Surface, specific, particle size distribution

A fundamental requirement in powder processing is characterization of the as-received powders (10—12). Many powder suppHers provide information on tap and pour densities, particle size distributions, specific surface areas, and chemical analyses. Characterization data provided by suppHers should be checked and further augmented where possible with in-house characterization. Uniaxial characterization compaction behavior, in particular, is easily measured and provides data on the nature of the agglomerates in a powder (13,14). 

P.O.34 is supplied in a variety of types, which differ considerably in their particle size distributions. Specific surface areas range from 15 m2/g in highly opaque versions to about 75 m2/g in transparent types. It is these physical characteristics that determine the coloristic and fastness properties of each type. Even varieties of P.O.34 with fine particle sizes are generally not resinated. 

The various bentonite samples have different physical, chemical, and colloid chemical properties. The particle size distribution, specific surface area, CEC, and swelling in water are shown in Table 3.2. For an easier comparison, some... 

Particle Size Distribution, Specific Surface Area (S), Cation-Exchange Capacity (CEC), Swelling in Water, and the Relative Amount of the Adsorbed 137Cs+ ion (x)... 

Mineralogy ISO brightness Average particle size (it) Particle size distribution Specific surface area (mVg) Particle morphology... 

Chemical Composition Particle Size Distribution Specific Surface Area. . Wet-to-Dry Shrinkage Dry Strength Base Exchange and Deflocculation Soluble Salts Fired Colour Vitrification., ... 

The most important filler characteristics determining the properties of PP composites are particle size, particle size distribution, specific surface area and shape. None of these influence stiffness very much the reinforcing effect is a result of the orientation of the anisotropic particles. All other properties are considerably affected by these filler characteristics. Yield stress and strength usually increase with decreasing particle size and increasing surface area, while deformability and impact resistance change in the opposite direction. 

This chapter will highlight the factors of packing (bulk density, voidage), rate of flow, compressibility of packing, flowability, failure properties and angle of internal friction, cohesion, strength and adhesion. The factors of particle size distribution, specific surface area and particle shape distribution have already been dealt with elsewhere (Stanley-Wood 2000, 2005). 

It may be deduced from KP = Koc x foc that partition coefficients of hydro-phobic organic compounds in general are dependent upon the chemical of interest (compound-specific properties affect the value of Koc) and the matrix properties of the medium in which it resides. In addition to the fraction of organic carbon present in the sorption phase, additional environmental factors affect partitioning. These factors include temperature, particle size distribution, the surface area of the sorbent, pH, ionic strength, the presence of suspended material or colloidal material, and the presence of surfactants. In addition, clay minerals may act as additional sorption phases for organic compounds. Nevertheless, organic carbon-normalized partition... 

Moments Moments represent a PSD by a single value. With the help of moments, the average particle sizes, volume specific surfaces, and other mean values of the PSD can be calculated. The general definition of a moment is given by (ISO 9276, Part 2 Calculation of Average Particle Sizes/Diameters and Moments from Particle Size Distributions)... 

If the form factor of the particles in a sample is known and does not change with particle size, the specific surface can be calculated from the size distribution. This procedure is time consuming and liable to produce inaccurate results because the finest portion of the distribution is often not well defined. Due to the proportionality of surface to /x, this portion contributes a large percentage to the total. Therefore, if the specific surface is a controlling parameter, e.g. for catalysts, it should be measured and not calculated. 

Fillers are those materials added to a matrix in order to improve its properties. The filler characteristics that affect the composite s properties are particle size, size distribution, specific surface area and particle shape and interfacial interactions. The shape of most mineral filler particles can be approximated as a sphere, cube, block, plate, needle or fibre. Some fillers contain a mixture of shapes. ... 

Several equations claim to predict the properties of filled plastics, especially Young s modulus. The subject has been extensively studied. In practice the effects of a given amount of a given filler on polymer properties will depend on the filler s physical and mechanical properties, its chemical composition, particle shape and size, size distribution, specific surface area, siuface chemistry, interparticle spacing and extent of agglomeration. 

