Causes for Agglomeration of Micro Powder

Author : Clirik

The dispersion of powder is undoubtedly the most important technology in the micro powder technology. Classification, particle size measurement, mixing and storage and transportation, and so on, are largely determined by the degree of dispersion of particles.

1.1 intermolecular forces cause aggregation of particles

It is well known that there is always a van Edward's attraction among the molecules, which is a short-range force. However, for the system composed of a large number of molecular aggregates, there are interactions between multiple molecules, the effective distance between the particle molecular force can reach 50nm, which belongs to the long range force. The fundamental reason of the particle aggregation is the molecular force between the micro powder.

micro powder

1.2 Electrostatic force between particles causes aggregation

In dry air, most of the micro powder particles are naturally charged. The maximum amount of charge limited breakdown strength of particles obtained from the surrounding medium, in dry air is about 1.7 x 10 m e / crn2. When the charged particles are in contact with other objects, the charge on the surface of the particles is equal to the different charge of the other side, which causes the residual charge on the surface of the object to generate the contact potential difference.

micro powder

1.3 Micro powder bonding of particles in wet air

When the relative humidity of the air is more than 65%, the water vapor begins to condense on the surface of the particles and the particles, and the particles form a liquid bridge, which greatly increases the bond strength. The adhesion force of liquid bridge is mainly caused by capillary pressure and surface tension on the surface of liquid bridge.

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