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| 3. |
- Ludvigsson, Linus, et al.
(författare)
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Investigations of initial particle stages during spark discharge
- 2015
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Ingår i: Journal of Physics D: Applied Physics. - : IOP Publishing. - 1361-6463 .- 0022-3727. ; 48:31
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Tidskriftsartikel (refereegranskat)abstract
- The number of nanoparticle-based products on the market is expected to increase considerably during the coming decades. This forces the industry to have highly meticulous manufacturing of large amounts of nanoparticles using cheap and environmentally friendly methods. For the production of metal nanoparticles spark discharge generation is a promising route to fulfill these demands. The spark discharge generator can be easily scaled-up for mass production due to its simple design solely by placing several units in parallel. Before doing so, one first needs to optimize a single spark discharge generator unit. To optimize the spark discharge generator in a controlled way the first stage of nanoparticle formation needs to be understood. To improve this understanding we have constructed a customized nanoparticle sampler to enable sampling of the initial stages of particle formation for imaging in a TEM. In this article we present the design of the sampler and discuss optimal sampling parameters. We also present how the generation parameters can be tuned in order to affect the first stages of particle formation and hence the final nanoparticles.
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| 4. |
- McKibbin, Sarah R., et al.
(författare)
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In situ observation of synthesized nanoparticles in ultra-dilute aerosols via X-ray scattering
- 2019
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Ingår i: Nano Research. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 12:1, s. 25-31
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Tidskriftsartikel (refereegranskat)abstract
- In-air epitaxy of nanostructures (Aerotaxy) has recently emerged as a viable route for fast, large-scale production. In this study, we use small-angle X-ray scattering to perform direct in-flight characterizations of the first step of this process, i.e., the engineered formation of Au and Pt aerosol nanoparticles by spark generation in a flow of N2 gas. This represents a particular challenge for characterization because the particle density can be extremely low in controlled production. The particles produced are examined during production at operational pressures close to atmospheric conditions and exhibit a lognormal size distribution ranging from 5–100 nm. The Au and Pt particle production and detection are compared. We observe and characterize the nanoparticles at different stages of synthesis and extract the corresponding dominant physical properties, including the average particle diameter and sphericity, as influenced by particle sintering and the presence of aggregates. We observe highly sorted and sintered spherical Au nanoparticles at ultra-dilute concentrations (< 5 × 105 particles/cm3) corresponding to a volume fraction below 3 × 10–10, which is orders of magnitude below that of previously measured aerosols. We independently confirm an average particle radius of 25 nm via Guinier and Kratky plot analysis. Our study indicates that with high-intensity synchrotron beams and careful consideration of background removal, size and shape information can be obtained for extremely low particle concentrations with industrially relevant narrow size distributions. [Figure not available: see fulltext.].
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| 7. |
- Messing, Maria, et al.
(författare)
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Gas-borne particles with tunable and highly controlled characteristics.
- 2013
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Ingår i: Nanotoxicology. - : Informa UK Limited. - 1743-5404 .- 1743-5390. ; 7:6, s. 1052-1063
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Tidskriftsartikel (refereegranskat)abstract
- Abstract For nanotoxicology investigations of air-borne particles to provide relevant results it is ever so important that the particle exposure of, for example cells, closely resembles the "real" exposure situation, that the dosimetry is well defined, and that the characteristics of the deposited nanoparticles are known in detail. By synthesizing the particles in the gas-phase and directly depositing them on lung cells the particle deposition conditions in the lung is closely mimicked. In this work we present a setup for generation of gas-borne nanoparticles of a variety of different materials with highly controlled and tunable particle characteristics, and demonstrate the method by generation of gold particles. Particle size, number concentration and mass of individual particles of the population are measured on-line by means of differential mobility analyzers (DMA) and an aerosol particle mass analyzer (APM) whereas primary particle size and internal structure are investigated by transmission electron microscopy. A method for 3 estimating the surface area dose from the DMA-APM measurements is applied and we further demonstrate that for the setup used, a deposition time of around 1 hour is needed for deposition onto cells in an air liquid interface chamber, using electrostatic deposition, to reach a toxicological relevant surface area dose.
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| 8. |
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| 9. |
- Messing, Maria, et al.
(författare)
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Generation of Pd Model Catalyst Nanoparticles by Spark Discharge
- 2010
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:20, s. 9257-9263
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Tidskriftsartikel (refereegranskat)abstract
- We present a method to deposit Pd nanoparticles with a very small size distribution by an aerosol process onto oxide substrates for the creation of model systems in catalytic research. The Pd nanoparticles are characterized by transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. We confirm the small size dispersion from the desired particle size, and we show that the particle surface coverage can he highly controlled. Further, our measurements indicate that an amorphous shell surrounding a crystalline core of the Pd particles may form during the particle synthesis and that the shell contains carbon.
