Agglomeration and distribution of nanoparticles
One can classify the agglomeration nanoparticles in two ways: soft or hard. Most of the soft agglomeration occurs due to electrostatic interactions between particles, as well as van der Waals forces. The weak force allows soft agglomeration to pass certain chemical tests.
Use of mechanical energy, or the law, to exterminate; formation of hard aggregates. In addition to the van der Waals and electrostatic forces, there is also chemical bonding. Therefore, hard agglomerates, while not simple to defeat, require special control methods.
Schematic diagram showing the aggregate of nanoparticles
The van der Waals effect or interaction between the groups is one of the ways to prevent nanoparticles from forming hard-block precipitates. It allows the primary particles not to agglomerate to create secondary particles. This causes the formation of hard-blocked precipitates with high densities. The anti-agglomeration mechanism is broken down into the following: (1) electrostatic stabilizement (DLVO theory);(2) steric stabilitization; and (3) electrostatic steric staining.
By adjusting pH to form an electric double layers, the electrostatic stabilize mechanism is also known as electric double level stabilization. Repulsive forces in between the electric double layer reduces the attraction between particles and allows the nanoparticles to disperse. The diagram below shows how the mechanism works.
Steric stabilization works by adding uncharged polymers to the suspension. The particles are absorbed around them to create microcell states, which results in repulsion. Figure 4.
The Electrostatic stability mechanism is a combination the two. That is, it involves the addition of a specific amount of polyelectrolyte into the suspension to adsorb that polyelectrolyte at the particle’s surface.
The pH value of polyelectrolyte is maximized to increase the dissociation rate of polyelectrolyte. Thus, when the polyelectrolyte surface of the particle reaches saturated absorption, both work in concert to uniformly disperse these nanoparticles. Figure 3.
Nanoparticle dispersion method
The stage of nanoparticles dispersing in liquid medium usually consists of three phases: 1) liquid wetting and 2) dispersing larger particles into smaller ones by an external force. 3) stabilizing dispersed powder particles. This will ensure that all particles remain evenly dispersed in the liquid for long periods of time, so they don’t re-aggregate. It is possible to divide it according to the different dispersion mechanisms into surface modification method and mechanical action method.
Mechanical action methods refer to the use or combination of instruments and equipment in order to increase dispersion stability. They include mechanical stirring, ultrasonic and high-energy dispersion. To ensure that nanoparticles are evenly distributed within the medium, mechanical agitation dipersion can be described as a straightforward physical dispersion. This method uses only mechanical energy like external shear or impact force. Ultrasonic dipersion occurs when ultrasonic cavitation generates a micro-jet and local high temperature and high pressure. The shock wave can weaken the nano-action between the nanoparticles.
Inorganic substances modify the surface of nanoparticles
Inorganic substances are uniformly applied to the nanoparticles’ surface. To decrease their activity and stabilize inner nanoparticles, the active group of the hydroxyl is shielded. Because the chemical reaction between inorganic and surface matter is not easy, the modified and the nanoparticle depend on either physical force or van der waals force.
Inorganic nanoparticles can be organically coated by using functional groups within organic molecules. The coating allows for the surface to be chemically modified or to absorb the functional groups.
This edge discipline is related to many others, including organic and colloidal chemical chemistry as well as modern instrument analysis. A surface coating modification technique has been extensively used in the area of surface modification for nanometers. Additionally, the research results indicate that there are good opportunities to develop this technology. But, there are many issues with the modification procedure, modification equipment, or modification effect characterization. There are many instances when the problem cannot yet be fully solved. Further research is therefore urgently necessary. A nano surface modification technique is an essential tool to generate new materials. Research and development in nano-particles is ongoing. Further exploration into the surface modification of nanopowders will be a key part of the future of nanotechnology. The economic and other benefits.
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