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Sökning: WFRF:(Messing Maria) > Tidskriftsartikel

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1.
  • Hamed, Tareq Abu, et al. (författare)
  • Multiscale in modelling and validation for solar photovoltaics
  • 2018
  • Ingår i: EPJ Photovoltaics. - : EDP Sciences. - 2105-0716. ; 9
  • Tidskriftsartikel (refereegranskat)abstract
    • Photovoltaics is amongst the most important technologies for renewable energy sources, and plays a key role in the development of a society with a smaller environmental footprint. Key parameters for solar cells are their energy conversion efficiency, their operating lifetime, and the cost of the energy obtained from a photovoltaic system compared to other sources. The optimization of these aspects involves the exploitation of new materials and development of novel solar cell concepts and designs. Both theoretical modeling and characterization of such devices require a comprehensive view including all scales from the atomic to the macroscopic and industrial scale. The different length scales of the electronic and optical degrees of freedoms specifically lead to an intrinsic need for multiscale simulation, which is accentuated in many advanced photovoltaics concepts including nanostructured regions. Therefore, multiscale modeling has found particular interest in the photovoltaics community, as a tool to advance the field beyond its current limits. In this article, we review the field of multiscale techniques applied to photovoltaics, and we discuss opportunities and remaining challenges.
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2.
  • Elmroth Nordlander, Jonas, et al. (författare)
  • Mo3Ni2N Nanoparticle Generation by Spark Discharge
  • 2023
  • Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 16:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Spark ablation is an advantageous method for the generation of metallic nanoparticles with defined particle sizes and compositions. The reaction of the metal particles with the carrier gas during the synthesis and, therefore, the incorporation of those light elements into structural voids or even compound formation was confirmed for hydrides and oxides but has only been suspected to occur for nitrides. In this study, dispersed nanoparticles of Mo3Ni2N and Mo with Janus morphology, and defined particle sizes were obtained by spark discharge generation as a result of carrier gas ionization and characterized using transmission electron microscopy and powder X-ray diffraction. Metal nitrides possess beneficial catalytic and thermoelectric properties, as well as high hardness and wear resistance. Therefore, this method offers the possibility of controlled synthesis of materials which are interesting for numerous applications.
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3.
  • Franzén, Sara, et al. (författare)
  • Compositional tuning of gas-phase synthesized Pd–Cu nanoparticles
  • 2023
  • Ingår i: Nanoscale Advances. - 2516-0230. ; 5:22, s. 6069-6077
  • Tidskriftsartikel (refereegranskat)abstract
    • Bimetallic nanoparticles have gained significant attention in catalysis as potential alternatives to expensive catalysts based on noble metals. In this study, we investigate the compositional tuning of Pd–Cu bimetallic nanoparticles using a physical synthesis method called spark ablation. By utilizing pure and alloyed electrodes in different configurations, we demonstrate the ability to tailor the chemical composition of nanoparticles within the range of approximately 80 : 20 at% to 40 : 60 at% (Pd : Cu), measured using X-ray fluorescence (XRF) and transmission electron microscopy energy dispersive X-ray spectroscopy (TEM-EDXS). Time-resolved XRF measurements revealed a shift in composition throughout the ablation process, potentially influenced by material transfer between electrodes. Powder X-ray diffraction confirmed the predominantly fcc phase of the nanoparticles while high-resolution TEM and scanning TEM-EDXS confirmed the mixing of Pd and Cu within individual nanoparticles. X-ray photoelectron and absorption spectroscopy were used to analyze the outermost atomic layers of the nanoparticles, which is highly important for catalytic applications. Such comprehensive analyses offer insights into the formation and structure of bimetallic nanoparticles and pave the way for the development of efficient and affordable catalysts for various applications.
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4.
  • Gericke, Sabrina Maria, et al. (författare)
  • In Situ H2 Reduction of Al2O3-Supported Ni- and Mo-Based Catalysts
  • 2022
  • Ingår i: Catalysts. - : MDPI. - 2073-4344. ; 12:7
  • Tidskriftsartikel (refereegranskat)abstract
    • Nickel (Ni)-promoted Molybdenum (Mo)-based catalysts are used for hydrotreatment processes in the chemical industry where the catalysts are exposed to high-pressure H2 at elevated temperature. In this environment, the catalyst transforms into the active phase, which involves the reduction of the oxide. Here, we report on the first in situ study on the reduction of alumina supported Ni- and Mo-based catalysts in 1 mbar H2 using ambient-pressure X-ray photoelectron spectroscopy (APXPS). The study confirms that mixing Ni and Mo lowers the reduction temperature of both Ni- and Mo-oxide as compared to the monometallic catalysts and shows that the MoO3 reduction starts at a lower temperature than the reduction of NiO in NiMo/Al2O3 catalysts. Additionally, the reduction of Ni and Mo foil was directly compared to the reduction of the Al2O3-supported catalysts and it was observed that the reduction of the supported catalysts is more gradual than the reduction of the foils, indicating a strong interaction between the Ni/Mo and the alumina support. © 2022 by the authors.
