1921. A Raman microspectroscopy-based comparison of pigments applied in two gothic wall paintings in SloveniaMaja Gutman, Ajda Mladenovič, Anabelle Križnar, Sabina Dolenec, 2019, original scientific article Abstract: The present study deals with the characterisation of pigments used in two overlaid gothic wall paintings from the former 13th century Minorite church of St. Francis of Assisi (Koper, Slovenia), in order to define differences in the technologies used. Paint layer samples were analysed via Raman microspectroscopy, supported by SEM/EDS and FTIR analysis, when necessary. The results revealed that the 14th century mural was painted mainly a fresco with final elements a secco, a technique typical of Italian mediaeval wall painting. In contrast, the 15th century painting was executed mostly a secco, a technique often applied in Northern Europe and the Alpine region. The differences between the two paintings are especially obvious in the pigments applied. While the earlier painting is characterised by azurite, carbon black, red and yellow ochres, lime white and green earth, the palette used for the younger painting is much broader. In addition to red and yellow ochres, carbon black and lime white, lead pigments such as lead white, red lead and lead-tin yellow type I were also determined, as well as a number of expensive pigments including cinnabar, azurite and malachite. Also found in the younger painting was the rare orange yellow pigment vanadinite. In both layers, azurite was applied a secco for the background area. Gilding was confirmed in both layers, carried out as application of gold leaves on red bole (in the earlier mural) and on mordant (on a younger, superimposed (overlaid painting), which is quite exclusive and rare for Slovene mediaeval painting. In the younger layer also a use of tin foil for secondary elements was discovered.
Keywords: wall paintings, pigments, Gothic, golding, Raman microspectroscopy
Published in DiRROS: 27.10.2023; Views: 493; Downloads: 215
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1922. The corrosion resistance of dental Ti6Al4V with differing microstructures in oral environmentsMirjam Bajt Leban, Tadeja Kosec, Matjaž Finšgar, 2023, original scientific article Abstract: The impact of the microstructural properties of a Ti6Al4V alloy on its electrochemical properties, as well as the effect of the α- and β-phases present within it, is still unclear. With the introduction of new, emerging technologies, such as selective laser melting and post heat treatments, the effect of the microstructure on an alloy's corrosion properties has become increasingly interesting from a scientific perspective. When these alloys are produced through different methods, despite an identical chemical composition they have diverse microstructures, and consequently display varying resistance to corrosion. In the present research study, Ti–6Al–4V alloy specimens produced by three different processes, leading to the formation of three different microstructures were investigated: heat treated specimen fabricated by selective laser melting, wrought and cast specimens. The impact of the microstructure of these alloys when immersed in artificial saliva was studied through the use of various electrochemical techniques, by microscopical examinations, and time-of-flight secondary ion mass spectrometry. Corrosion properties were investigated by the measurement of open circuit potential, linear polarization, and potentiodynamic curve measurements followed by microscopical examinations, and time-of-flight secondary ion mass spectrometry examination was conducted to reveal spatial distribution of alloying species on oxide film. It was found that the difference between specimens containing an α+β microstructure was small and not dependent on the aspect ratio of the β-phase, alloy grain size, and vanadium partitioning coefficient, but rather on the size, shape, and content of this phase.
Keywords: Ti6Al4V, dental alloy, microstructure, corrosion resistance, heat treatment, ToF-SIMS
Published in DiRROS: 26.10.2023; Views: 588; Downloads: 313
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1925. Influence of laser colour marking on the corrosion properties of low alloyed TiTadeja Kosec, Andraž Legat, Janez Kovač, Damjan Klobčar, 2019, original scientific article Abstract: In the field of surface treatment, laser colour marking can be used to produce coloured marks on the surfaces of metals. Laser colour markings can be applied to various materials, but on titanium alloys a wide spectra of vivid colours can be achieved. This study presents an analysis of the corrosion properties of laser treated surfaces that were exposed to aggressive environments. Different samples were prepared with laser light of various power intensities and processing speeds. The samples were prepared on low alloyed Ti. Electrochemical, spectroscopic and microstructural analyses were conducted in order to study the properties of the laser treated surfaces. Corrosion testing showed different effects of laser power and production speed on the properties of the laser treated surfaces. It was shown that a high intensity and slow processing rate affect the surfaces by forming oxides that are relatively stable in a corrosive environment of 0.1 M NaCl. Spectroscopic investigations including scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses showed the differences in chemical structure of the surface layer formed after laser treatment. Similarly, microstructural investigations showed different effects on the surface and sub-surface layer of the laser treated samples.
