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Povzetek: Stainless steel forms a native film of mixed metal oxides, and organic impurities are likely to adsorb on the surface upon exposure to ambient conditions. For many applications, oxides and impurities should be removed, and several techniques have been used for decades. An innovative method is presented in this paper. The organic impurities were oxidized using a water solution of 1 M peroxynitric acid (PNA). Stainless steel samples were immersed in the solution, and the oxidation of organic impurities was evaluated by the ultra-thin depth profiling using secondary ion mass spectrometry (SIMS). A minute of treatment with PNA caused oxidation of organic impurities and a decrease in the SIMS CN– signal over an order of magnitude. Prolonged treatment caused the selective removal of the native iron oxide film, leaving a protective film of chromium oxide. Removal of the iron oxide film was also observed when stainless steel was treated with 1 M HNO3. The PNA method is useful for routine cleaning of stainless steel to remove the organic contaminants from the surface and keep the passive chromium oxide film intact. It is ecologically friendly and enables rapid decomposition of the traces of organic impurities likely to be adsorbed on the metallic surfaces.
Ključne besede: peroxynitric acid, surface modifications, secondary ion mass spectrometry
Objavljeno v DiRROS: 11.11.2025; Ogledov: 130; Prenosov: 63
Celotno besedilo (1,14 MB)
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Ključne besede: electrochemical sensors, electrodes, polymers, graphite thick films, surface morphology
Objavljeno v DiRROS: 27.10.2025; Ogledov: 197; Prenosov: 99
Celotno besedilo (4,59 MB)
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Povzetek: Cathodic arc evaporation (CAE) is the most commonly used physical vapor deposition (PVD) method to deposit protective coatings on cutting and forming tools. However, this deposition method results in a relatively rough surface due to micro-droplet emission. The first contact between the coating and the workpiece surface is at the sites of these growth defects, influencing the state of the contact, such as particle formation and oxidation spots. Growth defects significantly impact the coating's wear and friction properties. Their impact is not limited to the beginning of the contact formation but also expands in the long run, and they can deteriorate the coatings much sooner than expected. This research aims to monitor the wear and friction properties of the cathodic arc deposited AlTiN hard coating during the running-in and steady-state periods under different temperature conditions. Tribological tests against the Al2O3 counterbody were carried out at different temperatures, from room temperature up to 700 °C. The sliding distance at specific temperatures, ranging from 50 to 140,000 cycles, enabled us to monitor the wear progression from first contact formation at the growth defects to the complete coating wear from the WC-Co substrate. After tribological tests, the samples were analyzed using detailed 3D profilometry, SEM, and FIB analysis to determine the wear mechanisms in different stages of high-temperature wear. Attention was focused on the growth defects, their impact on the running-in behavior, and the oxygen diffusion pathways along growth defects that ultimately lead to the delamination of the coating from the substrate.
Ključne besede: cathodic arc evaporation, physical vapor deposition, growth defects
Objavljeno v DiRROS: 19.09.2025; Ogledov: 322; Prenosov: 137
Celotno besedilo (17,23 MB)
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Povzetek: Nowadays, it is a great challenge to develop new medicines for treating various infectious diseases. The treatment of these diseases is of utmost interest to further prevent the development of multi-drug resistance in different pathogens. Carbon quantum dots, as a new member of the carbon nanomaterials family, can potentially be used as a highly promising visible-light-triggered antibacterial agent. In this work, the results of antibacterial and cytotoxic activities of gamma-ray-irradiated carbon quantum dots are presented. Carbon quantum dots (CQDs) were synthesized from citric acid by a pyrolysis procedure and irradiated by gamma rays at different doses (25, 50, 100 and 200 kGy). Structure, chemical composition and optical properties were investigated by atomic force microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, UV-Vis spectrometry and photoluminescence. Structural analysis showed that CQDs have a spherical-like shape and dose-dependent average diameters and heights. Antibacterial tests showed that all irradiated dots had antibacterial activity but CQDs irradiated with dose of 100 kGy had antibacterial activity against all seven pathogen-reference bacterial strains. Gamma-ray-modified CQDs did not show any cytotoxicity toward human fetal-originated MRC-5 cells. Moreover, fluorescence microscopy showed excellent cellular uptake of CQDs irradiated with doses of 25 and 200 kGy into MRC-5 cell
Objavljeno v DiRROS: 11.07.2025; Ogledov: 376; Prenosov: 145
Celotno besedilo (4,29 MB)

Povzetek: Nowadays, bacteria resistance to many antibiotics is a huge problem, especially in clinics and other parts of the healthcare system. This critical health issue requires a dynamic approach to produce new types of antibacterial coatings to combat various pathogen microbes. In this research, we prepared a new type of carbon quantum dots based on phloroglucinol using the bottom-up method. Polyurethane composite films were produced using the swell–encapsulation–shrink method. Detailed electrostatic force and viscoelastic microscopy of carbon quantum dots revealed inhomogeneous structure characterized by electron-rich/soft and electron-poor/hard regions. The uncommon photoluminescence spectrum of carbon quantum dots core had a multipeak structure. Several tests confirmed that carbon quantum dots and composite films produced singlet oxygen. Antibacterial and antibiofouling efficiency of composite films was tested on eight bacteria strains and three bacteria biofilms.
Objavljeno v DiRROS: 11.07.2025; Ogledov: 395; Prenosov: 120
Celotno besedilo (3,89 MB)