1. Defluorination of polytetrafluoroethylene surface by hydrogen plasmaAlenka Vesel, Dane Lojen, Rok Zaplotnik, Gregor Primc, Miran Mozetič, Jernej Ekar, Janez Kovač, Marija Gorjanc, Manja Kurečič, Karin Stana-Kleinschek, 2022, independent scientific component part or a chapter in a monograph Keywords: polytetrafluoroethylene, fluorine depletion, hydrogen plasma, VUV radiation, surface modification, hydrophilic
Published in DiRROS: 10.11.2025; Views: 281; Downloads: 126
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2. Influence of surface preparation and surface topography on tensile shear strength of polyurethane adhesively bonded beech wood single-lap joints : a finite element method approachLuka Naumovski, Martin Capuder, Jakub Michal Sandak, Boris Azinović, 2025, original scientific article Abstract: In this study, the mechanical properties of bonded single-lap joints are analysed by tensile lap shear tests on beech wood. A one-component polyurethane adhesive was used, and three different methods of surface preparation were applied: planing, sanding along the grain, and sanding perpendicular to the grain. Prior to bonding, the wooden lamellae underwent laser scanning to obtain surface profiles, which were then analysed for surface roughness. Scanned surface topographies with their features were integrated into the finite element analysis (FEA) software COMSOL Multiphysics to simulate the lap shear bonding area for different surface profiles and roughness. The FEA model implements linear material models, which represent the adherend and thin adhesive layer, combined with a modified local cohesive zone model for the adhesive bond interfacial forces. The experimental tests were conducted in a dry environment, where a higher surface roughness achieved by sanding correlated with a higher tensile shear strength. This increased surface roughness was attributed to the enhanced mechanical interlocking mechanism. This finding aligns with the FE analysis, which showed that increased surface roughness, micropillars and indentations, led to variations in stress concentration and distribution compared to a smooth surface bond.
Keywords: beech wood, mechanical interlocking, surface modification, polyurethane, finite element modeling
Published in DiRROS: 11.08.2025; Views: 464; Downloads: 212
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3. Dataset used for the paper »Surface modification of magnesium for biomedical applications: comparative analysis of plasma treatment, laser texturing and sandblasting«Marjetka Conradi, complete scientific database of research data Abstract: Magnesium and its alloys have emerged as promising materials for biomedical applications due to their light weight, mechanical compatibility with bone, biodegradability, and excellent biocompatibility. However, their rapid degradation in physiological environments remains a critical challenge. To address this, a range of surface-modification techniques have been explored to tailor the surface properties while preserving the bulk characteristics of magnesium. This paper provides an overview of surface-engineering methods aimed at enhancing the corrosion resistance, mechanical performance and bioactivity of magnesium. Three key surface-modification approaches are presented: plasma treatment, laser texturing and sandblasting. Plasma treatment resulted in the formation of a stable, protective oxide layer with significantly improved corrosion resistance and hydrophilicity. Laser texturing generated hierarchical microstructures yielding superhydrophobic surfaces with an enhanced hardness, though slightly reduced corrosion resistance. Sandblasting led to an increased surface roughness and mechanical stiffness, but also introduced microstructural defects that are detrimental to the corrosion stability. Overall, the study demonstrates how tailored surface modifications can effectively balance the mechanical integrity and degradation behavior of magnesium, paving the way for its optimized use in biomedical applications.
Keywords: magnesium, surface modification, biomaterial
Published in DiRROS: 18.06.2025; Views: 692; Downloads: 309
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5. Functionalization of FeCoNiCu medium entropy alloy via nitridation and anodic oxidation for enhanced oxygen evolution and glycerol oxidationLuka Suhadolnik, Milutin Smiljanić, Marjan Bele, Mejrema Nuhanović, Matjaž Finšgar, Nik Maselj, Daniela Neumüller, Lidija D. Rafailović, Nejc Hodnik, 2025, original scientific article Abstract: Medium entropy alloys (MEAs) have emerged as a promising class of materials for electro-catalysis due to their tunableproperties and exceptional catalytic performance. This study successfully functionalized a bulk FeCoNiCu alloy using a combined anodic oxidation (AO) and nitridation (NT) approach to produce a highly porous, thin-film catalyst. The hierarchical structure formed during the surface treatments enhances the material's specific surface area and alters the oxidation states of the constituent metals, creating abundant active sites. The electrocatalytic performance of themodified bulk FeCoNiCu electrode was evalu-ated for both the oxygen evolution reaction (OER) and glycerol oxidation reaction (GOR) in an alkaline electrolyte. Remarkably, the AO-NT-treated catalyst exhibited superior activity for OER, surpassing commercial IrOx benchmarks with lower overpotential requirements. For GOR, the FeCoNiCu electrode demonstrated excellent performance by significantly reducing energy input compared to OER, highlighting its potential as a dual-purpose catalyst for alkaline water splitting. Post-reaction product analysis via NMR confirmed the formation of value-added chemicals, with formic acid identified as the main product. These results underline the feasibility of surface-modified MEAs for sustainable energy and chemical production applications, offering a cost-effective alternative to noble metal-based catalysts.
