The concept of particle size distribution

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Particle size distribution is a general term used to describe the state of particle size distribution, and it usually refers to the proportion of particles with a specific particle size or within a certain particle size range in the entire powder mass. As a powder in a polydisperse system, the size of its particles follows statistical laws. For a particular particle, its particle size takes random values within a certain range, making it a random variable. However, for the entire powder mixture, the proportion of particles with a specific particle size or within a certain size range remains constant. Therefore, particle size distribution can be measured using sampling analysis methods, and statistical concepts such as the probability density function and probability distribution function are used to represent it; these are correspondingly referred to as frequency distribution and cumulative distribution. The particle size distribution can use one of four parameters as a basis: count, length, area, or volume (or mass). A particle size distribution based on count refers to the proportion of particles of a certain size or within a certain size range among the total number of powder particles, while a particle size distribution based on mass indicates the proportion of the mass of particles of a certain size or within a certain size range compared to the total mass of the material. Particle size distributions based on length and area can be defined in a corresponding manner. The basis for the particle size distribution depends on the method used to determine it; for example, when the particle size distribution is measured using microscopy, a count-based approach is commonly used, while a mass-based approach is typically employed when sedimentation is used for measurement. In engineering, quality benchmarks are used the most, while length benchmarks and area benchmarks are used very rarely. The particle size distribution of powders is usually obtained through experimental methods. The measured data can be organized in tables, plotted as curves, or expressed in the form of appropriate functions.