Chemical composition particles

An important advance in continuous analyzers uses both particle size data and single-particle chemical composition. These instruments employ a method of rapid depressurization of the aerosol that produces a particle beam and irradiation of particles to generate ions that are analyzed by mass spectroscopy. The single particle analyzers have been employed in atmospheric research recently but have not reached the stage where they are used routinely in air monitoring. 

One of the features of the catalysts for production of carbon nanofibers and especially nanotubes consists in a big role of catalyst particle size besides the catalyst chemical composition. The size can not be assigned in advance, and only the change of synthesis method or synthesis condition allows to produce the most active particles. Chemical composition of the catalyst can be changed during pyrolysis. 

Interest in different aspects of particle chemical compositions is driven... 

Particle chemical composition is of toxicological concern, and this is reflected in limits on occupational exposures, air pollution emission standards, and ambient air quality standards, Careful control of aerosol chemiciil properties is also a central feature in commercial processes such as the fabrication of optical fibers in which a silica aerosol produced by the... 

Particle chemical composition is determined by the specific system being examined. Therefore, it is important to understand when composition may or may not be overlooked in deference to information on particle behavior arising from data collected on different systems. Overall composition is not of itself adequate because particle structure, morphology, and size play important roles. These questions will all be discussed. 

To elucidate some aspects of the phenomena caused by HTT of fumed oxides (possessing different specific surface area, degree of aggregation of primary particles, chemical composition, and reactivity) in the steam phase, their structural changes occurring at different treatment temperatures are analyzed in the subsequent sections on the basis of the adsorption data, the FTTR spectra, the AFM images of initial and treated samples, and theoretical calculations (Gun ko et al. 2004a). 

Voisin, D., Smith, J.N., Sakurai, H., McMurry, P.H., Eisele, E.L. (2003) Thermal Desorption Chemical Ionization Mass Spectrometer for Ultrafine Particle Chemical Composition. Aerosol Sci. Technol. 37 471-475. 

It has been shown (IsraelachvUi, 2011) that for diameters beyond 0.5 nm a molecule must be considered a small particle and the equations of Table 2.2 should be used for the van der Waals forces. The effective Hamaker constant, which depends on the particles (chemical composition) and the medium, determines the effective strength of the vdW interactions. 

The second term on the RHS of (4.329) is related to the heat released by changes in the single particle chemical composition due to interfacial mass transfer and surface reactions. 

Because model colloids tend to have a ratlier well defined chemical composition, elemental analysis can be used to obtain detailed infonnation, such as tlie grafted amount of polymer in tire case of sterically stabilized particles. More details about tire chemical stmcture can be obtained using NMR techniques (section B1.13). In addition, NMR... 

The properties of fillers which induence a given end use are many. The overall value of a filler is a complex function of intrinsic material characteristics, eg, tme density, melting point, crystal habit, and chemical composition and of process-dependent factors, eg, particle-si2e distribution, surface chemistry, purity, and bulk density. Fillers impart performance or economic value to the compositions of which they are part. These values, often called functional properties, vary according to the nature of the appHcation. A quantification of the functional properties per unit cost in many cases provides a vaUd criterion for filler comparison and selection. The following are summaries of key filler properties and values. 

The particle size and chemical composition of lead and lead compounds affect the readiness with which lead is absorbed from the lungs and digestive tract (see Lead compounds, industrial toxicology). Larger particles and compounds having low aqueous solubiHty are less hazardous than finely divided particles and compounds of higher solubiHty. 

The value of pigments results from their physical—optical properties. These ate primarily deterrniaed by the pigments physical characteristics (crystal stmcture, particle size and distribution, particle shape, agglomeration, etc) and chemical properties (chemical composition, purity, stabiUty, etc). The two most important physical—optical assets of pigments are the abiUty to color the environment in which they ate dispersed and to make it opaque. 

Because the regions of the alimentary tract vary widely ia pH and chemical composition, many different commercial formulations of barium sulfate are available. The final preparations of varyiag viscosity, density, and formulation stabiUty levels are controlled by the different size, shape, uniformity and concentration of barium sulfate particles and the presence of additives. The most important additives are suspending and dispersiag agents used to maintain the suspension stabiUty. Commercial preparations of barium sulfate iaclude bulk and unit-dose powders and suspensions and principal manufacturers are E-Z-EM (Westbury, New York), Lafayette-Pharmacol, Inc. (Lafayette, Indiana), and Picker International, Inc. (Cleveland, Ohio). 

Wood (qv) is arguably the oldest building material used by humans to constmct their dweUings. It is a natural product obtained from trees, used in both stmctural and decorative appHcations. The chemical composition of wood is largely cellulose (qv) and lignin (qv). Today there are a variety of composite or reconstituted wood products, such as plywood, particle board, wood fiber boards, and laminated stmctural beams, where small pieces of wood or wood fiber are combined with adhesives to make larger sheets or boards (see Laminates). 

Clay particles are so finely divided that clay properties are often controlled by the surface properties of the minerals rather than by bulk chemical composition. Particle size, size distribution, and shape the nature and amount of both mineral and organic impurities soluble materials, nature, and amount of exchangeable ions and degree of crystal perfection are all known to affect the properties of clays profoundly. 

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