Where does Graphene come from when it's called "upside down"?

The Graphene layer contains intracranial σ bonds and Out of sight π bonds. The σ bond gives Graphene electronic conductivity and produces weaker interactions between Graphene Layers. The Covalent σ bond forms a rigid main chain of hexagonal structure and C axis, that is, the π bond controls the association between different Graphene Layers. It shows 3 Sigma bonds/atoms on one surface and π orbital perpendicular to Sigma bonds / atomic surfaces.

Let's see, without further ado, how did you get these physical properties of Graphene?

Then let's go into the details.

1 Conductivity

Ref.:Large-scalepatterngrowthofgraphenefilmsforstretchabletransparentelectrodes.(Nature457,706-710(5February2009).|doi:10.1038/nature07719)

The novel electronic properties of Graphene are that it can maintain huge currents. The π bond in Graphene gives Graphene electronic conductivity and produces weaker interactions between Graphene Layers. The carriers in Graphene can be described by the Dirac equation instead of the Schrodinger equation. Since there is two equivalent Carbon sublattice in the Honeycomb crystal, the conical valence band and guide band intersect at the K and K0 points in the Brillouin District at the Fermi level. These No quality fermions show many superior features. Graphene is a zero-band-gap two-dimensional semiconductor material that clearly shows the bipolar electric field effect, quasi-particles, and a longer average free path (micron scale).

In addition, the two-dimensional Dirac energy dispersion means that Graphene is a zero-band-gap semiconductor material whose state density disappears linearly when approaching the Fermi level. When Graphene is conducted, its electron or Hole concentration is as high as 10E13cm-2. It shows that outstanding carrier mobility is about 200,000 cm2/V. Such high mobility is due to the perfect Graphene Honeycomb lattice that allows electrons to pass very smoothly and can control their band gaps. Like semiconductors, people can control and regulate the movement of electrons to produce the desired results. In other words, Graphene cannot be used for conduction unless it can provide energy to strengthen the gap between electrons, that is, between the valence band and the conduction band.

Here, list the conductivity of Graphene under several different techniques:

2 thermal conductivity

The thermal conductivity of Graphene at near room temperature is between (4.84 ± 0.44) × 10 E3 and (5.30 ± 0.48) × 10 E3W /m.K., 2008). Graphene prepared by chemical vapor deposition shows a lower value(<UNK> 2500W/mK) (Caietal. , 2010).

It is considered to have a certain structural type, IE AA or AB type; The number of layers of Graphene also affects its thermal conductivity. Due to the high thermal conductivity of Graphene (due to its strong CAC Covalent bonds and phonon scattering, the flawless pure Graphene monolayer can have thermal conductivity up to 5000 W/mK (Ballandineta,.2008) at room temperature. (2008) It is considered to be an important part of electronic equipment.

At room temperature, the thermal conductivity of monolayer pure graphene is much higher than that of other carbon allotropes previously studied, for example, carbon nanotubes (multiwall carbon nanotubes are 3000W/mK(Kimetal. , 2001), single-walled carbon nanotubes 3500W/mK(Popetal. , 2005). The thermal conductivity is affected by a number of factors, such as defects and edge scattering (Nikaetal. , 2009) and isotope doping(Jiangetal. , 2010).

In general, all these factors have an adverse effect on the conductivity because doping leads to the localization of defects and phonon patterns, resulting in phonon scattering.

3 specific surface area

Ref. : Graphene-BasedUltracapacitors. (NanoLett. , 2008, 8(10), PP 3498 -- 3502. | DOI: 10.1021 / NL 802558 Y)

Graphene forms a hexagonal benzene ring structure with a side length of 0.142 nm and an area of 0.052 nm2. Therefore, the surface density is 0.77 mg/m2, and the specific surface area is 2630m2 / G.

4 elastic modulus

Ref.: Measurement of the elastic properties and intrinsic strength of monolayer graph E. (science.2008Jul18;321(5887):385-8.|do i:10.1126/science.1157996.)

According to Voigt graphite structure equation:

In the formula, subscripts 1 and 2 are the two main directions within the Graphene surface, and 3 is its normal direction. The experimental measurements were C11 = 1060 Gpa, C12 = 36.5 Gpa, C44 = 4Gpa, C12 = 180 Gpa, and C13 = 15Gpa. From this moment, we can also see that due to the strong SP2 bond between carbon atoms, the elastic modulus in the graphite surface is as high as 1Tpa.

Since the high degree of Anisotropy is due to the weak interaction between Graphene, which is usually considered to be the interaction between van der Waals forces or the coupling between π electrons, the shear modulus between Graphene layers was experimentally determined to be 4Gpa, and the shear strength was 0.08 Mpa, Obviously less than the mechanical properties between carbon atoms.

The following table shows the mechanical properties of Graphene

The physical properties of Graphene after oxidation have significantly changed. It can be seen that the C-O-C bond angle in the epoxy group is the first bent, and the oxygen atom moves in the direction of the graphite surface, resulting in an oxide Graphene with Young's modulus of 610Gpa, which is lower than that of Graphene 1060Gpa.

5 Transmittance

Graphene is transparent, and single-layer Graphene absorbs 2.3 % π α <UNK> 2.3 % of white light (97.7 % light permeability), α is a fine structure constant, and its value is about ~ 1/37. The stacking order and direction affect the optical properties of Graphene; Therefore, double-layer Graphene exhibits novel and interesting optical properties.

6Chemical stability and reactivity

The high chemical stability of Graphene is due to the presence of powerful in-plane SP2 hybrid bonds in the Honeycomb network structure. Graphene's chemical inertia can be applied to prevent oxidation of metals and metal alloys. Chen et al.(Chenetal., (2011) Graphene was plated on copper and copper-nickel with chemical vapor deposition technology, demonstrating the antioxidant properties of Graphene for the first time. Graphene has the chemical stability and inertia that it is expected to improve the durability of potential optoelectronic devices(Blakeetal. , 2008).

7 Barrier

Graphene tablets have a high degree of flexibility. They can be stretched like balloons, even under the vertical pressure of several atmospheres. Even small atoms like helium cannot penetrate it. Some literature will use Graphene oxide to block the diaphragm. I have only now discovered that Graphene has to be made because of poor dispersion. After all, Graphene has a high film formation, and Graphene oxide is hydrophilic. Water absorption and Graphene is hydrophobic, better resistance.

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