Particle size
Granulometry | |
---|---|
Basic concepts | |
Particle size, Grain size, Size distribution, Morphology | |
Methods and techniques | |
Mesh scale, Optical granulometry, Sieve analysis, Soil gradation | |
Related concepts | |
Granulation, Granular material, Mineral dust, Pattern recognition, Dynamic light scattering | |
Particle size is a notion introduced for comparing dimensions of solid particles (flecks), liquid particles (droplets), or gaseous particles (bubbles). The notion of particle size applies to particles in colloids, in ecology, in granular material (whether airborne or not), and to particles that form a granular material (see also grain size).
Measurement
There are several methods for measuring particle size
Machine learning algorithms are used to increase the performance of particle size measurement.[4][5] This line of research can yield low-cost and real time particle size analysis.
In all methods the size is an indirect measure, obtained by a model that transforms, in abstract way, the real particle shape into a simple and standardized shape, like a sphere (the most usual) or a cuboid (when minimum bounding box is used), where the size parameter (ex. diameter of sphere) makes sense. Exception is the mathematical morphology approach, where no shape hypothesis is necessary.
Definition of the particle size for an ensemble (collection) of particles presents another problem. Real systems are practically always
Expressions for sphere size
The particle size of a
- Volume-based particle size
- Volume-based particle size equals the diameter of the sphere that has the same volume as a given particle. Typically used in sieve analysis, as shape hypothesis (sieve's mesh size as the sphere diameter).
- where
- : diameter of representative sphere
- : volume of particle
- Area-based particle size
- Area-based particle size equals the diameter of the sphere that has the same surface area as a given particle. Typically used in optical granulometry techniques.
- where
- : diameter of representative sphere
- : surface area of particle
Indirect measure expressions
In some measures the size (a length dimension in the expression) can't be obtained, only calculated as a function of another dimensions and parameters. Illustrating below by the main cases.
- Weight-based (spheroidal) particle size
- Weight-based particle size equals the diameter of the sphere that has the same weight as a given particle. Useful as hypothesis in centrifugation and decantation, or when the number of particles can be estimated (to obtain average particle's weight as sample weight divided by the number of particles in the sample). This formula is only valid when all particles have the same density.
- where
- : diameter of representative sphere
- : weight of particle
- : density of particle
- : gravitational constant
- Aerodynamic particle size
- aerodynamic particle size equals the diameter of the sphere that has the same drag coefficientas a given particle.
- Another complexity in defining particle size in a fluid medium appears for particles with sizes below a interface layer becomes comparable with the particle size. As a result, the position of the particle surface becomes uncertain. There is a convention for placing this imaginary surface at a certain position suggested by Gibbs and presented in many books on interface and colloid science.[6][7][8][9][10][2]
International conventions
There is an international standard on presenting various characteristic particle sizes, the ISO 9276 (Representation of results of particle size analysis).[11] This set of various average sizes includes median size, geometric mean size, average size. In the selection of specific small-size particles is common the use of ISO 565 and ISO 3310-1 to the choice of mesh size.
Colloidal particle
In
See also
- Dynamic light scattering
- Laser diffraction analysis
- Micromeritics
- Dispersion Technology
- Sauter mean diameter
References
- S2CID 122702316.
- ^ a b Dukhin, A. S. and Goetz, P. J. Characterization of liquids, nano- and micro- particulates and porous bodies using Ultrasound, Elsevier, 2017
ISBN 978-0-444-63908-0
- ^ "Mesoscopic Probes". SOPAT | Smart Online Particle Analysis. 2018-04-11. Retrieved 2019-06-05.
- PMID 32128161.
- ISSN 0032-5910.
- ^ Lyklema, J. “Fundamentals of Interface and Colloid Science”, vol.2, page.3.208, 1995
- ^ Hunter, R.J. "Foundations of Colloid Science", Oxford University Press, 1989
- ^ Dukhin, S.S. & Derjaguin, B.V. "Electrokinetic Phenomena", J.Willey and Sons, 1974
- ^ Russel, W.B., Saville, D.A. and Schowalter, W.R. “Colloidal Dispersions”, Cambridge University Press,1989
- ^ Kruyt, H.R. “Colloid Science”, Elsevier: Volume 1, Irreversible systems, (1952)
- ^ ISO Standard 9276 "Representation of results of particle size analysis". Reviews from 1998 to 2015.
- ISBN 0-07-231808-2.
8.ISO Standard 14644-1 Classification Airborne Particles Cleanliness