Graphitization
Graphitization is a process of transforming a carbonaceous material, such as coal, graphite or certain forms of iron alloys, into graphite.[1]
Process
The graphitization process involves a restructuring of the molecular structure of the carbon material. In the initial state, these materials can have an amorphous structure or a crystalline structure different from graphite. Graphitization generally occurs at high temperatures (up to 3,000 °C (5,430 °F)), and can be accelerated by catalysts such as iron or nickel.[2]
When carbonaceous material is exposed to high temperatures for an extended period of time, the carbon atoms begin to rearrange and form layered crystal planes. In the structure of graphite, carbon atoms are arranged in flat hexagonal sheets that are stacked on top of each other. These crystal planes give graphite its characteristic flake structure, giving it specific properties such as good electrical and thermal conductivity, low friction and excellent lubrication.
Interest
Graphitization can be observed in various contexts. For example, it occurs naturally during the formation of certain types of coal or graphite in the Earth's crust. It can also be artificially induced during the manufacture of specific carbon materials, such as graphite electrodes used in fuel cells, nuclear reactors or metallurgical applications.[3]
Graphitization is of particular interest in the field of metallurgy. Some iron alloys, such as cast iron, can undergo graphitization heat treatment to improve their mechanical properties and machinability. During this process, the carbon dissolved in the iron alloy matrix separates and restructures as graphite, which gives the cast iron its specific characteristics, such as improved ductility and wear resistance.
Misuse
The word graphitization is often misused to describe the creation of layered, turbostratic carbon structures usually only a few to several layers thick. The correct term for this is graphenization or the formation of graphene layer(s) that stack to form a multilayered graphenic structure. The term is so misused that materials are often claimed to be graphite when in fact they are not. Graphitization refers to the formation of large crystalline graphite.
Notes and references
- ^ "Définitions : graphitisation - Dictionnaire de français Larousse" [Definitions: graphitization - Larousse French Dictionary]. www.larousse.fr (in French). Retrieved 25 October 2023.
- ^ Hardyal, Keri. "What Is graphitization? A Carbon/Graphite Engineer Explains". blog.metcar.com. Retrieved 2023-10-25.
Graphitization is the process of heating amorphous carbon for a prolonged period of time, rearranging the atomic structure to achieve an ordered crystalline structure that is typical of solids. During graphitization, carbon atoms are rearranged to fill atom vacancies and improve atom layout.
- ^ "Définition de graphitisation | Dictionnaire français" [Definition of graphitization | French dictionary]. La langue française (in French). Retrieved 2023-10-25.
