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Graphene presentation 2015

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Page 1: Graphene presentation 2015
Page 2: Graphene presentation 2015

GRAPHENE

Graphene is an allotrope of carbon in the form of a two-dimensional, atomic-scale, hexagonal lattice in which one atom forms each vertex.

It is the basic structural element of other allotropes, including graphite, charcoal, carbon nanotubes and fullerenes.

It can also be considered as an indefinitely large aromatic molecule, the limiting case of the family of flat polycyclic aromatic

hydrocarbons.

Page 3: Graphene presentation 2015

Andre Geim and Konstantin Novoselov at the University of

Manchester won the Nobel Prize in Physics in 2010 "for groundbreaking

experiments regarding the two-dimensional material graphene.

The global market for graphene is reported to have reached $9 million

by 2014 with most sales in the semiconductor, electronics, battery energy and composites industries.

Page 4: Graphene presentation 2015

STRUCTURE….

Graphene is a crystalline allotrope of carbon with 2-dimensional properties. Its carbon atoms are densely packed in a regular atomic-scale chicken wire (hexagonal) pattern.

Each atom has four bonds, one σ bond with each of its three neighbors and one π-bond that is oriented out of plane. The atoms are about 1.42 Å apart.

Graphene's stability is due to its tightly packed carbon atoms and an sp2 orbital hybridization – a combination of orbitals px and py that constitute the σ-bond.

The atomic structure of isolated, single-layer graphene was studied by transmission electron microscopy (TEM) on sheets of graphene suspended between bars of a metallic grid.[

Page 5: Graphene presentation 2015

ELECTRONIC SPECTRUM..

• Graphene is a zero-gap semiconductor, because its conduction and valence bands meet at the Dirac points.

• Electrons propagating through graphene's honeycomb lattice effectively lose their mass, producing quasi-particles that are described by a 2D analogue of the Dirac equation

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THE STORY OF GRAPHENE..

• If you've ever drawn with a pencil, you've probably made graphene.

The world's thinnest material is set to revolutionize almost every part

of everyday life.

• Although scientists knew one atom thick, two-dimensional crystal

graphene existed, no-one had worked out how to extract it from

graphite. That was until it was isolated in 2004 by two Russian-born

researchers at The University of Manchester, Andre Geim and

Konstantin Novoselov.

Page 8: Graphene presentation 2015

THE EARLY YEARS….

• Graphene, millions of ultra-thin layers that stack together to form

graphite commonly found in pencils, was first studied as long ago as

1947.

• That electric current would be carried by effectively massless charge

carriers in graphene was pointed out theoretically in 1984, and the

name 'graphene' was first mentioned in 1987.

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DISCOVERY AND EXTRACTION OF GRAPHENE FROM GRAPHITE

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HOME OF GRAPHENE…

Andre and Konstantin adopted a method that researchers in surface science were using – using simple Sellotape to peel away layers of graphite to expose a clean surface for study under the microscope. Once used, the tape was simply being thrown away. Yet no-one had noticed the material on the tape was thinner than the material produced by polishing. They had made graphene, yet had not realised it.

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FROM NANOMATERIAL TO GLOBAL

EXPLOSION

• Konstantin continued to explore how thin the graphite flakes on the tape

could be made. He peeled the layers so thinly that what was left was one-

atom thick graphene.

• Groups around the world sent students and postdocs to The University of

Manchester to learn how to make the material and much work was done to

explore the unusual electronic properties of graphene.

• Andre and Konstantin continued to publish academic papers describing how

it could potentially be used in a huge number of diverse applications.

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TYPES OF GRAPHENE….

Few-layer graphene (FLG) or multi-layer graphene (MLG) – a 2D,sheet-like material, either as a free-standing flake or substrate-bound coating, consisting of a small number (between two and about 10) of well-defined, countable, stacked graphene layers of extended lateral dimension.

Graphene oxide (GO) – chemically modified graphene prepared by oxidation and exfoliation. Graphene oxide is a monolayer material with a high oxygen content.

Reduced graphene oxide (rGO) – graphene oxide (as above) that has been reductively processed by chemical, thermal, microwave, photo-chemical, photo-thermal or microbial/bacterial methods to reduce its oxygen content.

Graphite oxide – this precursor to GO is a bulk solid made by oxidation of graphite through processes that functionalize the basal planes and increase the interlayer spacing.

Page 13: Graphene presentation 2015

THE MANUFACTURING PROCESS..

1. Chemical Vapour Deposition,

where a gas containing carbon (such as Methane) is broken down and reassembled on a hot metallic surface into a sheet of graphene.2. Solution Exfoliation, where graphite is blasted into small fragments of graphene using ultrasonic energy.

Page 14: Graphene presentation 2015

Graphene batteries and supercapacitors to

power our world

• The potential of graphene for batteries becomes more apparent each day,

with headlines touting new graphene electrodes and battery materials.

• Adding some boron atoms to the graphene structure result in an ultrathin

efficient flexible anode for lithium ion batteries & helps the lithium ions of

the battery stick better to the graphene anode, which was a problem earlier.

• Graphene anodes result in faster battery charging and discharging compared

to conventional anodes.

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Already some years ago, engineers

at Northwestern University have shown that graphene anodes

hold energy better than graphite anodes, with 10x faster charging.

Finally, graphene is not only being used for the electrodes of batteries, but for the active

material itself. Graphene makes such a good battery

material that the devices are called "supercapacitors", i.e.

batteries which hold enormous power and charge

within a few seconds.

UCLA researchers caused shock waves when they

showed a graphene mixture that can be coated onto the

surface of a regular DVD. An ordinary DVD burner is then used to inscribe millions of supercapacitor circuits into

the graphene layer. The layer can later be simply peeled off

and transferred anywhere where a super powered

battery is desired.

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• A new battery under development promises to store twice as much and power an electric vehicle for more than 300 miles .

• Battery that can store more than twice the Wh/kg of a Li ion battery, and has already shown that it can do 1,500 charge cycles without deterioration – probably more.

Lithium sulphur graphene - a battery breakthrough?

Page 17: Graphene presentation 2015

APPLICATION OF GRAPHENE..

• Medicine: Graphene could pave the way for a step change in the

treatment of cancer and conditions such as Parkinson's.

• Water purification and treatment in developing countries, and even provide

more efficient desalination plants.

• In aircraft technology and cars.

• Graphene detects: It could create sensors that can detect even minute

traces of gases or dangerous chemicals

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