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6.
  • Hedmer, Maria, et al. (författare)
  • Exposure and Emission Measurements During Production, Purification, and Functionalization of Arc-Discharge-Produced Multi-walled Carbon Nanotubes.
  • 2014
  • Ingår i: Annals of Occupational Hygiene. - : Oxford University Press (OUP). - 1475-3162. ; 58:3, s. 355-379
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: The production and use of carbon nanotubes (CNTs) is rapidly growing. With increased production, there is potential that the number of occupational exposed workers will rapidly increase. Toxicological studies on rats have shown effects in the lungs, e.g. inflammation, granuloma formation, and fibrosis after repeated inhalation exposure to some forms of multi-walled CNTs (MWCNTs). Still, when it comes to health effects, it is unknown which dose metric is most relevant. Limited exposure data for CNTs exist today and no legally enforced occupational exposure limits are yet established. The aim of this work was to quantify the occupational exposures and emissions during arc discharge production, purification, and functionalization of MWCNTs. The CNT material handled typically had a mean length <5 μm. Since most of the collected airborne CNTs did not fulfil the World Health Organization fibre dimensions (79% of the counted CNT-containing particles) and since no microscopy-based method for counting of CNTs exists, we decided to count all particle that contained CNTs. To investigate correlations between the used exposure metrics, Pearson correlation coefficient was used.
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7.
  • Hedmer, Maria, et al. (författare)
  • Real-Time Emission and Exposure Measurements of Multi-walled Carbon Nanotubes during Production, Power Sawing, and Testing of Epoxy-Based Nanocomposites
  • 2022
  • Ingår i: Annals of Work Exposures and Health. - : Oxford University Press (OUP). - 2398-7308 .- 2398-7316. ; 66:7, s. 878-894
  • Tidskriftsartikel (refereegranskat)abstract
    • The use of manufactured nanomaterials is increasing globally. Although multi-walled carbon nanotubes (CNTs) are used in a wide range of applications, only limited data are available on emissions and exposures during CNT composite production. No exposure data using portable aethalometers in the personal breathing zone (PBZ) to monitor occupational exposure to CNTs have yet been published. The aim of this study was to characterize emissions of and exposures to CNTs during CNT composite production, sawing, and shear testing. We also investigated whether real-time aethalometer measurements of equivalent black carbon (eBC) could be used as a proxy filter sampling of elemental carbon (EC). The presence of CNTs as surface contamination in the production facility was monitored since this could contribute to airborne exposure.Methods: During CNT composite production in an industrial setting including both chemical and manufacturing laboratories, different work tasks (WTs) were studied with a combination of directreading instruments (aethalometer, aerodynamic particle sizer, condensation particle counter) and filter-based methods. Measurements were performed to monitor concentrations in the emission zone (EZ), PBZ, and background zone. The filter samples were analysed for EC and fibre concentration of CNTs using scanning electron microscopy (SEM). Additionally, surfaces in the facility were tape sampled for monitoring of CNT contamination, and analysed with SEM.Results: Clear eBC peaks were observed in the PBZ during several WTs, most clearly during open handling of CNT powder. Power sawing emitted the highest particle number concentration in the EZ of both nanoparticles and coarse particles, but no individual airborne CNTs, agglomerates, or aggregates were detected. Airborne CNTs were identified, for example, in a filter sample collected in the PBZ of a worker during mixing of CNT epoxy. The airborne CNT particles were large agglomerates which looked like porous balls in the SEM images. Significant EC exposures were found in the inhalable fraction while all respirable fractions of EC were below detection. The highest inhalable EC concentrations were detected during the composite production. No significant correlation was found between inhalable EC and eBC, most likely due to losses of large EC containing particles in the sampling lines and inside the eBC monitor. In total, 39 tape samples were collected. Surface contamination of CNTs was detected on eight surfaces in the chemical and manufacturing laboratories, mainly in the near-field zone. Elongated CNT-like features were detected in the sawdust after sawing of CNT composite.Conclusions: Characterization of a workplace producing CNT composite showed that open handling of the CNT powder during weighing and mixing of CNT powder material generated the highest particle emissions and exposures. The portable direct-reading aethalometer provided time-resolved eBC exposure data with complementary information to time-integrated EC filter samples by linking peak exposures to specific WTs. Based on the results it was not possible to conclude that eBC is a good proxy of EC. Surface contamination of CNTs was detected on several surfaces in the near-field zone in the facility. This contamination could potentially be resuspended into the workplace air, and may cause secondary inhalation exposure.
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8.
