| 1. |
- Kim, Shin, et al.
(författare)
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Development of boron doped diamond electrodes material for heavy metal ion sensor with high sensitivity and durability
- 2023
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Ingår i: JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY. - : Elsevier BV. - 2238-7854 .- 2214-0697. ; 23, s. 1375-1385
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Tidskriftsartikel (refereegranskat)abstract
- We report on the optimized substrate pretreatment and deposition process conditions for boron-doped diamond (BDD) electrodes fabricated by hot-filament chemical vapor deposition (HFCVD). The optimized BDD electrode with a doping concentration of 8000 ppm showed high accuracy and precision in detecting Cd(II), Pb(II), and Cu(II) ions. In addition, this demonstrates excellent selectivity against external metal ions under the optimized stripping voltammetry measurement conditions. The detection limits of the target ions of Cd(II), Pb(II), and Cu(II) were 0.55 (+/- 0.05), 0.43 (+/- 0.04), and 0.74 (+/- 0.06) mg/L (S/N = 3), respectively. In real samples spiked with 100 mg/L Cd(II), Pb(II), and Cu(II), both the accuracy and precision of the BDD electrode were within 5%; the interference with organic matter was also negligible. The excellent selectivity and long-term stability indicate that the BDD electrode developed in this study are potentially useful for online water environment monitoring systems.
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| 2. |
- Bae, Kichang, et al.
(författare)
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Corrosion Resistance of Laser Powder Bed Fused AISI 316L Stainless Steel and Effect of Direct Annealing
- 2022
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Ingår i: Materials. - : MDPI. - 1996-1944. ; 15:18
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Tidskriftsartikel (refereegranskat)abstract
- Alloy parts produced by an additive manufacturing method with rapid heat transfer from fast melting and solidification have different microstructures, characteristics, and performances compared with materials made by the conventional process. In this study, the corrosion and oxidation resistance of SS316L, which was prepared by the powder bed fusion process, was compared with those of cold-rolled SS316L. Additionally, the surface oxide film on stainless steel was thoroughly assessed since the film has the greatest influence on the corrosion and oxidation resistance. The effect of heat treatment on corrosion and oxidation resistance of SS316L fabricated by additive manufacturing was investigated. The SS316L has a microstructure formed by sub-grain cells, in which locally concentrated alloying elements form a stable passive film. As a result, it has a higher level of corrosion resistance and oxidation resistance than conventional cold-rolled materials. However, it was confirmed that the sub-grain cell was removed by heat treatment, which resulted in the degradation of corrosion and oxidation resistance.
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| 3. |
- Choi, Young Joong, et al.
(författare)
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Controlled Lattice Thermal Conductivity of Transparent Conductive Oxide Thin Film via Localized Vibration of Doping Atoms
- 2021
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Ingår i: Nanomaterials. - : MDPI. - 2079-4991. ; 11:9
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Tidskriftsartikel (refereegranskat)abstract
- Amorphization using impurity doping is a promising approach to improve the thermoelectric properties of tin-doped indium oxide (ITO) thin films. However, an abnormal phenomenon has been observed where an excessive concentration of doped atoms increases the lattice thermal conductivity (kappa(l)). To elucidate this paradox, we propose two hypotheses: (1) metal hydroxide formation due to the low bond enthalpy energy of O and metal atoms and (2) localized vibration due to excessive impurity doping. To verify these hypotheses, we doped ZnO and CeO2, which have low and high bond enthalpies with oxygen, respectively, into the ITO thin film. Regardless of the bond enthalpy energy, the kappa(l) values of the two thin films increased due to excessive doping. Fourier transform infrared spectroscopy was conducted to determine the metal hydroxide formation. There was no significant difference in wave absorbance originating from the OH stretching vibration. Therefore, the increase in kappa(l) due to the excessive doping was due to the formation of localized regions in the thin film. These results could be valuable for various applications using other transparent conductive oxides and guide the control of the properties of thin films.
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| 4. |
- Khairy, Kholida Tul, et al.
(författare)
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Thermochromic properties of vanadium oxide thin films prepared by reactive magnetron sputtering at different oxygen concentrations
- 2023
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Ingår i: Vacuum. - : Elsevier. - 0042-207X .- 1879-2715. ; 210
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Tidskriftsartikel (refereegranskat)abstract
- Vanadium dioxide (VO2) is a thermochromic (TC) material, exhibits a reversible transmittance change in the near-infrared (NIR) region upon heating above a critical temperature tic, due to an insulator-to-metal phase transition. Numerous studies on the V-O system can be found in the literature, including the synthesis of VO2 films. The phase diagram of the V-O system involves complicated suboxide phases that prevent pure VO2 for-mation and obscures quantitative analysis. Here, VO2 thin films were systematically prepared with various ox-ygen flow ratios (r) using reactive magnetron sputtering. Thin films prepared with r = 4.1% show dominant VO2 phase and the highest TC performance. The r -range producing dominant VO2 phase is found to be narrow: 3.7% < r<4.2%. At lower and higher r, TC characteristics are shown to be accompanied, as expected, by electrical conductivity changes, but also by microstructure transformations. The latter producing textured films that gradually develop upon cycling around tic. In particular, a change of texture, yielding oriented VO2 crystallites, is observed by in-situ XRD around tic. Our results shed light on the VO2 formation and associated structural, chemical and electrical properties under various oxidizing conditions during magnetron sputtering, which calls for careful preparation and strategies to stabilize the VO2 phase.
