| 1. |
- Damour, T M, et al.
(author)
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Experimental evidence for evaporation/condensation nonuniform flow in a horizontal aerosol generator
- 2005
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In: Aerosol Science and Technology. - : Informa UK Limited. - 1521-7388 .- 0278-6826. ; 39:5, s. 444-451
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Journal article (peer-reviewed)abstract
- The formation of deposition patterns in the cooling zone during operation of a horizontal evaporation/condensation nanoparticle generator was studied to obtain information about flow conditions during particle formation. Quartz reactor tubes were used together with a simple light attenuation measurement to characterize deposition as a function of axial location. Results for the onset and pattern of deposition for four different metals-indium, gallium, silver, and lead-were obtained, and size distributions for indium and gallium particle nanoparticles at different temperatures were measured. Distinct deposition bands could be observed resulting from vapor deposition, nanioparticle deposition, or a combination of both. The location or the bands varied with metal and evaporation temperature. Experimentally observed fluctuations in temperature, bimodal size distributions obtained at the highest furnace temperatures, as well as asymmetric deposition patterns suggested the How in the cooling portion of the generator is nonuniform, possibly as a result of buoyancy. These results are important for the design of nanoparticle generation systems, in that horizontal evaporation/condensation generators are often chosen on the basis of assumed simplicity with respect to flow, and this may not always be the case.
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| 2. |
- Gustavsson, Eva, et al.
(author)
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Evaluation of Aerodynamic Particle Sizer and Electrical Low-Pressure Impactor for Unimodal and Bimodal Mass-Weighted Size Distributions
- 2005
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In: Aerosol Science and Technology. - : Taylor and Francis Ltd. - 0278-6826 .- 1521-7388. ; 39:9, s. 871-887
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Journal article (peer-reviewed)abstract
- The objective of this study was to investigate the feasibility of the Aerodynamic Particle Sizer (APS) and the Electrical Low-Pressure Impactor (ELPI) to study mass weighted particle size distributions. Unimodal and bimodal liquid test aerosols were produced to a small chamber. Simultaneous measurements were performed with an APS 3320, an APS 3321, an ELPI and a Dekati Low-Pressure Impactor (DLPI) analyzed gravimetrically. ELPI current and mass responses were simulated for lognormal size distributions using a parameterization of the impactor kernel functions. In experiments with a single coarse mode, the mass ratio to the DLPI was between 0.75 and 1.15 for both APS models up to 5 µ m and for the ELPI up to 3 µ m. For larger sizes the ELPI and APS 3320 overestimated and the APS 3321 underestimated the concentration. In experiments with a single fine mode, submicrometer ELPI and DLPI results were in good agreement. However, in contrast to the DLPI all three spectrometers showed a significant mass fraction above 1 µ m. In experiments with a bimodal size distribution, the mass ratios were altered compared to single coarse mode experiments. Simulations showed that uncertainties in ELPI measurements of larger particles occur when concentrations of small particles are high. Several mechanisms that may bias ELPI and APS measurements are described. With knowledge of these, ELPI and APS 3321 can, under many circumstances give accurate time-resolved mass size distributions for particles smaller than 3 and 5 µm, respectively.
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| 3. |
- Held, Andreas, et al.
(author)
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A Thermal Desorption Chemical Ionization Ion Trap Mass Spectrometer for the Chemical Characterization of Ultrafine Aerosol Particles
- 2009
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In: Aerosol Science and Technology. - : Informa UK Limited. - 0278-6826 .- 1521-7388. ; 43:3, s. 264-272
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Journal article (peer-reviewed)abstract
- The development of a thermal desorption chemical ionization ion trap mass spectrometer for the chemical characterization of ultrafine aerosol particles is reported and first experimental results are presented. Atmospheric particles are size-classified and collected using a unipolar charger, a radial differential mobility analyzer and an electrostatic precipitator, and analyzed after thermal desorption and chemical ionization using an ion trap mass spectrometer. Integration of an ion trap mass spectrometer allows for fast scans of the entire mass spectrum every 0.5 s and bears the potential to identify unknown particulate compounds by tandem mass spectrometry. Particle collection efficiencies range from 90-100% for 25 nm particles to about 50% for 40 nm particles. In the current configuration, the absolute sensitivity of the instrument with regard to ammonium is in the range of 10-100 pg NH4_+. In ambient samples collected in the Colorado Front Range, NH4+ was the major signal peak in the positive ion spectrum, and additional minor signals and peak patterns of organic compounds including methylamine were found.
