How Artificial Graphite Is Made
The production of artificial graphite involves heat treatment of petroleum coke. This type of product is used in refractories, steel production, lubricants, and electrodes for electrochemical cells.
There are several types of artificial graphite. The most common is called the "Acheson process" and is used to make graphite. It is based on the teachings of E.G. Acheson and has been modified since 1896.
Another method to manufacture artificial graphite is by extrusion. It is performed at a pressure of seven MPa. In this method, the binder pitch solidifies and the resulting material is then cooled. The binder usually consists of coal tar pitch or petroleum pitch.
Several additives are added during the manufacturing process. These additives have important roles in determining the quality of bulk graphite products. Some additives include wax, fatty acids, and iron compounds. They are used to reduce defects and prevent the rapid expansion of the coke.
In addition to using the Acheson method, synthetic graphite can also be produced by carbonization. Carbonization is a chemical reaction in which bulk graphite is heated in an inactive atmosphere. Complex dehydrogenation reactions take place at the same time.
Depending on the raw material and the temperature of the heat treatment, the degree of graphitisation can vary. Typically, industrially produced artificial graphite has a degree of graphitisation less than 90%.
Graphite has anisotropy. Natural flake graphite is a single crystal, whereas artificial graphite has a hexagonal basal plane structure. During the manufacturing process, the crystals can be anisotropic or isotropic.
