1. Time and potential-resolved comparison of copper disc and copper nanoparticles for electrocatalytic hydrogenation of furfuralNik Maselj, Vasko Jovanovski, Francisco Ruiz-Zepeda, Matjaž Finšgar, Tamara Klemenčič, Jan Trputec, Ana Rebeka Kamšek, Marjan Bele, Nejc Hodnik, Primož Jovanovič, 2023, original scientific article Abstract: Herein, a comparative analysis of two case example catalysts for electrocatalytic hydrogenation (ECH) of furfural under acidic conditions, namely a copper polycrystalline disc and copper nanoparticles dispersed on carbon support, is performed. To gain a detailed insight on ECH trends, a task-specific methodology is employed based on electrochemistry–mass spectrometry coupling, which enabled time- and potential-resolved detection of volatile ECH products, i.e., 2-methylfurane (2-MF) and H2. In this way, the ability to elucidate potential-dependent product distribution for the two catalysts, namely faradaic efficiency, is achieved. Accordingly, the nanoparticulate analog is significantly more active toward competitive hydrogen evolution reaction and 2-MF production, whereas the polycrystalline sample is more selective toward furfuryl alcohol. The observed differences in ECH are ascribed to alterations in surface domains, which is supported by surface-sensitive lead underpotential deposition characterization.
Keywords: baker, nanodelci, elektrokataliza, copper, nanoparticles, electrocatalytic hydrogeneration
Published in DKUM: 19.04.2024; Views: 161; Downloads: 5
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2. Development of a novel NiCu nanoparticle-loaded polysaccharide-based hydrogel for 3D printing of customizable dressings with promising cytotoxicity against melanoma cellsLaura Činč Ćurić, Maša Šuligoj, Maja Ibic, Nina Marovič, Boštjan Vihar, Matej Vesenjak, Polona Dobnik-Dubrovski, Nejc Novak, Janja Stergar, Irena Ban, Uroš Maver, Marko Milojević, Tina Maver, 2023, original scientific article Keywords: nanoparticle-loaded hydrogels, 3D printed dressings, polysaccharides, nickel-copper nanoparticles, cytotoxic activity
Published in DKUM: 03.04.2024; Views: 260; Downloads: 12
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3. Patterns of Copper Bioaccumulation and Translocation in Grapevine Grafts Depending on RootstocksStanko Vršič, Mojca Gumzej, MARIO LEŠNIK, Andrej Perko, Borut Pulko, 2023, original scientific article Abstract: The long-term use of copper (Cu) fungicides in viticulture in Europe has led to Cu accumulation in vineyard top soils. However, less is known about the accumulation of Cu in grapevine grafts after the callusing process/before planting in the nursery. This paper presents the capacity of 5BB and SO4 rootstocks to accumulate Cu, as well as the patterns of translocation in the grafts. After heat forcing (callusing), the grapevine grafts of Sauvignon Blanc on 5BB and SO4 rootstocks were grown in pots for six months in a glasshouse and exposed to various Cu formulations (Cu-oxychloride, Cu-gluconate) and concentrations in peat (50, 150, 500, and 1000 mg Cu of dry weight (DW)). In addition to monitoring the shoot growth dynamics and analyzing the copper content in graft organs, bioaccumulation (BAFs) and translocation factors (TFs) of Cu were calculated. The mean Cu concentrations were ranked as follows: roots (15–164) > rootstock trunks (8–38) > canes (5–21) mg kg−1 DW. The Cu concentrations depended on the Cu formulation and concentration in the substrate. Higher Cu content was found in the roots of both rootstocks (5BB and SO4, 23–155 and 15–164 mg kg−1 DW, respectively) and the lowest in the canes (less than 10 mg kg−1 DW) of grafts grown in Cu-oxychloride-treated peat. Based on the BAFs and TFs, both rootstocks could be considered as Cu exclusive. A higher translocation rate was determined in systemic Cu-gluconate and SO4 rootstock. With shoot length measurements, the significant inhibitory effects of Cu on grapevine grafts growth could not be confirmed, despite the inhibitory effects that were clearly expressed in the first two months of growth. Soils containing more than 500 mg Cu/kg−1 are less suitable for growing vine grafts.
