The physical and optical properties of graphene

Physical and chemical properties
physical properties
internal structures
carbon atoms inside graphene are arranged in the same way as graphite monoatomic layers in a
sp
2
hybrid orbit, and have the following characteristics: carbon atoms have 4 price electrons, of which 3 electrons generate
sp
2
keys, i.e. each carbon atom contributes an unkeyed electron located in the
pz
orbit, and the
pz
orbit of the adjacent atom is perpendicular to the plane to form π keys, and the newly formed π key is semi-filled. The study confirmed that the ration of carbon atoms in graphene is 3, the bond length between each of the two adjacent carbon atoms is 1.42×10
-10
meters, and the angle between the key and the key is 120 degrees. In addition to the cellular layer structure in which σ bonds are linked to other carbon atoms in hexagon rings, the
pz
orbit of each carbon atom perpendicular to the layer plane can form large π bonds (similar to benzene rings) that run through the entire layer, thus having excellent conductivity and optical properties
C.
).mechanical properties
graphene is one of the most powerful materials known, but also has good toughness and bendability, graphene theoretical Yang's mod of 1.0TPa, the inherent stretch strength of 130GPa. The use of hydrogen plasma modified reduced graphene also has a very good strength, the average module can be large 0.25TPa.Graphite paper consisting of graphene sheets has many holes, so graphite paper appears very brittle, however, oxidized to obtain functional fossil ene, and then made of functional fossil graphene graphite paper will be extremely strong and strong.
electronic effect
Graphene has a carrier migration rate of approximately 15,000 cm
2
/(V.s) at room temperature, which is more than 10 times that of silicon and more than twice that of InSb, the substance with the highest known carrier migration rate. Under certain conditions, such as at low temperatures, graphene's carrier migration rate can be as high as 250,000 cm
2
/(V.s). Unlike many materials, graphene's electron migration rate is less affected by temperature changes, and at any temperature between 50 and 500K, the electron migration rate of single-layer graphene is around 15,000cm
2
/(V.s).
Graphene constitutes Fullerene, carbon nanotubes, and graphite schematics
in addition, the semi-integer-numbered sub-Hall effect of electronic carriers and cavity-carrying fluids in graphene can be observed by altering chemical potentials through electric field action, and scientists have observed this quantum Hall effect of graphene at room temperature.The carriers in graphene follow a special quantum tunneling effect that does not produce backsllow when encountering impurities, which is the reason for the ultra-strong conductivity of graphene and the high rate of carrier migration. The electrons and photons in graphene have no static mass, and their speed is a constant that has nothing to do with momentum.
graphene is a zero-distance semiconductor because its conduction and price band meet at Dirac Point. The edge of the momentum space at the six positions of the Dirac point is divided into two sets of equivalent three parts. In contrast, the main points of traditional semiconductors are Γ, with zero momentum.
thermal
graphene has very good thermal conductivity. With a thermal conductivity of up to 5300W/mK, pure, defect-free single-layer graphene is by far the highest thermally conductive carbon material, higher than single-wall carbon nanotubes (3500W/mK) and multi-wall carbon nanotubes (3000W/mK). When it is used as a carrier, the thermal conductivity can also reach 600W/mK. In addition, the ballistic thermal conductivity of graphene can be lowered by the lower limit of the ballistic thermal conductivity of carbon nanotubes per circumferon and length.
thermal conductivity experimental values
resistance coefficient and temperature coefficient
optical properties
graphene has very good optical properties, absorption rate of about 2.3% over a wide wavelength range, looks almost transparent. Within the thickness range of several layers of graphene, the absorption rate increased by 2.3% for each additional layer of thickness. Large areas of graphene films also have excellent optical properties, and their optical properties vary with the thickness of graphene. This is an unusually low-energy electronic structure of single-layer graphene. At room temperature, voltage is applied to the double-gate double-layer graphene field effect transistor, and the band gap of graphene can be adjusted between 0 and 0.25eV. With a magnetic field applied, the optical response of the graphene nanoband can be tuned to the tyhertz range.
when the intensity of the incoming light exceeds a certain threshold, graphene absorbs it to saturation. These properties allow graphene to be used as a passive lock-mode laser.This unique absorption may become saturated when the input light strength exceeds a threshold, which is called saturation effect, and graphene can be saturated easily under the powerful excitation of the near-infrared region due to global optical absorption and zero band gap. Due to this special properties, graphene is widely used in ultra-fast photons. The optical response of the graphene/graphene oxide layer can be tuned. With denser laser illumination, graphene may have a nonlinear phase shift optical nonlinear Kerr effect.
solubility:
show good solubility in non-polar solvents, with super-hydrophobic and ultra-oil-affinity.
melting point:
scientists said in a 2015 study that about 4,125K, and other studies suggest that melting point may be around 5,000K.
other properties:
can absorb and dissoection a variety of atoms and molecules.
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