Particle-size distribution

Abstract: Properties of Gases Uniform Particle Motion Particle Size Statistics Straight-Line Acceleration and Curvilinear Particle Motion Adhesion of Particles Brownian Motion and Diffusion Thermal and Radiometric Forces Filtration Sampling and Measurement of Concentration Respiratory Deposition Coagulation Condensation and Evaporation Atmospheric Aerosols Electrical Properties Optical Properties Bulk Motion of Aerosols Dust Explosions Bioaerosols Microscopic Measurement of Particle Size Production of Test Aerosols Appendices Index

Abstract: Sampling of powders sampling of dusty gases in gas streams sampling and sizing from the atmosphere - air technology, Atcor Net 2000, Bausch and Lomb, Beckman, Centre for Air Environmental Studies, Climet Series 7000, Coulter Model 550 contamination monitor, Dynac, Gardner, GCA Miniram, Insitec PCSV-P, Kratel Partoscope, Leitz Tyndalloscope, Met One particle counters, Pacific Scientific Hiac/Royco particle counting systems, particle measuring systems, RAC particle monitors, Rotheroe and Mitchell digital dust indicator, Saab photometer, Sartorius, Sinclair Particle size, shape and distribution - shape regeneration by Fourier analysis, the Rosinn-Rammler distribution, mean particle sizes and specific surface evaluation for Rosinn-Rammler distribution Sieving microscopy interaction between particles and fluids in a gravitational field dispersion of powders incremental methods of particle size determination cumulative methods of sedimentation size analysis fluid classification - the Warmain cyclosizer, the Humboldt particle size analyzer TDS, the cross-flow elbow classifier, the Bahco classifier, the BCURA centrifugal elutriator, Analysette 9, the Donaldson classifier, the Micromeritics classifier Centrifugal methods - early instruments - the Marshall centrifuge and the MSA particle size analyser, the Alpine sedimentation centrifuge, the Mikropul Sedimentputer, the LADAL X-ray centrifuge, the LADAL pipette withdrawal centrifuge The electrical sensing zone method of particle size distribution determination (the Coulter principle) radiation scattering methods of particle size determination high-order Tyndall spectr (HOTS) permeametry and gas diffusion - alternative derivation of Kozeny's equation using equivalent capillaries Gas adsorption - BET isotherm for multilayer adsorption, comparison between BET and HJr methods, the Frenkel-Halsey-Hill equation (FHH), the Dubinin-Radushkevich equation (D-R), Kiselev's equation Other methods for determining surface area - Langmuir trough, Gravimetric method, the Rayleigh interferometer Determination of pore size distribution by gas adsorption - the Kelvin equation On-line particle analysis - Brinkmann analyser, Climet particle counting systems, Flowvision, Hiac/Royco (Pacific Scientific) particle counters, Horiba particle size analysers, the Insitic particle counter, Kane May particle size analysers, Kratel Partascope, Lasentec, Talbot optical-electronic method, the Erdco acoustical counter, the Coulter on-line monitor screening - the Cyclosensor, non-Newtonian rheological properties Appendix 1 Equipment and suppliers, manufacturers' and suppliers' addresses

