The graphite is a natural modification of carbon: its atoms are set in the hexagonal model, typical of carbon, creating a stratified lattice and the graphite takes on its typical grey colour, from an opaque shade to black crystals.
This material has a layered structure and in each layer, every carbon atom is bonded to three other: this results in a 2-dimensional hexagonal net with inside strong bonds and layers with very weak bonds. Therefore, layers can be easily moved against each other and separated too.
Graphite is found naturally on earth, but it can also be synthetically produced: the production’s process of the synthetic graphite is very complicated; however, it offers the possibility to change the graphite properties.
Electric and heat conductivity and high resistance to chemical agents.
Graphite applications are numerous: it is required for electronic and electric applications, for metallurgy, for glass and quartz glass production as well as for mechanical and nuclear applications.
A trigonal soft, greasy and dark-grey mineral, with a metallic sheen and easily flaked. The graphite is a good conductor of electricity and heat, rustproof and acid resistant, which melted only at about 3000 °C and which finds application in many sectors, from electrical engineering to electronic, from metallurgy to chemistry and industry and as protective material for nuclear energy production facilities.
The graphite is also used for the preparation of anti-oxidant varnishes, lubricant blends and for manufacturing pencils together with kaolin.
It is present in metamorphic rocks and it was located in the valleys of Chisone, Pellice, Bormida (Millesimo) in Italy. Today you can find it in other places situated in China, France, Germany and Canada. The artificial graphite is produced by heating at high temperatures carbonaceous material such as anthracite, charcoal and petroleum coke.
The production of the synthetic graphite began at the end of the 19th century, precisely in December 1895, in the USA, when a patent for the carbon graphitization was filed.
The electrographite produced in this manufacturing process was used as electrical current transmission element in the form of electrodes and graphite has since become increasingly important for a wide range of industries and sectors.
The core of the synthetic graphite is made of a very hard carbon part, usually crude petroleum coal, and pitch acting as binder. The two raw material are mixed together to make up a homogeneous mass and then processed and refined in complex processes at high temperature. These processes can vary depending on the desired properties and on the type of synthetic graphite. In this way, a process can be reproduced in a short time, especially when compared to the natural one, which takes million years.
The morphology of the greatest part of the synthetic graphite ranges from flakes of the fine powders to the irregular grains and tips of the coarse products. This technical presentation includes electronic scan micrographs of the morphology of calcined petroleum coke materials to be graphitized, crystalline graphite in flakes, present in nature, and synthetic graphite finely ground.
The “isostatic graphite” refers to the graphite isostatically created: this means that the mixture of raw materials is pressed into rectangular or round blocks in a so-called cold isostatic press (CIP). Compared to other processes, such as extruding or vibration moulding, this technology can produce a more isotropic kind of synthetic graphite.
In addition, the isostatic graphite has usually the smallest grain sizes of all the synthetic graphite. The isostatic graphite nowadays represents the large majority of the market of this fine-grain material and it has found application in over 30 different sectors: from nuclear and metallurgical applications to semi-conductor devices, solar industry and many others.
Among the isostatic graphite’s applications, there are billets, conveyor belts, pipes and melting of various metals including aluminium, brass, bronze, (grey and ductile) iron, nickel silver (alpaca), copper-nickel, metal precious alloys, silver, gold and various parts used in electroerosion sector.
The extruded graphite is produced by extrusion process: it has coarser grain sizes and lower resistance compared with the isostatic graphite, but a higher electrical and thermal conductivity.
Common uses of the extruded graphite include evacuation roller conveyors, rings, rollers, nozzles, crucibles, stirrers, wear plates, sockets, pipes, discs, moulds for sintering process, separators, lining for furnaces and lubricants for all the sectors.
Generally used in iron and non-iron alloys foundries