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Query: "author" (Luka Škrlep) .

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1.
B-IMPACT project : eco-friendly and non-hazardous coatings for the protection of outdoor bronzes
Giulia Masi, Maëlenn Aufray, A. Balbo, E. Bernardi, Maria Chiara Bignozzi, Cristina Chiavari, J. Esvan, Nina Gartner, V. Grassi, Claudie Josse, Tadeja Kosec, Carla Martini, Cecilia Monticelli, Luka Škrlep, W. Sperotto, Erika Švara Fabjan, E. Tedesco, F. Zanotto, Luc Robbiola, 2020, published scientific conference contribution

Abstract: Application of protective coatings is the most widely used conservation treatment for outdoor bronzes. Eco-friendly and non-hazardous coatings are currently needed for conservation of outdoor bronze monuments. To fulfil this need, the M-ERA.NET European research project B-IMPACT (Bronze-IMproved non-hazardous PAtina CoaTings) aimed at assessing the protectiveness of innovative coatings for historical and modern bronze monuments exposed outdoors. In this project, two bronze substrates (historical Cu-Sn-Zn-Pb and modern Cu-Si-Mn alloys) were artificially patinated, by acid rain solution using dropping test and by "liver of sulphur" procedure (K2S aqueous solution) to obtain black patina, respectively. Subsequently, the application of several newly developed protective coatings was carried out and their performance was investigated by preliminary electrochemical tests. In the following steps of the work, the assessment of the best-performing coatings was carried out and their performance was compared to Incralac, one of the most widely used protective coatings in conservation practice. A multi-analytical approach was adopted, considering artificial ageing (carried out in representative conditions, including exposure to rain runoff, stagnant rain and UV radiation) and metal release, as well as visual aspect (so as to include aesthetical impact among the coating selection parameters) and morphological and structural evolution of the coated surfaces due to simulated outdoor exposure. Lastly, also the health impact of selected coatings was assessed by occupational hazard tests. The removability and re-applicability of the best-performing coatings were also assessed. The best alternatives to the conventional Incralac exhibited were: (i) fluoroacrylate blended with methacryloxy-propyl-trimethoxy-silane (FA-MS) applied on patinated Cu-Sn-Zn-Pb bronze and (ii) 3-mercapto-propyl-trimethoxysilane (PropS-SH) applied on patinated Cu-Si-Mn bronze.
Keywords: bronze, patina, protective coatings, eco-friendly, corrosion, aging
Published in DiRROS: 01.03.2024; Views: 90; Downloads: 47
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2.
Efficiency of novel photocatalytic coating and consolidants for protection of valuable mineral substrates
Andreja Pondelak, Sabina Dolenec, Jonjaua Ranogajec, Luka Škrlep, Snezana B. Vučetić, Vilma Ducman, Andrijana Sever Škapin, 2019, original scientific article

Abstract: In the process of protection and consolidation of valuable materials, the efficiency is the crucial property that needs to be considered. TiO2/ZnAl layered double hydroxide (LDH) coating and silicate- and carbonate-based consolidants were synthesized and proposed to be used for protection and consolidation of four porous mineral substrates: brick, stone, render and mortar. The photocatalytic efficiency of TiO2/ZnAl LDH coating, as well as consolidation efficiency of two consolidants, both applied on model substrates, were studied. The photocatalytic coating showed significant activity and performed well after the durability tests involving rinsing and freezing/thawing procedures. After treatment with both consolidants, a serious enhancement of consolidation of the used substrates was found. On the other hand, the application of TiO2/ZnAl LDH, as well as consolidants, caused negligible changes in the water vapour permeability values and in appearance of the porous mineral substrates, indicating a high level of compatibility.
Keywords: photocatalytic coating, consolidant, protection, conservation, porous substrate, cultural heritage
Published in DiRROS: 21.11.2023; Views: 208; Downloads: 152
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3.
UV light causes structural changes in microplastics exposed in bio-solids
S. S. Alavian Petroody, Seyed Hossein Hashemi, Luka Škrlep, Branka Mušič, Cornelis A. M. van Gestel, Andrijana Sever Škapin, 2023, original scientific article