Abstract: Motor vehicle emissions usually constitute the most significant source of ultrafine particles (diameter <0.1 microm) in an urban environment, yet little is known about the concentration and size distribution of ultrafine particles in the vicinity of major highways. In the present study, particle number concentration and size distribution in the size range from 6 to 220 nm were measured by a condensation particle counter (CPC) and a scanning mobility particle sizer (SMPS), respectively. Measurements were taken 30, 60, 90, 150, and 300 m downwind, and 300 m upwind, from Interstate 405 at the Los Angeles National Cemetery. At each sampling location, concentrations of CO, black carbon (BC), and particle mass were also measured by a Dasibi CO monitor, an aethalometer, and a DataRam, respectively. The range of average concentration of CO, BC, total particle number, and mass concentration at 30 m was 1.7-2.2 ppm, 3.4-10.0 microg/m3, 1.3-2.0 x 10(5)/cm3, and 30.2-64.6 microg/m3, respectively. For the conditions of these measurements, relative concentrations of CO, BC, and particle number tracked each other well as distance from the freeway increased. Particle number concentration (6-220 nm) decreased exponentially with downwind distance from the freeway. Data showed that both atmospheric dispersion and coagulation contributed to the rapid decrease in particle number concentration and change in particle size distribution with increasing distance from the freeway. Average traffic flow during the sampling periods was 13,900 vehicles/hr. Ninety-three percent of vehicles were gasoline-powered cars or light trucks. The measured number concentration tracked traffic flow well. Thirty meters downwind from the freeway, three distinct ultrafine modes were observed with geometric mean diameters of 13, 27, and 65 nm. The smallest mode, with a peak concentration of 1.6 x 10(5)/cm3, disappeared at distances greater than 90 m from the freeway. Ultrafine particle number concentration measured 300 m downwind from the freeway was indistinguishable from upwind background concentration. These data may be used to estimate exposure to ultrafine particles in the vicinity of major highways.

Abstract: Classically, the grain size of soil and sediment samples is determined by the sieve method for the coarse fractions and by the pipette method, based on the ‘Stokes’ sedimentation rates, for the fine fractions. Results from the two methods are compared with results from laser diffraction size analysis, which is based on the forward scattering of monochromatic coherent light. From a point of view of laboratory efficiency, the laser sizing technique is far superior. Accuracy and reproducibility are shown by measurements on certified materials. It appears that laser grain size measurements of certified materials correspond very well with the certificated measurements. Tests were also done on a set of randomly selected sediments of fluvial, aeolian and lacustrine origin. Except for the (<2 μm) clay fraction, there is a coarsening of the mean diameter of one to two size classes (0.25 ɛ), caused by the non-sphericity of the particles. The platy form of the clay particles induces considerable differences (eight size classes) between pipette and laser measurements: the <2 μm grain size, defined by the pipette method corresponds with a grain size of 8 μm defined by the Laser Particle Sizer for the studied sediments. Using a higher grain size level for the clay fraction, when laser analysis is applied, enables workers in the geological and environmental field to compare classical pipette analysis with a laser sizing technique.

Abstract: Iron oxide colloidal nanomagnets generate heat when subjected to an alternating magnetic field. Their heating power, governed by the mechanisms of magnetic energy dissipation for single-domain particles (Brown and Neel relaxations), is highly sensitive to the crystal size, the material, and the solvent properties. This study was designed to distinguish between the contributions of Neel and Brownian mechanisms to heat generation. Anionic nanocrystals of maghemite and cobalt ferrite, differing by their magnetic anisotropy, were chemically synthesized and dispersed in an aqueous suspension by electrostatic stabilization. The particles were size-sorted by successive electrostatic phase separation steps. Parameters governing the efficiency of nanomagnets as heat mediators were varied independently; these comprised the particle size (from 5 to 16.5 nm), the solvent viscosity, magnetic anisotropy, and the magnetic field frequency and amplitude. The measured specific loss powers (SLPs) were in quantitative agreement with the results of a predictive model taking into account both Neel and Brown loss processes and the whole particle size distribution. By varying the carrier fluid viscosity, we found that Brownian friction within the carrier fluid was the main contributor to the heating power of cobalt ferrite particles. In contrast, Neel internal rotation of the magnetic moment accounted for most of the loss power of maghemite particles. Specific loss powers were varied by 3 orders of magnitude with increasing maghemite crystal size (from 4 to 1650 W/g at 700 kHz and 24.8 kA/m). This comprehensive parametric study provides the groundwork for the use of anionic colloidal nanocrystals to generate magnetically induced hyperthermia in various media, including complex systems and biological materials.