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| 2. |
- Deppert, Knut, et al.
(författare)
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Size-selected nanocrystals of III-V semiconductor materials by the aerotaxy method
- 1998
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Ingår i: Journal of Aerosol Science. - 0021-8502. ; 29:5-6, s. 737-748
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a fabrication route to produce size-selected III-V semiconductor nanocrystals via a simple, reliable, and efficient aerosol route. Since this approach includes the reaction of aerosol particles and a self-organized growth of a new compound, all in the aerosol phase, we call this process aerotaxy. Size-selected nanocrystals of different III-V compounds in a diameter range below 20 nm were fabricated using this method. Through the reaction of arsine with gallium droplets or of phosphine with indium droplets, GaAs and InP clusters were formed. Our approach opens the possibility to produce contamination-free and size-selected nanocrystals of compound semiconductor materials with considerable freedom in composition and size.
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| 3. |
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| 4. |
- Gudmundsson, Anders, et al.
(författare)
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Characteristics of Mult-Nozzle Impactors with 50 µm Laser-Drilled Nozzles
- 1995
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 26:6, s. 915-931
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to provide data for the design of multi-nozzle impactors giving size-fractionated samples for X-ray emission analysis and for size-distribution determinations of the α-particle activity from aerosol-particle-attached radon progenies. Different multi-nozzle impactors with laser-drilled 50–60 μm diameter nozzles designed for a cut-off diameter of about 0.05 μm were experimentally characterised. The nozzles were placed in a spiral pattern within a circle of 8.0 mm diameter. The nozzle-plate porosities were 0.013 and 0.050 (porosity = total cross-sectional area of nozzles divided by nozzle-plate area). The results show that laser-drilled nozzles can be used for multi-nozzle impactors and that the maximum nozzle-plate porosity is limited by the cross flow. The collection characteristics of the multi-nozzle impactors studied here were found to be more dependent on the Reynolds number and the S/W ratio [the ratio of the distance (S) between nozzle plate and impaction plate to the nozzle diameter (W)], than what has been shown for single-nozzle impactors. The S/W ratio and the Reynolds number must be considered if high size resolution is to be achieved.
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| 5. |
- Gudmundsson, Anders, et al.
(författare)
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Deposition of Airborne Particles onto the Human Eye - Wind Tunnel Studies of the Deposition Velocity onto the Eyes of a Mannequin
- 1997
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Ingår i: Journal of Aerosol Science. - 0021-8502. ; 28:6, s. 1085-1100
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Tidskriftsartikel (refereegranskat)abstract
- Abstract In the field of occupational hygiene much consideration is devoted to the uptake through the human airways, but there are also reports of irritations, complaints and hazards or potential hazards due to particle deposition onto the eyes. There is a need for data regarding the dependence of the deposition rate on particle size and environmental parameters in order to formulate sampling criteria and to find dose-response relations. The deposition of airborne particles onto the human eye was studied by making use of a dummy, the eyes of which were covered with pieces of transparent sticky foil. The dummy was exposed to airborne particles in a wind tunnel. The airborne particle concentration was simultaneously measured using an Aerodynamic Particle Sizer (APS, TSI Inc., U.S.A.). The deposited particles were counted using an optical microscope equipped with an image analyser. For the particle sizes (2–30 μm), wind velocities (0.5 and 1.0 m s−1), wind directions (0, 90 and 180°) and turbulence intensities (1.3 and 19%) employed in this study, deposition velocities onto the eyes were determined to be in the range of 0.001–1 cm s−1.
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| 6. |
- Martinsson, Bengt G.
