| 1. |
- Akinsinde, Lewis O., et al.
(författare)
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Surface characterization and resistance changes of silver-nanowire networks upon atmospheric plasma treatment
- 2021
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 550
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Tidskriftsartikel (refereegranskat)abstract
- Highly conductive silver-nanowire (Ag-NW) networks are used in composite materials as conductive channels. Their resistance tuning can be accomplished by changing the Ag-NW concentration, and, therefore, changing the network structure. In this study, an alternative pathway to resistance engineering of conductive Ag-NW networks by local atmospheric plasma treatment is employed. The corresponding changes in nanowire network morphology and crystallinity as a function of plasma etching time are investigated by time-resolved grazingincidence X-ray scattering, field-effect scanning electron microscopy, and X-ray photoelectron spectroscopy. Three characteristic etching phases are identified. The first two phases enable the controlled engineering of the electrical properties with different rates of resistance change, which results from changes in nanowire shape, network morphology, and different oxidation rates. Phase III is characterized by pronounced fragmentation and destruction of the Ag-NW networks. These results show the feasibility of atmospheric plasma treatments to tune the local electrical properties of conductive Ag-NW networks. Furthermore, we present a physical Monte Carlo model explaining the electrical network properties as a function of plasma etching time based on the network connectivity and a constant plasma etching rate of 570 ng s-1 cm-2.
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| 2. |
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| 3. |
- Li, He, et al.
(författare)
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Nitrogen-doped NiCo2O4 nanowires on carbon paper as a self-supported air cathode for rechargeable Zn-air batteries
- 2023
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 48:67, s. 26107-26118
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Tidskriftsartikel (refereegranskat)abstract
- A noble-metal-free bifunctional electrocatalyst with outstanding activity and stability is of great importance for the development of rechargeable zinc-air batteries (ZABs). Herein, we employed a facile strategy to fabricate nitrogen-doped NiCo2O4 nanostructures on carbon paper as a binder-free air cathode for rechargeable ZABs. An optimized process of nitrogen plasma treatment has enhanced the electrical conductivity of the metal oxide and induced abundant active sites into the crystal structures, resulting in enhanced electrocatalytic activities toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Notably, mild plasma treatment leads to efficient N doping while the morphology and specific surface area of the catalyst both remain unchanged. The air cathode with NiCo2O4 doped with nitrogen in 2 min plasma treatment and integrated into a zinc-air battery with liquid electrolyte provided a small charge-discharge voltage gap and distinguished cycling stability superior to the air cathode with noble-metal catalyst counterparts. Furthermore, the solid-state zinc-air battery with this material displays excellent stability with just a small increase of the charge-discharge voltage gap over 20 h of operation. This work illustrates the promising potential of plasma treatment in the fabrication of high-performance catalysts.
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| 4. |
- Pingen, Katrin, et al.
(författare)
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High growth rate magnetron sputter epitaxy of GaN using a solid Ga target
- 2024
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Ingår i: Vacuum. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0042-207X .- 1879-2715. ; 220
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Tidskriftsartikel (refereegranskat)abstract
- Magnetron sputter epitaxy (MSE) is a promising processing route for group-III nitride semiconductors, with the potential to enable high-quality and low cost GaN growth for widespread use. However, fundamental techno-logical hurdles must be overcome to enable the adoption of MSE in industrial production. Here, we present a new UHV-compatible magnetron design with high-performance cooling, enabling high GaN growth rates at high growth temperatures using a solid Ga target. The magnetron is tested with a wide range of process parameters and a stable process is feasible while maintaining the solid state of the Ga target. High GaN growth rates of up to 5 mu m/h are achieved at room temperature and a growth rate of 4 mu m/h at high temperature, which is one order of magnitude higher compared to MSE with a liquid target. We grow GaN on c-plane sapphire substrates and show the impact of partial pressure ratio and target-to-substrate distance (TSD) on growth rate, film morphology and crystal quality of GaN films with scanning electron microscopy and X-ray diffraction. While the growth rate and film morphology are strongly impacted by the process parameter variation, the crystal quality is further impacted by the overall film thickness. For a 2 mu m thick GaN film a full width at half maximum of X-ray rocking curve (omega-FWHM) of GaN 10 1 1 reflection of 0.32 degrees is achieved. We demonstrate a process window for growth of dense and smooth GaN films with high crystal quality using low N2 flow rates and high TSD. By introducing a 20 nm AlN nucleation layer prior to the growth of 390 nm GaN, the omega-FWHM of GaN 0002 reflection of 0.19 degrees is achieved. The epitaxially grown crystalline structure is precisely examined by transmission electron microscopy.
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| 5. |
- Smazna, Daria, et al.
