Structure of Graphite and Uses

Graphite, commonly known as plumbago or black lead, is a carbon-based mineral. It is a naturally occurring, form of carbon with a hexagonal structure system. Graphite name is derived from the Greek word “graphein,” the meaning of which is “to write.” Graphite is present in igneous and metamorphic rocks. It is of greyish-black colour, which is opaque and has a lustre. It is a soft mineral and has a very low specific gravity. It is used in pencils, metallurgy, and manufacturing. Graphite forms when carbon is treated with heat and pressure on Earth’s surface. Graphite is a unique material since it has both metal and non-metal qualities.

Classification of graphite:

Graphite can be classified into two main categories:

1. Natural graphite

2. Synthetic graphite

• Natural graphite: 

Natural graphite is a mineral that is naturally formed in the Earth’s crust. It is composed of graphite carbon. This graphite is extracted from mines and if found mixed with other minerals. It requires mineral processing like flotation and filtration.

Natural graphite can be stable in a large range of temperatures and is an excellent conductor of heat and electricity. 

On the basis of crystallinity, this mineral can be divided into three categories:

• High crystalline
• Amorphous
• Flake

1. High crystalline graphite is made from crude oil reserves that must undergo a transformation into graphite due to time, pressure, and temperature.
2. Amorphous: amorphous graphite is the least quality of natural graphite. They are still crystalline. They are found in mesomorphic rocks such as slate, coal, etc. They are extracted by mining.
3. Flake graphite: they can be found in metamorphic rocks. The carbon concentration of this is 5% to 40%. They are extracted by the froth flotation process. They are found worldwide.

• Synthetic graphite:

Coke and pitch can be used to make synthetic graphite. They are less crystalline than natural graphite, but they are purer.

There are two kinds of synthetic graphite:

1. Electrographite: they are pure carbon that is produced from coal tar pitch and petroleum coke.
2. These are synthetic graphite that is produced by heating calcined petroleum pitch.

Structure of graphite:

Graphite has a covalent structure, which means that each carbon atom is joined to three other carbon atoms by covalent bonds. The carbon atoms are arranged in a hexagonal pattern, forming a sheet-like structure, and the sheets are attached to each other by weak forces.

There are multiple sheets attached to each other parallelly. In graphite, the atoms show sp2 hybridization. The individual layers of graphite are known as graphene. The carbon atoms in each layer are organised in a honeycomb lattice whose bond length is 0.142 nm and a plane separation of 0.335 nm. The distance between the layers is 2.5 the distance between the atoms of each layer.

Three of each carbon atom’s electrons are used to create simple bonds with its three closest neighbours electrons. The fourth electron remains at the bonding level. Each carbon atom’s “spare” electrons become delocalized across the entire sheet of atoms in one layer.

The structure of the graphite is shown below:

Uses and applications of graphite:

There are many uses of graphite in different sectors:

Refractory substance:

Due to its stability in high temperature and chemical inertness, graphite is used in mankind many refractory items such as refractory material and Mag-carbon refractory bricks. It is also used in making crucibles, moulds, and ladles.    

Graphite is used in the production of blast furnaces for the production of iron.

The electrodes of graphite are used in electrical metallurgical furnaces and furnaces used in the processing of steel.

Chemical Industry:

In chemical industries, graphite is used in the production of calcium carbide and phosphorus in arc furnaces. Graphite is used as an anode in electrolytic processes. 

Nuclear Industry:

Graphite is used in making moderator rods and reflector components in a nuclear reactor.

Electrical Industry:

In the manufacturing of carbon brushes and electric motors.

Mechanical uses:

Graphite material is used in engineering sectors in the making of thrust and journal bearing, piston rings, and vanes. 

Other applications of graphite:

Metallurgy

As lubricants

In the production of paints.

In the production of pencils.

Conclusion:

Graphite is a soft and naturally occurring mineral form of carbon. There are two types of graphite that are natural graphite and synthetic graphite. The graphite is of greyish black colour. It is naturally found on the crust of the earth. Graphite can be found on the earth’s above surface.  It is used in metallurgy, in the coating, in manufacturing of paints etc. The structural design of graphite is honeycomb-like which are connected to each other with strong bonds, and form sheets. Many sheets are attached by weak bonds.