| 1. |
- Kanerva, Tomi, et al.
(författare)
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Microstructural characteristics of vehicle-aged heavy-duty diesel oxidation catalyst and natural gas three-way catalyst
- 2019
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Ingår i: Catalysts. - : MDPI AG. - 2073-4344. ; 9:2
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Tidskriftsartikel (refereegranskat)abstract
- Techniques to control vehicle engine emissions have been under increasing need for development during the last few years in the more and more strictly regulated society. In this study, vehicle-aged heavy-duty catalysts from diesel and natural gas engines were analyzed using a cross-sectional electron microscopy method with both a scanning electron microscope and a transmission electron microscope. Also, additional supporting characterization methods including X-ray diffractometry, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy and catalytic performance analyses were used to reveal the ageing effects. Structural and elemental investigations were performed on these samples, and the effect of real-life ageing of the catalyst was studied in comparison with fresh catalyst samples. In the real-life use of two different catalysts, the poison penetration varied greatly depending on the engine and fuel at hand: the diesel oxidation catalyst appeared to suffer more thorough changes than the natural gas catalyst, which was affected only in the inlet part of the catalyst. The most common poison, sulphur, in the diesel oxidation catalyst was connected to cerium-rich areas. On the other hand, the severities of the ageing effects were more pronounced in the natural gas catalyst, with heavy structural changes in the washcoat and high concentrations of poisons, mainly zinc, phosphorus and silicon, on the surface of the inlet part.
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| 2. |
- Koivikko, Niina, et al.
(författare)
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Activity and in situ DRIFT studies on vanadia catalysts during oxidative dehydrogenation of sulfur-contaminated methanol
- 2022
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Ingår i: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373. ; 318
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Tidskriftsartikel (refereegranskat)abstract
- Silica-titania (70/30) supported vanadium catalysts were prepared, characterized, and studied in oxidative dehydrogenation of sulfur-contaminated methanol. The quality of vanadia species is dependent on temperature and gas conditions during preparation, support type, support specific surface area and VOx surface density. For example, upon heating the amount of V2O5 decrease along with formation of polymeric species. Such changes may occur also during the catalytic reaction. The reaction experiments and characterization results showed that the stability of polymeric vanadia species and total acidity has a connection with better formaldehyde production performance. The best performance was observed for N2-calcined silica-titania catalyst. Easy reducibility of the catalyst, as in the case of reference catalysts, leads to further oxidation of formaldehyde.
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| 3. |
- Mohl, Melinda, et al.
(författare)
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Titania nanofibers in gypsum composites : an antibacterial and cytotoxicology study
- 2014
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Ingår i: Journal of Material Chemistry B. - : Royal Society of Chemistry. - 2050-750X .- 2050-7518. ; 2:10, s. 1307-1316
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Tidskriftsartikel (refereegranskat)abstract
- Further developments of antibacterial coatings based on photocatalytic nanomaterials could be a promising route towards potential environmentally friendly applications in households, public buildings and health care facilities. Hereby we describe a simple chemical approach to synthesize photocatalytic nanomaterial-embedded coatings using gypsum as a binder. Various types of TiO2 nanofiber-based photocatalytic materials (nitrogen-doped and/or palladium nanoparticle decorated) and their composites with gypsum were characterized by means of scanning (SEM) and transmission (TEM) electron microscopy as well as electron and X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX) techniques. These gypsum-based composites can be directly applied as commercially available paints on indoor walls. Herein we report that surfaces coated with photocatalytic composites exhibit excellent antimicrobial properties by killing both methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) under blue light. In the case of MSSA cells, the palladium nanoparticle-decorated and nitrogen-doped TiO2 composites demonstrated the highest antimicrobial activity. For the MRSA strain even pure gypsum samples were proven to be efficient in eradicating Gram-positive human pathogens. The cytotoxicity of freestanding TiO2 nanofibers was revealed by analyzing the viability of HeLa cells using MTT and fluorescent cell assays.
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| 4. |
- Wu, Ming-Chung, et al.
(författare)
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Photocatalytic activity of nitrogen-doped TiO2-based nanowires : a photo-assisted Kelvin probe force microscopy study
- 2013
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Ingår i: Journal of nanoparticle research. - : Springer. - 1388-0764 .- 1572-896X. ; 16:1, s. Article Number: UNSP 2143-
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a set of nitrogen-doped TiO2-based nanomaterials demonstrating photocatalytic activity was developed by combining the efforts of lattice doping and metal nanoparticle decoration and tested for photo-degradation of methylene blue dye by applying solar simulator irradiation. The surface potential shifts of these TiO2-based photocatalytic nanomaterials measured by Kelvin probe force microscope have been used to study the degree of electron generation of the photocatalysts after irradiation and were well correlated with the photocatalytic activity. The nitrogen-doped TiO2 nanowires decorated with Pt nanoparticles can induce obvious electron accumulation and result in a large shift of surface potential. The analysis shows a clear correlation between the surface potential shift and the photodegradation activity. Furthermore, a thorough comparative photocatalytic activity study combined with X-ray photoelectron spectroscopy analysis of the materials-doped with nitrogen under various conditions-reveals that the photocatalytic efficiency of the catalysts is maintained even if the lattice doping is leached e.g., by thermal treatments after doping. By monitoring the surface potential shifts of various TiO2-based photocatalysts by photo-assisted Kelvin probe force microscopy, we obtain a useful tool for developing novel materials with high photocatalytic activity.
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