the pits and on the edges of the
pits indicated that the corrosion process in the hole of the pit occurs due to the degradation of the Ni.
Keywords: Ni–Ti alloy, pitting corrosion, seawater, EDX analysis, nonlinear, probabilistic
Published in DKUM: 24.03.2025; Views: 0; Downloads: 11
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