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Graphene dispersion
The purpose of graphene dispersion is to achieve immiscible dispersion, and its particles must be crushed and mixed strongly, which means that the formation of a new surface must overcome the resistance of surface tension to achieve. With the continuous development of technology, the problem of agglomeration has become a bottleneck for the continued development of graphene. Therefore, improving the dispersion of graphene has become an indispensable technical method to improve the quality, performance and process efficiency of products (materials).
Graphene is insoluble with many substances due to its surface inertness and has poor dispersibility. There are two ways to solve the bottleneck problem in the development of graphene: one is the large-scale production of low-cost and high-quality graphene raw materials; the other is the commercialization of graphene application. In the past two years, graphene has entered the stage of industrial application, and the upstream and downstream interactions of the industrial chain are crucial. We must carry out secondary development for users to solve common technical problems such as dispersion and molding, so that graphene is more "earthly".
Graphene powder has the characteristics of fine particle size, large specific surface area, high surface energy, increased surface atomic number and insufficient atomic coordination, which makes these surface atoms have high activity, extremely unstable, and are easy to agglomerate to form a number of links. The size of the interface is larger agglomerates. The agglomeration of powder is generally divided into soft agglomeration and hard agglomeration. The formation of agglomerates makes the nanoparticles cannot be uniformly dispersed in a single particle, and cannot exert their due nano characteristics, which has a very adverse effect on the application performance of the nano powder.
Application of Ultrasonic Graphene Disperser
(1) Ultrasonic graphene dispersion machine
The core content of the ultrasonic graphene disperser is how to solve the problem of particle agglomeration. Graphene is insoluble with many substances due to its surface inertness and has poor dispersibility. It is very difficult to obtain individual dispersed particles. How to uniformly disperse the particles into the matrix is the key technology of graphene dispersion technology.
(2) How to use an ultrasonic disperser to disperse graphene
Ultrasonic graphene disperser uses ultrasonic cavitation to disperse agglomerated particles. It is to put the particle suspension (liquid) to be processed into a super-strong sound field and process it with an appropriate ultrasonic amplitude. Due to the inherent characteristics of agglomeration of powder particles, for some powders that are not well dispersed in the medium, an appropriate amount of dispersant can be added to maintain a stable dispersion state, which can generally reach tens of nanometers or even smaller. This product is especially effective for dispersing nanomaterials (such as carbon nanotubes, graphene, silica, etc.).
Parameter
Introduction:
Ultrasound is an elastic mechanical vibration wave, which is
fundamentally different from electromagnetic waves. Because
electromagnetic waves propagate in a vacuum, and ultrasonic waves
must propagate in the medium, the entire process of expansion and
compression occurs when passing through the medium.
In liquids, a negative pressure is created during the expansion
process. If the ultrasonic energy is strong enough, the expansion
process can create bubbles in the liquid or tear the liquid into
small cavities. These cavities are closed instantaneously, and an
instantaneous pressure of up to 3000 MPa is generated when the
cavity is closed, which is called cavitation. The entire process is
completed in 400 μs.
Cavitation refines substances and makes emulsions, accelerates
target ingredients into solvents, and improves extraction rates. In
addition to cavitation, many secondary effects of ultrasound are
also conducive to the transfer and extraction of target components.
The significance of cavitation is the reaction that occurs when a
bubble bursts. At some points, the bubbles no longer absorb the
ultrasonic energy, and implosion occurs. Gases and vapors in
bubbles or cavities are rapidly adiabaticly compressed, resulting
in extremely high temperatures and pressures.
The volume of the bubble is extremely small compared to the total
volume of the liquid, so the heat generated is instantly
dissipated, and it will not have a significant impact on
environmental conditions. The cooling rate after the collapse of
the cavity is estimated to be about 1010 ° C / s.
Ultrasonic holes provide a unique interaction between energy and
matter. The resulting high temperature and pressure can lead to the
formation of free radicals and other components.
In a pure liquid, when a hole is broken, it always remains
spherical due to the same surrounding conditions; however, close to
the solid boundary, the breakage of the hole is non-uniform.
Kinetic energy, which moves in the bubble and penetrates the bubble
wall.
The impact force of the jet on the solid surface is very strong,
which can cause great damage to the impact area, resulting in a
highly active fresh surface. The impact force produced by the burst
bubble deformation on the surface is several times greater than the
impact force generated by the bubble resonance.
The above-mentioned effect of ultrasonic waves is very effective in
extracting various target components from different types of
samples.
The high temperature and pressure generated on the contact surface
between the organic solvent and the solid substrate by applying
ultrasonic waves, plus the oxidizing energy of the free radicals
generated by ultrasonic decomposition, etc., thereby providing high
extraction energy.
Application:
(1) Compared with conventional extraction methods, ultrasonic
extraction technology has high extraction efficiency and short
extraction time;
(2) Ultrasonic extraction is not easily limited by the use of
solvents, allowing the addition of co-extractants to further
increase the polarity of the liquid phase and improve the
extraction efficiency;
(3) Compared with supercritical CO2 extraction and ultrahigh
pressure extraction, the ultrasonic extraction equipment is simple
and the extraction cost is low;
(4) In most cases, the ultrasonic extraction operation has few
steps, the extraction process is simple, it is not easy to cause
pollution to the extract, and the extraction temperature is low,
which is suitable for the extraction of heat-sensitive target
components.