Abstract: Bio-solids (biological sludge) from wastewater treatment plants are a significant source of the emission of microplastics (MPs) into the environment. Weakening the structure of MPs before they enter the environment may accelerate their degradation and reduce the environmental exposure time. Therefore, we studied the effect of UV-A and UV-C, applied at 70 °C, on three types of MPs, polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET), that are commonly found in sewage sludge, using three shapes (fibers, lines, granules). The MPs were exposed to UV radiation in bio-solid suspensions, and to air and water as control. The structural changes in and degradation of the MPs were investigated using Attenuated Total Reflectance–Fourier Transform Infrared Spectrometry (ATR-FTIR) and surface morphology was performed with SEM analysis. UV exposure led to the emergence of carbonyl and hydroxyl groups in all of the PP samples. In PE and PET, these groups were formed only in the bio-solid suspensions. The presence of carbonyl and hydroxyl groups increased with an increasing exposure time. Overall, UV radiation had the greatest impact on the MPs in the bio-solids suspension. Due to the surface-to-volume ratio of the tested samples, which influences the degradation rate, the fibers were more degraded than the other two plastic shapes. UV-A was slightly more effective at degrading the MPs than UV-C. These findings show that ultraviolet radiation in combination with an elevated temperature affects the structure of polymers in wastewater bio-solids, which can accelerate their degradation.
Keywords: microplastics, degradation, hydroxyl, carbonyl, ultraviolet light
Published in DiRROS: 14.11.2023; Views: 285; Downloads: 145
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4.
Development of multi-component fluoropolymer based coating on simulated outdoor patina on quaternary bronze
Tadeja 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: 316; Downloads: 170
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5.
Corrosion protection of brown and green patinated bronze
Tadeja Kosec, Živa Novak, Erika Švara Fabjan, Luka Škrlep, Andrijana Sever Škapin, Polonca Ropret, 2021, original scientific article

Abstract: Bronze surfaces, whether bare or patinated, tend to change when exposed to an outdoor atmosphere. Art made of bronze which is exposed to the outdoors is usually artificially patinated. This patina changes when exposed to rain, especially in polluted rain, where sulphuric, nitric or carbonic acids are present. In order to gain optimal protection of different patinas and consequently reduce the patina changes over the time different protection systems were developed, tested and tailored. Three types of patina (brown, green sulphate, and green persulphate) were prepared, protected and subsequently studied. The protections were based on two coatings (i) fluoropolymer based coating (FA-MS) and (ii) newly developed fluoropolymer based coating with addition of mercaptopropyl groups, named as alternative fluoropolymer coating (FA-MS-SH). Both the pure patinas applied on bronze surfaces as well as the bare bronze were electrochemically tested, first unprotected and then following the application of two different types of protection. After the protection was applied to the pa- tinas, the change in colour was defined. Different techniques were utilised in order to define the morphology and structure of the patinas, as well as the change in colour following application of the coating. It was shown that a fluoropolymer coating (FA-MS) provided the most efficient protection to bare bronze and the sulphate patina, while a newly proposed alternative fluoropolymer coating (FA-MS-SH) offered good protection to bare and brown patinated bronze. A mechanism for the protection of bare and patinated bronze was suggested.
Keywords: bronze, patina, protection
Published in DiRROS: 17.07.2023; Views: 279; Downloads: 159
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6.
Exploring the protection mechanism of a combined fluoropolymer coating on sulphide patinated bronze
Tadeja Kosec, Živa Novak, Erika Švara Fabjan, Luka Škrlep, Matjaž Finšgar, 2022, original scientific article

