The formation of graphite (A, D, E, B and coral-like)
Graphite is a form of carbon, which has been existent since the Carboniferous era, over 290 million years ago. Graphite was first discovered in 1564 in the form of black graphite. It has several unique properties that make it suitable for many uses, including its ability to conduct electricity and act as a lubricant.
At its highest level of order, graphite is composed of planes of carbon atoms in a hexagonal lattice (hexagonal structure). Depending upon the degree of order of the graphite, A, D, E, and B type graphite can be classified. Of the four types of graphite A type is the least ordered, and B type is the most ordered.
A type graphite is the least ordered form of graphite, a combination of highly disordered, randomly-oriented layers of graphite. It is formed when the reaction between two graphite sheets is not completed. The individual layers are strongly bound to each other due to the presence of randomly-bonded atoms in the middle. This type of graphite has very low strength, is brittle and prone to breakage compared to the other types of graphite.
D type graphite is the most commonly found form of graphite. It is composed of stacks of ordered graphene sheets in a closely packed hexagonal arrangement. These graphite planes are highly ordered and quasi-periodic in nature with high strength and low porosity. As a result, D type graphite has greater resistance to compression, higher crystalline perfection and greater strength than A type graphite.
E type graphite is a complex mineral structure formed when two graphite planes are joined together by intercalation of atoms that form a randomly arranged lattice. This lattice structure however, appears ordered and gives the mineral great strength and better resistance to compression than A and B type graphite.
B type graphite is the most ordered form of graphite and is also the rarest. It is composed of ordered graphene layers of uniform hexagonal arrangement and is typically formed when A type graphite undergoes a high temperature annealing process in the presence of oxygen. B Graphite has the highest crystalline perfection and strength of any type of graphite.
Finally, coral-like graphite is the most porous form of graphite. It is composed of very small, highly-porous flakes of randomly arranged graphite particles. This type of graphite is formed when larger graphite flakes are crushed into very small particles, resulting in a high porosity structure. The porosity of coral-like graphite can be as low as 10%, but can be as high as 25%. Due to its porosity, this type of graphite has suitable properties for a wide range of applications including lithium-ion batteries, catalytic converters and fuel cells.
In conclusion, graphite comes in a variety of forms with different levels of order. A type graphite is the least ordered form and B type graphite is the most ordered form. In addition, coral-like graphite is the form of graphite that is most porous. Each form of graphite has its own unique properties, making it suitable for different applications.
