Question 6.Introduction of graphite materials

Graphite is an allotrope of carbon element, the crystal of carbon element. According to different crystal degrees, graphite is divided into crystalline (flake) graphite and cryptocrystalline (earthy) graphite. Crystal graphite is divided into block graphite and crystal flake graphite. According to crystal size, crystalline graphite is divided into large-flake, medium-flake, and small-flake graphite.

Graphite mineral belongs to hexagon crystal, with a layered structure and special atomic structure. So graphite has a series of special qualities. The bigger crystal is, the more complete structure is, the clearer quality is. The specific qualities are as follows:

1.High-temperature resistance

Graphite is one of the highest temperature resistant materials. It can bear 3800, the highest temperature. Even under super high temperatures, graphite hardly loses its weight. Under 2000, the strength of graphite will be increased 1 time.

2.Electric and thermal conductivity

Graphite is 1 time higher than general nonmetallic metals in electric conductivity. The thermal conductivity is higher than iron, lead, and other metals. And, as the temperature increases, its thermal conductive coefficient will drop. Under extremely high temperatures, graphite is in an insulation status. Then, under super high-temperature conditions, the thermal insulation property of graphite is reliable.

3.Lubricity.

Graphite, as a special lubricating material, has excellent lubricating property. With a change of graphite flake sizes, graphite’s lubricity will change. The bigger the flake is, the friction coefficient is lower, better lubricity is.

4.Special property for resistance against heat and shock.

Graphite may bear huge thermal variation at a very high temperature without breaking the structure. There is no big change in volume and no cracks.

5.Chemical stability

Graphite has good chemical stability at normal temperatures, resistant to organic solvent and acid corrosion.

6.Plasticity

Graphite has slices that are breathable and transparent. It is naturally hydrophobic. The high strength graphite has great strength, even difficult to process with a diamond cutter.