FAQ | Frequently Asked Questions

Particle Size

Particle Size

• Nano Powders

  • BET (nitrogen gas adsorption) is used to determine the specific surface area (square meters per gram). A formula is used to convert this value to an Average Particle Diameter (APD) in nanometers. APD and APS (Average Particle Size) are used interchangeably. This method gives no information about the particle size distribution (PSD).

• Nano Dispersions

  • For most dispersions the average particle size of the dry powder is used.

  • Sometimes a measurement is made in the dispersed form in order to correlate with a customer’s lab measurements on the received product or to provide information on PSD. These measurements (for example on the Horiba LA-910) can be very precise and show changes from lot to lot, but they always show a much larger absolute value even though the particles are in fact dispersed to individual particles.