Graphite  crystalline form of the element carbon. It consists of weakly bound layers of graphene stacked into a hexagonal structure. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Under high pressures and temperatures, it converts to diamond. Graphite is used in pencils and lubricants. It is a good conductor of heat and electricity. Its high conductivity makes it useful in electronic products such as electrodes, batteries, and solar panels.

Types and varieties

The principal types of natural graphite, each occurring in different types of ore deposits.

Crystalline small flakes of graphite (or flake graphite) occurs as isolated, flat, plate-like particles with hexagonal edges if unbroken. When broken the edges can be irregular or angular.

Amorphous graphite: very fine flake graphite is sometimes called amorphous.

Lump graphite (or vein graphite) occurs in fissure veins or fractures and appears as massive platy intergrowths of fibrous or acicular crystalline aggregates, and is probably hydrothermal in origin.

Highly ordered pyrolytic graphite refers to graphite with an angular spread between the graphite sheets of less than 1°.

The name “graphite fiber” is sometimes used to refer to carbon fibers or carbon fiber-reinforced polymer. Read the full article to know more about Graphite the element of carbon by Pritish Kumar Halder.

Structure

Solid carbon comes in different forms known as allotropes depending on the type of chemical bond. The two most common are diamond and graphite (less common ones include buckminsterfullerene). In diamond the bonds are sp3 orbital hybrids and the atoms form tetrahedra with each bound to four nearest neighbors. In graphite they are sp2 orbital hybrids and the atoms form in planes with.

The two known forms of graphite, alpha (hexagonal) and beta (rhombohedral),have very similar physical properties, except that the graphene layers stack differently: stacking in alpha graphite is ABA, as opposed to ABC stacking in energetically less stable and less common beta graphite. The alpha form can be converted to the beta form through mechanical treatment and the beta form reverts to the alpha form when it is heated above 1300 ° .

Uses of natural graphite

Natural graphite is mostly used for refractories, batteries, steelmaking, expanded graphite, brake linings, foundry facings, and lubricants.

Refractories

The use of graphite as a refractory (heat-resistant) material began before 1900 with graphite  crucibles used to hold molten metal; this is now a minor part of refractories.

Batteries

The use of graphite in batteries has increased since the 1970s. Natural and synthetic graphite are used as an anode material to construct electrodes in major battery technologies.

The demand for batteries, primarily nickel–metal hydride and lithium-ion batteries, caused a growth in demand for graphite in the late 1980s and early 1990s – a growth driven by portable electronics, such as portable CD players and power tools. Laptops, mobile phones, tablets, and smartphone products have increased the demand for batteries. Electric-vehicle batteries are anticipated to increase graphite demand. As an example, a lithium-ion battery in a fully electric Nissan Leaf contains nearly 40 kg of graphite.

Radioactive graphite from old nuclear reactors is being researched as fuel. Nuclear diamond battery has the potential for long duration energy supply for electronics and the internet of things.bles used to hold molten metal; this is now a minor part of refractories.

Steelmaking

Natural graphite in steelmaking mostly goes into raising the carbon content in molten steel; it can also serve to lubricate the dies used to extrude hot steel. Carbon additives face competitive pricing from alternatives such as synthetic graphite powder, petroleum coke, and other forms of carbon. A carbon raiser is added to increase the carbon content of the steel to a specified level. An estimate based on USGS’s graphite consumption statistics indicates that steelmakers in the US used 10,500 tones in this fashion in 2005.

Brake linings

Natural amorphous and fine flake graphite are used in brake linings or brake shoes for heavier (nonautomotive) vehicles, and became important with the need to substitute for asbestos. This use has been important for quite some time, but nonasbestos organic (NAO) compositions are beginning to reduce graphite’s market share. A brake-lining industry shake-out with some plant closures has not been beneficial, nor has an indifferent automotive market. According to the USGS, US natural graphite consumption in brake linings was 6,510 tones in 2005.

Reference

https://en.wikipedia.org/wiki/Graphite