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W.J. Stepniowski
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5 records found
1
Journal article
(2020)
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Wojciech Stepniowski, Damian Paliwoda, Shoshan Abrahami, Marta Michalska-Domańska, Kai Landskron, Ivan Buijnsters, Arjan Mol, Herman Terryn, Wojciech Z. Misiolek
Self-organized anodization of copper in 0.1 M Na2CO3 electrolyte was studied in order to obtain nanostructured oxide surface on the metal substrate. Linear sweep voltammetry (LSV) revealed that the most suitable voltage range for anodic film formation is from 3 to 31 V. In this range (except between 3 and 7 V), the oxide is formed as nanorods, with the diameter of the anodically grown nanostructures increasing with the applied voltage. The smallest diameter of the nanorods was found to be 28 ± 9 nm (15 V), while the greatest diameter was 109 ± 15 nm (30 V). X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Raman spectroscopy pointed out that the nanorods consist of crystalline CuO (tenorite) and Cu2O (cuprite), and amorphous Cu(OH)2. Moreover, the greater the anodizing voltage, the greater the CuO content versus Cu2O. The formed nanostructured materials may find applications in photocatalysis and catalytic electrochemical reduction of carbon dioxide into light hydrocarbons.
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Self-organized anodization of copper in 0.1 M Na2CO3 electrolyte was studied in order to obtain nanostructured oxide surface on the metal substrate. Linear sweep voltammetry (LSV) revealed that the most suitable voltage range for anodic film formation is from 3 to 31 V. In this range (except between 3 and 7 V), the oxide is formed as nanorods, with the diameter of the anodically grown nanostructures increasing with the applied voltage. The smallest diameter of the nanorods was found to be 28 ± 9 nm (15 V), while the greatest diameter was 109 ± 15 nm (30 V). X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Raman spectroscopy pointed out that the nanorods consist of crystalline CuO (tenorite) and Cu2O (cuprite), and amorphous Cu(OH)2. Moreover, the greater the anodizing voltage, the greater the CuO content versus Cu2O. The formed nanostructured materials may find applications in photocatalysis and catalytic electrochemical reduction of carbon dioxide into light hydrocarbons.
Journal article
(2018)
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Wojciech J. Stepniowski, Marcin Moneta, Krzysztof Karczewski, Marta Michalska-Domanska, Tomasz Czujko, Johannes M.C. Mol, Josephus G. Buijnsters
Anodic aluminum oxide was formed by employing mild and hard anodizing in sulfuric acid followed by mild anodizing in oxalic acid without oxide removal in-between at 40 and 45 V. Such multi-step anodizing, combining hard anodizing in sulfuric acid with mild anodizing in oxalic acid allowed to form a highly-ordered nanoporous template with a barrier layer at the pore bottoms thin enough for further processing. Four different conditions of electrochemical barrier layer thinning, with varied voltage steps and their time durations, were investigated. Optimized conditions allowed to provide conductivity at the pore bottoms and made the nanoporous oxide templates suitable for electrodeposition. It was found that the most effective barrier layer thinning approach employs voltage steps Un + 1 = 0.75·Un with each step (n) being 10 s long. To check applicability of the formed templates, copper electrodeposition from sulfate-borate bath was done. Copper nanowires with average length of about 14–16 μm and diameter of about 35–40 nm were obtained by using through-hole AAO templates.
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Anodic aluminum oxide was formed by employing mild and hard anodizing in sulfuric acid followed by mild anodizing in oxalic acid without oxide removal in-between at 40 and 45 V. Such multi-step anodizing, combining hard anodizing in sulfuric acid with mild anodizing in oxalic acid allowed to form a highly-ordered nanoporous template with a barrier layer at the pore bottoms thin enough for further processing. Four different conditions of electrochemical barrier layer thinning, with varied voltage steps and their time durations, were investigated. Optimized conditions allowed to provide conductivity at the pore bottoms and made the nanoporous oxide templates suitable for electrodeposition. It was found that the most effective barrier layer thinning approach employs voltage steps Un + 1 = 0.75·Un with each step (n) being 10 s long. To check applicability of the formed templates, copper electrodeposition from sulfate-borate bath was done. Copper nanowires with average length of about 14–16 μm and diameter of about 35–40 nm were obtained by using through-hole AAO templates.