Keywords: grapevine grafts, copper accumulation, Cu-oxychloride, Cu-gluconate, 5BB and SO4 rootstocks
Published in DKUM: 08.12.2023; Views: 457; Downloads: 29
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4. Electrochemical and surface analysis of 2-phenylimidazole adsorbed on copper from chloride solutionMatjaž Finšgar, Klodian Xhanari, 2018, original scientific article Abstract: The electroanalytical and surface characterization of copper immersed in 3 wt.% NaCl solution containing 1 mM of 2-phenylimidazole (2PhI) is presented. It was proven that 2PhI can be employed as corrosion inhibitor for copper using various electrochemical analyses, such as cyclic voltammetry, chronopotentiometry, electrochemical impedance spectroscopy, and potentiodynamic curve measurements. The adsorption of 2PhI on copper was further analyzed by 3D-profilometry, attenuated total reflectance Fourier transform infrared spectroscopy, contact angle measurements, and scanning electron microscopy equipped with an energy dispersive X-ray spectrometer. This system was therefore comprehensively described by various analytical approaches.
Keywords: corrosion inhibitor, copper, electrochemical impedance spectroscopy, EIS, cyclic voltammetry, attenuated total reflectance Fourier transform infrared, ATR-FTIR
Published in DKUM: 17.01.2019; Views: 2084; Downloads: 392
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5. Synthesis and characterization of hardened Cu-Fe-Ni-P alloyGoran Brovč, Goran Dražić, Blaž Karpe, Igor Đorđević, Gorazd Lojen, Borut Kosec, Milan Bizjak, 2015, original scientific article Abstract: In the manufacturing industry of electrical contacts, the prohibition of the use of toxic metals (Cd, Be), and desire to avoid the alloying with precious metals (Ag) has created a need for new alloys with good electrical conductivity and high mechanical properties at elevated temperatures. As a potentially useful material for this purpose, we have analyzed the continuously cast Cu-Fe-Ni-P alloy in various heat treatment conditions. Sequence of phase transformations during heat treatment was followed by 4 point D.C. electrical resistivity measuring method, and analyzed by scanning (SEM) and transmission (TEM) electron microscopy. Measurements of Vickers hardness and electrical conductivity after various heat treatment procedures indicate on high potential of Cu-Fe-Ni-P alloys as a material for electrical contacts.
Keywords: copper alloys, precipitation hardening, electrical contacts, electrical conductivity
Published in DKUM: 03.07.2017; Views: 2320; Downloads: 97
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6. Analysis of a strain rate field in cold formed material using the visioplasticity methodLeo Gusel, Rebeka Rudolf, Borut Kosec, 2009, other scientific articles Abstract: In this paper the visioplasticity method is used to find the complete velocity and strain rate distributions from the experimental data, using the finite-difference method. The data about values of strain rates in plastic re- gion of the material is very important for calculating stresses and the prediction of product quality. Specimens of copper alloy were extruded with different lubricants and different coefficients of friction and then the strain rate distributions were analysed and compared. Significant differences in velocity and strain rate distributions were obtained in some regions at the exit of the deformed zone.
Keywords: forward extrusion, copper alloy, visioplasticity, strain rate, lubrication
Published in DKUM: 03.07.2017; Views: 966; Downloads: 141
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7. Investigation of phytotoxicity regarding copper fungicides applied to applesMario Lešnik, Stanislav Vajs, Vesna Gaberšek, Vili Kurnik, 2013, original scientific article Keywords: apple, copper, phytotoxicity, additives, kaolin clay, pine resin, milk protein
Published in DKUM: 21.12.2015; Views: 1446; Downloads: 38
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8. Modified surface of Cu, Zn, Cu10Zn and Cu40Zn with expression of hydrophobic properties for the purpose of corrosion protectionGregor Žerjav, 2015, doctoral dissertation Abstract: Copper and its alloys are soft and malleable metals and are often used for fabricating structures and monuments open to the atmosphere where they are subject to corrosion attack. There are many ways to protect metal against corrosion: corrosion inhibitors, protective layers, hydrophobic layers.