  • Isaxon, Christina, et al. (författare)
  • Workplace Emissions and Exposures During Semiconductor Nanowire Production, Post-production, and Maintenance Work
  • 2020
  • Ingår i: Annals of Work Exposures and Health. - : Oxford University Press (OUP). - 2398-7308 .- 2398-7316. ; 64:1, s. 38-54
  • Tidskriftsartikel (refereegranskat)abstract
    • BackgroundNanowires are a high-aspect-ratio material of increasing interest for a wide range of applications. A new and promising method to produce nanowires is by aerotaxy, where the wires are grown in a continuous stream of gas. The aerotaxy method can grow nanowires much faster than by more conventional methods. Nanowires have important properties in common with asbestos fibers, which indicate that there can be potential health effects if exposure occurs. No conclusive exposure (or emission) data from aerotaxy-production of nanowires has so far been published.MethodsDifferent work tasks during semiconductor nanowire production, post-production, and maintenance were studied. A combination of direct-reading instruments for number concentration (0.007–20 µm) and filter sampling was used to assess the emissions (a couple of centimeter from the emission sources), the exposure in the personal breathing zone (max 30 cm from nose–mouth), and the concentrations in the background zone (at least 3 m from any emission source). The filters were analyzed for metal dust composition and number concentration of nanowires. Various surfaces were sampled for nanowire contamination.ResultsThe particle concentrations in the emission zone (measured with direct-reading instruments) were elevated during cleaning of arc discharge, manual reactor cleaning, exchange of nanowire outflow filters, and sonication of substrates with nanowires. In the case of cleaning of the arc discharge and manual reactor cleaning, the emissions affected the concentrations in the personal breathing zone and were high enough to also affect the concentrations in the background. Filter analysis with electron microscopy could confirm the presence of nanowires in some of the air samples.ConclusionsOur results show that a major part of the potential for exposure occurs not during the actual manufacturing, but during the cleaning and maintenance procedures. The exposures and emissions were evaluated pre- and post-upscaling the production and showed that some work tasks (e.g. exchange of nanowire outflow filters and sonication of substrates with nanowires) increased the emissions post-upscaling.
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9.
  • Lovén, Karin, et al. (författare)
  • Emissions and exposures of graphene nanomaterials, titanium dioxide nanofibers, and nanoparticles during down-stream industrial handling
  • 2021
  • Ingår i: Journal of Exposure Science & Environmental Epidemiology. - : Springer Science and Business Media LLC. - 1559-064X .- 1559-0631. ; 31:4, s. 736-752
  • Tidskriftsartikel (refereegranskat)abstract
    • Today, engineered nanomaterials are frequently used. Nanosized titanium dioxide (TiO2) has been extensively used for many years and graphene is one type of emerging nanomaterial. Occupational airborne exposures to engineered nanomaterials are important to ensure safe workplaces and to extend the information needed for complete risk assessments. The main aim of this study was to characterize workplace emissions and exposure of graphene nanoplatelets, graphene oxide, TiO2 nanofibers (NFs) and nanoparticles (NPs) during down-stream industrial handling. Surface contaminations were also investigated to assess the potential for secondary inhalation exposures. In addition, a range of different sampling and aerosol monitoring methods were used and evaluated. The results showed that powder handling, regardless of handling graphene nanoplatelets, graphene oxide, TiO2 NFs, or NPs, contributes to the highest particle emissions and exposures. However, the exposure levels were below suggested occupational exposure limits. It was also shown that a range of different methods can be used to selectively detect and quantify nanomaterials both in the air and as surface contaminations. However, to be able to make an accurate determination of which nanomaterial that has been emitted a combination of different methods, both offline and online, must be used.
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10.
  • Lovén, Karin, et al. (författare)
  • Size-resolved characterization of particles >10 nm emitted to air during metal recycling
  • 2023
  • Ingår i: Environment International. - : Elsevier Ltd. - 0160-4120 .- 1873-6750. ; 174
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: In the strive towards a circular economy, metal waste recycling is a growing industry. During the recycling process, particulate matter containing toxic and allergenic metals will be emitted to the air causing unintentional exposure to humans and environment. Objective: In this study detailed characterization of particle emissions and workplace exposures were performed, covering the full size range from 10 nm to 10 µm, during recycling of three different material flows: Waste of electrical and electronic equipment (WEEE), metal scrap, and cables. Methods: Both direct-reading instruments (minute resolution), and time-integrated filter measurements for gravimetric and chemical analysis were used. Additionally, optical sensors were applied and evaluated for long-term online monitoring of air quality in industrial settings. Results: The highest concentrations, in all particle sizes, and with respect both to particle mass and number, were measured in the WEEE flow, followed by the metal scrap flow. The number fraction of nanoparticles was high for all material flows (0.66–0.86). The most abundant metals were Fe, Al, Zn, Pb and Cu. Other elements of toxicological interest were Mn, Ba and Co. Significance: The large fraction of nanoparticles, and the fact that their chemical composition deviate from that of the coarse particles, raises questions that needs to be further addressed including toxicological implications, both for humans and for the environment. © 2023 The Authors
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