Meaning
International standard providing the methodology and validation requirements for the measurement of particle size distributions using laser diffraction techniques. Adoption of iso 13320 ensures that laboratories across the globe produce comparable data when evaluating the grain size of battery cathode precursors or metal powders. This document defines the mathematical models used to translate light scattering patterns into volume-based distributions.
It establishes the limits for repeatability and reproducibility that a testing facility must meet to maintain certification.
Mathematical Model
Calculation of particle diameters relies on the mie theory of light scattering which accounts for the refractive index of both the material and the surrounding medium. When following iso 13320, technicians must provide accurate optical constants to the software to avoid errors in the sub-micron range. The standard allows for the fraunhofer approximation only when the particles are much larger than the wavelength of the laser light.
This distinction ensures that the fine fractions of a powder are not underestimated during the analysis. Modern instruments integrate these calculations into automated software packages that provide the final distribution curve.
Validation Protocol
Verification of instrument performance requires the periodic measurement of certified reference materials with a known size distribution. Adhering to iso 13320 means that the measured mean value must fall within a narrow percentage of the certified value of the standard. If the results are outside these bounds, the optical system may be misaligned or the light source might be losing intensity.
Detailed logs of these validation runs provide the audit trail necessary for quality management systems in high-tech manufacturing. This rigorous checking ensures that the data used for purchasing decisions is technically defensible.
Sample Dispersion
Dispersion techniques are critical because particles often stick together and appear as larger objects to the laser beam. The guidelines in iso 13320 suggest using ultrasonic energy or high-pressure air to break up these clusters without damaging the individual grains. Proper dispersion ensures that the measured distribution reflects the true size of the primary particles rather than the state of agglomeration.
This step is particularly important for cohesive materials like graphite or lithium carbonate which tend to form stable clumps. If the energy applied is too low, the coarse tail of the distribution will be exaggerated. Conversely, excessive energy can mill the material and create a false fine fraction.
Technicians must find a stable balance where the size profile does not change with further increases in dispersion energy. Accurate reporting of these settings is required for data transparency.
