Graphite is a mineral from the native elements class, one of the allotropic forms of carbon. Its chemical formula is C.
Graphite has a crystalline structure in which carbon atoms form flat hexagons, known as graphene.
It occurs in nature as a mineral. It is a gray or black opaque material with a metallic luster. Natural graphite is formed as a result of the metamorphism of organic substances such as peat or wood. It is found in many parts of the world.
The name “graphite” is derived from the ancient Greek word “γράφειν” (graphein), which means “to write.” Graphite easily leaves a gray residue on paper or other rough surfaces when individual flakes are rubbed off, which is used in pencils.
Physical characteristics of graphite
Physical characteristics of graphite include:
- Crystal Structure: It has a crystalline structure in which carbon atoms form flat hexagons, known as graphene. Graphene layers have a unique thickness consisting of just one atomic layer.
- Softness: It is a very soft material and can be easily smeared or flaked. This softness makes it useful for making pencils and other writing instruments.
- Black Color: It has a characteristic black or gray color, typically associated with its light-absorbing properties.
- Electrical Conductivity: Graphite is a good conductor of electricity due to the structure of its atoms and the presence of free electrons. This makes it important for manufacturing electrodes in batteries and electronics.
- Thermal Conductivity: Graphite has good thermal conductivity and is used in the production of heat exchangers and other thermal systems.
- Lubricant Material: It is an effective lubricant material as it has a low friction coefficient.
- Corrosion Resistance: Graphite is resistant to the effects of oxygen and many chemical reagents, making it important in various applications.
- Malleability: It can be easily shaped and is used for making various products such as crucibles and electrodes.
- Ease of Machining: It can be machined using various methods, including milling, drilling, and grinding.
Chemical characteristics of graphite
Chemical characteristics of graphite are determined by its composition and structure, namely carbon atoms that form hexagonal crystalline layers.
The key chemical characteristics of graphite include:
- Composition: Consists exclusively of carbon atoms (C). Each carbon atom forms four covalent bonds with other carbon atoms, creating a network of carbon atoms.
- Bonds: It has a specific structure with carbon atoms forming covalent bonds in the shape of hexagons, creating flat hexagonal layers.
- Interaction with Oxygen: Is resistant to the effects of oxygen and does not burn under normal conditions.
- Chemical Stability: It is chemically stable and does not react with many chemicals, such as oxygen, acids, and alkalis, under normal conditions.
- Surface Reactions: It can react with oxidizing agents at high temperatures, producing carbon dioxide (CO2).
- Specific Reactions: Can undergo chemical modifications to obtain specific chemical properties, for example, by using oxidizing agents to obtain graphite oxide, known as graphene.
In general, it is quite stable and chemically inert at low temperatures and typically only reacts when exposed to highly aggressive chemical environments or at high temperatures.
Production of artificial graphite
Artificial graphite can be produced through various methods in laboratory conditions and on an industrial scale. Here are some primary methods for obtaining artificial graphite:
- Thermal Decomposition of Hydrocarbons: In this method, carbonaceous materials such as coal and petroleum products are subjected to high temperatures in a vacuum or an argon atmosphere (pyrolysis). During pyrolysis, hydrocarbons decompose, and carbon forms graphite material.
- Graphitization: Graphitization involves heating high-carbon content materials like coke or carbon fibers at high temperatures (above 2500°C) in a vacuum or under a protective atmosphere. During graphitization, carbonaceous material transforms into graphite.
- Chemical Vapor Deposition (CVD): This method involves the gradual deposition of carbon atoms from the gas phase onto a substrate through chemical reactions. A gas precursor, typically methane or acetylene, is introduced into a reaction chamber along with catalysts that facilitate carbon deposition onto the substrate. This method is used to produce thin graphite films.
- Exfoliation of Graphene: Graphene, a single atomic layer of graphite, can be obtained through the exfoliation of graphite or other carbon materials like graphite or carbon nanotubes. This technique involves isolating a single atomic layer from multi-layered materials.
- Synthesis from Carbon Compounds: Graphite can be synthesized from carbon compounds, such as carbides, through reactions with metals, e.g., reactions with metallic sodium.
These methods allow for the production of artificial graphite with various properties and applications, depending on the specific manufacturing process and conditions.
Graphite has a wide range of applications due to its unique physical and chemical properties. Here are some primary industries and applications of graphite:
- Pencils: Used to make “graphite” pencils due to its softness and ability to leave a mark on paper.
- Electrodes: Used in electrode systems, such as batteries, steel production, anodes for electrolysis, electrodes for chemical reactions, and more.
- Heat Exchangers: It is used to manufacture heat exchangers and equipment for thermal processes because of its high thermal conductivity.
- Lubricants: Used as a lubricant in machinery and equipment due to its low friction coefficient.
- Nuclear Energy: It is used as a moderator in nuclear reactors to control nuclear reactions.
- Electronics: Graphite films and graphene are used in electronics to make transistors, sensors, thermoelectric elements, and other components.
- Protective Coatings: Graphite coatings are used to protect metals from corrosion and oxidation.
- Casting of Skates: Graphite is used for casting skates from skate steel.
- Electrolytic Tanks: It is used to make tanks and containers for storing chemicals.
- Aerospace Industry: Composites are used in aerospace applications, such as rockets and satellites.
- Structural Materials: Composites are used to create lightweight, strong, and high-temperature-resistant construction materials.
- Medicine: Graphite is used in medical research, including the creation of nanomaterials for drug delivery and diagnostics.
These are just a few examples of graphite applications. Its unique properties make it an essential material in many fields of science, technology, and manufacturing.