In order to obtain the correct data of the primary particle size, it is often necessary to open the agglomerated particles in the particle size test to form a particle monomer and keep it uniformly dispersed in the medium. This operation is called "dispersion". The requirement of the laser particle size analyzer for the dispersion system is "dispersion without segregation".

Dispersion techniques and methods that can be used for ultrafine particles in liquid media include:

1. Ultrasonic dispersion. Use the cavitation effect of ultrasonic waves in the liquid to deaggregate the agglomerates;

2. Mechanical stirring and dispersing. Use the mechanical action of the blade rotation to disintegrate the agglomerated particles and distribute the particles uniformly in the liquid;
Mechanical dispersion is the use of mechanical force to break the particle agglomeration, which is the most widely used ultrafine powder dispersion method. A necessary condition for mechanical dispersion is that the mechanical force should be greater than the adhesion between the particles.

3. Add dispersant. Some samples need to be chemically dispersed, adding an appropriate amount of dispersant to improve the electrical properties of the particle surface to maintain the dispersed state;

4. Surface pretreatment. Some samples are incompatible with the medium and appear to float on the water surface, so a small amount of ethanol or other surface treatment agents need to be added for pretreatment before entering the water to make them easy to disperse in water.

Before dispersing ultrafine particles, it is necessary to understand its characteristics. The particles that have undergone surface coating and modification treatment should be carefully dispersed with ultrasonic waves; materials that are required to observe the original natural state should not be dispersed; those that record crystallization or other chemical reaction processes should not be dispersed. For the dispersion of nano gold powder, in addition to adding dispersant, high-speed stirring and ultrasonic waves should be used comprehensively to achieve good dispersion effect. The same is true for the dispersion of nano silver powder. Failure to use appropriate dispersion methods will lead to poor dispersion. For example, when adding dispersant water, detergent or PVP can be used, and the dosage is generally 1-2%wt. In ethanol, PVP or oleic acid can be used. 1-2%wt, and mix with a high-speed emulsifying disperser for half an hour.