What is graphene? How is graphene refined?

What is graphene?


Graphene is a single-layer carbon atom surface material peeled off from graphite material. It is a two-dimensional structure of carbon. The thickness of this graphite crystal film is only 0.335 nanometers. If 200,000 films are stacked together, it will only be as thick as a hair. It was first discovered in 2004 by the team of Kostya Novosev and Andre Geim of the University of Manchester. The advent of graphene has triggered a research boom around the world. Not only is it one of the thinnest known materials, it is also extremely strong and hard; as a simple substance, it can transfer electrons faster than any known conductor at room temperature.


Graphene has a very specific structure at the atomic scale that must be described using relativistic quantum physics. The structure of graphene is very stable, and so far, researchers have not found any missing carbon atoms in graphene. The connections between the carbon atoms in graphene are very flexible. When external mechanical force is applied, the carbon atom faces bend and deform, so that the carbon atoms do not have to be rearranged to adapt to the external force, thus maintaining structural stability. This stable lattice structure gives carbon atoms excellent electrical conductivity. As electrons in graphene move in orbits, they are not scattered by lattice defects or the introduction of foreign atoms. Because the force between atoms is very strong, at room temperature, even the surrounding carbon atoms collide.



How is graphene refined?


It was the graphene "teared" out of tape in this way that brought the two British scientists the Nobel Prize, and also set off a graphene research craze in the global scientific community. Scientific research has discovered that the single-atom structure of graphene gives it many extraordinary and magical properties.


First, it's very thin. Graphene is the thinnest nanomaterial currently known. How thin? A 1 mm thick graphite sheet can peel off up to 3 million pieces of graphene.


Secondly, it has high transparency and good light sensitivity. The transmittance of graphene to infrared light, visible light, and ultraviolet light reaches 97.7%; its light transmittance is very good in a wide range of wavelengths, and the light absorbed by it can be quickly converted into light of other wavelengths.


Third, the airtightness is good. It is airtight and watertight, and has strong resistance to corrosive solutions such as strong alkali and strong acid; it can effectively inhibit the growth of bacteria.


Fourth, high intensity. Graphene is twice as strong as diamond and 200 times as strong as steel. It is the hardest material known. Someone made this analogy: If you cover a cup with a graphene product that is as thin as food plastic wrap and want to pierce it with the tip of a pencil, you would have to have an elephant stand on the pencil.


Fifth, the toughness is very good. Graphene is the most flexible material known and has a very high resistance to pressure. An ordinary graphene packaging bag can lift a 2-ton car.


Sixth, it has low resistivity and is the most conductive material known. It is called a super conductor; it is also the best known thermal conductor. In addition, graphene is highly sensitive, and even the adsorption or release of tiny gas molecules can be detected through tiny resistance changes on graphene.


Graphene is divided into two categories: graphene powder and graphene film. Common graphite powder production methods are mechanical exfoliation, redox, and SiC epitaxial growth. The production method of graphene films is chemical vapor deposition (CVD).



The most promising application of graphene at present is to become a substitute for silicon, making ultra-miniature transistors, and used to produce future supercomputers. Replacing silicon with graphene could allow computer processors to run hundreds of times faster.


In addition, graphene is almost completely transparent, absorbing only 2.3% of light. On the other hand, it is so dense that even the smallest gas atoms (hydrogen atoms) cannot penetrate it. These characteristics make it very suitable as a raw material for transparent electronic products, such as transparent touch displays, light-emitting panels and solar panels.


As the thinnest, strongest, and most electrically and thermally conductive new nanomaterial discovered so far, graphene is called "black gold" and the "king of new materials.