Abstract: When bronze or artificially patinated bronze is exposed to an outdoor environment that contains aggressive ions such as sulphates, nitrates, and carbonates, the surface of the bronze changes its appearance due to the formation of corrosion products on the surface. Research is being conducted on versatile protective measures that can be used to protect the surface from these changes. A recently synthesised fluoropolymer-based coating with mercaptopropyl groups, i.e. a 3-component fluoropolymer coating FA-MS-SH (silane-modified poly methylmethacrylate (MS) with added mercaptopropyltrimethoxy silane (SH) and a fluoroacrylate (FA)) was explored in detail in this work where its protective mechanism on sulphide patinated bronze was investigated. Electrochemical tests were conducted on the sulphide patinated bronze with and without the 3-component coating FA-MS-SH. Furthermore, FA, MS and SH alone and various combinations and concentrations of FA-MS were studied in order to determine the protective effect and properties of each component. Colour change and contact angle measurements were also defined. FIB-SEM measurements and GCIB-XPS depth profiles were carried out to study surface bonding with the sulphide patina in detail. A mechanism for the protection of sulphide patinated bronze was presented through the use of a multianalytical tool approach. It was shown that FA physisorbed on the patinated surface, while MS and blends of the components chemisorbed on the layer of sulphide patinated bronze, also resulting in the surface being efficiently protected from corrosion processes.
Keywords: bronze, protection, brown patina, fluoropolymer coating
Published in DiRROS: 31.05.2023; Views: 301; Downloads: 173
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7.
Properties of the fluoroacrylate and methacryloxypropyl-trimethoxysilane applied to a layer of Cu2O on bronze as either single or multi-component coatings
Luka Škrlep, Tadeja Kosec, Matjaž Finšgar, Andrijana Sever Škapin, Erika Švara Fabjan, 2023, original scientific article

Abstract: Various coatings have been developed and explored to protect bronze surfaces against the uncontrolled formation of different corrosion products when exposed to outdoor environments. In this research, the surfaces of artificially-formed oxidized bronze patinas (OB), consisting of Cu2O, were covered with either a single-component (fluoroacrylate, FA or methacryloxypropyl-trimethoxysilane, MS) or multi-component (a mixture of FA and MS, FA-MS) fluoropolymer coating and investigated. Variations in the concentration of each component in the coating were studied. Electrochemical tests were performed to determine the corrosion protection efficiency, followed by detailed surface analyses of the OBs, both uncoated and covered with single and multi-component coatings. A variety of investigative methods were used, including focused ion beam scanning electron microscopy (FIB-SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The coating made from a combination of FA and MS resulted in a very high protection efficiency. Despite the increased hydrophilicity of the single MS component, however, it was shown to efficiently protect the oxidized bronze surface. The FA-MS systems showed high hydrophobicity, but no improvement was measured in the efficiency of the corrosion protection when it was compared to the coating that contained 10% MS. According to XPS and ToF-SIMS imaging, the FA component of the FA-MS coating was not present only on the uppermost surface of the coating but throughout the whole coating, which could affect its corrosion protection efficiency.
Keywords: bronze, Cu2O layer on bronze, fluoropolymer coating, protection efficiency, surface spectroscopy
Published in DiRROS: 30.05.2023; Views: 297; Downloads: 159
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8.
Environmental hazard of polypropylene microplastics from disposable medical masks : acute toxicity towards Daphnia magna and current knowledge on other polypropylene microplastics
Anita Jemec Kokalj, Andraž Dolar, Damjana Drobne, Marjan Marinšek, Matej Dolenec, Luka Škrlep, Gregor Strmljan, Branka Mušič, Andrijana Sever Škapin, 2022, original scientific article

