11. Development of the recycling procedure for rapid antigen testsRebeka Rudolf, Darja Feizpour, Žiga Jelen, Peter Majerič, Tilen Švarc, Matej Zadravec, Timi Gomboc, Aleksandra Kocijan, 2024, original scientific article Keywords: rapid antigen tests, recycling, characterization, nanogold, plastic
Published in DiRROS: 28.02.2024; Views: 158; Downloads: 66
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13. Tribological evaluation of vegetable ▫$oil/MoS_2$▫ nanotube-based lubrication of laser-textured stainless steelMarjetka Conradi, Bojan Podgornik, Maja Remškar, Damjan Klobčar, Aleksandra Kocijan, 2023, original scientific article Abstract: In the present work, the functionalisation of austenitic stainless steel, AISI 316L surfaces via nanosecond Nd:YAG laser texturing in order to modify the surface morphology with crosshatch and dimple patterns is presented. A tribological analysis under lubrication with sunflower and jojoba oil with and without the addition of a solid lubricant, MoS2 nanotubes, was performed. In conjunction with friction/wear response laser-textured surface wettability, oil spreadability and oil retention capacity were also analysed. It was shown that the crosshatch pattern generally exhibited lower friction than the dimple pattern, with the addition of MoS2 nanotubes not having any significant effect on the coefficient of friction under the investigated contact conditions. This was found in addition to the better oil spreadability and oil retention capacity results of the crosshatch-textured surface. Furthermore, texturing reduced the wear of the stainless-steel surfaces but led to an approximately one order of magnitude larger wear rate of the steel counter-body, primarily due to the presence of hard bulges around the textured patterns. Overall, the crosshatch pattern showed better oil retention capacity and lower friction in combination with different vegetable oils, thus making it a promising choice for improving tribological performance in various environmentally friendly applications.
Keywords: tribology, stainless steel, vegetable oil lubrication, MoS2 nanotubes
Published in DiRROS: 02.02.2024; Views: 131; Downloads: 75
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14. 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: 184; Downloads: 74
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15. Ultra-high strenght TWIP steel with high chromium contentPavel Podaný, Tomáš Studecký, Tomas Gregor, Radek Prochazka, Aleksandra Kocijan, 2023, original scientific article Abstract: A new ultra-high strength steel with a fully austenitic microstructure and twinning-induced plasticity (TWIP) effect has been developed. TWIP effect gives this steel a good combination of high strength of over 1000 MPa and ductility of over 35%. This new steel has a high chromium content, which increases its corrosion resistance. By combining cold rolling and annealing, the steel has achieved a very fine austenitic microstructure with an average grain diameter of 2.85 µm. This steel could be used for structural applications or components that need to withstand high levels of stress, deformation and corrosion environment.
Keywords: TWIP steels, corrosion resistance, microstructure, tensile strength, plasticity
Published in DiRROS: 31.01.2024; Views: 202; Downloads: 81
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16. Improving the surface properties of additive-manufactured Inconel 625 by plasma nitridingDanijela Anica Skobir Balantič, Črtomir Donik, Bojan Podgornik, Aleksandra Kocijan, Matjaž Godec, 2023, original scientific article Abstract: As a surface-hardening technique, plasma nitriding is a common procedure for improving the properties of
conventional Ni-based alloys. The diffusion of nitrogen hardens a layer on the surface of the alloy, leading to
better wear resistance and a higher coefficient of friction, as well as a higher surface hardness. This study reports
the effect of plasma nitriding on additive-manufactured (AM) Inconel 625 (IN625) compared to its conventional
manufactured and nitrided counterparts. The samples produced with the laser powder-bed fusion (LPBF) process
were subsequently plasma nitrided in the as-built condition, stress-relief annealed at 870 °C and solution treated
at 1050 °C. The plasma nitridings were carried out at 430 °C and 500 °C for 15 h. The growth kinetics of the
nitride layer of the AM samples depends on the prior heat treatments and is faster in the as-built state due to the
specific cellular structure. The lower nitriding temperature leads to the formation of expanded austenite in the
nitride layer, while at the higher nitriding temperature, the expanded austenite decomposes and CrN precipitation
occurs. The XRD and SEM analyses confirmed the presence of two layers: the surface layer and the
diffusion layer beneath. The lower nitriding temperature caused the formation of expanded austenite or a
combination of expanded austenite and CrN. The higher nitriding temperature led to the decomposition of the
expanded austenite and to the formation/precipitation of CrN. The higher nitriding temperature also decreased
the corrosion resistance slightly due to the increased number of precipitated Cr-nitrides. On the other hand, the
wear resistance was significantly improved after plasma nitriding and was much less influenced by the nitriding
temperature.