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| 4. |
- Larsson, Ann-Charlotte, et al.
(author)
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Deactivation of SCR Catalysts by Exposure to Aerosol Particles of Potassium and Zinc Salts
- 2007
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In: Aerosol Science and Technology. - : Informa UK Limited. - 0278-6826 .- 1521-7388. ; 41:4, s. 369-379
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Journal article (peer-reviewed)abstract
- Generated aerosol particle deposition has been applied in laboratory scale to induce deactivation of commercial Selective Catalytic Reduction (SCR) catalysts Of V2O5-WO3/TiO2 monolithic type. The monolithic catalyst has been exposed to the generated submicrometer particle of inorganic salts, KCl, K2SO4, and ZnCl2 at 200 degrees C in a tubular reactor. The generated particles have been deposited on the catalytic surfaces by utilization of an electrostatic field. Physical characterization of the generated aerosol particles were conducted by Scanning Mobility Particle Sizer (SMPS) and Electric Low Pressure Impactor (ELPI) with and without catalyst in order to investigate the magnitude of the particle deposition. Particle charge distribution was also evaluated with a Tandem Differential Mobility Analyser (TDMA) set up.SCR is the most common method to commercially reduce NOx emissions from combustion processes. Catalyst lifetime is important for process economics and extending catalyst life can allow future strengthened emission legislation and diminished NOx emissions.Verification of particle deposition has been conducted through comparison with catalyst samples exposed to commercial biomass combustion condition.The reactivity of both fresh and exposed catalyst samples as well as commercially used samples was examined in SCR reaction and the methods of deposition as well as the influence of the different salts on catalytic performance have been explored.Catalyst samples have been evaluated with Scanning Electron Microscopy (SEM) with respect to surface morphology of the catalyst material. The laboratory deactivated catalyst samples showed resemblance with the commercially exposed catalyst sample with respect to salts concentration and deposition of the salts particles. The obtained influence on catalyst activity was comparable with commercially obtained catalyst activity reductions at comparable potassium concentration levels.
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| 5. |
- Nguyen Ngoc, Hung, et al.
(author)
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Design and calibration of a multi-channel aerosol sampler for tropopause region studies from the CARIBIC platform
- 2006
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In: Aerosol Science and Technology. - : Informa UK Limited. - 1521-7388 .- 0278-6826. ; 40:8, s. 649-655
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Journal article (peer-reviewed)abstract
- An aircraft-based, multi-channel aerosol sampler for studies of the upper troposphere and lowermost stratosphere from the CARIBIC ( Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container) platform was designed and calibrated. The sampler operates with an impaction technique at a flow rate of 10.4 lpm and consists of sixteen sampling channels. Samples are collected in a time sequence. Each channel contains two sample types that are used for quantitative measurement of concentrations, using particle-induced X-ray emission ( PIXE), and single particle analysis with electron microscopy. The minimum detection limits for PIXE analysis after 1.5 h sampling are, for example, 2.0, 0.14, and 0.02 ng/m(3) STP ( standard temperature and pressure) for sulfur, potassium, and nickel. Calibration included penetration studies of a cyclone arrangement used to define the upper size limit in the sampling to 2.0 mu m diameter and the collection efficiency of the impactor. Both components of the sampling system showed penetration and collection efficiency close to 100%, respectively, in the particle size range of interest. The impactor cut-off was found to be dependent on the ratio of the impactor upstream-to-downstream pressure for ratios well below the critical pressure drop (i.e., the pressure where the jet reaches sonic velocity) being 0.15 mu m and 0.08 mu m for ratios 0.41 and 0.2.
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| 6. |
- Pagels, Joakim, et al.
(author)
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Processing of Soot by Controlled Sulphuric Acid and Water Condensation - Mass and Mobility Relationship
- 2009
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In: Aerosol Science and Technology. - : Informa UK Limited. - 1521-7388 .- 0278-6826. ; 43:7, s. 629-640
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Journal article (peer-reviewed)abstract
- The effects of atmospheric processing on soot particle morphology were studied in the laboratory using the Differential Mobility Analyzer-Aerosol Particle Mass Analyzer (DMA-APM) and the DMA-DMA (Tandem DMA) techniques. To simulate atmospheric processing, combustion soot agglomerates were altered by sulphuric acid vapor condensation, relative humidity (RH) cycling, and evaporation of the sulphuric acid and water by heating. Primary investigated properties were particle mobility size and mass. Secondary properties, derived from these, include effective density, fractal dimension, dynamic shape factor, and the mass fraction of condensed material. A transformation of the soot particles to more compact forms occurs as sulphuric acid and water condense onto fresh soot. The particle mass increases and initially the mobility diameter decreases, indicating restructuring of the soot core, likely due to surface tension forces. For a given soot source and condensing liquid, the degree of compaction depends strongly on the mass (or volume) fraction of condensed material. For water and sulphuric acid condensing on combustion soot, a mass increase of 2-3 times is needed for a transformation to spherical particles. In the limit of spherical particles without voids, the effective density then approaches the inherent material density, the fractal dimension approaches 3 and the dynamic shape factor approaches 1. Our results indicate that under typical atmospheric conditions, soot particles will be fully transformed to spherical droplets on a time scale of several hours. It is expected that the morphology changes and addition of soluble material to soot strongly affect the optical and hygroscopic properties of soot.