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| 11. |
- Messing, Maria, et al.
(författare)
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Iron-based magnetic nanoparticles by spark ablation
- 2019
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Konferensbidrag (refereegranskat)abstract
- Magnetic nanoparticles have shown great potential for use in drug delivery and bioimaging applications and are prospective building blocks in future high-performing permanent magnets. Today, magnetic nanoparticles are most often produced in batches by chemical methods resulting in the risk of chemical impurities and production of vast amounts of chemical waste. Aerosol generation methods on the other hand, particularly spark ablation, are promising for future generation of magnetic nanoparticles since they are simple, fast, continuous, scalable, provide good control of size and composition, and offer the possibility to form alloys of material combinations not miscible on the macroscopic scale. High controllability is of utmost importance when generating magnetic nanoparticles since small deviations in size can significantly alter the magnetic coercivity. Also, the composition of the particles is of high significance since the magnetic properties can be completely transformed by changes in elemental composition or the oxidation state of the particle.In this work, we present the successful generation of monodisperse bimetallic FeCr and FeMn nanoparticles by spark ablation, and the results from the thorough characterization of individual particles with aerosol instruments, transmission electron microscopy, and synchrotron-based X-ray photoelectron spectroscopy. We demonstrate how the carrier gas can be used to dictate the oxidation and how to alternate between self-passivated and completely oxidized nanoparticles. We also show how the produced particles can be deposited to yield a low surface concentration which is critical for minimizing interparticle interactions during magnetic measurements. Finally, as a proof of concept, measurements using a magnetometer equipped with a SQUID on samples with different particle coverages are presented.
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| 12. |
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| 13. |
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| 14. |
- Meuller, Bengt, et al.
(författare)
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Review of Spark Discharge Generators for Production of Nanoparticle Aerosols
- 2012
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Ingår i: Aerosol Science and Technology. - : Informa UK Limited. - 1521-7388 .- 0278-6826. ; 46:11, s. 1256-1270
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Forskningsöversikt (refereegranskat)abstract
- In the growing field of nanotechnology there is an increasing need to develop production methods for nanoparticles, especially methods that provide control and reproducibility. The spark discharge generator (SDG) is a versatile device for the production of nanoparticle aerosols. It can produce aerosol nanoparticles in the entire nanometer range (1-100 nm), and beyond. Depending on requirements, and the system used, these nanoparticles can be completely contamination free and composed of one or more materials. This provides a unique opportunity to create new materials on the nanoscale. Already in use in semiconductor, materials, health and environmental research, the SDG shows promise for yet more applications. If needed, particle production by the SDG could be scaled up using parallel generators facilitating continuous high-volume production of aerosol nanoparticles. Still, there is a surprisingly low knowledge of fundamental processes in the SDG. In this article we present a thorough review of the most common and relevant SDGs and the theory of their operation. Some possible improvements are also discussed.
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| 15. |
- Nilsson, Patrik, et al.
(författare)
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In-situ characterization of metal nanoparticles and their organic coatings using laser-vaporization aerosol mass spectrometry
- 2015
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Ingår i: Nano Reseach. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 8:12, s. 3780-3795
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Tidskriftsartikel (refereegranskat)abstract
- The development of methods to produce nanoparticles with unique properties via the aerosol route is progressing rapidly. Typical characterization techniques extract particles from the synthesis process for subsequent offline analysis, which may alter the particle characteristics. In this work, we use laser-vaporization aerosol mass spectrometry (LV-AMS) with 70-eV electron ionization for real-time, in-situ nanoparticle characterization. The particle characteristics are examined for various aerosol synthesis methods, degrees of sintering, and for controlled condensation of organic material to simulate surface coating/functionalization. The LV-AMS is used to characterize several types of metal nanoparticles (Ag, Au, Pd, PdAg, Fe, Ni, and Cu). The degree of oxidation of the Fe and Ni nanoparticles is found to increase with increased sintering temperature, while the surface organic-impurity content of the metal particles decreases with increased sintering temperature. For aggregate metal particles, the organic-impurity content is found to be similar to that of a monolayer. By comparing different equivalent-diameter measurements, we demonstrate that the LV-AMS can be used in tandem with a differential mobility analyzer to determine the compactness of synthesized metal particles, both during sintering and during material addition for surface functionalization. Further, materials supplied to the particle production line downstream of the particle generators are found to reach the generators as contaminants. The capacity for such in-situ observations is important, as it facilitates rapid response to undesired behavior within the particle production process. This study demonstrates the utility of real-time, in-situ aerosol mass spectrometric measurements to characterize metal nanoparticles obtained directly from the synthesis process line, including their chemical composition, shape, and contamination, providing the potential for effective optimization of process operating parameters.