Keywords: Ti alloy, laser treatment, XPS, corrosion
Published in DiRROS: 25.10.2023; Views: 486; Downloads: 191
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1926. Development of multi-component fluoropolymer based coating on simulated outdoor patina on quaternary bronzeTadeja Kosec, Luka Škrlep, Erika Švara Fabjan, Andrijana Sever Škapin, Giulia Masi, Elena Bernardi, Cristina Chiavari, Claudie Josse, Jerome Esvan, Luc Robbiola, 2019, original scientific article Abstract: Bronze reacts with oxygen, humidity, and pollutants in the atmosphere so that a patina forms. Natural exposure to an outdoor atmosphere can be simulated and accelerated in order to achieve a patina that mimics outdoor ancient patina. In order to avoid the uncontrolled dissolving of either the natural or artificially formed patina, protection of the patina is needed.
In this study, a multi-component fluoropolymer based coating for the protection of bronze patina was developed. In order to provide various functionalities of the coating (such as the hydrophobicity of the coating surface, obtaining interactions within the coating itself as well as a bronze substrate and inhibiting the corrosion processes), a fluoroacrylate coating with appropriate adhesion promoter was suggested, with and without a silane modified benzotriazole inhibitor. The protective efficiency and durability of the applied coatings were investigated electrochemically using potentiodynamic tests and electrochemical impedance spectroscopy in a simulated acid rain solution. All of the developed coatings showed a significant decrease in the corrosion current density. The self-assembled single layer coating (FA-MS) also showed 100% inhibition efficiency. After ageing the coating remained transparent and did not change by UV exposure and/or thermal cycling. The patina and coating investigations using FIB-SEM and EDX showed that the latter coating (FA-MS) successfully covered the surface of the patinated bronze. The mechanism of the bonding was proposed and supported with the spectroscopic observation of a thin and even coating.
Keywords: bronze, patina, fluoropolymer coating, atmospheric corrosion
Published in DiRROS: 25.10.2023; Views: 453; Downloads: 250
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1928. Development of an electrical resistance sensor from high strength steel for automotive applicationsTadeja Kosec, Viljem Kuhar, Andrej Kranjc, Vili Malnarič, Branko Belingar, Andraž Legat, 2019, original scientific article Abstract: This work focuses on a demonstration of the monitoring of corrosion processes taking place in high strength steel in automotive applications. This is performed by means of a corrosion sensor, which operates as an electrical resistance sensor. It was developed from the same type of material that is used for the high-strength steel parts produced in the automotive industry. Using the sensor, real time corrosion processes can be measured. It is attached to a location inside the vehicle’s engine and is equipped with a data logger, which enables wireless transfer of the measured data. In this study the development, operation, and evaluation of the monitoring process are presented. Corrosion estimation is verified by means of electrochemical methods. A metallographic investigation was included in order to verify the similarity between the microstructural properties of the sensor and those of the as-received high-strength steel sheet.
Keywords: high strenghth steel, automotive, electrical resistance sensor, corrosion
Published in DiRROS: 24.10.2023; Views: 616; Downloads: 203
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1929. Production of lightweight alkali activated mortars using mineral woolsAhmad Alzaza, Mohammad Mastali, Paivo Kinnunen, Lidija Korat, Zahra Abdollahnejad, Vilma Ducman, Mirja Illikainen, 2019, original scientific article Abstract: This experimental study aimed to develop a fiber-reinforced lightweight mineral wool-based alkali activated mortar. The lightweight mineral wool-based alkali activated mortars were produced using premade foam and reinforced by polypropylene (PP) fibers. They were assessed in terms of fresh and hardened-state properties. Fresh-state properties were investigated by mini-slump tests. Hardened-state characteristics were assessed by ultrasonic pulse velocity, dry density, compressive and flexural strengths, drying shrinkage, efflorescence, water absorption, and permeable porosity. For the first time, the resistance of the synthesized lightweight mineral wool-based alkali activated mortars against harsh conditions (carbonation, freeze and thaw, and high temperature) were evaluated. The porous structures of the developed lightweight alkali activated mortars were also analyzed using an X-ray micro-computed tomography (CT) technique. Lightweight mix compositions with densities in a range of 770%1510 kg/m3, compressive strengths of 1%9 MPa, and flexural strengths of 2.6%8 MPa were developed. Increases in both density and strength after carbonation were also recorded, while a decrease of strength was noticed after exposure to freeze/thaw and high temperatures of up to 500 %C.
Keywords: alkali activation, mineral wool, mortars
Published in DiRROS: 24.10.2023; Views: 416; Downloads: 168
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1930. Legislative and judicial responses to the “refugee crisis” in Slovenia and Austria : a comparative perspectiveNeža Kogovšek Šalamon, 2023, original scientific article Abstract: The article compares key normative and judicial responses to the 2015–2016 “refugee crisis” in Slovenia and Austria. It does so by comparing the asylum statistics, the main changes to the legislation reflecting populist reactions to the “refugee crisis,” and judicial responses to these changes and reactions. The qualitative legal analysis is based on examples of the most important changes and responses. The article considers the populistic context of these changes, as discussed by some political scientists, who demonstrate that with the crisis, a new wave of populism—“the populist Othering of migrants”—emerged.
Keywords: refugee crisis, constitutional court, Slovenia, Austria, populism
Published in DiRROS: 24.10.2023; Views: 462; Downloads: 169
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