(författare)
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Buckminsterfullerene hybridized zinc oxide tetrapods : defects and charge transfer induced optical and electrical response
- 2018
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 10:21, s. 10050-10062
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Tidskriftsartikel (refereegranskat)abstract
- Buckminster fullerene (C-60) based hybrid metal oxide materials are receiving considerable attention because of their excellent fundamental and applied aspects, like semiconducting, electron transfer, luminescent behaviors, etc. and this work briefly discusses the successful fabrication of C-60 decorated ZnO tetrapod materials and their detailed structure-property relationships including device sensing applications. The electron microscopy investigations indicate that a quite dense surface coverage of ZnO tetrapods with C-60 clusters is achieved. The spectroscopy studies confirmed the identification of the C-60 vibrational modes and the C-60 induced changes in the absorption and luminescence properties of the ZnO tetrapods. An increased C-60 concentration on ZnO results in steeper ZnO bandgap absorption followed by well-defined free exciton and 3.31 eV line emissions. As expected, higher amounts of C-60 increase the intensity of C-60-related visible absorption bands. Pumping the samples with photons with an energy corresponding to these absorption band maxima leads to additional emission from ZnO showing an effective charge transfer phenomenon from C-60 to the ZnO host. The density of states model obtained from DFT studies for pure and C-60 coated ZnO surfaces confirms the experimental observations. The fabricated C-60-ZnO hybrid tetrapod based micro- and nanodevices showed interesting ethanol gas sensing characteristics.
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| 6. |
- Tomer, Vijay K., et al.
(författare)
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Superior visible light photocatalysis and low-operating temperature VOCs sensor using cubic Ag(0)-MoS2 loaded g-CN 3D porous hybrid
- 2019
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Ingår i: APPLIED MATERIALS TODAY. - : ELSEVIER. - 2352-9407. ; 16, s. 193-203
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional materials are incipient as an innovative class of multifunctional elements with promising attributes for energy and environmental applications. Herein, a novel nanohybrid consisting of Ag-MoS2 loaded mesoporous g-C3N4 (herein 'm-CN') with ordered structure was synthesized by a nanocasting method using cubic and ordered mesoporous silica (KIT-6) as a hard template. Due to its unique 3D mesoporous architecture, the as-synthesized Ag-MoS2 @m-CN nanohybrid revealed excellent visible-light absorption for enhanced charge separation of photo-induced e(-)-h(+) pairs to improve the degradation performance, high stability, and reusability with respect to Rhodamine B (RhB). The measured very high degradation efficiency is explained by synergistic effects from catalytically active Ag and MoS2 nanoparticles cumulatively decorated on the cubic mesoporous m-CN in form 3D mesoporous architecture. Additionally, the Ag-MoS2@m-CN nanohybrid exhibits high response and selectivity toward n-butanol gas at low-operating temperatures for reliable detection of volatile organic compounds (VOCs). The photocatalysis behavior and VOC sensing response of Ag-MoS2@m-CN nanohybrid material are discussed in detail for possible various application avenues toward environmental purifications and monitoring. (C) 2019 Elsevier Ltd. All rights reserved.
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| 7. |
- von Langermann, Jan, et al.
(författare)
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Design of an Integrated Process of Chromatography, Crystallization and Racemization for the Resolution of 2 ',6 '-Pipecoloxylidide (PPX)
- 2012
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Ingår i: Organic Process Research & Development. - : American Chemical Society (ACS). - 1083-6160 .- 1520-586X. ; 16:2, s. 343-352
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Tidskriftsartikel (refereegranskat)abstract
- An integrated process for the chiral separation of the industrially relevant substance 2',6'-pipecoloxylidide (PPX), an intermediate in the manufacture of a number of anesthetics, was developed. By combining three different techniques, chromatography, crystallization, and racemization, high productivity was achieved. All unit operations were executed using a common solvent system, full recycling, and a minimum of solvent exchanges or removals. The target molecule was obtained with an enantiopurity of >99.5 wt %.
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| 8. |
- Zeilinger, Michael, et al.
(författare)
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Alkali Metals Extraction Reactions with the Silicides Li15Si4 and Li3NaSi6 : Amorphous Si versus allo-Si
- 2014
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 26:22, s. 6603-6612
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Tidskriftsartikel (refereegranskat)abstract
- The silicides Li15Si4 and Li3NaSi6 were subjected to chemical extraction of the alkali metal component by liquid ammonia and ethanol, respectively, which after washing yielded black powders of amorphous silicon. The investigated reactions are interesting with respect to both the formation of novel Si modifications and the delithiation process in Si anode materials. The products termed a-Si (from Li15Si4) and a-allo-Si (from Li3NaSi6) were characterized by a combination of methodologies (X-ray diffraction, transmission electron microscopy, differential thermal analysis, Raman, atomic absorption, and energy-dispersive X-ray spectroscopy) which revealed (i) a porous microstructure for a-Si built from spherically shaped particles with sizes around 10 nm, (ii) partial surface oxidation of both materials and (iii) the presence of nanocrystalline Si in both materials. The result of the protic oxidation of Li3NaSi6 is at variance with earlier findings reporting the formation of a crystalline bulk allotrope of silicon (allo-Si) from the topotactic combination of silicon layers present as polyanions in Li3NaSi6. Additionally, quantum chemical calculations show that silicon layers in Li3NaSi6 cannot combine to energetically favorable allotropic forms of Si. This is different from Li7Ge12, where polyanionic germanium layers topotactically convert to the germanium allotrope m-allo-Ge upon oxidation.
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