Keywords: medium entropy alloy, surface modification, electrocatalysis, oxygen evolution reaction, glycerol oxidation
Published in DiRROS: 10.04.2025; Views: 760; Downloads: 389
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6. Combining ultrafast laser texturing and laser hardening to enhance surface durability by improving hardness and wear performanceAbhijit Cholkar, Suman Chatterjee, Sujith Kumar, Marko Sedlaček, Bojan Podgornik, David Kinahan, Dermot Brabazon, 2024, original scientific article Abstract: Aluminum alloy 7075 is utilized widely across marine, aerospace, and automotive sectors. However, its surface wear resistance has hindered its application in certain tribological environments. Addressing this challenge, the current study examines a hybrid laser method to increase surface wear resistance by combining two techniques: ultrafast laser texturing and laser-based surface hardening. Ultrafast laser processing is conducted using 3 W laser power, 100 kHz pulse repetition rate, 4 mm s-1 scanning speed, and three different scan patterns. After the texturing operation, laser-based surface hardening is then performed on these textures using a continuous wave laser. The laser heat treatment is conducted using laser powers of 400 and 500 W with three different scan speeds of 1, 2, and 3 mm s-1 . Microhardness evaluations show a notable increase in hardness, with the hardest sample exhibiting a 17.8% increase compared to the pristine sample. The lasertextured and laser heat-treated samples exhibit a significant reduction in the average coefficient of friction and wear volumes compared to samples that were laser-textured but not laser heat-treated. The investigated laser processing strategy offers a promising approach for surface modification, enhancing both mechanical properties and wear resistance of aluminum alloy 7075 surfaces.
Keywords: hardness, laser hardening, parametric modeling, surface modification, ultrafast laser texturing, wear resistance
Published in DiRROS: 05.11.2024; Views: 1011; Downloads: 1143
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7. Influence of oil viscosity on the tribological behavior of a laser-textured Ti6Al4V alloyMarjetka Conradi, Aleksandra Kocijan, Bojan Podgornik, 2023, original scientific article Abstract: Laser texturing with a dimple pattern was applied to modify a Ti6Al4V alloy at the micro level, aiming to improve its friction and wear resistance in combination with oil lubrication to optimize the performance in demanding industrial environments. The tribological analysis was performed on four different dimple-textured surfaces with varying dimple size and dimple-to-dimple distance and under lubrication with three different oils, i.e., T9, VG46, and VG100, to reflect the oil viscosity’s influence on the friction/wear of the laser-textured Ti6Al4V alloy. The results show that the surfaces with the highest texture density showed the most significant COF reduction of around 10% in a low-viscosity oil (T9). However, in high-viscosity oils (VG46 and VG100), the influence of the laser texturing on the COF was less pronounced. A wear analysis revealed that the laser texturing intensified the abrasive wear, especially on surfaces with a higher texture density. For low-texturing-density surfaces, less wear was observed for low- and medium-viscosity oils (T9 and VG46). For medium-to-high-texturing densities, the high-viscosity oil (VG100) provided the best contact conditions and wear results. Overall, reduced wear, even below the non-texturing case, was observed for sample 50–200 in VG100 lubrication, indicating the combined effect of oil reservoirs and increased oil-film thickness within the dimples due to the high viscosity.
Keywords: oil lubrication, surface modification, Ti-based alloy, tribology
Published in DiRROS: 01.02.2024; Views: 1729; Downloads: 795
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8. Deposition of chitosan on plasma-treated polymers : a reviewAlenka Vesel, 2023, review article Abstract: Materials for biomedical applications often need to be coated to enhance their performance, such as their biocompatibility, antibacterial, antioxidant, and anti-inflammatory properties, or to assist the regeneration process and influence cell adhesion. Among naturally available substances, chitosan meets the above criteria. Most synthetic polymer materials do not enable the immobilization of the chitosan film. Therefore, their surface should be altered to ensure the interaction between the surface functional groups and the amino or hydroxyl groups in the chitosan chain. Plasma treatment can provide an effective solution to this problem. This work aims to review plasma methods for surface modification of polymers for improved chitosan immobilization. The obtained surface finish is explained in view of the different mechanisms involved in treating polymers with reactive plasma species. The reviewed literature showed that researchers usually use two different approaches: direct immobilization of chitosan on the plasma-treated surface or indirect immobilization by additional chemistry and coupling agents, which are also reviewed. Although plasma treatment leads to remarkably improved surface wettability, this was not the case for chitosan-coated samples, where a wide range of wettability was reported ranging from almost superhydrophilic to hydrophobic, which may have a negative effect on the formation of chitosan-based hydrogels.
Keywords: polymer surfaces, chitosan, coatings, plasma-surface modification, adhesion
Published in DiRROS: 24.02.2023; Views: 1711; Downloads: 908
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9. A method for the immobilization of chitosan onto urinary cathetersAlenka Vesel, Nina Recek, Rok Zaplotnik, Albert Kurinčič, Katja Kuzmič, Lidija Fras Zemljič, 2022, original scientific article Abstract: A method for the immobilization of an antibacterial chitosan coating to polymeric urinary medical catheters is presented. The method comprises a two-step plasma-treatment procedure, followed by the deposition of chitosan from the water solution. In the first plasma step, the urinary catheter is treated with vacuum-ultraviolet radiation to break bonds in the polymer surface film and create dangling bonds, which are occupied by hydrogen atoms. In the second plasma step, polymeric catheters are treated with atomic oxygen to form oxygen-containing surface functional groups acting as binding sites for chitosan. The presence of oxygen functional groups also causes a transformation of the hydrophobic polymer surface to hydrophilic, thus enabling uniform wetting and improved adsorption of the chitosan coating. The wettability was measured by the sessile-drop method, while the surface composition and structure were measured by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. Non-treated samples did not exhibit successful chitosan immobilization. The effect of plasma treatment on immobilization was explained by noncovalent interactions such as electrostatic interactions and hydrogen bonds.
Keywords: polymer, chitosan immobilization, adhesion, plasma-surface modification, biopolymers
Published in DiRROS: 05.12.2022; Views: 1638; Downloads: 889
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