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| 7. |
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| 8. |
- Saqnati, Mehri, et al.
(author)
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Hygroscopic behaviour of aerosol particles emitted from biomass fired grate boilers
- 2005
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In: Aerosol Science and Technology. - : Taylor & Francis Group. - 0278-6826 .- 1521-7388. ; 39:91, s. 919-930
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Journal article (peer-reviewed)abstract
- This study focuses on the hygroscopic properties of submicrometer aerosol particles emitted from two small-scale district heating combustion plants (1 and 1.5 MW) burning two types of biomass fuels (moist forest residue and pellets). The hygroscopic particle diameter growth factor (Gf ) was measured when taken from a dehydrated to a humidified state for particle diameters between 30– 350 nm (dry size) using a Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA). Particles of a certain dry size all showed similar diameter growth and the Gf at RH = 90% for 110/100 nm particles was 1.68 in the 1MWboiler, and 1.5 in the 1.5MWboiler. These growth factors are considerably higher in comparison to other combustion aerosol particles such as diesel exhaust, and are the result of the efficient combustion and the high concentration of alkali species in the fuel. The observed water uptake could be explained using the Zdanovski-Stokes-Robinson (ZSR) mixing rule and a chemical composition of potassium salts only, taken from ion chromatography analysis of filter and impactor samples (KCl, K2SO4, andK2CO3). Agglomerated particles collapsed and became more spherical when initially exposed to a moderately high relative humidity. When diluted with hot particle-free air, the fractallike structures remained intact until humidified in the H-TDMA. A method to estimate the fractal dimension of the agglomerated combustion aerosol and to convert the measured mobility diameter hygroscopic growth to the more useful property volume diameter growth is presented. The fractal dimension was estimated to be ∼2.5.
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| 9. |
- Svane, Maria, 1957, et al.
(author)
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On-Line Chemical Analysis of Individual Alkali-Containing Aerosol Particles by Surface Ionization Combined with Time-of-Flight Mass Spectrometry
- 2009
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In: Aerosol Science and Technology. - : Informa UK Limited. - 0278-6826 .- 1521-7388. ; 43:7, s. 653-661
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Journal article (peer-reviewed)abstract
- An aerosol mass spectrometer for measurements of the alkali metal content in individual submicron aerosol particles is presented. The instrument combines surface ionization of individual particles on a hot platinum surface with orthogonal acceleration time-of-flight mass spectrometry. The instrument simultaneously provides the content of different alkali metal elements in single particles with high sensitivity. The instrument is characterized in laboratory experiments, and determination of the alkali metal content is demonstrated for particle diameters of 50-500 nm. The technique is demonstrated in ambient air measurements at an urban background site, and sea spray particles and particles originating from biomass burning are identified based on their content of sodium and potassium. Possible further improvements and applications of the technique are discussed.
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| 10. |
- Piao, Shuying, et al.
(author)
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A New Compound in the Cu-In System : the Synthesis and Structures of Cu10In7
- 2008
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In: Zeitschrift für Anorganische und Allgemeines Chemie. - : Wiley. - 0044-2313 .- 1521-3749. ; 634:14, s. 2589-2593
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Journal article (peer-reviewed)abstract
- A new binary phase, Cu10In7, was found during the investigation of the eta-phase field in the Cu-In system. Single crystals Cu10In7 were grown from a melt under an inert atmosphere. The compound crystallizes in the monoclinic space group C2/m with cell parameters a = 13.8453(2) angstrom, b = 11.8462(1) angstrom, c = 6.7388(1) angstrom and beta = 91.063(1). The structure is based on a unit of face-sharing octachedra consisting of five Cu4In2 octahedra terminated by Cu5In octahedra at both ends. The crystal Structure is closely related to the Cu11In9 structure type.
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