(författare)
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Physical basis for a droplet aerosol analysing method
- 1996
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 27:7, s. 997-1013
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Tidskriftsartikel (refereegranskat)abstract
- A technique for the characterisation of droplet aerosols is presented and theoretically evaluated. The system, which finds applications for example in the experimental study of cloud formation and cloud water chemistry, relies on a four-step process. The droplet aerosol is electrically charged in a unipolar charging unit, followed by diffusion drying of the droplets, resulting in charged particles consisting of non-volatile matter (droplet residues). In the third step, the residual particles are classified by electrostatic spectrometry, and in the final step the residual particles are detected, collected or further characterised. The basic function in respect of the charging process and the particle interaction with water vapour is demonstrated by model calculations, which show that droplets which are activated in a thermodynamical sense can be separated from unactivated droplets. Different strategies for the application of the system are briefly outlined. By measuring two parameters, associated droplet size and residual particle size can be determined. Results from the first field measurement campaign of the resulting instrument are also briefly presented.
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| 7. |
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| 8. |
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| 9. |
- Spanne, Mårten, et al.
(författare)
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Characteristics of Particle Emissions at Paint Manufacturing
- 1996
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Ingår i: Journal of Aerosol Science. - 0021-8502. ; 27 S1, s. 437-438
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Tidskriftsartikel (refereegranskat)abstract
- The handling of pigments and powders in paint manufacturing cause emissions of airborne particles. A great variety of substances occur. Previous studies (Bohgard et al., 1994) of simulations of pouring of pigments, which occur in small scale weighing procedures, showed typically bimodal size distribution including a sub-micron and a super-micron mode.The objective of the study was to get detailed knowledge on the relation between different source processes (depending on production technology, equipment and the manual handling routines) and aerosol characteristics.Super-micron particles were continuously measured with a time-of-flight instrument (Aerodynamic Particle Sizer, APS TSI Inc.) and sub-micron particles with an electric mobility spectrometer (Scanning Mobility Particle Sizer, SMPS TSI Inc.). In addition filter sampling techniques for standardised work-place sampling (so-called total dust filter cassettes, a cyclone sampler for respirable dust and IOM-samplers for inhalable dust) have been used for idealised exposure/area measurements using a rotating mannequin as a carrier of these samplers. The filters were analysed gravimetrically and with Particle Induced X-ray Emission Analysis. The aerosols were measured during manufacturing of batches of paint. Sources and source mechanisms, as pouring pigments from bags, disposal of packages, mixing of powders and pigments and suspected re-suspension sources, were documented simultaneously with the performance of the measurements.Figure 1 shows examples of size distributions obtained with the APS and SMPS. The size distributions have essentially bimodal shapes with median diameters of 0.05 -0.4 [mu ]m and of 2-5 [mu ]m respectively. Rapid variation in concentration occurs.Preliminary results show that several sources occur. Irregular activities and events as disposal of package material, cleaning, leakage from conveyor tubes and re-suspension due to wind velocities from open gates and moving vehicles significantly contribute to the particle concentrations.Filter sampling with the samplers mounted on a mannequin torso, rotating 360 degrees forth and back, is advantageous by giving idealised measures on exposure. Samplers mounted on equal horizontal level will have equal sampling location integrated over time. Furthermore, the sampling procedure emulate sampling in accordance with sampling conventions. Inlet characteristics of samplers mounted on a body differ from characteristics of free-hanging samplers (Vincent, 1989). Higher estimated mass concentrations were obtained with the IOM-samplers for inhalable dust than with the 37 mm open-face [ldquo ]total dust[rdquo ] cassettes.Figure omitted
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| 11. |
- Bishop, D. M., et al.
(författare)
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Effects of vibration on the polarizability and the first and second hyperpolarizabilities of HF, HCl, and HBr
- 1999
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Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 111:7, s. 3042-3050
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Tidskriftsartikel (refereegranskat)abstract
- We report calculations, using electron uncorrelated and correlated wave functions, of the electronic and vibrational properties which pertain to certain nonlinear optical properties for HF, HCl, and HBr. Our main focus is on vibrational effects (zero-point-vibrational averaging and pure vibration). Analysis of the results obtained at various levels of approximation indicates that first-order perturbation theory is generally adequate for finding the zero-point-vibrational-averaging corrections for these molecules and that complete second-order perturbation theory nearly always gives reliable results for the pure vibrational corrections. Attention is drawn to some differences with previously published results for these properties. © 1999 American Institute of Physics.
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