Do You Know Natural Graphite? Let's Introduce Something About It

  • Good high temperature resistance and thermal shock resistance.
  • Excellent resistant to acids, alkalis and organic solvent corrosion.
  • The strength increases as the temperature rises.
A pile of natural graphite powder
Description

Graphite is a crystalline form of carbon that is black to dark gray, soft and slippery. It has a distinct layered structure, with a single layer of carbon atoms bonded to three other carbon atoms through covalent bonds to form a covalent molecule. It was named by Abraham Gottlob Werner in 1789 and originated from the Greek word γράφειν. It is an allotrope of carbon.

Natural graphite is a carbonaceous crystalline mineral that is generally found in ores such as graphite schist, graphite gneiss, graphite-bearing schist, and metamorphic shale. It has two common forms: crystalline (flake graphite) and cryptocrystalline (amorphous graphite).

In addition, there is another type of graphite called vein (crystalline vein) graphite. There is some controversy about its origin, suspecting that it is a result of pyrolysis of graphite naturally occurred. In simple terms, solid graphite carbon may be deposited from a high-temperature fluid as it flows. Once the fluid cools, this graphite carbon forms graphite flows or veins in the surrounding rock. Carbon-rich gases may react with the high-temperature fluid to form deposited graphite solids, or may be absorbed as the fluid flows. It typically appears as fibrous or needle-like crystalline aggregate.

Features

The graphite structure is intermediate between atomic crystals, metallic crystals, and molecular crystals, and has a unique crystal structure, so it has some special properties.

  • High Temperature Resistance & Thermal Shock Resistance
    The graphite melting point is 3850±50 °C, and the boiling point is 425 °C. It has a small thermal expansion coefficient, in the case of sudden temperature change, the volume of graphite changes little, therefore it has good thermal shock resistance. The strength of graphite increases as the temperature rises, and at 2000 °C, the strength is doubled.
  • Electrical & Thermal Conductivity
    As each plane of carbon atoms has residual atoms, together with residual atoms on the adjacent planes, functions as electron clouds and exists between the mesh planes, making graphite have good thermal and electrical conductivity. The thermal conductivity of graphite decreases as temperature rises, and at extremely high temperatures, graphite becomes a thermal insulator.
  • Chemical Stability
    Graphite has good chemical stability at room temperature and is resistant to corrosion from acids, alkalis, and organic solvents.
  • Lubricity
    The van der Waals force between graphite layers is weak, making it lubricious. The lubricity of graphite depends on the size of the graphite flakes, the larger the flakes, the lower the friction coefficient, and the higher the lubricity.
  • Plasticity
    Graphite has good toughness and can be rolled into very thin sheets.
  • Coating Performance
    Graphite can be coated on the surface of solid materials to form a thin film, which adheres firmly and provides protection.