Graphite, the Most Useful Mineral with Extreme Features and Users
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Author : TRUNNANO
Update time : 2020-09-24 14:45:15
What is Graphite?
Graphite is a dark gray to black, very soft, shiny metallic mineral with a distinctive greasy feeling. One of the Earth’s softest minerals, graphite will easily leave marks on paper, which is why it is used for fine artist pencils. Graphite is a naturally occurring form of crystalline carbon. It is a natural element mineral found in metamorphic and igneous rocks. Graphite is an extreme mineral. It is very soft, the pressure when splitting is very small, and the specific gravity is very low. In contrast, it has extremely strong heat resistance and is inert when in contact with almost any other material. These extreme characteristics make it widely used in metallurgy and manufacturing fields.
Geological occurrence
Graphite is a mineral that is formed when carbon is subjected to heat and pressure in the crust and upper mantle. The production of graphite requires a pressure of 75,000 psi and a temperature of 750 degrees Celsius. These correspond to granite metamorphic phases.
Graphite: Graphite crystals in a piece of marble from the Saint-Jovite Skarn Zone, Mont-Tremblant, Les Laurentides RCM, Quebec, Canada. This specimen is approximately three inches (7.6 cm) in length.
Graphite from regional deterioration (flaky graphite)
Most of the graphite seen on the surface of the earth today is formed at the converging plate boundary, where organic-rich shale and limestone are subjected to the heat and pressure of regional metamorphism. This produces marble, schist and gneiss, which contains tiny crystals and graphite flakes. When the concentration of graphite is high enough, these rocks can be mined, broken into particles that can release graphite flakes, and then processed by specific gravity separation or foam flotation to remove low-density graphite. The product produced is called "flake graphite".
Graphite in metamorphic coal seams ("amorphous" graphite)
Some graphite is formed by the metamorphism of coal seams. The organic matter in coal is mainly composed of carbon, oxygen, hydrogen, nitrogen and sulfur. The heat of metamorphism destroys the organic molecules of coal and volatilizes oxygen, hydrogen, nitrogen and sulfur. What is left is an almost pure carbon material that can be crystallized into mineral graphite.
This graphite appears in the "joints" corresponding to the original layers of coal. When mined, the material is called "amorphous graphite." The term "amorphous" is actually incorrect in this usage because it does have a crystal structure. In mines, the appearance of this material is similar to coal, without bright and dim bands.
Graphite in igneous rocks and meteorites
A small amount of graphite is known to be the main mineral in igneous rocks. It is called tiny particles in basalt flow and syenite. It is also known to form in pegmatite. Some meteorites contain small amounts of graphite. These forms of graphite are not of economic importance.
Graphite and diamond
Graphite and diamond are the two mineral forms of carbon. Diamonds are formed in the mantle under extremely high heat and pressure. Most of the graphite found near the surface of the earth is formed in the earth's crust at lower temperatures and pressures. The composition of graphite and diamond are the same, but the structure is quite different.
The carbon atoms in graphite are connected in a hexagonal network to form an atom-thick sheet. These thin plates are poorly connected, and if they bear a small force, they will easily split or slide against each other. This makes graphite have extremely low hardness, perfect cleavage and smoothness.
Instead, the carbon atoms in the diamond are connected to form a framework. Each carbon atom is connected to the other four carbon atoms with strong covalent bonds to form a three-dimensional network. This arrangement firmly holds the atoms in place, making diamond a very hard material.
Synthetic graphite
"Synthetic graphite"also called artificial graphite is made by heating high-carbon materials (such as petroleum coke and coal tar pitch) to a temperature of 2500 to 3000 degrees Celsius. At these high temperatures, all volatile substances and many metals in the raw materials are destroyed or driven away. The remaining graphite is linked into a sheet-like crystal structure. The carbon purity of synthetic graphite can exceed 99% and can be used in finished products that require extremely pure materials.
Applications of Graphite
Graphite has a variety of almost contradictory uses. An allotrope of carbon and one of the softest minerals in the world. Uses include writing instruments and lubricants. It can be made into a single-atom thick cylinder of graphene, which is a super-strength material for sports equipment. Graphite behaves like metal and can conduct electricity, but it can also be used as a high temperature resistant non-metal.
Graphite reacts with water vapor in the atmosphere to deposit a thin film on any adjacent surface and reduce the friction between them. It forms a suspension in the oil and reduces the friction between two moving parts. In this way, graphite is used as a lubricant at temperatures up to 787 degrees Celsius (1,450 degrees Fahrenheit) and as a release material up to 1315 degrees Celsius (2,399 degrees Fahrenheit). Graphite is a common refractory material because it can withstand high temperatures without chemical changes. It is used in the manufacturing process from steel and glass manufacturing to iron processing. It is also an asbestos substitute for car brake pads.
Lithium ion batteries have lithium cathodes and graphite anodes. As the battery is charged, positively charged lithium ions (a lithium salt solution) in the electrolyte will accumulate around the graphite anode. Lithium anodes can be made into more powerful batteries, but lithium swells a lot when charging. Over time, the surface of the lithium cathode will crack, causing lithium ions to escape. These, in turn, form growths called dendrites in a process that may short-circuit the battery.
TRUNNANO (aka. Luoyang Tongrun Nano Technology Co. Ltd.) is a trusted global chemical material supplier & manufacturer with over 12 years’ experience in providing super high quality chemicals and Nano materials. The graphite powder produced by our company has high purity, fine particle size and impurity content. Lower, please contact us if necessary.