Abstract: The COVID-19 pandemic has increased the use of disposable plastics, including medical masks, which have become a necessity in our daily lives. As these are often improperly disposed of, they represent an important potential source of microplastics in the environment. We prepared microplastics from polypropylene medical masks and characterised their size, shape, organic chemical leaching, and acute toxicity to the planktonic crustacean Daphnia magna. The three layers of the masks were separately milled and characterised. Each of the inner frontal, middle filtering, and outer layers yielded different types of microplastics: fibres were obtained from the inner and outer layer, but irregular fragments from the middle layer. The shape of the obtained microplastics differed from the initial fibrous structure of the intact medical mask layers, which indicates that the material is deformed during cryo-milling. The chemical compositions of plastics-associated chemicals also varied between the different layers. Typically, the inner layer contained more chemicals related to antimicrobial function and flavouring. The other two layers also contained antioxidants and their degradation products, plasticisers, cross-linking agents, antistatic agents, lubricants, and non-ionic surfactants. An acute study with D. magna showed that these microplastics do not cause immobility but do physically interact with the daphnids. Further long-term studies with these microplastics are needed using a suite of test organisms. Indeed, studies with other polypropylene microplastics have shown numerous adverse effects on other organisms at concentrations that have already been reported in the environment. Further efforts should be made to investigate the environmental hazards of polypropylene microplastics from medical masks and how to handle this new source of environmental burden.
Keywords: COVID-19 pandemic, plastics-associated chemicals, Daphnia magna, fibres, fragments, nanofibres, polypropylene microplastics, single-use plastic
Published in DiRROS: 05.05.2023; Views: 320; Downloads: 200
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9.
Innovative calcium carbonate-based products to repair cracked cement mortars
Martina Zuena, Andreja Pondelak, Enrico Garbin, Matteo Panizza, Luca Nodari, Andrijana Sever Škapin, Luka Škrlep, Gilberto Artioli, Patrizia Tomasin, 2022, original scientific article

Abstract: The durability of Portland cement mortars is often affected by environmental factors, which can cause physicochemical and mechanical degradation processes. In this study, the performance of three products, calcium acetoacetate and calcium tetrahydrofurfuryloxide dissolved in two different solvents developed and tested as stone consolidants, was evaluated in terms of crack filling or sealing and consolidation. Realistic cracks were induced in quasibrittle cement mortar prisms using a custom-designed test rig. The effectiveness and the performance of the considered treatments, investigated on specimens, were evaluated by optical and scanning electron microscopy, colourimetry, water absorption rate, ultrasonic pulse velocity, and surface hardness measurements. Results revealed that, in the examined conditions, the products were more suitable as surface consolidants than as crack fillers.
Keywords: cement mortars, 20th century architecture conservation, calcium acetoacetate, calcium alkoxide, concrete repair, open access
Published in DiRROS: 04.05.2023; Views: 325; Downloads: 188
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10.
Influence of alkalis on the phase development of belite-sulfoaluminate clinkers
Barbara Čeplak, Katarina Šter, Maruša Mrak, Luka Škrlep, Mirijam Vrabec, Sabina Dolenec, 2022, original scientific article

Abstract: This paper presents a study on the influence of different amounts of alkalis (K2O and Na2O) on clinker phase formation, microstructure, phase composition and reactivity of belite-sulfoaluminate cement clinker. Using X-ray powder diffraction and scanning electron microscopy with energy dispersive spectrometry, it was found that the amount of C2S and C4AF increases with the incorporation of alkalis, while the amount of C4A3Ś and CŚ decreases. In addition to the major phases, the samples with alkalis also consist of minor phases such as C3A (tricalcium aluminate), KŚ (arcanite), and KC2Ś3 (Ca-langbeinite). The major ions in the major phases were substituted by alkali cations and some other ions (Ca2+, Al3+, Fe3+, S2-, S6+, Si4+). The alkalis also affect the microstructure of the clinker, e.g., the shape of the grains. Consequently, isothermal calorimetry was used to detect differences in hydration kinetics. The clinker with 2 wt. % K2O content was the most reactive, while the sample with 0.5 wt. % Na content was the least reactive. The latter was primarily influenced by the content of the main and minor phases of the clinker.
Keywords: BCSA clinker, microstrcuture, reactivity, alkalis, open access
Published in DiRROS: 06.12.2022; Views: 505; Downloads: 252
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