Particle density, general properties

Particle shapes influence properties such as surface area, bulk density, flow, and so on. A number of methods are available for describing shape from simpler qualitative descriptions, through property ratios, to techniques that employ fast Fourier transformations to describe the projected perimeter of the particle. The measurement of the shape and the relevance of the data obtained are generally the two difficulties associated with particle shape. Fortunately, in the processing of materials physically unlike those in chemical processing, shape is perhaps is less significant and is more often than not inherently accounted for in the nominal diameter. 

Beyond similarities in bulk density, the physical properties of fly ash and bottom ash are very distinct (Table 3). The diameter of fly ash particles is generally several orders of magnitude smaller than that of bottom ash particles, leading to... 

The mechanism of particle incorporation is treated extensively in the next section, but a generalized mechanism is given here to better comprehend the effects of the process parameters. Particle incorporation in a metal matrix is a two step process, involving particle mass transfer from the bulk of the suspension to the electrode surface followed by a particle-electrode interaction leading to particle incorporation. It can easily be understood that electrolyte agitation, viscosity, particle bath concentration, particle density etc affect particle mass transfer. The particle-electrode interaction depends on the particle surface properties, which are determined by the particle type and bath composition, pH etc., and the metal surface composition, which depends on the electroplating process parameters, like pH, current density and bath constituents. The particle-electrode interaction is in competition with particle removal from the electrode surface by the suspension hydrodynamics. 

It is well known that particle shape affects many secondary properties relevant to powder handling such as the bulk density, failure properties or particle-gas interaction. For non-spherical particles, the results obtained with different methods of particle size measurement are, in general, not comparable. From the point of view of powder handling, flaky or stringy particles like wood shavings, mica or asbestos fibres are known to be difficult because they interlock and form obstructions to flow. 

In FFF, particle size, mass, density, and so forth are determined by their relationship to particle retention time r, the time required for the passage of the particle through the FFF channel. The relationship between particle properties and tT arises because a particle s position in the streamlines of a thin channel, and thus the particle s velocity, is determined by the force exerted on the particle by an external field directed at right angles to flow. The interactive force between the field and the particle can generally be expressed explicitly in terms of particle properties, thus a mathematical... 

Bulk Density—This property is generally desired to be high (spherical particles and uniform distribution) for maximum rates in compounding and processing equipment,... 

Other aggregate parameters which can affect the performance of cement include surface texture, bulk density, particle density, drying shrinkage, thermal movement and fire resistance. The properties of hard, dense limestones are such that they are generally suitable for use in concrete [8.1]. 

The Weisz-Prater criterion makes use of observable quantities like -Ra)p, the measured global rate (kmol/kg-s) dp, the particle diameter (m) pp, the particle density (kg/m ) Dg, the effective mass diffusivity (m /s) and the surface concentration of reactant (kmol/m ). The intrinsic reaction rate constant ky need not be known in order to use the Weisz-Prater criterion. If external mass transfer effects are eliminated, CAb can be used, and the effective diffusivity can be estimated using catalyst and fluid physical properties. The criterion can be extended to other reaction orders and multiple reactions by using the generalized Thiele modulus, and various functional forms are quoted in the literature [17, 26, 28]. 

For homogeneous catalysts, the process of polymer particle formation generally leads to porous, low-density polymer particles, which can cause significant increase in slurry viscosity and reactor fouling, leading to inadequate reactor temperature control. Additionally, polymer particles with poor powder properties are undesirable for postreactor polymer processing. These problems must be addressed before using soluble metallocene catalysts for industrial production of polyolefins. 

The properties, uses, and methods of formulating emulsions are graphically and comprehensively described in the trade literature, which is an excellent source of information. Most manufacturers specify properties of their emulsions in terms of percent solids, emulsion viscosity, pH, acid content, percent unreacted monomer, and density. Other properties generally described are particle size, molecular weight, film properties such as clarity, water and grease resistance, and tolerance of the emulsions to various organic and inorganic chemicals. 

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