Why does graphite have a layered structure

Graphite has a giant covalent structure in which:. Graphite has delocalised electrons, just like metals. These electrons are free to move between the layers in graphite, so graphite can conduct electricity. This makes graphite useful for electrodes in batteries and for electrolysis. The forces between the layers in graphite are weak.

This means that the layers can slide over each other. This makes graphite slippery, so it is useful as a lubricant. The sigma bonding system acting within a single graphene layer is exceedingly strong. The strength of the sigma bond in carbon is also illustrated by the high hardness of diamond.

Each carbon atom within the graphene layer has three of these sigma atomic orbitals, which combine with similar orbitals of adjacent carbon atoms forming the molecular bonds that hold the layer together see sp2 bonding in the organic chemistry section.

In contrast, the carbon atoms of the diamond structure each have 4 such bonds. However, your stroll would be limited only to the two dimensions covered by the graphene layer you were on. The stiff sigma bonds that give rigidity and high tensile strength to a graphene layer do not provide any support in the perpendicular direction.

Graphene layers are real structures and require some force to maintain sheet alignment as well as the proper equilibrium separation distance. The pi component is the result of weak, secondary electrical bonds formed by the overlapping pi p orbitals of the sp2 carbon network within each graphene sheet. Each carbon atom has one pi electron. This electron has a high probability of being found in a region just above or below the plane formed by the carbon atoms in a graphene layer.

Since each graphene layer can be viewed as a system of fused six-carbon rings, one can also imagine that superimposed above and below each ring there exists a ring or donut shaped region, containing six pi electrons one from each carbon atom. This de-localization of pi electrons results in what is known as resonance energy or resonance stability See section on Aromaticity and Resonance. The carbon atoms are linked together by very sturdy sp2 hybridised bonds in a single layer of atoms, two dimensionally.

Each individual, two dimensional, one atom thick layer of sp2 bonded carbon atoms in graphite is separated by 0. Essentially, the crystalline flake form of graphite, as mentioned earlier, is simply hundreds of thousands of individual layers of linked carbon atoms stacked together. So, graphene is fundamentally one single layer of graphite; a layer of sp2 bonded carbon atoms arranged in a honeycomb hexagonal lattice.

Graphite is naturally a very brittle compound and cannot be used as a structural material on its own due to its sheer planes although it is often used to reinforce steel. Graphene, on the other hand, is the strongest material ever recorded, more than three hundred times stronger than A36 structural steel, at gigapascals, and more than forty times stronger than diamond.

Buy this product. However, for this high level of electronic conductivity to be realised, doping with electrons or holes must occur to overcome the zero density of states which can be observed at the Dirac points of graphene. The high level of electronic conductivity has been explained to be due to the occurrence of quasiparticles; electrons that act as if they have no mass, much like photons, and can travel relatively long distances without scattering these electrons are hence known as massless Dirac fermions.

There are a number of ways in which scientists are able to produce graphene. The first successful way of producing monolayer and few layer graphene was by mechanical exfoliation the adhesive tape technique. However, many research institutions around the world are currently racing to find the best, most efficient and effective way of producing high quality graphene on a large scale, which is also cost efficient and scalable.

The most common way for scientists to create monolayer or few layer graphene is by a method known as chemical vapour deposition CVD. This is a method that extracts carbon atoms from a carbon rich source by reduction. The main problem with this method is finding the most suitable substrate to grow graphene layers on, and also developing an effective way of removing the graphene layers from the substrate without damaging or modifying the atomic structure of the graphene.

Other methods for creating graphene are: growth from a solid carbon source using thermo-engineering , sonication, cutting open carbon nanotubes, carbon dioxide reduction, and also graphite oxide reduction. This latter method of using heat either by atomic force microscope or laser to reduce graphite oxide to graphene has received a lot of publicity of late due to the minimal cost of production. However, the quality of graphene produced currently falls short of theoretical potential and will inevitably take some time to perfect.