Fine particle characterization

In recent years, disk centrifuges have been revived to characterize fine particles smaller than 1 pm, basically because of the work by Provder and coworkers in cooperation with Brookhaven Laboratories Ltd.. ... 

Some manufacturers of instruments for characterizing fine particles claim that their instruments do not need calibration. Such claims should be treated with skepticism. In practice, many sizing instruments have to be calibrated using standard powders available from several vendors.Because the various methods of exploring the size distribution of a powder evaluate different physical parameters, the size distributions of a powder generated by different methods do not always agree. The relationship between distribution fimctions, as evaluated by different methods, should be explored experimentally. ... 

Efforts to characterize fine particles including speciation of toxic metals and organometallic surface binding... 

The characteristics of a powder that determine its apparent density are rather complex, but some general statements with respect to powder variables and their effect on the density of the loose powder can be made. (/) The smaller the particles, the greater the specific surface area of the powder. This increases the friction between the particles and lowers the apparent density but enhances the rate of sintering. (2) Powders having very irregular-shaped particles are usually characterized by a lower apparent density than more regular or spherical ones. This is shown in Table 4 for three different types of copper powders having identical particle size distribution but different particle shape. These data illustrate the decisive influence of particle shape on apparent density. (J) In any mixture of coarse and fine powder particles, an optimum mixture results in maximum apparent density. This optimum mixture is reached when the fine particles fill the voids between the coarse particles. 

Aerosol Dynamics. Inclusion of a description of aerosol dynamics within air quaUty models is of primary importance because of the health effects associated with fine particles in the atmosphere, visibiUty deterioration, and the acid deposition problem. Aerosol dynamics differ markedly from gaseous pollutant dynamics in that particles come in a continuous distribution of sizes and can coagulate, evaporate, grow in size by condensation, be formed by nucleation, or be deposited by sedimentation. Furthermore, the species mass concentration alone does not fliUy characterize the aerosol. The particle size distribution, which changes as a function of time, and size-dependent composition determine the fate of particulate air pollutants and their... 

Airborne particulate matter, which includes dust, dirt, soot, smoke, and liquid droplets emitted into the air, is small enough to be suspended in the atmosphere. Airborne particulate matter may be a complex mixture of organic and inorganic substances. They can be characterized by their physical attributes, which influence their transport and deposition, and their chemical composition, which influences their effect on health. The physical attributes of airborne particulates include mass concentration and size distribution. Ambient levels of mass concentration are measured in micrograms per cubic meter (mg/m ) size attributes are usually measured in aerodynamic diameter. Particulate matter (PM) exceeding 2.5 microns (/i) in aerodynamic diameter is generally defined as coarse particles, while particles smaller than 2.5 mm (PMj,) are called fine particles. 

Fine Particles Synthesis, Characterization, and Mechanisms of Gro A4h, edited by Tadao Sugimoto... 

The frictional properties of TPs, specifically the reinforced and filled types, vary in a way that is unique from metals. In contrast to metals, even the highly reinforced plastics have low modulus values and thus do not behave according to the classic laws of friction. Metal-to-thermoplastic friction is characterized by adhesion and deformation resulting in frictional forces that are not proportional to load, because friction decreases as load increases, but are proportional to speed. The wear rate is generally defined as the volumetric loss of material over a given unit of time. Several mechanisms operate simultaneously to remove material from the wear interface. However, the primary mechanism is adhesive wear, which is characterized by having fine particles of plastic removed from the surface. 

B. H. Kaye, Direct Characterization of Fine Particles, John Wiley Sons, New York, 1981. 

Specialty products with fine particle sizes, high specific surface areas, and enhanced transparency are characterized not only by increased tinctorial strength, but also by inferior stability to solvents and light. 

The chemical and physical aspects of crud can dilfer for each separate operation and will vary in inorganic composition, organic content, color, and density. The composition of many cruds appears to have in common such constituents as Si, Al, Fe, P, SO4, particles of gypsum, clay, and other fine particles together with the solvent. Often there is a direct relation between the feed liquor and the crud compositions, indicating possible aqueous carryover as well as inefficient clarification before solvent extraction [33]. Various researchers have reported on the formation of crud and its characterization in their circuits [42-45]. 

Matijevic, E. Partsch, R.E. (2000) Synthesis of monodispersed colloids by chemical reactions. In Sugimoto.T. (ed.) Fine Particles Synthesis, Characterization and Mechanism of Growth. Marcel Dekker, New York Matijevic, E. Sapieszko, R.S. (2000) Forced hydrolysis in homogeneous solutions. In Sugi-moto, T. (ed.) Fine Particles. Basel, Marcel Dekker, 2-34... 

Ohta, S., M. Hori, S. Yamagata, and N. Murao, Chemical Characterization of Atmospheric Fine Particles in Sapporo with Determination of Water Content, Atmos. Environ., 32, 1021-1025 (1998). 

Particles produced in the gas phase must be trapped in condensed media, such as on solid substrates or in liquids, in order to accumulate, stock, and handle them. The surface of newly formed metallic fine particles is very active and is impossible to keep clean in an ambient condition, including gold. The surface must be stabilized by virtue of appropriate surface stabilizers or passivated with controlled surface chemical reaction or protected by inert materials. Low-temperature technique is also applied to depress surface activity. Many nanoparticles are stabilized in a solid matrix such as an inert gas at cryogenic temperature. At the laboratory scale, there are many reports on physical properties of nanometer-sized metallic particles measured at low temperature. However, we have difficulty in handling particles if they are in a solid matrix or on a solid substrate, especially at cryogenic temperature. On the other hand, a dispersion system in fluids is good for handling, characterization, and advanced treatment of particles if the particles are stabilized. 

Fine particles synthesis, characterization, and mechanisms of growth / edited by Tadao Sugi-moto. 

For fine particles, despite the fact that the major rationale behind diffusive sampling of a gas is to achieve discrimination from the concurrently present atmospheric aerosol, relatively little attention has been paid to actually characterizing the particle transmission through these systems. A summary of existing data has been presented (40). The only thorough charac-... 

Niemi JV, Tervahattu H, Vehkamaki H, Kulmala M, Koskentalo T, Sillanpaa M, Rantamaki M (2004) Characterization and source identification of a fine particle episode in Finland. Atmos Environ 38 5003-5012... 

Uhde, E., He, C. and Wensing, M. (2006) Characterization of ultra-fine particle emissions from a laser printer. Proceedings of Healthy Buildings, Lisboa, pp. 479-82. 

During biomass and fuel burning, a complex mixture of ill-characterized volatile organic matter are released into the atmosphere (Andreae and Merlet, 2001). It contributes to the formation of aerosols and fine particles of sizes up to 100 pm. After an estimated lifetime of 7.9 days (Cook and Wilson, 1996), they are either degraded or are removed from the atmosphere by precipitation. However, they can be transported a considerable distance. For example, boreal forest fires contribute substantially to atmospheric BC in the Arctic (Cook and Wilson, 1996), and Antarctica receives BC from biomass burning in the tropics (Wolff and Cachier, 1998). On a global scale the amount of atmospheric emission is estimated with 5-6Tg BC yr 1,... 

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