'Graphene' - The Future of Engineering

 

Bansilal Ramnath Agarwal Charitable Trust's

Vishwakarma Institute of Technology

(An Autonomous Institute affiliated to Savitribai Phule Pune University)

Vishwakarma Institute of Technology, 666, Upper Indiranagar, Bibwewadi , Pune, Maharashtra, INDIA - 411 037.

Contact No. +91 - 20 - 2428 3001

GRAPHENE

            Graphene is one of the carbon allotropes and one atom thick layer of carbon connected by hybridized bonds. Its layers are arranged in two-dimensionalhexagonal structure which is called as honeycomb lattice. The name is derived from the element graphite having -ene as the suffix in which -C=C- has been attributed highest priority in the organic compound. Each and every atom of graphene is connected to its three nearest atoms by strongest types of sigma bond. Graphene is also known as the mother of different graphitic forms present up to date. It has remarkable property is that energy of electrons is dependent linearly on the wave vector near the crossing points in the Brillouin zone.

 

Graphene: - mother of all graphitic forms

 

Discovery of Graphene: -

            P. R. Wallace Was the first who explored graphene very first time in 1947 as starting point for understanding properties of 3D graphite. Hanns-Peter Boehm published a study in 1961-62 of extremely thin flakes of graphite and introduced the term “GRAPHENE”. In 1984 Gordon Walter Semenoff and David DiVincenzo emphasized the occurrence of magnetic field of an electronic level precisely at Dirac point which describes unusual electron transport properties of material. Transmission electron microscopy (TEM) works on the single sheets of graphite. It was used in the description of carbon nanotubes by R. Saito and Mildred in 1992 as well as in 2000 for polycyclic aromatic hydrocarbons by S. Wang.

Finally, Richard L. Dudmanas well as Robert B. Rutherford filed for a patent in 2002 to produce graphene by repeatedly peeling off layers from graphite flake adhered to subtract, achieved graphite thickness of 254 Nanometer. Graphene was isolated in proper manner and characterized at university of Manchester by Andre Geim and Konstantin Novoselov in 22 October 2004. By using adhesive tape, they pulled graphene layers form graphite in process calledMicro-mechanical cleavage or exfoliationtechniques. It is used to obtained single layer or atomically thin sheets of the graphene. It is also carried out by electrostatically as well as by using electromagnetism in air, vacuum or inert environment. In 2014 National Graphene Institute was established for further studies.

 

Production of Graphene: -

Now a days graphene used in many commercial applications. According to the need there are various production techniques of the graphene.

Mechanical way of production: -

1.      Mechanical exfoliation

Mr. Geim and Mr. Novoselov used adhesive tape for extraction of the grapgene from the graphite. But for getting single layer of graphene, multiple exfoliation steps are required. By doing this we get thin layer called as flakes which is deposited on silicon wafer. But these flakes of graphene are visible to naked eyes. As technology gets developed the number of defects in flakes gets reduced and mobility of electrons is highest as of 2014. The sharp single crystal diamond wedge are used to divide layers of graphite. As well as in the year 2014, an unoxidized graphene with liquids were made by scientist which was defect free.It is made up of graphite with the help of mixers that produce local shear rate greater than 10 * 10⁴ .

2.      Ultrasonic exfoliation

By using Sonification with centrifugation method spreading graphite in a liquid medium, graphene can be obtained. Heptane and water are used as ionic liquid for dispersing. Surfactant is used as solvent before the sonication to prevent restacking helps to increase the concentration at higher level. Sonication of graphite in between two liquids, heptane and water produced macro scale graphene films.

Splitting monolayer carbon

Nanotube slicing and fullerene splitting

One of the easiest is to opening carbon nanotubes by cutting it, and putting it in potassium permanganate and sulfuric acid to get graphene. In Fullerene splitting method, spraying buckyballs at supersonic speed on to the substrate, the balls get open by cracking and result into the unzipped cages. Then form a bond in between them to form films of graphene.

