Number of carbon atoms packed in a two-dimensional (2D) grid cells as flat single layer give the graphene. This is a key building block for graphitic materials of all sizes. It can be enclosed in fullerenes (0D), rolled into 1D nanotubes or stacked into three dimensional graphite.
A serious step forward in the study of graphene was when Andre Geim and Kostya Novoselov from Manchester extracted Singlet thick crystallites (graphene) from crude graphite in 2004.
The unique electronic properties of graphene produce an unexpectedly high opacity for one atomic monolayer, with amazingly simple value : it absorbs ~ 2.3 % of white light . This is a consequence of the unusually low energy electronic structure of monolayer graphene saws which electrons and holes tapered zone which meet each other at the point Dirac which is qualitatively different from the more common solid square zones.
In 2008 carried out the first experiment proves that graphene is the strongest material that exists in nature. The measurements showed that graphene has a tensile strength of 100 times greater than steel.
Graphene is different from most conventional 3D materials. The natural Graphene presents a semimetal or zero-gap semiconductor.
Been a long time since we talked through the Medgreece in graphene and its unique properties. Graphene is a material which was discovered relatively recently, and its main feature is that it is a graphite sheet consisting of a lattice of carbon atoms linked together as shown in the photo of the article ( we could characterize as a wire ) which has a thickness of a single atom . So far it has been described as the ideal replacement for silicon , and has a very low resistance and higher conductivity which can lead to the creation of faster chips for computers . And all at room temperature . Where else could however be used graphene ?
From the University of California , and Alexander Balandin (Chair of Materials Science and Engineering), investigated the possibility of using graphene sheets as heat conductors .
The researchers call these cards “quilts” ( like a quilt ) and that is because the graphene sheets are not homogeneous but consist of ” flakes ” graphene , which overlap creating a spreadsheet. Only unlike the quilt ( we all know ) the ” quilt ” of graphene flakes will not retain heat, but will remove it .
The graphene sheets can be used to extract heat from parts of a circuit which, due to the high speed flow of electrons ( current) particularly heated , which leads to impaired function of the circuit. Helping the diffusion of that heat , graphene will help create sdti much faster chip .
Graphene based on measurements made ​​by the researchers shows remarkably high thermal conductivity that surpasses even that of diamond and carbon nanotubes.
The properties of graphene , (electrical conductivity , low resistance , high thermal conductivity ) find no scope only chip electronic circuits. As we mentioned previously this technology could even be used to improve the photovoltaic , since one of the main problems (in terms of performance ) is the high resistance of the conductor carrying the current. Graphene thanks to its properties , could significantly increase their performance
Chapter 1: Carbon Nanostructures
1.1 A new class of materials
The two-dimensional (2D) crystalline materials have only recently been identified and investigated. [1] The first material that falls into this category, is graphene, a singlet carbon layer. This new material has unique properties that make it extremely interesting both as basic knowledge, as well as for future applications. The electronic properties of graphene, for example, have resulted in an unusual quantum Hall [2], [3]. It is a transparent conductor [4] with a thickness equal to the extent of zp orbital of an atom of carbon (0,344 nm). It also has parallels with the physics of elementary particles which for example displays an unusual tunneling [5], [6], which was predicted by the Swedish Natural Oscar Klein [7]. Additionally, graphene exhibits excellent mechanical and electrical properties. Its mechanical strength is greater than steel while it can be bent. The thermal and electrical conductivity is very high and can be used as a flexible conduit. The Andre K. Geim and Kostantin S. Novoselov from the University of Manchester, were awarded the 2010 Nobel Prize for the production, isolation and identification of graphene [1].
1.2 Forms of carbon
Carbon is perhaps the most exciting element of the periodic table. It is the basis of DNA and life on earth. O coal occurs in different forms. The most common form of carbon, graphite, which consists of “stacked” sheet carbonates hexagonal structure. At high pressures, the diamond is created, which is a metastable form of carbon.
A relatively new form of molecular carbon, are the Fullerenes (Fullerenes) [8]. The most “ordinary” fullerene consists of 60 carbon atoms (60 C) and has the shape of a football. It is consisting of 20 hexagons and 12 pentagons which enable the surface to form a ball. The discovery of fullerenes was awarded the Nobel Prize in Chemistry in 1996. The existence of a pseudo-one-dimensional form of carbon, carbon nanotubes, has been known for many decades and the existence of single-wall carbon nanotubes in 1993 [9]. The nanotubes are formed by “winding” of a graphene sheet so as to acquire a cylindrical shape with hemispherical ends with a configuration similar to that of the fullerene. The electronic and mechanical properties of metallic nanotubes, show many similarities with those of graphene.
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It was already known that the toner is composed of hexagonal carbon levels which are “stacked” on top of one another but scientists believed that such a singlet carbonate sheet could not be produced. In 2004, however, scientists A. Geim, K. Novoselov and colleagues [1] showed that such an individual could be isolated and was stable. The singlet this level carbon called graphene.
Figure 1.1. The graphene sheets form the native structure of the graphite, carbon nanotubes and fullerenes [11]. It should be noted that structures similar to graphene has been known since the 1960s [10] but there were experimental difficulties in isolating them and raises doubts about whether this would be possible. The amazing thing is that a simple pencil contains graphite and as it moves the paper, toner levels separated in a very small part of which contains some of singlet layers of graphite, ie graphene. The difficulty is not the production of graphene structures but rather to isolate large quantities of singlet levels for the identification, characterization and study its properties. This just managed to make the Geim and Novoselov.
1.3 Graphene
Graphene is called a singlet level of carbon atoms arranged in a hexagonal lattice, with nearest neighbor distance of atoms 0.142 nm. It is the first truly two-dimensional crystalline material and is representative of a whole class of two-dimensional materials which includes for example
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