Graphite is a semimetal derived from carbon that may be synthesized or found in nature. In its natural state, it is usually dark to medium gray, brittle, shiny and electrically conductive, though it ranges from type to type, of which it is available in three forms. Naturally occurring graphite is found as lump graphite, crystalline flake graphite or amorphous graphite. Lump graphite is found in lumps, fissures and veins underground; crystalline flake graphite is flat with hexagonal edges and amorphous graphite is very flake. A process by which synthetic graphite could be made was first discovered in 1893 by a man named Charles Street. Later, in the mid-1800s, another process by which synthetic graphite could be made was accidentally discovered by Edward Goodrich Acheson, who patented his method in 1896 and began commercial production in 1897. Today, all types of naturally occurring graphite, as well as machined graphite and carbon graphite, can be used to create graphite products.
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Benefits of Graphite
Graphite has a number of positive characteristics that make it an excellent candidate for the creation of all sorts of different products. For one, graphite is extremely temperature resistant; even when immersed in environments of very high heat, it will not burn, deform, melt or chemically change. In addition, both in its natural and synthetic forms, graphite is a strong conductor of heat and electricity. Also, it can absorb neutrons, which is a characteristic incredibly useful in the regulation of nuclear reactions, and it easily leaves marks, which is why it is used to make pencil lead. Graphite products are produced for use in a wide variety of industries, including the automotive, aerospace, chemical, electrical, electronic, industrial mechanical and nuclear sectors.
Graphite Production Process
Graphite products are not only useful. Rather, they are also sustainable. They may be recycled in a number of different ways, as leftover graphite scraps and used graphite products can be melted down and reused many different times. To do so, the retired graphite products, such as old electrodes and lathes, are first melted down. Then, a mixture of these used graphite materials and some new graphite materials are ground by crushers into a fine powder. From here, the powder can be used in a variety of ways. Typically, it is mixed with other materials and then created into new products using forming methods like molding, extrusion or cold isostatic pressing. After the new graphite products are formed using one of these methods, they are heat treated in a baking oven so that they will go through carbonization.
When converted into different forms or paired with additional materials, graphite can serve many purposes. When graphite is combined with zirconia and alumina, for example, it can be used to form ladle shrouds, stopper rods and sub-entry nozzles. Likewise, powdered graphite can be used as a dry lubricant. An example of this is in steel casting, where this graphite product is used as a die lubricant to help make part ejection easier. Generally speaking, graphite in synthetic form proves very useful in the fabrication of parts used in steelmaking. This is due to its electrical conductivity, which lends it to the application as such products include electrodes used in electric arc furnaces. These conduct electricity and melt scrap steel during die casting. Also, the aforementioned graphite electrodes are sometimes used in printing processes. During these processes, they are thinly coated onto wax impressions then placed underneath a copper layer. Here, they provide the negative electrical connection needed to create electrolysis. Other commonly produced graphite products include: pencil lead, brake linings for large non-automotive vehicles, batteries, laptop components, paint, electric motor brushes and crucibles. Crucibles are containers used to hold extremely hot fluids and liquids in forging and other high heat applications.
Standards and Specifications for Graphite
While graphite products can be recycled, graphite production is not entirely friendly, as prolonged exposure to graphite and graphite dust can pose risks to human health. To keep workers safe, the Occupational Safety and Health Administration (OSHA) sets the legal limit of exposure in the workplace at a time weighted average (TWA) of 15 million particles per cubic foot (1.5 mg/m3) over an 8 hour workday. Likewise, the National Institute for Occupational Safety and Health (NIOSH) has published a recommended exposure limit (REL) of TWA 2.5 mg/m3 respirable dust over an 8 hour work day. Note that at exposure levels of 1250 mg/m3, graphite becomes urgently hazardous to human health and life. As long as those using graphite or creating graphite products in their facilities follow the codes set out to keep them and their workers safe and they wear proper clothing, however, working with graphite is perfectly safe. To learn more about graphite products, graphite production and/or safe graphite handling, contact a graphite manufacturer today.