The effect of the separation between electrodes on the main output parameters of the anodic aluminum oxide structure, namely the pore size, the cell size, the thickness and the regularity ratio was investigated. Pure aluminum foils were anodized in 0.3 M oxalic acid at different combinations of electrode separations (1.5, 3 and 6 cm), anodization voltages (30, 45 and 60 V) and temperatures (10, 20 and 30 °C). Whereas cell size and thickness appeared to be independent on the electrode separation, minor effects emerged for the pore size and significant effects emerged for the regularity ratio. The latter decreased with electrode separation at the lowest anodization voltage, but increased for the other voltages, especially at intermediate value of 45 V. For the temperature series, the regularity ratio decreased with separation at highest and, mostly, lowest temperature, while increased at intermediate temperature. Therefore, in addition to the major fabrication parameters of anodization voltage, current density, temperature and electrolyte concentration, it appears that the electrode separation may also cause relevant effects on the pattern quality, which should be taken into account for careful control of this nanofabrication process.
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The effect of the separation between electrodes on the main output parameters of the anodic aluminum oxide structure, namely the pore size, the cell size, the thickness and the regularity ratio was investigated. Pure aluminum foils were anodized in 0.3 M oxalic acid at different combinations of electrode separations (1.5, 3 and 6 cm), anodization voltages (30, 45 and 60 V) and temperatures (10, 20 and 30 °C). Whereas cell size and thickness appeared to be independent on the electrode separation, minor effects emerged for the pore size and significant effects emerged for the regularity ratio. The latter decreased with electrode separation at the lowest anodization voltage, but increased for the other voltages, especially at intermediate value of 45 V. For the temperature series, the regularity ratio decreased with separation at highest and, mostly, lowest temperature, while increased at intermediate temperature. Therefore, in addition to the major fabrication parameters of anodization voltage, current density, temperature and electrolyte concentration, it appears that the electrode separation may also cause relevant effects on the pattern quality, which should be taken into account for careful control of this nanofabrication process.
Journal article
(2017)
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Wojciech J. Stepniowski, Stevan Stojadinović, Rastko Vasilić, Nenad Tadić, Krzysztof Karczewski, Shoshan T. Abrahami, Josephus G. Buijnsters, Johannes M C Mol
Copper foil was anodized in 1 M KOH at potentials ranging from −400 to −100 mV vs. Ag|AgCl electrode. Cyclic voltammetry showed a distinct peak with a maximum at around −150 mV. For anodizing at −100 and −200 mV, nanowires with diameters of ca. 19 and 24 nm respectively were found to be grown. Moreover, photoluminescence and X-ray diffraction show that the dominant phase is the CuO phase. At lower potentials, cuboidal micron sized crystals were formed and Cu2O was found to be the major phase.
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Copper foil was anodized in 1 M KOH at potentials ranging from −400 to −100 mV vs. Ag|AgCl electrode. Cyclic voltammetry showed a distinct peak with a maximum at around −150 mV. For anodizing at −100 and −200 mV, nanowires with diameters of ca. 19 and 24 nm respectively were found to be grown. Moreover, photoluminescence and X-ray diffraction show that the dominant phase is the CuO phase. At lower potentials, cuboidal micron sized crystals were formed and Cu2O was found to be the major phase.
Journal article
(2016)
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Wojciech Stepniowski, T. Durejko, M. Michalska-Domanska, M. Lazinska, J. Aniszewska
Technical purity aluminum was subjected to laser pre-treatment. Subsequently, self-organized anodization in sulfuric acid was performed in order to form nanoporous oxide layer. The influence of the laser pre-treatment operating conditions and grain size of the direct solidified aluminum on the formation of the nanoporous anodic aluminum oxide was studied on the base of FE-SEM images quantitative analyses. It was found there is no significant influence of laser pre-treatment on pore diameter, interpore distance and thickness of the grown oxide. Furthermore, fast Fourier transform-based quantitative image analysis showed that arrangement of the nanoporous alumina grown on the laser pre-treated aluminum is comparable to the arrangement of nanopores formed on high-purity aluminum without any pre-treatment. These findings were supplemented by the circularity analysis of the grown nanopores. This means that laser-treated aluminum elements can be anodized without significant decreases in the quality of the anodic oxides.
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Technical purity aluminum was subjected to laser pre-treatment. Subsequently, self-organized anodization in sulfuric acid was performed in order to form nanoporous oxide layer. The influence of the laser pre-treatment operating conditions and grain size of the direct solidified aluminum on the formation of the nanoporous anodic aluminum oxide was studied on the base of FE-SEM images quantitative analyses. It was found there is no significant influence of laser pre-treatment on pore diameter, interpore distance and thickness of the grown oxide. Furthermore, fast Fourier transform-based quantitative image analysis showed that arrangement of the nanoporous alumina grown on the laser pre-treated aluminum is comparable to the arrangement of nanopores formed on high-purity aluminum without any pre-treatment. These findings were supplemented by the circularity analysis of the grown nanopores. This means that laser-treated aluminum elements can be anodized without significant decreases in the quality of the anodic oxides.