Agglomeration nanoparticles
The agglomeration between nanoparticles falls into two main categories: Soft agglomeration or Hard agglomeration. The van der Waals forces and electrostatic force are the primary causes of soft-agglomeration. Soft agglomeration passes some chemical tests due to the weak force.<br />
It is not easy to eliminate hard agglomerates due to the chemical bonds and electrostatic forces.<br />

Diagrammatic representation of the agglomeration and nanoparticles

Dispersion nanoparticles
In order to avoid the formation of hard-block, high-density nanoparticles, one method is to reduce the interaction between groups or van der waals attraction. This way, the primary particles will not be easily agglomerated into secondary particles. This leads to the formation high-density hard-blocked particles. The antiagglomeration of nanoparticles can be divided into three parts: (1) electrostatic (DLVO) stabilization; (2) steric stabilisation; and (3) electrostatic steric steric steric steric stable.

The theory of nanoparticles dispersion
Electrostatic stabilization mechanisms (DLVO theory).
The electrostatic stabilizer, or electric double layer stabilization device, forms a double electric layer on the particle surface by adjusting the pH. The electric double layer repellence reduces the attraction between the particles and allows for dispersion. The mechanism shown in Figure 2 is the same.<br />

The steric stabilizer mechanism involves adding a certain amount to the suspension of a polymer compound that is not charged to adsorb around the nanoparticles and form a state of microcells. This causes repulsion, and thus achieves the dispersion goal. The mechanism diagram can be seen in Figure 4.

The Electrostatic Stabilization Mechanism is a combination from the two previous mechanisms. It involves adding a polyelectrolyte solution to the suspension, which adsorbs the polyelectrolyte onto the particle surface.<br />
The dissociation of the polyelectrolyte is maximized when the pH of the polyelectrolyte is high. This allows the polyelectrolyte at the particle surface to reach saturated adsorption. Figure 3 illustrates the mechanism diagram.<br />

Nanoparticle dispersion method

The dispersion process of nanoparticles usually consists of three stages. According to the different mechanisms of dispersion, it is divided into mechanical actions method and surface modification methods.

The mechanical action method is the use of instruments and equipment in order to increase the stability of the dispersion of the nanoparticles into the solvent. It includes the mechanical stirring method, the ultrasonic dispersion and the high energy treatment methods. Mechanical agitation, also known as mechanical dispersion, is a simple, physical method of dispersion. It uses external forces such as shear and impact to ensure that nanoparticles disperse well in the medium. Ultrasonic Dispersion is local high temperature or high pressure shock wave and microjet generated by ultrasonic agitation. It can weaken the nanoaction energy and effectively prevent nanoparticles agglomerating.

The surface of nanoparticles is uniformly covered with an inorganic material. The active hydroxyl groups on the surface are coated or shielded, which reduces the activity of nanoparticles and stabilizes the inner nanoparticle. Inorganic matter, the surface, and the inner nanoparticle cannot be chemically reacted. Therefore, the inorganic substance, which is used as a precipitation agent on the surface, relies on physical or van Der Waals forces.

The organic coating is a method of using functional groups from organic molecules to coat or adsorb the surface particles of inorganic particles.<br />

The surface modification of nanoparticles can be a cutting-edge discipline that is closely linked to other disciplines. These include colloidal and organic chemistry as well as crystallography, nanomaterials and modern instrument testing. Surface coating modification has been widely applied in surface modification. The research results show that this technology has good growth prospects. Modification mechanisms, methods and equipment for modification and characterization of modification effects are not perfect. Many times the problem can’t be solved in a fundamental way, so further research is required. Nano surface modification is regarded as a way to create new materials for the future due to its significant impact on the chemical and physical properties of surface-treated particles. The nanotechnology is a powerful tool that will be used in many fields. Benefits, both economic and social.<br />
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