Keywords: additive manufacturing, powder-bed fusion, plasma nitriding, expanded austenite, wear and corrosion resistance, Ni-based alloy
Published in DiRROS: 31.01.2024; Views: 187; Downloads: 79
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17. Effect of laser texturing pattern on Ti6Al4Vtribocorrosion in a physiological solutionMarjetka Conradi, Tadeja Kosec, Bojan Podgornik, Aleksandra Kocijan, Janez Kovač, Damjan Klobčar, 2022, original scientific article Abstract: Laser texturing is a process that alters a material’s surface properties by modifying its morphology, which can improve properties like adherence, wettability, thermal and electrical conductivity and friction. Here, the effect of laser texturing was studied on an alpha-beta titanium alloy (Ti6Al4V) biomedical material. Two types of patterned surfaces, cross-hatch with varying scan-line separations, Dx = 100, 180 and 280 μm and dimples of 200 μm size, were prepared on the surface of alpha-beta titanium alloy by laser technology. Prepared samples were characterised for their surface properties, such as corrosion, wear-induced corrosion, friction and wettability. Electrochemical and tribocorrosion properties in a physiological solution were studied on the samples with different texture densities of cross-hatch pattern and dimples and compared to the as-received alpha-beta titanium alloy surface. Corrosion rate decreased for laser-textured samples, especially for cross-hatch texture (down to 1 μm/year for Dx = 180 μm) when compared to the as-received alpha-beta titanium alloy surface due to the changed laser-induced surface film and wetting properties. Friction coefficient slightly decreased for all laser-textured surfaces, most noticeably for cross-hatch patterns, from 0.38 (as-received) down to 0.34 (Dx = 180 and 280 μm). The main contribution to total wear in physiological solution increased due to the mechanical wear, which is governed by the removal of the surface oxide layer induced by laser texturing.
Keywords: TiAIV, laser texturing, tribocorrosion, open access
Published in DiRROS: 17.05.2023; Views: 294; Downloads: 119
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18. Current trends on mechanical, corrosion resistance, and antibacterial properties of metallic materials : editorialMarjetka Conradi, Aleksandra Kocijan, 2022, preface, editorial, afterword Keywords: steel, corrosion resistance, mechanical properties, antibacterial properties
Published in DiRROS: 22.06.2022; Views: 498; Downloads: 136
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19. Water versus oil lubrication of laser-textured Ti6Al4V alloy upon addition of MoS2 nanotubes for green tribologyMarjetka Conradi, Bojan Podgornik, Aleksandra Kocijan, Maja Remškar, Damjan Klobčar, 2022, original scientific article Keywords: green tribology, surface texturing, MoS2 nanotubes, lubrication, Ti6Al4V alloy
Published in DiRROS: 06.05.2022; Views: 485; Downloads: 160
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20. The influence of the plasma-nitriding temperature on the microstructure evolution and surface properties of additive-manufactured 18Ni300 maraging steelMatjaž Godec, Francisco Ruiz-Zepeda, Bojan Podgornik, Črtomir Donik, Aleksandra Kocijan, Danijela Anica Skobir Balantič, 2022, original scientific article Keywords: maraging steel, powder bed fusion, plasma nitriding, microstructure, wear resistance, corrosion resistance
Published in DiRROS: 06.05.2022; Views: 591; Downloads: 206
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