When atoms of more than one element are combined, they form chemical compounds. Iron oxide, which is easily recognizable as common rust, is the combination of iron and oxygen atoms. Water is a chemical compound composed of oxygen and hydrogen. Multiple chemical compounds can be formed by combining different ratios of their component elements. For example, combining two hydrogen atoms with a single oxygen atom creates a molecule of water. Combining two hydrogen atoms with two oxygen atoms creates a molecule of hydrogen peroxide.

Although they are composed of identical atoms, elements can be connected in different geometries to produce different molecular structures. These forms are called allotropes of the element.

Carbon and oxygen offer two well-known examples of common allotropes. Breathable oxygen consists of two atoms of oxygen bonded together to form a single diatomic oxygen molecule. It is common to see oxygen represented by the chemical notation O2. However, oxygen atoms can also be joined three at a time. Instead of breathable oxygen, the O3 oxygen allotrope is known as ozone.

Carbon, one of the most basic building blocks of all life on Earth, can be joined to other carbon atoms in a variety of geometries. When the atoms are connected in a tetrahedral lattice known as the adamantine structure, pure carbon exists as diamond. When the atoms are joined together in a hollow sphere, ellipsoid or tube, pure carbon exists as a fullerene. When the atoms are connected in stacked, planar sheets of hexagonal lattices with a separation of 0.142 nanometers and interplanar distances of 0.335 nanometers, pure carbon exists as graphite. A single atomic layer of the graphite sheet is known as graphene. Carbon atoms connected without any discernable crystal structure forms charcoal or soot.

Diamonds are valuable as gemstones and as cutting and polishing tools in industrial applications. They have the highest known hardness of any material available in bulk quantities.

Fullerenes, specifically buckyball clusters and fullerene carbon nanotubes, have been intensely studied since they were discovered in 1985. They have continuing implications in cutting-edge materials science and nanotechnology applications.

Graphite has been known and used since the 4th millennium B.C., but the name graphite wasn’t coined until 1789. Graphite demand has historically been limited to use as the marking material in pencils, as high-end coal, as molds for metal casting, as the carbon ingredient in steel formulations, and as a dry lubricant. Air and water get between the planar sheets of graphite and cause the sheets to slide smoothly across one another.

Graphite occurs in three natural ores. Crystalline flake graphite, which is often simply called flake graphite, is found as flat, plate-like particles with hexagonal edges. Amorphous graphite is found as fine particulate that occurs following the natural or industrial thermal metamorphism of coal. Lump graphite, which is often called vein graphite, is found in hydrothermal fissure veins or fractures.

The United States Geological Survey reports that flake graphite mining surpassed 1,110 kilotons in 2008. China, India, Brazil, North Korea and Canada house the largest flake graphite mining operations and are the major exporters of the material.

Single layers of graphite that are only one atom thick are known as graphene. Single layer graphene foils were first described by Hanns-Peter Boehm in 1962. They are the basic structural element of graphite where graphene sheets are stacked one on top of the other, carbon nanotubes where graphene sheets are rolled into a tube and joined at two parallel edges, and fullerene spheres where the edges of a graphene sheet are all joined to create a sphere.

The interest in graphene is intense, and the graphite market may soon experience explosive growth as a result. The Nobel Prize in Physics for 2010 was awarded for a series of experiments with graphene, and the material is poised to play a major role in the emerging field of spintronics. Spintronics, which is more properly known as magnetoelectronics, exploits the intrinsic spin and magnetic moment of electrons to store information in solid state devices. Quantum computers utilize spintronic principles.

Graphene has both the small spin-orbit interaction and the extremely minute nuclear magnetic moment required in spintronic material. It has demonstrated a spin coherence length greater than one micrometer at room temperature, and the spin current polarity can be controlled with a low-temperature electrical gate.

Graphene oxide membranes are being used for room-temperature distillation of ethanol. The membranes are impermeable to all gases, but they allow water vapor to pass through. Commercialization of this technology could dramatically impact the cost of bulk biofuel production.

In graphene nanoribbon applications, graphene is cut into a particular pattern to create specific unbounded edge configurations and yield electrical properties associated with the structure. Many of these ribbons are semiconductors, and the band energy gap has been shown to decrease with increasing ribbon width. The two-dimensional structure, electrical conductivity characteristics and low noise of graphene nanoribbons make them a prime candidate to replace copper in integrated circuit boards. The drawback is that graphene sheets are still difficult to produce.

Graphene is also one of the strongest materials known. It has a breaking strength 200 times greater than steel. Again, the limiting factor in the development of applications for the material is the difficulty of separating graphene layers from graphite.

California Lithium Battery, in a cooperative agreement with Argonne National Laboratory, recently announced that work has begun on the commercialization of a third-generation lithium-ion battery that uses a graphene silicon carbide anode. The graphene silicon carbide anode is significantly lighter than current electrode materials, and the company increases battery capacity by maintaining the same overall battery weight but using lighter materials.

Graphite demand will increase as these technologies mature, and the relatively limited graphite market is predicted to expand to keep pace.