Calculating Shape Factors from Particle Sizing Data

Abstract

It is well established that particle size and shape substantially influence the bulk properties of powdered materials. Although these characteristics are closely interrelated, the tendency has been to analyse the particle size independently from particle shape. The aim of this work was the assessment of particle shape through particle sizing data. For this purpose, three different particle shape materials – glass beads (spherical), crushed glass (moderately irregular) and mica (lamellar) – were tested, employing four particle sizers. The shape factor selected was the Wadell's sphericity, which was evaluated utilizing distinct equations. The comparison of the results reveals problems arising from the use of approximations rather than more fundamental equations.

New Propellant Component, Part I. Study of 4,6-Dinitroamino-1,3,5-Triazine-2(1 H)-One (DNAM)

“…The output of the laser diffraction technique from which these are derived is based on the mean diameter of the randomly projected area instead of the maximum projected area as it is in image analysis (11) . In fact, the image analysis picture also shown in Figure 2 indicates that a particle size analysis made by this technique would appear somewhat shifted towards higher sizes.…”

Sedimentation Image Analysis (SIA) for the Simultaneous Determination of Particle Mass Density and Particle Size

“…We chose a nonrecurring manual grey scale thresholding included in the calibration of the system as automatic thresholding techniques such as clustering or interclass variance do not result in a constant threshold value over a series of images and, worse, problems in particle detection can arise as grey levels of particles of different size may vary greatly. The particle characteristics directly accessible from the individual images are the particles' projected area, the center of gravity and the circularity, which is defined as the ratio of particle perimeter to the perimeter of a circle having the same area as the particle [6]. Particles touching the image boundaries are not considered in the analysis.…”

“…Although the certificate was achieved by sieving, resulting directly in a distribution by mass, the results of sedimentation image analysis indicate good agreement, particularly when considering the fact that two techniques based on different particle characteristics are compared. Therefore, especially for non-spherical particles, slight deviations in the resulting particle size distributions are unavoidable [6] and can also be seen in the size distribution by mass in the region of about 150 mm.…”

Determination of Particle Mass Density Distribution

“…A possible reason for these deviations from the real particle mass density is the two different particle sizing techniques needed for the determination of particle mass density, as was already indicated by the error propagation analysis. As mentioned before, methods based on different particle characteristics, in this case sedimentation and laser diffraction, lead to slightly different particle size distributions [12,17]. This effect becomes stronger with increasing deviations from the spherical particle shape and has to be taken into account when natural materials are analysed as in this work.…”

“…For example, particle size distributions measured by laser diffraction are usually broader and shifted towards larger particle sizes in comparison with photosedimentation. This phenomenon is often observed for irregularly shaped natural material [12]. Consequently, the in¯uence of this effect on the determination of particle mass density also has to be studied in computational simulations in order to carry out an error propagation for individual parameters For this purpose a particle size distribution consisting of a single peak with a ®rst moment of 250 mm and a standard deviation of 20 mm is generated.…”