Sedigraph

Fig. 3. Sedigraph particle size distribution for superground submicrometer alumina, (a) Partially dispersed (b) fully dispersed.

Thus, the random spatial distribution of the three modes of particle-fluid contacting is transformed into the ordered, temporal sequence of the three stages of the sedigraph. 

EXAMPLE 2.2 Use of the Sedimentation Equation for Particle Size Determination. A titanium dioxide pigment of density 4.12 g cm 3 is suspended in water at 33°C. At this temperature, the density and viscosity of water are 0.9947 g cm-3 and 7.523 10-3 P, respectively. A particle size analyzer (SediGraph, Micromeritics Instruments Corp., Norcross, GA 30093) plots the following data for cumulative weight percent versus equivalent spherical radius ... 

Method of analysis (Re-Tap sieve shaker, SediGraph particle size analyzer, or other equipment) ... 

A well-known device here is the Sedigraph in which a cuvette containing a suspension moves in relation to an X-ray beam (figure 13.4). 

The Sedigraph is connected to a plotter which can represent the grain size distribution in several ways, for example as in figure 13.5. 

Particle Size Analysis. Particle size distribution measurements of the dry resin were made using a Micromeritics Sedigraph 5000D particle size analyzer. This instrument employs a gravity settling technique and uses Stokes law to determine the particle size. The PSD was run over the size range of 0.36 to 100 micrometers. All measurements were made in dibutyl sebacate as the suspending medium. 

Example 1.1 One of the applications of using Stokes s law to determine the particle size is the Sedigraph particle analyzer. Table El.l shows the relationship between the cumulative weight percentage of particles and the corresponding particle terminal velocities for a powder sample. The densities of the particle and the dispersing liquid are 2,200 and 745 kg/m3, respectively. The liquid viscosity is 1.156 x 10-3 kg/m s. Find out the relationship of the mass fraction distribution to the equivalent dynamic diameter. 

Thus, the random, spatial distribution of the three modes of particle-fluid contacting is transformed into the ordered, temporal sequence of the three stages of the sedigraph. The bed collapsing method has been used, too, for other objectives in studies on fluidization (Rietema, 1967 Morooka et al., 1973). 

With all the methods, complications or uncertainties of interpretation arise due to effects associated with particle shape and with flocculation, so that the results given by different methods do not necessarily agree and usually have relative rather than absolute significance. Fig. 4.1, curve R, shows the cumulative PSD, obtained using an X-ray sedigraph, for a... 

FIGURE 1.22 Micrograph of silicon nitride powder, SN-EIO, from UBE Industries, ltd. [16] with sedigraph size distributions for various grades of this powder with 3 mV gm (EOS), 5 mVgm (E ), and 10 mVgm (ElO). 

For narrowly classified mica flakes and carbon fibers in the 1 to 100 pm size range it was found that partiele shape could be estimated from the ratio of median sizes by laser diffraetion and sedimentation [35]. Austin found that conversion between Sedigraph and sieve analyses depends not only on a mean shape factor, but also on size distribution. He generated an equation that applies for overall conversion when the sieve distribution followed a Schuman form (Equation 2.97) [36]... 

Several alumina powders have been analyzed using SEM, TEM, gas adsorption, x-ray Sedigraph and laser light scattering and the results compared [210]. 

Particle size distribution and classifier selectivity have been determined, using kernel density estimations, to data from (two) classifier flow streams. The procedure has been applied to hydrocyclones using platey particles whose sizes were determined with a Sedigraph 5100 and spheroidal particles whose size distributions were determine using the Malvern Mastersizer and the Coulter Counter [8] Svarovsky s equation was used [9,10]. 

The Sedigraph 5100 is also available with the MasterTech 051 Autosampler so that as many as eighteen samples can be analyzed unattended. 

Many industries have large data banks on product size distributions by sieve analysis and want to continue using this form of presentation. In order to accommodate this need Cho et. al. [48] converted Sedigraph data to sieve data using wet screened powder in the 38 to 53 pm size range and fitted the data to a logarithmic distribution to give the slope and median size. This procedure must be use with caution since the conversion factors are shape dependent and a new calibration is required for each product. 

Activity Software imports data from Micromeretic s Sedigraph 5100, Leeds and Northrup s Microtrac and Cilas Model 920. In operation data such as particle size distribution, surface area, filler costs or other properties are entered into the software. Target values are next assigned to the data components with the values scaled to reflect each component s... 

Veran stated that in industry, measurements are usually carried out by x-ray sedimentation and laser diffraction and they hardly ever agree. He compared the CILAS 1064, the x-ray Sedigraph 5000ET and 5100 and found that the application of an extinction coefficient brought the laser diffraction into agreement with photosedimentation [ 188]. 

Many manufacturers have large data banks using, for example, sieve analysis and they need to continue generating data in the same form. To cater for this need, some manufacturers of MALLS instruments install a conversion program, so that the instruments provide data that can be compared with historical data. However, Austin [190] compared sieve analyses with Sedigraph and Microtrac data and found that the conversion... 

When comparing results with other methods it is often necessary to dilute the suspensions without changing their state of agglomeration. Despite this, under electrokinetically stable conditions, excellent agreement was found in a comparison with the Mastersizer S, the Ultra Fine Particle Analyzer, the Sedigraph 5000D and scanning electron microscopy [265]. It was stressed however that sample preparation procedure was important. 

FIG. 21-19 The Sedigraph III 5120 Particle Size Analysis System determines particle size from velocity measurements by applying Stokes law under the known conditions of liquid density and viscosity and particle density. Settling velocity is determined at each relative mass measurement from knowledge of the distance the X-ray beam is from the top of the sample cell and the time at which the mass measurement was taken. It uses a narrow, horizontally collimated beam of X-rays to measure directly the relative mass concentration of particles in the liquid medium. 

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