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| 5. |
- Kim, Seohan, et al.
(författare)
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Embedded nanopattern for selectively suppressed thermal conductivity and enhanced transparency in a transparent conducting oxide film
- 2022
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Ingår i: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 103:Part A
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Tidskriftsartikel (refereegranskat)abstract
- Transparent conductive oxide (TCO) thin films are cornerstones in many optoelectronic applications including displays, photovoltaics and touchscreens. In these devices, thin films with simultaneous high optical transparency and electrical conductivity are needed. Ideally, heat generated during normal device operation must ideally be compensated for to achieve optimum functionality. One possible way to address the thermal management problem is adding thermoelectric (TE) properties to TCO films. However, improving TE properties while maintaining optimal electrical conductivity and optical transparency is challenging: thermal and electrical transport properties are deeply intertwined. Here, we demonstrate an approach allowing for independent optimization of optical transparency, electrical conductivity and thermal conductivity. An embedded nanopattern structure is filled with indium tin oxide (ITO) and sandwiched between two ITO layers. The resulting triplelayered structure exhibits reduced thermal conductivity and excellent electrical conductivity. This is made possible by electron channels in the embedded ITO nanopattern that electrically connect top and bottom layers, while at the same time limiting phonon-mediated heat conduction. The filling fraction and thickness of the nanopattern are adjusted to improve optical transmission, achieving transparency higher than bare ITO film. The result is a transparent TCO triple layer film with simultaneous high TCO and thermoelectric figures of merit.
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| 6. |
- Kim, Seohan, et al.
(författare)
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Embedded Oxidized Ag-Pd-Cu Ultrathin Metal Alloy Film Prepared at Low Temperature with Excellent Electronic, Optical, and Mechanical Properties
- 2022
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 14:13, s. 15756-15764
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Tidskriftsartikel (refereegranskat)abstract
- Most transparent conducting materials are based on Sn:In2O3 (ITO). When applied onto flexible substrates, ITO can be prepared in an oxide-metal-oxide (OMO) configuration, typically ITO/Ag/ITO, where the ductility of the embedded metal layer is intended to reduce the mechanical brittleness and improve the electrical conductivity of the OMO multilayer. Hitherto, the lower limit of the thickness of the Ag layer has been limited by the percolation threshold, which limits the Ag layer to be thicker than similar to 10 nm to avoid agglomeration and to ensure conductivity and structural stability. Metal layers of thicknesses below 10 nm are, however, desirable for obtaining OMO coatings with better optical properties. It is known that agglomeration of the metal layer can, to some extent, be suppressed when substituting Ag by an Ag-Pd-Cu (APC) alloy. APC-based OMO films exhibit excellent optical and electrical properties, but still continuous APC films well below 10 nm thickness cannot be achieved. In this work we demonstrate that controlled oxidation of APC results in smooth, ultrathin APC:O continuous coatings (of thickness similar to 5 nm) on ITO-coated PET substrates. Moderate oxidation yields superficial PdOx formation, which suppresses Ag agglomeration, while still maintaining excellent conductivity. On the other hand, extensive oxidation of APC leads to extensive Pd oxide nucleation deteriorating the conductivity of the film. The ITO/APC:O/ITO films exhibit low resistivity, attributed to a high Hall mobility associated with suppressed agglomeration, good stability in high humidity/temperature environments, superior transmittance in the visible and infrared region, and excellent mechanical bending properties, thus providing new opportunities for fabricating superior transparent conducting coatings on polymer substrates.
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| 7. |
- Kim, Seohan, et al.
(författare)
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Hydrogen-driven surface amorphization of the transparent oxide semiconductor thin-films for photovoltaic applications
- 2021
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Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 555
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Tidskriftsartikel (refereegranskat)abstract
- Crystalline transparent conductive oxides are promising candidates as front electrodes in electronic devices due to the high electron mobility and good optical transparency in the visible region. However, the rough surface morphology resulting from the grain growth during the deposition and post-annealing process triggers severe drawbacks in their thin-film applications. Here, we demonstrate the hydrogen-driven surface amorphization of the crystalline In?Sn?O (c-ITO) thin film. By introducing hydrogen gas during the deposition process, the surface of the c-ITO thin film is selectively amorphized, allowing for the smooth surface morphology while preserving the advantages of the crystalline thin film. The progressive surface amorphization of c-ITO thin film offers the tunability of the work function, leading to the improved power conversion efficiency of the thin-film solar cell. Our work provides a facile method to realize the smooth surface morphology of the c-ITO thin films, which can be further utilized for a wide range of crystalline thin films for optoelectronic applications.
