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Introduction to the commonly used dispersion and stripping method for graphene

Issuing time:2018-12-10 Popularity:789

I. overview of graphene

Graphene (Graphene) is a kind of hexagonal planar film with honeycomb lattice composed of carbon atoms and sp2 hybrid orbitals. It is a two-dimensional material with only one carbon atom thickness. Graphene is now the world's thinest and hardest nanomaterial, almost entirely transparent, absorbing just 2.3% of light. Coefficient of thermal conductivity is as high as 5300 w/m, higher than that of carbon nanotubes and the diamond, room temperature the electron mobility, more than 15000 cm2 / Vs, and higher than carbon nanotubes or silicon crystal, and the resistance rate is only about 10-8 Ω/m, are lower than those of copper or silver, for minimum resistivity materials in the world.

II. Method of graphene stripping

1. Mechanical stripping method

On-line ultra-high speed high shear homogenizer (including Shanghai ou river ODG series of ultra-high speed grinding shear emulsifying machine) stripping preparation of graphene is the energy generated by high speed rotating the graphite materials are strong mechanical and hydraulic shear, high-speed impact stripping, centrifugal extrusion pressure, the liquid layer friction and corrosion by combination of the graphite crystal horizontal dislocation and sliding between layer and layer, and then spin out the graphite rapid, after high frequency cycles, finally be stable graphene. In the process of dispersion preparation, linear velocity, shear force and angular velocity are important factors affecting the stripping results. ODG series adopts unique grinding working shear head (intermittent adjustable), with a maximum rotation speed of 15000rpm and a linear velocity of over 50m/s, which is the first choice for glass graphene.

Video (high viscosity during dispersion)

2. Chemical vapor deposition (CVD)

3. Oxidation-reduction method

Oxidation-reduction method is to react natural graphite with strong acids and strong oxidizing substances to form graphite oxide (GO). After ultrasonic dispersion, GO is prepared. After adding reducing agent to remove oxygen-containing groups on the surface of graphite oxide, graphene is obtained. Due to its low cost and easy implementation, the oxidation-reduction method has become the most mainstream method to produce graphene. However, the waste liquid produced by this method is quite serious for environmental pollution. The graphene prepared is generally multilayer graphene or graphite microcrystalline rather than strictly graphene, and the product has defects that lead to partial loss of electrical and mechanical properties of graphene.

4. Solvent stripping method

The principle of solvent stripping method is to disperse a small amount of graphite in the solvent to form a low concentration of dispersion liquid. Ultrasonic wave is used to destroy the van der Waals force between the graphite layers. The solvent is inserted into the graphite layers to conduct layer by layer stripping to prepare graphene. This method does not destroy the structure of graphene like the oxidation-reduction method, and can produce high quality graphene. The disadvantages are high cost and low yield, which makes industrial production more difficult. Of course, the preparation methods of graphene include solvent-thermal method, high-temperature reduction, photoreduction, epitaxial crystal growth method, microwave method, arc method and electrochemical method, which are not as common as the above four methods. Don't get confused!!! RGO, or RGO. In general, go is made from graphite oxidized by strong acids and then reduced by chemical or thermal shock.

So that's what we're going to share, and I hope it's helpful.

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