Particlesize

Particle size is a measure of the dimensions of particles within a material, typically described by a size distribution rather than a single value. A particle is often represented by an equivalent diameter, such as a volume- or area-based diameter, depending on the measurement method and application. Sizes span from nanometers to millimeters, with nanoscale particles generally defined as less than 100 nanometers and micrometer-scale particles from about 1 micrometer upward.

Size influences a range of properties and behaviors, including surface area, dissolution rate, optical and mechanical properties, rheology, filtration, sedimentation, and chemical reactivity. Applications span pharmaceuticals, paints, catalysts, ceramics, cosmetics, and environmental science. The geometry and distribution of particle sizes affect performance; broad or multimodal distributions can indicate aggregates or multiple particle populations and may require processing to achieve a desired specification.

Common sizing methods include sieve analysis for coarse powders, laser diffraction and dynamic light scattering for smaller particles, and Coulter counter techniques for suspensions. Direct imaging with electron microscopy provides morphology information. Size distributions are often summarized with percentiles such as d10, d50 (median), and d90, while d32 (Sauter mean diameter) relates to surface area to volume. The polydispersity index (PDI) assesses distribution breadth in certain techniques.

Standards and guidelines exist for particle-size analysis, detailing calibration, sample preparation, and reporting practices. Accurate sizing requires consideration of particle shape, aggregation state, refractive properties, and the specific assumptions and limitations of the chosen measurement method.