Particles dispersion uniformity

The restricted primitive model is the simplest approximation. It considers the ions as charged conducting particles dispersed uniformly in a continuum fluid made up of a compressible dielectric. The ions are characterized by their masses, charges (magnitudes), and sizes (radii), and are assumed to be spherical. The sign of the charge does not play a role in this model. The solvent is characterized by its permittivity, compressibility, and thermal expansibility. The standard state properties of the ions may then be estimated by the application of electrostatic theory and compared with the experimental values. 

Platinum deposits on onionlike fullerenes (OLFs) were studied by Xu et al. (2006). The Pt particles dispersed uniformly on OLFs had an average diameter of 3.05 nm, smaller than the 4.10 nm on PlA ulcan XC-72 prepared by the same method, and exhibited a peak current for methanol electrooxidation 20% higher than that on Pt/Vulcan XC-72. 

Morphology of the enzymatically synthesized phenolic polymers was controlled under the selected reaction conditions. Monodisperse polymer particles in the sub-micron range were produced by HRP-catalyzed dispersion polymerization of phenol in 1,4-dioxane-phosphate buffer (3 2 v/v) using poly(vinyl methyl ether) as stabihzer. °° ° The particle size could be controlled by the stabilizer concentration and solvent composition. Thermal treatment of these particles afforded uniform carbon particles. The particles could be obtained from various phenol monomers such as m-cresol and p-phenylphenol. 

Generally, the physical stability of a pharmaceutical suspension can be appropriately adjusted by an alteration in the dispersed phase rather than by significant modifications in the dispersion medium. These adjustments are mainly concerned with particle size, uniformity of particle size, and separation of the particles so that they are not likely to become larger or to form a solid cake upon standing. 

On the inherent assumptions that (a) all entering particles are uniformly dispersed over the area of the inlet duct, (b) the barrel is a perfect cylinder with a straight inlet duct entering tangentially, (c) the trajectory of die incoming particles will not result in any impingement on the gas outlet duct, (d) that the velocity of the downwardly spiraling gas... 

The fineness characteristic of a powder on a cumulative basis is represented by a straight line from the origin to 100 per cent undersize at a particle size of 50 un. If the powder is initially dispersed uniformly in a column of liquid, calculate the proportion by mass which remains in suspension in the time from commencement of settling to that at which a 40 i m particle falls the total height of the column. It may be assumed that Stokes law is applicable to the settling of the particles over the whole size range. 

At the end of the polymerisation, we have fine particles of the polymer, stabilised by the emuisifier layer and dispersed uniformly in the aqueous phase. This milky white dispersion is often called... 

While precipitation in homogenous solutions is an exceedingly simple method, usually rather low concentrations of electrolytes must be used if well-dispersed uniform particles are to be achieved. This requirement is based on the need to keep the ionic strength of the system below a critical value in order to prevent the coagulation of the precipitates, which consist, almost without exception, of charged particles. In some instances, concentrations of the reactants can be increased, if stabilizers are added into the systems, although the latter may affect the particle uniformity and/ or shape. 

There are other aerosol methods which can yield uniform powders, such as by dispersing aqueous dispersions of particles (e.g. of latex) and evaporating the water (12). In this case each droplet should contain only one particle, a task not easily accomplished. Alternatively, it is possible to nebulize solutions of electrolytes or other substances, which on removal of the liquid result in solid particles, dispersed in the carrier gas (13,14). This process has been expanded to include sintering of resulting solid aerosols in a continuous process to produce powders for various applications (15-18). 

In an early experiment, metal/graphite composite anodes were made of bored graphite rods that were packed with pressed mixtures of metal oxide powder, graphite powder, and pitch (12,13). The packed graphite rods had to be heated to about 1600°C for several hours under vacuum in order to cure the pitch. Subsequently the preparation of composite anodes was simplified by simply packing with a mixed powder of metal oxide (or metal) and carbon. Several kinds of composite rods, in which metal particles are uniformly dispersed in graphite, are now commercially available (31). 

Although they are a relatively small volume product—approximately 75,000 tons produced in 1949 (126)—interest in asphalt emulsion has continued at a high level. Abraham (6) has reviewed the patent literature relative to the types of emulsifying agents used, while commercial practice has been discussed by Day (16). The most common emulsifiers are sodium or potassium soaps of tall oil, abietic acid, or Vinsol resin, or colloidal clays such as bentonite for adhesive base emulsions. Lyttleton and Traxler (53) studied the flow properties of asphalt emulsions, and Traxler (122) has investigated the effect of size distribution of the dispersed particles on emulsion viscosity. A decrease in particle size uniformity was found to be accompanied by a decrease in consistency because particles of various size assume a more loosely packed condition than do those of the same size. 

Finely dispersed sodium chloride particles were prepared, their specific area was measured, and their solubility in ethanol at 25°C was studied. It was found that a preparation with a specific area of 4.25 x 105 cm2 g-1 showed a supersaturation of 6.71%. Estimate the radius of the NaCl (p = 2.17 gm cm-3) particles, assuming uniform spheres. Calculate 7 for the NaCl-alcohol interface from the solubility behavior of this sample. 

Breads or muffins enriched in [3-glucan may be produced using oat or barley flour or bran, as well as coarser particles such as oat flakes or cracked barley. Coarser particles tend not to disperse uniformly in a dough. Therefore, it is important to obtain a representative sample from such products in order to have uniformly distributed P-glucan-rich particles. 

Eq. (15) and 1.1 10- 7 m2/s according to Eq. (14). This significant difference may be explained by the fact, the Kang et al. used particles of uniform size whereas van der Meer et al. measured dispersion between two fractions of different particle size in a segregated fluidized bed. As adsorption in a frontal mode is performed using classified or otherwise stabilized fluidized beds, the lower Daxp resulting from van der Meer s correlation may be a better description of the solid phase dispersion in a fluidized bed for protein adsorption. 

Information derived from (1) and (2) would indicate if the particle sizes are uniform or not. A small 5A (or more accurately 5A/A) and small 5R (or 5R/r) in general imply a narrower size distribution or more uniform particle sizes. The standard deviation 5AF (or 6AF/AF) is an index of the "goodness" of particle dispersion or the spatial distribution of particles. 

When particles are uniformly dispersed in a gas, brownian motion will change the position of the individual particles but will not change the overall particle distribution. When the particles are not uniformly dispersed, brownian motion tends eventually to produce a uniform concentration throughout the gas, the particles moving away from areas of high concentration to regions of low concentration. This process, known as particle diffusion, follows the same two general laws that also apply to molecular diffusion, known as Fick s laws of diffusion. 

ZS were calculated from the same Qk experimental runs as the solid settling velocity results. Many of the solid concentration profiles for the 0.5-5 ym size particles were uniform to within 0.2 weight percent. As uniform profiles suggest an infinite dispersion coefficient, scatter for the smallest size particles was too large to be included in the analysis. For the iron oxide... 

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