Nanoparticles have a special surface structure, which lacks adjacent coordinating atoms on the surface, and has high activity, so it is easy to agglomerate. Due to the strong self-absorption property among nanomaterial particles, the agglomeration of nanoparticles is inevitable. Aggregates can be divided into two types: hard agglomerates and soft agglomerates. The formation process of agglomerates reduces the energy of the system.


Soft agglomeration: A type of interparticle aggregation caused by van der Waals forces. Soft agglomerates can be redispersed mechanically. Mechanical dispersion is the use of mechanical force to break up particle agglomerations. The necessary condition for mechanical dispersion is that the mechanical force (usually refers to the shear force of the fluid and the differential pressure force) should be greater than the adhesion force between the particles. The realization of mechanical dispersion is easier, but it is a mandatory dispersion. Although the bonded particles can be broken by mechanical force, the force between them still exists, and they may re-agglomerate after the treatment process is completed. Therefore, adding follow-up work and using in conjunction with other methods can make the process of this method more perfect. At present, this method is mostly used to prevent the formation of soft agglomerates between particles and to eliminate the soft agglomerates that have already formed.

Hard agglomeration: In addition to electrostatic force and van der Waals force, there are also chemical bonds, so hard agglomeration is not easy to destroy, and some special measures need to be taken to control and disperse. Nanoparticles can be surface modified to prevent hard agglomeration, and storage method is also an important factor. Some nanoparticles can be coated with SiO2, PVP, PEG and other polymers to form a core-shell structure, which is not easy to agglomerate. Nano-precious metal particles can be modified with citric acid, so that the surface of the nanoparticles has negatively charged citrate ions, and the electrostatic repulsion between the particles makes the nanoparticles stable and not agglomerated, such as the nano-gold powder produced by SAT NANO, and the nano-palladium powder. Can be treated with citric acid.


In order to ensure good dispersion of the nanoparticles in the liquid medium, appropriate dispersants can be added. Commonly used dispersants are:

1. Inorganic electrolyte. For example, sodium polyphosphate, sodium silicate, sodium hydroxide and soda. The function of such dispersants is to increase the absolute value of the surface potential of the particles, thereby producing a strong electrostatic repulsion of the electric double layer, and at the same time, the adsorption layer can also produce a strong steric repulsion, which can effectively prevent the agglomeration of the particles.

2. Organic polymers. Commonly used are polyacrylamide series, polyethylene oxide series and natural polymers such as tannin and lignin. Such dispersants mainly form an adsorption film on the surface of the particles to produce a strong steric repulsion effect, so obtaining a dense adsorption film with a certain strength and thickness is the premise of good dispersion. The organic polymer type dispersant can be used in water or in organic medium depending on its characteristics.

3. Surfactants, including anionic, cationic and nonionic surfactants. Such dispersants can form a molecular film on the surface of the particles to hinder the mutual contact between the particles, and can reduce the surface tension, reduce the capillary adsorption force and produce steric hindrance effects. The dispersing effect of surfactants is mainly manifested in the adjustment of the wettability of the particle surface.


Although nanoparticles are easy to agglomerate, as long as the agglomeration mechanism is different, the agglomeration can be controlled by using the corresponding dispersion technology. SAT NANO can customize products with special specifications according to the special needs and parameters of customers. For the better application of customers, we continue to explore and experiment in the fields of nano-powder surface modification and dispersion to provide customers with more complete consulting services and Technical Support. Welcome to consult and negotiate!