The size of a particle is referred to as “grain size” (also known as “particle size” or “diameter”). When a certain physical property or behavior of a particle most closely resembles that of a homogeneous sphere (or a combination of spheres) with a specific diameter, the diameter (or combination) of that sphere is taken as the equivalent particle size (or particle size distribution) of the measured particle. Naturally, for non-spherical particles, the particle size depends on the measurement reference and statistical method, and the size can only be considered “equivalent.”

The percentage (or cumulative percentage) of particles within different size intervals in a powder is called the frequency size distribution (or cumulative size distribution). The vertical axis represents the composition of particle sizes calculated based on different references, which can be expressed as a percentage or cumulative percentage of the number, length, area, or volume. The horizontal axis represents particle size values calculated using the same reference.

Parameters such as D10, D50, and D90 are commonly used to reflect the uniformity of a powder, and they are also known as cumulative distribution metrics:

• D50: Also called the median particle size, it refers to the particle size at which the cumulative distribution percentage reaches 50%. This value divides the total particle population into two equal halves: 50% of the particles have a size larger than this value, and 50% are smaller. For example, if a sample has a D50 of 5 μm, it means that 50% of the particles in the sample have a size greater than 5 μm, and 50% have a size smaller than 5 μm. D50 is often used to represent the average particle size of a powder.

• D90: This refers to the particle size at which the cumulative distribution percentage reaches 90%, meaning that 90% of the particles in the powder have a size smaller than this value. It is commonly used to indicate the coarser end of the particle size spectrum, making it a key indicator in powder production and application. In some industries, D95 or D97 values may be used, which have similar meanings to D90.

• D10: This represents the particle size below which 10% of the particles are found, essentially the opposite of D90.

These three parameters are highly significant in production and everyday applications. For instance, in the pharmaceutical industry, understanding the particle size distribution of a drug can provide insights into its efficacy and side effects. Similarly, in environmental monitoring, particle size distribution is an important indicator for air and water quality.

In summary, D10, D50, and D90 are critical parameters in particle size distribution, representing the particle size distribution in different ranges. Fine particulate materials are widely used in daily life and industrial production, where their size and distribution directly impact industrial processes, product quality, energy consumption, and production safety. Therefore, accurate and convenient measurement of particle sizes and determination of the particle size distribution function is of great significance.