Particle Size: Definitions, Measurement, Distributions and Practical Uses
Particle size: meaning, common metrics (equivalent diameters, D10/D50/D90), measurement methods, size distributions, standards and applications in geology, industry, environment and health.
Overview
Particle size denotes a representative linear dimension of an individual solid particle. For irregular shapes it is usually reported as an equivalent spherical diameter that reproduces a chosen property (volume, surface area or settling behaviour). The range of interest extends from nanometres for engineered nanoparticles and ultrafine aerosols to millimetres or larger for sands and gravels. General definitions and formal terminology are available in technical references (general definitions).
Definitions and common metrics
Several metrics are used: geometric diameter, volume-equivalent diameter, surface-equivalent diameter and aerodynamic diameter. Particle size distribution (PSD) characterises the fraction of material across sizes and is commonly summarised by percentiles such as D10, D50 (median) and D90. Mean values may be number-, area-, volume- or mass-weighted; each emphasises different aspects of a sample.
Measurement methods
Measurement choice depends on size range, concentration and material state. Typical methods include:
- Sieving for coarse granular materials and powders.
- Sedimentation and hydrometer techniques that infer size from settling behaviour.
- Laser diffraction and optical particle counters that estimate distributions by scattering or counting.
- Dynamic light scattering (DLS), electron microscopy and atomic-force microscopy for fine nanoparticles, offering mean sizes and images.
- Electrical sensing (Coulter principle) and aerodynamic sizing for aerosols and polydisperse flows.
Particle size distributions and statistics
Distributions may be unimodal or multimodal and are often approximately log-normal. Reporting should state whether the distribution is presented by number, surface, volume or mass and include sample preparation details. Percentiles, span and standard deviation are typical descriptors used to characterise breadth and central tendency.
Standards, reporting and preparation
Standards from national and international organisations guide test procedures, instrument calibration and reporting conventions. Important reporting elements include measurement method, dispersion medium (wet or dry), pre-treatment to break agglomerates, and the weighting basis of the distribution; these affect comparability between datasets.
Applications and practical importance
Particle size controls bulk properties such as flowability, packing density, surface area, reactivity and optical behaviour. In geology and sedimentology it informs transport and depositional processes; in industry it affects milling, blending, filtration, catalysis and drug delivery. For airborne particles, aerodynamic diameter determines deposition in the respiratory tract and is central to exposure assessment and regulatory limits.
Notes and distinctions
Size is only one attribute: shape, porosity, surface chemistry and density also influence performance. Agglomeration state can change apparent size; therefore measurement and interpretation must consider the intended application and conditions under which the particles will be used or encountered.
Questions and answers
Q: What is particle size (general)?
A: Particle size (general) is a term used to describe the overall notion of particle size.
Q: What does particle size (grain size) refer to?
A: Particle size (grain size) refers to specific details regarding the particle sizes of soils, powders, gravel, etc.
Q: What is included in the concept of particle size distribution?
A: Particle size distribution includes information about the range and relative proportions of different particles within a given sample.
Q: How can one measure particle sizes?
A: Particle sizes can be measured using various methods such as sieving, sedimentation analysis, laser diffraction, or imaging techniques.
Q: What types of materials are typically studied with regards to their particle sizes?
A: Materials such as soils, powders, gravels, and other granular materials are often studied with regards to their particle sizes.
Q: Are there any applications for studying the concept of particle size? A: Yes, understanding and measuring the concept of particle size has many practical applications in fields such as engineering and medicine.
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AlegsaOnline.com Particle Size: Definitions, Measurement, Distributions and Practical Uses Leandro Alegsa
URL: https://en.alegsaonline.com/art/74836