Abstract This chapter deals with the non-linear viscoelastic behaviour of rubber-rubber blend composites and nanocomposites with fillers of different particle size. The dynamic viscoelastic behaviour of the composites has been discussed with reference to the filler geometry, distribution, size and loading. The filler characteristics such as particle size, geometry, specific surface area and the surface structural features are found to be the key parameters influencing the Payne effect. Non-Unear decrease of storage modulus with increasing strain has been observed for the unfilled vulcanizates. The addition of spherical or near-spherical filler particles always increase the level of both the linear and the non-linear viscoelastic properties. However, the addition of high-aspect-ratio, fiber-like fillers increase the elasticity as well as the viscosity. 

In crystallized glass type LTCCs, since one kind of ceramic powder is used, it is not necessary to consider its charging characteristics. However, in order to achieve a homogenous structure, it is desirable to have a sharp distribution of particle size, and it is necessary to decide the powder particle size and specific surface area taking into account formability and sinterability in the same way as with glass/ceramic composites. 

The differences of raw material characteristic among six kind of iron concentrates and the influences on ballability were studied from the aspect of the size distribution, specific surface area and particles morphology. The results show that the specific surface area of iron concentrates has crucial influence on ballability, and the eifective method of improving ballability for weak ballability iron concentrate has been found. 

This article studies the material characteristics of iron concentrate mainly from three aspects of the size distribution, specific surface area and micro-particle morphology, and researches the influence of material characteristic on the quality of green balls in the same pelletizing condition. 

The absorption rate behavior of crosslinked,water swellable polymers is explained in terms of diffusion of water into the polymer network. The absorption kinetics can be studied over time using a viscosity versus time measurement. Alternately, a one point determination of sorption time can be used to compare various polymers. The limitation of this method is that the polymers tested must have a sufficiently high swelling capacity so that the simplifying equations hold. This limitation can be eliminated by a proper choice of polymer/sallne solution ratio in the vortex test. The variables which control the absorption rate of ail the samples studied are swelling capacity, mesh size of powder particles and the distribution of particle sizes, the specific surface area of the product, and the apparent density of the polymer. 

Rowell and co-workers [62-64] have developed an electrophoretic fingerprint to uniquely characterize the properties of charged colloidal particles. They present contour diagrams of the electrophoretic mobility as a function of the suspension pH and specific conductance, pX. These fingerprints illustrate anomalies and specific characteristics of the charged colloidal surface. A more sophisticated electroacoustic measurement provides the particle size distribution and potential in a polydisperse suspension. Not limited to dilute suspensions, in this experiment, one characterizes the sonic waves generated by the motion of particles in an alternating electric field. O Brien and co-workers have an excellent review of this technique [65]. 

Deterrnination of the specific surface area can be made by a variety of adsorption measurements or by air-permeability deterrninations. It is customary to calculate average particle size from the values of specific surface by making assumptions regarding particle size distribution and particle shape, ie, assume it is spherical. 

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. 

The most commonly measured pigment properties ate elemental analysis, impurity content, crystal stmcture, particle size and shape, particle size distribution, density, and surface area. These parameters are measured so that pigments producers can better control production, and set up meaningful physical and chemical pigments specifications. Measurements of these properties ate not specific only to pigments. The techniques appHed are commonly used to characterize powders and soHd materials and the measutiag methods have been standardized ia various iadustries. 

The two steps in the removal of a particle from the Hquid phase by the filter medium are the transport of the suspended particle to the surface of the medium and interaction with the surface to form a bond strong enough to withstand the hydraulic stresses imposed on it by the passage of water over the surface. The transport step is influenced by such physical factors as concentration of the suspension, medium particle size, medium particle-size distribution, temperature, flow rate, and flow time. These parameters have been considered in various empirical relationships that help predict filter performance based on physical factors only (8,9). Attention has also been placed on the interaction between the particles and the filter surface. The mechanisms postulated are based on adsorption (qv) or specific chemical interactions (10). 

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