Chemical Way of production: -

1.      Molten salts

In this method graphite particles are allowed to corrode in the molten salts which forms different nanostructures, one of them is graphene. We can observe that Hydrogen cations can be discharged on graphite which is cathodically polarized as hydrogen is dissolved in molten lithium chloride and from that cathode, we can peel odd the graphene sheets. These nanosheets are of high degree of crystallinity with the great thermal stability.

2.      Electrochemical synthesis

We can also exfoliate graphene by electrochemical synthesis. The graphite is first immersed in the solvent for intercalation purpose and by varying voltage we get required properties as well as in controlled manner.

3.      Hydrothermal self-assembly

This method is easy and safethan other techniques. It is also environmental free than the exfoliation techniques. From sugar like glucose, fructose graphene has been prepared. This method is also known as Tang-Lau method as we can extract multilayers.

4.      Microwave assisted oxidation

By using microwave energy, we can produce graphene in just one step and this process occurred in 2012. Because of this method the use of potassium permanganate is excluded. Just what have to do is to control the microwave time to synthesized the graphene with micro wave radiation assistant.

Chemical vapor deposition

1.      Epitaxy

In this process, silicon slices coated with germanium are keep in to the dilute hydrofluoric acid which create hydrogen terminated germanium with the coat of graphene on it by CVD.

2.      Cold wall

With help of cold wall CVD, the rate of production of graphene gets increased by 100 times than the conventional CVD method as well as cost gets reduced by 99%. The produced material has the enhanced electronic qualities.

 

Carbon dioxide reduction

In this process the magnesium combusts because of the exothermic reaction. Because of that in oxidation or reduction reaction, the nanoparticles of carbon get produced. On that carbon nanoparticles we get the graphene.

PROPERTIES OF GRAPHENE

1.      Physical properties

Graphene is the thinnest material with 0.34 nm thickness and toughest 2D material ever. It is much harder than the steel and the diamond having same dimensions. It has the tensile strength 130 GPa with stiffness more than 1 TPa. 0.3 inches of graphite contains 3 million graphene layers. It is incredible stretchy and flexible, so that it can gets stretch up to 25% of its original length. Graphene is two-dimensional material even then it is visible without any microscope. One more interesting property is that it gets expand when it gets cooled and shrinks when it gets warm. There is not a single material of the same quality. Its density is 0.763 mg per m² .

 

2.      Electronic properties

As graphene is a zero-gap material it has extremely high electrical current density, because conduction and the valence bands meet at the Dirac points. The resistance offered by graphene is less than other material. Also, it is able to convert into the superconductor which carry 100% electricity. There no bandgap, hence it is used for transistor production.  Its intrinsic mobility is 100 times better than silicon thus electrons have no resistance when they move through graphene.

 

3.      Thermal conductivity

Graphene is the best thermal conductor which has the highest thermal conductivity as compared to other materials. It is greater than carbon nanotubes and diamond. As well as graphene is able to conduct heat in all direction and that’s why it is isotropic conductor.

4.      Optical properties

One remarkable property is that graphene absorbs extreme amount of light near about 2.3% of white light and because of that a single layer also we can see with naked eyes. By this property I can be used as solar cells and transparent conductors.  The optical response of graphene nanoribbons is tuneable into the terahertz regime by an applied magnetic field.

5.      Chemical properties

Graphene is inert material as it does not react with other substances even its all atoms are exposed to environment. It absorbs different atoms and molecules still doesn’t react with them. This property makes is special and can lead in the future. Also, it’s the material whose both sides all atoms available for reaction purpose. That’s why it has special chemical reactivity and the highest ratio of edge atoms of any allotrope. Its boiling point is 4200^oC.

Forms and Application of Graphene (See in Part 2) 

https://vitech21.blogspot.com/2021/08/graphene-future-of-engineering-part-2.html  

Home Assignment Activity By - 

SYDA _B_ Batch - 2_Group - 2

51 - Ahire Mrunal Keshav

52 - Mathpati Vaishnavi Vikas

53 - Sonawane Pushkar Mukesh

54 - Jagtap Sanket Rajendra

55 - Chavan Sanskruti Suresh

Guided By : 

Prof. N. S. Kulkarni

Prof. S. V. Patil