Graphite is a form of carbon with unique properties, including conductivity and anisotropic heat and sound conduction. It is used as a lubricant, in steel production, and in composite materials. Its name comes from its use in pencils, but it is not related to lead.
Graphite is an allotrope of the element carbon, meaning it is one of several different forms of the pure element with a unique arrangement of its atoms, compared to other forms of carbon. The arrangement of carbon atoms in graphite molecules gives this substance some unique properties. It can be used as a lubricant and has characteristics normally only attributed to metals. It is also similar, in some ways, to coal. This unusual combination of characteristics makes graphite suitable for many different applications.
The substance name graphite was coined by a German geologist in the 18th century who adapted the Greek word “grapho”, meaning “to write” due to its use in pencils, a usage still common today. In this application, graphite is often called “pencil lead” or “lead”, but this is misleading, as it is not lead at all. Graphite is a natural mineral composed of pure elemental carbon.
The physical properties of graphite are very similar to those of coal. Its molecules are arranged in hexagonal lattices that form sheet-like arrangements. It is this molecular configuration that contributes to graphite’s excellent properties as a lubricant, both in dry form and suspended in a liquid, usually oil. It is one of the softest of all naturally occurring minerals and is easily scratched with a fingernail. It appears as a dark, silvery solid.
Like coal, to which it is chemically identical, graphite is sometimes found in large veins within some metamorphic rocks, or as small, scattered flakes within a variety of minerals. The properties of graphite, however, make it unsuitable for use as a fuel, as it is very difficult to burn. Similarly, graphite is chemically very stable and nearly inert.
One of the most interesting properties of graphite is its conductivity. Graphite conducts electricity, which is unusual for a substance that is not a metal, especially since at least one other elemental carbon allotrope, diamond, is not conductive at all and is in fact a very good insulator. However, it is not as conductive as a metal and is sometimes classified as a semiconductor. Another of the interesting properties of graphite is its strong anisotropic heat and sound conduction properties. This means that it conducts heat and sound very well in one direction while doing it poorly in other directions.
Science and industry have found many uses for graphite. In addition to its applications as a pencil filler and a wide range of highly effective lubricants, graphite’s properties make it suitable for use in the production of steel, high-strength and lightweight composite materials, and as a component for composite brake pads, among the numerous other uses. Its softness would seem to make it an odd choice for high-strength composites such as those used in skis and fishing rods, but while the flat formations of its molecules make it soft, these sheets can be rolled up and formed into fibers with enormous resistance due to the strong bonds between individual atoms.
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