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| 8. |
- Lee, Nam-Young, et al.
(författare)
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Performance of Insoluble IrO2 Anode for Sewage Sludge Cake Electrodehydration Application with Respect to Operation Conditions
- 2022
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Ingår i: Coatings. - : MDPI. - 2079-6412. ; 12:6
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Tidskriftsartikel (refereegranskat)abstract
- The efficient management of wastewater and sewage sludge treatment are becoming crucial with industrialization and increasing anthropological effects. Dehydration of sewage sludge cakes (SSCs) is typically carried out using mechanical and electrochemical processes. Using the mechanical dehydration process, only a limited amount of water can be removed, and the resultant SSCs have a water content of approximately 70-80 wt.%, which is significantly high for land dumping or recycling as solid fuel. Dumping high-moisture-content SSCs in land can lead to leakage of hazardous wastewater into the ground and cause economic loss. Therefore, dehydration of SSCs is crucial. Contemporary treatment methods focus on the development of anode materials for the electrochemical processes. IrO2 is an insoluble anode material that is eco-friendly, less expensive, and exhibits high chemical stability, and it has been widely used and investigated in wastewater treatment and electrodehydration (ED) industries. Herein, we evaluated the performance of the ED system developed using IrO2 anode material. The operating conditions of the anode such as reaction time, sludge thickness, and voltage on SSC were optimized. The performance of the ED system was evaluated based on the moisture content of SSCs after dehydration. The moisture content decreased proportionally with the reaction time, sludge thickness, and voltage. The moisture content of 40 wt.% was determined as the optimum quantity for land dumping or to be used as recycled solid fuel.
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| 9. |
- Park, Sungmin, et al.
(författare)
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Hydrogen-driven dramatically improved mechanical properties of amorphized ITO-Ag-ITO thin films
- 2021
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 11:6, s. 3439-3444
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Tidskriftsartikel (refereegranskat)abstract
- An oxide/metal/oxide (OMO) multi-structure, which has good electrical, optical, and mechanical stability, was studied as a potential replacement of polycrystalline In-Sn-O (ITO). However, the degradation of mechanical properties caused by the polycrystalline structure of the top layer forming on the polycrystalline metal layer needs to be improved. To address this issue, we introduced hydrogen in the oxide layers to form a stabilized amorphous oxide structure despite it being deposited on the polycrystalline layer. An ITO/Ag/ITO (IAI) structure was used in this work, and we confirmed that the correct amount of hydrogen introduction can improve mechanical stability without any deterioration in optical and electrical properties. The hydrogen presence in the IAI as intended was confirmed, and the assumption was that the hydrogen suppressed the formation of microcracks on the ITO surface due to low residual stress that came from decreased subgap level defects. This assumption was clearly confirmed with the electrical properties before and after dynamic bending testing. The results imply that we can adjust not only IAI structures with high mechanical stability due to the right amount of hydrogen introduction to make stabilized amorphous oxide but also almost all oxide/metal/oxide structures that contain unintended polycrystalline structures.
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| 10. |
- Österlund, Lars, et al.
(författare)
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Transparent multifunctional cover glass coating for solar energy applications
- 2023
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In photovoltaics, the cover glass module has hitherto not yet been fully optimized for its purpose. Instead quite conventional architectural glass is used. In a recent review of the state-of-the-art on UV down converting dopants [1], a way forward to improve cover glasses was presented. Some of these possibilities, and others are covered in the present paper. We present possibilities to add several functionalities, instead of using dopants in the glass composition, including omnidirectional antireflection, dynamic solar control, and self-cleaning. Omni-directional anti-reflective coatings, were made by colloidal lithography templating methods on iron free glass, realizing nanopillar structures with dimensions /2 exploiting Mie scattering for wide angle light collection (Fig. 1). Yttrium oxyhydride (YHO) coatings were deposited on the nanopillar structures using magnetron sputtering methods [2]. The YHO film blocks UV light and photo-darkens upon solar light absorption and reverts to its transparent state in dark in reproducible manner [2]. In addition, the YHO film also becomes hydrophobic upon photo-darkening, acting as a self-cleaning layer. The fabricated coatings were compared with bare glass substrates. The results reveal suppressed reflectance, with acceptable anti-reflective properties up to about 50 degrees. Solar light modulation of a thin 100 nm YHO coating is below 10% thus having high transmittance throughput while allowing for solar cell life-time saving by removal of excess irradiance. Finally, the surface energy of the YHO coated glass structures are presented, demonstrating synergetic chemical and structural (the Lotus effect), showing promising self-cleaning properties. In conclusion, we show possibilities to combine photonic and chromogenic principles with suitable surface chemistry to achieve high-performance cover glass for solar energy application..
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