He aim was to develop a simple technological process for forming hydrophobic, protective coatings for protection of Cu, Cu10Zn, Cu40Zn and Zn under conditions of atmospheric corrosion as tested in simulated urban rain. Carboxylic acids form self-assembled hydrophobic layers by adsorption to the positively charged metal surfaces via their carboxylic group. Corrosion inhibitors are often used to protect metals against corrosion in closed system. Most used corrosion inhibitors to protect Cu and its alloys is benzotriazole (BTAH) which showed good results in different environments. 2-mercaptobenzimidazole (2-MBI) is a derivative of BTAH with stronger affinity to adsorb on the Cu surface and showed good corrosion protection results in acidic solutions.
Corrosion protection properties of the layers were tested with the use of electrochemical methods: potentiodynamic polarization and electrochemical impedance spectroscopy. The results were complement with immersion test where the weight loss was obtained. The properties of the layers were explored with surface-analytical methods: measurement of the contact angles, X-ray photoelectron spectroscopy, scanning electron microscopy with a chemical analysis and glow discharge optical emission spectroscopy.
First the optimal conditions to produce hydrophobic coatings with the use of carboxylic acids were explored. The inhibition efficiency increased with increasing carbon chain length, longer preparation time in ethanol solution and increasing concentration of carboxylic acid.
The inhibition of corrosion of Cu, Cu10Zn, Cu40Zn and Zn in simulated urban rain was further studied using the self-assembly of BTAH, 2-MBI and SA in ethanol solution, as individual inhibitors and in combinations. The morphology of layers differed greatly. The results of electrochemical measurements and weight loss immersion test ruled out BTAH as a possible inhibitor, unless combined with stearic acid. In the cases of Cu40Zn and Zn it even promoted corrosion. In contrast, 2-MBI gave good results, and even better in combination with stearic acid. SA layers provided the best long term corrosion protection of all tested inhibitors and exhibited the highest contact angles. 2-MBI provided less protection than SA. Combining organic inhibitor and stearic acid improves the corrosion protection properties of the self-assembled layers compare to individual layers.
To make the procedure of layer preparation more appropriate for industrial application the time of immersion was decreased. Layers prepared on Cu with 1 min immersion time showed adequate corrosion protection of Cu in simulated urban rain. We also studied the possibility of combining SA with vitamin E in the layer preparation procedure. The modified layers formed with combination of Vitamin E and SA showed better corrosion inhibition properties for Cu and Cu40Zn in simulated urban rain as individual layers.
Combining inhibitor and carboxylic acid together to prepare corrosion protective layers has a positive effect on the corrosion properties of the layers. Layers made combining corrosion inhibitor and carboxylic acid showed better corrosion protection than individual layers. The self-assembling process is a fast process shown by the tests made on the Cu layers with shorter immersion time. The addition of Vitamin E in the preparation of layers with carboxylic acids shows a positive effect on the corrosion properties of layers.
Keywords: copper, brass, corrosion, simulated urban rain, inhibitors, carboxylic acid, benzotriazole, 2-mercaptobenzimidazole
Published in DKUM: 30.11.2015; Views: 1800; Downloads: 174
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9. The influence of copper on the decarburization and recrystallization of Fe-Si-Al alloysDarja Steiner Petrovič, Monika Jenko, Valter Doleček, 2006, original scientific article Abstract: The decarburization and recrystallization of Fe-Si-Al alloys containing copper was investigated. The decarburization annealing of non-oriented electrical steel sheets produced from Fe-Si-Al alloys depends on the chemical reactions between the gas mixture and the carbon at the steel's surface. The carbon diffusion, the temperature of decarburization annealing, the composition of the gas mixture and the chemical composition of the steel are the influencing parameters that determine the kinetics and the mechanism of decarburization. The decarburization of Fe-Si-Al alloy with the mass fraction of 0.24% and 0.43% of copper was compared with the decarburization of an Fe-Si-Al alloy with a very small amount of copper (0.01%). The decarburization annealing was performed in a H2-H2O gas mixture at 840 °C. The residual carbon content was determined by analytical chemical method. The alloys were also recrystallized in hydrogen at 980 °C. Microstructure of samples after decarburization and recrystallization annealing was investigated with optical microscopy.
Keywords: alloys, recrystallization, decraburization, non-oriented electrical sheet steels, copper, carbon
Published in DKUM: 10.07.2015; Views: 1268; Downloads: 101
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