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| 16. |
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| 17. |
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| 18. |
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| 19. |
- Preger, Calle, et al.
(författare)
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Controlled Oxidation and Self-Passivation of Bimetallic Magnetic FeCr and FeMn Aerosol Nanoparticles
- 2019
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 123:26, s. 16083-16090
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Tidskriftsartikel (refereegranskat)abstract
- Nanoparticle generation by aerosol methods, particularly spark ablation, has high potential for creating new material combinations with tailored magnetic properties. By combining elements into complex alloyed nanoparticles and controlling their size and structure, different magnetic properties can be obtained. In combination with controlled deposition, to ensure nanoparticle separation, it is possible to minimize interparticle interactions and measure the intrinsic magnetic property of the nanoparticles. Most magnetic materials are highly sensitive to oxygen, and it is therefore crucial to both understand and control the oxidation of magnetic nanoparticles. In this study, we have successfully generated oxidized, bimetallic FeCr and FeMn nanoparticles by spark ablation in combination with a compaction step and thoroughly characterized individual particles with aerosol instruments, transmission electron microscopy and synchrotron-based X-ray photoelectron spectroscopy. The generated nanoparticles had an almost identical transition-metal ratio to the electrodes used as seed materials. Further, we demonstrate how the carrier gas can be used to dictate the oxidation and how to alternate between self-passivated and entirely oxidized nanoparticles. We also discuss the complexity of compacting alloyed nanoparticles consisting of elements with different vapor pressures and how this will affect the composition. This knowledge will further the understanding of design and generation of complex alloyed nanoparticles based on transition metals using aerosol methods, especially for the size regime where a compaction step is needed. As a proof of concept, measurements using a magnetometer equipped with a superconducting quantum interference device were performed on samples with different particle coverages. These measurements show that the magnetic properties could be explored for both high and low surface coverages, which open a way for studies where interparticle interactions can be systematically controlled.
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| 20. |
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| 21. |
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| 22. |
- Svensson, Christian, et al.
(författare)
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Characteristics of airborne gold aggregates generated by spark discharge and high temperature evaporation furnace: Mass-mobility relationship and surface area
- 2015
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 87, s. 38-52
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Tidskriftsartikel (refereegranskat)abstract
- The properties of gas-borne aggregates are important in nano-technology and for potential health effects. Gold aggregates from three generators (one commercial and one custom built spark discharge generator and one high-temperature furnace) have been characterized. The aggregate surface areas were determined using five approaches - based on aggregation theory and/or measured aggregate properties. The characterization included mass-mobility relationships, effective densities (assessed by an Aerosol Particles Mass analyzer), primary particle analysis (based on Transmission Electron Microscopy), as well as total mass and number concentration outputs. The relationships between mass and mobility are well described by power-law functions with exponents of 2.18-2.35. For all generators, the primary particles of the aggregates were fused together by a bridge with a diameter typically similar to 60-70% of the primary particle diameter (5-10 nm). The total mass outputs were 6.1-48.1 mg/m3 and the predicted surface area outputs in the range 0.9 x 10(-3)-17 x 10(-3) cm(2)/cm(3). The aggregate effective densities differed considerably between generators. The difference could partly be explained by the differences in primary particle diameter, but not fully. This in turn may be explained either by a varying primary particle size with aggregate size, or by that there are slight differences in the morphology of the aggregates from the generators. (C) 2015 The Authors. Published by Elsevier Ltd.
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| 26. |
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| 27. |
- Ternero, Pau, et al.
(författare)
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Effect of the carrier gas on the structure and composition of Co–Ni bimetallic nanoparticles generated by spark ablation
- 2023
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 170
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Tidskriftsartikel (refereegranskat)abstract
- Spark ablation is a versatile technique for producing pure size-selected nanoparticles. The carrier gas used in spark ablation affects the nanoparticles’ generation, crystalline structure, and chemical composition. The comprehension of this phenomenon can contribute to the design of nanoparticles with tailored properties. In this paper, we evaluate the effects of reducing (95%N2 + 5%H2), inert (N2), and oxidative (air) carrier gases in a spark ablation setup with Co–Ni alloyed electrodes. The agglomerates’ particle size distribution, morphology, structure, and composition were highly dependent on the carrier gas, especially its relative oxygen content. The agglomerates were then sintered into compacted particles. Three different crystalline structures and chemical compositions were observed with X-ray diffraction and confirmed with transmission electron microscopy for the compacted particles. For 95%N2 + 5%H2 and air, single-phase (Co,Ni) and (Co,Ni)O particles were identified, respectively, whereas for N2, two-phase (Co,Ni) and (Co,Ni)O particles were obtained. This work opens up new possibilities of tuning the structure and composition, i.e., distribution of metallic and oxide phases, of the produced particles and thus tailor their properties for specific applications by simply changing the carrier gas.
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