Application scope of expanded graphite powder

Dilated graphite powder is a loose and porous worm like substance made from natural flake graphite, hence also known as graphite worm.

Natural flake graphite is a crystal with a layered structure, where carbon atoms in each layer form a network of planar macromolecules through strong covalent bonds, and the layers are weakly bonded by van der Waals forces. Under the action of strong oxidants, the network of planar macromolecules become positively charged planar macromolecules, causing polar sulfate molecules and negative ions such as hydrogen sulfate ions to insert into the graphite layer and form expandable graphite powder, also known as graphite intercalation compound (GIC).

Due to the formation of a unique network pore system during the puffing process, with a large specific surface area and high activity of the resulting fresh surface, it has excellent adsorption performance and other special properties, and has a wide range of applications.

The preparation methods of expanded graphite powder usually include chemical oxidation (concentrated sulfuric acid method, mixed acid method, secondary oxidation), electrochemical oxidation, gas-phase diffusion method, explosion method, etc.

1、 Properties of Expanded Graphite Powder

Soft, lightweight, porous, and with good adsorption performance.

Due to the developed voids and predominance of large pores in expanded graphite, it is prone to adsorb large molecular substances, especially non-polar ones, which are resistant to oxidation and corrosion. Except for a few strong oxidants, it can resist corrosion from almost all chemical media.

Resistant to radiation, with good electrical and thermal conductivity, self-lubricating properties, non permeability, high bottom temperature resistance, and excellent resilience.

2、 Application of Expanded Graphite Powder

(1) Environmental protection field

Expanded graphite powder has hydrophobicity and oleophilicity, and can selectively remove non-aqueous solutions in water, such as oil stains from the sea, rivers, and lakes.

Expanded graphite can form a certain winding space when absorbing oil, and can store oil substances much larger than its total pore volume.

After adsorbing a large amount of oil, it can gather into blocks and float on the liquid surface, making it easy to collect and recycle.

And the expanded graphite powder is mainly composed of pure carbon, which will not cause secondary pollution in water.

In addition, expanded graphite can also be used for removing oil from industrial wastewater emulsions and substances soluble in oil, such as pesticides, and has good adsorption effects on many other organic or inorganic harmful components.

In addition to selective adsorption in the liquid phase, expanded graphite also has a certain removal effect on the main components of atmospheric pollution such as SOx and NOx generated by industrial and automotive exhaust gases.

(2) Sealing material

Expanded graphite powder can be processed into flexible graphite for use as a sealing material.

Compared with traditional sealing materials such as asbestos, rubber, cellulose, and their composite materials, flexible graphite has a wider temperature range, lower thermal expansion coefficient, no brittleness or explosion at low temperatures, and no softening or creep at high temperatures. It is known as the king of sealing and has been widely used in industries such as petrochemicals, mechanical metallurgy, and atomic energy.

(3) Biomedical Science

Expanded graphite powder has good biocompatibility, is non-toxic, odorless, and has no side effects, making it a very important class of biomedical materials

Based on its excellent adsorption and drainage performance, breathability and permeability, small adhesion to wounds, non blackening of wounds, and adsorption inhibition of various bacteria, expanded graphite composite materials can be used as high-performance external wound dressings, replacing conventional gauze dressings and achieving good results in burn and other wounds.

(4) High energy battery materials

Adding expanded graphite powder to the zinc anode of rechargeable zinc manganese batteries can reduce polarization during zinc anode charging, enhance electrode and electrolyte conductivity, suppress dendrite formation, and provide good forming characteristics, suppress anode dissolution and deformation, and extend battery life.

In addition, lithium can form expanded graphite with graphite through gas, liquid, solid state, and lithium salt electrolysis methods. This expanded graphite has a lower electrode potential and good reversible insertion and extraction.

(5) Fire safety materials

Foreign countries have added some expandable graphite to the interlayer of cabin seats, or made it into fire-resistant sealing strips, fire-resistant blocking materials, fire-resistant rings, etc. Once a fire breaks out, it rapidly expands and blocks the path of fire spread, achieving the purpose of extinguishing the fire.

In addition, adding fine particles of expandable graphite to ordinary coatings can produce effective flame retardant and anti-static coatings.

(6) Other

Expanded graphite sheet has good electrical and thermal conductivity, with an electric thermal conversion rate of over 97%, and can generate far-infrared radiation, making it a new type of heating material.

Expanded graphite is crushed into fine powder, which has strong scattering and absorption characteristics for infrared waves, making it an excellent infrared shielding (stealth) material.

Make fireworks from expandable graphite, instantly explode to form expanded graphite, and disperse it in a predetermined airspace to form aerosol interference cloud smoke curtain agent.

In addition, expanded graphite can also be used as insulation and soundproofing materials, electromagnetic shielding components, and catalytic materials.